heat ae & * Vbbataanne a eeles, Spee tehe ts Pek tba ee ela Plehers Soearnet bte-hahethe gents sescemret eels OS heehee ‘WiereesOuba bs). Fidesedl te petertisies ehetentgtiicts} hare pete was vee . tite Bae | sinha, rs) ew tes wg er pieaetss +h tt tee i i : Sie = eeear ur’ sare aaa Bpsthet wueleate : mele tp isy s - Foe. arse : ror it # itt baba he’ ci $3 isitt 2 DEPARTMENT OF COMMERCE AND LABOR ie shes ‘BUREAU OF FISHERIES ° ay ‘GEORGE. Mi. . BOWERS, ‘Comentsxioner if ay ue ie - SURVEY OF OYSTER BOTTOMS 1 IN _ MATAGORDA BAY, TEXAS - oe | Bureau of Fisheries Document No, 610 LUO MASHINGTON hal GOVERNMENT PRINTING OFFICE ’ hy 907. DEPARTMENT OF COMMERCE AND LABOR M BUREAU OF FISHERIES GEORGE M. BOWERS, Commissioner SURVEY OF OYSTER BOTTOMS IN MATAGORDA BAY, TEXAS Bureau of Fisheries Document No. 610 WASHINGTON GOVERNMENT PRINTING OFFICE £907 SURVEY OF OYSTER BOTTOMS IN MATAGORDA BAY, TEXAS By H. F. Moore, Assistant, Bureau of Fisheries. Bureau of Fisheries Document No. 610. PREFACE. On February 13, 1904, Hon. A. S. Burleson, Representative in Congress from Texas, addressed to the Bureau of Fisheries a request that a survey of the oyster regions of that state be made for the pur- pose of determining their extent, condition, and the possibilities of their development and improvement. It being impossible with the Bureau’s limited equipment and personnel to undertake a comprehensive exami- nation of the extensive oyster-producing waters of the entire Texas coast, a work which would require several years, suggestion was made on February 15 that a specific locality be indicated and “that the proper state authorities make a formal request for this survey in order that the Bureau may know officially that the proposed work is agreeable to and desired by the state.” Pursuant to this suggestion Hon. S. W. T. Lanham, governor of Texas, on March 14 made formal application for the survey, and in a letter dated May 14, in reply to a request of the Bureau, submitted correspondence defi- nitely indicating Matagorda Bay as the most desirable region for the investigation. The steamer Yish Hawk was detailed to the work, with the requisite civilian assistants in addition to her naval personnel, and the direction of the survey was assigned to Dr. H. F. Moore, scientific assistant in the Bureau of Fisheries. It was the original intention to dispatch the /ish Hawk in season to take up the work early in September, 1904, but delays incident to the making of neces- sary repairs caused unexpected detention and the vessel did not reach the scene of her labors until December 14. The work continued until May 14, 1905, according to the plans and with the results detailed in the following pages. Grorce M. Bowers, Commissioner. 3 CONTENTS. Spyecth and methods or the Survey". 2222-2. -- «2-5 ose 25 ene oe eee as eoeripnonroie Matavorda Days ose =) Lise See cee eee ne wie eee - Wocationeens sa. soe Area and shore line Attiuents yess ee Menenvang «character or DOtlOM -.e-- 5-5-6 == ae ee a Channels. 22... -2- Mheroyster, beds=--4---- Mensibyrom oyster how thse eer ake: sea ee oe Fes san- a2 -- ses t Types of oyster beds Long reefs - - -- - Shontenecisrandelmmpstesee cc eee Sen eee osteo see ence abs - sec Bila oedsesnGupatGiess aan eee a Ge S SL sans was. alae ees Peseripuontoly fie) Principal DEUS. sace Nec a2 lc =o niso enc ~ see =n asses ees Half Moon Reef Mad Island Reef pale eel MCS een hoe ae reek ee acer aes = Sete a Gees Mem kedeinenyOUlmnNcOteer ie wecaae Maat oc see ae tenets ocee es ss eee Dog Island Reef North end - West side. - Sani nopicnutitveeme ety t= at '0 os ets Jak che Swe se eden ce a Boilers ayOUMCelsMerrme teen. 8k eee ee Oo Peete cre se eet Raymond Landi Kains and Cleve Middle Lump -- Boggy Lump... Grass Lump.-.--.- Idlebach Patches Middle Patches. East Point Bed - Eleven Mile Lumps Creek Patches. - Dressing Point § Live Oak Bay... Beds above Dressing Point Browns Lump Marsh Patch Root Lumps Ranch Patches Off-the-Cut Lumps East Side Lump Shores and bayous LOU SIN OA SNe Mens eet ie se Sm ce ere see Sito Siar | Pewravel) 2F5 te) OVENS 528 a ee ate lls Be et NE cp anor ee htc. cole ae ee ee Go G > OO & Co Sey (SY ISS) 18S) Vf —) oD 09 oo Oo OO IO FP OB ee BB CO tO CO RSFPooocnwuo hw for) CONTENTS. Oyster culture 2c. 2.2. csicch be cet se ce seesceencseb eee Necessity and general considerations. ..........--...----+--.---------- Demand upon the natural beds: --.-- 2.2.2 22-2 3s nee Previous output and possible yield. .....-<-+.\---.n-geese= =e aeeeee The oyster Jaws'and public sentiment....... 5... -.0::-neseeeseee ees eeeen Synopsis’ of existing laws: .. 2... 3.22. -2.< 2.7. Shane oe canteen eee eee ae cole TID Nees cae Jo] sase cee Total jaco-c4 tate saben deduce late enodoee Weicok aed eee Busia -padeeees oxo 445, 900 «Not examined in detail. »’ Partially fished out. ¢ Thoroughly fished out. OYSTER BOTTOMS IN MATAGORDA BAY. Lb TYPES OF OYSTER BEDS. These beds may be divided into three general types—(1) long reefs consisting of extensive long, narrow shell beds surmounted by oysters, running at right angles to the currents and with marked shoaling of the water over their crests; (2) short reefs and lumps consisting of small deep shell beds bearing oysters, with usually no great disparity between their long and short axes, and also marked by abruptly shoaling water; (3) flat beds and patches without ex- tensive deposits of shells, over which the depth varies but slightly from that over the surrounding bottom. LONG REEFS. The long reefs are confined entirely to that portion of the bay lying below the mouth of the Colorado River, and judged by their size and structure they are undoubtedly the beds of greatest age. With the exception of Dog Island Reef, which forms a practically complete bulkhead, they all begin at or near the northwest shore and end in the deeper water toward the middle of the bay. Dog Island Reef probably originated in the same way, and its present condition is but a completed or more matured stage of development. The stiff, waxy, prairie loam which forms the inland shore is better adapted to the support of cultch than is the sand of the gulf side of the bay, which is more or less subject to shifting under the influence of the storms and winds which sweep over the sandy peninsula. Shells or other bodies lodging in the shallow water near the prairie shore are therefore preserved for a longer period in a condition favorable for the attachment of the minute floating fry of the oysters, and once established the infant bed tends to grow by yearly accretions. After the bed has become fairly established and begins to rear its crest above the bottom, the tendency is toward the pre- ponderance of growth at its outer end, where the currents sweep most strongly and more perfectly clean the oysters and shells of all deposits of mud and silt which would operate to stifle the tiny spat. It will be observed from an inspection of the chart that each of these reefs has its long axis at right angles to the set of the currents. Above Palacios Point the currents run generally in the direction of the length of the bay, and Mad Island, Shell Island, and Dog Island reefs therefore lie almost transversely to the parallel shore lines; but at Palacios Point the bay abruptly widens, the currents describe more or less of an arc with the point as the center, and Half Moon reef has grown along that radius to which the flow of greatest velocity is related as a tangent. In other words, the reefs have followed the usual law of development, growing most rapidly toward the strongest current and less rapidly along their sides, where the currents slacken 16354—07 m——2 16 OYSTER BOTTOMS IN MATAGORDA BAY. and eddy and where, therefore, the deposit of mud and silt more speed- ily engulfs the shells and renders them ill adapted to the attachment of spat. In other characters, also, the long reefs present general features of resemblance to one another. Each has a crest or backbone, awash or nearly awash at low water, running from end to end. The margin of the bed facing up the bay is comparatively close to this crest, ab- rupt in its rise from the bottom and continuous in its contour, while the opposite margin is farther removed from the crest, merging more gradually with the adjacent barren bottom and broken up into long projecting ridges or spurs separated by narrow, muddy indentations and sloughs. In all of these reefs, also, the upper side is the only one resorted to by the oystermen, as there only are large oysters of good quality to be found in quantities sufficient to make remunerative tonging. On the lower sides of the reefs not only is the density of all sizes.of oysters less, but among those that are found there is a prepon- derance of small ones, and all are inferior in fatness to those just across the crest. At first thought it might seem that the proportionately large num- ber of small oysters on the lower sides of these reefs was due to a more abundant set of spat, but this assumption is speedily invali- dated by the fact that the total number of oysters there is undoubt- edly less than on the opposite side, notwithstanding that none are removed by the oystermen. The evidence shows, therefore, that the set of spat is actually less than on the upper side, and the prepon- derance of small oysters is due solely to deficiency of growth. From these facts it is apparent that the conditions on the “ up-the-bay ” margins are superior as regards both the set of spat and the supply of food, but the exact nature of the difference is difficult to deter- mine from actual observation. On theoretical grounds, however, it would appear to be dependent upon the set of the currents, for it is a general condition of oyster growth that, other things being equal, the set of spat, the rate of growth, and the production of fat are greatest in those parts of reefs where the water flows with great- est velocity. It can be assumed that in the presence of the great bodies of spawning oysters which these reefs furnish the distribution of swimming fry must be so general as to be practically uniform everywhere in their vicinity; that the food value of the water on the different sides of the reef is essentially uniform was determined by actual observations, as exhibited in the table (p. 73) incorporated in the section of this report treating specifically with that subject. As to the matter of currents, however, what are the actual conditions / In the discussion of the currents of Matagorda Bay subsequently | given in this report will be found the statement that the pre- OYSTER BOTTOMS IN MATAGORDA BAY. 1 ponderating set is toward the mouth of the bay, a condition neces- - sarily imposed by the discharge of fresh water from the several streams. If there were no tributary streams, the currents would be strictly conditioned by the ebb and flow of the tides, and, neglect- ing the small factors of evaporation and seepage, their volumes would be equal in the two directions; but the Colorado and its sister streams drain vast areas of the country, discharging a volume of water which relatively to the cross section of the bay is very con- siderable, and as essentially all of this water finds its way into the gulf through Pass Cavallo, the downward currents must conse- quently be stronger than those flowing toward the head of the bay. This gives the upper margins of the reefs a decided advantage in the matter of conditions favorable to spat fixation and the growing and fattening of the oysters, inasmuch as the cultch is kept cleaner and more food is carried within the reach of the oysters setting on it. It also appears reasonable to invoke the current characteristics as an explanation of some of the physical peculiarities of the long reefs, especially that diversity which occurs between the two sides. The water of the Colorado River, which, especially in times of freshet, is heavily charged with mud, flows into the bay just above Dog Island Reef. As it spreads out after leaving the channel, its velocity is promptly checked and the coarser and heavier particles of sand and mud are deposited to produce a fan-shaped