TPWD 1955 F-6-R-2 #153: Inventory of Species Present in Lake Corpus Christi

Job Completion Report by Alvin Flory TITLE Inventory of Species Present in Lake Corpus Christi. OBJECTIVES To determine the species present and their relative numbers in Lake Corpus Christi. PROCEDURE The investigation of Lake corpus Christi was divided into three Jets: Job Ae3,lBasic Survey of Lake Corpus Christi, to gather fundamental data on the chemical and physical characters of the lake, Job Bm6, Creel Census and Check of Commercial catch of Rough Fish from Lake Corpus Christi, to estimate the total catch of fish from the lake, and the present job. Refer to the job completion reports on the basic survey and the creel census for_their applications to this job. Job Em2, 'Experimental Provision of Cover for Game Fish, began July 1, 195h and is still in progress. Project lemD, Lake Corpus Christi water Hyacinth Control, was begun on September 25, 1953 and is still underway. The present job consisted of making monthly seining and experimental net~ ting collections at nine stations on the lake. Hoop and fyke nets and 2" and 3" gill nets were used_sporadically to supplement the data gathered from the regular stations. The information collected was kinds and relative nowhere of fish in the lake, sizes and coefficient of condition, sex and sexual condition, feeding habits, parasites and the seasonal changes in the whole population. a. Netting Collections. 1. Nine stations as shown in Map l were selected in Lake Corpus Christi to represent different locations and types of habitat. Station l.was about ls feet deep with a silt bottom and was exposed to winds from all directions. The prevailing wind direction was south or southeast but changing weather brought east winds, generally moderate, or moderate to strong west winds. During the fall and winter months strong north or northwest winds were to he expected. Station 2, north of a'sandy point of Dennisons Slew, was from h to 10 feet deep with a bottom of fine sand and silt. It was exposed only to west winds. In September of 195% a willow brush pile was bdflt near the beach at this station to furnish cover for game and forage fish. Station 3 was northwest of a point in Pernites Creek; 6 to 10 feet deep with a silt bottom; the set was made across the channel of the creek. It was well protected from the wind and was within 100 feet of dead mesquite trees holding beds of water hyacinths over deep water. Station 4 was off the moderately sloping beach at the Boy Scout Camp; 60 to 10 feet deep with a fine sand to silt bottom, it was exposed to the prevailing winds as well as to west winds. Rather small beds of ' 2 . f 3' Potomo eton in about 2 to 5 feet of water furnished some fish cover. Station 5 was about 8 feet deep with a silt bottom and exposed to the northeast. It was across an old creek channel and on the offshore end was adjacent to many dead mesquite trees. Station 6 in the upper end of Coffin Bay was 5 feet deep with silt bottom. The prevailing wind crossing a wide stretch of open shallow water usually kept this station very turbid. Station 7 was distinctly different from the others. Locat ed in Beldon Hollow, it could be reached only by a ranch road because an imu penetrable bank of water hyacinths about 1/4 mile wide choked the mouth of the bay. Through the courtesy of.Mr. H. D. Miller, we were granted access to an area of about 30 acres in the northwest and of the Bay which remained free of hyacinths. The banks and mouth of the Bay were covered with a solid mass of hyacinths held in place by mesquite trees killed when the lake was filled. Surrounding hills gave the Bay . fair protection from all winds. The water depth was about 8 feet and the bottom was very soft, made up of silt and decaying hyacinths. The water, especially when low, was clearer than that of the main lake and often had a brownish cast. Station 8 was 7 to 12 feet deep with a silt bottom. The net was set across the channel of the mucosa River about 1/2 mile above the head of the main lake. High willow trees along either shore gave good wind protection. Station 9 was 15 to 18 feet deep with a silt bottom. It was very similar to station 8 in the sharply cut banks and high willow trees protecting it. The scouring action of flood waters down the channel kept these two stations rather deep and the protection from winds allowed the water to be relatively clearer than in Coffin Bay or the main lake except dorm ing the flood stages. All depths given above were measured when the lake was full (7h feet above mean sea lr“vel..) For the fluctuations in the lake level during the two segments, see Job AsB. Experimental gill nets composed of 5 sections of varying size mesh (1", 3 , 2", 2§‘ and 3" square mesh) each 25 feet long and 8 feet deep were set at each station