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ARTIFICIAL FERTILIZATION OF LAKES AND PONDS A Review of the Literature
SPECIAL SCIENTIFIC REPORT- FISHERIES No.ll3
Pne Biological Laboratory LIBRA?' ^
i\^ARl2 ....-- WOODS HOLE, MASS,
UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE
Explanatory Note
The series embodies results of investigations^ usually of restricted scope^ intended to aid or direct management or utilization practices and as gxiides for administrative or legislative action. It is issued in limited quantities for the official use of Federal, State or cooperating Agencies and in processed form for econoray and to avoid delay in publication.
United States Department of the Interiors Douglas McKay, Secretary, Fish and kildlife Service., John L. Farley, Director
ARTIFICIAL FERTILIZATION OF LAKES AND PONDS A Review of the Literature
By John Ac Maciolek Fishery Biologist
Special Scientific Report: Fisheries No. 113
Washington^ DoC, January, 195U
TABLE OF CONTENTS
Page
X
Introduction ................... oo o. ..o .
Fundamentals of aquatic fertilization. ......... 2
Physical considerations ................... 2
Biological considerations .................. h
Chemical considerations ......,=.,,........ 5
The fertilization p rocess ............. 12
Interpretation of results .................. l5
Fertilization and pond culture .................. l6
The pond and enrichjnent procedure « ............ . 17
Techniques contributing to maximum production ........ 18
Conclusions on pond fertilization ......,„.,...., 19
Farm fish ponds. ,.„..,,,.„..,.,,,,, 21
Fertilisation of lakes ...................... 21
The environment and artificial enrichment .......... 22
Experiments in lake fertilization ... .......... . 23
Conclusions on lake fertilization ,.......,...,. 25
Summary. ............................. 27
References . ....<.,......,......,..... . 31
Literature cited in text. ,.....,,....,.,.., 31
Other literature reviewed ... .............. . }6
Appendix A; fertilizers reported in the literature ........ 39
Inorganic .......................... 39
Organ! Co .... c . ..,...,.„..,...,..., . UO
Appendix Bj fish and food organisms reported in the literature . . Ul
ARTIFICIAL FERTILIZATION OF LAKES AOT) PONDS A Review of the Literature
PREFACE
One of the primary factors limiting the productive capacity of a body of water is the quantity of available nutrients which form basic materials for structure and growth of living organisms. Fertilization techniques attenpt to supply these nutrients in optimal quantities, there- by overcoming natural chemical deficiencies and shifting limitations of productivity to other factors. Aquatic fertilization is as ancient as pisci- culture. The Chinese reputedly fertilized carp ponds more than 2,000 years agOj developirgthe process as an art rather than as a science. Through the intervening years, culture-pond enrichment apparently existed as an off- spring of agronomy, but recent scientific work has shown that the two fertil- ization processes (agricultural and aqui cult 'oral) are not homologous because of differences in the very nature of land and water. Aquatic fertilization undoubtedly hasmerit in raising productive levels^, else it could not have survived to the present state of development „
Artificial aquatic enrichment has been limited mainly to standing water^ but a few reports on brackish water and stream fertilization have appeared in the literature. Huntsman (19li8) , for example, succeeded in increasing the abundance of plants and numbers of fish in a Nova Scotian stream with inor- ganic fertilizers. Admittedly, the barren state of the stream provided an excellent background for the experiment. However, these few isolated reports of stream enrichment have been largely trial and error, and do not provide sufficient information for adequate treatment of the subject, A great deal remains to be learned about the enrichment of standing water before a sound approach can be made to the fertilization of lotic habitats. Therefore, the following report concerns only lenitic fresh water and the complexities that relate to its artificial enrichment.
INTRODUCTION
The three essentials for protoplasmJ.c growth are light, heat, and raw materials. Natural enrichment, the source of raw materials, occurs to a certain degree in every body of water, by decomposition of organic matter produced within the environment, by ion exchanges between water and sedi= ments, and by nutrient increases from affluents carrying minerals and humus leached out of the surrounding soils. Artificial fertilization, an accessory to these natural proccesses, is a human-controlled operation concerned with the addition of natural or manufactured fertilizers and directed toward the increased production of fish.
Artificial fertilization is by no means a simple process. Considera- tion must be given to the conditions and variables of the environment which affect both procedure and results of fertilization. Such environmental com- plexities are presented in this report by assembling information which occurs in fish cultural and limnological literature. The objective is to show how and where sirtificial enrichment applies to the present culture^, management, and investigation of fresh-water fisheries in this country. No effort has been made to advise or outline a method of fertilizing^ the intent is to minimize meaningless trial-and-error experiments by giving the investigator a grasp of the complex nature of the subject. The literature reviewed is essentially North Aiaerican_, but certain Asiatic and European reports are included. These European reports represent a composite of vast European knowledge, and frequent references will be made to them.
Early appearance of pond-culture fertilization in scientific literature dates back to European work in the late nineteenth century. Da^/is and Weibe (1930) and Smith (193Ua) reviewed the publications of their predecessors in this field, and Neess (19li9) presented a historical synopsis of European pond culture. These summaries indicated that the first European experiments were directed toward the production of plankton and were later applied directly to carp culture, American work began in a similar fashion (Embody, 1921j VJiebe, et alo, 1929j Wiebe, 1930), As a scientific proced^jrej early enrichment experiments had one fault in common; they proceeded from the nu- trient addition to fish or fish-food production disregarding fundamental physical, chemical, and biological factors which, directly or indirectly^ influence enrichment and the resultant changes in productivity. Cognizant of this, some more-recent investigators have conducted experiments of greater significance. Nevertheless, there exists an incomplete understanding of fertilization dynamics which can be supplemented only by careful experi- mentation.
FUND.1MENTALS OF AQUATIC FERTILIZATION
Numerous factors, inherent in the metabolism of fresh water, concern the process and outcome of artificial fertilization. They may be classi- fied as physical, biological and chemical, but this grouping is made only to facilitate discussion. In practice it is necessary to consider such things as they actually exist - highly interrelated. Moreover, few fac- tors remain constant within a given body of water. The variability ar.d interaction of these factors present basic problems in the understanding and success of aquatic fertilization.
Physical Considerations
Reference to physical factors in literature is abundant but fragmen-
tary. Schaeperclaus (1933) treated the important physical factors in pond culture^ particularly depth. He established optimum depth for assinilative plant functions at 1 to 2 meters., since shallower areas fluctuate readily in temperature and oxygen content, Schaeperclaus further pointed out the in- creased nutrient release from bottom soils per unit water volume in shallow waters, and in ponds with large shore development „ Rounsefell (19U5) in- dicated a straight-line logarithmic relation between fish productivity and size of water bodies | smaller lakes had the greater yield per unit area. Rate of water exchange was considered by Schaeperclaus (1933) ^ Lawson (1937), Ifiesner (1937) ^ and others, who concluded that a small exchange is usually necessary for temperature and oxygen control, but that a large outflow re- moves nutrient materials „ Nutrients may also be lost by seepage or by settling through sandy or rocky bottom tyr^es, which are noticeably unpro- ductive (Lawson, 1937j Province of Quebec, 19h3) , Many authors discuss light and heat requirements as affected by shade and turbidity of the water.
In all waters, light and heat are the physical essentials for photo- synthetic activity which, in turn, is basic to productive capacity. Water temperatures, in general, depend upon climate, sunlight, and depth, Probst (1950) found an avera^^e increase in carp ^deld of 22 kilograms per hectare for each 1* C rise in mean temperature in unfertilized oonds over a period of 32 years. Light intensity and penetration are affected by border vegetation, floating aquatic plants, and turbidity. The latter may be caused bj/ plankton blooms., silt, particulate organic matter, or by pig- ments and suspensoids as in bog waters. Excessive turbidity, according to Smith (i93lja), has a pronounced effect in confining ddily heat gains to the surface layer of water. Plankton turbidity, while often indicative of oroductive waters, limits heat and light penetration, thus reducing the depth and effective volume of the trophogenic zone. On the other hand, such turbidity aids in the control of soft water flora (Surber, 19U8^ Swingle and Smith, 19^0) and improves angling success (Smith and Swingle, 19h3) - Excessive shade caused by aquatic plants is a similar hindrance to heat and light exposure of the water and results in lowered production ('.fiesner, 1937). Temperatures, optimum for growth of the desired fish species, plus time give the grovdng season which is also relevant to fertil- ization. Lastly, water movement can be added inasmuch as it affects the distribution of heat and nutrient materials viathin the environment.
Generalizations may be drawn concerning the physical characteristics of waters vjith respect to fertilization;
1, Dimensional increase of the environment (beyond that of the highly productive culture pond) decreases its possibility for successful fertilization. This limitation involves economical impracticability, lack of control and manipulation, and chemi- cal-biological complexities which will be considered in the following text,
2. Increasing depth decreases the relative productive potential.
3. Geographical locations having mild climates and long grow- ing seasons are most favorable for enrichment because of temperature and light factors,
Uo Heat and light are essentials that may be regulated to some extent by control of border and surface vegetation.
5. Turbidity^ other than that caused by plankton^ is undesirable. Plankton turbidity is a consequence of the productive metabolism of water and may sometimes be of value.
6. Rate of water exchange should be at a minimumo
?o The nature of the bottom affects nutrient loss and productive ability.
Biological Considerations
The organisms in an aquatic habitat, relative to fertilization and productivity, were discussed in some detail by Schaeperclaus (1933) - His interpretation of the biological complement, with modification, placed the important flora and fauna in three groups: 1. Basic producers (bac- teria, water molds, phytoplankton, soft waterflora and microfauna)j 2. Intermediate consumers (zooplankton, insects, and other benthic fauna); 3. Ultimate consumers (fish). Wiesner (1937) referred to the binding of nutrient elements by organisms as "biological absorption", while Meehean (1935), Lawson (1937) j, Smith and Swingle (I9I4.O), and others indicated the importance of bacteria and higher flora acting in that capacity: Plants also act as a storehouse for nutrient elements (Surber, 19U7) » Inverte- brate fauna links flora to fish in the simplified nutrient chain (Lawson, 1937 J Smith and Sxijingle,, 19iiO) , but all orgc^nisras are not beneficial to the productive cj''cleo Nutrients may be lost tenporarily or permanently through the action of denitrifying and sulfate- reducing bacteria (Lawson, 1931) Zuur, 19^2), blue-green algae (Easier and Einsele, 19^8), and emergent aquatic plants (li/iesner, 1937) = Excessive growth of soft water- flora may tie up nutrients, crowd the water, or cause anaerobiosis upon decay (V/iebe, 193U| Meehean, 1935) •
These organisms may be considered, to great advantage, in the pattern of a food chain, or succession of biota from nutrients to removable cropo Meehean (1933) proposed alternative food chains in black-bass culture, and later (Meehean, 193U) outlined a more simplified chain terminating with bass finger lings
Organic Protozoa
Fertilizer —^ Bacteria — ^ Rotlfera -^ Zooplankton -y Chironomids
Nauplii (as Daphnia) Ostracods
\ /
Bass fry ^ Bass fingerling
Three food chains of differing natures were described by Smith and Swingle (I9J4O) s
Phytoplankton ) Stnall organisms)
Bacteria ) Phytoplankton)
Bacteria ) Micro fauna)
(Golden shiner (Gizzard shad (Goldfish
(Zooplankton ) (Insect larvae)
(Plankton) (Insects )
(Bluegill (Small crappie (Small bass
( )
(Small fish)
(Largp crappie (Large bass
These examples are given to illustrate some approaches taken in con- sidering the biological fate of nutrients. Ball (19h9) concluded that food habits (of fish) nearer the base of a food chain result in a greater increase of fish. It thus seems axiomatic that shorter food chains result in larger and more consistent fish returns. The cyclic behavior of populations is another important characteristic of aquatic life closely related to the succession discussed above. This advance and decline of numbers is most oronounced among the lower organisms, and may take an erratic pattern. The nature of such fluctuations is not well understood, but it should be remembered that they may occur independent of nutrient addition.