shoal surrounding the mouths of the river and Buffalo Bayou, while the finer particles remain in suspension. At high water, when the crest of the reef is covered, the outward flow of the bottom stratum of this water is largely checked by the barrier of Dog Island Reef and some part of the suspended matter is thrown down on the bottom close to the reef as silt, while over the crest there is flowing a current of sufficient velocity to keep the top of the upstream portion of the reef cleanly scoured and in condition to receive fresh accretions of young oysters. As the crest of the reef is crossed, the velocity is again lessened by reason of the larger cross section of its available channel in deeper water, and there is a deposit of silt upon the downstream side of the bed, rendering it less adapted to a set of spat. When the level of the water is below the crest of the reef, a generally similar result is brought about by somewhat different means. Then the entire dis- charge passes through the several channels by which the reef crest is traversed, especially those at Dog and Tiger islands. There is a current of varying strength running lengthwise of the northeast side of the reef and a swift current through the channels, but as soon as it passes the barrier the silt-laden water spreads out and eddies after leaving the channels, and there is again a tendency to the deposit of mud. 18 OYSTER BOTTOMS IN MATAGORDA BAY. When the tidal currents are reversed and the flow is running up the bay the conditions of silt deposit also are reversed, and were it not for two important factors there would result a general similarity rather than a marked diversity in the aspects of the two sides of the reefs. As has already been stated, the average velocity of the in- flowing current must, from the relative positions of the stream mouths and the mouth of the bay, be less than that of the out- flowing, and it is therefore physically unable to take up and return much of the material carried down and deposited by the latter. In the second place, and entirely independent of the previous considera- tion, the water in the lower bay, coming in large part from the sea, is clearer than that above Dog Island. The streams are the main sources of silt. This is gradually deposited in the course of the water toward the sea, and, once deposited, would require a higher velocity of current to pick it up again than sufficed to carry it originally. In the light of this preliminary understanding of the action of the currents and the local distribution of the silt deposits, let us examine the effect upon that growth of oysters which fixes the final character- istics of the beds. Upon the “ up-the-bay ” side of the reef we find a deposit of silt from the more stagnant bottom strata of water inhib- iting a set of spat at the foot of the barrier while at the same time the flowing surface water is exerting a scouring action on the top of the reef northeast of the crest. The preponderance of oyster growth is therefore at the top of the reef and toward the upper margin of that side, with the result that the margin in question tends to main- tain a uniform outline and an abrupt face. The crest itself hes closer to the northeast margin, because it, too, tends to grow in that direction from the same causes—the superior scouring action and food: - carrying capacity of the currents on that side of the reef. It can never grow to a level much above the low-water plane, because as it rises above that level the oysters are each year killed by exposure to the air for long periods during the low water prevalent in the winter months. On the opposite side of the reef, as we have seen, the condi- tions are essentially different. Immediately upon crossing the crest the outflowing water begins to deposit silt, which falls most abund- antly in the lower levels between the oyster clusters, and the latter soon become, therefore, the only places on that side of the reef pre- senting conditions inviting a new set. Wave action, too, being more energetic near the surface, tends to scour those areas raised somewhat above the bottom, especially those surfaces looking toward the mar- gin of the reef, and silt thus washed away is likewise thrown down in the neighboring pools and crevices. The result is that the original oyster clusters having this advantage gradually grow into clumps, and these, by virtue of the greater cleanliness of their outer ends OYSTER BOTTOMS IN MATAGORDA BAY. 19 more exposed to the waves, eventually develop into tonguelike ridges at right angles to the general trend of the reef, with muddy silted sloughs between them. In the discussion thus far, particular consideration has been given to Dog Island Reef, where the conditions are most marked, but the statements will apply with gradually decreasing force to the reefs below. By virtue of its proximity to Dog Island channel, which acts in relation to it much as the Colorado does to Dog Island Reef, Shell Island Reef presents the same characters, though less marked, the upper margin being abrupt, and the spurs and sloughs on the opposite side of the crest being relatively shorter and less differen- tiated. Mad Island Reef being shorter, there is a wider avenue for the passage of currents around its end. The channel at the inner end of Shell Island is not so large, and therefore discharges less water to impinge on the reef below, and finally the water, by the time it reaches this reef, has had an opportunity to deposit no incon- siderable part of its silt, all of which factors still further reduce the formation of spurs on the lower side of the reef. At Half Moon Reef the lower margin is almost entire, but the conditions are still such, by virtue of the preponderating current velocity from the upper bay, that the crest maintains its proximity to the eastern face, and the oysters are better, larger, and more abundant on that side. From Dog-Island Reef to Half Moon Reef there is therefore a gradual transition in correspondence with the waning influence of the conditions above indicated. SHORT REEFS AND LUMPS. The short reefs, or “ lumps,” as they are usually called, are found principally in the upper part of the bay, though there are a few below Dog Island Reef. They are simply old oyster beds in which the growth is localized, and as a rule they are developed in those places where the currents are less marked than they are below the mouth of the Colorado River. They rise from soft muddy bottoms, which tends to restrict their expansion laterally, and their growth is principally at the top. They often consist of dense bodies of rac- coon oysters. FLAT BEDS AND PATCHES. The patches or flat beds are confined to that part of the bay above the vicinity of Dressing Point. They are relatively young, and in many cases their origin can be -traced to artificial causes, the culling and throwing overboard of shells and young oysters from boats on their way to market. Many of them formerly produced oysters of excellent quality, and under proper density conditions this phase of their history would undoubtedly be repeated. 90) OYSTER BOTTOMS IN MATAGORDA BAY. PRINCIPAL OYSTER BEDS IN MATAGORDA BAY. HALF MOON REEF, : This, the westernmost limit of the survey, is an economically im- portant reef, setting in a generally southwesterly direction from Palacios Point to and beyond Half Moon light. It has a total length of about 5,200 yards and an average width of about 500 yards, em- bracing an area of approximately 494 acres. Between its inner end and Palacios Point there is an area of soft mud, with a width of from 300 to 500 yards and a depth increasing from about 14 feet close to shore to upward of 34 feet at low water on and for a short distance beyond the edge of the oyster bed. This deeper water constitutes Palacios Point channel, much used by boats plying to and fro be- tween the upper bay and the town of Palacios. Stretching prac- tically the entire length of the reef, with here and there an interrup- tion, there is a backbone of shells and oysters lying in a depth of less than 1 foot at the mean low water of winter. Surrounding the light there is a depth of about 4 feet, shoaling rapidly on each side. The shoal crest is nearer the southeast side of the reef, and, as in the other long reefs hereafter described, the slope is relatively sharp in that direction, although, excepting the extreme end, there is not so abrupt a rise at the margin as on Dog Island, Shell Island, and Mad Island reefs. Excepting at the two ends, where the edges of the bed lie in about 34 feet of water, the limit of oyster growth is generally in a depth close to 1 fathom. The reef is growing comparatively rapidly at its outer end, and it now extends from 400 to 500 yards farther toward the southeast than it did when the hydrography of the Coast Survey was executed. That it is a very old reef is shown by the depth from which it rises and by the results of probings through an almost impenetrable mass of shells and compacted fragments at least 8 or 4 feet in thickness. As in the cases of the other beds of the region, it began by the fixation of a few oysters to some firm for- eign body lying in mud of a consistency similar to that now sur- rounding it, and upon the shells so grown successive generations set until the whole area became covered and the level was gradually raised higher and higher above the normal bottom. It is still build- ing up, and, as stated, comparison with the previous survey shows that its horizontal dimensions, and particularly its length, are increasing with comparative rapidity. According to local witnesses its productiveness ha _ iuctuated greatly, more or less long periods of barrenness having been succeeded by periods of rejuvenescence and fecundity. Local authorities state that there were no oysters on it in 1895 and for several years thereaf- ter, but about 1900 there was a heavy set of spat which grew to market- PLATE Il. 1. OYSTERS FROM HALF MOON REEF, SHOWING “RED GRASS" (EGG-CASES OF PURPURA). Reduced i 2. OYSTERS FROM HALF MOON REEF, SHOWING PITS AND CHAMBERS OF BORING CLAM (MARTESIA). Reduced §. OYSTER BOTTOMS IN MATAGORDA BAY. 21 able size about 1902, since which year it has been fished each season. During at least a part of the season of 1904-5 it was the most ex- tensively tonged bed in Matagorda Bay, about 50 boats being con- stantly at work on it during November and December. Apparently there has been no heavy set of spat in recent years, and the area which has been most extensively worked during the past two or three seasons is showing distinct indications of such exhaustion that unless soon replenished with a young growth it will speedily again become barren. At the inner end, in the area shown on the chart as a very scattering growth, a number of boats operated early in the season, but when this portion was examined in the latter part of April there was practically no young growth and an average of but one adult oyster per square yard. This part of the bed covers about 56 acres and was estimated to contain but approximately 1,000 barrels of oysters, about 18 barrels per acre. Between 300 and 800 yards shoreward of the light the same conditions obtain, there being an average of but two adults per square yard. The oysters in both of these localities are almost without exception large, single, and of good shape. Beyond the light the growth is sparse, and no fishing is done there. Of the very scattering oysters on the outer third of the reef it is estimated that there are about 4,400 barrels, covering an area of 176 acres. The densest area at the time the reef was examined lay on the southeast side of the crest between 800 and 3,500 yards from shore, on which there were per square yard 35 oysters over and 11 under 3 inches in length. On this section there were estimated to be in April, 1905, about 30,000 barrels of adult oysters, covering an area of 87 acres. This area had been rather thoroughly fished during the season, and in places had been almost “ cleaned up,” leaving but a scattered growth. The oysters are good in size, shape, and quality. Many