SYSTPMS A.NALYSIS OF U.S. I-I/u^AGEMENT STRATEGIES IN TKE GULF OF MEXICO SHRIl-iP INDUSTRY By PAUL JEROME HOOKER A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILU-IENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1972 UNIVERSITY OF FLORIDA 3 1262 08552 4485 Copyright by Paul Jerome Hooker 1972 FOR KERRY ACKITOVTLEDGMEIH'G My debt of gra^.itud£ for assistance during my graduate career exceeds my ability to provide acltnowledgment . I tru.tit that my many unrecognised benefactors will forgive vie fc-i ciLiug ori].y a fe\': of the debts that I perceive to be the greatest. The greatest debt should be acknov;ledged first. Mine is duo ray wife, Martha, for her moral support during my graduate career and uiy young daughter, Kerry, for making that career vrorthwhile, Leo Polopolus has served as Chairman of my Supervisory Conmittee, academic and professional advisor, and friend. Max II. Lar.gham has pro- vided good advice during my graduate career and liis thorough reviews of my dissertation research materials have been invaluable. W. W. McPherscn has provided a X'/ellspring of experience from v/hich I have freely drawn as a student and as author of this dissertation. C . C. Osteibind brought the expertise of an economist with experience in the Gulf of Mexico shrimp industry to bear in his revicvj of the dissertation manu- script. For these contributions, as well as many left unmenticned, I wish to thank the members of my Supervisory Comnuttee. I wish to thank K. R. Tefertiller, Chairman of the Department of Food and Resource Economics of the University of Florida, for providing financial assistance during the course of research on this project. In addition, I wish to acknowledge departmental support of the project which allowed use of the facilities of the University of Florida Computing Center. iv Mrs. Cindy Bass, with the picLovinl aid oi= Mrs. Pntti Fesmlre, has accomplished the transrorm^tion of: this dissertation from a longhand manuscript into its present form. For this feat she has earned my gratitude and admiration of her considGrable ability. TABLE OF CONTENTS Page ACKNOWLEDGl-IENTS iv LIST OF TABLES viii LIST OF FIGURES . . . .' x ABSTRACT xi CHAPTER I INTRODUCTION 1 CHAPTER II BIOECONOMIC THEORY 3 Fish Population Theory 3 A Theory of Open Access and Common Property Resource Exploitation 17 Bioeconomic Theory of a Fishery 33 CHAPTER III GULF OF MEXICO SHRIMP INDUSTRY: DESCRIPTION AND MODEL ... 38 Description of the Industry 38 The Gulf Shrimp Resource 38 The Gulf Shrimp Fleet 46 Processing and Marketing the Gulf Shrimp Catch . . 56 A Model of the Gulf Shrimp Industry 58 A Model of the Gulf Shrimp Resource 59 A Model of the Gulf Shrimp Fleet 62 A Model of the Marketing and Demand Sector of the Gulf Shrimp Industry 69 CHAPTER IV METHODOLOGY AND DATA 73 Simulation as a Tool for Model Building and Policy Evaluation 74 Data 84 The Computer Program 95 vi TABLE OF C01;TEvyi'S--Con!:irnied r?.ge CllArTKR V RESULTS OBTAINED WITH THE SIi-lLlLATIOi>I MODEL Ai'i) POLICY IMPLICATIONS '^'' Model Validation -^^ Simulated P.csults for the Policies Con:;.ldf:rv-f] 11''; Policy Implications -'-^^ CHAPTER VI RECAPITULATION OF THE PPESENT STUDY WITH SUGGESTIONS FOR Iffl'ROVEMENTS /Mv'D FURTHER WOPvK 130 APPENDIX I APPENDIX II LIST OF REFERENCES . ADDITIONAL REFERENCES BIOGRAPHICAL SKETCH . 15! Recapitulation of Objectives and Evaluation of Achievements • • Improvements Needed in the Present Model snd Suggest ionb for Further Work ^^^ 134 1^)8 180 183 185 vli LIST UF TABLES Table Page 3.1. Landings of Gulf slirimp by area and specicF! for the years 1967, 1968, and 1969 *. 41 3.2. Percentage distribution of Gulf shritnp landings by area and species for the years 1967, 1968, and 1969 ... 43 3.3. Average landings and percentage distribution of average landings of Gulf shrirap by area and species over the years 1967, 1968, and 1969 44 3.4. Summary of shrimp otter trawl boats, vessels, fishermen, and gear in the Gulf states, 1966 47 3.5. Summary of shrimp otter travel vessels of the Gulf states, by tonnage groups, 1966 51 3.6. Marine economics data - 65 foot Gulf of Mexico shrimp vessels 53 4.1. Age (in months of 4.33 weeks each) distribution by size and sex of brown, pink, and white shrimp in the Gulf of Mexico 86 4.2. Coefficients to convert 24-hour days fished to fishing mortality and estimated square nautical miles fished by area 87 4.3. Vessel size classes and sweep capacity of nets along headrope in hundreds of feet 89 4.4. Mean 24-hour days fished per month by a vessel in each size class 90 4.5. Factors to adjust days fished by a vessel in a size class to reflect variations in average days fished by vessels in different areas 91 4.6. Number of vessels in each size class estimated to have home ports in each area and number of vessels in each size class assumed to be fishing in each area in December of a typical year 93 4.7. Reduced form coefficients for quarterly shrimp model, 1956-1967 94 viix LIST OF TABLES— Contiriued Table Page 5.1. Adjusted coefficients to convert 24--hour days fished to fishing mortality and factor? (APFACJ's) by which initial estimates of the mean number of shrimp recruits were multiplied for final use in the model 99 5.2. Size composition of actual shrimp catches in the Gulf and South Atlantic states for the years 196A-1970 and average size composition of thirty years catch data generated by the computer model 101 5.3. Simple correlation coefficients between selected vari- ables based on values generated by the computer model 3 06 5.4. Comparison of percentage distribution of effort by area in each month of the year of sample vessels with the percentage allocation generated by the computer model in the 30th year for vessels (vessel size classes 2-5) 109 5.5. Comparison of percentage distribution of effort among aggregated areas in eacli month of samiple vessels with the allocation geiierated by the model 110 5.6. Annual fixed cost charges per vessel employed by the computer model and the capitalized values that these sums represent 113 5.7. Value of the fleet under different assumptions about average life of vessel and gear and using values given in [1] 115 5.8. Average annual returns from the Gulf shrimp catch, costs to the industry and fixed investment in the industry assuming a five year investment life under various settings of the policy variables 118 5.9. Rate of return to fixed investment in the Gulf shrimp fleet under various settings of the policy variables 119 5.10. Changes in average annual returns, costs, and investment occasioned by the imposition of controls 120 5.11. Average annual total production costs incurred by the Gulf of Mexico shrimp fleet per pound of shrimp produced and average annual wholesale price of shrimp produced and average annual wholesale price under alternative policies 124 ix LIST or FIGURES i Page Curves Describing the Population DyaainicG of a Single Year-Class Within a Fishery -• Major Shrimp Fishing Areas in the Gulf of Mexico .... AO Shrimp Vessel with Otter Traul Nets Deployed . 49 Shrimp Processing and Marketing Channels 57 Schematic Representation of a Framework for Validation of Simulation Models ""^ 4.2. Flow Diagram of the Computer Model of the Gu!! f of Mexico Shrimp Industry ■ ^6 5.1. Annual Values Generated by the Computer Model for Wholesale and Ex-vessel Prices, Total Landings, Imports, and Effort in Adjusted Days Fislied 104 5.2. Annual Values Generated by the Computer Model for Total Production Costs, Adjusted Days Fished, Value of the Fleet Assuming a Fixed Year Investment Life and Net Return Figure 2.1. 3.1. 3.2. 3.3. 4.1. 5.3. Simple Correlation Coefficients Between Selected Variables Based on Values Generated by tha Computer Model 105 108 Abstract of Dissertation Presented to th? Grfjdu;,>te Council of the University of Florida in Partial fulf i.llr.cnt of the Raquireincnts for the Degree of Doctor of Philosophy SYSTEMS /J\ALYSIS OF U.S. MAIvlAGEi-IENT STRATEGIES IN THE GULF OF MEXICO RHRBIP IOTjUSTRY By Paul Jerome Hooker March, 1972 Chairman: Leo Polopolus Major Department: Food and Resource Economics The shrimp resource is an open access resource. Except for r.itua-- tions attributable to territorial waters, the shrimp resource is open to exploitation by anyone possessing the physical capability to exploit it. A priori theoretical reasoning suggests that the economic return attributable to the shrimp resource as a productive input will be dis- sipated so long as it retains an open access status. A problem of immediate practical importance is to determine the extent of dissipa- tion of the returns to the shrimp resource in its open access status and the relative efficiency of different institutional schemes in capturing this return. The first objective of this study was to determine the responses of individual fishing firms in the Gulf of Mexico shrimp industry and the resultant aggregate effect for the industry to changes in the shrimp population in the Gulf of Mexico, technological conditions of harvesting xl and processing, and demand coiiditj.ons . A second ob3Cc!.i\e was to deteriiiine whether a] tP) native nanageraent strcitegies exist which will improve industry effiiciency in a social sense, reducing overinve.stiv.ent and/or the extent of non-optimal husbandry practices that occur as a result of the free use of a;i open access resource. A theory of the basic resource was developed to describe tlie behav- ior of a particular year-c]ass in a fishery ovor time in teims of growth in Vi'eight, recruitment patterns, and natural and fishing mortality rates. An economic theory of exploitation of an open r.ccess resource was developed and the divergency between behavior that is optimal for the industry as a whole and the behavior resulting from uncoordinated individual actions was derived. The basic resource and economic theo- ries were then synthesized into a bioeconomic theory cf an exploited fishery and the on-vessel entry and fish landings charges needed to manage the fishery in an efficient m^anner were specified as theoretical aggregates. An abstract model of the Gulf shrimp industrj' V7as constructed based on the developed theory. The industry model took the form of three sub-models, one each for the basic resource, harvesting, and demand sectors. The interface between the basic resource and harvesting sector models was composed of the availability of shrimp by size and area and the amount of effort applied by the shrimp fleet to capturing the basic resource. The interface between the harvesting and demand sector models encompassed the catch produced by the fleet and the ex-vessel price paid for this catch by the demand sector. The model provided policy vari- ables in the age (size) at which shrimp first become subject to capture, the barriers to vessel entry into the fleet as expressed in annual Xll license fees, and per pound taxes ciiarged the fleet members on the shrimp landed as expressed in reduced ex-vessel prices. The first objective was satisfied and the abstract model trans- formed into ^n cinpirir.al model by drawing, en published research results as well as estimating model parameters from primary secondary' data. The empirical model of the Gulf shrimp industry was developed as a simulation model and a computer program was developed to generate model behavior over time. Information generated by the simulation model on selected indicators of industry performance was used to satisfy the second objective by establishing tentative conclusions, subject to the limitations of the model, as to the relative effectiveness of the poli- cies considered in attaining alternative objectives. xiii CHAPTER I INTRODUCTION niere are both academic and practical reasons for this particiilar studj'. Tlic shrimp resource is an open access resource. E>;cc'pL for situations attributable to territorial waters, the shrimp resource is open to exploitation by anyone possessing the physical capabllit}/ to exploit it. The problems involved in creating instjtutions for effec- tive public or private ownership of open access resources and in determining the relative efficiency of exploitation of the resource under various institutional forms are particularly intriguing from the academic point of view. These problems are not without practical importance. For example, the annual value of the Gulf shrimp resource at point of first sale has been in the neighborhood of $100 millioii in recent years. A priori theoretical reasoning suggests that all the return attributable to the shrimp resource as a productive input will be dissipated so long as it retains an open access status. Thus, a problem of immediate practical importance is to determine the extent of the potential return available from the resource and the relative efficiency of different institutional schemes in capturing this return. The objectives of this study are to: 1. Determine the responses of individual fishing firms in the Gulf of Mexico shrimp industry and the resultant aggregate effect for the industry to changes in: 1 2 a. The shrimp population In the Gulf of Mer.ico; b. Technologic;il coijditlcias of harvesting and processing; and c. Demand condiiions. 2. Determine whether alternative management strategies exist whicli will improve industry efficiency in a social sense, reducing overinvestment and/or the extent of non-optimal huirbandry prac- tices that occur as a result of the free use of an open access resource. The plan of attack for fulfilling the above objectives Is briefly as follows. Chapter II presents some theoretical considerations with respect to open access resources, especially fishery resources. (The term "fishery resources," as used here, includes the crustaceans.) These considerations involve economic, as well as biological, theories of the fishery resources. Chapter III presents a description and abstract model of the Gulf shrimp resource involving both economic and biological considerations — thus, it is a bioeconomic m.odel. Chapter IV discusses the methodology used and data limitations. Chapter V contains the results of the application of the model to the available data, simulated results from operating the system under alternative management strategies, and a discussion of policy implications. Chapter VI, the concluding chapter, is devoted to a review of the study and a critical evaluation of the analysis with suggestions for improvement and further research. CHAPTER II BIOECONOMIC THEORY A fishery is a prime example of a system involving man as an ecc- nomically viable predator on a natural population. To adequately describe such a system, biological theory describing the behavior of the natural population must be meshed with economic theory describing the behavior of man as the predator. The result of this synthesis may best be called "biocconomic theory." The biological stock enters into the economic model as an input. Consequently, when dealing with bioeco- nomic theory, biological theory is appropriately treated first. After a discussion of fishery population theory, the economic theory of exploitation of open access resources is presented. The chapter con- cludes with a combination of the two theories into a bioeconomic theory of a fishery. Fish Population Theory This section draws heavily on som.e recent work in fish population analysis by J. A. Gulland [20], although generalized functional forms are used in place of Gulland 's specific functional notation. Considering a closed stock subject to exploitation, the factors (rates) determining changes in the stock over time are [see also 20, p. 3]: 1. Recruitment or the rate at which young fish reach a size and/or age at which they are considered to become part of the stock 3 subject to exploitation; e.g., larv:'! shrimp and pelagic flounder are not considered ))art of the conmercially exploited stocks of shrimp and flounder. If tliere is no clear-cut natural recruitment size, then the recruitment size may be arbitrarily set. 2. Growth of individuals or the time rate of gain in length and/or weight or some other measure of growth. 3. Deaths due to fishing or the catch rate; these V7ill be roughly correlated with landings and will be ascertained by "fishing effort" which is determined outside the biological frame^TOrk of the fishery. 4. Deaths due to other causes or the natural mortality rate. Figure 2.1, corresponding roughly to Gulland's Figure 1.1 [20, p. A], depicts the behavior over time of the length, weight, and number of individuals in a particular year-class (the progeny of the stock in a given year) and the behavior over time of the total weight of the year-class. The ordinate of Figure 2.1 is assumed to be arranged in units appropriate to the particular curve of interest. The abscissa measures time. The reproductive process is assumed to be essentially complete at t ; t is the time at which the individuals are recruited to the o r stock while t is the point in time at which they become subject to mortality from fishing. Beyond t , the solid portion of the line repre- senting number of individuals is drawn under the assumption of zero fishing mortality, while the dashed portion represents numbers of indi- viduals when the year-class is subjected to some constant level of fishing mortality. VJeight , Length, or Number W maxiraum or L maximum 1 ^^ individual length individual veit^ht f;otal vcight of year-class number of individuals -Bl Time Figure 2.1. Curves Describing the Population Dynamics of a Single Year-Class Within a Fishery 6 The total weight curve is calculated under the assumption of an uncxploited stock. The total weight of t.ie year-class in the absence of fishing is assumed to increase, at first at an increasing rate until time t , and thcr at a decreasing rate until some maximum weight is reached at time t • Then total weight declines, more and more rapidly at first but eventually at an algebraically increasing rate, until the year-class is eliminated from the stock. Individual fish are assumed to grow in length throughout their lives at a decreasing rate. Indi- vidual fish gain in weight throughout their lives at an increasing rate during the first part and at a decreasing rate during the latter part of their lives. The number of individuals in a year-class decreases over time, slowly approaching and finally reaching zero, implying that the natural mortality rate is positive and decreases over time; i.e., the rate of survival is negative but increasing algebraically at any point in time. The individual weight and number factors combine to produce the aggregate weight behavior described above. The recruitment and fishing mortality factors do not lend them- selves to straightf on^/ard description so vjell as the otlier factors. If the population has a well-defined and short spavrning season and homoge- neous development of young so that all members of each year-class are essentially the same size, then the recruitment function will take the form of a series of points, zero at all times other than the instant of time in which year-classes enter the exploitable stock, at which time the function takes on the value of the size of the year-class in ques- tion. However, if, as is more likely, the spawning period occupies a more or less significant portion of the year and subsequent development is not homogeneous, then recruitment will not occur at an instant of time. Rather, it will be spread over an interval of time during which 7 the proportion of the year-class being recruited into the stocV increases at first at an increasing and later at a decreasing rate. Given that the juveniles are in the sairie area as is the exploited stock, the time pattern of recruitment is of interest wi*"h respect to determining opti- mal time patterns of fishing and gear selectivities. An alternative situation is one in vhich juveniles are segregated from the exploited stock by location and recruitment occurs by migration. In this situa- tion, the proportions of the year-class of different length (size) being recruited are of interest. Until a mean recruitment length is reached, the proportion of the year-class entering the exploited stock increases at an increasing rate while it increases at a decreasing rate beyond this mean length. To place the appropriate emphasis on the recruitment rate and to relate it to an aspect of fishing effort — gear selection — the following quote from Gulland is helpful: Recruitment is, by its nature, much less easy to express in quantitative terms than mesh selection. As the main interest is in the combined effect of recruitment and selection — i.e., the pattern of entry into the catch — the recruitment pattern is very important when it is above, or overlaps, the range of gear selection, but not when it is complete before gear selection starts. If, therefore, all fish have been recruited at a size below the selection range of any likely mesh size, then the precise pattern of recruitment may be ignored, and it can be taken arbitrar- ily as occurring at some convenient length or age below the selection range ... [20, p. 86]. The importance of the recruitment rate seems to lie in its relationship to gear selectivity. The interaction of these two factors produce the commercially important result: the rate of entry of juveniles into the catch. Gear appears to fall into three general groups: completely non- selective gear; e.g., a fine-mesh purse seine; gear that is non-selective above some size of fish; e.g., certain trawls; and gear that is selective 8 over a certain range of fish sii,e, allov;ing those smaller and larger to escape; e.g., gill-nets. There is little to say about the completely non-selective gear except to point out that if legal size restrictions on landings are placed on a fishery (thus arbitrarily defining the size at which juveniles are recruited into the exploited stock) and juveniles are subjected to the non-selective gear, then a certain portion of the catch will be discarded at sea. If part or all of this discarded catch dies, the various year-classes will be reduced by the extra mortality not reflected in landings. Thus, the stock will be reduced beyond what would be expected from measured fishing mortality (landings). The implication is that in order to properly assess the population, measured fishing mortality (landings) must be adjusted to allow for the mortality experienced by the juveniles. Gear that is selective to the extent that escapement of individuals below some size is allox'/ed is of particular interest in this study. Shrimp trawls allow small individuals to pass through the netting while larger individuals are retained. The selectivity is not perfect, however, and over some size range, the proportion of individuals retained increases with size and varies from zero to one. It seems reasonable to assume that the proportion of individuals retained (recruited into the catch) increases at first at an increasing and then at a decreasing rate over the relevant size range, producing a sigmoid curve in a plot of fraction retained against size. If a size limitation is placed on landings at a size falling within this selection range and if all or part of the resultant discarded catch dies, the yield curves estimated from recorded landings data will underestimate the potential yield by not taking into account the fishing mortality experienced by the juveniles. In this situation restrictions on gear selectivity, if 9 feasible, restrictions on time of fishing, if the recruitment pattern is time-oriented, and/or restrictions on location of fishing, if recruitment is by migration, may present superior alternatives from the standpoint of maximizing yield for a given amornt of effort Jn that simultaneously the year-classes being recruited are strengthened and a larger proportion of the catch handled is actually landed. Gear that is selective over a certain si?.e range is probably t)ie most effective as far as selection is concerned. Gill-net selectivity typifies this type of gear, having a selectivity curve (plot of propor- tion retained on size) that is normal in shape. Size limitations are, apparently, seldom used in conjunction with restrictions on mesh size as gill-net selectivity curves appear to be sufficiently sharp so as to cause size of fish retained and mesh size to be closely related. It is apparently easier to regulate mesh size than to enforce minim.um size limits on fish in the catch, thus the former course of action is taken. This action usually serves to eliminate the problems involved in estimating "true" selectivity or yield curves when legally defined recruitment sizes and gear selectivity ranges overlap. Gear that is selective only below some certain size (so that proportion of fish retained varies from zero to one over the selection range) is the gear considered below. Deaths due to fishing are determined in large part by the amount of fishing effort expended and are thus determined by forces exogenous to the biological system. However, a constant level of fishing effort per unit area and per unit time produces mortality behavior similar to natural mortality. A constant fishing mortality coefficient (defined as an increasing linear function of a measure of fishing effort such as 10 number o£ trav;l tov/s per unit area per unit tiii.u) implies that tlie number of fish surviving over time from a given recruited year-class decreases but 3t an algebraically increasing rate. The above discussion of factors affecting a particular year-class of a fisli stock, and the stock itself by extension to all year-classes making up the stock, is conveniently summarized by presenting the theory in generalized notational form. The expressions that follow represent a modification and extension of CuJ.land's derivation of a simple yield curve for a single year-class [2.0, section 9]. The variables of interest are: N = number of fish surviving at age (t - t ) during a unit time interval t. N = number of fish considered to be recruited during t, either by migrating to a different area or by reaching a particular size. N = number of fish retained by gear during t. C = number of fish caught during t. Y = the weight of the catch, C , during t. L = average length at age (t - t ) . W = average v/eight at age (t - t ) . B = biomass (total weight of year-class) at age (t - t^) . M = instantaneous natural mortality coefficient. F = instantaneous fishing mortality coefficient defined to be a linear function of fishing effort per unit area per unit time. The time index, t, ranges from time of completion of reproductive process, t , to infinite time, t^ and thus, (t - t^) is the age of an average member of the year-class. Two ages of interest are (t^ - t^) , 11 the mean recruitment age of the year-clasR at vjhlch all individuals may be assumed recruited, and (t -• t ), tlie mean age at which the year- class becomes subject to fishing mortality. These ages may be the same in time-varying recruitment or, especially in location- varying recruit- ment, they may be different. In any event, they are defined to represent the ages in the interva.ls during which recruitment and selectivity occur at which one half of the year-class is considered recruited and/or is retained by gear when contacted. It is oftentimes convenient to assume that the full year-class is recruited or becomes subject to fishing mortality at the relevant mean age. The theoretical relationships with directions of change are: 1. Number of fish and total mortality rate v^7ith direction of change: (2.1) N = N(M, F, t - t ) t (2.2) dN /dt = N (N^) < 0 (2.3) d^Nj./dt^ = N (Nj.) > 0 (2.2) and (2.3) also hold when F = 0 or M = 0. 