Final consi deration is given to productivity in vrhich the entire con- cept of fertilization is embodied. The objective of artificial enrichment is to increase the productive capacity of a body of water and so increase the potential yield of fish,. Each environment differs ,n the amount of living matter it is able to support. Lawson (1937) believed that superior production is based on abundant microvegetation. Productive differences among vraters are characterized by many factors, Wunder et al, (1935) seated that good producing ponds have algal blooms in spring or early sum- mer j, and that these blooms are continuous in the best producing oonds. Various indexes of productivity are treated in another section, but it may be stated at this point that the ultimate measure is the yield of desirable fish per urj.t area and time. This productive capacity is realized only when the crop is rermved. Fertilization places nutrients in the water and oroductive anabolic processes transform them into fish flesh. It follows that an expenditure of time and energy on fertilization will be profitable only if the water is cropped and the fish utilized.
Chemical Considerations
The chemical aspect of the aquatic environment is, by far, the most important consideration involved in the fertilization process, A brief description of the chemical nature of lakes and ponds w ill later aid in the understanding of nutrient interactions. The aquatic habitat can be thought of as a quantity of water retained in an earthen bcwl. The re-
taining structure contains mineral and orgarJ.c matter as solid substances which^ by chemical and biological actions^ influence the composition of the water. In addition to this^ Neess (19U9) pointed out the function of the bottom colloidal fraction (humic substances^ ferric gels^ clay) which ab- sorbs and regulates the distribution of certain soluble nutrients, and also facilitates chemical deconposition and transformation by nicroorganic life occurring therein. As in agriculture, fertile soils are indicative of high productivity. Schaeperclaus (1933), Meehean (1935) j and Lawson (1937) discussed the quality of the substratec The bottom^ at least in shallow water, acts as a nutrient storehouse,, center of biological activity, and area of chemical transformations « Topsoil, and soils rich in humus, are most desirable. Marl„ clay_. sand, and rock follow a general order of de- creasing richness o The vrater contains dissolved gases and solids, and sus- pended particulate matter,, which are in continuous exchange with the sub- strate. Oxygen and carbon dioxide are gases most abundant and vital to life processes.- Methane„ hydrogen, nitrogen^ ammonia, and hydrogen sulfide may be present in small quantities,, The last three gases and carbon dioxide may be toxic in large amounts. Suspended solids can be divided into organic (as detritus) and inorganic (silt) coniponentso Dissolved solids comprise a wide range of compounds containing most elements that are in some way soluble in water. These are also inorganic, or complex organic, compounds. A cer- tain proportion of each compound, depending upon its chemical characteris- tics, and those of the solvent, exists as ions in dissociation- this in t'orn affects pH, chemical reactions, and nutrient absorption.
The hydrogen-ion concentration (pH) , a result of many obscure chemical conditions, is one of the singularly significant factors affecting aquatic productivity. Both soil and water should show an alkaline reaction (TflE-esner, 1937). Smith (1933) found the decomposition rate of fish meal noticeably lowered above pH 9oO= Schaeperclaus (1933) termed pH 9=0 the alkaline danger point, and further recommended raising the pH of waters rated 6,5 or lower. It is well known that acid waters are ooor producers. Tne optimal range of pH can thus be established at 7oO to 8,5- To main- bain a constant pH, water and soil must show a buffering action caused by the presence of calcium and magnesium carbonates. Schaeperclaus (1933) and Wiesner (1937) regarded this buffer action as the acid combining capacity (A.CCo) of the water. The A.C.C, (corresponding to our methyl orange alkalinity) is the number of cubic centimeters of 0,1 N hydrochloric acid that can be neutralized by 1 liter of water. Waters of 2 to 5 A=C.C, vary only slightly in pH and are rated as "very productive."
The next step is to relate chemical nutrients to aquatic organisms. Liebig's law of the minimum, directed toward plant crops, has also been applied to fish crops. It states, in essence, that plants require certain nutrients J the presence of any one in minimal quantity will lower the total productivity. Early work in nutrient enrichment carried the results of agriculture to aquiculture„ From its inception to the present time, aquatic fertilization has dealt almost exclusively with organic matter and four chemical elements? nitrogen, phosphorous, potassium, and
calcium. These substances were added to the water in quantities that yielded the most fish„ This approach proved successful in pond culture, consequently„ little consideration was given to the action of these nu- trients or to the many other elements essential to living matter. It was realized some years ago that nitrogen and potassium were not always needed, Davis and Wiebe (1930) presented the European opinion that fer- tilization with nitrogen and potassium is varied in effect, but all agree to the importance of phosphorus. Smith (1932a) found that plankton pro- duction varied directly with nitrogen and phosphorus concentrations,, but irregularities occurred when nitrogen was used alone. Recentlyj Zeller^ concluded that only phosphorus fertilizers need be used in Missouri ponds. While this is far from a complete picture of the work that has been done^ it illustrates the need for a more fundamental approach to the study of chemical enrichment.
¥iesner (1937) listed 17 elements necessary to formulate and sustain life. Grouped in order of decreasing importance, they are; oxygen, hydro- gen^ carbons nitrogen| sulfur _, phosphorus, sodium, potassium^ calcium, magnesium, iron, chlorine, fluorine^ silicon, manganese, iodine, and arsenic, Most of these appear in the environment as compounds of two or more elements- Optimum ranges of some compounds have been established for certain organ- isms. Moyle (19ii5), for example, was able to distinguish three groups of aquatic flora in Minnesota lakes.' Hardwater flora (in waters with alkalin- ity between 90 and 2^0 parts per million^ sulfate below 50 parts per mil- lion, pH from 8,0 to 8,8) j Soft- water flora (in waters with alkalinity below ho parts per million, sulfate below 5 parts per million, pH below 7 .h) ; and sulfate-water flora (in waters with alkalinity greater than l50 parts per million^ sulfate usually above 125 parts per million, pH from 6.I4 to 9^2) , Knowledge of the minimum threshold r equirements of organisms for various elements is nonexistent j except for indications that they are extremely low. What, then, is known about the individual elements in fresh-water metabolism?
The apparent success of phosphorus as a fertilizer has made it the center of interest and experiment,, Its main physiological function is to assimilate nitrogen into cellular matter (Hasler and Einsele, I9U8) . Water phosphorus occurs in small quantities (usually less than 1 milli- gram per liter) as organic and phosphate fractions (Welch, 193$) '■> The organic component is further divided into soluble organic and sestonic phosphorus. Many experiments have shown that added phosphate disappears rapidly from the water, usually within a week or two, Zeller's (1953) work indicated a storage of phosphorus in cells during periods of abun- dance with a later growth at the expense of stored material; he also found a constant increase of phosphate in pond bottoms, and attributed this to insolubility and settling of fertilizers. Hasler and Einsele (19ii8) indicated a rapid regeneration of sedimented phosphorus in littoral
1/ Zeller, H, 1952, Inorganic nutrient levels in fertilized and unfer- tilized farm ponds in central Missouri. Master -s Thesis, Univ, Mo,,
1U5 pp.
areas, and the possible permanent loss of it in hypoliranetic depths. Although insoluble phosphorus accumulates mainly at the bottom, this is also the region of greatest phosphorus solubility (Neess, 19h9) . Soluble phosphorus is highly motile, enabling it to form insoluble compounds with calcium and iron (Lawson, 1937; Ifiesner, 1937 j Hasler and Einsele, I9U8; Neess, 19^9) .
A study by Barrett (1953) indicates that the rate of disappearance for added phosphorus from epilimnial water was related to alkalinity (theoretical lower limit of alkalitrophy seemed to be between 120 and I60 parts per million K.O.k.), and also that the amount of exchangeable phos- phate in bottom sediments was inverselj'" related to the ratio of marl to organic matter. Added phosphorus accumulated in the hypolimmon or sediments in the following situations; In lakes where sediments were high in organic matter and low in marl, phosphorus was adsorbed by sediments and remained in an exchangeable form; where sediments were high in both marl and organic matter, phosphorus accvimulated in hypolimnetic water and sediments; where sediments were very low in organic matter and verj'- high in marl, phosphorus did not accumulate in hypolimnetic water nor was it adsorbed by sediments^ but probably became fixed in insoluble precipitates.
Recent experiments with radioactive phosphorus (P32) in stratified lakes have furthered the understanding of phosohorus metabolism and per- haps the action of other elements. McCarter et al. {19^2) traced the movements of P32 in a lake after introducing it below the thermocline. Lateral r.iovement, quite pronounced in the iirection of the outlet, averaged 3 meters per day. Vertical movement was slight and penetration of soluble phosphorus above the thermocline was not evidenced. Hutchinson and Bowen (19^0) expressed the opinion that most of the added phosphorus enters phytoplankton. The leaves and stems of some aquatic plants absorb p32 before it enters the root system, according to Hayes et al. (1952). Coffin et al. (I9h9) studied living organisms more closely to find absorp- tion of p32occurring in a matter of minutes and hours. Plants and micro- or^.anisms absorbed phosphorus directly. Zooplankton obtained it either directly, or indirectly by feeding on smaller organisms. Fish apparently acquired P32 by feeding upon plankton and similar organisms. Recent experi- ments have indicated that fish may absorb phosphorus and other nutrient substances directly from water. These authors further found that zoo- plankton could concentrate phosphorus up to IiO,000 times the level present in surrounding water. An average of concentration ratios, given for several aquatic plants and animals, showed that the floral level of phos- phorus was about 2^0, and the f aunal level about 20,000 times the water content.