of them, especially in areas which have been tonged, are single, shapely individuals, but in the parts less extensively worked they are large, clustered, and more elongate. They are best near the margin of the reef. The part of the reef lying northwest of the crest was not examined in detail, but general observation showed it to possess the same rel- ative characters as the corresponding portions of the other long reefs hereinafter described. There is a scattering growth of poor, small oysters, covering an area of about 175 acres. The shells of oysters from Half Moon Reef are characterized by abundant pits and chambers excavated by the boring clam, a more detailed account of which will be found in the section of this report dealing with oyster enemies. The yellow boring sponge, which honey- combs the shells with its galleries, is also abundant; there is a sparse growth of mussels, and in April, 1905, many of the shells bore clusters 29 OYSTER BOTTOMS IN MATAGORDA BAY. of the red egg cases of the so-called borer, Purpura. These cases are often referred to by the oystermen as “red grass.” The drumfish is said to be destructive at times. One of the chief characteristics of the oyster growth is the scarcity of young oysters. This is a serious matter, and indicates an ap- proaching period of unproductiveness unless there is a speedy change for the better. MAD ISLAND REEF. This is the smallest of the Matagorda Bay “long reefs.” It stretches in a generally southeasterly direction for a distance of about 2,000 yards from the north shore at Mad Island West signal, with an average width of about 300 yards and an area of about 93 acres exclusive of the exposed crest, which extends for practically its entire length. Apparently this reef has not grown at its offshore end as have Half Moon and Shell Island reefs, a fact that may be explicable on the assumption, based on local reports, of its periodical destruction. It is known that on at least one occasion, about 1896 or 1897, it was almost if not entirely destroyed by fresh water, grass, sand, and debris carried upon it by a freshet in the drainage basin of Mad Island Lake, and it is stated that similar disasters had before visited it. After an interval of several years it became reseeded by a heavy set of spat, and during the season of 1904-5 the oysters became marketable and were in considerable demand at Matagorda. The reef lies on a deep, dense bed of shells, compacted with fragments and sand, lying on a foot or two of soft mud, which in turn is underlaid by hard mud. The margin of the bed les in a depth of about 14 feet of water at the shore, with gradually increasing depth to 5 feet offshore. The crest, which is close to the eastern margin, is more or less covered with a growth of raccoon oysters, and at its inner end has an elevation of 6 or 8 inches above the low-water plane adopted in this report. The eastern margin is well defined and continuous, and it is near this limit only, over an area of about 23 acres, that mar- ketable oysters are found. There was in April, 1905, on the reef east of the crest, an average per square yard of about 42 adult oysters and 28 small ones, and from these data it is estimated that there were at that time approximately 9,000 barrels of marketable oysters. Both young and adults had well-shaped, clean, thin shells and the market- able stock was of good size and flavor, with a considerable proportion of single oysters and few clusters of more than 3 or 4 individuals. The preponderance of single oysters and small clusters is directly attributable to tonging, a number of boats having operated on this part of the reef during the season preceding. On that part of the reef lying west of the crest the conditions are quite different. The area is much larger, about 70 acres, and the reef slopes gradually away from the crest to a more or less indented PLATE III. ced 2. 3 13) o jag 1p) jag uJ io ep) = Oo i uw ua} jag Zz e) {e) = re = ss. cone tees 72 February 1-14, inclusive ................ £0204) April 16-80) inclusive. .:-5.. 2 --.ssseeeee 73.4 February 15-28, inclusive ..............- Piso||, May l= ANCMUIBLYG: 3225225 2cn- cee eee fr 4 March 1-15) inclusive... 4-2 2.24 ss. aoe 60.3 Number of days on which temperature was between— | Days Month | — observed. 30-40. | 40-50. | 50-60. | 60-70. | 70-80. | 1905 | JANUSTY Ss ono acc cine oc conte een aseeceepcaee wate | 1 10 7 ere ee. | el Rebruany)-- (8-2) 0c ae ee er eee 3 22 3 eae We eceee | 28 Marchiss ch eceacec cose eee seer pace teinn aan ae oe a Nes Sites 10 17 | rd Bae | 31 A prilissoanjae stb : Agee re ee eee heck ee USE See oe eee 5 25 | 30 May dalik.. Soc ste. cscces see score teens Ree eweie ee ee 11 | 11 The temperature observations at large in the bay, owing to the ex- igencies of the work and weather, were not made with sufficient reg- ularity and system to be readily digested, their main purpose being the correction of the densities shown on the chart. A comparison with the corresponding day’s observations on the Fish Hawk shows a general agreement within one or two degrees, excepting, as might be expected, that the shoal water warmed more rapidly with the ad- vance of spring. During the winter, which was an unusually severe one, the temperature dropped on several days below the freezing point, but on the whole the operations of oystering were not nearly so much interfered with as they are every year on the oyster beds of Chesapeake Bay and northward. In this respect the oyster fields of Texas and other localities on the gulf coast have a distinct advantage over those of the Atlantic coast. The prime importance of the temperature of the water lies in its relation to spawning and the spawning season. The oyster, as is shown by the writer’s observations on various parts of the gulf and Atlantic coasts, does not begin to spawn until the temperature of the surrounding water reaches about 70° F. An inspection of the table will show that this average temperature was not reached until April, and it was past the middle of that month when it rose permanently above 70°; before then there were occasional periods when it fell for a day or two below that point. During the winter particularly the changes of temperature, even at a depth of 8 feet, were sudden. From 8 a. m. February 12 to 8 a. m. February 14 the temperature fell from 48° F. to 32° F.. a decrease of 16° in forty-eight hours, and from 8 a.m January 12 to 8 a. m. January 15 it fell 18°, from 59° to OYSTER BOTTOMS IN MATAGORDA BAY. Dit 41°. After March 1 the changes were more equable, a factor favor- able to the young oyster fry, which appear to be peculiarly susceptible to the influences of sudden transitions. There are no records avail- able which show what the late spring and summer temperatures may be, but it can be assumed that after the middle of April the tempera- tures everywhere in the bay are above the minimum required for spawning, and that there are few, if any, sudden changes such as kill large numbers of the oyster fry and interfere with spawning on some of the beds of the North Atlantic coast. DENSITIES OF WATER. By the density of the water is meant its specific gravity or the weight of a given quantity, as compared with the weight of the same quantity of pure fresh water. If the weight of the latter be con- sidered as 1.000, that of salt water from the open sea will be about 1.0260, and the water on the oyster beds will be somewhere between these two, as oysters live only in brackish waters and eventually die if placed in water either too salt or too fresh. Aside from the ques- tion of the very existence of the oyster the matter of density or salinity influences the flavor, stock taken from the fresher waters being insipid or even repugnant to many palates, while very salt water produces a briny flavor equally objectionable. Two series of density observations were made during the survey, one on the /ish Hawk in connection with the temperature observations from January 1 to May 7, inclusive, and the other by the field party as the work progressed from the head of the bay downward. The latter, which, like the other series, have been corrected for tempera- ture, are shown in red figures in their appropriate positions on the chart, together with the date upon which the observation was made. As was to be expected, the water in the upper parts of the bay has a very low density. The Colorado River, Caney Creek, and several smaller streams flow into this part of the bay and at times discharge large volumes of fresh water, and there is a considerable influx at all times. This fresh water has no means of egress from the bay excepting at Pass Cavallo, about 30 miles below Matagorda, and, moreover, its escape 1s very materially retarded by Dog Island Reef, which with the exception of several small channels forms a complete barrier across the bay, with its crest awash at low water, just below the mouth of the Colorado. Formerly, as already stated, a channel, Mitchells Cut, afforded a connection of fluctuating breadth and depth between the extreme upper part of the bay and the gulf, but in the summer of 1904, after many oscillations dating from the time of its formation about 1875, this cut finally closed. It is apparent that during the existence of the opening the density conditions in the upper bay must have been quite different from those obtaining during the survey. It 5S OYSTER BOTTOMS IN MATAGORDA BAY. furnished an avenue.of escape for the fresh water discharged by the streams and a means of ingress for salt water from the gulf, and the two agencies operating toward the same end must inevitably have produced a salinity considerably higher than that found by the survey. That this is true is indicated by the former presence of good oysters above Dressing Point, where they could not be produced under the conditions existing during the winter of 1904-5. During March and until April 12 the highest density observed above Dog Island Reef was 1.0061 on March 22, and most of the readings were below 1.0030. This was during a time when the observations made below Dog Island Reef on the Wish Hawk av- eraged about 1.0140. Above Dressing Point on several occasions the water was perfectly fresh and at no time between March 1 and March 21 did it rise above 1.0056 and the average was but 1.0020. This part of the bay is of course especially affected by the closure of Mitchells Cut. The observed density is entirely too low for the production of good oysters, and as during times of heavy rainfall in the drainage basin of the Colorado it undoubtedly falls for con- siderable periods below the average density of March there is no doubt that many of the beds will eventually be decimated or utterly destroyed unless from either natural or artificial agencies there occurs some change in the topography which will reestablish con- nection with the gulf. During the spring of 1905 this condition was made manifest to those interested in the oyster industry at Matagorda, and a private subscription was made to defray the expenses of opening a new cut. Considerable work was done in deepening Browns Bayou (just be- low Brown signal) and this channel was extended artificially almost to the gulf shore. The position of this canal is shown on the chart. It was planned to make the final opening into the Gulf at a time of very high tide in the bay, so as to take advantage of the scouring action of a strong outward flow to carry the excavated sand away from the bay, but at the time the survey party left (May 12) no such opportunity had occurred. Undoubtedly this cut if completed and maintained will have a beneficial effect, and should considerably increase the density of the water in the upper part of the bay and reestablish the oyster beds of the region upon their former productive basis. It is doubtful, however, owing to the shifting sands of the gulf littoral, whether the cut can be maintained in effective cross section without more or less frequent excavation. A jetty or revetment extending to moderately deep water in the gulf would doubtless be most banefsials but such work is expensive and