2. Length (2.4) L^ = L(t) (2.5) dL^/dt > 0 (2.6) d^Lj./dt^ < 0 3. Weight (2.7) W^ = W(t) (2.8) dW^/dt > 0 (2.9) d\^/dt^ > 0 12 (2.9a) d^v/j./dr.^ < 0 , ' ^ ^r where t is such that d W /dt . =0. w t. t - t^ 4. Bioraass (2.10) B^ = N^W^ (2.11) dB^/dt = W^ dN^/dt + N^ dW^/dt (2.11a) dB^/dt > 0 , t < tg (2.11b) dB^/dt < 0 , t > tg (2.11c) dB^/dL =0 , t = tg dW dN 2 2 (2.12) d^B^/dt^ = W^ d\^^/dt^ + 2 J~ dT" "^ ^\ "^ "t'''^^ (2.12a) d^B^^/dt^ > 0 , t < tj^^ , t > t^2 (2.12b) d^B^/dt^ < 0 , tg^ < t < tg^ (2.12c) d^B^/dt^ = 0 , t = tg^ , ^^ = '^B2 Conditions (2.11a), (2.11b), and (2.11c) describe the relative offsetting effects of decreases in biomass due to reduction in numbers of indivi- duals versus increases in biomass due to increase in individual weight. Equation (2.12) expresses the variation in rate of change in biomass in terms of rates of change and direction of rates of change of numbers of individuals and individual weight. Conditions (2.12a), (2.12b), and (2.12c) state the direction of rate of change over different periods of time and are consistent with (2.2), (2.3), (2.8), (2.9), and (2.9a). * 5. Recruitment with proportion of year-class recruited (R^ = Nj./N^) expressed as a function of age, (2.13), and length, (2.16). 13 (2.13) R^ = n' (M, F, t. - l:^)/N(K, F, t - t^^ * * t^ < t < t^ (2.13a) R,^ = 0 , t 5 tj^ (2.13b) P^ ^ -^ ' ^ - *^3 (2.1A) dR /dt > 0 , t < t < t (2.15) d^R /dt^ > 0 , t^ < t < t2 (2.15a) d^R^/dt^ < 0 , t^ < t < t^ (2.15b) d^R /dt^ =0 , '^ " ^2 In equations (2.16) - (2.18), L must bs considered a length measure, not an average, and N (L ) is the number of fish of length less than L that are considered to be recruited. (2.16) R^ = N*(L^)/N(M, F, t - t^) , L^.^ < ^^ < Lp^ (2.16a) Rj. = 0 , L^ < L^^ (2.16b) R^ = 1 , L^ > Lj,3 (2.17) dR^/dL^ > 0 , L^i < L^ < L^3 (2.18) d^R^/dL^^ ^ Q ^ ^^^^ ^ ^^ ^ ^^^^ (2.18a) d^R^/dL^^ < 0 , ^^2 '^ ^t ^ ^R3 (2.18b) d^R^/dLj_^ = 0 , L^ = Lr2 6. Selectivity (travel-type) with proportion of fish retained by + gear (S = N /N ) expressed as a function of length (a measure of size proportional to the positive square root of surface area and to the cube root of volume or weight). In equations 14 (2.19) - (2.21), as in (2.16) - (2.18), L^ liUould be inter- preted as a measure of length, not an average related to the population. (2.19) S^. -- 4(L^)/N(M, F, t - t^) , Lg^ < L^ (2.19a) Sj. - 0 , L^ < Lg^ (2.19b) S^ = 1 , Lj. > Lg3 (2.20) dS^/dLj. > 0 , I^si '^ -^t ^ ■^SS (2.21) d2Sj./dL^^ > 0 , Lgi < Lt '^ ^S2 (2.21a) d^S^/dL^_^ < 0 , Lg2 < L^ ^ -"^SS (2.21b) d^S^/dLj.^ = 0 , L^ = Lg2 7. Catch in numbers of fish (2.22) C^ = C(F, N^) (2.23) 9C^/8F > 0 (2.24) 8^Cj./3F^ > 0 , 0 < F < F^ (2.24a) a^C^/3F^ < 0 , F^ < F < ~ (2.25) 9C^/3N^ > 0 (2.26) 3^C^./3N^^ > 0 , 0 < N^ < N^ (2.26a) 3^C^/3N^^ < 0 , N^ < N^ < «> (2.27) 3^C^/3F3Nj. > 0 (2.28) dC = ^ dF + ^ dN ^ 3F SN^ < Lr,^ s:j 15 ') 2 (2.29) d C - ^t dF + 2 _ t_ d.-^dN + D^_C_ dN " t Conditions (2.23), (2. 24). and (2.24a) state that the Earginal return to effort, assuiiiing numbers of fish constant, is everywhere positive but declines after some level of effort is reached. Conditions (2.25), (2.26), and (2.26a) describe a different type of marginal behavior, namely that as numbers increase, assuming effort constant, catch increases but at a decreasing rate beyond some population level. Condition (2.27) states that as numbers increase, the return to marginal units of effort increases or, conversely, as effort increases, the marginal increment due to increasing numbers increases. Equation (2.28), expressing the total change in catch for changes in effort and numbers, is especially interesting when divided through by the incremental change in fishing mortality, dF, a proxy for effort. Recalling that number of fish is a declining function of fishing mortality, it becomes apparent that the change in catch due to a change in effort is not readily pre- dictable as to sign or direction of change — given by equation (2.2y) — when allowance is made for the negative effect of increasing effort on fish numbers. 8. Weight of catch (2.30) Y^ = Y(F, N^, W^) or (2.30a) Y^ = Y(F, B^) (2.31) 8Y^/3F > 0 (2.32) 3^Y /3F^ > 0 , 0 < F < F^ (2.32a) 3^Y^/3F^ < 0 , F^ < F < CO (2.33) ?A'^/9Nj. > 0 (2.3M 9^Y^/3N^^ > 0 , 0 < N^ < N^ (2.34a) 9^Y /3N ^ < C , N^ < N^ < «> (2.35) 8Y /3w > 0 (2.36) 3^Y^/3W^^ > 0 , 0 < W^ < VJ^ (2.36a) 3^Y /3VJ "*' < 0 , W^ < W^ < ^ (2.37) 3^Y /3F3N > 0 (2.38) d^'-Y /3F3W > 0 (2.39) 3^Y /3N 3W > 0 3Y 3Y 3Y (2.40) dY^ = -3^ dF + 3^ dN^ + 3^ dW^ 2 ^'^ 2 ^^\ 2 ^\ 2 ^^\ dF oN oW t 3^Y 3^Y + 2 ^^^f, dFdW^ + 2 ^-. ^f. dN^ dW^ 3F3W t 3N 3W t t Equations and conditions (2.30) - (2.39) describe the weight of the catch and the partial effects of changes in effort, numbers of fish, and average weight of fish. Equations (2.40) and (2.41) describe the total effect on weight of catch of simultaneous changes in effort, numbers, and individual weight and are most interesting when divided through by the incremental change in effort. As is the case in (2.28), the change in weight of catch due to a change in effort is not predict- able a priori when the decreasing effect on numbers of increases in 17 eitort; is taken into account, A consideration of (2.41) indicates that the direction of rate of change in v/eight of catch due to changes in fishing mortality is as unpredictable as the rate of change itself. Equations and conditions (2.22) - (2.41), especially those dealing v;ith changes in fishing mortality, represent that part of fish popula- tion theory that may provide a liiik witli an econouiic theory of coiiimoa property resource exploitation. A Theory of Open Access and Common Property Resource Exploitation In the opening chapter, a distinction between open access resources and common property was implied. Before erecting a theory of exploita- tion, more explicit definitions of the resources are needed. Open access resources are those that arc open to exploitation by any who possess, or may ever possess, the physical ability to exploit the resource. In terras of ownership, the resource is not owned by djiy group comprising fewer people than the world population. The effec- tiveness of world ownership as an institution to implement management goals is sufficiently limited to permit acceptance of "open access" as synonjTuous with "no ownership" when applied to resources. The terra "cormion property," when applied to resources, implies that ovsmership exists by use of the word "property" but that ownership is exercised by a group of people in "common," for example, the citizens of a state or country. Institutions for attaining optimal exploitation rates may or may not exist but the implication is that the "common" group is not so large as to make their creation impossible. The key difference between "common" and "private" property resources lies in the behavior of the individual exploiter. In the common property situation, each individual, playing an unrestrained profit-seeking role. 18 will follow a course of action that is inconsistent vzilh an optimal use rate for tlie resource as a v;hole anrl that does not maximize profit for the group exercising the common property rights. In the cnse of private property, the expectation is that the individual, in pursuing a profit maximizing course, will act in a manner consistent V7ith optimal use of the resource as a whole assuming no technical externalities. Examples illustrating these essential differences exist in the form of land and oil pools in common and private property situations and fish in open access (high seas) and regulated common property (territorial waters) situations. Wlien arraying resources on a scale denoting then to be open access, common property, or private property, a continuum forms with no sharp demarcation between the various classes. A different and helpful classification of resources by their reaction to time-varying use rates is presented by S. V. Ciriacy-Wantrup [12, pp. 42, 43]. Some relevant literature on fisheries economics j.ncludes the seminal articles by H. Scott Gordon [19] and Anthony Scott [28], as well as the work of Christy and Scott [11], Crutchfield and Pontecorvo [14], Crutchfield and Zellner [15], and Daniel Bromley [9]. The paper by Bromley presents a provocative literature review. A comprehensive review of the work just cited would be redundant in view of Bromley's [9] work. However, acknowledgment must be made of the significant contributions to fishery theory of these authors. The theory developed here undoubtedly owes much to these authors but the debt is in the form of general knowledge rather than specific contributions. The resource to be exploited is assumed to be a flow resource in that it provides an exploitable flow of goods or services — fish, wild- life, scenic beauty, water, or capacity to absorb man-made effluent — from a given area over time. The resource may or may not be affected .19 by exploitation rates, but aome exploitation I'ate must, at sorae time, be positive in order for the resource to be of interest and maintain its resource character. In addition, the marginal utility derived from exploiting the resource must be positive in the absence of externalities. That is, the resource must not be a "free good." This qualification leaves the definition broader than may be inmiediately apparent. For example, stars of the seventh order of magnitude provide a flow of star- shine that is exploited at a positive rate by astronomers who delight in viewing seventh order stars. The qualification does state that for something to attain resource character, it must somehow affect humans. In this sense, orbital bodies under the direct gravitational influence of seventh order stars do not qualify as resources at the present tim^e. The resources of interest are those that require human effort to maintain a positive exploitation rate and thus have positive costs asso- ciated with their exploitation. The effort required for positive resource exploitation will vary over resources and is considered to be composed of inputs combined in constant proportions (linear expansion path) and treated as a single input. Physical returns to effort are assumed to increase but at a decreasing rate beyond some level of input. The condition of the resource, including qualitative factors, is assumed to be expressed by a single quantity index at any point in time. This assumption is, admittedly, heroic, but does much to facilitate the following exposition and, for a fishery, may not be so unreasonable as it first sounds. Demand for the product and factor supply curves are assumed to be less than perfectly elastic to the industry but perfectly elastic as viewed by the individual firm. The variables involved in open access or common property resource exploitation are: 20 Y. = output of producer i clvriiig a unit interval ot tine, t; e.g., a week, moath, year, decade, etc. Y = total output for the industry during unit time interval t. X. = input or effort of producer i durincr t. xt X = total industry input during t. P = price of the output during t, arisumed constant over producers. P = input price, identical foi" all producers, during t. R = a quantity index reflecting the condition of the resource during t. n = number of producers involved in the resource industry during t. TR.^ = total revenue for producer i during t. xt TR = industry total revenue during t. TC . = total cost to producer i during unit time interval t including It ' a "normal" return to "ii:ced" resources. TC = industry total cost during t. NR.^ = TR. - TC.^, net revenue of producer i during t or "pure xt It It' " ■ profits. " NR = TR - TC , industry net revenue (pure profits) during t. In generalized functional notation, the relationships of interest, their rates of change, and the directions of rates of change are as follows : 9. Individual output (2.42) Y.^ = Y.(X.^, R^) It X xt' t (2. A3) 9Y^^/3X^^ > 0 (2.44) 3^Y^j./3X.^^ > 0 , X.J. < X.^ 21 (2. /,4a) 3\j./9\/ < 0 , X.^^ > X.^ (2.45) 9Y.^/3R^ > 0 (2.46) S'^'Y. /SR ^ > 0 , R < R""^ (2.46a) d^Y. /[)R ^ < 0 , R > R"'" (2.47) 8^Y.^/8X.^3r^ > 0 xt It t 9Y. SY (2.48) dY.^ = ^;^ dX.+ -^r^ 6R it dX. It dR t it t 9 9^.. , 8^Y 9^Y (2.49) d^Y.^ = ^ dX./ + 2 x^— ^-^ dX. dR^ + z- dR^ It 9^_ 2 It 9X.^9R^ It t 3j^ 2 t it t 10. Individual effort and numbers of individual producers (2.50) X.^ = X.(NR^^_^) , r = 1, ..., k , 0 1 X. (NR. ^..„) < X.^ (2.50a) X^j. = X^^, X. (NR.^_^) > X^^ (2.51) ^\t^^^\t-T ^ ° ' "^ " ^' •••' ^ ' ° -h^^\t-r^ ^ \^ (2.52) 9^X.^/9NR.^ 9NR.^ >0 , l n^ (2.54) 9nj./9NRj._j. > 0 , r = 1, ..., k (2.55) 9^n^/9NR 9NR^ >0 , l 0 13. Total output (2.62) Y^ = S.^t Y.^ (2.63) 3Yj./8Y^^_ = 1 (2.64) 8Y^/3n^ ~ S.^^^t Y.^/n^ + ^.^t SY.^/9n^ where, from (2.49), (2.66), and (2.64), 8Y. /5n = OY. /9R JOR /3X )(9X /Sn ) < 0 it t it t t t L L 9Y ^ 3Y^ (2.65) dY =9^dn +i:.^^t3Y-d^'it . ._. Equation (2.42) describes individual output (harvest in pounds, numbers, board feet, acre feet, etc., per time unit) as a function of individual effort expended and the condition of the resource. Equations (2.43), (2.44), and (2.44a) describe the return to an increment of effort, assuming resource condition constant, as increasing at first at an increasing rate but eventually (beyond input level X^ ) increasing at a declining rate. In more technical economic terms, equation (2.42) is a production function which exhibits diminishing marginal returns to effort beyond input level X^^. Further, given constant input (effort) and product prices, the profit-maximizing producer will operate at or 23 beyond input level X. if at all. Equations (2.A5), (2.46), and (2.46a) indicate that increases in the resource condition (effort constant) increase individual output along a sigmoid path, at an increasing rate at first but evertually at a decreasing rate. Viewed another V7ay, equations (2.45) - (2.46a) indicate that the efficiency of a given amount of effort increases as it is applied to increasingly dense resource stocks but at a decreasing rate throughout. In fisheries, effort may be divided into search time, actual harvest time, and on-board processing time. For a given amount of effort, increases in density of fish will at first add to catch at an increasing rate as both search time and actual harvest time are large in relation to on-board processing time and are decreasing while processing time increases. As processing time, V7hich is independent of stock density, comes to dominate in the total effort, increases in stock density will increase catch at a decreasing rate. Equation (2.47) says that effort and resource condi- tion are complementary in their effect on output, increases in resource condition increasing the rate of increase in product due to increases in effort and vice versa. Equation (2.48) expresses the unconstrained ("total") change in individual output in tenns of partial rates of change and unconstrained increments of effort and resource condition. The direction of change in output is predictable from (2.48) alone only when effort and resource condition move in the same direction in which case output will move in the same direction as effort and resource condition. The direction of change in the rate at which output is changing, as given by (2.49), depends upon the relative directions of change in effort and resource conditions as well as the level of effort and resource conditions. For similar movements in effort and resource condition below X. and R , 1 24 output will increase at an increasing rate. The direction of rate of change above iiiput levels X." and R' for movements of effort and resource condition in the same direction will depend on the relative magnitudes of (2.44n) and (2.46a) versus (2.47) and t)ie relative size of the changes in inputs. Equation (2.48) is particularly interesting when divided through by the increment in effort, dX , and written as (2.66) in which form it expresses the unconstrained change in output resulting from a change in effort (numbers of firms constant). 3Y. dR (2.66) dY. /dX. = 3Y. /9X. + ^*^ ^ it it it it 3r dX. t xt To the individual member of an industry with many producers, the term dR /dX is zero. That is, he neglects changes in the resource condi- tion that result from changes in the effort he expends. This may be rational for the individual since the cost of considering this small change in his decision process probably outweighs the benefits to be obtained from considering it. However, for the industry as a whole, the effect of changes in effort on the resource condition is not negli- gible. This discrepancy leads to the difference between the sum of changes in output expected by individuals from individual changes in effort and the change in output for the industry as a whole resulting from the sum of individual changes in effort. The sum of changes expected by individuals is: (2.67) E. "t dY. /dX_ = I. "t dY.^/dX.^ 1=1 It it 1=1 it It while the actual change for the industry is: 9Y. dR (2.68) Z. "t dY. /dX.^ = E. "t dY./dX.^ + Z. "t ^^ ^ 1=1 It It 1=1 It It 1=1 9R^ dX. t it 25 Since dR /dX. is negative (it is the product of (2.60) and the total derivative of (2.56) assuming u constant and dX. /dX. = 0 for i ^ i) t J t It the actual change in total output from an increase in effort is smaller dY^ dR by the positive amount -Z._ t ,," -jri — than is the sum of changes t XL expected by individuals. This discrepancy, derived assuming the number of producers in the industry constant, is part of the reason that indi- vidual producers, following profit-maximizing courses of action, will not behave in a manner consistent with maximizing industry profits. Equations (2.50) and (2.50a) describe the effort of individual firms as a function of past net revenues up to a ceiling (X. ) beyond which individual firms find themselves incapable of increasing effort. Condition (2.51) says that higher past net revenues increase current effort, and condition (2.52) (for r = s) describes the rate of increase as constant or increasing for the range over which the function is defined on past net revenues. The sign of (2.52) (for r = s) is inter- preted to mean that, when hypothetical sets of past net revenues are compared, the increment in effort called forth by an increment in net revenue at a higher level of net revenue is at least as large as the increment of effort called forth at lower levels of net revenue. Such behavior is taken to be typical up to the ceiling (X. ) at which the individual cannot effectively increase effort. The plausibility of (2.52) (for r = s) rests on the assumption that individuals are more sensitive to changes in net revenue at high levels of net revenue (their adjustments are larger) than they are at low levels of net revenue. Equation (2.52) (for r < s) states that higher levels of net revenue in a given period reinforce the effects of net revenues from subsequent periods. Equations (2.53) - (2.55) describe numbers of 26 producers in any time interval as a function, similar to individual effort, of past net revenues of the industry. That is, entrants are seen to increase at a constant or increasing rate as a function of past levels of in'.lustry net revenue with levels in previous periods having a reinforcing effect on those in subsequent periods. Equation (2.56) states that total effort during any time interval is the sum of individual effort over the number of producers in the Industry during that interval. Equation (2.57) indicates that aggregate effort is measured in the same units as individual effort. Equation (2.58) defines the effort level of new entrants as being at the average for the industry. Were equations (2.53) - (2.55) to be developed for different size classes of producers, then (2.58) would be modified to reflect the effect of entry into each size class. Definition (2.58) is a sort of "minimum knowledge" relation and should be replaced if more information is known about entrants. Equation (2.59) describes the condition of the resource as an instantaneously adjusted function of effort. Conditions (2.60) and (2,61) state that the resource condition declines as a function of effort but at an algebraically increasing rate. While the particular form of (2.59) will depend upon the theory of the behavior of the resource under study, there are probably few exceptions to the limits imposed by (2.60) and (2.61). A resource may be depleted as effort Increases but it will be depleted less and less efficiently so that very large amounts of effort are required to finally destroy the resource. Equation (2.10) in the section on fish population theory, after modifi- cation to represent the biomass of all year-classes comprising the fish stock, may be substituted for (2.59) in a bioeconomic model of a fishery. 27 Equation (2.62) expresses total output as the sum of individual outputs over producers in the industry during time interval t. Equation (2,63) states that individuals make contributions to total output in the same magnitude in which individual output 5s measured. Definition (2.64) gives the change in total output resulting from nev? entry (or exit) as the sum of changes in individual output due to the additional depletion of the resource by the entrant, plus the product of the new entrant which is defined to be the average product of all producers in the industry. Definition (2.6A) could be improved by reflecting productivity of entrants by size class or incorporating more complete information on the productivity of entrants when such inform.ation is available. Equation (2.65) adds to the sum over producers of the behavior indicated by equation (2.48), the change in total output resulting from a change in the number of producers. That is, (2.65) takes into account the effect on total output of changes in established producer output (the sum over producers of the product of (2.48) and (2.63) as well as the effect on total output of new entrants (2.64)). Rewriting (2.65) as (2.69) using the rules of differential calculus and equation (2.66) helps to delineate these effects and to point out the discrepancy in situations arising from individual behavior as opposed to industry- oriented behavior. (2.69) dY^ = E.