Hutchinson and Bowen (1950) postulated a steady exchange between organic and phosphate phosphorus, and described rapid gains of P-' by the h-j/polinTiion in terms of seston sedimentation. They concluded that T^'- replacement in the epilimnion occurred each 3 weeks. Hayes et al. (1952) proposed quantitative exchanges of phosphorus between the soluble
and solid (including living matter) fractions. In their experiments, the turnover time for soluble P32 was ^.U days, and 39 days for the p32 in solids. Less than one-sixth of the added phosphorus was in solution at any one time. Considering the results of other experiments, these workers calculated turnover times for phosphorus in solids up to 176 days, and for dissolved phosphorus to 30 days. From Uo7 to 8o7 times as much phos- phorus was turning over as was in solution. McCarter et al, (1952) analyzed the hypolimnetic muds and concluded that the P-^'^ had not pene- trated much beyond 1 millimeter.
The phosphorus picture can be reduced to greater simplicity;
1, The case history of fertilization supports phosphorus as the most essential common fertilizing element,
2, Small quantities exist in natural waters, mainly in two forms, organic phosphorus and phosphate. The former is more abundant, but the latter is more active and often minimal or limiting to productive capacity. Phosphate may become bound in insoluble compounds, and this loss may be related to the alkalinity of the water and to the marl organic matter ratio; of the substrate.
3, Apparently, most phosphate is absorbed directly by lower organisms and indirectly by fish which feed upon them. The direct absorption occurs in minutes or hours. Fauna can concentrate phosphorus in far greater amounts than can flora,
U, The dynamic state of phosphorus has been describerl. The environment
has a great affinity for phosphorus, most of it rapidly entering solids. A continuous phosphorus exchange occurs between water and solids. Since the amount of phosphorus in solution is small, the turnover rate for dissolved phosphorus is more rapid than that for phosphorus in solids.
Nitrogen, as a basic constituent of protein, is necessary for the formation of living matter (Meehean, 1935) • It occurs as a free element (N) , or as amraonia (NH3) , nitrate (NO^) , nitrite (NO2) ; and organic ni- trogen. These form a well-known cycle related to bacterial activity. Nitrification proceeds in the order named, by the action of nitrogen- fixing and nitrifying bacteria. Welch (1935) listed molds and possible algae as nitrogen fixers. Nitrate and nitrite nitrogen (especially the former) are generally accepted as the available forins of nitrogen for anabolic activity of higher organisms, Pennington (19li2) found that cultures of algae and bacteria utilized amraonia nitrogen more rapidly than nitrate nitrogen. Denitrification acts in the reverse order with denitrifying bacteria changing organic nitrogen into ammonia. According to Welch (1935), free nitrogen is barely soluble and enters the water from the atmosphere, Aninonia, he stated, is highly soluble and toxic to fish in relatively small amounts (8 p.p,m.). The nitrate nitrogen con- tent of water is low and usually variable.
Chu (19h3) concluded from laboratory results that nitrogen and phos- phorus occur naturally in quantities far below the upper limit for optimal growth and often do not reach lower optimal concentrations. These ele- ments, he added, may limit growth at certain times of the year and may exert a selective influence on different species of algae when concentra- tions are below the lower optimal limit (nitrogen, 0.3 to 1.3 p. p.m. phosphorus, 0.018 to O.090 p. p.m.). Such concentration limits may not apply to natural situations. Since water is exposed to unlimited quanti- ties of atmospheric nitrogen, Neess (19h9) postulated that nitro.-^en utili- zation is limited only within the aforernentioned cycle.^ which is a system in equilibriu;n, and does not depend upon niirogen addition. There is a possible inverse relation of nitrate-nitrogen and direct relation of organic- nitrogen content of water with productivity (Surber, 19^7). Nitrite nitro- gen and ammonia are indicators of pollution because they posses an oxygen demand (^iS-ebe, 1929). Aerobic conditions in the environment suppress a.m- morda and improve conditions for nitrification.
The value of potassium as a nutrient addendum is also questionable. V/elch (1935) considered it a fixed requirement for plants in food manu- cature and a catalyst occurring, naturally in small amounts (0.5 to 9.0 p.p.m, - Moyle, I9I49) . A slight acid reaction results when its compounds are added to water (Wiesner, 1937) • Swingle and Smith (1939a) found that small amounts of potassium increased pond yields^ but lari,er quantities caused no further increases. Potassium has a most favorable influence in peat,, sand, and hard-bottomed ponds j in mud ponds, it inhibits hard water- flora (such as Equisetum) and favors soft waterflora (SchaeperclauS;, 1933) . Neess (I9li9) stated that results of potassium fertilization are erratic but cited an instance of increased 'production tiy use of potassium alone He concluded that the effects of potassium are indirect, selective, and partly bacteriological .
Compounds of calcium and magnesium, for the most part, function simi- larly in water metabolism. As an individual element, calcium is the more abundant and important of the two, often occurring naturally in large quan- tities. Welch (1935) considered calcium in the following roles i (1) Related to the translocation of carbohydrates 3 (2) an integral component of plant tissue] (3) acts to increase the availability of other ionsj (U) reduces toxic effects of single-salt solutions of other elements. Its presence is obvious in some animal tissue, especially the exc skeletons of arthropods and mollusks. Magnesium, Welch stated, is a component of chlorophyll and, in some instances, acts as a carrier of phosphorus, Wunder et al. (1936) stated that magensium stimulater^ bacterial reduction of organic matter in the bottora„ Cal':ium- rich waters are those draining marl and limestone soils. Schaeperclaus (1933) claimed that he had never encountered a pond too rich in calcium. Surber (19U5) believed waters that acquire hardness by contact with limestone formations may foster growth of Chara that reach great density and curtail fish production. Schaeperclaus (193J) and Welch (1935) discussed the relations of calcium and magnesium to the carbon-dioxide mechanism of water in some detail. The affinity of
10
I
these elements for free carbon dioxide results in the formation of soluble bicarbonates (CA/JcoJL) or half-bound carbon dioxide, and carbonates (CaCO-s) or fixed carbon dioxide. This mechanism is somewhat complex, being related to acidity-j buffering, photosynthetic action, removal of decomposi- tion products, and activation of other nutrients. Calcium may be deposited in large quantities as lime on the bottom of lakes and ponds » Mollusks and certain algae (marl-forming organisms) are important organisms functioning in this process. Calcium nutrition will be considered later in the dis- cussion of liming.
Conflicting opinion is found in the literature on the value of iron in fresh waters. High iron content, according to Schaeperclaus (1933) <• is a phenomenon usually accompanying acid waters, and it presence denotes a poorly productive habitat, Wunder et al. (1936) believed ponds rich in iron and aluminum were good producers and that typically good ponds had bottom soils with autochthonous organic sediments rich in iron and manga- nese. General belief holds that a small amount of iron is necessary^ but that large quantities are detrimental to productivity. Welch (1935) indi- cated that the function of iron lies in chlorophyll production, and that it possibly acts as a catalyst or oxygen carrier. The best algal growth, he stated, is in water having 0.2 to 2,0 milligrams of ferric oxide per liter, but in the absence of buffer compounds 5 milligrams per liter may be toxic. Estimation of the iron content of water may be made from the amount of ferric mud in the bottom (Schaeperclaus, 1933)- The power of iron as a reducing agent accounts for its undesirable activity.
Welch (1935) briefly described the importance of several minor elements. Silicon is a structural component of diatoms and sponges, being soluble in water as silicate. Blooms of diatoms or desmids may cause high fluctuations in the content of dissolved silicon. Sodium supplements the action of potassium and may act as an antidote against the toxicity of some salts. Sulfur is necessary to protoplasm as a constituent of certain amino acids j it may occur abundantly in organic matter or combined with iron in bottom soils. Manganese is esrential in minute quantities to chlorophyll -bearing plants. Zinc and copper are required by protoplasm in small amounts. The former may stimralate plant growth, but both may be toxic in large quanti- ties. This group of elements, with the exception of sodium and sulfur, occur sparingly in natural waters, and little is known about their optimal levels or roles in water metabolism.
Organic compounds are more varied and complex than mineral substances. As previously mentioned, some of the organic matter in lakes and ponds occurs in solution. Welch (1935) discussed the composition and function of this dissolved matter. It is a mixture of many substances (carbohydrates, fats, and proteins), the most prominent being nitrogenous waste products. In natural waters the total amount of dissolved organic matter usually ex- ceeds 10 milligrams per liter. Nutritionally, it is known that some organisms exist mainly on such dissolved material. Largest quantities of undissolved organic matter are found as humus in t he substrate, reaching
11
the botton. via seston sedimentation and settling of plant mattero Meehean (1933) stated that crustaceans and chJ.ronomids may utilize proteins and carbohydrates directly, or through the action of bacteria and protozoa. Not only may organisms grow and multiply at the expense of organic m.atter, but saprophytic activity of bacteria and molds releases soluble organic and inorganic materials. Bacterial activity depends on t he carbon-to-nitro- gen (CsN) ratio of the parent substance, according to Meehean (^-935). It is low when ratios fall below lOsl and good when 20 ;1 or higher. The im- portance of carbohydrates and C:N ratios in nitrt>gen fixation has been indicated by Neess (19ij9) ■ Lawson (1937) and others have pointed out the relation of productivity to the presence of organic matter and have indicatec; the need for it in humus -deficient waters.
The Fertilization Process
Two approaches can be made to artificial enrichment. The first^ nu- tr-ient addition;, is the common and accepted practicej it is what the word "fertilization" ordinarily implies. The second liberation of nutrients present, is a direct approach only in theoryj it operates as a secondary effect in the former method, and has been given little substantial consider- ation as a separate process.
The primary concern of nutrient addition is the nature of fertilizing substances. These are readily classified into two groups: orf,anic and inorganic fertilizers. The composition of several fertilizers, reported in the reviewed literature, is presented in table 1, Prince and Bear (19ii3) listed the nitrogen, phosphate, and potash content of various organic materials that are used or could be used as fertilizers. Complete current analyses of many fertilizers appear in State agriculturel publications deal- ing mth such matters.
Organic fertilizers contain a large percentage of organic carbon in addition to many minerals. These supply most of the elements necessary for metabolic activity and are usable for overall enrichment of waters or as a source of carbon in an organic-deficient environment. Organic fer- tilizers may be in the form of manures, composts, commercial meal residues, or many other organic byproducts, Neess (19U9) explained the advantages of meal fertilizers in terms of their high C;N ratios. Smith and Swingle (19U3) found that organic fertilizers tend to crowd ponds with excessive plant ^^rowthsj especially filamentous green algae (Swingle, 19U7) . Wiesner (1937) suggested the use of composted aquatic plants as an inex- pensive, readily available fertilizer. Swingle and Smith (19^0) recom- mended barnyard manure to clear muddy waters, Hora (1950) stated that the carbon in manures reta ns nitrogen for a longer period than inor- ganic fertilizers and ensures a sufficiency of carbon dioxide and nitro- gen.
Inorganic fertilizers lack organic carbon and are available as single compounds (e, g., ammonium sulfate; sodium nitrate, potassium chloride),
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Table lo Composition of some fertilizing substances
Fertilizer
Composition
Inorganic;
Colloidal phosphate.