it is uncertain whether it would Be warranted by the results. At all events, however, the establishment of oyster culture and the existence of productive natural beds in the upper waters of Mata- ; OYSTER BOTTOMS IN MATAGORDA BAY. 59 gorda Bay depend upon the maintenance of some considerable con- nection between the gulf and the bay in that region. The present low salinity is absolutely prohibitive of the production of market- able oysters. Between Dressing Point and Raymond Landing Shoals the bay, from the standpoint of density, may be divided into two portions by a line running through the middle. Northwest of this line the average density between March 20 and April 6 was 1.0030 and south- east of the line during the same period the average was 1.0048, over 50 per cent higher. As this was at a time when the standard obser- rations on the F%sh Hawk showed a marked decline of 50 or 60 degrees, it is not improbable, though by no means certain, that earlier in the season, during January, February, and the first half of March, the water on the southeast side of the bay had a density of at least about 1.0060 or 1.0070, quite sufficient for the production of market- able oysters, though not oysters of the best quality as regards flavor. Between the uppermost of the Raymond Landing Shoals and Dog Island Reef there was the same difference between the two sides of the bay from April 7 to April 12, when the local observations were made, the average density of the northwest half of the bay being 1.0012 and that along the southeast shore 1.0038. These observations were made at a time when the general salinity of the bay was low, as is shown by the Fish Hawk observations, and what has been said in regard to probable higher salinity earler in the season above Ray- mond Landing Shoals is equally applicable here. Proximity to the discharge from the Colorado River, however, must always keep the density unsuitably low on the northwest shore. There never have been any oysters there and there never will be so long as the mouth of the river maintains its present position. Below Dog Island it is convenient for the purposes of consideration of the densities to divide the bay into three longitudinal zones, one near each shore and the other in the middle. When the depth exceeds 5 or 6 feet there is almost invariably a difference in density between the bottom and surface strata, the fresher water from streams and ‘ainfall tending to float above the more saline water coming in from: the sea. As the survey’s observations were all made at a fixed dis- tance of about 14 inches above the bottom, it follows that the water specimens trom the shallow water alongshore were taken at a point much nearer the surface than those made in the middle of the bay. Tn the region between Dog Island and Mad Island reefs the aver- age densities for the northwest shore, middle, and southeast shore were 1.0024, 1.0078, and 1.0094, respectively. These readings show the influence of the discharge from the Colorado, which, passing mainly through Dog Island channel, near the northern end of the reef, tends to lower the densities in the northwest and middle zones, 60 OYSTER BOTTOMS IN MATAGORDA BAY. The tendency of the strongest upward currents carrying the water from the gulf to hug the peninsula shore also operates to produce : higher density in that part of the bay. As the densities taken by the Fish Hawk at this time were about 50° below the normal estab- lished by the series, it is probable that the averages for the months of January, February, March, and April in this region were from 30° to 40° higher than above indicated. Below Mad Island Reef the fresh water discharged through Dog Island channel having been de- flected southward by two long projecting barriers of oysters extend- ing from the northwest and commingled by currents and wave action with the denser waters from the lower part of the bay, the disparity in density between the two shores is much less marked, the respective averages of the three zones, beginning at the northwest shore, being 1.0140, 1.0168, and 1.0163. These readings were obtained between April 22 and 28, and as the “ish awh: observations were then about 10° above the established normal, the local readings should be re- duced by that amount in order to obtain the probable average between January 1 and May 1, 1905. The * normal ” referred to in several places above is the average of 381 density observations made at the Fish Hawk anchorages from January 1, 1905, to May 7, 1905, inclusive. The monthly averages are as follows: January, 1.0124; February, 1.0154; March, 1.0134; April, 1.0092, and May, 1.0100. The average daily observations are shown graphically in the upper curve on plate x, an imspection of which will show that the densities were sometimes fairly uniform for several days in succession, but frequently exhibited sudden and violent fluctuations. A study of these fluctuations shows that they are in large measure conditioned by the tides, and the latter are in turn, as has been previously stated, mainly influenced by the winds. A northeast wind, therefore, lowers the tide and decreases the density, while a southwest wind has the opposite influence. To illustrate this influence of the tides upon the density a tidal curve has been prepared showing the mean daily height of water at Matagorda above or below the plane of reference. It will be seen at once that there is a general coincidence of the two curves; whenever the tidal curve rises or falls abruptly there is a more or less synchronous rise or fall in the densi- ties. The explanation is that whenever there is a low tide after a period of tidal elevation the current sets down the bay, carrying the fresh water discharged by the streams into the region below Dog Island Reef, whereas a high tide after a period of tidal depression backs the salt water from the gulf toward the head of the bay. Of course, these phenomena are related solely to what has taken place immediately prior to the time of observation and have no bearing upon more remote facts. For instance, the tides of the middle of April were higher than any of those of January and February, yet PLATE X. JANUARY FEBRUARY MARCH APRIL DAILY DENSITY AND TIDE OBSERVATIONS IN MATAGORDA BAY BETWEEN JANUARY 1 AND MAY 1905. OYSTER BOTTOMS IN MATAGORDA BAY. 61 they were accompanied by much lower densities. It will be ob- served, however, that the tides, though higher than they were in February, were much lower than they were at the beginning of April, and that: consequently the upper part of the bay was discharg- ing the water which it held at the beginning of the month; in other words, the currents were setting from the fresher parts of the bay. Of course, in the long run the density is dependent upon the pre- cipitation and drainage, and in April the streams were discharging into the bay a vastly greater volume of water than they carried in February. The greater the discharge of fresh water into the upper bay the lower will be the average density of the water during that time and for a longer or shorter period succeeding. As a density of at least 1.0100 is generally regarded as essential to the production of oysters of good flavor it will be seen that, other things being equal, the region below Dog Island Reef has in respect to salinity an advantage over localities above the reef, and that be- tween Dog Island and Mad Island reefs the southeast side of the bay is distinctly superior to the opposite shore and the middle. These facts are significant to the prospective oyster growers desirous of producing the best stock. The saltness of the oysters is less im- portant to the shipper of shucked oysters than to the dealer in shell stock, as washing and icing, to which the former are subjected, tend in any case to deprive them of much of the original flavor. With the growth of the country in population and wealth, however, the shell trade invariably increases, a condition eventually to be expected on the Texas coast. STGRMS, FRESHETS, AND SILTING. These factors are all concerned mainly with destructive action on the beds through the deposit of materials which stifle the oysters already existing and so cover the shells as to unfit them, for longer or shorter periods, for cultch. The gulf is subject to the visitation of storms of great violence and destructiveness, which not only wreak great damage to the frailer works of man, but also cause marked changes in the topography and hydrography of the coast. Within the past thirty years two such gales, accompanied by extraordinarily high seas and tides, have been experienced in Matagorda Bay. During the great gale of 1875 the sea swept over the peninsula in many places, greatly changing the topography of that sandy strip of land and carrying large quantities of shore material into the neighboring portion of the bay. As has been before mentioned, Forked Bayou Reef was partially over- whelmed with sand at that time and nearly destroyed as a productive bed, and there is reason to believe that some of the other minor beds 62 OYSTER BOTTOMS IN MATAGORDA BAY. have, either at this or some other not remote period, undergone similar experiences. Ifa bed raised high above the bottom, as is Forked Bayou Reef, can be thus threatened with extermination, planted beds, which will never be permitted to accumulate to any considerable depth, would be subjected to still greater danger. Fortunately, however, storms of such violence are uncommon, and an average period of con- siderable length is to be expected between successive occurrences. The chief danger to oyster beds lies in that part of the bay closest to the peninsula; the prairie shore and the middle of the bay are com- paratively little affected. With this matter the sole consideration. the prospective oyster culturist should avoid a location in an exposed situation too close to the peninsula and especially the vicinity of very shifting sands either along shore or on the adjacent bottom. There is another possibility of storm action, however, which may have a favorable aspect for the oyster industry. The same gale which practically covered Forked Bayou Reef. cut a semipermanent com- munication between the gulf and upper bay, with the result, as has been before stated, of making favorable to oyster growth a great area of the bottom on which it had previously been inhibited by the fresh- ness of the overlying water. The same thing is liable to happen again under similar conditions, but of course it can not be anticipated or taken into consideration in the location of oyster claims; and more- over, while benefiting the upper bay in general, the local conditions in the immediate vicinity of the cut, through scouring and erosion in one place and silting in another, would undoubtedly be more or less destructive. So far as freshets are concerned, the peninsula shore, especially below Tiger Island, is practically immune. The drainage into that side of the bay is local and circumscribed and can never be consid- erable in amount. On the other hand, the streams discharging on the prairie shore drain thousands of square miles of land, over which at times there may be enormous precipitation. Freshets act de- structively in two ways—by reducing, for considerable periods, the density of the water to a degree which the oysters are unable to tolerate, and by carrying upon the beds sand, mud, and débris, which bury the oysters, killing them and rendering their shells inaccessible to a new set. The first disaster is more liable to occur in that part of the bay above Dog Island Reef where the fresh water tends to become impounded or dammed back and where its effects extend more or less completely from shore to shore. The burial of beds under the deposits of detritus carried down by floods is, on the other hand, more likely to occur closer to the mouths of the streams, and the damage may be done in a comparatively short time. This agency of destruction is therefore more imminent close to the prairie shore, either above or below Dog Island, and we have a case in point, OYSTER BOTTOMS IN MATAGORDA BAY. 63 