^^t (3Y.j./SR^)(8R^/3X^.)(3x^/9n^) dn^. + ^i=l^ (^it/\) '\ + Z.^-t (9Y^/8Y.^)OY.^/3X.^) dX.^ + ^1=1^ (3\/3Y.^)(3Y^^/3R^)(dR^/dX.j.) dX.^ 23 The first and fourth terms on the riglit-hand side, of (2.69) are negative while the second and third terms are positive. Assume, for the moment, constant product and input prices and past net revenues high enough to encourage increases in effort by individual firms as well as entry by new firms. Individual producers believe that they affect only the elements of term three from the right-hand side of (2.69) and will, individually, increase effort so long as that direct increment in value of output is greater than the increment in value of input required for its production, halting further increases when the two are equal. The ex ante equilibrium position for all producers together, when each pursues his selfish interests in an unregulated manner, is given by: (2.70) P ^ E "t 0Y_/3X. J dX.^ = P ^ Z. !^t dX_ yt 1=1 It It It xt 1=1 It or, if l^J^t dX^j. = 1 (2.70a) ? I. '^t (8Y. /9X. J dX.^ = P ^ yt 1=1 It It It xt or, if dX. =1 It (2.70b) E. "t P ,(8y. /3X.J = n P ^ 1=1 yt It It t xt or (2.70c) Z..;t Py,0Y^,/3X,,)/n^ - P,, Equations (2.70) - (2.70c) state an ex ante condition that individuals attempt to attain, namely to equate, on an individual basis, the value of the marginal product of the input with its price. This translates, on an industry-wide basis, to equating the value of the marginal product of a one-unit Increase in industry-wide effort to the price of the input (2.70a) or to equating the value of marginal product averaged over members of the industry to the price of the input (2.70c). These 29 conditions cannot obtain ex post and the left-hand side of (2.70) viil (assuming numbers of firms constant) be reduced by the product of P and the fourth teiin on the right-hand side of (2.69) so that the average for the industry of the actual value of marginal product of effort is less than the price of that effort as indicated in (2.71). (2- 71) ^t h=l' t^^^it/^^it) ■' (9Y,,/9\)(dR^/c^X.^)] dX.^/n^ < P^^ This is not the final situation for the industry as a ichole. Past net revenues were assumed to be high enough to entice new entrants. New entrants have a mixed effect on output: they tend to reduce it by depleting the resource through increases in effort (term one on the right-hand side of (2.69)) but they increase it by the average produc- tivity for the industry (term two of (2.69)). Thus, new entrants may have a positive, negative, or nei\tral effect on total output. However, new entrants will expect to receive the average revenue for the industry as a whole and will plan to enter, ex ante, so long as industry net revenue (or average net revenue) is positive, stopping when average industry revenue (marginal revenue to entrant) equals average industry cost (marginal cost to entrant). However, all the entrants together affect the resource by depleting it so that, ex post, the increment to industry revenue from entry will be less than average factor cost by the value of the marginal depletion caused by the new entrants (P times term one of (2.69)). Thus, the increment in value of total output (all prices constant) is made up of the increment due to entrants and the increment due to expansion of effort by established members of the industry. For both increments, ex post value of marginal product for the industry is less than cost of the marginal input although individ- uals seek ex ante to equate apparent value of marginal product and cost 30 of marginal input. Sinco cogIg must equal revenues ex 2ps_t, the nega- tive net marginal revenues must he home hy the indiviJ.ial J'inus in the industry and may be evident as lov; incomes or less than "noriiial" returns. Thus, high past net revenues lead to lov7 net revenues In the current time period and the unstable nature of the situation is apparent. A stable situation may prevail only if firms continuously accept less than "normal" returns or if all firms in the industry luckilj' discover that proper ratio of privately expected value of marginal product to marginal factor cost that equates the increment in value of output for the industry to the increment in industry cost. A third alternative, in which firms learn to reckon all costs (voluntarily take the viewpoint of the industry) seems unworkable since firms would not be likely to have the information or incentives to take the viewpoint of the industry. The first alternative of sustained below "normal" returns may explain part of the behavior of som.e open access or comriion property resource industries, especially when "normal" returns origi- nally are based on acquisition value of inputs and not salvage value (see [9]). The second alternative may contain some explanatory power also if the marginal returns indicated do not (as they do not here) recognize uncertainty. That is, due to uncertainty, firms may attempt to maintain a ratio of value marginal product to input price that is consistently greater than one so that the ex post result from uncer- tainty planning may be closer to the value marginal product expected by the individual firm than is predicted by theory under certainty. Although these factors may contribute to a partially stable situation, they do not lead to an equilibrium in the sense of equating marginal factor returns with marginal factor cost. 31 This section is best sumTnarized by presenting, as briefly as possible, the conclusions of the theory of open access resource exploi- tation under variable prices, i.e., where input and product prices are, respectively, functions of input and product quantities. A given incre- ment in total output, dY given by (2.75), is attributable to increments in the effort of established firms, E. ,t dX. , as well as in effort due 1=1 it to entry, ^._,t X. /n dn , which sum to give the total increment in effort, dX . To maximize industry revenue, the increment to total revenue is equated to the increment in total cost or: (2.72) (P + Y dP /dY ) dY = (P + X dP /dX ) dX yt t yt t t ^ xt t xt t^ t Individual establislied producers see their marginal products as a func- tion of their effort alone and, taking price as constant, collectively try to equate marginal revenue product to marginal factor cost as given by equation (2.70). Entrants, who enter at average levels of produc- tivity and average effort expenditure, perceive the marginal return to entry as the average return for the industry or P Y /n and the mar- ginal cost of entry as the average cost for the industry or P X /n . (The marginal cost of a unit of effort from expansion by established firms is assumed to be the same as the marginal cost of a unit of effort by entry.) The marginal conditions for a static entry situation from the individuals' point of view, are: (2.73) Py^ Y^/n^ dn^ = P^^ X^/n^ dn^ The condition that established industry members and entering firms, acting as individuals, attempt to attain is given by the sum of (2.70) a and (2.73) or: (2.74) P^^ [l.Jlt 0Y,^/8X.^) dX.^ + (Y^/n^) dn^] = P^^ [l.J^t dX.^ 32 The riglit-hand side of (2. 74) corresponds to the riylil-hand side ol (2.72) if input supply is assumed to be infinite at a constant price (as it is assumed by individuals). The left-hand side of (2.74), :n addition to considering the effect of a change in output on output price to be zero (as individual producers consider it) , neglects to take into account the depleting effect of increased effort on the resource. To equate the value of the marginal increment in output for the industry to the cost of the marginal increments in effort required to produce it involves, ignoring price effects, satisfaction of: (2.75) P dY = P (E "t dX. + (X /n ) dn ) yt t xt 1=1 It t t t Theory indicates that for maximum industry profits to be obtained (monopoly and monopsony profits) equation (2.72) must be satisfied for the industry. The competitive industry situation (zero profits, normal returns included as a cost, guaranteed by the satisfaction of (2.73) under freedom of entry) is realized by satisfaction of (2.75). A con- dition of chronic below-normal returns is attained when individual producers and entrants attempt to satisfy (2.74). The crux of the problem at hand is that individuals involved in exploiting an open access or unregulated common property resource \>7ill attempt to satisfy equation (2.74), resulting in chronically low returns in resource industries involving no, or ineffective, ownership of the resource. The ensuing chapters will be concerned with determining the extent of possible gains from institutions (policies) designed to correct the problem of low returns. Any possible gains must, of course, be weighed against costs of implementing the policies necessary to attain the gain. The follow- ing section describes a bioeconomic model of a fishery, necessary for empirical work, in theoretical terms. 33 Bloecouoinic Theory of a Fishery Earlier sections of this chapter were concerned with the theoret- ical behavior of a particular year-class in a closed stock of fish and with the theory of oiploitation of an open access resource. This sec- tion combines the efforts of earlier sections into a bioeconomic theory of a fishery that will be useful in analyzing the shrimp industry. For a slightly different development, and one that incorporates the effects of "vessel crowding" — assumed negligible here — see the article by V. L. Smith [29]. Equation (2.30a) describes the weight of the catch from a partic- ular year-class as a function of effort and the biomass of the year- class. In most fisheries, the catch is actually made up of fish from several year-classes, in general J year-classes, so that (2.30a) should be rewritten in terms of a year-class j where j = 1, ...» J. Equation (2.42) gives the output of an individual producer in teinns of individual effort and resource condition while equation (2.62) defines the output for the industry. Modifying and combining (2.30a), (2.42), and (2.62), total industry output is seen to be (2.76), the sum over individuals of the catches from different year-classes. (2.76) Y^ = E. ^t Z.-^T Y..(X. . B.J t 1=1 j=l ij ' It' 2^ The biomass of a particular year-class is (abstracting from the effects of varying stock density on growth and mortality rates) a function of the growth and mortality rates natural to the species , the fishing mortality the year-class has suffered, and the size (in numbers) of the parent (spawning) population or E._. N where all year-classes at ^ ^1 J o least as old as j are spawners and t is the "birth" year of the year- class in question. 34 Total revenue to the industry, t>ie sum uf total revenues to indi- viduals, involves tlie product of the weight of each year-class in the catch times the price per unit v.'civ,ht ccr.inianucd hy tlie year-class {for example, different size shrimp, corresponding; to different ages, hring different prices per pound). That is: (2.77) TR = I. !}t Z.^^ P .^ Y.. (X. . B.J t 1=1 j = l yjt ij It' jt Total cost is the sum of individual total costs as given by the product of total effort (2.56) and price per unit effort P xt (2.78) TC^ = P X = P Z. ^t X t xt t xt 1=1 It Demand price, P . , is taken to be a declining function of output while yjt' input price, P , is assumed to be an increasing function of input quantity. However, individuals, and the industry, are assumed to treat prices as if there were no quantity effects on prices, thus eliminating monopoly- and monopsony-type price effects. For equilibrium to occur in the industry, the value of increases in output due to increases in effort must exactly offset the increase in costs due to increases in effort (due to expansion by established firms and entry). Further, the value of an increase in effort due to expansion by established firms (the "intensive margin," see [29]) must equal the value of an increase in output due to entry in order for stability to occur on the "capital" side of the produc- tion system. Stability of the fish stock requires that decreases in the stock due to fishing and natural mortality are just offset by the sum of increases in biomass due to growth in weight and recruitment. In addi- tion, the number of spawners , Z. . N. , must remain constant if that number is equal to or less than the number required to produce the maximum size spawn that the biological system will support. (For example, there may be some number of eggs above which further egg production is super- fluous so far as maintaining or adding to the adult stock is concerned.) 33 At some level of net revenue (zero, it net revenue is synonymous with pure profits and certainty is assumed) equilibrium may occur in the fisbci-y in the sense that increments to value equal increments to cost and fish stock is stable (catch equals sustainable yield where sustainable yield is that yield that may be taken in perpetuity without affecting the stock). The condition (2.73) applied to the fisheries assures that the net revenue level at industry equilibrium is zero. Mathematically, the equilibrium conditions are formed by setting the total derivative of net revenue, equation (2.77) less equation (2.78), equal to zero and satisfying the additional constraints that the time rate of change in biomass is zero as is the change in num.ber of spaw-ners. The conditions are: (2.79) Z. "t l.\ P .^ 1=1 j = l yjt ^dY.. 8y.. 8b. \ ^ It jt It/ 8Y.. Y.. 9Y.. j_ iJt . xit J . lit ,^ + 3 — ^— + — ^- dn^ + ^p ■' dB_ dn^ n^ t oB.^ it t t jt -J - P ^ f E "t dX.^ + — dn I = 0 xt \ 1=1 It n t / (2.80) Z/, dB. = 0 (2.81) Z/. dN. = 0 While (2.79) represents the conditions for competitive industry equilib- rium (zero profits), individuals do not take into account the indirect effects of their actions and will, as pointed out in the preceding sec- tion, attempt to expand output by increasing efforts, thus raising marginal factor costs (by raising P ^) and lowering value marginal pro- ducts (by lowering P , through the effect of diminishing returns to effort and through depletion of the resource) , resulting in the left 36 side of (2.79) being less than zero. If (2.80) and (2.81) are satis- fied, (2.79) may be persistently below zero, the negative net marginal value products being absorbed in incomes tc the fisheriaen belovj acqui- sition cost incomes (but above salvage valr.e ircomes) . In order to assure equilibrium by satisfaction of (2.79), some management authority need only levy on the industry a tax on entry (license fee, L) equal to the value of the reduction in output caused by entrants or 8Y.. 8B. 9X (2.82) L = E "t E. . P .^ ~^3-J^^ dn^ 1=1 1=1 yit 3B. dX dn t -* ■^-' jt t t and a tax on individual landings (landings fee, D) equal to the reduc- tion in value caused by expansion of effort by established firms or (2.83) D = Z "t E.^ P _ -^-^^3-1^ dX.^ 1=1 J=l yjt 3B dX^^ It where P . is the prevailing price at contemporaneous industry output. If tax-incidence problems are solved, this Pareto-ef f icient competitive industry equilibrium is as optimal as any other Pareto-ef f icient point. If a social welfare function is devised that acquiesces to the consumer desires expressed in the demand function, then this equilibrium is socially optimal. Although the charges needed (L and D) to manage a fishery in an efficient zero-profit manner can be specified as theoretical aggregates, the pattern of license fees for vessels of varying sizes and efficien- cies and the pattern of landings fees for fish of different sizes and per unit values are not so readily apparent. For heterogeneous firms and landings sizes, the charge levied may well influence the pattern of landings sizes and/or the characteristics of entering firms. The direc- tion of such influence is not obvious from the static considerations given here and requires modification and adaptation of the theory, by 37 specific industry, ivit.o a v;orkable dynamic model capable of evaluating alternative control strategies (policies). The theory presented here is modified and extended into a dyna:,! i c model capable of analyzing the Gulf of Mexico shrimp industry in Chapter III. CHAPTER III GULF OF MEXICO SHRIMP INDUSTRY; DESCRIPTION AND MODEL The Gulf of Mexico shrimp industry may be divided into three seg- ments. The basic segment is formed by the natural shrimp resource and the dynamics of its population behavior. A second segment is the fleet of boats and vessels that is involved in capturing the basic resource. The third segment consists of the processing and marketing channels that facilitate the movement of shrimp from the point of first sale at dock- side to the consumer's table. This chapter presents a brief description of the Gulf of Mexico shrimp industry and then, in somewhat more detail, an abstract model that represents the essential workings of the industry. Description of the Industry The descriptive portion draws heavily on work done at the University of Florida by David A. Whittaker, Jr. [33], C. C. Osterbind and R. A. Pantier [27], and Roy L. Lassiter [22], as well as National Marine Fisheries Service (formerly Bureau of Commercial Fisheries) publications by John P. Doll [16] and Kenneth W. Osborn, Bruce W. Maghan, and Shelby B. Drummond [26] , and a dissertation completed at the University of Rhode Island by Richard James Berry [7]. The Gulf Shrimp Resource The commercially important Gulf shrimp resource is comprised largely of three species of shrimp: brown shrimp, Penaeus aztecus; pink shrimp, 38 39 p. duo r a rum; and white shrimp, P. setiferus. In addition, small numbers of a smaller shrimp called seabob , Xiphoponaeus kroveri, are taken near the outlets of Louisiana rivers. The royal red shrimp, Hymenopenaeus robustus, is harvested in depths of from 200 to 300 fathoms (one fsthom equals six feet) in the waters off the east and southwest coasts of Florida and southv^est of the Mississippi River Delta. The Penaeus species have similar life cycles and habits. The adult shrimp spawn offshore and the larvae make their way back into the coastal estuarine systems, V7here they develop into juvenile shrimp. The juvenile shrimp begin to migrate back to the open sea where, upon reaching adulthood and spawning, the cycle is completed. Individual shrimp may live from eighteen months to tvjo years and reach lengths of 170 mm. (6.7 in.) for males and 200 mm. (7.9 in.) for females. Shrimp are generally considered an annual crop, however, and are harvested from the time they are juveniles in the estuaries. Brovm and pink shrimp are nocturnal in habit and burrow during the day into the mud and coral silt bottoms which they respectively seem to prefer. Wliite shrimp, on the other hand, are active during daylight hours and burrow into the mud bottom at night. Brown shrimp are found in heaviest concentrations along the Texas coast, white shrimp along the Louisiana coast, and pink shrimp off the coast of Florida near the Dry Tortugas and Sanibcl Island and in the Gulf of Campeche off the northwestern coast of the Yucatan Peninsula. Figure 3.1 (after Lassiter [22, p. 2]) depicts the seven areas of the Gulf of Mexico that comprise the study area and Table 3.1 gives landings by area and species for the years 1967, 1968, and 1969 (see also [2]). Together, these references depict the recent occurrences of shrimp in commercial harvests and, presumably, the distribution of the various shrimp species. AG t^i^ki^^^ Area I ^/^* >^'^J!!^ Q'-^- 85° I Pensacola, Florida, to the Mississippi River Mississippi River to Texas Texas Coast ^ High Seas Off Mexican Coast West of Longitude 94 High Seas Off Obregon and Campeche Figure 3.1. Major Shrimp Fishing Areas in the Gulf of Mexico '^il o H CO cu •H O en 5-J -J CM CO •o- in CT. CM vO Cv) CJ^ CM o CO in 00 r~. o vO rH r^ r^ CO Ct #t ^ *i *s «K ^ #w ^ r* r. <\ o in f^ CO O • • • ■ • • • • • • • c-i in <3- CM r^ r^ r^ CM .D X: o O t-l in m O cy\ ^ ^. CO ^ »< #. » #v r. C3 in in r^ CO ro v^ 4-' cy> CM in vD 00 CTl 00 in CM CM o C) • • • « ■ • • • • • • • CU vO CNl .H O r-- <}■ CO rH rH CO o -* B o tH *^ .Q oo CO rH ^ (-. (T. in m r^ T-t 00 *^ •* r. O cyi O vCi in vO CM C-) vO o a CNJ r-t <3- CM rH - CO VD o rH T-H rH rH rH CNl 00 >H CO 00 iH O rH r-^ r- in CO r^ bs and al Red 3 CN (y. eg o ^ bs and al Red CTs CO C CO CO 'd pi CO 00 CO C (U o >, rH C 0) o >, r-( a Q) O >i r-t 5 M u ^ o c3 3 ^ 4-1 43 o CO s ^ 4-1 XI o CO o C •H nJ Pi J-l o c •H CO ai 4J o c •H CO Pi 4-1 !-i •H r; 0) o u ■H r" QJ O u •H rC 0) o pq Cli CO H PQ PU ^ C/3 H P3 PL, 3 C/3 H r^ 00 CTi vO vO vO 0^ cr< CTi M rH <-A < m o oo c •H C o CO Q x: CO CM U CO d 0) o o 3 • u 4J 'V -o 00 (U 14H c T3 4-1 rH •H ^3 !-i 3 x: CO O O CO D- CO 4J 0) S o ^ • • c 0) «\ QJ u • >. C M W CO O 3 • CCJ^ X3 o CO • /<2 Table 3.2 transforms the aci.'j;-il landings of Tdble 3.1 into percent- ages of total landings vhic]i inore rr.<- vD O P~. rO CO iX) > 0) J-l M CO 4-l o c o u 0) o o o^ ro ~d- 00 iH 00 O O rH o o-i in csi O O O CO j3 tn vO ^ o o m in C 0) CO Pi en iH C 0) o >^ S ^ W JD o O C -H CO Pi M -H x: 0) PQ Pm 3 to o o o v£5 r^ rH o rH ro CO rH i-H O O CO o o Csl O CO r-l O rH CO O O ^ CO CO o o in vO CO Pi to iH J3 CO o >^ J2 O CO Pi , c o Vl CO o • 3 c^ o o o CO /:/< o > CO (0 (U •H a 0) 00 O CO o rH in ro 00 r^i U-) u~) iH r^ r~~ u-i ■H cr. O- ro r-l CTv r^ VD LT) CM m ■u o rH o CN iH o o r^ CM 00 CM r^ vo iH r- o CM CM CO in en O in C3^ CO o o- in o rH < 1—1 5 ^ ■U ^ O to o c •H cfl Pi j-i l-l •H r; 0) O m P^ 3 W H cr\ r- in in in o O CNJ O in 00 O CTN 0^ CO CO , •-\ 3 ^ ■U -Q o to o C •H 03 Pi 4J v< •H ^ (U O PQ P-l 3 C/5 H o o o o in CO CO Cvl CM CO in o in CO CM O ■u • c CO QJ O (U V4 T-{ cu Xi IX cC H in o C • o •H 00 ■ c o CO •H 4J T3 c CO C CO •a 3 X O ■u a 1-1 o CO )-l o CO UH 4-1 0) rH Id 0) CD D • CO i-{ Id •Td 0) -H 0) 4J P. -a •u CO e Td M CJ o CO O •H o CU Td 4J 0) c o n •H • • c (U (U o o >. d o u =3 o • D J2 ^ o o iT Xi CJ CO 45 grass is present or the bcttora ic scuddad with coral, large sponges or other obstructions, and distance from port. Thus, Tables 3.1 -■ 3.3 should be interpreted as indicating conicercia] ly important concentra- tions of shriap, given current technology and knowledge of bottom conditions. In addition to variation by area, shrimp concentrations vary in a seasonal pattern by species. Osbcrn et al. [26] have summarized five years of data (1959-63) to indicate shrimp concentrations by area, species, and month of year. Their findings on density by area are roughly the same as those presented above. The seasonal patterns of abundance of the three species are such that shrimp are available in heav^' concentrations the year round. Brown shrimp concentrations support a summer and early fall fishery vjith 80 percent of the landings occurring from June to October and the peak catches occurring in July and August [26, p. 6], Pink shrimp support a year-round fishery although landings are somewhat lower during June through September and peak in December [26, p. 14]. Nearly 80 percent of the white shrimp land- ings are made in the fall from September to December [26, p. 10]. Although all three species of shrimp are harvested from the time they are juveniles in the estuarine systems (inshore) until they reach adulthood offshore, there are some striking differences in the percent- ages of the various species landed inshore versus offshore and in the depths of landing. For the study period 1959-63, [26] found that 80 percent of the brown shrimp landed were taken offshore, most of them in water between 11 and 30 fathoms in depth. Ninety-eight percent of the pink shrimp landed were taken offshore with the heaviest concentra- tion (nearly 80 percent) taken in 11 - 20-fathom depths. In contrast to the brown and pink species, 42 percent of the white shrimp landed AC) were taken in inshore waters. By depth, iiliout. 