Di calcium phosphate. Li mate. ..... o.. .o. o «
Ldme marl„ . . . . . . . . . .
Limestone. .. ....... .
Rhenania phosphate. . Superphosphate.. ...
Thomas meal ........ .
, .... 2$% CaOj 2U% P2O5; 11% SiOg^ h%
Fe2035 small amounts of Mn, Mg., Clj
Fl, Cr, ?a and Na . .... }>% P2O5J 2% CaO . .... h%% CaO| 32^ MgO . . . o , 80 to 90^ CaC03 , . . . . 90 to 9% CaC03 , .... 2$% PjO^j 1|2^ CaO , .... 16 to 20^ P2O5; CaSO[^^ small amounts
of AI5 Sij Fe, Mg, and Fl , .... 13 to 20% P205^UO to S0% Ca05 8 t;^
9% Fe
Organic;
Cottonseed meal,.
Sheep manure ..... Shrimp bran. .....
Soybean meal. ... .
Timothy hay. .................... ..-,
Aquatic plants >, GsN ratios (see Meehean, 1935) Ceratophyllum dermersum. ..... 2 2 „ 8 s 1
=""" ^ '■ ..... 18,6;1
..... 12.3sl
h.0% protein^ 1% nitrogenj 3% P2O51
2% K2O
2% Nj 2% K2OJ 1% P2O5J low in proteins
53^ organic matterj \xh% protein; 1% N (exclusive of NO3) j 2% P
6\% total organic matter; hh% protein.; 2U^ N (exclusive of NO3) ; 1% P
0.8^ N; OM KoO; 0.2^ P2O5
Ceratophylli
Potampg^tcn americanus P. filliformis. ......
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or commercial mixtures expressed in percentage ratios of nitrogen iphos- phorusspptassium (N:P:K) . There are also mineral fertilizers such as superphosphate which contain several minor elements in addition to soluble phosphorus (table 1) .
Since the compositions of inorganic fertilizers are known or easily determined^ they are especially adaptable where definite quantities of nutrient elements are to be applied. Swingle (19^7) found that large amounts of phytoplankton grew in response to inorganic fertilization by virtue of the rapid solubility and distribution of the nutrient substances, but that carbon dioxide was limiting in ponds fertilized only with inorganic materials. In Japanese rice-paddy carp culture^ Hiyama (1950) concluded that organic manures promoted more zooplankton than inorganic fertilizers. Organic and inorganic fertilizers have been successfully used in combination in many instances.
The following list^ adapted from Lavjson (1937), shows the relative con- sumption of different fertilizers in Czechoslovakian pond culture for 1935|*
Lime and limestone , .o„ ... o o „ 1,579 metric tons
Superphosphate , , . , , . , = « . . . 301 '' "
Other inorganic fertilizers. . , , , . 86 " ■'
Manures. ...,,....»..=,. U63 " "
Compost and aqUatic plants ...... 8^0 " "
If such a tabulation Xifere available for fertilizers used in this country, it would undoubtedly show a greater relative consumption of super- phosphate and other inorganic fertilizers^ plus large quantities of meal residues. The world-wide use of either mineral or organic fertilizers is largely a matter of availability. Large quantities of meal and mineral fertilizers are manufactured and thus available in this countrj'^, while Asiatic fertilization (Mora, 1950| Rabanal, 19^0) is limited mainly to the use of locally occurring manures and other organic substances.
Local and regional differences occur in the chemical composition of water and soils. For this reason the selection of fertilizers should be based on the results of chemical analysis of water and soil (Rabanal, 1950s Rounsefell and Everhart, 19^3: Schaeperclaus, 1933) . An alternative or supplementary method of determining fertilizer requirements is suggested by Schaeperclaus (1933) . It consists of inoculating containers of parent water, enriched by various kinds and concentrations of fertilizers with algal cultures. Highest j.;rowth rates indicate the most suitable fertilizer and concentration. Swingle and Smith (1939a) used this method with ap- parent success in early experiments. It has obvious limitations since environmental conditions cannot possibly be duplicated in culture containers. Hasler et. al. (19^1), for instance^ found that the actual lime requirement for the alkalization of a bog lake was 'Tiore than three times the quantity estimated by sample inoculation. Availability, cost, and mode of action
Hi
with respect to food chains may also influence the selection of fertilizers « Fertilizers are often mentioned in the literature for specific conditions and areas (as Swingle and Smithy 1950j Meeheanj 1939)-
Fertilizers are generally applied in the spring of the year when waters grow warm and biological activity increases, European consensus (Schaeperclaus^ 1933| Lawson, 19375 Wiesner, 1937) is that a single large application of fertilizer suffices, and that additional doses are super- fluous o American opinion (exemplified by Swingle and Smithy, 1939a., 1950s Zellerj 1952) is that frequent^ light doses result in higher producti^'/ity and improved conditions. The lack of agreement stems from differences in practice and is significant mainly in fertilizing shallow waters = European fish-cultural methods place greater emphasis on liming (see Fertilization and Pond Culture) and the role of the bottom in pond productivity. Both factions recommend an even distribution of fertilizers over shallow areas. Most fertilizers are dry solids and are distributed as such by broadcasting. Smith (1933), in using this method, produced rapid plankton growth, but a larger total yield resulted when the fertilizer was dissolved from suspended sacks. This possibly may be an important consideration in situations where nutrients are "lost" in the bottom. If a fertilizer consists of several substances, all should be added simultaneously (except caustic lime) to insure proper chemical interdiction (I'fi.esner, 1937) »
The theoretical approach of nutrient liberation has been considered by Hasier and Einsele (19U8) for the activation of phosphate in eutrophic lakes. It is based on the dissociation of phosphorus and iron and their mutual sedimentation as FeP(l at the fall overturn. Two schemes were pre= sented for the rerrcval of ferrous iron. One is the precipitation of ferrous ions with sulfatej amounts of calcium sulfate needed and the ensijing reactions were discussed. Implications of other nutrient liberations are given by Welch (1935) j who noted that magnesium may free calcium and that sodium may release potassium. The cultural practice of draining ponds mobilizes nutrients in accordance with this concept. Since productive increases result in the reduction of bottom soils, draining and aeration cause the oxidation of bound nutrients which, in turn, makes them available the following season. Nutrient release is also one of the major functions of liming (see Fertilization and Pond Culture) o This concept holds that chemical elements are limiting, not because of their absence or paucity, but because of their inability to contribute to anabolic processes. It is an approach to artificial fertilization that may be wort.hy of greater consideration.
Interpretation of Results
Fertilizers act to increase the general productivity of water,, The first and most pronounced effects of these nutrients appear on organisms having short life cycles (Ball, 19U9) . Fish are last to indicate benefits of fertilization, and the quantity produced is the ultimate measure of
15
fertilizer effectiveness. Time, experimental design^ or nature of the environment often necessitates the use of other indices » Moyle (19U9) considered several such measures of lake productivityo Quantitative determinations of plankton and bottom fauna^ creel returns, fish length and- weight increment, relative plant growth, and plankton turbidity are some biological evaluations » Changes in pH may be significant. Surber (I9U7) and Zeller (19$2) suggested that an inverse relation exists between water nitrate and fish growth, Meehean and Marzulli (19h5) contended that huraus loss and C:N ratio of the substrate may demonstrate fertilizer effec- tiveness. Their experiments indicated that lowest humus loss and highest C:N ratios were associated with highest productivity. The authors concluded that humus loss is more reliable, while CjN ratios were valuable because of ease in determination. Many of these secondary indexes are valuable at times, and occasionally necessary, but their reliability when applied to fish pro- duction is questionable. The many variables in operation subject these indexes to extreme critical evaluation.
Wiebe (1929) described aquatic fertilization as "intentional pollution", implying that it may cause unwanted or, perhaps, detrimental changes. According to Hasler (19li7), fertilization involves eutrophication. Many workers have experienced undesirable increases in vegetation, resulting in higher water temperatures and oxygen depletion. Wiebe (I93I4.) pointed out relations between oxygen content and temperature-flora conditions, indi- cating that reasonable amounts of fertilizer \-jill not cause oxygen deple- tion so long as vegetation is alive. Measurements for minimal oxygen should be made at dawn (Hcgan _, 1933) ^ Smith (193lia) noted the extreme chemical and physical conditions tolerated by lower organisms in heavily fertilixed water. Swingle and Smith (1939a) found that ammorium sulfate lowered pH values significantly in moderate to heavy doses „ while sodium nitrate tended to increase the hj'-droxyl-ion concentration,. Certain elements (Cu, Zn, As, etc.) are especially toxic to fish in soft waters, Wiesner (1937) cautioned a,-,ainst the use of large amounts of fertilizers containing toxic substances such as cyanide and ammonia. Undesirable effects of fer- tilization are not limited to chemical toxicity and objectionable flora, but mayresult from the growth of competitive fish or other injurious fauna.
FERTILIZATION AND POND CULTURE
Fertilization had become a part of Eurasian pond cultiire long before it was accepted in this country^ This early development was stimulated by extensive fish-cultural enterprises and their importance In Eiorasian economy Therein is symbolized the basic difference in fish culture be- tween the two continents. In Europe and Asia, the primary aim of aqui- culture is to produce quantities of protein foodc Here, most cultural efforts are concerned with a recreational fishgry. Tha European approach to scientific pond fertilization has been meticulous. Consequently, gen-
16
eral references such as Schaeperclaus (1933) and Wiesner (1937) contain great detail on many phases of pond enrichment. Smith (1932b) considered two cultural concepts of fertilization; (1) Production of zooplankton in greatest possible amounts for removal and feeding to fish; (2) production of food directly in rearing ponds and natural waters. Many early experi- ments were conducted in accordance with the first conceptj mainly because plankton are able to tolerate abnormal amounts of f ertilizer. This view has been super SBded in recent years by the second concept, the direct fertilization of fish ponds.
The Pond and Enrichment Procedure
Physical characteristics, such as depth, size, and bottom type, exist optimally in the culture pond. Many environmental variables (vegetation, rate of exchange, temperature, sunlight, nutrient loss, and population composition and density) are controllable, often to a large degree. Regu- lation of the inflow and outflow affects water temperature, oxygen con- tent, and nutrient retention. Pond-draining facilitates complete crop removal. Small size and shallowness permits effective seining and control of emergent border vegetation. The latter, in turn, determines the amount of direct sunlight reaching the water. For these reasons, a drainable culture pond represents the ultimate in potential aquatic production.
Advantages of f ertilizing such an environment were given by Wiesner (1937) s it is less expensive than artificial feeding^ the resultant natural feeding causes rapid growth and low losses due to disease and nu- tritional deficiencies; fish can then tolerate grt^ater population densities. The rearing of brood trout in fertilized ponds, Wiesner added, is uniquely advantageous. Initially there is a plankton bloom upon which fry feed and, as the season progresses, larger food organisms produced correspond to changes in diet of the growing fish. Meehean (1933) further concluded that large fish can be produced at earlier maturity, and the shortened growing season saves space and overhead.