already noted, in the destruction of Mad Island Reef by the débris carried upon it by the floods in the drainage basin of Mad Island Lake, which discharged close to the shoreward end of the reef. Localities such as this, therefore, are to be avoided for oyster culture. The term “ silting,” though in general meaning the deposit of any materials, either coarse or fine, from turbid water, is in this special connection restricted to the more or less constant dribbling of fine material upon the bottom. It has but little effect upon adult oys- ters, operating mainly to cover the cultch, either natural or planted, with a deposit, very thin perhaps, yet sufficient to stifle the small fry at the time when it is settling to fix and become spat. This fine sediment is thrown down in general where the currents are slack, and will therefore, under present conditions, be greatest above Dog Island Reef and in the wake of the larger reefs in the lower bay— that is, on the prairie shore. In other words, the peninsula side of the bay below Tiger Island is liable to be more free from silt de- posits, a fact of considerable importance to oyster growers in search of a location. ENEMIES OF THE OYSTER. The information gathered concerning the enemies of the oyster in Matagorda Bay is neither as definite nor as copious as it is to be desired. As the investigation was made entirely during the months of*winter and early spring, direct observations upon this phase of the subject were comparatively few, excepting in the cases of mus- sels, boring clams, and similar organisms having no particular sea- sons of operation or presence. It is evident, however, that in com- mon with other localities on the gulf coast Matagorda Bay is free, or practically free, from two of the most dangerous and _ trouble- some enemies of the north Atlantic oyster beds—the starfish, which is the dread of the Long Island Sound oyster planter, and the drill, which annually causes great destruction on the Chesapeake. Besides the enemies enumerated below, it is probable that the large ray, known on the Louisiana coast as the “stone-cracker,” may cause oceasional damage, and there is also probable the occurrence of an obscure parasitic worm (Bucephalus haimeanus), which has been found in Louisiana. Drumfish—Of the aggressive enemies of the oyster this is appar- ently the most destructive found in the waters of Matagorda Bay. The species generally known as the “ black drum” (Pogonias cro- mis) is found on the oyster beds more or less along the entire coast from New Jersey to the Rio Grande, but it varies much in destruc- tiveness from year to year and with the locality. A low density of water tends to exclude some oyster enemies, such as the starfish, and a high density others, such as the drill (Uvosalpinx), but the drum- 16354—07 Mu 5 64 OYSTER BOTTOMS IN MATAGORDA BAY. fish is found in water of almost any density, and no locality acces- sible from the sea may be expected to be free from it. Often within a single night, for this destroyer works chiefly in the dark, hundreds of bushels of stock are ground to fragments. The fish frequently congregate in considerable schools, and from 100 to 200 are known to have been killed by the simultaneous explosion of two charges of dynamite 50 feet apart. As the fish are large and powerful the damage wrought by a school so numerous as this would indicate ‘an be readily appreciated. In the case of one grower near Tuck- erton, N. J., about 80 per cent of a total planting of 15,000 to 20,000 bushels is estimated to have been destroyed in a few weeks, and such is the concealment which the nocturnal feeding habits of the fish afford that the damage was almost completed before the owner was thoroughly aware of what was occurring. The drum was, more- over, a comparatively new enemy in the vicinity, and even after the loss was noticed it was for some time attributed to theft. This fish differs from most other animals preying upon the oyster in the fact that it is in general more destructive upon the planted than upon the natural beds, and the better the shape of the oyster the more lable it is to attack. The drum feeds upon its prey by grinding it up, shell and flesh, by means of the great molar teeth which floor and roof its mouth. The ill-shaped, densely clustered, sharp-edged raccoon oysters, the extreme of their type, are usually in such large clusters and present so many knife-like points and edges that it is difficult for the drum to crush them without itself suffering serious injury, and it is no uncommon thing to find the fish in the vicinity of raccoon oyster beds with badly lacerated lips and mouth. The planted oysters, however, especially those of the better grade, are in smaller clusters, and their rounded shells can be seized by the fish with much greater impunity. On the Louisiana coast, and presuma- bly in Texas, unculled oysters can be bedded with comparative safety, but when the clusters are broken up in order to permit the liberated individuals to grow and improve untrammeled by their fellows it is necessary to surround them with stockades or netting to prevent their complete destruction by the drums. As might be supposed also the younger and thinner-shelled oysters are more likely to be damaged than large heavy-shelled ones, and it is generally observed that the period of a few weeks following planting is that of greatest danger. Whether the oysters in time become more or less concealed and incon- spicuous through the deposit of silt, or from some other reason, it is generally observed that the old bedded stock is liable to escape while adjacent recently bedded oysters are destroyed. In the winter the drumfish is less active and less abundant in shoal water, and for this reason the survey party had little oppor- tunity to study it in Matagorda Bay. During some of the extreme OYSTER BOTTOMS IN MATAGORDA BAY. 65 cold weather a number of dead drums were observed near Mad Island and at other places. The oystermen state that at times con- siderable damage is done at Half Moon Reef and on other beds in the lower part of the bay, but apparently there is less danger to appre- hend above Dog Island Reef, though there is no reason why the fish should not be found there at times. Mussels.—The mussel may be regarded as one of the passive ene- mies of the oyster—that is, an organism which injures it not by direct attack, but by appropriating to itself certain things which the oyster requires, in this case food and space in which to grow. As will be shown in a following section of this report, the oyster feeds mainly upon microscopic plants called diatoms, of which there is a more or less limited supply in any given body of water. Investi- gation has shown that the food of the mussel consists of these same organisms, and its consumption of food consequently lessens by so much the supply available for the oyster. An abundant growth of mussels therefore may render inadequate for the oyster a natural fertility of the water otherwise quite sufficient, and beds which if clear of mussels would produce oysters of good quality are thereby rendered of but little economic value. Moreover, if crowded by its fellows or by foreign growths, the oyster assumes elongated or irregu- lar shapes, the shells are shallow, and the meat is generally inferior ; in other words, it tends toward the raccoon type. The young mus- sels under favorable conditions attach in large numbers to the oysters, and as they grow with great rapidity they soon form dense masses, which fill all available space in the clusters and crowd the oysters to the point of starvation and suffocation. In a number of places in Matagorda Bay numerous instances were noted in which the mussels had grown in great masses over the lips of large oysters and had actually killed them. In addition to the damage wrought thus, the mussels operate in other ways to injure the beds. By presenting entanglements they tend to collect seaweeds and other débris, which serve to stifle the oysters; and they very much interfere with culling, because, unlike oysters, they can not be knocked from the clusters, but, owing to their tough attachments, must be laboriously pulled off, leaving rough, unclean- looking débris behind. In Matagorda Bay mussels are found in varying numbers on prac- tically all of the oyster beds, but below Dog Island do not constitute a markedly objectionable feature. They thrive best in water of low salinity, and in the extreme upper part of the bay they constitute a serious menace to many of the beds. It was stated by persons fa- miliar with the region that they have developed to this extent only within a comparatively recent period, mostly since the permancnt 66 OYSTER BOTTOMS IN MATAGORDA BAY, closure of Mitchells Cut. The oyster grower must take this fact into consideration, for beds overrun with mussels are not only less productive, but the stock is lable to be inferior in condition and external appearance and more labor is required to cull it. Borer, boring clam (Martesia cuneiformis).—During the survey frequent reference was heard to the presence of borers upon certain of the beds, but investigation developed that it was neither the drill (Urosalpinx) of the Chesapeake nor the lke-named snail (Purpura) of the gulf coast which was so designated, but a comparatively harm- less little clam. Neither upon the reefs nor among the specimens exhibited by the oystermen was there found a single shell exhibiting the work of a predatory snail. A few live specimens of U’rosalpina were found, and on Half Moon Reef there were many egg cases of Purpura, but it is evident that these organisms are not destructive in these waters. The boring clam appears to be confined almost exclusively to Half Moon and Mad Island reefs, being most #bundant on the former, where a large proportion of the shells are occupied by it. It in no way preys upon the oyster, but merely utilizes the shell as a place of abode and does but comparatively little harm. If either living or dead oyster shells from Half Moon Reef are carefully examined, a very large proportion of them will be found to exhibit numerous small round holes, each fringed with a very short parchmentlike tube. If the shell be carefully broken, each of these orifices will be found to communicate with an egg-shaped cavity, narrow toward the opening and broader toward the inner face of the shell, in which is snugly lodged a little clam of corresponding shape. Often the chambers are so numerous as to be almost in contact and the shell is reduced to the strueture of a honeycomb. In such cases it becomes much weakened, the outer layer scales off, the clam drops out, and the new surface exposed presents the bottoms of the chambers as a mosaic of smooth hemispherical pits having the appearance of drilled cavities almost penetrating to the inner face. It is this appearance that generally attracts the attention of the oystermen, who apparently do not connect it with the small inconspicuous ori- fices primarily existing. The boring clam first enters the shell when quite small and in- creases the dimensions of its chamber as it grows, eventually attain- ing a length of three-eighths of an inch. The boring of the chamber sometimes perforates the shell, in which case the oyster throws down new deposits of shelly matter to close the opening and produces either a general thickening when the perforations are numerous and close together or a series of slightly elevated lumps when they are more isolated. The clam never attacks the oyster, but gets its food OYSTER BOTTOMS IN MATAGORDA BAY. 67 through the external pores. Although so far as the writer is aware no investigations have been made, it undoubtedly feeds upon many of the same organisms that constitute the oyster’s food, but so small must be the quantity required that it can not have much effect in de- priving the oyster. The only real damage done by this organism is the gradual disintegration of the old shells to the lessening of their value as cultch and the occasional weakening of the shells of living oysters so that they break in culling. Boring sponge (Cliona sulphurea).