90 percent of tlie white shrimp landed \,'ere taken In less tVian 10 fatlsoins of vater. In summary, bro\n shrirp, Penaeus aatecus, are n'.OGt abundant in the summer and early fall in the offshore waters of Texar. . Louisiana, and, to a lesser extent, Mississippi and Alabama, Pink sbrjrap are abundant at all times except the late summer in the olfsliore waters of south- western Florida (Dry Tortugas and Sanibel Island) and tl;e western Yucatan Peninsula (Obregon and Gulf of Carapeche) . White shrlii'p are most abundant during the fall of the year about equally in the inshore and offshore waters of the coast of Louisiana and, to a lesser extent, Mississippi and eastern Texas. The concentrations of shrimp reported here doubtless reflect activity patterns of the shrimp fleet in that they are inferred from conunercial landings. However, the commercially important ccncen- trations of shrimp would seem to be fairly v?ell indicated by these data. The Gulf Shrimp Fleet In 1966 there were 7,739 boats and vessels in tJie Gulf shrimp industry operated by 13,756 regular and casual fishermen. These 7,739 craft were equipped with 9,969 otter trawl net units having a sweep capacity of 141,472 yards at mouth [23, p. 645]. Tabic 3.4 contains a breakdown of these statistics by state and by vessel and boat fisheries for 1966. By the definitions followed by the U.S. Department of Interior, a boat is a craft of less than five net register tons \,7l)ile a vessel is a craft of at least five net register tons. A register ton is a volume of 100 cubic feet which displaces 6,242.5 pounds of fresh water of maximum density. The designation "gross" refers to register tonnage calculated from the volume between decks below tlie tonnage deck and Table 3.4 Sumniary of shrimp otter trav/l boats, vesse. Is, fxshe ;rinen , and gear in the Gulf states, 1 966 Number Fishermen Otter Trawls Number Number Yds. at State Boats Regular Casual Number Mouth Fla. , W.C. 98 142 24 99 1,281 Alabama 203 311 43 203 3,900 Boat Mississippi 380 178 285 380 3,680 Fishery Louisiana 3,261 2,919 1,220 3,305 42,016 Texas 861 772 406 861 9,149 Total, excl. of dupl. 4,797 4,312 1,978 4,842 59,942 Vessels Fishermen Otter Traxjls Gross Yds. at State Number Tonnage Number Number Mouth Fla. , W.C. 886^ 43,686 2,140 1,664 25,912 Alabama 366 14,050 882 598 9,730 Vessel Mississippi 410 16,835 1,020 665 10,878 Fishery Louisiana 1,342 59,007 3,524 2,354 37,289 Texas 1,409 77,348 3,787 2,646 41,697 Total, excl. of dupl. 2,942 132,149 7,466 5,127 81,530 Boats and Vessels Fishermen Otter Trawls Yds. at State Number Number Number Mouth Total Fla. , W. C. 984 2,306 1,763 27,193 (Boat Alabama 569 1,236 801 13,630 and Mississippi 790 1,483 1,045 14,558 Vessel Louisiana 4, ,603 7,663 5,659 79,305 Fishery) Texas 2, ,270 4,965 3,507 50,846 Total, excl. of dupl. 7 ,739 13,756 9,969 141,472 Printed as 386, apparently a misprint. Source: Fishery Statistics of the United States, 1966, Stat. Dig. No. 60, U. S. Dept. of the Int., Fish and Wildlife Service, Bureau of Commercial Fisheries, 1968. II 4. II A 8 within permanent structures above the tonnage deck, while the "net' designation refers to the gross tonnage adjusted for cei^tain allowable exemptions. A regular fisherman earns more than half his income from fishing while a casual fisherman earns less than half his income from fishing. An otter trawl net (see Figure 3.2) is designed to be towed along the bottom, collecting shrimp at the mouth and funneling them into the cod end of the net. Table 3.4 indicates that there are 2,942 vessels in the Gulf shrimp industry manned by 7,466 regular fishermen. These vessels operate 5,127 otter trawl net units having a combined sv;eep of 81,530 yards at mouth. Since each vessel operates either one or tv;o net units, there must be (5,127 - 2,942) = 2,185 double rig vessels operating 4,370 net units and (2,942 - 2,185) = 757 single rig vessels operating 757 net units. Assuming single rig net units are twice as large across the mouth as double rig net units [26, p. 4], there are 4,370 + 2(757) = 5,834 double rig net unit equivalents operating in the Gulf shrimp industry measuring 81,530 yards at mouth. The average double rig net unit is 13.86 yards (41.58 feet) across the mouth v/hile a single rig net unit is 27.72 yards (83.16 feet) across the mouth. The average vessel in the Gulf shrimp industry tows nets having a sweep capacity of 27.72 yards (83.16 feet) across the mouth. In addition to the main nets, each vessel usually carries a ten-foot try-net used to locate profitable shrimp concentra- tions before the main nets are deployed. The distribution of vessels by states as shown in Table 3.4 corre- sponds closely to the distribution of landings by areas. Louisiana and Texas (Areas IV and V) lead in number of vessels and landings followed by Florida (Areas I, II, and to a large extent VII so far as vessels are concerned) and Mississippi and Alabama (Area III). Landings from 49 o i-i C-t, QJ Q 0} £3 CO H !-i (V 4-1 •P o 4-1 0) 0) > e •H to CM CO u Ml •H 50 Area VI are probably largely accounted for by Texfs Vfi.ssels while landings from Area VII are accounted for by Florida and, to a lesser extent, Texas vessels. Tabic 3.5 indicates the relative size composi- tion of the fleets landing shrimp in each state. The vessels landing catches in Alabama, Mississippi, and Louisiana tend to be relatively smaller than those landing catches in Texas and Florida. Tliere are 4,797 boats in the Gulf shrimp industry (Table 3.4) of which the majority (3,261) arc based in Louisiana. Florida has the smallest number of boats (98). These 4,797 boats are manned by 4,312 regular and 1,978 casual fishermen and carry 4,842 otter trawl net units with a sweep capacity of 59,94 2 yards at mouth. Assuming single rig nets are twice as large as individual double rig nets, there are 530 double-rigged boats equipped to tow tv7o nets having a width at mouth of 6.25 yards (18.75 feet) each. The majority of boats are single- rigged, towing one net having a sweep capacity of 12.5 yards (37.5 feet) at mouth. Many boats are manned by casual fishermen who, as a primary source of income, either engage their boats in another fishery or leave their boats idle and take jobs as shore workers or crew on craft employed outside the shrimp industry. As Table 3.4 indicates, the largest numbers of casual fishermen are found in Louisiana and fish the highly seasonal (late fall) white shrimp resource in the inshore or near off- shore waters. Alternative maritime employment for the Louisiana casual fisherman is available on oil company tugboats and service boats [22, p. 39]. Although boats outnumber vessels in the Gulf shrimp industry, vessels represent the most important segment of the industry, so far as fishing capacity is concerned, controlling 51.4 percent of the nets and 51 Table 3 .5. Summary of by tonnage shriir.p groups. otter , 1966 trav/1 vess< -Is of tlie Gulf states 5 •OSS mage Number by State Gi Tor 11a. , W.C. Alabama Miss: Lssippi Lo> aisinna T( ixas Total, of d excl. up] . 5 - 9 38 30 7 41 22 122 10 - 19 89 88 62 235 138 512 20 - 29 41 42 83 166 83 318 30 - 39 134 56 71 167 124 370 40 - 49 152 45 58 176 161 374 50 - 59 78 29 38 141 154 264 60 - 69 217 28 51 231 392 531 70 - 79 69 24 19 113 191 239 80 - 89 22 3 9 32 52 73 90 - 99 40 9 7 23 66 93 100 - 109 3 — 3 9 16 23 110 - 119 2 3 1 2 5 9 120 - 129 1 6 — 4 4 9 130 - 139 — 3 — 2 — 3 160 - 169 — — — — 1 1 190 - 199 — — 1 — — 1 Total vesse] .s 886 366 410 L,342 1 ,409 2 ,942 Total gross tonnage 43,682 14,050 16,835 59,007 77,348 132,149 Source: Fishery Statistics of the United States, 1966, Statistical Digest No. 60, United States Department of the Interior, Fish and Wildlife Service, Bureau of Commercial Fisheries, 1968. 52 57.6 percent of tlie sweep capacity. In terms of utilization, che vessel fleet probably accounts for a larger percentage, of the catch than the percent of sweep capacity indicates since nearly all the vessels fish on a year-round basis. To the extent that the offshore vessel fleet catch is of larger shrimp than the boat fleet catch, the vessel fleet accounts for an even larger proportion of the value of the shrimp catch since larger shrimp are more valuable. As for profitability of operation of the fleet and of vessels ver- sus boats, no data are available on boat operations since statistics are not gathered separately for boats. Table 3.6 presents costs and returns for a typical offshore Gulf shrimp vessel (see also [3]). The "return to management (gross return less all costs)" or net return is negative in this case. As shown in Table 3.6, this negative net return may serve to reduce owner share as in "return to investment" or operator share as in "return to labor and management." Caution must be used in applying these figures to vessels in different size classes or ultra- modern vessels of different efficiency. C. C. Osterbind and R. A. Pantier [27] and Roy L. Lassiter [22] present and analyze data from the 1950 's and early 1960 's on costs and returns in, and utilization of the Gulf shrimp fleet. These studies are valuable for a historical review as is the more recent Basic Economic Indicators: Shrimp, Atlantic and Gulf [1] published by the National Marine Fisheries Service. A feature of shrimp vessel operation bearing on costs and returns and adequately described elsewhere [27, 33] is the "share system." The "share system" is an arrangement whereby captain (whether or not he is the vessel owner) and crew share in the proceeds of the catch — and in part of the variable trip cost — in lieu of guaranteed salaries. Under t; 3 Table 3.6. Marino economics data - 65-foot GnTi of Mexico shrimp vessels Vessel Description; 65 feet, SO gross tons and 3-man crew (1967-1968 data) Expected Production and Prices; 183 fislnug diys, 100,000 pounds (50 tons) shrimp at $. 69'4/pound . Shrimp Variable Costs Season Total Vessel Repair $ 5,798 Gear Repair 5,450 Fuel 4,655 Galley 2,269 Ice 1,456 Other 1,190 Crewshare 16,553 Operator Share^ 8,276 Total Variable Costs $ 45,647 Fixed Costs Interest on Investment (8%) $ 9,168 Depreciation^ 8,604 Insurance , 3,791 Interest on Operating Capital (1/2 of 10%) 2,188 Administrative 2 ,597 Total Fixed Costs $ 26,348 Summary Variable and Fixed Costs $ 71,995 Gross Returns 69,400 Gross Returns Less Variable Costs 23,753 Return to Management (Gross Returns Less All Costs) -2,595 Return to Investment (Return to Management Plus 8% of $114,600) 6,573 (5.7%) Return to Labor and Management (Return to Management Plus Operator Share) 5,681 Captain's commission and wages actually received. Interest is charged against all investment and average operating capital whether or not borrowed. Investment is based upon returns to the vessel, a 15-year useful life and a 12 percent discount rate as determined by the National Marine Fisheries Service and for this vessel is $114,600. Depreciation is not standardized as in other marine economics data sheets but is as given in Working Paper No. 57 [1]. Source; Marine Advisory Program, Sea Grant, Oregon State University, Corvallis, Oregon. Prepared February 1971 from Working Paper No. 57, [1] Division of Economic Research, National Marine Fisheries Service [3]. 54 the share arrangement, the captain and crew receive a percentage of tb.e value of the catch, this percentage varying over vesf^els and portG and according to whether or not the captain is the vessel oumer. The share of the captain and c.vc\^ in variable codLs usually includes food and gear (net) repair, these costs being deducted from crew share. The obvious advantages of this arrangement are that it gives the cre\.' an incentive to maximize catch while holding down certain variable costs that are directly dependent on crew performance. The share system also guarantees short-run profit-maximizing behavior by a captain who is not the vessel owner and does not encourage loyalty of the crew to their emplo^'er. Such behavior may be at odds with the longer-run interests of the vessel owner. Since the share system is widely used, apparently many vessel owners feel that the advantages outweigh the disadvantages. Francis J. Captiva in a recent paper on "Changes in Gulf of Mexico Shrimp Trawler Design" [10] describes the recent shift in the Gulf shrimp industry to slightly larger vessels (80 to 100 feet) of stee] , fiberglass, or aluminum construction in place of the tradition.il wooden vessel. He describes the newly constructed vessels as being higher powered (from 400 up to 750 horsepower as compared to 150 - 200 horse- power on older vessels) with more comfortable crew quarters and more mechanized gear-handling and processing equipment, as well as design oriented toward diversification to allow handling various gears with little or no equipment modification. Modern electronic aids installed in duplicate, power steering with automatic, hand and remote controls, powerful remotely controlled trawl winches, and relocation of the con- trol bridge to provide a better view of the working deck are attributes of many of the newly constructed vessels. Mr. Captiva envisions in the future an even larger vessel (150 feet in length) incorporating computer 55 designed hull, the capability Lo handle a v;idp. variety of gears, new concepts in pi-opulsion and auxiliary pDv;er (specifically, a diesel- electric or gas turbine-electric syr.ten) and otlior innovations. This "dream" vessel, \7ith its increased hold and supply space and mechanized processing and freezing equipment, could serve as a motber-ship-catcher- ship, towing tour electro-shrimp trawls simultaneously. While changes in vessel design^ equipnient, and fishing techniques must meet the test of economic efficiency as well as technical feasi- bility, there are two recent developments that may be important for the Gulf shrimp industry. One of these concerns the development of the electro-shrimp trawl, which uses pulsed electric current to force shrimp up from their burrows, thus permitting 24-hour per day fishing with an increase in catching efficiency over the conventional trawl. Adoption of the electro-shrimp trawl by the Gulf shrimp fleet would have the effect of greatly increasing the potential effort (measured in 24-hour periods spent in actual fishing) of the fleet since vessels could, theoretically, fish continuously once they reached the fishing grounds and found profitable concentrations of shrimp. The other development concerns the discovery that royal red shrimp concentrate about the 49°F thermocline. By locating the 49''F thermocline and fishing at that depth, improved catches of royal red shrimp can be made [4]. The Expendable Bathythermograph System, originally developed for use by the U. S. Navy in locating the thermocline, is currently being used in experiments. Its cost apparently prohibits commercial adoption. The development of economically feasible gear with which to locate thermo- clines should lead to greater utilization of the royal red shrimp resource, thus expanding the shrimp supply. 56 Processing and Mai']'.rtin.o, Ilia Gull" Slirimp Catch Shrimp processing begins on hoard tht^. catching vessel v.'he7;e shrimp arc beheaded (thus losing about 38 percent of their body weight). They are then packed in ice or, on some of the larger modern vessels, frozen in five-pound cartons for direct marketing or in blocks for later thaw- ing and further processing. An exception occurs when heavy shrimp concentrations are located and/or fishing is close to shore. Under these conditions, the catch rate may be so high that beheading on board requires more fishing time than does returning the shrimp to shore. In this case, shrimp may be iced down whole and beheaded during shoreside processing. Once the domestic shrimp catch is ashore, most of it is sold as raw material to processing plants either directly or through "packing houses" which assemble shrimp for sale to processors. Figure 3.3 presents a detailed analysis of shrimp processing and marketing channels. About 80 percent of the U. S. shrimp catch is processed as a frozen product while the remainder is canned or dried. Much of the Pacific coast catch, especially Alaska's, as well as part of the New England catch is processed into canned or dried products. Thus at least 80 percent of the Gulf shrimp landings may be said to enter the frozen product market. The frozen shrimp are converted into three major prod- uct forms: raw headless, breaded, and peeled and deveined, in order of importance, with raw headless accounting for about 40 percent and the latter categories about 30 percent each of the weight of raw headless shrimp processed into these products in 1969. According to Miller et al. [2A, p. 29] trends indicate that breaded and peeled and deveined products will account for a growing share of the frozen shrimp total at 57 H •z w >-< trt n Pi H z^ w t: tj u .^ a. O H ti Pi:::2 R oo ^ M u >< CO 3 ^ HI M tJ t! ^ (jt kJ O HI ^ o Pi 3 t O O Q a Q <: o CJ s lii w c/^ CO >> w CO H c^ > tj 1-1 o H < H < M C^J c; O M w K^I p-l UJ CO Q a' i-> OJ CO ^ V cy ■rH 4-J --o c 4-1 •H O (0 CI) >. c. c3 •H g .-1 >. c O 0) x; ^s; 4-1 o }j ':^ XI 3 co (U O CU I-l x: c •H 4-1 C X! iH rt 3 ca X! O 0) 4-1 iH 0) 00 J-J ^ 3 •H !-i •H 4-1 4-1 U ,« o 0) j2 CO c 4J S o •H x: TJ CO M) 3 CO 3 CO 01 O (0 !-4 60 CO ,C 3 o 4J •H o. o. CO CO >. e Q) J3 •H U c; o fl.^ >-i e CO (U •H )J U-l CU J= o e CO 4-1 • d) o ro e E • 0) en > OJ o 4-1 0) e CO 4-1 3 (U •H • 60 4-1 iH 0) •H « •H rH lit o O 4-1 •H C3 •i-l TD U-l 4-1 • C 1— 1 •H CO U 00 >-l o £N to (1) 0) ^ 3 • c o O Cu •H u •H rH XI CO M W CO 13 a> (U CO •H >-i CO l__l ■H ;eight) character- istics of a recruit class. The fishin?; rportality coefficient (F. , ) is assumed to be a direct linear function of the effort expended in the area after shrimp reach some age in the fishery, say V, and zero before this age. (3.1) F..^^ =0 , t - k < V Number of shrimp surviving at the end of interval t is a declining expo- nential function of the mortality rates and the number present at the beginning of period t (end of period t - 1), The number surviving when t = k is the original recruit class, that is N..,, = R. ., . ij kk J.J K -<^jkt + "ijkt) (3.2) N.., = N. ., , e ijkt ijkt-1 The weight of an individual of age t - k is given by; (3.3) W. 1 - e 32i (t-k) + B.., 33i ijklt 31ij for females and for males is given by: P^/, 34i (3.4) W. 1 - e ^42i(^-^) -*■ \31 3 44i ijk2t 41ij L Shrimp are classified commercially according to number of tails per pound. If individual weight is measured in pounds, then the reciprocal of W. ., times a factor to arrive at heads-of f weight represents number of tails per pound. Given size of recruit classes and effort, equations (3.1) - (3.4) and aggregations of these equations describe the behavior of the shrimp population in the Gulf in terras of numbers and weight. In addition, a 62 policy variable is provided by V, tlie ape in tlic-. fishery at v/hich shrimp begin to be subjected to fishing mortality. The variable V may be manipulated by, for example, restrictions on mesh size, closed seasons or areas, or any combination of these uieasures. Variability in the model comes in the form of inter-period variation in sizes of recruit classes and varying fishing effort. The effort expended provides a link betvjeen the basic shrimp resource and the harvesting sector, the Gulf shrimp fleet. A Model of the Gulf Shrimp Fleet The craft in the Gulf shrimp f].eet may be divided into H size classes, vessels in each size class having a different sv-;eep capacity and, possibly, different cost characteristics. Larger vessels usually have greater sweep capacity and a day spent trawling by a vessc] of 2X yards sweep capacity may be considered as contributing roughly twice as much to fishing mortality as a day of trawling time by a vessel having X yards of sweep capacity. Thus, an arbitrarily chosen "standard" vessel size class having a "standard" sweep capacity may be established and the days spent trawling by vessels in other size classes may be adjusted by the ratio of sweep capacity of the vessel size class in ques- tion to that of the "standard" class. Thus, the model of the harvesting sector must be able to aggregate effort of diverse vessel size classes into the single effort index required by the basic resource sector model. In addition, the harvesting sector model must specify catch and gross revenue of vessels in each size class. Since prices vary according to Effort data are available in "days fished" — 24-hour periods spent in actual fishing activity. 63 size of shrimp (as expressed in tails per pound) the size composition of the catch must be knovm. In addition, cost per unit of effort is required to derive a measure of profitability. Profitability must be related to the intensity of fishing effort and to the entry and exit of fishing vessels to areas and the industry in order to determine effort vhich is needed as an input to the basic resource sector. The interface between the harvesting sector and the marketing and der..and sector is characterized by the weight and size composition of the catch and the ex-vessel price, by size class, paid for the catch. The following variables delineate the factors to be considered in a model of the Gulf shrimp fleet: C , = Catch (in numbers) of a craft of size class h (h = 1, ...» hijkt H) of species i in area j of recruit class R- -j. (^ge in fishery t - k) during interval t. Y = (1/2)2 ^, C, .., W.., = weight of catch C, ... . hijkt ^ '^ m=l hijkt ijkmt ^ hijkt P = Price per pound of shrimp in area j of age t - k and sex m jkmt and thus of count per pound 1/a W. ., vjhere a is a factor to convert to headless weight. ^\jt = (^/2^^i=l \=t-T^ Cl ^jkmt Sijkt ^^jkmt = Gross revenue of a craft of size class h in area j during period t. X^. = Effort in 24-hour periods (days fished) spent in actual fishing activity by a vessel of size class h in area j during interval t. n, = Number of craft of size class h fishing in area j during interval t. n,. = Number of craft of size class h with home port in area j Ihjt during interval t. 64 n„, . = New vessels of si'/.c class h having lioine port in area j 2njt entering fleet at beginning of time interval t so that "ihjt = "lhjt-1 '""2hjt S = Sx.7eep capacity (in yards along footrope of nets) of a vessel of size class h in area j during interval t. X.. = ^,^\ n, . fS, .^/S .^)X, .^ jt h=l hjt^ hjt rjt^ Tijt = Effort in standardized "days fished" in area j during interval t when vessel size class r is chosen as the "standard" class. V, = Cost (variable) of a day fishing by a marginal vessel of bjt size class h in area j during time period t. W, = Per time period value of sunk capital plus interest on ht this sum at a competitive rate prorated over the expected life of the sunk capital. %t = \jt-\jt\jt- V = Net revenue of a vessel of size class h in area j during period t. The relationships of interest are those leading to Di -^ and the rela- tionships relating effort and profitability. The number of shrimp of species i and age t - k caught by a vessel of size class h during period t is given by: (3 5) C = Vl^\it/^jt>^jt ^ ^^^ 'hijkt F..^^+M..^^ iJkt-1 -(F. ., + M. ., ) ^ _ ^ ^ ijkt ijkt' From (3.5) total catch, weight of catch, gross revenue, and net revenue per vessel may be calculated from their definitions. Firms owning vessels in the Gulf shrimp fleet must decide in which area their vessels will fish and how intensely they should fish. The 65 cost structure of vessels in each size class will depend, in addition to size characteristics, on the area of hem? port and the port area of current operation. Vessels fishing an area out of a temporary port may have higher cos uf. than vessels fishing the same area who are permanently based in a port in that area. Similarly, vessels of the same size class fishing the same area but from ports at different distances from the fishing ground will have different costs due to differences 5.n steaming time to and from the grounds. Thus, the cost of a unit of effort of a marginal vessel in an area v;ill appear as a step function vjhen plotted against the number of vessels fishing in the area. This cost will take on one value when a marginal vessel has its home port in the area and a higher value when the marginal vessel has a home port in some other area. It is probably reasonable to assume that migration patterns are such that the cost of fishing an area other than the home port area from the home port area is greater than or equal to the cost of fishing out of a temporary port in that area. Thus, vessels fishing an area other than their own may be considered to be fishing out of a temporary port in that area so that there will be only two values for V for a given vessel size class in a given area during a given time interval. Since vessels of a given size class have identical revenue functions but different cost functions depending on home port area, all vessels of a given size class based in an area will be fishing in that area before other vessels of the same size class migrate to the area. Thus, the cost, by size class, of a unit of effort by a marginal vessel in an area will depend on the relationship betv/een number of vessels fishing the area and number of vessels based in the area. Specifically: (3.6) V, .^ = v., .