Fertilizers are selected to suit the needs of the pond after considera- tion is given to the quality of the water and bottom soil. Swingle and Smith (19^0) recommended 100 pounds of 6:8:U and 10 pounds of sodium nitrate per acre-application. Schaeperclaus (1933) suggested using 35 pounds of phosphate (T^Or) per acre alone, or with h^ pounds of potash (KpO) ,. Wiesner (1937) advised similar araounts of phosphate (l80 to 270 pounds of super- phosphate per acre) as effective and economical. Surber (19li7) tabularly listed amounts of some single inorganic fertilizers needed to prepare vari- ous NsP:K combinations. A list of fertilizers and the papers in which they were reported is given in the appendix. Fertilizers are spread over the bottoms of drained ponds before spring filling. They are applied to filled ponds by broadcasting from shore or boat over shallow areas. American theory recommends periodic applications throughout the growing season at intervals governed by temperature, plant growth, and oxygen conditions in the ijater. This maj'' be each 2 weeks in spring and at monthly intervals
17
during the summer. Smith and Svdngle (I9U1) concluded that vnnter fertili- zation of blue^i^ill ponds in the South is inadvisable because of slow fish growth in that season.
The recommendations given here are generalized and may not apply to specific cases. Nelson (I9UI), for example, found that the addition of fertilizers to shallow ?rras disturbed spawning beds and hindered the sein- ing of bass fry. This difficulty was eliminated by applying the entire amount of fertilizer to the center of the pond. Rounsefell and Everhart (1953) believed that investigators usually place excessive emphasis on a single factor with the result that recommendations and conclusions concern- ing pond fertilization vary without reason, and the process reverts to trial and error in different localities.
Techniques Contributing to Maximum Production
Fertilization, although specifically a problem of nutritional chemistry, has other considerations of equal importance. Draining the pond, as pre- viously indicated, oxidizes bottom soils and facilitates crop removal. In addition to these functions, it permits control of aquatic vegetation and competitive or injurious organisms. Ponds are usually drained at the end of the grovring season and are allowed to overwinter in fallow (Schaeperclaus, 1933). Nutritionally poor bottoms may be seeded with a legume in early spring and the crop plowed into the soil when in bloom.
Liming e considered the first step in pond fertilization (Schaeperclaus, 1933; Jiesntr, 1937). Strictly speaking, it concerns the addition of caus- tic liiae (quicklime, slaked lime, or calcium cyanamid (see Appendix A) to the pond bottom when in spring fallow. Liming serves the following pur- poses:
1. Kills, by caustic or caustic and toxic action, the eggs and inter- mediate stages of fish parasites and some plants.
2. Raises the pH of water to a level most favorable for fish health and metabolic cycles of the pond.
3. Raises the A.C.C. of the water and creates a carbon-dioxide reserve.
Ii. Insures sufficient calcium for plant and animal nutrition; for the building of carapaces and shells; and for the detoxification of soluble sodium, magnesium, and potassium compounds.
5. Ameliorates the bottom (aids mineral decomposition, liberates potassium, hastens soil decomposition, lowers oxry-gen consumption).
6. Eliminates strong excesses of putrescible organic matter (which demand oxygen and provide favorable conditions for the existence of many disease instigators).
18
Liming is preferably done about 2 weeks before the addition of ferti- lizers^ to avoid binding nutrients in insoluble calcium compounds. The degree of caustic action desired^ and the activity of the soil vary the dosage from 90 to 3^0 pounds per acre. Liming^ in a more general sense, covers the addition of noncaustic lime compounds (limeston8_, lime marl) which may accomplish all purposes except the first. Such lime may be included with the fertilirers. Sandy bottoms and calcium- rich waters may derive little benefit from liming.
Proper stocking, as to species composition and numbers^ is essential for maximum productivity. Stocking, tables can be found in the literatures
Schaeperclaus (1933) = . <■ comprehensive Wiesner (1937) , , , o , « salmonids Swj-ngle and Smith (19^0) , pondfish
The fishes involved in fertilization work are listed in the appendix with references to the papers in which they appear. The total yield of fish per unit area varies, as does stocking density, with species and population composition. Generally, oroductive increase in enriched oonds is' reckoned at 100 percent over unfertilised ponds. This may be expected to vary considerably in different geographical locations and with different types of fis^i. It is readily understandable why omnivorous carp can be produced in greater quantity than can carnivorous fish such as bass. Maxi= mum yields of carp and related species in Asiatic countries., as cited by Hora (19^0), generally range fron 2,000 toU^OOO pounds per acre per year. On the other hand, Sid.ngle and Smith (195o) claimed that fertilized Alabama ponds produce UOO to 600 pounds of sport fish per acre compared with I4O to 200 pounds per acre in unfertilized ;)onds. Properly fertilized waters in our northern latitudes may show only 30-percent increase over control ponds because of the shorter growing season.
Conclusions on Pond Fertilization
Experiments in pond enrichment have ^^enerally revolved about the testing of common fertilizer t,-;T3es and concentrations relative to the pro- duction of food organisms and various species of fish. In these trials, near-isomorphic ponds have been used as typical test and control units. Some experimental work, of course, has not followed this pattern, Hender- son (19li9) tested the value of manganous sulfate as a plant stimulator, and was apparently successful in oroducing the desired algal blooms with concentrations of 0.1 and 1,0 part per million. Walker (I9I49) failed to Increase production by adding limestone to acid ponds. Weed control by fertilization has been an interesting sidelight. Surber (I9U?) found that hay plus superphosphate effectively controlled overabundant flora. Organic and organic-plus-superphosphate fertilizers produce heavy algal growths which can be destroyed by sodium-nitrate applications 5 according to Smith and Swingle (19U3) , Patriarche and Ball (19149) were unable to control algae as suggested by these authors. Productive increases of fish have
19
not always been attained, as shovm by Ball (19li9) , who increased the abundance of plankton and botto.-n fauna without significantly affecting the fish yield.
Implications which may be drawn from piscicultural literature resolve the subject of pond fertilization into two components:
1. Cultural aspect. A culturist need only have the fertilizers, ponds, fish and the objective of fish production. Fertilizers are appHed in advised amoimts according to recommended procedure. Results will vary^ but by altering the type and quantity of fertilizers the culturist will arrive at increased yields of some consistency within a few years. Ii/hen the increased production overbalances the cost of fertilizers and fertilization, success is achieved. Knowledge of pond metabolism is not essential, nor is it useless. An understand- ing of the causes and effects of changes due to nutrient addition will enable the culturist to produce more fish at less expense and with greater consistency.
2, Experimental aspect. This is explained and related to the above by Meehean (l939,pJ.) . Referring to the cult^urist's view of scientific investigation, he stated, "They (culturists) are not conscious of the fact that results frnm such a study are dependent upon the vagaries of nature and not produced at will as a series of chemical experiments might be. It has not been realized that many problems such as the social reactions of the fish, how they feed, how the food organisms are produced, what food chain from the organic com- pounds to fish is the most beneficial, what fertilizer will best stimulate this food chain, must first be solved in order to know what is happeningt. In other words, one must get to the fundamentals of the reactions of the fishes and their relation to food in order to offer an intelli{-;ent solution to the nroblem. We are still a long way from that final solution." Other problems more intimate to nu- tritional enrichment, might be added to Meehean' s list. The solu- tions have not yet been compounded and remain to be reached only throutih careful experimentation. Therein lies the need for experi- mental fertilization.
Piscicultural trends in the United States are directed toward sport- fish production and, since protein food is abundant, no serious efforts have been made to produce food fish. The phenomenal annual jrields of 1 to 2 tons per acre found in European and Asiatic carp c ulture cannot be ex- pected under our cultural methods. The ecology and food ha'its of our sport fish, together with the cost of f ertilizatlon, limit the extent to which this method of production gain applies. Rounsefell and Everhart (1953), considerint, the use of commercial fertilizers, estimated the cost of fertilizing shallow oonds at l5 to 20 dollars per acre per year. At that rate, without complete assurance of satisfactory results, artificial enrichment may not be profitable. Present needs seem to call for the de- velopment and standardization of fertilization methods in pond culture, rather than the promotion of fertilization as now practiced.
20
FARM FISH PONDS
A great deal of literature has been published in recent years on the construction, maintenances and management of fferm fish ponds. Apparently the public has been convinced of their practical, recreational, and con- servational value. In response to such publicity, innumerable farm ponds have appeared in various parts of the country. Fertilization is one of the management practices commonly recommended and much pioneer work to that end has been done in Alabama by H. S. Swingle and Ms collaborator, E. V. Smith. Several of their reports are cited in the "List of References",
A discussion of farm fish ponds as environmental entities related to artificial enrichment is felt unnecessary because such treatment would mere- ly overlap the preceding and subsequent sections of this report. Informa- tion gleaned from farm-pond literature has already been presented and the reader is referred to thosfe publications for more direct and pertinent data.
One important issue, the practical value of fertilizing farm ponds, is open to question. One might assume, after reading some of the litera- ture, that fertilization is an essential phase of proper farm fish pond management. However, fish rearing in farm ponds is not intensified as in culture ponds, nor is it done for a marketable crop. Published reports do not indicate the extent of harvest in farm ponds, but it is probable that few of them are adequately cropped. Therefore, unless serious effort is made to harvest the fish, it seems unwise to recommend the fertilization of farm ponds where costs are involved.
FERTILIZATION OF LAKES
Thus far, specific discussion of aquatic environments has been mostly limited to d^einable culture ponds. Delicate experiments in aquatic nutri- tion have been conducted in laboratory containers where many natural varia- bles can be eliminated or controlled. Much fertilization literature is de- voted to farm fish ponds, and some to trials in lake enrichment. .These dif- ferent types of lerlitic habitats can be arranged in a sequence of increasing environmental conplexity, paralleled to a large extent by increasing size and depth. The simplest is a laboratory receptacle, followed by outdoor pools, drainable culture ponds, nondrainable culture ponds, farm fish ponds and natural ponds, small shallow lakes, and, finally, larger lakes of in- creasing physical and biological diversity. Notable changes occur in this progression when it is considered from an enrichment point of view. The first appears when the artificial retaining structure is replaced by natural soil. A second important break exists between drainable and nondrainable waters. A third of probable importance coincides with thermal stratifica- tion. The second and third major changes in the nutritional succession indicate basic differences between culture ponds and lakes so far as this paper is concerned, and will be considered with other factors in the follow- ing sections.