each month except when conditions prevented. In the first segment stations 5 and 6 were missed in July and August due to low water and station 7 was missed in August and hecember due to low water and a rain which blocked the access road. In segment 2, all stamens were set each month. A total of 210 experimental gill net collections was made. All nets were sinkers, resting on the bottom and reaching the top of the water only where the depth was less than 9 feet. Galvanised ring weights on the bottom line and plastic floats on the top line kept the nets stretchm ed vertically while 2mquart concrete weights (about 12 pounds) and lines to sure face floats or tree limbs kept the nets stretched horizonally. Normally two or three stations were set at one time, about t or 5 P. M. and the nets were picked up the next morning between 7 and 9 A. M. Stations 1, 2 and 3 were usually set in the first week of the month, t, 5 and 6 in the second week, 8 and 9 in the third week and station 7 in the last week. 2. Sill nets with 2” and 3” square mesh were set at various times and places around the lake to try to locate spawning and feeding areas. During the two segments, t nets 100* a 89 with 2“ mesh, 2 nets 1009 by 8? with 3" mesh and 30 nets 300“ by 83 with 3“ mesh were set. Most of these were set in Beldon Hollow near Station 7 but several were set near hog Island, in Pernitas Creek, the river chaos nel and one was set in Coffin Bay. The information gathered from these nets was recorded in the same way as that from the experimental nets. Although of little use in locatingspawning and feeding areas, these nets did help in getting inform mation on the larger fish of the lake, especially the smallmouth buffalo and blue catfish. 3. Ten 1" square mesh hoop nets seven feet long, four feet wide at the mouth and with two throats were set during the job at various times and places. One of these sets was made near the beach using two 50’ x 6* seines with %" mesh as wings. The others were stretched open by tying them to three poles and baiting with cut fish or cottonseed cake. Data gathered was recorded in the same way as 3. for the experimental gill nets. Two near shore ”heart sets" were made with %" mesh fyke nets 7 feet long with four foot wide mouths and two throats. The fykes were 15 feet long by four feet deep. The fish from these sets were tabulated and recorded as those from seining collections. h. The fish taken in all gill and hoop nets were brought back to the State Park (except from Station 7) for processing. All fish were laid on a measure ing board and the standard and total lengths in millimeters recorded (except in a few cases when large numbers of freshwater drum were caught they were only counted and weighed). Each fish up to 500 grams was weighed on a Hanson platform scale, larger fish were weighed on a Perfecto hanging scale (to 20 lbs.) or on a beam scale (to 200 lbs). Pounds and ounces were converted to grams for recording. When food was found in the stomach of a game or predatory fish, the stomach was removed, tagged and preserved in 10% formaldehyde. Special notes concerning the fish such as worms, stunted, etc., were noted. Scale samples were taken during much of the first segment but study of them in thelaboratory proved of no value in determining the age due to the warm winters here and consequent absence of distinct circulli. All fish handling for a catch was done by one field assistant while the other rem corded the data called out to him. ”K“ factors and contents of the stomachs were calculated later in the lab. Table 2 is a typical netting collection record sheet. b. Seining Collections. 1. Nine seining stations were selected around the lake at or near each of the netting stations. Station 1 was on the west shore of the main lake exposed to the north and cast but protected from other winds by high willow trees. The beach was gently sloping with a fine sand and silt bottom and small beds of Potomou geton grew in about two feet of water during the summertime. Occasionally water hyacinths drifted onto the beach and furnished more cover for small fish but made seining difficult. Station 2 was well protected from the wind in the north fork of'Dennisonis Slough. The banks were sharply out from sandy loam and the bottom was of slippery silt. water depth was to to four feet and small bunches of hyacinths furnished.fish.cover. The whole slough was choked with hyacinths a few times which prevented seining. Station 3 was on a gently sloping easterly exposed beach in Perm nitas Creek. Many stumps and drifting hyacinths made seining difficult or, at times, impossible. The bottom was silty. Station h, on the Boy Scout Beach, was moderates 1y sloping with water depths up to four feet and a fine sand to silt bottom. Beds ‘of ggtomogeton and floating