—This animal, like the preced- ing, attacks the shell rather than the oyster itself. It apparently is not so troublesome in Matagorda Bay as on some other portions of the coast, but evidence of its work was found on certain of the reefs below Dog Island; above that place the water is generally too fresh for it to grow in profusion. It produces what are generally known to the oystermen as “ worm-eaten ” shells, a condition characterized by a network of small irregular burrows which often so completely fill the shell and leave so little solid material that it can be crumbled in the fingers. In its young stage the sponge fills these galleries with a yellow pulpy mass and projects from the external orifices in little mushroom-shaped papilli or pimples. In its older stage it. forms a large sulphur yellow or pale orange mass which may completely embrace the shell in which it originally grew. The means by which it burrows has not been definitely determined, but it probably exudes a fluid having a solvent action on the limy material of the shell. The boring sponge damages the reefs in several ways. It breaks up the shells and covers them with a shmy deposit, both of which processes tend to unfit them for the attachment of future growths of oysters. It renders the shells fragile and difficult to cull, besides making the oysters unattractive as shell stock, both on account of their exterior appearance and the mottled and discolored aspect of their interior. It serves to encourage the accumulation of other débris on the beds. And, finally, as the galleries frequently pene- trate the inner face of the shell, the oyster to stop the gaps is forced to lay down successive deposits of shell and apparently suffers more or less damage, for almost invariably badly infested individuals are poor in quality. Barnacles (Balanus).—Barnacles are generally a minor or insig- nificant enemy to the oyster. Their effect is very much the same as that produced by the mussel, their rapid growth tending to produce crowding in the oyster clusters, besides making the shells unattract- ive and uncomfortable to handle. In Matagorda Bay they are not especially troublesome, though found in small numbers on a consid- erable number of the beds. “Red grass.”"—The growth locally known by this name is not a 68 OYSTER BOTTOMS IN MATAGORDA BAY. vegetable substance at all, but consists of the closely aggregated egg cases of a snail-like mollusk, Purpura. It is found in dense masses upon the oysters and shells of Half Moon Reef, the growth being about one-half inch long, extremely tough and leathery, and of a rich crimson color. It is objectionable in itself as interfering with culling, and the mollusk to which the eggs give rise is reputed to drill the oysters, although the author has never been able to satisfy him- self absolutely of the truth of this assertion. FOOD OF THE OYSTER. CHARACTER OF FOOD AND MANNER OF FEEDING. The food of the oyster consists mainly of microscopic plants, prin- cipally of the kind known as diatoms, together with a small number of microscopic animal organisms, Infusoria, some of which so closely re- semble piants that their exact status is still a matter of dispute among naturalists. Diatoms, a number of species of which are illustrated (pls. x1, x11, and x11), vary greatly in shape and size, but all resemble one another in the interesting character of encasement in a siliceous or glassy shell, usually beautifully sculptured, and nearly all of them have the power of independent movement. Most of them exhibit a golden brown coloration, unequally distributed, but there are a few blue-green species. Prorocentrum, one of the so-called animal or- ganisms referred to above, is an equally minute green body, propelling itself by means of a taillike lash, and it, too, is sometimes inclosed in a capsule, which, however, is not siliceous in structure. Though both diatoms and Infusoria are capable of motion by their own powers, their movements are too feeble to transport them any con- siderable distance and are only sufficient to raise them above the bot- tom, where, however, the organisms are brought within the action of tidal currents, which become the chief agency of transportation and bring about their general distribution. The oyster feeds upon these minute bodies by straining them through its sievelike gills from the same water which it utilizes in respiration, and it passes them on to the mouth through feeble cur- rents set up by the lashing of innumerable microscopic bristles which clothe the gills and the neighboring organs. These currents are the only means by which the oyster can reach out into the water sur- rounding it and bring to itself the food there supplied, and so weak are they and so limited in their radius of action that the supply avail- able to each individual oyster would be soon exhausted were it not constantly replenished by tidal currents bringing new bodies of food- laden water within reach. In still water, therefore, the oyster is able to obtain less food than in flowing water of the same fertility. OYSTER BOTTOMS IN MATAGORDA BAY. 69 DISTRIBUTION AND AVAILABILITY OF FOOD. In any given body of water in which the physical conditions of precipitation, density, temperature, etc., are fairly constant there is a more or less fixed limit to the amount of oyster food produced, very much as there is limitation to the size of the crop that can under simi- larly fixed conditions be grown on a given area of land. As, how- ever, the diatoms and other organisms upon which the oyster feeds are not permanently fixed to the bottom but suspended in the water, it follows that their abundance fluctuates rather more than that of land crops in general correspondence to the relative instability of the water as compared with the soil. A high storm tide, for instance, may carry away on its ebb large numbers of diatoms and materially reduce the food value of the waters over the oyster beds. Such phenomena are readily intelligible. There are others, however, con- nected with the distribution and abundance of diatoms, which are obscure as to their causes. It is a fact well known to students of diatoms that not only their abundance in a given body of water but the species themselves vary from year to year, and practical investi- gators of the oyster beds observe the same fluctuations. In an ex- perimental pond or claire at Lynnhaven, Va., where every effort has been made to maintain practically uniform conditions, the rise and fall of many species has been observed and it was not possible to assign any cause for the changes. Oystermen and oyster growers have indirectly remarked the same fluctuations, as their oysters one year fatten and the next fail absolutely to get into condition for the market, a phenomenon found everywhere on our coasts, but more frequently occurring in some localities than in others. Undoubtedly there are for these irregularities physical and chemi- cal causes which it may take years to elucidate, but for the failure of the oysters to fatten in some localities there are sometimes causes which it is by no means difficult to trace. Like land plants, diatoms require for their growth certain soluble mineral salts, sunlight, and air, all of which they obtain in the water, the medium in which they live. The mineral salts, which the land plant obtains through its roots, bathe the diatoms on all sides, the water deriving them by solu- tion of the materials of the bottom and from the leaching of the soils of the drainage basins of the tributary streams. The former source of supply must be fairly uniform year after year, and the latter, be- ing dependent upon the precipitation, would appear, on the whole, to conform to an average within certain limits, being less in dry years and greater in wet ones, especially when freshets occur. In any given body of water, therefore, with a fairly constant supply of salts in solution there is a certain more or less definite imit beyond which the production of diatoms can not proceed for lack of necessary nutri- ment. To produce oysters of good size and quality a certain mini- 70 OYSTER BOTTOMS IN MATAGORDA BAY. mum consumption of diatoms is necessary, with the exact definition of which we are not now concerned, and it follows from the limitation of the production of diatoms that the production of oysters in any given area is likewise limited. The absurdity of the claim of those enthusiasts who multiply the area of the tidal bottoms of a state by the annual yield of a few favorably situated acres and exhibit the product as the potential oyster production under a system of oyster culture is not difficult of demonstration. Every oysterman knows that on densely inhabited beds the oysters are less likely to fatten than on those beds where the growth is more scattering, and every oyster planter learns sooner or later, either from his own experience or the experience of others, that he will get unsatisfactory results if the density, of his beds exceeds a more or less well-defined maximum; that though the oysters will grow, they will forever remain poor and unfit to market. In many cases the difficulty is attributed to its true cause, the multiplicity of mouths to feed from a limited larder. There is, however, another condition which not infrequently escapes observation—the possibility of overplanting as to area, while main- taining but a moderate average density of growth. Instances are known where the only reasonable explanation of the facts appears to rest on the assumption that this has been done. Im Lynnhaven Bay, Virginia, oysters formerly fattened every year without fail, but the profits of the business were so attractive that eventually a large part of the available bottom was taken up by oyster growers, and coinci- dently there was a gradual falling off in the condition of the oysters in many parts of the bay. With a decrease in the profits attendant upon the inferior condition of the oysters the quantity planted has recently decreased, and on certain areas they were, in January, 1906, fat for the first time in ten years. The oysters are planted more thinly at Lynnhaven than on any other part of our coast, the average being not more than about 100 to 150 bushels per acre; yet by utilizing an undue proportion of the bottom their aggregate demand for food has evidently become too great to be sustained by the natural fertility of the water. That this condition may be repeated in other places there can be no doubt. Unfortunately our knowledge of the food and feeding of the oyster has by no means reached a stage where just what population a given body of water will sustain can be foretold. That determina- tion must for many years at least be made a matter of experiment, but knowledge of the facts above stated may guard prospective oyster growers against a too rash and unconsidered expansion of their busi- ness and dictate care not only against planting too thickly, but against a too gregarious location of their claims. A general knowl- edge of the local distribution of food organisms in any given region is of value, and quite within reach. The survey is able to make some contribution to the subject. OYSTER BOTTOMS IN MATAGORDA BAY. 1a! FOOD VALUE OF WATER IN MATAGORDA BAY. Determinations of the food value of the water in Matagorda Bay were made at all places where the density was recorded, about 120 stations, distributed at approximately uniform intervals throughout the bay, and many additional determinations were made at the anchorage of the Fish Hawk and upon the principal reefs. Ex- planation of the methods adopted in this work, though useful for the information of future investigators making comparative studies of the food of oysters in various parts of the coast, is of: little general interest to the oystermen, and a discussion of them will be postponed to the end of this chapter. The subject of immediate practical value is the general distribution of the food, with the localities in which it is most abundant, and in the following tables will be found a digest of the results obtained by the present