21
The Environment and Artificial Enrichment
Ponds and lakes differ in size, depth^ and degree of control that can be exerted over many variables. Increasing size and dapth imply decreas- ing productive capacity (relatively) ^ and decreasing economic feasibility for fertilization (Hasler, 19ii75 Smith., 1952). There are obvious limita- tions in depth and area of a f ertilizable lake. The inability to control several important factors is also discouragingo Added nutrients may be carried away in lakes having a rapid rate of exchange. Affluents may bring allochthonous nutrients into a lake in beneficial quantitieSj but may also carry toxic substances and excessive nutrients to cause eutrophication. Most lakes cannot be drained to derive the many benefits attributable to that process o~/ Plant and animal populations are established, and controllable only to a limited extent. This is disturbing in that the populations not only affect fertilization, but may be affected by it in various and some- times undesirable ways. Fluctuations in abundance of organisms irrespective of enrichment are difficult to fathom, and insert a question into the inter- pretation of fertilizer effects. Finally, the crop removal is rather indefi- nite, being subject to the pressure and effectiveness of angling.
Thermal stratification, for purposes of fertilization, divides a lake into a trophogenic epilimnion and an oxygen-deficient, tropholytic hypo- limnion which may entomb nutrient elements by permanent sedimentation. Hutchinson and Bowen (19^7) found that U? percent of the phosphorus intro- duced into a small lake had descended below the thermocline before it could be utilized in the biological cycle. The fall overturn serves to disperse oxygen and dissolved substances throughout the lake, and thus reverse the tropholytic processes occurring in the hypolimnion during summer stagnation.. However, it may also cause the precipitation and consequent loss of valuable nutrients. The spring overturn acts similarly, but since it follows mild winter activity, nutrient loss is not as great. The subsequent warming of water in the presence of abundant nutrients causes increasing biological activity. The thermocline, then, is significant because it diverts or consumes many nutrients which would otherwise contribute to the productive metabolism of the lake.
It would seem desirable here to discuss lakes in the common (but somewhat arbitraty) grouping of oligotrophia, eutroohic, and dystrophic. By doing so, many related chemical, physical, and biological factors could be considered in conjunction with results of lake= enrichment attempts. However, supporting data in reports of lake fertilization are not detailed enough to warrant this distinction,, Reports are summarized below in t.wo groups s lakes supporting warm water fishes (warm-water lakes), and lakes supporting salraonids (cold-water lakes) . Herein the separation is purely mechanical J it may be of significance when more lake experiments have been
2/ Certain impoundments are capable of being drained. In such circiunstances, an increase in productivity has been noted after dry fallow^ refilling, and restocking.
22
performed. This division is based on the general contentions that warm- water fishes can tolerate greater population densities and physico-chemical extremes J that warm-water fishes occur in lakes of higher temperature which signify higher metabolic rates and^ perhaps, greater productivity; and thatj Qther things being equal, warm-water fishes respond more readily to fertili- zation.
Experiments in Lake Fertilization
Pioneer work in scientific lake enrichment was done by Juday et al. (1938) on a 39 "acre, UU-foot (maximum) depth, seepage lake containing small- mouth black bass and yellow perch. Various fertilizers were added over a 5-year period as follows: 1932, superphosphate; 1933> superphosphate and lime; 1931, superphosphate, lime, and ammonium sulfate; 1935^ potassium chloride and cyanamid; 1936, soybean meal. The effects were studied in terms of dissolved ions, plankton quantity, and growth rates of perch. Initially, the water was "very soft" (0.7 parts per million calcium). Added nutrients raised the water levels of phosphorus, nitrate, and calciiom, but only the latter remained above prefertillzation level. Plankton content and perch growth did not chan^^e significantly until after the 1936 fertili- zation, whereupon a sharp increase was noted in both. These biological Indexes continued high the following year and the authors concluded that organic matter was more effective than mineral fertilizers used singly or in groups. Therefore, the organic content of the lake appeared to be limiting.
King (I9U3) reported the fertilization (6:9;3 and sodium nitrate) of a shallow, acid (pH 5,2 to 7,0), 21-acre lake containing largemouth bass, bluegill, and several types of coarse fish. Productive changes were studied in terms of fishing returns (average catch per hour, average creel weight, and pounds per acre caught) . Comparison of these indexes before and after fertilization showed a decrease in fishing returns, bub the drop was not as great in the fertilized lake as in a nearby control lake. Ball (1950) and Ball and Tanner (1951) fertilized one of two adjacent shallow seepage lakes containing several species of warm-water fish. Inorganic 10; 6:1; was added at 3-week intervals. May to mid-September, at the rate of 100 pounds per acre, in I9U6 and 19U7. Definite plankton gains followed each applica- tion and growth rates of t^me fish showed significant increase. Heavy algal mats, which restricted spawning, formed during the second summer. Neither lake had experienced a winterkill within 10 years before fertiliza- tion, but anaerobic conditions under a winter Icecap caused the destruction of most fish and insect life in the fertilized lake following the second year of nutrient addition. The fertilized lake was restocked in I9U8 and the fish grew rapidly. Filamentous algae presented no further problem, and plankton blooms did not occur in the ensuing summer. Surber (19it8) successfully fertilized a UU-acre recreational lake with 5slO;5 and lime, to control nuisance excesses of submerged aquatic plants o It was also noted that fishing inproved.
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More cold-water lakes have been fertilized than the above-mentioned warm-water lakes » Perhaps this is because they are "poorer producers", lower in mineral solutes, and therefore considered better enrichment poten^ tialso A superficial fertilization of the centrally located lake m a chain of three, with l5 tons of sea mussels, was reported by Smith (1931). Marked plankton increases in the fertilized lake, and in the lake below it, were noted the following year„ Taylor (I9UI1) discussed the fertilization of a clear-.vater, sand-bottom trout lake with 1^:8:10 plus calcium carbonate, indicating a large increase in trout weight attributed to fertilization. The content of these reports does not justify more than passing comment.
One phase of a trout investigation project, reported by Wales (19$0), involved the organic enrichment of a clear, deep (120 feet^ maximum), alpine cligotrophic lake supporting four species of salmonids and some forage fish„ Pretreatment water analysis showed 3U parts per million total dissolved solids, a hardness of 23 parts per million, and a pH near neutralityo Cot- tonseed meal was selected on the basis of promising results shown by Juday et al„ (1938). The only apparent change was an increase in turbidii.y im- mediately following fertilization. Langford (19^0) fertilized four deep lakes, thermally stratified, with inorganic 12;2li:12 at monthly intervals. This preliminary report considered detailed changes in plankton abundance. A definite increase in phytoplankton occurred within 3 weeks to 1 month after nutrient application, and it appeared that only a single spring addition was utilized by these organisms. In conjunction with the fertil- ization of a warm-water lake (discussed above). Ball (1950) reported the artificial enrichment of one of a pair of sand-bottom trout lakes. As in the warm-water lake, excessive summer growth of algae fostered winter anaerobiosis which caused the d eath of fish and insects in the f ertdlized lake.
The fertilization study of a shallow, soft-water lake containing brook trout and four species of rough fish was made by Smith (19U8a^ 19USb) , A single application of ammonium phosphate and potassium chloride in late spring caused a zooplankton bloom which disappeared later in the season dur- ing a bloom of Anabaena, Postf ertilization observations within the same year showed an increase in bottom fauna, oxygen saturation, and carbon-= dioxide reserve over pref ertilization levels. Water phosphorus remained somewhat above normal during the season. Indications of increased trout gi'owth and angling success were obtained the following season (I9h7' when the yield of trout to anglers (3=6 pounds per acre) more than doublea the average returns for a 2=year period before nutrient addition. This was attributed to catches of rapidly growing stock fish (60 percent of total catch) which previously grew slowly and constituted only a sm,all part of the creel returns. Observations in t he succeeding years (Smith, 1952) showed a decline in fishing returns. The author concluded that further benefits to trout were masked by predators which also profited from the nu- trient enrichment, and that predator control plus a supply of trout to cap- italize on the increased food supply are requisites for successful fertilization.
2U
The alkalization of two brown-water bog lakes has been reported recently by Hasler et al, (195l) » Objectives of this investigation were to neutralize the acidity (pH 5oii to 5o6) and increase light penetration by the precipitation of humic colloids as lime humate. The addition of limate and calcium carbonate to the water brought pH to neutrality, increased the carbon=dioxide reserve, light penetrationj total phosphorus, and organic nitrogen,, while the ammonia and nitrite nitrogen^, iron, and sulfate content were decreased. These effects were more pronounced in the lake that received heavy lime applications early in spring than in the one that received pro= longed applications throughout the summero Cost was about 60 cents per acre- foot.
Shortcomings are evident in these lake=f ertilization reports. In gen- eral appraisal of work done, it might be said that treatment preceded diag- nosis, Pretreatraent data, necessary for the interpretation of fertilizer effects, were weak and insufficiento Post-treatment observations were more numerous and carefully done, but were not of the quality and quantity demanded by the situation. Proper consideration was not given to the many variables that affect the intricate mechanism of nutrient enrichment. Thus, conclusions reached were often either assumptive, or too broad to contribute information of significance.
Conclusions oft Lake Fertilization
Similarities occur in the effects of fertilizers in lakes and in ponds, as might be expected. Population increases were rapid and most pronounced among the lower organisms. Single species, rather than whole groups, tended to show greatest gains,. Nutrients disappeared rapidly from solution, ap- parently through deposition in bottom soils and uptake by living organisms. Lake-fertilization results differed from those of ponds in that less notice- able changes occurred after the addition of nutrients, especially to fish life. The effects of fertilization on fish were not included in the reports of Smith (1931) s Langford (19^0), and Hasler et al. (19^1) . Fish did not benefit from the first h years of lake enrichment described by Juday et al (1938), or in the experiments performed by Ball (1950) and Wales (19^0) . Nutrient applications were of questionable value to fish in two cases (Juday et al., 1938| King, 19U3) ., while Taylor (19hh) and Smith (19h8b, 1952) indicated definite growth increases. All in all, fish may have pro- fited from fertilization in one warm-water and two cold-water lakes. The biological destruction of two lakes by the artificial enrichment described by Ball (1950), and Ball and Tanner (19^1) demonstrates a possible pitfall in tampering with the natural metabolism of lakes. Perhaps there have been other negative attempts at lake fertilization which, although noteworthy at this time, have not been r eported. In concluding the various results, it can be said that fertilization increases at least part of the productive capacity of lakes, but not necessarily the yield of fish. It is possible that fertilization may become a valuable technique in raising the productive levels of some lakes, and an important method of studying the biological interactions and little-known chemical relations of lakes in general,
25
The practical success of artificial lake enrichment demands a consis- tent increased yield of desirable fish to angler. Assuming that productive capacity of a lake can be enhanced by fertilization, it is necessary to examine the possible effects of f ertilizers on the principal objectiveo Some concepts of increased productivity, based on hypotheses in Province of Quebec (19hQ) s which do not insure practical success are —
lo A general increase in the abundance of plants and animals to the extent of complete eutrophi cation, and resulting destruction of the fish populationo
2, A decrease in the population of desirable fish owing to overcrowd- ing by excessive growth of submerged flora,
3, A decrease in total population of desirable fish by the gain of a few large cannibalistic individuals, or by increase in the popula- tion of coarse fish,
iio An increase in population of desirable fish with individuals too small to be utilized.