hyacinths furnished cover. Station 5, just inside the entrance to Coffin Bay, was protected from wind except those from the north. It has a moderately sloping beach of silt with some Potomogeton and hyacinths for cows er. There were seweral submerged stumps in the water up to three feet deep. Stew tion'6, in the upper end of Goffin Bay, had a fine sand beach grading to silt in the deeper water. The slope was gentle and exposure was to the south and east. A bad of'Scirpgg furnished some cover near the beach. Station 7 usually had relativem 1y clear water up to three feet deep. The bottom was gently sloping and of very soft silt and decaying hyacinth plants. Collections were seldom good or complete due to dead plants clogging the seine and the hyacinths along the edge made it necessary to lift the sane from the water rather than dragging it out on the beach. Station 8 had a sharply cut beach to about t feet deep with a few hyacinths and often some green algae along the edge. The bottom was soft silt. Station 9 was in a small secondary channel shows Legarto Bridge. The beach was gently sloping, the bottom of very soft silt. Floating hyacinths furnished some cover but masses of them sometimes prevented seining. The banks of the main channel were too deep and sharply cut to allow seining. Whenever possible, the seining was done with a: 30' x 6‘ bag seine with %” knotted mesh. Where water hyacinths or stumps pretented the use of this seine, a 15? x h“ common sense seine was used. A sample of the fish seined was preserved in one quart fruit jars containing 10% formaldehyde and sorted, identified and counted later in the lab. Excessive numbers of a single spew a '{I', he cies or fish too large for the jar were counted, recorded on the fish card and dis» carded at the time of collectiono Seining was usually done in the last week of the month except at stations 7,8 and 9 where seining was done on the afternoon that the experimental nets were set“ Of the 216 seining collections scheduled, 166 were madeo Low water conditions prevented access to Station 6 due to shallow, stumpy water in Coffin Bay, water hyacinths sometimes drifted onto some of the beaches in such large masses that seining was impossible and once the water level was so high that seinn ing was prevented during the last part of the month because water was backed up ion to thick terrestrial weeds and brush on all beacheso co Data concerning weather and water conditions and other observations were kept on Fish Cards and Fish Gollection Sheetso A description of the lake and' its chemical and physical characteristics was given in Job Ae3a FINDINGS The seasonal variation of fish activity; as reflected by comparison of the monthly seining and netting catches} may be seen in Tables 3, t, 6, 7, 9’and 100 Tables 9 and 10 show the average catches of seines and nets for each month of each segmentn Above this graph is shown the average temperature.of the water at Station 1; just above the dam, and average water level of the lake for each month. There are two apparent peaks of fish acthity in Lake Corpus Christi during the year; the most prominent one is in the spring beginning in January or February and reachw ing a posh in April or Mayo The second is in the fall from August to November, it is not so distinct as the spring peak and lasts for a shorter period. Considering the larger fish.taken in the experimental nets first: the numbers of fish taken per net in the spring of l95h began to rise in January and continued to rise to a peak in April, then dropped off in May and Juneo The water temperature likewise began to rise in January from about 57 degrees Fahrenheit to Th degrees in Aprilo The temperature dropped in March but seemed to have no effect on the increasing net catch, probably because the deeper water in which the nets were set was not affected by the dropa During this period of increasing net catches the water level of the lake was dropping continuously until midmApril at which time it rose to about 73 feetw The rise dropped off in May but another came in June with a drop in the fish catch during those two monthsa In the spring of 1955 the not catch again began to rise in January, leveled off in.February and March, made a small increase in April; than reached a peak in Mayo The average temperature at.the dam started to rise in February? leveled off at 72 degrees in March and April} than rose to 79 degrees in Mayo The water level rose about 1% feet in Febm roaryy then dropped until Mayo Therefore the spring run of fish seems to be core related primarily with.the water temperature and to some extent with the rise of the water levelo This increase in fish activity in the spring run is a spawning and feeding rung Tables l6 and i? show the sexual condition-of eight common species taken in gill nets in