^ if n. _ < n hjt Ihjt hjt — Ihjt V =V >V ifn. >n \jt 2hjt Ihjt ^jt Ihjt 66 Net revenue by vessel size class may be calculii'red for each area once number of vessels and effort are determined. Entry into the fleet by new vessels is baaed on the profitability over a number (t ) of pre- vious time periods by vessels of the size class and area in question. Entry and exit are probably asymmetrical so that nev; vessels begin to be attracted only after cumulative net revenue reaches some positive level (say D-,, .) but vessels may not begin to exit until cu:nulative net reve- nue is lower or even negative (say D .). Over the range between these two values, vessels neither enter nor leave the fishery. That is: (3-^) "2hjt = ^71hj \l~t\ %T' \ll\ %T ^ ^Ihj "2hjt = ^72hj ^T=t-t^ %T' \l~t\ %T ^ ^hj "2h3t = ° ' ^.hj < ^'^-t^ Via- ' °lh3 Movements of vessels between areas from one time period to the next will occur by moving vessels to the area with highest net revenue in the previous time period from all other areas. In the event that the area with highest net return has fewer vessels fishing in it than have their home port there, so that the lower cost coefficient (V-,, . ) is in effect, the number of vessels required to bring the higher cost coefficient (V„, ) into effect will be moved to that area on a prorated basis from the other areas. In terms of behavioral relations: 7 (3.8) ^jt = "hjt-1 -^ ^r=l ^8hrj %t-l - °hrt-l^ %rt-l + "2hjt where D, . , = Max D, ^ , hit-l hst-1 ■^ s and n, _ ^ > n., .^ , Tijt-1 — lhjt-1 67 and: (3.9) n^^^ = n^.^^_^ - 3g,,^^.. (D^^^ ,__^ - D^.^^^_^) n^^^^_^ + n^^^^^ r=l, ...,j-l, j +],..., 7 except that, if rL < n,, , the fo]lov7ing reallocation is pcr- 113 1-1 injt-1 ° ^ formed. (3.10) n, _ = n,, . , + n„. .^ hjt lhjt-1 2nj t and: (3.11) Vt = Vt-1 - f^Shri ^^hit - \rt^ Vt-l^ 8hr j hj ■ ^s=l ^8hsj %3t - \st^ '''hst-l^ ^"lhjt-1 - \jt-l^ ^ ^2hrt r=^l, ...,j-l, j + 1, ...,7 Equations (3.8) and (3.9) indicate that new vessels begin to fish, or retiring vessels leave the fishery, in their home port area. These propositions are not unreasonable since new vessejs V7ill probably make some test runs near their home port until the vcGccl is deened seav7orthy. If the time interval used is short these test runs will probably require most of one time period to complete. Likevjise, vessels retiring from the fleet will most likely be found fishing in their home port area since cost conditions are most favorable there. Once vessels are located on a particular ground, they must decide how intensely to fish, that is, hov; many days fishing time per time interval to expend. Variability in fishing days per time interval is probably not large since, if it is profitable to initiate a trip at all, it pays to fish as intensely as possible while on the trip. However, to the extent that profitability affects the attitude of the crew about length of trip and layover time between trips, effort may vary. In addition, number of trips per time period may be varied for a particular vessel by postponing equipment maintenance and thus reducing layover time 60 in port. However, maintenance may be postponed only for a finite ariount of time so that for the avertige vessel in the area, this is probably an ineffective method of varying effort. Expected returns below the level at which average variable cost is covered will preclude fishing alto- gether. However, data are obtained on ex post results, not a priori expectations, so that a formulation indicating cessation of fishing activity is probably not reasonable unless expectations can be discovered and are homogeneous throughout the vessel size class in the area. The most reasonable proposition is that effort in days fished per time period varies between minimum and maximum levels as a linear function of net revenue in the preceding time period. (3.12) X^j,=X^^.^ , D^.,_,iD^^. \jt = ^(12)1 %t-l ' °lhj - %t-l - ^2hj \jt " "2hjt ' ^2hj -\jt-l Given the behavior described by equations (3.5) - (3.12), various totals of interest may be calculated by taking the proper sums. For example: H 3 7 t Weight of total catch in period t = E^ ^ E . ^ E . ^ E, ^ Y, ...^ " ^ h=l 1=1 j=l k=t-t hijkt or: Total standardized effort in period t = E. , X. J=l Jt By combining over vessel size classes, species, and areas, catches of shrimp of the opposite sex and different age that are of the same size, total weight of shrimp of a given size count may be obtained. Totals such as these are necessary input to the model of the shrimp resource as well as the model of the marketing and demand sector. A Kodelof the- Marke-ting__3nj_U&maml Sector "o£~t"he Gu"lf~Shr3.inp_ Industry Rather than attempt to build an original model of the marketing and demand sector of the Gulf shrimp industry, the approach follovied here is to take advantage of the work of John Doll entitled, _Ari_ Econometric Analysis of the U. S. Shrimp Market , [16]. Doll's quar- terly model [16, Chapter IV] is presented below with modification in symbols. In addition, a relation is presented to convert the single ex-vessel price appearing in his model into a range of prices for each size class of shrimp. The model is simultaneous, involving four jointly determined (endo- geneous) variables and nine predetermined variables. The jointly determined variables are [16, p. 65]: A = Total consumption, per quarter (t represents one quarter here and does not necessarily correspond to the time period of the basic resource or harvesting sector models) in millions of pounds, heads-off weight. B = Stocks held in cold storage at the end of the quarter, in t millions of pounds, heads-off weight. D = Wholesale price, frozen processed, 26-30 count, Chicago, BLS (Bureau of Labor Statistics). E = Ex-vessel price, weighted average for South Atlantic and Gulf states. The predetermined variables are [16, pp. 65-66]: Y = Landings per quarter in the South Atlantic and Gulf states in millions of pounds, heads-off weight. I = Imports per quarter, in millions of pounds, heads-off weight. 70 E ^^ = Ex-vp.ssel price lai^ged one quarter. B ^^ = Stocks held in cold storage at the beginning of the quarter. G = Quarterly total disposable income. Qo > Q-ij Qa ~ Quarterly intercept dummies for quarters twoj three, and four, respectively. 1 = The intercept dummy. The structural quarterly model for v^^hich Doll estimated parameters is composed of four equations. Wholesale demand (3.13) A^ = 3(^3)^ + 6(,3)2 ^2 + ^13)3 ^3 "^ ^13)4 % ■*■ ^13)5 ^t -^ ^13)6 ^ Price linkage (3.1A) D^ = B(,,), + E.f^ B(i,). Q. + B^,)3 E^_^ "^ ^(14)6 ^t + ^14)7 \ Ex-vessel demand ^''^'^ h = ^15)1 -^ htl ^15)i '^i ■" ^15)5 \ ^ ^15)6 ^t + ^15)7 ^t ■*■ ^15)8 Vl + ^15)9 \ Stock balance (3.16) B^ = 3(,,), + 3(,,)2 ^t + ^16)3 ^t "■ ^(16)4 Vl + ^(16)5 \ The difference in length of time interval between Doll's model and the time interval used in the rest of the model presented here raises the difficulty of obtaining quarterly landings with a model that requires prices for all time periods within the quarter except the last. This 71 difficulty may be partly overcome by using tht; prices determined in one quarter for all time periods occurring during the subsequent quarter. For example, if the shrimp and fleet models employ monthly time periods, then the prices determined at the end of the preceding quarter could be used in each month during the current quarter to generate catch. At the end of the current quarter, monthly catches may be totaled and used to generate a set of prices which are used for each month in the subsequent quarter. Thus, prices are constant for the entire quarter. However, if the number of tim.e periods per quarter is not large, this procedure nay give reasonable results. An alternative is to use a month corresponding to the moving average of prices obtained in a hypothetical quarter employing data from current, previous, and subsequent months in the preceding few years. Wiile this would allow shorter lags in the har- vesting sector and thus more immediate seasonal responses, it builds into the model an incapacity to react to extremely volatile conditions resulting from large inter-year price variation. A third alternative is to use quarterly data in the models of the harvesting sector and basic shrimp resource. This alternative may prove reasonable also. Choice of an alternative must rest upon empirical considerations. The problem of disaggregating the ex-vessel price into prices for each size class of shrimp is serious but a workable solution can be more readily proposed than for the time period problem. The price of a given size class of shrimp most likely depends on the relative abundance of the various-sized shrimp available in the market. Although imports and cold storage holdings influence the size composition of available shrimp, the relationship postulated here is between current landings and price. The price of a given size class of shrimp is postulated to 72 be a direct function of the aggregate price detenniTicci by equation (3.15) and an inverse function of the proportion of that size shrimp in total landings. That is: (^•1^) ^jnt = ^j = 2 P(17)3 Qj + ^17)8n ^ /\ ^o \ "*" ^(17)9 I y"T ~ Y~ J^t \ nt no y where the Q., j - 2, ..., 7 are dummies for areas II - VII; i.e., the equation is normalized on Area I , Y ., is landings of shrimp of size n (n = 1, ..., N different sizes) in time period t, Y is landings in time period t, P is the ex-vessel price derived from the quarterly ex-vessel price determined in (3.15), Y and Y are landings in some base period, and the B/-,-,xo are coefficients derived from the price spread between (17) on size classes in the base period. Equations (3.1) - (3.17) arc the relations needed to describe the dynamic workings of the Gulf of Mexico shrimp industry with the excep- tion noted in the model of the marketing and demand sector. In addition, modifications in the variables of the model of this sector to make them correspond more closely to conditions in the Gulf shrimp industry may be needed. Further refinement will be dictated by the estimation tech- niques and programming procedures involved in the application of a simulation model. CHAPTER IV METHODOLOGY AlU) DATA The objectives of this study, listed In Chapter I, nay be presented as a set of objectives relating to the behavior of individual firms and a set of objectives relating to industry behavior. The objectives relating to firms concern the description of the behavior of firms in the Gulf of Mexico shrimp industry in response to changes in the shrimp population, the technological conditions of harvesting and processing, and demand conditions. The objectives relating to the industry concern the behavior of the industry in th.e aggregate and particularly its response to management strategies. The management strategies or poli- cies to be considered are: (1) varying age of shrimp at first capture; (2) imposing an annual entry fee (license fee) on vessels in the industry; and (3) imposing a landings fee or tax per pound on shrimp landed by vessels in the industry. The procedure for attaining the objectives relating to industry behavior involved constructing a simulation model of the Gulf of Mexico shrimp industry that simulates the behavior of the industry under vari- ous conditions. The objectives relating to firm behavior were realized by drawing on published results of research into various phases of the industry and, where such results were not available, by resorting to synthesis of needed parameters. The major thrust of this study is to develop a bioeconomic theory of a fishery, to build an abstract model of the Gulf of Mexico shrimp industry based on this theory, and to 73 74 develop an empirical model that gives plausible results. Ther.? was v.o attempt to elaborate upon the objectives relating to indivxdurtl firm behavior as the emphasis ol" this study is to deteiTnine the effects on the industry of selected regulatory strategies. This chapter describes simulation as a tool for policy evaluation, the available data, and the computer r.odel employed in this simulation study. Si mujL a ti on as a Tool _f or_ Model Euildi ng and Policy Evaluation The dog trots freely in the street and sees reality and the things he sees are bigger than himself and the things he sees are his reality ["Dog," from Lawrence Ferlinghetti , A Coney Island of the Mind , Copyright 1958 by Lawrence Ferlinghetti, reprinted by permission of New Directions Publishing Corporation.] In order to describe simulation as a tool for evaluating manage- ment strategies, one must first define simulation. Simulation is not a well-defined technique in the sense that linear programming or regres- sion analysis are well-defined techniques. As is the case in most descriptions of simulation, several definitions are given and then a comprehensive definition is made for the purpose of this study. Describing simulation as a research method, Fred H. Tyner [31, p. 13] says: "Simulation Involves the application of logical reasoning to a scale model of selected real-world phenomena, whether the scale model be one of equations or the prototype of a physical plant." In a paper discussing the reasons for using simulation J. E. Creameans [13, p. 6] writes: "The best that one can say about any simulation model is that it describes the object process using those characteristics which are important to the results that the model builder wishes to study." 75 G. H. Orcutt [25, p. 893] furnishes an open-ended definition of siranla- tion: "Simulation is a general approacli to the study and Lise of models," Defining simuDation for the purposes of a paper, Boutwell and McMinimy [8, p. 1] say: "A matheiTiatical simulation model is defined as a model that traces a series of events through time and/or space in sucli a manner that the cost and benefit streams of the resulting time path are measured," In a Rand Corporation publication, M. A. Geisler [18, p. 1] gives a hint as to the birthplace of the term simulation: The study of large and complex systems in recent years, combined with the development of large-scale computers, has led to the representation of these systems in mathe- matical form for programming and calculation on high-speed computers. Calculations so obtained have been essentially pseudo-observations of these systems, which accounts to some extent for applying the term simulation to this technique. Jay W. Forrester [17, p. I'^i] j while dealing with industrial dynamics (which may be thought of as a specific type of simulation technique) , states: The first and most important foundation for industrial dynamics is the concept of servo-mechanisms (or information-feedback systems) as evolved during and after World War II. An information-feedback system exists whenever the environment leads to a decision that results in action which affects the environment and thereby influences future decisions. As can be seen from the above definitions, there is no general accord in defining simulation. However, there are commonalities in nearly all definitions of simulation. Most of the definitions indicate that systems with interacting components are involved and that the systems are dynamic as opposed to static. Simulation is defined, for the purposes of this study, to be a technique for studying the performance of dynamic systems whose 76 components intei"act to form an environmental sett-lng vjhich may change as a result of component interaction tlirougli timt-. A simulation model is an abstract representation of the system to be studii^d. It is usually, but not necessarily, formulated ii"i terms such that a coraputer may be used to trace out the interaction of the mode] components over time. The model components correspond more or less closely to their real system counterparts in a degree that serves best the purposes for which the study is being conducted. Further, as implied above, a system refers to a set of real-world components whose decisions in reaction to their environment either wholly or in large part determine their future environment. Simulation involves building a model of this real-world system and operating the model over time, observing its behavior which supposedly reflects that of the real system. At this point, legitimate questions arise. It is very well to be able to represent a system symbolically and even to have a machine manipulate these symbols to simulate the system's behavior, but what is to be gained from this? Cannot the real system be observed as easily as its machine-bound counterpart? To answer these questions is to specify the value of simulation as a research tool. If a system is relatively simple and well-understood and its behavior predictable without error, then there is no point in simulating the system since nothing is to be gained from such a simulation. However, many systems are not well-understood and/or their behavior not readily predicted. It is in studying these systems that simulation is of use. In many large and dynamic systems, the components of the system and the ways in which these components interact may not be readily identifiable. Building a simulation model of the system forces the researcher to (1) identify the various components of the system, 77 (2) specify how they interact, and (3) decide the relative importance of components and interactions to the behavior of the systeE. The test of the researcher's skill is the degree to which selected m.odel results approximate the behavior of the system. (VJhile it is possible that the model may behave correctly for the v.'rong reasons, this chance must be taken in lieu of a better validation.) The researcher may use all the conventional econometric analysis at his coraniand to identify the rela- tionships betv7een the components and the components themselves. Then, by fitting these relationships into a simulation framework, the researcher m.ay discover important areas of omission or misspecif ication. Thus, a value of the simulation technique is that it provides insight into the components and interactions of a system, i.e., how the system actually v/orks . Given that a system may be readily identified and that an accurate model may be devised, often the complexity of the system prevents accu- rate prediction of future behavior, especially if some component or relation of the system is changed. Using a simulation model, the system's behavior may be traced out through time under different sets of conditions (different levels or states of the policy variables). That is, if an accurate model of the system can be devised, then it will be possible to experiment on the model, gaining valuable (and often less costly) information about the probable effect of proposed manage- ment strategies on the system itself. Thus, a second value of simulation and the one of primary interest in this study is that it gives the researcher and his decision-making clientele an opportunity to test new management strategies on a realistic model without fear of a possibly disastrous result that could occur from testing on the system itself. 78 Thus, simulation is a research teclmiqiKi that has the. noteiit i al to provide valuable information about the system being naodeled and pof:sible effects of proposed policies affecting the system. A drawback to employing simulction as a research technique is that there currently exists no standardized method for evaluating, the reliability of the information provided by a simulation model. Lack of a standardized validation technique for simulation models may be partly due to the youth (relative to standard econometric methods) of simulation as a research technique. In addition, simulation models tend to be unique, problem-oriented models that m.ay not lend themselves v.-ell to standard- ized validation techniques. However, simulation has been defined for this study in a rather general sense and an attempt is made here to develop a general approach to the problem of model validation. For purposes of exposition, a situation is assumed involving an analyst employed by a client to provide information about the possible effects of proposed policies on selected indicators of the performance of some system. To provide this information, the analyst employs The terms "analyst" and "client" are used for convenience' sake. The "analyst" may actually be a group of investigators which may include all or a part of a group of individuals represented here by the term "client." The situation assumed here presupposes a "client" who recog- nizes a problem in a system for which he has authority to implement policies designed to correct that problem. In addition, the client is assumed to possess an array of alternative policies among which he will choose on the basis of information provided by the analyst. This is an idealistic situation. More likely, the "client" is likely to have con- fused and/or conflicting views about the problem and policies designed to correct it. In addition, as is the case in the present study, there may not exist a "client" with the ability to implement policies even after problems have been identified and corrective policies proposed. Alternatively, the analyst may not be able to conceive of or comprehend the system and/or the problems involved in a manner that leads to the generation of meaningful information. These problems are not unique to studies employing simulation as a research technique and represent needless complication to the framework to be developed here. 79 simulation modeling as his prii-nary resedrcb technique. Figure 4.1 presents a flow diarriram of a possible frainevork in which tlie sinulation model, as initially constructed by the analyst, may be subjected to progressively liio-re rigorous validation procedures. The model is refined by the analyst as a result cf the validation procedures and as a result of the assessment by the client and the analyst as to the usefulness of the information generated by the model. As the model becomes more refined and capable of providing information v.'orthy of r.iore confidence, so do the validation procedures become more sophisticated and capable of detecting less obvious aberrations in model performance. As represented in Figure 4.1, the validation process begins after initial construction of a model by the analyst. During the process of model construction the analyst may gain insights into the system that 2 prove to be valuable information to his client. The analyst and his client can evaluate this information in terms of its implications for model revision. In addition, the analyst may select model output quan- tities that he believes to be reliable indicators of system performance and compare the means, ranges, and standard deviations over the simula- tion period of these quantities with the means, ranges, and standard deviations of their real-world counterparts over some base period. Since the model parameters are usually estimated with data generated by the actual system for a period in which the system exhibited enough stability to survive, the model will likely prove stable if it is properly specified. Model stability is not a goal within itself, however. There may be inherent instabilities in the system that are 2 These insights may be the most valuable product of the entxre research effort. 80 1 4J 1 M c •H O >. QJ <-i U-l -n a O C Crt P. T3 •H •a w c 0) Q) CU CO it-l •a CO > O •H CO •H 4J > CO ■u c c o CO -i x) C •H •H p. c u iH /<— N 4J CO OJ O 4-1 CO c •w v^^ en 3 o iH rH > i-H •H a) CO en rH rt iJ 'C3 CO o <4-l •H C w e B o u CO d C •T3 1 x) O -H 0) (U c •H > >-l CO cn T3 o •o •H C Vj CO 0) c > CO Ou » -H U-l •H >-i iH fO 3 J2 4J O 4J CO V4 CO cn S C 4J 4-1 a C 0) o CO CO C -H o u s-x c 0) >+-l •H >j ■4-t o B -H 4J QJ CO o 0) o CO 4J tiO 4-1 > Q) U •t— 'C3 P- V4 V4 iH o O 6 >4-l o CO d !-i S tH o CJ ft CO P CO 0) ;-! -a CU a o , cn CO Q) C > CO iH --' 4J (U iH t3 iH 3 j:: cjo CO •H O ft 4-1 C 3 rH > 4J O 4J CO C 3 >. B o t» -H O ^ CO CO 0) J5 4-) c U-i o O •H 4-1 CO CD CO CO (U -o CU m •H o CO r-t o j= CO >^ Pl< > a r 4J 1 CO 1 o >^ •H 3 iH CO C V-i 1 CO 4-1 •H 4J o C jn B tn M CO (50 0) ^ C ft •H 4J 00 o % O o 4J •H cn m ■H •H ^ dJ 4J >> c Q) 4-1 T3 CO JO o j^ O 01 n P4 0) s ti o ■H T3 4-) Q) CO > iH iH 3 O S > •H d C/2 •H M-l CO o 0) c 4-) o Vl •H CO 4J ft CO T3 (U •H ,c .H 4-1 CO > (U 4J !-l CO O o 4-1 ■H -3 Ai c i-J •H o s 60 OJ C •H T3 !