5. An increase in population of desirable fish with individuals of usable size^, but a lower yield to anglers caused by excessive natural food or difficulty in angling (surface blooms, littoral vegetation) »
Other concepts could be added to this list but it is intended solely to indicate effects which deserve consideration in the planning of a lake- fertilization programj and in the interpretation of results, A hypothetical situation demonstrates the flaws in some conclusive reasonings Suppose that a lake containing a population of undersized fish was fertilized to increase the size of its fish. Due consideration was given to several chemical and biological factors. Fertilizers were selected and applied according to recommended procedure. Post-treatment determinations showed improved chemi- cal conditions and a general increase in plant life, nannoplankton^ benthos fauna, or other indexes used in the study. Fish growth was carefully watched but. alas, there was no change. Although the number of fish may have increased owing to conditions which allowed a greater population density, the investigator erroneously concluded (on the strength of his data) that no benefit to fish resulted from the addition of nutidents ,
A lake is a sizable and complex environment, often reacting indepen- dently or adversely to efforts in its management. The fertilization of a lake poses an impressive problemo Cost of enrichment, in terms of net fish yield, may be prohibitive; this is especially true of deep oligotrphic lakes. Experience gained from pond fertilization shows that a single ap- plication will not keep productivity high indefinitely. Rather, fertili- zation requires the renewal of nutrients at least annually, especially if the crop is regularly removed^ What, therefore, is the basis for the arti- ficial enrichment of a lake? The stimulus must be either an explicit
26
demand for no re fish or the need for more knowledge of lake metabolismo Considering the low degree of success in past lake-enrichment attempts, the demand for greater fish crops through lake fertilization is seemingly- inadequate to justify the process in this country at present. If artifi- cial enrichment is to be applied to the study of lake metabolism^ experi- mental d esigns must be more rigid than those used in past investigations in order to procure results of greater significanceo Hasler and Einsele (I9U8) stressed the importance of scientific approach to lake fertilization, A thorough limnolo^-ical investigation should precede enrichment o A few lakes should be tested over a number of years, or several proximate lakes in a shorter time. Inherent variations in chemical and biological con- stituents among the lakes 5 and normal fluctuations of these factors within each lake must be considered. The experiment should then test a minimum number of factors in such a manner that the results will be clear and will lend themselves to statistical interpretation.
SUMMARY
1, Artificial enrichment and the environmental factors associated with it are treated in order to describe the fertilization pro- cesses and relate them to various fields of fresh-water fisheries, The literature reviewed is largely North American, but pertinent Asiatic and European reports are included,
2, The fertilization mechanism involves many physical, biological, and chemical factors which are complex and interrelated in the aquatic habitat. Recognition of such factors is essential to sound planning and interpretation of enrichment experiments.
3, Heat, light, and dimension are the most important physical con- siderations. The first two function mainly in photosynthetic activity, upon which rests the fate of higher fauna. Heat and light exposure of the water are limited by geographical varia- tion in growing season^ occludent vegetation, and turbidity. Small size and shallowness of the environment signify greater relative productivity,
ii. Biological components of a lake or pond may be classified as either producers (flora and microfauna) or consumers (macro- fauna) and form various food chains from nutrient matter to removable fish crop. A fertilization program should consider such successions and operate through the most direct route to fish production. Organisms that do not contribute to the suc- cess of enrichment should be suppressed. Bacteria are of singular importance in bridging the gap between nutrient matter and other organisms. Fluctuations in abundance, a characteris- tic of plant and animal populations, may result from or occur
27
independent of fertilization. The objective of artificial enrich- ment is productive increment, considered here in tenns of yield of desirable fish per unit area and time,
5c Chemical considerations of the environment concern the presence and reactions of nutrient elements or compounds, and their rela- tions to living organisms. Since the substrate is chemically and biologically active in shallow water, fertile soils signify high productivityo Productive waters are generally rich in dis- solved substances and have an alkaline pH (7.0 to 8.5). Many chemical elements are required for the sustenance of life but only four (nitrogenc, phosphorus, potassium, calcium) and organic matter have been widely used in aquatic fertilization. Whether these ele- ments limit productivity is a controversial matter, but most authorities agree that phosphorus is usually limiting in natural waters, and is the most valuable fertilizing element.
6. Phosphorus functions as an assimilator of nitrogen into cellular material o It occurs naturally in a dynamic state, the dissolved component (organic and phosphate phosphorus) being smaller in quantity with a consequent faster turnover rate than the phosphorus in solids. Soluble phosphate is absorbed directly in a matter of minutes by lower organisms, and can be concentrated in large amounts by fauna. Since it is an active element, phosphorus may confcine with iron or calcium and be lost by permanent sedimentation - of insoluble phosphates.
I. Nitrogen, a constituent of protein, is found free and combined
(NH3, NO25 NO3, and organic nitrogen) in the water. These forms of nitrogen are related in a cycle energized by bacterial activity. Nitrate is generally regarded as available nitrogen, but lower organisms may also utilize nitrite and ammonia nitrogen.
80 Calcium and magnesium function similarly in the, complex carbon- dioxide mechanism of thewater. Individually, calcium i s the more in^jortant element, often the major precipitate and dissolved cation in waters draining lime-rich soils. It functions physio- logically in plant tissue, is a prominent structural member in faunal groups, and, in general, ameliorates chemical conditions in the environment. Magnesium is not so abundant, but is neces- sary for chlorophyll production and may aid bacterial reduction in the substrate.
9. Potassium is the most beneficial of the remaining elements,
especially to submerged flora. As a fertilizer, its effects are indirect and selective, and its reactions are most favorable in bottoms of peat or sand. Functions of other mineral elements are discussed.
28
10. Organic matter is necessary for a high productive capacity. It occurs in solution^ in suspension, and deposited in the bottom. These complex compounds result from excrax,ory proces- ses and decomposition of plant or animal matter. They are the source of energy for bacteria and become transformed into usable nutrients by the saprophytic action of such organism,s. The ratio of carbon to nitrogen has been related to levels of bacterial activity,
11. The addition of nutrients to directly increase production is the common approach to aquatic fertilization. It concerns the selec= tion and application of mineral or organic fertilizers to best suit environmental needs ^ in order to attain highest productivity, Availabilityj cost^ amount, mode of action, method, and period- icity of application of fertilizers are factors to consider, A second approach considers nutrient limitations due to lonavail- ability. This theory operates in the fish=cuJ.tural practices of draining and liming_, which mobilize nutrient md. erials held by chanical retention in reduced bottom soils or inactivation due to adverse environmental conditions. As a direct approach^ nutrient liberation exists only in theory,
12. Fertilizers cause a general increase in water productivity, and various indexes (both biological and chemical) have been applied to measure their effects. Such measurements are subject to the vagaries of man and nature^ and must be viewed critically. Enrich= ment may not aid the desired end of fish yield because of undesir- able changes (lowered pH, toxicity, oxygen depletion) or diversion of nutrient matter into nuisance animal and plant growths,
13. Factors affecting fish yield, such as suTxlight_, temperature, rate of water exchange, fish populations, and plant- growths, are con- trollable to a certain extent in a culture pond. Control plus optimum dimensions result in high productive capacity and render such ponds very profitable for fertilization. Cultural fertili- zation is said to be more economical than artificial feeding, the natural nutrition enabling greater population density and result- ing in hardier fish. Recommendations as to type and quality of fertilizer for general enrichment can be found in the literaturej but do not apply in all instances. Nutrients are added before or during the growing season and must be renewed at least annually
to svistain yields,
111. Draining, liming, and proper stocking should be considered in order to realize the greatest productive effects of fertiliza- tion. Draining facilitates crop removal and control of undesir- able plants or animals. Winter fallow oxidizes bottom soils, thereby activating nutrient substances o Liming, strongly recom- mended by European culturLsts, kills disease instigatorsj raises
29
buffer effect and pH of water; provides calcium for nutrition; and aids in detoxification, amelioration, and nutrient release. Correct stocking as to species composition and number is essen- tial. Proper fertilization and accessory techniques usually boost fish yields to 100 percent or more over unfertilized ponds.
15. The numerous pond-fertilization reports duplicate or parallel each other in many instances, but indicate two aspects of pond enrichments Cultural fertilization deals strictly with produc- tion of fish by varying the type^ quantity <, and rate of applica- tion in order to arrive at consistently high yields. Experimental fertilization considers intricate problems of hydro-chemistiy and biota-nutrient relations which can be explained only through careful experimental studies o
16. Sport-fish yields from cultural efforts in this country, comparable to the high production of food fish from fertilized Asiatic and European ponds, cannot be expected. High cost of fertilization and lack of assured success call for the d evelopment of better enrichment techniques in our pisciculture.
17. Farm fish ponds are not discussed in detail, to avoid repetition of information considered elsewhere in the report. Since these ponds are established for a recreational fishery and may not be cropped properly, a question is raised about the practical value of fertilization involving cost.
18. As aquatic habitats increase in size and depth, they become more complex and less practical to f ertilizeo The average fish yield in lakes is only a fraction of that in culture ponds. Besides dimensional drawbacks, features of lakes that discourage fertili- zation are lack of control, established populations, nondrainabil- ity, thermal stratification, and indefinite harvest.
19. Conclusions drawn from 11 lake-fertilization trials indicate
that fish may have benefited from enrichment in only three experi- ments. Effects of fertilization were more pronounced on lower organisms, especially single species of plankton. Stimulated growths of waterflora have caused winterkill upon decay. Although the fertilization of lakes has increased their productive capacity, its practical success in terms of net fish yield to anglers is doubtful. End effects of lake enrichment must be viewed cautiously with regard to the many variables of the environment.
20. Sport-fishing returns of lakes are not comparable in monetary value to the yield of fish flesh in pond culture. Lake fertili- zation, at present, can be a method of studying water metabolism with results possibly applicable to a future program of enrich- ment that would raise the productive capacity of some lakes. If clear-cut, significant data are to be obtained, such scientific studies need sound experimental design.
30
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Literature Cited in Text
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3U
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Other Literature Reviewed
Brown, W,
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1925. The forms of nitrogen found in certain lake waters. Jour. Biol. Chem., 63 (2) J 269-285.
Hayes, F,
1951. On the theory of adding nutrients to lakes with the object of increasing trout production. Canad. Fish. Cult., 10s 1-7.
36
Hofstedej A» E.
19^0 o Pond culture of warm-water fishes in Indonesia. U. N, Scien- tific Conference on the Conservation and Utilization of Resources^ Vol. VII, Wildlife and Fish Resources. 1950 . II. B. 8s 136-138.
Hogan^ J.
19U9o The control of aquatic plants with fertilizers in rearing
ponds at the Lonoke Hatchery, Arkansas. Trans. Amer. Fish. Soc< 76s 183=189.
Howell, Ho
19U2. Bottom organisms in fertilized and unfertilized fish ponds in Alabama. Trans, Amer, Fish, Soc, 71 J 165-179.