inves- tigation. The table on page 72 shows the stomach contents of oysters from five of the principal reefs, with the food value of the water from which these oysters were taken. The first column of figures repre- sents (in heavy type) the average number of each organism found in the oyster stomachs and (in roman type) its corresponding food value. In the adjoining column are exhibited the number and food value of the same organisms found in a liter (24 pints) of the water lying over and about the same reefs. It will be seen that the average oyster examined contains in its stomach about the same quantity of food as is found in a pint of water. | The table on page 73 is a systematic presentation of the kinds and numbers of organisms and their value as oyster food in the several parts of the bay above Half Moon Light. For purposes of compari- son and discussion the bay has been divided into twelve sections running transversely to the shore, and for each there is shown the average food value of each species of diatom, the average of the section as a whole, and the average of each shore and the middle of the bay. The attention of the practical oyster grower is called to the totals rather than to the relative value of the individual species, as consideration of the details is reserved for the more technical discussion. The food value, so called, represents the actual volume or bulk of the various species enumerated found in each liter of water taken at a level of 14 inches above the bottom, the unit of measurement employed being the one-millionth part of a cubic millimeter. A cubic millimeter is about six ten-thousandths of a cubic inch. In cases of organisms which from their small numbers or other causes are unimportant as food, the number only is shown, as it was considered unnecessary to calculate the volume. OYSTER BOTTOMS IN MATAGORDA BAY. 72 B28‘sk | 969‘01 | O08‘Ns | S9S‘9T | OOS‘OL | OS8‘OL | OO*ZT | ToL*ST | 00098 | OS8°SE [77777 TTT ttt Mca * SUISTUBSIO JO JOQuINU [BIOL C26 ‘StF =|: 986‘90T | O6G‘ZE8 | SOE ‘FOL | G00 ‘86% | OLZ‘9ZE | O8Z‘TIG | TS‘P9T | OOT‘S6h | Pa8‘E8T |------7 777" Tie aRT Nae Be ama AN[BA POOF IO ‘AUAN[OA [BIOT, OOF ISS 000°F ; 008 ‘Z FI OL 000 ‘9z SUBOIUT UINI}UIIOIOIg | 6T L88 000°T SuLO}RIP IAY1O | ST tn Ocoee “7° ds Bl[rxdd | LL eam ol ia Ss ds 9T LERG Lo6 00L°6 £90°1 : OPL‘Sh =| OFS “ST_~— |: 000 FG 092 ‘Tz SUBISIP BIISO[OW | CL LsI FOE | 0090 0c0*T ae pI Foo rg9 ‘sg 00L a ; 49'S LSP LT 169° OOL LT G28 "Lg GELS livre wince Sipiialalnjos stewie orm neem cee eae sites oetaers 608 ‘ZL s. ako 2 Z9L ‘OF 5 868 ‘L BYBINUMIMIOD BIPAUAS | ST eens S| Bee ae [nis sSslcimicie Sie minis sisiaic/e leins> cin e/xfeyerc inte cicieie inteinis)eae RyB[nsueR ZI Sso°r 6 gL UWINULISSINUd} IL SIs*t OR ee OOS = es | OS) ey Sailer errs &I GZS ‘ZS BRIG OUD. A806 Wie )5? 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LEE S 962°T | 009°9 | eats | ¢s9°¢ | 006°T | 009°S | L88°s | 000‘0T | 239° \ Se er apart ge COCO ECO B20 snyBoul] é [66 “C6G 098 ‘29 000‘TSZ | SLE ‘bL G18 ‘96 | 00¢‘99 000°92L | SFO‘TOT | 000‘0GE | GZ8 ‘9ZT ; sre‘ l 101 008 OST GG i pilates ote ae al ca a [OT BORDA COT re es ae aS ee a or a SNSSBIO SNOSTPOULOSOD | T “IOJBM | ‘SIOISAQ | “TOJBA | ‘SIOJSAQ | “1OIBAA | “S1OJSAO | “TOJBAA | “S1O}SAQ | “10}7BM\ | “S10}SAQ a 7 aa ‘sotoeds ‘ON ae ‘JOY PUBS] PUN | Joo PUBIS] TENS Joo noABg poyIoy, “Jooy pussy soq -ueyg ett ISU, [‘SUISTUBSIO JO IOQUINU 9]BOTIPUL SeANSyY ooVj-plog “AN[BA POO] 1O ‘SUISTUBSIO JO OUINIOA 9}BOIPUL SoInSYy UBUIOY]) ‘HALVA\ AHL NI SINTALMSNOQ GOOY ANV AVG VANODVLV] AO SUTAY TVdIONIUG WOM SUALISAQ) dO SINTLNOZ) HOVNOLS OYSTER BOTTOMS IN MATAGORDA BAY. PL9‘S9L | 0G2'Z8s | GFS‘8E% | GLO‘68L | GZL‘ecT | OLA ‘6 | Gz9'ZTS | SIP‘FIS | OGP‘SSL | 6FO ‘OBL a1OYs BINSUTUAg QZG'ZGT | OG9'LGS | G26‘Z8T | 66S °98T | G26'FGs | O06‘LLE | OS8'FLc | 000'292 | OOG‘GHS | FLL ‘6G |~ TT TTT TTT tte eq JO o[ppuUN DIOS OS LANE MOA! || Oolsocsye EO) Kee |) epeteyeray ASME AME Sr “| ido) tatere. | Mers Nrdeenita: ||/P2Roe DSO coCop aoc oa corisoeassno00 dIOYS OLLBIg F96°9T =| OG2°SE | LOST | OFS*ST | GEREL | OSL*FT | OSG°ET | S80°0R | OSL*TE | S68°0S | OTF‘9G | SOLES [- 777777777777 “stUsTUBSIO Jo IoquINU [BIOI, 98¢ ‘TST GLO'LLT | G6L‘L9T | ORG‘09% | O09'FEE | GL4Z‘8LT | GzG‘99L | OF9‘LLT | OSO‘#8z | ShL‘TLZ% GHONOIG lotsa ae “"*--ON[BA poo} IO ‘9UIN[OA [RIOJ, L99°T oc? £80°S Gal‘ &E8 GLE 00¢ ee ae OSa'T | OSs‘ 669°S Paacereercor 699‘Ir | ocz'a | 1sc'rt | qzg‘s CeehGuies |KCGCOkG, eal OGG ie ule-so ona ea TOG Hane mINOayIR CLE ‘ST Assad vacates pore 00¢ OS'S PRG Gy Serre oy "SRG@aies Abliaage* "") 000ST 008 0937 ieee SOLO RID RLo NG) pees SaINOGy 001 Gor L91 0&3 0&6 (Yee epaanre aes || eeeceneren| OC ee cecon [occ heck re ia ea ee a ose ooo a OREN 88 yA shes oleae a aan kana Pom realou sont Casiang! eon Be ee eae ae G 000 ae haa I 806 £8 OB OSGr Me, ci tosaes secs te anaes - prcssesorsiseneesson*| Qge‘etT | 000'02 |"77"--"7"-"| 000‘0E | 000‘0z | ogt‘st | ooo‘cs | ope‘ez | oFg‘so | Oog‘zc SOGHETD Sareolers 991‘ 00¢'T G28‘ 991 TFS 009°T 0&3 0¢9, 008 $80°T ess, QOS ee ehe sarees nese ease ee eeeaee eee opr loses loons [ae | tors |sre'r loons loser | ooees |onoer | overs | seo. 9995T 0G6°S 80F°S 3 0¢9'T 00¢°98 ; 00956: WNO0%Sn Whesasccceentes cseneete oe 991 ‘T gig‘'tT | 989‘T _| aF9 LIg‘t | 296 Oor‘T keer's | oce‘ez | o0r'6 | oc9‘9 | 009‘¢ SPORE aS SLL Caer seals BRR. ose sees LEO 991 GEL OSG ate, oe al oe ee Spe | Bears ha hate Ee ae rofeur ByBlnsuB 688 oes &88 99t OG! 008° 00¢ GE 363 GLE “77> UIMUTISSITL00} &8¢ foes weaeOv. 991 Sry OSes [ee amr ae OOO pea eal CGH We eas oem a Siete: Ber Ses ane aa BOG * UIT petdseyUr OSG Oc! Fela ete TA Fae he as sr c| oh bee gl Saal Rae ae BB C15] eae a Nene ei al lane sy ae ES 2 ROS Oa et ACE) urninosqo 991 ina aan 991 oon ae 2et “"""* BIOLOSB] BUISISOINI[T 8&8 0¢ 98 aches d q OE ee eS sce OG illiaemecenesc ane ate cee ence econ 699 ‘T ogz'e | ogg seaNese set l CesT me lVGC0 om wt eceac re rIKONd: ae ace ---*-] G79 i Lato sender hess L915 00ST | 0005 | &8¢ 366 928°T 00st | $29 SSF, G28 \ einiele ajc wns bdin’e @oisiab/ae gam mauane 0ZF‘G 0g ‘8 00g ‘% SSF 'T 082 Ser ‘es 0¢4 ‘8 889 ‘T GPL ‘T 186 : 09% WE oy ain, 2 OS3'E | LIF 09% 093 o1F 991, GBT \anwmenecen sterner sees -=++=*-gondiqqa ne rd Agate =§ ee 00¢‘ZE | OLT'F 00¢ ‘% 008 ‘% O9L ‘Pb 099 ‘T pa fi wh It 81 | B66 0G3 Take See 000°T G18 &89 Gp sawethe eer eeeee Be ee See 180 a2 810" % | GIG'g Og sneer areas 000‘Ir | ¢c9‘6 | str‘9 | eat'P f | MUAY OI 38 6o'T 199°S 806°S | G28°% 000°S 096°% L16°% OGUST.. “Wiseraheoses sates scares R6F ‘8 ost‘6 | zoo‘or | sra‘er | oGe ‘ZT 000‘%E =| O9L'ZE | zoc‘zt | o0¢ ‘or | es oak ie : 000°F 00g‘+ | 68's | 999°¢ | 999°F | G28‘8 09a'¢ =| S80'F_ | ctor | S8FS \ Go cesaaan neem Saco -- snyeauly 000‘OFE | OOS‘ZGT | OzL ‘SIT | OLe‘S6L | OLS*s9T | G29 ‘GEST OGL ‘E8L | G06‘ZFT | OLE ‘TFL | G08 ‘TOL g EE See amee =” "1008 c6L G63 GLE 0&3 Dh (Cee eee Se 00¢ pers "To oesse==""" SNSSBIO SNOSIPOULOSOD) : rales s ‘Ss[BU ‘Ss[Bu [BUSS “sJoor *sJool ‘STVUSIS | ., = |} cerns -yulog ’ ae ue -SIS OT TUT | -3Is oylur | UOrT[IA pueysy pues, | oxVT geeene eee Surssoiq Avg Sutssoaqy pus ajar “UdADS | -90INL | -Bd PUB |[[EeYS Puy pRIT PUB] pUB ISO AA punoj ust aAOqy HBO OATT pure sey) -UdA0g pue o[rut pus pus] puevys] puv[st puvy[s] qstH |pue pues *soroods usemjog |uoomjog | POUL | uoABd) sod =H Teds PBN | woaMjag | uooMjog UsaM Jog | WaaM jog | UWadM jog | WaaMJog | UaaMJog | TaaMIO . aa Sil “te i sl » “aA ‘a ‘a 19) ‘a “Vv qT §1 ol [SUISTUBSIO JO JOQUINU o,BOTPUL SeANSY oovJ-plog “ON[BA POOF IO ‘SUISIUBS1O JO DUIN[OA 9} BOIPUL SaINSyYy uBuTr0yzy] “AVG VAHOOVIVI JO SUMLV AA HO HNATIVA GOO 74 OYSTER BOTTOMS IN MATAGORDA BAY. It will be observed that while certain parts of the upper bay— notably the middle of section I—are prolific in oyster food, the gen- eral average is lower than below Dog Island, where the food value per liter (14 quarts) of water averages 251,327 units, as compared with 189,490 units above that reef, an excess of about 33 per cent. In the lower bay the greatest fertility found anywhere during the survey was in Tiger Island Channel, where there were 493,100 units per liter, an extraordinary figure, due mainly to the abundance of one large diatom, Coscinodiscus lineatus, ordinarily found on or close to the bottom, its unusual abundance in the water specimens being doubtless due to its being lifted and carried by the strong currents. This locality would be a valuable one for oyster culture, but its use for private ends is prohibited by the fact that it is now and has been for a long time a natural bed. It is an interesting fact that the sec- tions (EK and F) immediately above and below this are practically less productive of oyster food than any in the bay, and so far as sec- tion E is concerned, it is the portions nearest Dog Island Reef and along the north shore which are most deficient, while on the south shore, near Forked Bayou Reef, it is especially rich, a quality reflected in the fatness of the oysters on that bed. In sections C and D, lying between Lake signal and Shell Island Reef, the waters of the peninsula shore are more fertile than either the north shore or the middle, the food value being about 27 per cent greater than the former and 17 per cent greater than the latter. Far- ther down the bay, in sections A and B, the middle of the bay is most richly laden with food, exceeding the north side by about 29 per cent and the south side by not less than 60 per cent. The middle of the bay, in section B, about opposite Oyster signal, is the richest water above Half Moon Reef. Above Dog Island Reef the most fertile water lies generally in the middle of the bay, but with the exception of the middle of section I this belt is much inferior in food produc- tion to the best parts below Forked Bayou, the difference being about 17 per cent. The poorest water above Dog Island Reef hes, as might have been expected, close to the mouth of the Colorado, and the best is in the middle of section I, between Middle and Boggy lumps, where a really high degree of fertility is reached. The excellence of the food supply in this vicinity is reflected in the fatness of the oysters on Boggy Lump, a condition in which Middle Lump would undoubt- edly participate were the growth there less badly clustered and musseled. The method developed in this report of estimating the food value of waters is new, and there are no definite data for comparison; but it is the opinion of the writer, based upon general experience, that any water containing over 200,000 units of food organisms per liter may be regarded as good, while over 250,000 is very good. In any event there OYSTER BOTTOMS IN MATAGORDA BAY. 75 is evidence to show that a food value of 250,000 units will in a mod- erate current produce fat oysters on a moderately dense bed, while 350,000 units will have a similar effect upon a very dense bed, like Boggy Lump, exposed to currents of less velocity. The production of oyster food in Matagorda Bay, therefore, can be considered on the whole very satisfactory, and sufficient to support a vastly greater oyster population than now exists. Taking into consideration not only the immediate abundance of diatoms, etc., but the size of the area over which they are distributed, the most favorable location for oyster planting, so far as available food is concerned, lies in the middle and on the peninsula side of the bay from just above Forked Bayou Reef to the extreme lower limit of the survey, a large extent of extremely productive water. METHODS EMPLOYED IN DETERMINING FOOD VALUE OF WATER. In the investigations of the oyster food of the waters of Matagorda Bay the methods pursued were as follows: The water specimens, one liter each, were taken by the survey party wherever density observa- tions were made, at average intervals of about 1 mile, and, inclosed in tightly corked bottles, were carried back to headquarters at the end of the day and filtered. The filters are agate ware or copper fun- nels of 1 liter capacity, the small end being closed by a perforated cork, over which is stretched a piece of fine bolting cloth supporting a one-half inch