each of the two segmentso Sondition 1 indicates that eggs or sperm were flowing, aggonads well developed; 3, acres discernible, h, sexes not discernible and 5 indicates that the fish had just spawnedo In the first segment the number of fish that were ready to spawn or had just spawned increased from 3 in March to 21 in April} dropped to l"1 in May and to l3'in June, 10 in July and l in August. In the second segment the number of fish ready to spawn or just having spawned began with 32 in February {when the lake level rose but before the main lake temperature had risen); dropped to 10 in March; then rose to l? in April and 16 in May together with the increasing water level and temperaturec By June of 1955 only 3 fish were taken that had already spawnedo The fall run of netted fish in the first segment secured in August along with a very large rise in water level from 69 feet to 77 feeto In the second segw mentjthere was a small rise in water level in September with a corresponding small increase in catch, another in October with a drop in fish caught and a third rise r. 30 ‘ r in water level in November with a pronounced increase in the number of fish caughta The high summer water temperatures dropped gradually in September and October and then dropped to 63 degrees in Novembero This fall run is probably mainly a feeds ing run resulting from a change of water and temperatures but three fish, a spots ted gar and a smallmouth buffalo which were ready to spawn and a channel catfish which had just spawned? were taken in November 19540 During both the spring and fall runs many fish were taken with full stomachsw The seining collections show an apparent increase in the numbers of small fish in the spring but not in the fall» The small fish which live in shallow, near shore water react to temperature changes more definitely than do the larger fish taken in the deeper waters and also; the seining collections are probably more subs ject to sampling errors than are the netting collectionso In segment 1? the avers age number of fish seined showed an increase in March, apparently the increase in water temperature which occured in Februaryl The drop in temperature in March caused a corresponding drop in fish seined in Aprils The rise in temperature which began again in March} together with rising water level caused the small fish popum lation to reach a peak in Mayo Further rises in temperature and water level in Junefwere accompanied by a decrease in the numbers of small fish takeno In the second segment, the small fish showed a rise in frequency in January despite the fact that water levels and temperatures were still droppingo The catch then drops ped off despite rising water and temperatures These may both be cases of sampling errors The main increase in the small fish catch came in June, a month later than the distinct rises in water level and temperatureo These small fish taken in seines produce tremendous numbers in a short time and are reduced to small numberszgain very quichpo DISGUSSIOH 0F INDIVIDUAL SPECIES The numbers of each species of fish taken in the different months of the job may be found in tables 3 and To The pounds of larger fish taken in the experw imental nets is listed in Table to The numbers of fish caught at the nine differs ant stations during the job is shown in Tables 5 and 8; The rank of each netted species, by number and weight and minimum? maximum and average standard length} weight and "K” factor is shown in Table 150 Table 16 shows the sexual conditions of the eight most common fish taken in nets during the job and Table 18 summarises the results of stomach analyses of 191 stomachs examinedo Other details of each species will be discussed in the following sectiono heoisostegs‘spatulaam Alligator dart Rather common and of a large size? occuring in alignrts of the lake, they were frequently taken on trotlines by fishermeno Three taken by a commercial fishermen were examined that weighed a total of 360 pounds; one of these had a freshwater drum in its stomach which was 200 mag in standard lengtho One stomach taken during the job contained an unidentified fisha Spawning apparently secured in April and may as two fingerlings were seined in June and another in Julyj all from beds of Potonogetonu The adults were usually infecm ted with tape worms in the stomach and intestine and fish lice and small leeches were found about the head of several specimenso Individuals of over 200 pounds were reported caught by commercial fishermeno Lepisosteus_productus m Spotted Gare The most common gar of the lake; they were found in all areas and were serious pests by stealing trotline baitsa From our netting data they did not occur as frequently in the open water of the main lake as elsewherea Two fingerlings were taken in February and March, 10 