Hutchinson, G.
I9UI4, Limnological studies in Connecticut. VII. A critical example of the supposed relationship between phjrto plankton periodicity and chemical changes in lake waters. Ecology, 2$ (l) ; 3-26.
Juday, C.5 E. Birge, G, Kemmerer, and R. Robinson
1928. Phosphorus content of lake waters of northeastern Wisconsin. Tran: , Wis, Acad, Sci,, Arts, and Lett., 23: 233-2i|8.
Leach, G,
19360 Fertilization of bass and daphnia ponds. Prog. Fish-Cult,, 16s 13-15,
Leim, A,
193h, U, Fertilization of ponds, Ann, Rpt., Biol. Bd. Canad., Atl, Biol. Sta,, N.B,: 11, 12.
Lin, S, Y,
1950. Pnnd culture of warm-water fishes. U.N« Scientific Conference' on the Conservation and Utilization of Resources, Vol. VII, Wildlife and Fish Resources. 1950, II. B. 8s 131-135.
MacFadyen, A.
19U3. The meaning of productivity in biological systems. Jour, Anim. Ecol., 17s 75-80,
Meehean, O.L.
1950. Pond culture of warm-water fishes as related to soil conserva- tion. U.N, Scientific Conference on the Conservation and Util- ization of Resources, Vol. VII, Wildlife and Fish Resources. 1950. II. B. 8s 138-lli2.
Mortimer, C,
1939, Physical and chemical aspects of organic production in lakes. Ann, Appl. Biol., 26 (l)s 167-172.
37
19U2. The exchange of dissolved substances between mud and water in lakes. Jour. Ecol., 30 (1): 1^7-201.
Pearsall, W.
1932. Phytoplankton in English lakes. II. The composition of phyto- plankton in relation to dissolved substances. Jour. Ecol.^ 20 ^2): 2U-262.
Pearson^ A.
19hS. How to manage your fish pond. Ala. Polytech. Inst., Ext, Serv. Circ. 325, 8 pp.
Shelubsky^M.
19^0. A review of fish farming in Israel. U.N. Scientific Conference on the Conservation and Utilization of Resources , Vol, VII, Wildlife and Fish Resources. 1950. II. B. 8; Ih7-l50.
I
Smith, M.W.
1930. Investigation of the Chamcook series of lakes. Ann. Rpt.,Biol. Ed. Canad., Atl. Biol. Sta., N.B.: 30,31.
1932c. Fertilizing water with herring meal. Prog. Rpt. No. 3j.Atl. Biol. Sta., Biol. Bd. Canad., Note No. 13: 7-9.
1932d. Oxygen in water affected by fertilizing. Prog, Rpt. No. U, Atl, Biol. Sta., Biol. Bd. Canad., Note No. l8s ll;,l5.
193Ub. Fertilization of ponds. Ann. Rpt., Biol. Bd. Canad., Atl, Biol. Sta., N.B.
193hc. The dissolved oyxgen content of fertilized waters. Trans. Amer. Fish, Soc, 6U: ho8-Ul5.
1936. Rearing speckled trout in fertilized water. Prog, Rpt. No. 17, Atl, Biol. Sta., Biol. Bd. Canad. Note No. 52, 10, 11,
1938, Rearing of trout in flooded or fertilized ponds, Ann Rpt. Fish. Res. Bd. Canad., Atl. Biol. Sta., N.B.
Snieszko, S.
19itl. Pond fish farming in Poland. Symp. on Hydrobiol,, Univ. of Wis. Press, pp. 227-2iiO.
Swingle, H., and E. Smith
1939b. Increasing fish production in ponds. Trans. Uth N. Amer. l/fi-ldl, Conf.: 332-338.
19[tl. The management of ponds for the production of game and pan fish, Symp. on Hydrobiol., Univ. of Wis. Press, pp. 218-226,
U.S. Fish and Wildlife Service.
19li3, Fertilization of fish ponds. Fish. Leaf. 12, 7 pp.
38
APPENDIX A
FERTILIZERS REPORTED IN THE LITERATURE
Inorganic
Ammonium phosphate: Smith (19U8a, 19U8b, 1952).
Ammonium sulfate: Juday, et al. (1938), Schaeperclaus (1933)} Smith and Swingle {19hO, 19^1), Swingle and Smith (1939a), Surber (19i47), Wiesner (1937).
Basic slag: Lawson (1937), Smith and Swingle (l9hO,19U3)5 Swingle and Smith (1939b).
Bone meals Davis and Wiebe (1930), Lawson (1937), Schaeperclaus (1933) »
Caustic lime: Hasler and Einsele (19U8), Lawson (1937), Neess (19l;9)^ Schaeperclaus (1933), Wiesner (1937).
Colloidal phosphate: Meehean a nd Marzulli (19ii5) .
Cyanamid, calcium cyanamide: Juday et al. (1938), Schaeperclaus (1933) j Wiesner (1937)
Dicalcium phosphate: Lawson (1937), Schaeperclaus (1933).
Limate: Hasler et al. (1951).
Manganous sulfate: Henderson (19li9) ,
N:P:K: combinations: Ball (I9l9, 1950), Ball and Tanner (195l) , Brown (I95l), Hasler and Einsele (I9I18), Henderson (I9I49), Hogan Cl933,19ii9), King (19^3), Langford (1950), Leach (1936), Meehean (1935), Patriarche and Ball (19ii9), Surber (19U5, 19h7, 19U8) , Swingle and Smith (1939a, I9UI, 1950) .
Noncaustic lime: Hasler and Einsele (I9U8), Hasler et al. (195l), Juday et al. (1938), Lawson (1937), Meehean and Marzulli (1935), Neess (19U9), Schaeperclaus (1933), Smith and Swingle (I9I4I), Surber (I9h8) , Swingle and Smith (1939a, I9II) , Swingle (19U7), Walker (I9I49), Wiesner (1937).
Potash, potassium salts : Hasler and Einsele (I9U8), Juday et al.
(1938), Lawson (1937), Schaeperclaus (1933), Smith (19U8a, 19l48b) ,
Smith and Swingle (19hl) , Surber (19^7), Swingle and Smith (1939a, 1939b, I9I4I), Wiesner (1937).
39
Rhenania phosphate: Neess (19U9) , Schaeperclaus (1933), Wiesner (1937).
Sodiiim nitrate: Hogan (19l;9) , King (19ii3)> Meehean (1939) > Meehean and Marzulli (19U5), Schaeperclaus (1933) > Swingle and Smith (1939a, 19iil, 1950) o
Superphosphate: Brown (195l), Davis and Wiebe (1930), Hasler and Einsele (I9ii8), Hogan (1933), Juday et al. (1938), Lawson (1937), Meehean (1939), Neess (19U9), Schaeperclaus (1933), Smith and Swindle (I9I4O, 19U1, 19U3) , Surber (19hS, 19U7), Swingle (19U7), Swingle and Smith (1939b), Wiebe (1929, 193h) , Wiesner (1937).
Thomas meal: Schaeperclaus (1933), WLesner (1937).
Organic
Aquatic plants; Hasler and Einsele (I9U8), Meehean (1935)., Schaeperclaus (1933), Swingle and Smith (1950) , Vfi.esner (1937) o
Cottonseed meal: Hogan (1933), Leach (1936), Meehean (1933, 1935, 1939), Meehean and Marzulli (19U5), Neess (I9U9), Smith and Swingle (I9I0, 19li3), Surber (19i45, 19^7), Swingle (19^7), Wiebe (193u)
Fish meal: Leim (1931), Sch as^erclaus (1933), Smith (1931, 1933, 193Ub, 193iic, 1936, 1938).
Hays Meehean and Marzulli (19U5) , Surber (19ii5, 19i;7) .
Manure: Davis and Wiebe (1930), Hiyama (1950), Hora (1950), Leach (1936), Meehean (1933, 1939), Nelson (19^1), Schaeperclaus (1933), Shelubsky (1950), Surber (19U5, 19U7) , Swingle (19ii7) , Wiebe (1929), mesner (1937).
Peanut meals Smith and Swingle (19i;3).
Poultry laying mash: Smith and Swingle (I9U0, 19U3) »
Sea Mussels: Smith (1930, 1931).
Shrimp bran: Vftebe (1929),
Soybean meal: Davis and Wiebe (1930), Juday et al. (1938), Leach (1936), Meehean (1933), Neess (19U9) , Smith and Swingle (19^3), Surber (19U5), W^es (I9U6), Wiebe (1929).
Miscellaneous: Embody (1921), Hora (1950), Lawson (1937), Leach (1936), Meehean (1939), Prince and Bear (19ii3), Schaeperclaus (1933), Smith (1933), Swingle (19^7).
I4O
APPENDIX B FISH AND FOOD ORGANISMS REPORTED IN THE LITERATURE
Largemouth bass; Ball (19U9)5 Brown (19^1), Hogan (1933), King (19U3)s
Leach (1936), Meehean (1933, 193l4, 1939), Meehean and Marzulli (19l45) , Nelson (I9I4I) , Patriarche and Ball (19U9) , Smith and Swingle (19i;0, 19ii3), Swingle and Smith (195o) »
Sraallmouth bass: Ball (19^0), Juday at al. (1938), Surber (19^5, 191+7) , Swingle and Smith (1939) »
Bottom faunas Ball (19U9), Ball and Tanner (19^1) , Howell (19U2), Patriarche and Ball (19U9) , Smith (l9U8a), Wales (I9U6) .
Bullhead, catfish: Ball (1950), Brown (195l), Swingle and Smith (1939a, 1950) .
Carp and allied fishes j Hiyaraa (19^0), Hora (19^0) , Lawson (1937), Probst (1950), Rabanal (19^0), Schaeperclaus (1933), Shelubsky (19^0), Snieszko (I9I4I) .
Forage fish (minnows, suckers, etc): Ball (19l;9), Meehean (1939)., Schaeperclaus (1933) •
Panfish (bluegill, crappie, etc): Ball (19U9s 19^0), Ball and Tanner (195l) , Brown (19^1), King (19h3) , Patriarche and Ball (19li9);, Smith and Swingle (I9U0, 19lil, 19U3), Swingle and Smith (1939a, 1939b, 19^0) .
Perch, pikeperch: Ball (19^0), Ball and Tanner (195l), Juday et al„ (1938), Schaeperclaus (1933) -
Plankton: Ball (19^9), Ball and Tanner (1951), Henderson (19i49) Juday et al. (1938), Langford (195o), Leach (1936), Meehean (193U), Smith (1931, 1932a, 1933, 19h8a), Smith and Swingle (I9U0) , Swingle (19U7), Swingle and Smith (1939a, 1939b), Walker (19U5) , Wales (I9I46) , Wiebe (1929, 1930).
Trout: Ball (1950) , Smith (1936, 1938, 19h8b, 1952), Taylor (I9UI4), Wales (I9U6), Wiesner (1937).
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