-i CO [J:4 0) J3 CO 0) 4-1 Jl o 4-1 >— \ c c >^ o •H 4J •H •H U CO > CO tu •H 4-1 CO 4-1 c (U o (U .c CO CO 4-1 c rH o O •H > 4J c CO •H T3 •H cn .H 4-> U CO o P- U-l 0) v^ t-^ r*-* u 4J o s 0) a) 4-1 a CO CO o u •H fe c CO •H iw 00 o C •H c TS o CO •H 0) JJ x: TJ CO 0) 4J 0) 3 c X d (U 4-1 •H en 4J . U 4-1 4-1 CO c •H e Q) > 0) ^4 •H x; CO 4-1 CJ Pli O CO >*• CO 0) 3> 0) 10 cd (U CD CO Pli 82 isolated as a result of model construction or that the model must cap- ture in order to provide information on policies designed to eliminate the instabilities. The comparisons involved in Phase I of the valida- tion process are not of the t3'pe that lend credibility to irformation provided by the model. They merely provide crude indicators of the performance of the model and, together with the information provided by the interaction of analyst and client, provide input into the process of revising the initial model. Phase II of the validation process involves experimenting with the model to determine the type of policy information the model provides. This information, after evaluation by the analyst and his client, may indicate needed model revisions. In addition, the analyst may compute simple correlation coefficients between selected indicators of the per- formance of the model. These coefficients, together with a graphic analysis of selected model quantities, serve to indicate relative direction of serial movement between model quantities. The relative movements of model quantities over time can be compared with expecta- tions based on theory as well as the relative movements of actual quantities over time. These comparisons together with the information provided by analyst-client interaction provide the basis for further revision of the model and comprise Phase II of the validation process. The revised model is used to provide information to the client which the analyst and client assess for implications for further model revi- sion. In addition, values generated by the model for selected aggregated (over time or variable subsets) output quantities may be subjected to spectral analysis. The resultant time path parameters relating to trend as well as amplititude, frequency, and phase angle of cycles may be 83 compared with those resulting from spectral analysis of actual data. The information thus provided by Phase III of the validation process may be used to direct further revision of the model. Phase IV of the validation process involves considering model- generated values of dis- aggregated output quantities produced by the model after its revision at the end of Phase III. These quantities may be analyzed by graphic methods and calculation of simple correlation coefficients as in Phase II or by spectral analysis as in Phase III or both. The results of this procedure, together with the information obtained through analyst-client interaction may be used to attain a fourth level of revision of the model. The framework for model validation presented here may be modified or extended to meet the needs of a particular situation. At each phase in the validation process the client receives information from the model through the analyst. On the completion of any phase (possibly even before Phase I begins) the client may decide he has enough infor- mation. The analyst and his client may choose to cease revising the model after any phase of the validation process, considering any increase in model reliability not worth the cost of the required model revision and validation. The analyst may be hindered in his validation procedures by the absence of actual time series data on variables of interest with which to compare model results. Thus, it becomes clear that the process of model construction, revision, validation, and use remains as much an art as it is a science. Even within the framework presented here, the analyst must effectively allocate his resources (presumed to be scarce) between model "validation" and model revision and maintain a balance between the sophistication of his validation procedures and the level of development of his model. Data Models that represent complex systems make stringent demands on the data. In the case of the GuJf of Mexico shrimp industry data in the form of parameter estimates that can be used directly in building a model of the industry do not exist for many of those needed. Those parameters that could not be adapted from published literature were synthesized from available data using basic sLatistical techniques. Estimates of the parameters describing the behavior of the Gulf shrimp resource were derived from estimates made by Berry [7]. The work of John Doll [16] provided most of the parameter estimates for the marketing and demand sector of the model were synthesized from primary data published in Osterbind and Pantier [27], Lassiter [22], Lyles [23, for the years 1965 and 1966], Osborn et al. [26], Surdi and Whittaker [30], and Arnold [5] A model of the Gulf shrimp resource requires an individual growth equation and a survival equation which incorporates estimates of natural mortality and mortality due to fishing. Equations (4.1) and (4.1a), derived from equations given by Berry [7, p. 127] are the growth (in weight) equations for male and female pink shrimp, respectively, on the Dry Tortugas grounds utilizing a monthly time period. These equations are used in this study to represent weight in grams of individual shrimp of brown, white, and pink species on all grounds. f/ T^ „ , , . ,„ - r -.1992(t + 1.062)1 3.134 (4.1) W (males) = 42.3 |1 - e J f, , s ,, fr: 1 X TO o F-, -.2382(t - .2633)1 3.115 (4.1a) W (females) = 73.3 Ll - e J The time variable, t, is measured in months of 4.33 weeks each from time of hatching (zero age of shrimp). By multiplying equations (4.1) and (4.1a) by factors to convert to heads-off weight, convert from grams to 85 pounds, and taking the reciprocals of the results, the number of shrimp per pound at a given age may be determined. Factors to convert heads-on to heads-off weight are (as derived from E. J. Barry [6, p. XVL]) for brown shrimp, C,S21; pink shrimp, 0.625; and white shrimp, 0.649. The size classification of shrimp considered are: (1) very small, over 55 tails per pound; (2) small, 41-65 tails per pound; (3) medium, 26-40 tails per pound; and (4) large, 25 and under tails per pound. Table 4.1 gives the age, in months, of male and female shrimp in the four size categories. Shrimp are assumed to become subject to capture at three months of age. The variation in heads-on to heads-off weight conversion factors made no difference between species in these gross size categories. The survival equation used in this study is of the form specified in equation (3.2). The natural mortality coefficient, M, is not differ- entiated by species, time, or area and the initial value used was 0.22 [7, p. 88]. Fishing mortality (F ) was related to effort (in standard- ized 24-hour days fished -X. ) by area and time as shown by equation (4.2). (4.2) F.^ = b.X.^ Initial estimates of the b.'s were derived for each area from the b J value given by Berry [7, p. 88] of 11 x 10~ by multiplying by 1125 and dividing by the square nautical miles fished in the area (as estimated from maps presented in [26]) to convert to an equivalent area basis and multiplying by 24 to convert to an equivalent time basis. The initial estimates of the b.'s and the estimated area fished in square nautical miles in each area are given in Table 4.2 for each statistical area. Standardized days fished are derived from reported 24-hour days fished 86 Table 4.1. Age (in inonths o£ 4.33 vje.eks each) distribution by size and sex of brown, pink, and white shrimp in the Gulf of Mexico Size Category (tails/pound) 1) over 65 2) 41 - 65 3) 26 - 40 4) 25 and under Males 3 through 4 inonths 5 through 6 months 7 through 9 months 10 months and over Age Females 3 months 4 months 5 through 6 months 7 months and over 87 Table 4.2. Coefficients to convert 2'-';-hour days fished to fishing mortality and estimated square nautical miles fished by area Estimated square nautical Area j b miles fished '■■■■■ - . - J I 1.13 X 10"^ 26,185.50 II 2.26 X 10~^ 13,092.75 III 2.50 X 10"^ 11,902.50 IV 1.19 X 10~^ 24,995.25 V 1.25 X 10"^ 23,805.00 VI 3.12 X 10"^ 9,522.00 VII 0.92 X 10"^ 32,136.75 88 per vessel size class by multiplying days fished by each vessel size class by the estimated sweep capacity per vessel in hundreds of feet. The vessel size classes used and their sweep capacity in hundreds of feet are given ia Table 4.3. The computer model calculates number of recruits each month by adding to the mean recruits each month the product of a normally dis- tributed random number with zero mean and variance of one and the standard deviation of recruits in that month. The estimated means and standard deviations of recruits for species in each month in each area are presented in Appendix II in the data required for initialization of the simulation program. Appendix I presents the computer program and data required to estimate recruits by species by month and area. The model of the harvesting sector — the fleet — of the Gulf of Mexico shrimp Industry is required to generate 24-hour days fished by vessels in each size class in each area. To do this, the computer program adjusts average days fished per month by a vessel of a given size class in a given area by a factor depending on net revenue in the preceding month. Adjusted average days fished per vessel is then multiplied by the number of vessels in that size class fishing in the given area. Adjusted days fished by vessels of all size classes are then standardized by multiplying by vessel size class sweep capacity in hundreds of feet and added together to determine 24-hour days fished in that area. Table 4.4, adapted from tables by Lassiter [22, pp. 40-46], presents estimates of the average 24-hour days fished by a vessel in each size class in each month of the year. Table 4.5 gives the adjustment fac- tors by which the data in Table 4.4 are adjusted to arrive at average 24-hour days fished per month by a vessel in each size class in each area in each month of the year. These factors are based on the ratio 89 Table 4.3. Vessel size classes and sweep capacity of nets along headropc in hundreds of feet Vessel size class Gross register tonnage Sweep capacity 100 feet 1 less than 5 .375 2 5-19 .500 3 20-49 ,800 4 50-79 1.000 5 80 and over 1.250 90 Table 4.4. Mean 24-hour days fished per month by a vessel in each size class Vessel size class Month 1^ 2 3 4 5 January 1.0 2.9 4.2 5.4 4.9 February 0.5 2.7 3.7 5.9 5.0 March 0.5 3.2 4.6 6.6 7.9 April 0.5 2.7 4.1 6.5 5.2 May 1.0 3.2 4.5 7.2 6.8 June 1.0 4.9 5.4 6.7 6.7 July 0.75 5.8 6.4 7.4 7.1 Augus t 1.5 5.2 6.5 7.7 7.0 September 2.5 4.5 5.3 6.9 7.2 October 3.0 5.5 6.2 7.2 7.3 November 3.0 3.8 5.0 6.3 6.3 December 2.0 2.7 4.2 6.5 6.4 Estimated from closed seasons in 1969, personal knowledge, and the distribution of white shrimp landings as given in [26]. 91 Table 4.5. Factors to adjust days fished by a vessel in a size class to reflect variations in average days fished by vessels in different areas Area Adjustn.ent factor I 1.15 II .83 III -73 IV .83 V 1.13 VI 1.13 VII 1.15 92 of the average days f i shed per year by vessels in an area to the average days fished per year by vessels in all areas. The number of vessels estimated to have hone ports in each area is given in Table 4.6, along with the number of vassels assumed to be fishing in each area in December of a typical year. The latter figures are needed to initialize the simulation model. The model of the marketing sector employs a quarterly time inter- val. Given catch for the quarter, this model calculates ex-vessel price as well as consumption, ending stocks in cold storage, and whole- sale price. The calculated ex-vessel price is used to determine the ex-vessel prices used in the model of the harvesting sector for each month in the succeeding quarter. The model of the marketing sector is based on the quarterly model estimated by Doll [16] and the reduced form coefficients of Doll's model are presented in Table 4.7 for the variables as identified in Chapter III. In addition, Doll [16, p. 104] 3 presents an import equation that is employed here. The equation is given as (4.3) using the same variable defined as in Chapter III. (4.3) I^ = -9.212 - 0.1952Y^_^ - 8.4988Q2 In order to be consistent with the model of the harvesting sector, the ex-vessel price computed with the parameters presented in Table 4.7 is converted to ex-vessel prices for each size class of shrimp and further 3 There is an exception. Doll [16, p. 104] reports the coefficient of Q- in equation (4.3) as -88.4988. Use of this value, holding Y and G at mean values, produced negative imports which did not occur in the data he reported using. Since imports were nearly the same in the second and third quarters in this data [16, pp. 98-99], the value of -8.4988 was used as the coefficient for Q^ , approximating the coeffi- cient of Q_, and reflecting the assumption of an error in the reported coefficient. 93 Table 4.6. Number of vessels in each size class estimated to have home ports in each area and number of vessels in each size class assumed to be fishing in each area in December of a typical year Vessels estimated to have home ports : each area by vessel size class Ln Area 1 2 3 4 5 I 0 7 170 191 41 II 98 101 52 21 3 III 582 158 242 110 29 IV 3 ,257 233 347 283 46 V 860 135 251 429 93 Vessels December assumed of a typ to bf ical 2 fishing year by ; in each area in vessel size class Area 1 2 3 4 5 I 0 7 170 291 61 II 98 101 52 21 3 III 582 158 242 110 14 IV 3 ,257 233 347 283 26 V 860 135 251 229 23 VI 0 0 0 100 10 VII 0 0 0 0 75 94 o X) 0) 3 (4 rH en <-{ •H )-l > -a 60 W 1 1 •H 01 o pq VJ 4J • • • • ^ " CO 1 Cu W o CT. o o 4-J 0) h-5 X CO CM CJ 0) 1 >4H o •H > CO 00 CM CM rH U) i to P-M • • • • rH TJ >-' • • • • Q) 0) c o o o o e c ca 1 1 o •H 1-4 c o o CO 4-1 w a. VO <3- t^ 00 •-i iH M o o • 4J c iH rH &< CO M 1 John ch, N 4-1 4J M 'V 1 •» cO rH (U 0) 0) i-i CO XI CO 4-1 u o O 0) >% 0) 0) < 4J •H •H O pS rH C -H 1 « V4 u 4J -H J3 fi 1 CM PU o C 6 CO •H S -H O CO •• -H •^^ ^ dJ r^ -) 4J CO P. o CO (0 M C 0) > a 4-1 eo CO 3 O x> 5 w (U 0) O O en rH > CO w C X) o 1 O u c w g 14H O 95 adjusted to reflect variations in the proportion of total catch that each size class represents. The Computer Program The model was reduced to a computer program using the Fortran IV Level E language designed for the IBM System/360 [21]. The program and initialization data are presented in Appendix II. Figure 4.1 is a flow chart of the essential workings of the program, denoting input and out- put of the main program and the subroutines. 96 >. u 4J (C y TD • C t-> M X. 60 CU-H 6 >^ •H Vj O J= +J w +J o D-l o 0) •H rH « 0) a s o vj y-i 14-1 o n y-i OJ iH •T3 3 S-i O o 0) c JS •H AJ W >4-l 0) o C -H ■H J-) 0) 3 •a O o i-J S ^ 3 j-i 0] 'kCJ. 4, ,00 4. .00 2, ,00 1, ,75 1. .75 1, .00 3, .00 I 4.93 X 10~^ II 9.85 X 10~^ III 7.26 X 10"^ IV 3.31 X 10"^ V 3.49 X 10~^ VI 9.08 X 10"^ VII 5.81 X 10~^ 100 the intercept value used from the -9.212 presented in equation (4.3) to the value -19.212 used in the model as presented in Appendix II. No further adjustments in the model parameters were made as a result of Phase I validation procedures. Phase I comparisons based on output from the model as presented in Appendix II are given below. Surdi and Whittaker [30, p. 7] report annual Gulf shrimp landings from 1960 to 1970. During this period landings varied from a low of 79.6 million pounds (heads-off weight) in 1961 to a high of 145.2 million pounds (heads-off weight) in 1970 with average annual landings for the period 1960-1970 at 119.1 million pounds. The model listed in Appendix II, using the initialization data listed there, generated annual landings values ranging from a low of 93.6 million pounds to a high of 113.9 million pounds with an annual average of 104.4 million pounds and a standard deviation of 5.0 million pounds. Thus, the model generates landings in the ranges of actual landings occurring during the decade of the 1960's; however, model landings show more stability. Average generated landings were below average actual landings during the 1960 's by 14.7 million pounds per year for an average percentage error of 12.3 percent per year. This discrepancy may result from low estimates of mortality, shrimp recruits, or both. It may also result from the intra-year cyclical patterns of shrimp abundance by area and effort allocation being out of phase in the model as compared with the real world and may be altered during later revision. Table 5.2 presents information on the size composition of actual catches in the Gulf and South Atlantic states from 1964 through 1970 and the average composition of 30 years of catches generated by the computer model. While the size classifications used in the model 101 Table 5.2. Size composition of actual shrimp caiches in the Gu]f and South Atlantic states for the years 1964-1970 and average size composition of 30 years catch data generated by the computer model Percent of actual catch Year Large Medium Small (30 & under tails/lb.) (31-50 tails/lb.) (over 50 tails /lb.) 1964 1965 1966 1967 1968 1969 1970 39.5 35.3 36.8 37.8 34.7 32.9 36.3 35.8 35.9 31.1 34.8 33.3 31.7 30.3 24.7 28:8 32.1 27.4 32.0 35.4 33.4 Mean 36.2 33.3 30.5 Standard Deviation 2.15 2.30 3.73 Percent of average catches generated by the computer model Large (25 & over tails/lb.) Medium (26-40 tails/lb.) Small (41-65 tails/lb.) Very small (over 65 tails/lb.) Mean 27.9 29.8 21.7 20.6 Standard Deviation 1.31 1.71 1.48 1.56 Mean Large Medium Small (30 & under tails/lb.) (31-50 tails/lb.) (over 50 tails/lb.) 37.9 28.5 33.6 Calculated from catches generated by the model on the assumption that catches in the medium (26-40) and small (41-65) categories are uniformly distributed over the five tails/lb. intervals making up these classifi- cations. 102 am not the same as those reported by Surdi and Wiittaker [30, p. 8], the data in Table 5.2 indicate that the shrimp catches generated by the computer model have a similar si?.e composition to that of actual catches. Surdi and Whittaker [30, p. 16] report ex-vessel prices occurring for brown, white, and pink shrimp at Brov^msville-Port Isabel, Texas, Morgan City, Louisiana, and Tampa, Florida, respectively, for each month of the years 19G9 and 1970 for three sizes of shrimp. There are thus 72 observations on prices for each size of shrimp. The ex-vessel price for 15 - 20 tails per pound count shrimp ranged from a low of $1.07 per pound to a high of $1.48 per pound. Prices for large shrimp generated by the computer model fell within this range. The ex-vessel price for shrimp counting 31 - 35 tails per pound ranged from a low of $0.75 per pound to a high of $1.10 per pound, a range which contained the prices generated for medium shrimp as defined in the model. The prices for shrimp counting 51 - 65 tails per pound ranged from a low of $0.41 per pound to a high of $0.77 per pound. The prices generated by the model for small shrimp were generally near the top of this range while the prices for very small shrimp concentrated near the bottom of the range. As with landings, model prices showed somewhat more stabil- ity than real-world prices. The computer model generated average imports of 180.3 million pounds (heads-off weight) per year with a standard deviation of 0.8 million pounds. About 23 percent of the imports occurred in the first quarter, about 20 percent in each of the next two quarters with about 37 percent of the imports entering the country in the last quarter. Thus, generated imports were slightly lower than the average annual 103 imports of 182.1 million pounds per year reported by Surdi and Whitr.akor [30, p. 12] for the years 1960-1570. The above comparisons of means and standard deviations of model quantities with actual data for the 1950 's indicate that the model as presented in Appendix II did not explode; it reproduced values within the ranges established from actual data. The comparisons of Phases II through IV of the validation framework presented in Chapter IV are intended to provide indications of the underlying economic relationships contained in the model. Relative movements in selected model quantities are presented below. In the present model total personal disposable income is held con- stant, thus eliminating shifts in demand due to population and/or productivity effects. In addition, to the extent that personal dispos- able income is correlated with time (as it was in Doll's data [16, pp. 29, 97]), holding this variable constant removes any trend in demand. Thus, the movements in values generated by the model reflect variations in shrimp supply resulting from resource availability and effort variability. Figure 5.1 presents the values generated over a 30-year time period by the model for average wholesale and ex-vessel prices, total landings, imports, and effort in adjusted days fished. Figure 5.2 presents the values generated by the model for total produc- tion costs, adjusted days fished, value of the fleet assuming a five- year investment life, and net return (ex-vessel value of the catch less total production costs). Table 5.3 presents simple correlation coeffi- cients for the variables presented in Figures 5.1 and 5.2 plus ex-vessel value of the catch. These comparisons correspond to those indicated in Phase II of the validation framework described in Chapter IV. As indi- cated in Figure 5.1 and Table 5.3, wholesale and ex-vessel prices 104 185- 180- 175- 170- 165- 160- 155- 150- 145- 140- 135- 130- 125- 120- 115- 110- 105- lOO- 95' 90- 85 Imports (mil. of lb.) Adjusted Days Fished (2,000 days) Wholesale Prices (cents per lb.) T — t—r 5 T— I — r— 1 10 I I I I I I I 1 I I I rill 15 20 25 30 Total f \ / Landings V (mil. of lb.) Ex-vessel Prices (cents per lb.) Figure 5.1. Annual Values Generated by the Computer Model for Wholesale and Ex-vessel Prices, Total Landings, Imports, and Effort in Adjusted Days Fished 105 255 - 245 I 235 225 205 200 -i 195 185 165 _ 155 - 135 - 125 115 _ 105- Value of the Fleet (nil. of dollars) Adjusted Days Fished ...xN.^^, (2,000 days) Total Production Costs (mil. of dollars) ■15 _ -25- -35 -45-1 I I I I 1 I I I I I I I 5 10 I I I I I I I I I 15 20 rTT TT 25 TT Net Return (mil. of dollars) m 30 Time in Years Figure 5.2. Annual Values Generated by the Computer Model for Total Production Costs, Adjusted Days Fished, Value of the Fleet Assuming a Fixed Year Investment Life and Net Return (ex-vessel value of the catch less total production cost). 106 Table 5.3. Simple correlation coefficicnLs between selected variables based on values generated by the computer model Net Total Ex-vessel value return landings of the catch Total Production Costs -0.923 Value of the Fleet (5-yr. investment life) -0.809 a Adjusted Days Fished -0.950 0.847 Wholesale Price a -0.093 Ex-vessel Price a -0.380 Imports a -0.774 Net Return 1.0 -0.689 0.577 Not calculated. 107 generally move in directjons opposite to that for total landings con- sistent with the predictions of demand theory (increasing quantities supplied results in lower prices). The relationship betvjeen landings and prices was moderated somewhat by the negative correlation between total landings and imports and the dependence, in the model, of prices on total supplies (landings plus imports). Total landings and adjusted days fished (effort) are positively correlated. This result is con- sistent with production theory for stages I and II of the classical production function. The data presented in Table 5.3 and depicted in Figure 5.3 indicate that net return is negatively correlated with total production costs, value of investment in the fleet, and adjusted days fished. These comparisons indicate that effort and investment in the fleet are in excess of the levels needed for maximization of net return. The positive correlation between adjusted days fished and ex-vessel value of the catch suggests that the point of decreasing total returns to effort has not been reached. Tables 5.4 and 5.5 present data on the intra-year cyclical alloca- tion of vessels among areas by the computer model. Comparisons of these data with the data presented by Lassiter [22, p. 34] correspond to the types of comparisons outlined as part of Phase IV of the validation framework presented in Chapter IV. Lassiter [22, p. 34] presents infor- mation on the percentage of total monthly activity spent in each area by a sample of otter trawl shrimp vessels for the years 1959, 1960, and 1961. Since the computer model allows vessels to fish in only one area per month, the number of vessels fishing in an area expressed as a per- centage of vessels fishing in all areas is a measure of the effort spent in that area. Boats (vessel size class one) do not readily migrate between areas in the real world and were not allowed to migrate in the 108 c 0) 0) M m CO C 0) O 3 •H r-l cd > Q) r-i Vj di >-l w O CO O 0) 1 iH X P< Wl w c 0) 0) o & 4-> ^ QJ w M «v c < o •H x) •U c rt cd iH -i 3 o •u C.3 a) P^i lU iH •u eu 01 a Z CA M-f 1 I i i I I I c o (U (0 « & p^ 4-1 d) n pq W C " O Q •H 4-1 X) CO C r-l CO 0) j-4 cn M bc o C U -H -a Q) c rM CO p-hJ B •H .H m CO CO CO u • O H I 1 I I I I I I I i -f-H- +-M- i„ t-h-J w o •o » nj V C "3 QJ H CO 3 13 CO en AJ QJ PQ 4-1 ID 0) OJ 4-> ^ U CO 0) •H iH <4-l OJ 0) QJ o o W ,H CO T-l -H QJ >. ^J J-I c -c CO CU (X QJ O T3 QJ S 0) iH s TJ M 0) •i-l H 0) CO CO QJ Q) 4-) 0) CO PQ 4-) 03 Q) (1) 3 3 ■H > CO a •>-) O 1 w e ■X! 5 w C O <; QJ O •H II II II O QJ •H ^ Q W li* U-l 4-1 QJ t^ ^-s O ^ 0) (^ U-l X) •H C QJ iH O 4-1 •H CO 4J 4-1 !-i c CO QJ (U . .