stratum of well washed and sifted sand, fine enough to pass through no. 11 bolting cloth, but too coarse to go through no. 1. As the water in the funnels falls the walls are washed from time to time with filtered water from a wash bottle or a pipette, so that practically no diatoms or other organisms will adhere, and when the specimen has entirely filtered the walls are given a final rinsing, the cork is removed, and the sand washed with a small quantity of water into a vial or small beaker. The precipitate is then energet- ically shaken and the liquid immediately decanted off into a gradu- ated vial, a small quantity of water is again added to the sand, and the process repeated. As the sand is much coarser and heavier, it at once settles, while the organisms are carried off by the successive washings and collected in the vial, sufficient water then being added, or abstracted after settling, to bring it to a standard measurement of 10 c. ce. A few drops of formalin will preserve the organic contents of the precipitates, which are kept in vials appropriately labeled until such tyme as they can be examined. This method of filtration is more rapid than that of precipitation usually employed, and, more- over, the latter can be used only with difficulty on a rolling ship. Comparative tests show that they give approximately equivalent re- sults. One cubic centimeter of the precipitate is then transferred to a Rafter cell and the diatoms in ten fields each 1 mm. square are iden- 76 OYSTER BOTTOMS IN MATAGORDA BAY. tified and counted, a second specimen is examined in the same man- ner, and the sum of the twenty counts multiplied by 500 gives an approximate to the total number of diatoms of each species in the original liter of water. In former reports the writer has offered the total number of diatoms as an index of the food value of the water, but his experience in experimental work at Lynnhaven has shown this method to be subject to grave error even as applied to a limited region and to be very untrustworthy for purposes of comparison be- tween different regions. As the species of diatoms vary widely in size and fluctuate in relative abundance, it often happens that a mul- titute of small ones give a fictitious value to a water specimen as com- pared with another specimen containing a much smaller number of a species of vastly greater volume. This is well illustrated in the table on page 73. Comparing the water of Tiger Island channel with that of Forked Bayou Reef, we find it to be but one-half as rich in individual diatoms; but its food value, as computed by the method hereafter explained, is found to be almost exactly one and two-thirds as great, a disparity produced by the comparative abundance in the former locality of Coscinodiscus lineatus, the largest diatom enter- ing into the dietary of the oyster in Matagorda Bay, and in the latter place of Synedra commutata, the smallest species of importance. Grave* has recognized this and improves upon the previously em- ployed method by disregarding in his report the smaller diatoms and tabulating the larger, more important ones by species. His results as published are interesting and valuable, but are difficult of com- parison one with another and are still more difficult to bring into relation with results obtained by the same method in other regions producing diatoms of other species. Moreover, an error in the iden- tification of the species, which may easily happen with persons not specialists in the group, would entirely vitiate the results for pur- poses of comparison by other workers. And finally, there is often wide diversity in the sizes of individuals of the same species, some- times small and again large ones predominating. In the present paper an attempt is made to estimate the actual vol- ume of the oyster food in such manner as to make the results readily available for comparison. To this end each species was carefully measured in length and breadth and, wherever possible, in thickness. In some cases the latter dimension was calculated proportionately from published figures or estimated from the known thickness of a related species. From these measurements and the figure of the diatom its volume was calculated by ordinary methods, and this result was used as a multiplier in arriving at the results shown in the tables on pages 72 and 73. It is not contended that this method is absolutely accurate, aGrave, Caswell. Investigations for the promotion of the oyster industry of North Carolina, Report U. S: Fish Commission 1903, p. 247-351. OYSTER BOTTOMS IN MATAGORDA BAY. ee but it gives good approximate values readily available for compar- ison with other investigations made by the same method and will in a measure place the study of oyster food upon a volumetric basis. It has the advantage also of placing less importance upon the abso- lute identification of the diatoms, for if the measurements be accu- rately made and the figures carefully drawn the volume can be calcu- jated without reference to the exact names of the species. The unit of measurement adopted in this report is that employed by Van Heurck in his Treatise on the Diatomacew, the one-hundredth part of 1 millimeter (0.01 mm.—0.0003937 inch), referred to as a “ec. d. m.” (centiéme decimeter). The unit of volume, which is re- garded as presumably the unit of food value, is of course the cube of this, or one-millionth of 1 cubic millimeter (0.000001 ce. mm.). It follows from this that when, as in section A of the table on page 73, the food value of the water is said to be 219,342, it is meant that in absolute measurement 1 liter of water contains diatoms of an aggre- gate volume of about one-fourth of 1 cubic millimeter. In order to make the results of greater value for comparison and to render them susceptible to recasting to accord with such improvements as may be introduced into the method above outlined, there should be given for each species, or at least for all of the important ones, the following data: Name, or the name of closely allied species; outline of its figure; average length, breadth, and thickness, preferably in e. d. m.; its calculated volume; the number per liter of water, as determined by the Rafter method. Ordinarily it will be unnecessary to furnish these facts for all of the species, as it will be found that in any region from 4 to 8 organisms constitute the great preponderance of oyster food and the other species found are negligible for all practical purposes. In Matagorda Bay there were found in the stomachs of oysters about 25 species of diatoms and 1 infusorian, but over 98 per cent of the food in bulk was: contributed by 8 organisms, Coscinodiscus lineatus, C. eacentricus, Navicula didyma, N. elliptica, Synedra commutata, Synedra sp., Melosira distans, and Prorocentrum micans. The figure and the actual numbers of each species in each locality will be found in the accompanying tables and illustrative plates, and all the other data in the following notes on the several species. The identifications were verified by Dr. Alfred Mann, and with one or two minor exceptions are authoritative. The measurements given are the average dimensions of a number of indi- viduals of each species. DESCRIPTION OF ORGANISMS CONSTITUTING FOOD OF OYSTERS IN MATAGORDA BAY. Coscinodiscus lineatus Ehrenberg (pl. xu, figs. 1-3) is a large circular diatom, which on account of its bulk and general distribution 78 OYSTER BOTTOMS IN MATAGORDA BAY. is the most important food organism of the bay. It is found in practically equal profusion both above and below Dog Island, and an examination of the stomach contents of the oysters from the prin- cipal reefs shows that it constitutes about 63 per cent of the food. It lives on or near the bottom, and is suspended in the water most abundantly in the presence of strong currents or energetic wave action. Average specimens measure in diameter 5 ¢. d. m., thickness 1.75. c. d. m., volume=0.78 (d?t)=85 cu. c. d. m. Coscinodiscus excentricus Ehrenberg (pl. xu, figs. 4-7) is a small circular diatom practically uniformly distributed, excepting in Live Oak Bay and the waters above Dressing Point, where it is deficient. In its vertical distribution it resembles the preceding species, and its numerical abundance is about one-half. Proportionally to its abun- dence in the water it is consumed in larger numbers, but owing to its smaller bulk it constitutes but about 10 per cent of the food found in the oysters’ stomachs. Measurements of average specimens show the diameter 2.25 c. d. m., thickness 1.7 c. d. m., volume=0.7 (d?t)=6 Gu. God. am. Navicula didyma Ehrenberg (pl. xu1, figs. 7-11) is an 8-shaped dia- tom, found in much smaller numbers than either of the foregoing and not so universally distributed. It was altogether lacking in four sections, and is considerably more abundant and constant below than above Dog Island Reef. It constitutes about 1.8 per cent of the food of the oysters in the lower part of the bay. Average specimens measure in length 4 c. d. m., breadth 2.25 ¢. d. m., thickness 1.8 e. d..m., volume=0.7 (1XbX 8 ao we 8 aes as best Serta osg at aes ae aq =AROD Sst e| BORA BAL WwW a a 2 ero} dq OYSTER BOTTOMS IN MATAGORDA BAY. (CS: merically about one-fifth, and in volume about one-eighth of the available oyster food. Like the preceding species, it is taken up by the oysters in relatively large numbers, and constitutes about 3.4 per cent of their food. Average specimens measure in length 10 c. d. m., breadth 0.75 c. d. m., thickness 0.75 ¢c. d. m., volume=0.65 (IXbXt) = 5.) Cu. c. d. m: Melosira distans Wiitzing (pl. x1, fig. 3) is a circular diatom fre- quently aggregated by the circular faces to form filaments. It is much more abundant below Dog Island, and is entirely absent in Live Oak Bay and above Dressing Point. Between Mad Island and Half Moon reefs it comprises numerically about 12 per cent, and in volume over 25 per cent of the food contents of the water. It is taken up by the oysters in about the same proportion relatively to its abundance as (. lineatus, and in the lower bay constitutes about 12.3 per cent in volume of the stomach contents. Average specimens measure about 3.3 c. d. m. in diameter and 2.3 c. d. m. in thickness, yolume—0.78 (d? . MEL By 5 ZS Ks x hs Va! oa a) s | SWS sg | 4 mo yy 7 Sr 3 a 0 1 . \) ! e % S \) put (as I is Ne e rE es ri Ys : . = = Ny Fy =< . ie = DEPARTMENT of COMMERCE ano LABOR BUREAU or FISHERIES OF PART OF i < Le SHOWING LOCATION OF OYSTER BEDS Grass : DEPTH AND SPECIFIC GRAVITY OF THE WATER aA t a AND CHARACTER OF THE BOTTOM B a= =. # ae th A FR “= —— 3iGrass Lump | = OM A SURVEY MADE UNOER THE DIRECTION OF ba At A i H.F. MOORE MordS ere on Tt Occemacr 1904 to May 1905 (od 3 Marte a } . jl Boggy Lump Eleven Explanation of Symbols Mor23 (8020 44,25 10080 ~ "™S Oysters, very scattering, beds averaging per acre /ess than 25 bushels of oysters over 3 inches fong ay NT Oysters, scattering,deds averaging per acre batuseen 25 ond 100 bushels of oysters over s inches long Ks ” Mar20, (0052 tant 0c ® Oysters, conse, beds averaging per acre more than 100 bushels of oysters ove nehes long | ar 25 (0065 abe aa - Reefs ond shell banks exposed during low winter tides 1M ar 2B BONE 4imM Mor? ai Dote ond Figures in red indicate bottom density of water and dote of observation 8.46.3 figures inl dicate depth in feet af mean low water in winter ied Are Coost Suri triangulation stefi used in the present sur 4 26 1OON8 a eM a oos vey ongulation stefions us vey A Lh Mar BS Loos? yew ot es Ook Say. e Triongulortion stations established for the present survey | “ “ ce Mey tw. . eS ~ ie = 3 ee ial a “ j Middle Lump as 3 Mort long co : Abbraviorions ° M ee an eo apn hee 5 k Sp sond wo Shoals oe Marts (00s? poo ? © pram hord Mud } Lending an ead sofr Mua Nauncal Miles shorts (0957 4 warez 10060 AE Beds ainw reese 0058 i] 20 19055 k ak O57 Porm Seq . va i rE Lh) r NOM fe oe fen gen eee sonal Mong 08 oy ay ( -_ s oe } PO rrr sy acne ro 2 Ee yn meee ue SN beayens one sty a ee ae a i 2 a Bose, /883 (foragorda) 2. ‘She AGG 7, ; es a Meneeere oO | los B® sh OW in t a a = uN