-H C 6 QJ Q) 4J u a CO t-i 0) O CO > CJ QJ c 3 •H QJ iH to .H CO U-) 4-1 • a-> CT» CO U X) e • O >. Q) •H C 1 CJ 1 rC LO CO CO o C ^-^ -H o M-l • •H 4-t n 4J 0) tn • O OJ >, in 3 iH CO TJ 14-1 -d QJ O u S-i <4-l XI 3 a. O 0) OO 4-1 •H iH QJ CO fn CO 3 3 j-i rH -t-) ■1 o CO X) ^ H > <: I I I I I I I < I I II II II <; pq u OCTiCJO r~.>^ u-iv3-rocN4 T-HCNm •u o CO to c o en to CO 4.) c a) !-i (1) M-l U rH m 00 Q) CO 4-> 3 iH cw CO O > Q) 60 3 C iH -H CO CO > 3 m OJ 0) IW bO o CO o Mr-t u !-( (^ Q) C (U Q (U CO o ^ •H cn 3 > CD 4-) B en rH CO 60 cn 3 0) to > -o T) O UJ c 3 U-l CO OJ S-1 to CO o OJ £50 CO 3 4-1 to t) o iJ Q) .H >H > 1.1 #\ ^ CO in CO > o CO o S-i o CO r. Q) 00 >. o^ OJ 00 00 o ** CO • o u o iH 0) M «;J- > ! CO G) OO C3\ (1) r~. •* -H -ra • m >4H 3 ^o r~ CO CM QJ ^ -H 4J 0) tn iw tn O 0) > 0) o 3 tn o rH i-i o CO to «v > 0) o\ >^ o •» • m m o •CO- CO H O o tn -3- ■<1- tn <• CO rH 3 cn •3 to 3 tn -a to 3 > ptl > CM iH 00 > CM rH CM •H (3^ •H tn 0) rH -H to OJ -a- 116 an efficient, zero-profit manner arc specified as theoretical aggregates in Chapter II. These charges correspond to the landings fee and vessel entry charges considered here. In addition, the regulating agencies of the various states involved in the Gulf shrirap fishery pursue some management policies, including closed areas, closed seasons, and gear regulations, designed to increase the age (size) at v/hich shrimp first became subject to capture. The specific policies considered here (based on Tullock's discussion, the development in Chapter II, and current practices) are: 1. No controls; 2. A set of policies possibly including closed seasons, closed areas, and gear regulations designed to increase the age at which shrimp begin to enter the catch (called simply, age at first capture) from three months to four months; 3. An annual vessel entry fee, by vessel size class of: vessel size class (CRT) less than 5 5-19 20-49 50-79 80 & over annual entry fee ($) 750 1,000 1,600 2,000 2,500 4. A per pound landings tax of $0.10 on all shrimp sizes. (Viewed as a percentage of ex-vessel price, this tax is relatively higher on the smaller sizes of shrimp which command lower prices.); and 5. A combination of the vessel entry fee charges in (3.) and the per pound landings tax described in (4.). The $0.10 per pound landings tax was arbitrarily chosen. The annual vessel entry fees were derived from an arbitrarily chosen fee for vessel size class four of $2,000 per year by multiplying this fee by the average sweep capacity per vessel. The rationale for this adjustment 117 is that, in order not to discriminate araong vessels on the basis of productivity, the annual vessel entry fee should be based on a measure of vessel productivity. The most convenient measure of vessel produc- tivity available during the present study was vessel sweep capacity by size class. The computer model was used to simulate the behavior of the Gulf shrimp industry over five-year time periods for the five different settings of the policy variables. Table 5.8 presents the levels of the policy variables and the associated average annual values generated by the computer model for the total catch, wholesale value of the catch, ex-vessel value of the catch, total production costs, revenue to the control authority (the authority imposing the policies and collecting the fees), the difference between total production costs and ex-vessel value of the catch (which may be considered a net return to fixed investment if all variable costs, specifically labor costs, are consid- ered to be covered) , and the value of fixed investment in the fleet under the assumption of a five-year average life of vessels and gear. Table 5.9 presents the rate of return to investment represented by the net return and value of investment figures in Table 5.8 for each of the policy levels. The revenue collected by the control authority may be considered a return to the shrimp resource. The disposition of this return and the welfare implications of alternative dispositions of this return are beyond the scope of the present study. However, the figures presented in Table 5.10 make possible some interesting comparisons. Table 5.10 presents the changes, occasioned by instituting the policy variables, in the quantities listed in Table 5.8 from the situation of no controls. In addition. Table 5.10 presents the sum of the revenue to the control authority and the changes in wholesale value and net 118 Table 5.8. Average annual returns from the Gulf shrimp catch, costs to the industry and fixed investment ?Ln the industry assuming a five-year investment life under various settings of the policy variables Policy . a settings Total catch Wholesale value Ex-vessel value 1 96,498,298 lbs. $136,067,890 $95,391,740 2 96,498,224 lbs. 136,067,840 95,391,680 3 94,303,328 lbs. 133,811,552 94,883,072 4 92,724,624 lbs. 132,358,080 88,322,608 5 92,199,424 lbs. 131,798,112 87,940,096 Policy . ■' a settings Total prod, costs Rev. to cont. auth. Net return Value of investment 1 $114,826,888 $ 0 $-19,435,148 $237,633,000 2 114,826,800 0 -19,435,120 237,633,000 3 119,989,504 8, ,694 ,105 -25,106,432 217,833,000 4 102,985,264 9, ,272 ,454 -14,662,656 205,431,000 5 11,158,576 17, ,748 ,080 -23,218,480 205,431,000 Tlefer to text, page 116, 119 Table 5,9. Rate of return to fixed Investment in the Gulf shrimp fleet under various settings of the policy variables Policy settings Percentage rate of return 1 - 8.18 2 - 8.18 3 -11.53 4 - 7.14 3 -11.30 a,. See text, page 116. 120 Table 3.10. Changes in average annual returns, costs, r.nd investment occasioned by the imposition of controls Chang es in: Policy settings Total catch Wholesale value Ex-vessel value Total prod, costs 1 0 lbs. $ 0 $ 0 $ 0 2 -74 lbs. -50 -60 -88 3 -2,194,970 lbs. -2,256,338 -508,668 -5,162,616 4 -3,773,600 lbs. -3,709,810 -7,069,132 -11,841,624 5 -4,298,874 lbs. -4,269,778 -7,451,644 -3,668,312 Revenue to cont. Changes in: Rev. to cont. auth. authority plus changes in Policy settings Net return Value of investment wholesale value and net return 1 $ 0 $ 0 $ 0 $ 0 2 28 0 0 -22 3 -5,671,281 -19,800,000 8,694,105 766,486 4 4,772,492 -32,202,000 9,272,454 10,335,136 5 -3,783,332 -32,202,000 17,748,080 9,694,970 ^See text, page 116. 121 return (which reflect the difference between changes in ex-vessel value and production cost). This sum is a measure of what is left over from revenue to the control authority after adding any changes in wholesale and ex-vessel values of the catch and deducting any changes in the cost of producing the catch. Thus, it is a measure of the net money returns obtained from instituting a particular policy exclusive of the cost of implementing the policy. It is what is left (after compensating all losers and taxing away all gains) to apply to the cost of implementing the policy. Increasing the age of shrimp at first capture to four months has essentially no effect on the quantities considered in Tables 5.8 and 5.10. Imposing an annual vessel entry fee, differentiated by size class as shown in Table 5.8, reduces total catch, the wholesale and ex- vessel values of the catch, and the net return. This policy increases total production costs and revenue to the control authority. The vessel entry fee policy considered produces a surplus after revenue to the control authority is adjusted for changes in wholesale value and net return although this surplus is probably not large enough to implement the policy. Imposing a landings tax on shrimp decreases wholesale value but increases net return since production costs are decreased more than the ex-vessel value of the catch. Thus, the revenue to the control authority, after being adjusted for changes in wholesale value and net returns, is significant, amounting to 11.7 percent of the ex-vessel value of the catch. Imposing both a vessel entry fee and a landings tax produces the greatest gross revenue to the control authority but a slightly smaller adjusted revenue than a landings tax alone due to the larger decline in wholesale value of the catch and a decline in net return rather than an increase. "Both the entry fee and landings tax 122 policies reduce investment in the fleet although when the polirieL; tire used singly the landings tax policy seems to more effectively reduce investment. Policy Implications Considering the relatively primitive nature of the model used to obtain the results presented here, caution must be used in drawing implications about the various regulatory measures considered on the basis of those results. In addition, different conclusions may be drawn as to the relative desirability of a proposed regulatory policy depending on whether one takes the point of view of the consumer, the vessel owners, the vessel crew, or processors. The benefit to society of a policy will vary depending upon the segment of society that the individual estimating the benefit is most closely associated with. Such conflicts seem to be inevitable and the approach taken here is to rank the policies on their effectiveness in attaining several alternative objectives. The assumption is made that all the policies are equally costly to implement with the exception of the policy of no controls, which may be implemented at zero administrative cost. No estimates of implementation costs have been made. If the revenue to the control authority is considered to be a return to the resource and the objective of maximizing this return is assumed, then the results presented in Tables 5.8 and 5.10 indicate that a com- bination of the entry fee and the landings tax policies is most effective in obtaining this objective. The landings tax policy ranks second in effectiveness. The vessel entry fee policy ranks third. The other policies give no return to the control authority. Since implementation costs are unknown, the net effects of the landings tax and vessel entry 123 fee policies cannot be determined and they cannot be compared on a ''net" basis with the costless alternative of no controls. The policy relating to age at first capture, since it produces no revenue to the control authority and has positive implementation costs, is clearly inferior to the alternative of no controls on the basis of maximizing returns to the resource. If maximization of net return to investment in the Gulf of Mexico shrimp fleet is taken as the objective and policy implementation costs are ignored, then based on the results presented in Table 5.8, a tax on landings seems to be the most effective means of attaining this objec- tive. The policy relating to age at first capture ranks second while a policy of no controls ranks a very close third. A combination of entry fees and a landings tax ranks fourth in effectiveness. Imposition of entry fees alone is the least desirable policy for attaining the objec- tive of maximization of net revenue to the fleet. If maximization of the total catch is taken as the objective, a policy of no controls is most effective. Regulating age at first cap- ture ranks second while an entry fee, landings tax, and combination of the two rank third, fourth, and fifth, respectively. If the objective of industry regulation is to reduce the value of investment in the Gulf of Mexico shrimp fleet, the per pound landings tax policy and a combination of the landings tax and entry fee policies are equally effective in reducing total investment. The entry fee used alone is the next most effective policy while the age at first capture and no controls policies do not reduce investment in the fleet. Table 5.11 contains the total production costs incurred by the fleet per pound of shrimp produced under the different policies. If the objective of regulation is to minimize per pound product cost by 124 Table 5.11. Average annual total production costs incurred by the Gulf of Mexico shrir.ip fleet per pound of shrimp produced and average annual v/holcsaJe price of shrimp produced and average annual wholesale price under alternative policies Per pound Policy production costs Wholesale price 1 $1.19 $1.41 2 $1.19 $1.41 3 $1.27 $1.42 4 $1.11 $1.43 5 $1.22 $1.43 See text, page 116. 125 the fleet, a per pound landings tax is the most effective policy. No controls and regulating age at first capture are tied for the second position. A combination of landings tax and entry fee is the next most effective while a vessel entry fee alone produces the highest costs per pound. The model does not presently provide information that can be used directly to evaluate the effects of the policies on consumers. However, if the wholesale value of the catch is accepted as a proxy for retail value of the catch and some assumptions concerning retail demand are accepted, then some tentative inferences concerning the effects of the policies on consumers can be made. Doll [16, pp. 35, 70-71] finds that the price elasticity of retail demand (in his annual model) at the mean of price and consumption is -0.63 and that the price elasticity of wholesale demand (in his quarterly model) is -0.50 at the means of the variables. Thus, retail and wholesale demands as reported by Doll appear to be relatively inelastic, a finding corroborated by Miller et__al. [24, p. 45]. The significance of these results for evaluating the effect of the policies on consumers lies in the fact that, given a downward sloping demand curve, changes in quantity taken in the neigh- borhood of the quantity used to calculate the price elasticity produce 2 The fact that as catch is reduced in Table 5.8 wholesale value of the catch is reduced also might seem to contradict the assertion that wholesale demand is price inelastic in this range of landings. However, as domestic landings decrease in the model, imports increase after a quarter lag (see equation 4.3). Thus, the effect of decreased domestic landings on the total annual supplies of shrimp available to meet whole- sale demand is not readily predictable. It would appear from the results in Table 5.8 that, as landings decrease, imports increase by enough so that the increase in the wholesale price is not enough to produce the increase in wholesale value of the catch that would be expected if landings were to decrease and imports were to remain constant. 126 larger changes in consumer surp3.us (measured as the area under the. demand curve and above the price liiie) for price inelastic demand curves than for price elastic demand curves. For example, there is no change in consumer surplus as defined here in response to quantity changes when consumer demand is perfectly elastic; there is, in fact, no con- sumer surplus. For a complete inelastic consumer demand curve, minute changes in quantity supplied produce infinitely large changes in con- sumer surplus. The average annual wholesale prices occurring under each policy setting are presented in Table 5.11. The policies do not cause large changes in v/holesale price. If retail price behavior is similar, most of the effect on consumers of the reduction in domestic landings resulting from implementation of the policies would seem to be offset by increases in imports. However, with apparent annual consumption of fresh and frozen shrimp of 357.3 million pounds in 1970 [30, p. 13, preliminary estimate] coupled with an inelastic retail demand at that quantity, even a small increase in retail price resulting from a propor- tionately smaller decrease in quantity available will result in a sizeable loss in consumer surplus. Assuming that the increase in average wholesale prices indicated in Table 5.11 represents the extent of the price increase at the consumer level, then the annual loss in consumer surplus occasioned by implementing a vessel entry fee is on the order of 3.5 million dollars as compared to no controls. The annual loss in consumer surplus occasioned by imposing a landings tax or a combination of a landings tax and an entry fee is on the order of 7.0 million dollars. Regulating age at first capture produces no signifi- cant reduction in consumer surplus. Thus, assuming that consumers do not pay for implementing the regulatory policies, do not share in the revenues these policies produce, and desire to minimize less of consumer surplus, policies of no controls or regulating age at first capture would seem to be preferabl-'; co cor.suinars. A vessel entry fee ranks second in minimizing loss of consumer surplus while a per pouud landings tax and a combination of a per pound landings tax and a vessel entry fee cause the largest losses in consumer surplus as measured here. The column in Table 5.10 headed "Revenue to control authority plus changes in wholesale value and net return" presents an alternative cri- terion for ranking the policies. Assume that the decreases in wholesale value represent losses to society while increases in net return to the fleet (changes in ex-vessel value less changes in total production costs) and revenue to the control authority represent gains to society (ignoring costs of policy implementation). Then the sum of changes in wholesale value of the catch, net return to the fleet, and revenue to the control authority represents the net gain to society from implement- ing any one of the policies. Of course, implementation costs cannot be ignored and in choosing between a policy of no controls and one involving some regulation, the gain to society from implementing a policy must be calculated net of the cost of implementation. Assuming that all the policies involving regulation are equally costly and that the objective is to maximize net gain (minimize net loss) to society, the policy involving a per pound tax is most effective based on the information in Table 5.10. A policy involving both a tax on landings and a vessel entry fee is a close second while the vessel entry fee alone ranks a poor third. Regulating age at first capture produces negative gain to society and thus, is inferior to a policy of no controls even without considering the costs of regulating age at first capture. 128 As is evident from tlie discussion in this section, no one policy is clearly superior for attaining all objectives. The ranking of the effectiveness of the policies depends on the objective to he attained. The one clear implication to emerge from this discussion is that a policy designed to increase age at first capture is never preferable to one involving no controls, especially when costs of implementation are 3 considered. However, even this conclusion must be accepted cautiously, remembering that many of the parameter estimates used in the model are initial estimates. The ordering of the remaining policies by effec- tiveness changes as objectives are changed. It is possible that the policy types would change ordering for a given objective if the regula- tory variables were set at different relative levels. Thus, it must be remembered that the above discussion is specific to stated levels of the policy variables. It is quite possible that different combina- tions of values for the annual vessel entry fee and/or landings tax, for example, would result in different sets of rankings of the policy alternatives for given objectives. What is really needed is additional research to vary each policy variable to determine its optimum level with respect to a given objective or criterion. A comparison of policies set at their optimum levels with regard to given objectives would lead to more meaningful rankings . The implications stated here are meant to describe the relative effects of different and specific types of policies, not to endorse a particular policy in a given case. Also, more meaningful policy 3 It is interesting to note that policies designed to increase age at first capture are the only regulations currently in effect in the industry and these are enforced by individual states. 129 rankings will he possible: in an environment in which the objectives and limitations oT the policy-makers are kno\>m and taken into account. In addition, there are improvements and extensions needed in the model that will increase the reliability of the information it provides. Some of these improvements and suggestions for further research are discussed in Chapter VI. CHAPTER VI RECAPITULATION OF THE PRESENT STUDY WITH SUGGESTIONS FOR IMPROVEMENTS AND FURTHER WORIC The present study is summarized in this chapter and attainment of the objectives is assessed. A simulation model is not easily brought to perfection and certain improvements needed in the present model are cited. In addition, this study provides the basis for several sugges- tions that may prove fruitful for further research. Recapitulation of Objectives and Evaluation of Achievements As listed in Chapter I, the objectives of this study were to: 1. Determine the responses of individual fishing firms in the Gulf of Mexico shrimp industry and the resultant aggregate effect for the industry to changes in: a. The shrimp population in the Gulf of Mexico; b. Technological conditions of harvesting and processing; and c. Demand conditions. 2. Determine whether alternative management strategies exist which will improve industry efficiency in a social sense, reducing overinvestment and/or the extent of non-optimal husbandry practices that occur as a result of the free use of an open access resource. The steps involved in pursuing the objectives involved developing a bioeconomic theory of a fishery and applying it to the shrimp resource, 130 131 A rather general abstiact model of shrimp resource resulted from this application. Based on the abstract model, a simulation model of the Gulf of Mexico shrimp industry was developed. Experimentation with the simulation model produced empirical results relating to alternative policies . Objectives l.a. and I.e. did not emerge as the primary objectives of the study. They were achieved, however, to the extent that a model incorporating estimates of the indicated responses was realized. Objec- tive l.b., relating to responses of firms and the industry to changes in technology, was not satisfied. The model resulting from this study could, however, incorporate certain types of technological changes such as changes in trawling effectiveness or ability of a vessel to fish more days per month. Objective 2. emerged as the primary concern of this study. The part of the second objective relating to non-optimal husbandry practices was approached only indirectly through the effect of the policies on measures of the value of the catch. The effects of the specified regulatory measures on investment in the harvesting sector of the industry were determined. In addition, the relative effects of the regulatory policies on several measures of industry performance were discussed. Part of the objectives set forth at the beginning of this study were attained to a limited degree. In order to more fully achieve the stated objectives, there are certain parameter improvements and model extensions that need to be made. Improvements Needed in the Present Model and Suggestions for Further Work Most of the work that seems to be needed involves obtaining more complete data to improve parameter estimates within the model. In this 132 regard, sensitivity analysis on the present parameter estimates to determine which ones are the most critical and thus, need more careful estimation would seem to be a logical starting place. Model improve- ments are, however, not without cost, and potential gains from model improvements must be weighed carefully against the costs of making and implementing the improvements before research is undertaken to improve the model. Improvements are needed of estimates of the frequency distribution of shrimp recruits by species, area, and month of year. The means and standard deviations used in the model to generate recruits are very rough estimates indeed. Other areas for improvement in the basic resource model include improving the mortality estimates used in the survival equations, differentiating the growth of shrimp by species and season, as well as relating the fishing mortality suffered by a size class of shrimp to the fishing effort of specific size classes of vessels. As an example of this latter recommendation, it is unlikely that vessels over 80 gross registered tons contribute very much to the fishing mortality of the smaller size classes of shrimp that are taken in relatively shallow water. On the other hand, boats (craft of less than five net registered tons) do not contribute to the fishing mortal- ity suffered by the larger size classes of shrimp in the deep-water grounds away from the coastal areas. This problem may be solved by considering fishing effort by vessel size class to be specific to parts of an area by depth or by inshore versus offshore classification. In addition, more accurate description of the geographic range of shrimp of different size classes may contribute to more accurate mortality rates. 133 The model of the harvesting sector of the industry needs refinement witli respect to the process by vzhich vessels enter and leave the fleet, allocate fishing effort among areas, and determine degree of fishing intensity. The improvement in these areas could come in the form of more complete specification rather than restructuring of the model. A study that would perhaps add much to the present model involves identifying the relative magnitudes of the determinants of cost per day fished by vessels in different size classes fishing in different areas of the Gulf of Mexico. The vessel costs per day fished obtained from such a study could be combined with the catch rate and returns figures of this study to determine net revenue more accurately. Given accurate data on net revenue and effort by vessel size class and area, a study to determine the causal relationships between net revenue and effort should improve the vessel allocation and effort intensity schemes. The model of the marketing and demand sector is the product of Doll [16]. If this model were respecified to conform to a monthly time interval and expanded to provide an estimate of retail demand and ex- vessel price by size class of shrimp, it would be more conformable to the data requirements of the simulation model. This extension of the model would allow development of a more refined measure of consumer surplus and, consequently, a more complete evaluation of the effects of proposed regulatory policies on consumers as well as other segments of the industry. Meaningful systems analysis projects are evolutionary in that they require models which are continually updated to keep them relevant from the point of view of the current physical, biological, and decision environments. All of the above suggestions for further work would not, of course, result in a perfect model. 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O l^-l *— < o q: O O o X O X 1/1 CJ I/) CO rsj ^-4 a a: o o: u r-l 'C o C_) o X a X 5^ _l r- t- N^ "> '^ o ~> -J ^~ lo •-< S^ X •- lA ». fc — . .^ .-4 — ^ > — in ro ► ro f^ «.- LA •• «> <5 •- • _l •. r-H <-l "—«•-• iir: r-l II II UJ II II -T II X H-i — 'H- •-'•-•U. X» A _J>— I ►«.(_) ► — . — »?>; • CL '--_) _J :^ 3 _j _j _i - »• w i i A ^ v^ 2 iiO i^»._J ..-5 -^ 0»-0-3.--3.. •• - — ^ UJ _j _j w- _j ^ :j2 -J^QiOU-XX w i^ w^ .^ w- — (M u> — IT, u'\ir'inininiri«-t^-h-ir\ir\ f->— ^-«--~l — w^ .^ ~; r~l ,-i •"« '-U UJ Ul UJ UJ UJ UJ UJ UJ fM UJ iU UJ X> >-* --t ^^ t— •— I— t— J— I— I— >— K-l— (Ml— I— J— I— I— CM(\J ^ f-4 "-^ I— » ►-4 ►— 4 t— 4 t— 4 ^-4 1-4 *— 4 »— 4 H^ HH 2! 03:f-43"JC33:33:i03jC3^0UO fvi t-l o (M fv4 fSJ (VJ (M (M r<^. CM □ 141 CM fsl i.i -> :>' i-< I in CO II a: •• fk •» •• it: itT it: ic: -? -■> -> -5 ,^ _ _ »-< 0 t~i C\J .w «o vO -0 _J r-4 f-l rW i^ «• »» 0 —> 0 sC •£ HH •«,■ •>^ :z> i/i J/) to -) -> _j _j .J cc ►-^ I— ^ 1—4 N^ d. cr. cc 0^ ' ^ «. ro »- •• -< -^ -^ — ■ r-l vO r-< r-< ~) "5 M II •-< OJ fn 11 .-( II II •■»>—<"} • • ♦^ «- !•— 1 — -- (M (M LLi UJ UJ (M — in :n _J _l •-« •— I • e • r-l LU r~) r-t vi«irvjfM»-Hi-4.-irvji— CM(\j •-i>--• < — _i -} _J _J rvi ». (Nj •— r- -- »-i -• :>i «. >.^ c» |/> es »0 *• <5 p-< vO •"< vC >~< vO "^ t— )! .-I n r-H I! i-l * ■0 o — fvi f.-i r- o in < a in c vO 00 5r lu LU UJ 2 ro ^- ro — r'> r-l !!' "-I U •-' • • • >-i LU »-l lU •-< l;.! .-< lU ii IMOrMO'— ■-'•-••-'I— l~(MI— fSJi— (MH-")0- or)a=30u.u. LL3ci:oci:aQ:oQ!:oi-^ X o in po CvJ rg rvl r-l {NJ 1-1 r-l O O CO en O vO vO 142 m I— i \0 I-! c> <)- .-< vO -f CO r-l o in o CO nj •H CO CO fO o in a» CO o ro c^ o t-1 in o O --• 0> (VI rn Ch f\( rr\ ,-< in O r-« h- .£) O r-< CO 'M m >4- in r- sj- fM r\j '^ -i- CM "J- nO vO f^ iTv (Nj in 00 CM in f~ r- Csi CO r-t in r^ nj rn o CM u^ (\J CO -o o^ o -r r-i u-\ (W .T. O'- vT CO C'l r«. ~i o ^ .-1 CO o r- <\) »r ^ CO !»- ©>*■— <'^c^r>r^ococ3Pinr^ ^mrvj^i-rom c>ooNrcofMO— »-too^O"'OfMrOvDi.noo^ccDvj-L"if\j>Tor-coi-iovro^f<^ccvCoocofM«r O vO c^ vO CO CM CM u"\ c\i r-< rn vT c^ '-< CO r- >3' o o in cc CO o r- O O f^ t^J XI vO o^ ro vT nJ ,_4(<-C-— < Olnlnoolnomr'^•^J•Oln^oc■•JDO<-'0^-'-'^O^C^'-^r)a>f^J^-^-f<^coo^<^ln h-inoco«--'-<»~tinLno^m'-r^>i'«^rvifOCMCMcnor^«^<~'^'nr-f~-^^cofMoocoooo«ooLnocT<^-o>Tvf CM (\) CI^<-< t-« f\J r-l.-t r-t»-ICOCM'-< O ^ in o r<^ C> CO m o o r^ — < CO -o -H nj in r~ rg CM CM ocx5ocoo<^ino .-I O (NJ cvJ ro rvj r^ r- o (^ in Ov -^ .-I CO fi in (NJ — « ^-0'-j- o c^ C^f'^f^Jro^O'-^— *" fNJ ro r\j f>T ^- "-< c> ro ^t ln>o^~-•~^(Mm^3■ln^o^^■-*c^Jro^tln^o^-•-< ,Hi-«.-(CMnj(\irNJf\jr\jnjrororOfOrorr> O t) O O O O O O o o o cccoQOcocor^r>-r-r~-r^h- OnO>00 (^J^o^rLr^^O^-•-<'^lro3"ininininmin'n OftOOOOOOOOOOO o o o o o o cocococoaTor.coc03D^JOcocoa3aDcocococococo ^0^0^0\0>0v0^000^0^0^0^0«0 •X) 1A3 •O O J- 03 Ln CM ,'<^ o !--« r- vO tn a- vj- vo f^ CO r-l f>- fvl i-t >"( in lA CO !v^ r- Csl I^ vj- ^ Cr- vO fi^ >r O O iA r^ fM O U3 in o -< i-< (*1 CO !~- <0 U-i ^ ^0 (M >d- t^J o r\j in ■t in OT' r-l ^^ 00 in in 03 CO ■0"- in in vO I— I f^ nj O in >j- f-- o r- CT* O O O r- m vT <}■ f<^ o r~ f^ .3- r>- ra v5- tn 'v'< --o c> '-f >— ' n nO 'O -sT r— D-\ CNJ X --H c^ r<- >jD r\( (M s}- *o >r ^ in »o in (^ r-t »-< f>- 1- >o tX) 0 vO fO On t^ 00 r-l i-l O CT> »-*>£) o r^ o >i- in ro r-l ro ni o o m i-i f~ sT CNi ro vO CNJ £>or~corri.a-OOc^oc7^aDinfviooj-o— «0-*coo-J-mcMoor«^o^ocot^^-o■--^Lnc^f^.-i^OfMr^r-4ln-«cO'-•lC^ rr)0^C>(\.ivj-N}-C^O-l >J-vOW3t-< •-I OOOvOfVJ O^~o•-<■£>f^c^c^coo^ln^^'^lr^o 0'-ir-oo»-ooooo <^ln^o>^co<^co^J•<^lOo^f■:l(^JO^J•'--lC^c^Jc^f<^C^C^OlnvD(\l•--^ln^Olnc^O•-<^l■ r^ror-o-cffvjfvJin^-d-a^fo sOoovO-J-f^in •.oo i-i-j-criN .--(r-ia^r-vj r-intM •~io.-i(\j <\jcoo rv) o vj- f\j O m —I o r-< (> r-l 0^ rsjrri%j-invor-»-ifMf<>«j-in«or>-r-oi^'-»(Ni<^vJ"invOr-t--oooc^a^croooooC)0 C>oooooooooooc>oooooooc:)OOoooo.-i— I— I— I— I— ""-^ cocococoaia3cccccoxaocooooococC'XiaocGo?cocooococooRcoocoO'X)oocr-<^ r~ fO t^ o rvi so o o f<^ r-« O r-« r- O O- CO fO f~l in m o o rvj >*■ sr f\J rr\ m .-« ro .-I in CO .-4 f\) CO O i-< -o in <\! o r>- nj vO f^ >o >*- rn f^ r<^ 00 •-< f^ r- o r- vf r-( f-''-^'-<<- r- sO v£) ex? CO r— I vT -O f-« (\J fO rsi i-t <\j o •-t f^ vO fO ro CNJ •4- rO h- f~ in >j- ^ o o o i>o vo vO ro (Nj r-4 in ro o — 1 in 3J a) r- vQ o .-< o ("-J ^- u> c 1 Li'^ .^ nT h- O sC >J- r-< I-* O N- t» f- ro O .--l .--4 fO "H r-« in (^ r-1 r- ,-4 t»- CO .-< vO O^ in CX3 ■J" '-' r-< ro r»- ^o f\j in nj r-« vO in r- r>- -« poinoinc>f^i£>rOi-tr-iinro^i-ro^-cor~»-4a5>i-i-t oininr^>5-in>}-cooc^^C'C^ln^«-fO(^J-^^-lvr>J■c^^fJcor~co^occ)c^o^^vO<^••■<^-Xln>J•(^">m a■)lno•--'coO'-(^.'Lnmln^-lnrOJ■■J-r^J.-<»-iOT'J"0 fO in ^ vO -« CT> r-l -t ro O ^t- CO O O^ vj- in sO %1- f\J r-l O ro fO ro f\J ro fOOOOcooOfNiOf^ in >3- CO in o £> \f fvi rsi fvi oO'^r~oinvOfNJOinr.*iO'-'co---or\JO.-i 0'~'>J'covir-3-oo>r<-t f\jN}-f-<>*-oin0OOr\JC0OOOJ^^rOOOOO fNj o O r^ CT^ o CO >j- 00 r<^ 30 vj- f\j :o in o c> o r^ ro -f o O <^ co »3- O f^ r-j 1^ G" --< -f O •--' 3") in 1-1 ro f^ '^ (N) f"" J- CM — ' re 0^ csj OOOini-4r-< cornnvj-CJ^ro .-«.-^a3<\iC7^->OfO'-< >*• 1-4 l-H v}- u^ >j- r<^ i.n o^ "Nj nj m1 o CO invOr^fvjinocjt^ og o^ .-4 ro v-c a^ J-invOf~-i-lfNJrn>J-invOr-— 'fM.•0«J■U■^vON■ ^^^r-4r-4r-(r-^^-ooooooooo oocooooooraoconocccoco'Ocr>a.)coT)x^a•)oocococ^c^c^c^c^c^c^c^c^c^c^c^cr 1^5 vO —4 ^}• vi" rf\ «0 CJ ^-4 CM .-♦ r^ oo i-i vO CO CO 00 o rn cv O o •J- csj in O ir. O ^ O f- (^"1 p-< r^ o vo »o tr\ .-4 f\i in vo ^ m in o CO CO '7> CO o^ C\! O o CO o in nO in in "4- •-* nj r- r- CM r- m lA -O m in in r«- fo —1 vO <}• >o CM L-^ O OD in r- CM r- ro ^\i CM O i^\ --I •♦ CM vj- nj- !• (M go (M r-4 o r"* ro o o -^r o (> o (M i-< o (>■> nj vO »J- nO vf o in CM <>i — ' (7- ^.0(7v,-HO— 'OOOOOOOcOOOOininOOOOOCviOO o^'-(fMC^r-oc^'ii^omo-^0'-«P^infMo>t(MfnvOOcnc7>r\)0000<-«inrc»rri f\jcovi-vj'co.-^t-«r-+r^>j~4f— -oor-o .--< (M (NJ--0>i- r-(fMCf>CM O^CJOOD »-< CM CC.-imOCO vOCT^^fCOOOOOOO--* ocoiMLnvj-cninO'-HrvJOOOoo ,-(coinmofn'<^CT>coooCT^f*-^~oocx) CO CO ^ o o^ nj in CM h- sO o ^o ^-■ fCj rH f- CT^ T— I (.i^ ui u^ c._) *^» f^i IT -Tj i«i "^ tr p- r^ i^ i«> tu »}-f^mr^sOOinincMcoi-j-cMNOcoo^cM'-4 »-(aocnfMin»-icsi.-iQa'-«>l"r^inro^-4vOcO'-J--l"in »-i->o r-i rn <-i r^r-«cMrnvtinsO(^'-^inxOf~-'^njco-^in njc^^f*", r<>,-nrnrOrA^*->}-vt-inj^ininininLn%OvOOvO>OvO»Of^r^r-r^i^ OOOOOOCOOOfDOOOOOOOOOOOCJOOOOOOOOOCiO (^c^c^c^c^r^cT■c^c^c>c7^C"C^c^oc^c^c^o^oc^<7^^-^-^-r^^-^>-^-(•-r^r^^-^- i/.r. in CO o r<^ fO f- O >3- O (^ '-'^ CO in t«- o (^ o vo m >?- £> f* O vO O O ITi cr o cc o O f^T ro O a< c> o U\ O r-l r^ f^ CO vO O lA ir\ J- vT OD «M U^ O (Nj -» r>- fO t^ ro C^ f-- u-> O .-ri O lO. P>- (?- —1 <-< vj- C> f\' — 4 >?• O CM O fO (\f CO r-l o a^ t~- m- fO m 3> fvJ r-l r-t CM r-i r~ o ^o lA vO ^0 CO o CO rr> CO O Ti in vT CO >^ (M —4 CO r— sO o t-» o 4- rvj o in -r> --.o (M o f^ fv in vO (^ r^ i-« m .-» in r»- vj- o r^ CO .-( ^- CD .O -< —< m ■.J- nJ- (T> •-< in r~ ^- m c'j f^ <\J O <^i C^ o 00 00 00 on O' -r tr\ o --' sj- -J- vO c^i m <4- O (X) CM f\J C.> o i/i o^ a") o sT' 0» rvj CC' o^ f-' — < r- >o aD in^rvTvO— <»-i3- lo (M >j- uA ri-^ r<\ vO O >?■ >-i in ^- r-< in r-l 1^ -O f^ o 1^ o >D 00 o r^ .-I "^^ in o r~ »j r-(»^vr^or~cO'-o •ootM-^vOoocoooinr-o r>-coroofMrrinjcooco<\i>j-sO C>h-«-'h-CO CC>o ir, r- in •-H in f*i .— I r-4 ro O O O —< o^ O >}- r-4 fM o o in fO in m vO vO ro inrM(M (MOrO^tO inOOOrr^iM r~ o J) o r- O (MO'~o .Of^'-«fMmvj-invOh-»-*-inNor-r-«rM.'"v>*-invor^'-<-^(Mro>^ r-r-aDo3coa)30foaDO(>0 t^a-'C^0^ooC}OOOO rs) (M CM rvj oooooooooooooooo r^r>->£)0>OvOvO»n«of^h-f^r^^-f^r~'vONO<>OvOvOvOf»-r»-r~f^f~-r-r-r~N-r-f>- rsi i-H 147 00 O £> O O 00 o r*- >£> (7^ en •-< vO lA f1 fO >d- .-^ o CM «! C> »-« UA 0» lA vO r-- vO ro O CO f-l vO vO o in CM in o ^f o \0 m C' (V >!• O Nj" 1- rO fO r<- o «i- ro r- ^o in f- in r- (— o .-< r~ -o fO fA fM (V) f^ o in <^ CO CO CO o fM CO •-< CO T) CT< r--- <"j <;• ro a» O —1 o c> r-i CO r-i .r O tt' (M C ^J" lA (M >d- in fO C7^ •-< ff^ fo v^ fo r-« (NJ CM sT oco vO CO nO vo o -^r O '-' CO CM »-• CM O O CO CO r^ cr CM C^ O en o r- rvi cr cvj >o -4- CM CM ,-« f<>i CO 00 in o in 1^ m o o f^ O -J" CO o3 vo in CO in r-o CM o o ^^ rf> vt- (> (T> CO — < Lr> r^ o CO r^ vO •-< r~t .}- ln o ^o CO »o tn in •-< r- r^ in fvj r-< .—( CM CA CO CO in >o vf CM r^ in (\) '-< sj- in in CO ir» o ^n CO f- 00 o c> in r-~ o in iM CO CO 00 CO O CM CO ^ sT r- -l" o o r- m c^ CO CM o lA p~ in o >o CM CO CM CO in CO r«- o ^- v£i o O CM CO f— o 00 t-l r-l CM — < o XI in vO o CO %0 00 vj- O Ovd-o»oincMf^^i-r^ cMif\uo«o^or~vor-f-- in --I 30 o in 00 (V> r-l .-J O CO vO O in CM 00 ro o^ CM CO m CO vO f>- vO o o CO (Mr*-0'-j-co>t«d-4-invD>oinoinr~-cMr--cMOoorvjnina:?f^.-« CMCMfOCMoOvi-inu'XvtinrOCMl^ O O O O O O LH OLnininoof^in in jy CM CM PO f,-) f\! t^ ino(^'-<'N.''^-4-ins0r^ CM CM CM CO CO t*^ CO CO CO ro r-(>-)f-Hr-<'-<<-<<--— *•-' in'-fojro^inor^ co --icM'<\«i-Ln>or>-coCT< CvJ CO APPENDIX II Simulation program, BIGOKE, and initialization data 149 1 • 0 u. LU 'jj a t'l LU Ul vU cr >d- o UJ UL > a: Ou < h-* IJU Ui 0 t- UJ 5- »— K CL _J ~z o >- s: t/O X 0. CD 2r < Cl 0 »~# 2 Ul 0 >- < < 0 D. (~ •-^ < < X t—l -J \~t _i s: 2- < •s. Cf. K- X Q:: >- (Z HH UJ UJ UJ (_ # "5 ilJ UJ < > LL. 0 • LU =3 _j US _l _i X d !- •• CC (i X ^ x UJ < \- ii! UJ to < UJ t~ 0 to 1— UJ • < 0 13 0 X «: CO UJ LU a. T'i lU _J 0 X 1- 0 ^ to < s 0 CC UJ > r-4 >— < 0 f— CQ 2: tti s 0 c-: Q 1— 10 »-< 0 > c; to to ITi -^ 0 UJ 0 ^~ 2: < >- ^ 35; c •— 1 ci: _J ^ < H- 0 f-« a lA »— 1 X a 2: _J 1- Z) •rr 2 o i>0 _J _! c a. 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CM ^ o a? o <>- u> r- r- r- in o --f >i- r\i— :>oo-o Oi'O^-Or-if^Lno coromo-^o rc(OLnu-\ra -j-vrsOvOcn-Hin vtr-N-ino m— o h- o ^r —( r- r-« .-Nj in r\i cm r\j (\j o <}■ co o t-( r- ^ co iTi "i f~ •-^^o-j- in rcif^'> (MtMo^^r—ivC <^ f^ o r- o o o o o m. •-' r-c o o o o C' o o o o nj o co m c:- ^o -j- c> o tv nj rr> ,-< —< CM r-- ffl o^ vO CO CO (<^ r-. ^ ro cAcoo^i-o i-fo-oovj- r-OvOmor^r-i mr-rd- CO t\i r~ nj ro <'>J — < vO vON-f-ifvjmvj-invor-r-tjNjnvj-insO o Q i/> ^/) 176 o o o o o in iTi r- o sO >o r- r^ r^ r^- -£> ■f. LTi in r— ■if> in lA in u'\ lA X\ t^ ir> C) r«- in t— ^f> r- ;J"^ r^ o r~ ;n o o o CT- vQ 'J^ ro r- vf f~- c> fM fO in -J- L^^^(J^o^-->o^--^~<5^-vo^Olf^ to r^ in in ir> lo m r^ o ^- m u-^ in in in f^ o ^- -n o o o o CO r- vO — < m >t ^ IT. ro r\i o m (M <^»j--j'vrinvDvOLnvOint tn in m in in rs! o o in o tn f"<.' o fM in o in n. O O r-* O r-< o o o o h-r\)^-f\joocnjincnoot^0 fMmnjmsj-inmxfLnmrMfsj in in in in in f\i o O O rvJ o fNJ C O O fM O (M o o o .-< c.< o O -" in in inmiAoof^ii^inoooo oooo i-i»-i i-i(Mmmf\ji-i.-(0000 o o o o o o 177 (.■^ to u"( i.n lA -o ir\ ■r'. .mm ltn m r- m m f^ o r^ JA I*- '-^ r~ i^ r~ c; r- r- m m ia m r-- m m m in t. i,'\ ;r- f-^ (^ t-- t~ f.- f^ t^ o — t o o o o lO U"> Lf\ Ul „4 -J ,-» r-1 in in in r- o in in m if\ lA o lA ,-( r-i m o in m m in (M (M --< f<^ •*• »o 1^ c:/ in »-i ro O^ .-■ ■ ' u^ 1^ r^ (^ ^- (-- ^. N_ i^ f^ (_-y Q -J, c_^ o c_i o vo r-i (m rg ^ t~ o . ? ro rf^ ^ O in >4- O O — I r-< C' O 'J ..J O O O o^ rNj — 4 00 rj o <;^ rsj ^ rvjfMfvjrMrvjfv^ rj ,-ic\jf\i— i ^-i r-i r-( >—» r-i .—<.-< f-< in in vO O O f<^ r<^ ro n o o o o in in in in m o t-t .-( r-l .-1 .-H .-< ,-1 ,-(,_( ,-l ,-H ooooonoofMfMr- o o CI o o N- in vi- sj- cocooDcoco •-< (\iro ro f<^ sT o o O O vT <- t si- ir. (M •-< rv) ■•n (sj in r- 00 CO QO CO oo C-\ CO -t o o o o o o o r- '-« 0.1 ro in o o r- >-« an rf>i m o o O O Ci .'j o o u^ r^ m o in f^ r^ m <• o ooo ooo ooo in -j^ ininiain ocoinsO a^ajinvo ^^^^ Lnnjoo in(Mi:o 179 O >j- ^ -t rn ir-. vO nO 00 CO o in m r<^ rn o r ro >j- !■ vO sO o < >i- -r o o CO ro i- o o 03 Q U. O J- o c m LU •d- vr o o in CO o o in ro LIST OF REFERENCES 1. Anonymous, Basic Economic Indicatoi's; Shrimp, Atlantic and Gulf, Working Paper No. 57, Division of Economic Research, National Marine Fisheries Service, College Park, Maryland, May 1970. 2. Anonymous, Gulf Coast Shrimp Data, United States Department of Coimnerce, National Oceanic and Atmospheric Association, National Marine Fisheries Service, Washington, D. C. , in cooperation with Fishery Agencies of Florida, Alabama, Mississippi, Louisiana, and Texas. Annual SuBimaries for 1967, 1968, and 1969. 3. Anonymous, Marine Economics Data, Oregon State University Sea Grant, Marine Advisory Program, Oregon State University Coopera- tive Extension Service, Corvallis, Oregon. 4. Anonymous, "V'ater Teiaperature Guide to ShriDip and Tuna," Fishing News Inter, ational 10, No. 1, 34, 37 (vTanuary 1971) as abstracted in Coiiuiercial Fisheries Abstracts, National Marine Fisheries Service, United States Department of Comnercc, July .1971, pp. 7-8. 5. Arnold, V. , An Analysis to Determine Optimum Shrin'i' Fishing Effort by Area, Working Paper No. 40, Division of Econom.ic Research, National Marine Fisheries Service, College Park, Maryland, January 1970, 196 pages. 6. Barry, E. J., "Gulf Fisheries (Selected Areas): 1969," Division of Statistics and Market News, National Marine Fisheries Service, New Orleans, Louisiana, February 19/1. 7. Berry, Pdchard James, "Dynamics of Lhe Tortugas (Florida) Pink Shrimp Population," Doctoral Dissertation, University of Rliode Island, 1967. 8. Boutwell, Ken and McMinimy, Vernon, "Use of Mathematical Simula- tion Models in Analyzing Agricultural Policies," draft of an Unpublished Memorandum, 1967. 9. Bromley, Daniel, Economic Efficiency in Common Property Natural Resource Use: A Case Study of the Ocean Fishery, V^Jorking Paper No. 28, Division of Economic Research, Bureau of Conmiercial Fisheries, College Park, Maryland, July 1969, 162 pages. Also published as a Doctoral Dissertation in the Department of Agricul- tural Economics at Oregon State University, Corvallis, Oregon, 1969. 10. Captiva, Francis J., "Changes in Gulf of Mexico Shrimp Trawler Design," paper presented at Conference on Canadian Shrimp Fishery, Saint-John, N. B., October 27-29, 1970. 180 181 n fhristv Francis T., Jr. and Anthony Scott, Tjie_Co2moiLWGalthJjl Ocpan Flshp.-ies: c._^^Pvr,h1 ..^^. of Growth and Economic AUocatxon. pabli'ibrd1^r"'R^i^rces for the Future, Inc., by The Johns Hopkins Prej-s, Baltimore, Maryland, 1965. 12. Ciriacy-Wantrup , S. V., Rescu£c_e_Conserva^on_^_Eco^^ Policy, University of California Press, Berkeley, Californxa, IJ^i. 13. Creameans, J. F.., "m.y Simulation," paper origiur.lly giy^n at a symposium of the Washington, D. C. Chapter of the Assoc.atxon for Computing Machinery, May 18, 1967. 14 Crutchfield, James P. and Giulio Poatecorvo, The_Jacifi^_Salm.Dn Fisheries, published for Resources for the Future, Inc., by Ine J^ns Hopkins Press, Baltimore, Mar>'land, 1969. 15. Crutchfield, James P. and Arnold Zellner, "Economic Aspects of the Pacific Halibut Fishery," FTc^herv Industrial Research, Vol. 1, No. 1, Fish and Wildlife Service, April 1962. 16. Doll , John P. , An Econometric Ana3^sj^_^LlJ2^iL-^A^-£J^gELii^rj^^ Working Paper No. 79, Division of Economic Research, !',c.ticnai Marine°Fisheries SerA'ice, College Park, Maryland, Feb ruary 19/1. 17. Forrester, Jay U. , Industrial Dynamics, 2nd printing. The M.I.T. Press, Cambridge, Massachusetts, June 1962. 18. Geisler, M. A., Haythorn, W, W. , and Stager, W A. "Simulation and the Logistics Systems Laboratory," Mem.orandum El-I-32dl-PK prepared for United States Air Force Project Rand, September 1.62. 19. Gordon, H. Scott, "The Economic Theory' of a Common-Property Resource: The FisheiT," Journal of PoliticaJJEconom^, Vol. LXli, No. 2, April 1954, pp. 124-142. 20. Gulland, J. A., Manual^liLethojl^_JorJlslL.St^^^ li_llsh.Po2ulatiirAii^iii, Food and Agriculture Organxzatxon of the United Nations, Rone, 1969. 21. IBM Svstem/360 Fortran IV Language, IBM Corporation, Prograinming Syster.-£ Publications, New York, New York, 1966. 22. Lassiter, Roy L., Utilization of U.S. Otter-Trawl Shrimp Vessels in the Gulf Area, 1959-1961, Bureau of Business and Economic Research, University of Florida, Gainesville, Florida, 1964. 23. Lyles, Charles H. , ti^ery__Statistics._ol^heJIn^ Bureau of Commercial Fisheries, Washington, D. C, 1939-1967. 24. Miller, M. , D. Nash, and F. Schuler, Industrx^AnaJ^:sa^_of_Gulf Area Frozen Processed Shrimp and an Estimation of Its Iconomic ^^ Adaptability to Radiation Processing, Working Paper No. 16, Divi sion of Economic Research, Bureau of Commercial Fisheries, College Park, Maryland, October 1969, 100 pages. 182 25. Orcutt, G. H. , "Simulation of Economic Systems," The American Econoiuic Review, Vol. 50, No. 5, December 1960, pp. 893--907. 26. Osborn, Kenneth W. , Bruce W. Maghan, and Shelby 15. Drumraond, Gulf of Mexico Shrimp Atlas, United States Department of the Interior, Bureau of CoirjTjercial Fisheries, Circular 312, VJashington, D. C., May 1969. 27. Osterbind, C. C. and R. A. Pantier, Economic Study of the Shrimp Industry in the Gulf and South Atlantic States, Bureau of Economic and Business Research, University of Florida, GainesviDlej Florida, 1965. 28. Scott, Anthony, "The Fishery: The Objectives of Sole Ownership," Journal of Political Economy, Vol. LXIII, No. 2, April 1955, pp. 116-124. 29. Smith, V. L., "Economics of Production from Natural Resources," The American Economic llcview, Vol. LXIII, No. 3, Part 1, June 1968, pp. 409-A31. 30. Surdi, Richard W. and Donald R. Wiittaker, principal contributors, Shellfish: Situation and Outlook: 1970 Annual Review, Current Economic Analysis S-20, National Marine Fisheries Service, United States Department of Commerce, Washington, D. C. , March 1971. 31. Tyner, Fred H. , Jr., "A Simulation Analysis of the Economic Struc- ture of U. S. AgiiculLuie," Doctoial Dissertation, Oklahoma State University, Stillwater, Oklahoma, May 3 967. 32. Tullock, Cordon, The Fisheries ... Some Radical Proposals, Ecsays in Economics No. 6, University of South Carolina, Bureau of Business and Economic Research, School of Business Administration, Columbia, South Carolina, February 1962., 29 pages. 33. V>Tiittaker, David A., Jr., "Economi.c Effects of Trade Policies on the Shrimp Fisheries of the United States and the Latin American Nations," Doctoral Dissertation, University of Florida, Gainesville, Florida, 1971. ADDITIONAL REFERENCES Bator, Francis M. , "The Simple Analytics of Welfare Maximization," Tlie American Economic Review, Vol. XLVII, No. 1, March 1957, pp. 22-59. Bell, F . W . , Estima t ion of the Economic Benefits to Fishermen, Vessels and Society From Linited Entry to the Inshore U. S. Northern Lobster Fishery, Working Paper ho. 36, Division of Economic Research, Bureau of Commercial Fisheries, College Park, Mai-yland, March 1970. Bell, F. W. and J. E. Hazleton, Recent Developments and Research in Fisheries Economics , published for The New England Economic Research Foundation by Oceana Publications, Inc.. Dobba Ferry, New York, 1967. Carlson, E., Bio-Economic Model of a Fishery (Primarily Demersal) , Working Paper No. 12, Division of Economic Research, Bureau of Commer- cial Fisheries, College Park, Maryland, March 1969. Cleary, Donald P.. Demand and Price Structure for Shrimp > Working Paper No. 15, Division of Econo'iiic Research, Bureau of Commercial Fisheries, College Park, Maryland, June 19'J9. Crulchfield, J. A., "Econor.ic Objectives of Fishery Management, The Fislieries; Problems j.n Resource Management," University of Washington Press, Seattle, Washington, 1965, pp. 43-65. Food and Agricultural Organi?^ation of the United Nations, Yearbook of Fi sh ery Statistics, Vols. 26 and 27, FAO, Rome, Italy, 1968. Nash, D. and F. Bell, An Inventory of Demand Equations for Fishery Products, Working Paper No. 10, Division of Economic Research, Bureau of Commercial Fisheries, College Park, Maryland, July 1969. Ricker, William E., Methods of Estimating Vital Statistics of Fish Populations , Indiana University Publications Science Series No. 15, Blooinlngton, Indiana, 1948, 101 pages. Samuelson, Paul A. , "Contrast Between Welfare Conditions for Joint Supply and for Public Goods," The Review of Economics and Statistics, Vol. LI, February 1969, pp. 26-30. Scott, A. D. , Economics of Fisheries Management: A Symposium, Institute of Animal Resource Ecology, The University of British Colombia, Canada, 1970. Sokoloski, A., Some Elements of an Evaluation of the Effects of Legal Factors on the Utilization of Fishery Resources, Working Paper No. 8, Division of Economic Research, Bureau of Coimnercial Fisheries, College Park, Maryland, February 1969. 183 Sugiri, G. K. A., "A Description of the Tortugas Shrimp Fisliery and ii.s Maximum Sustainable Yield," Master's Thesis, University of Miami, Coral Gables, Florida, January 1971. Turrey, Ralph, "Optimization and Suboptimization in Fishery Regulation," The American Economic Review, Vol, LIV, March 1964, pp. 6A-76. Turrey, Ralph and Jack Wiseman, The Economics of Fisheries, Food and Agriculture Organization of the United Nations, Rome, 1957. Zellner, A., "On Some Aspects of Fishery Conservation Prob] ei.is ," reprinted from the bulletin of the International Statistical Institute, Vol. XXXVIII, Part III, Tokyo, 1961. BIOGRAPHICAL SKETCH Paul Jerome Hooker was born on August 29, 1943, at Homestead, Florida. In August, 1960, he was graduated from North Marion High School, Reddick, Florida. In August, 1966, he received the degree of Bachelor of Science V7ith a laajor in zoolog}' from the UnJ.vcrsiLy of Florida. During the 1966-67 school year, he taught biology and chemistry at North Marion High School. In 1966 he enrolled in the Graduate School of the University of Florida. From August, 1967, to December, 1971, he has held an NDEA Title IV fellowship, worked for two quarters as a teaching assistant, and has been employed as a graduate reseat ch a^'sociate in the Department of Food and Pvcsource Economics v.'hile pursuing the degree of Doctor of Philosophy. He is currently employed as Iviterim Assistant Professor of Food and Resource Economics with the University of Florida on assignment to the Ministry of Agriculture of Guyana. Paul Jerome Hooker is married to the former Martha Jean Yongue, and is the father of one child. He is a member of Gamma Sigma Delta, Omicron Delta Epsilon, and the American Agricultural Econom.ics Association. 185 I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is Cully adequate, in scope and quality, as a dissertation lor the degree of Doctor of Philosophy. :'olopo.'-!' ■ , Lh^r!.i,on Professor of Food and Resource Economics I certify that I have read this study and that in my opinion it forms to acceptable standards of scholarly presentation and is fully conf adequate, in scope and quality, as a Doctor of Philosophy. dissertation for the degree of jr. Max 'R. Laagiiauij Professo Food and Resource Economics I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor oi Philosophy. W. VJ. McPherson, Professor Food and Resource Economics I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Carter C. Osterbind Professor of Economics This dissertation was submitted to the Baaii of the College of Agriculture and to the Graduate Council, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. March, 1972 D;';::n, Graduate School 9 9110