in June and 5 in Julyp all from beds of Potomogetong Many adults taken had well developed gonads during all months? but only one was taken with eggs flowing; in November 1955» Specs inane that had just spawned were taken in Aprilj June and Julyo Many were found with tape worms in the stomach and intestineso Sex ratio 115 males, 111 females, 33 not discernibleo 6. Lepisosteus osseus m Longnose Gar. 0f common occurrence in all parts of the lake except that none was taken in Beldon Hollow; Females that were flowing eggs or had just spawned were taken in April, May, June and July. Three fingerlings were taken in Janet As with the spotted gar, these fish seemed to be less abundant in the open water of the main lake and preferred near shore water, creeks and the river channel. Some were infested with tape wormso Sex ratio, 65 males, 2% fem males, 19 not discerniblea Dorosoma petenensis m Threadfin shad. The most common and prObably the most inn portant forage fish in the lake, it was found at all stations apparently flooring shallow beaches with.a gradual slope, These fish were very prolific producing very large sohools during the summer months. Because they are so prolific and seldom grow to more than four inches in length, they might be useful for stocking as a forage fish in other lakes. Dorosoma oepedianum n Giszard Shad. Common at all stations but apparently not so prolific as in clear water lakes in the rest of the Stateo Only one specimen was taken that was ready to spawn, a male in April 1955. Young were taken in seines most commonly in January, February and March and in June, July and August which probably indicated a winter spawn.as well as one in the spring; Rene was taken at Station 7. Sex ratio, 87 males, 178 females, 117 not discerniblea Astyanax fasciatus m Tetraa 0f common occurrence throughout the lake but not in large numberso They seemed to prefer shallow gently sloping beaches. lotiobus bubalus m Snallmouth Buffalo. very common throughout the lake at all seasons, it ranked second in numbers and first in weight of all fish taken in one perimental notes Commereial fishermen took moderate numbers of them for sale as food and out baito Gill nets four feet deep with 7 or 8 inch stretched mesh were hung on tight top lines with no weights on the nettingo Spawning apparently occurm red from February through May and one ripe female was taken in November 1955; The larger sizes (12 to 25 pounds, sexually mature adults) were seldom taken during the job probably due to the use of mesh sizes that were too small for them (3" square nesho) Young were taken in seines in February, July and August mostly at Station 90 Table ll shows their relative abundance at the nine stations during each'month of the year. While they decreased in abundance in the winter at the open water stations of the main lake, they inoreased in abundance at the near shore and rive er stations during the winter. Sex ratio 385 males, 355 females, 189 not discernm ibleo Gyprinus fiaFEEE,“ Carp. Unoommon, only three were taken in experimental nettinga Conneroial fishermen sometimes took them and their reports indicated that previousM 1y, when the lake was olear, the carp was very comment Mro Ollie Cox, commercial fishermen on the lake for many years, believed that extensive netting of the adult carp while they were spawning caused tje practical eliminationo Considering the fecundity of the carp, it seems more probable that the continued siltation of the lake and the invasion of water hyacinths in many of the sloughs oaused their rem duetion in numbers by limiting the underwater plants on which the carp fed and spawnedt Rbtemigonugaorysoleuoas m Golden Shinero Rare, only 10 were taken in routine seining, all at Stations 2,h and 5 where bait released by fishermen could be expected.. ppsopoeodusaemiliae m Pugnose minnow. The third most common minnow in the lake, s ' 7 o it was found at a11 stations during all months of the year. Next to the threadfin shad, it was the most important forage fish in the lake for the smaller game fish. NotroEis_roseus m Central weed Shiner. Rare, only 11 specimens were taken in room tine coining, 10 of these were from Station 7, in the relatively clear water of Beldon Hollow. Notropis lutrensis w Red Shiner. Very common, especially at shaflow'beaches from January through July. During the spring spawning run in April or May large numbers were taken off Hog Island while seining for bait. Only two were taken at Station 7 perhaps due to difficulties in seining. Pimephales vigilax a Parrot Minnow. Taken in rather small numbers at all stations except 7, they were most numerous during the winter and early spring. ‘ ggtalurus punctatus m Channel Catfish. Commonly taken at all stations throughout the year. Table 19 shows that to percent of those checked had round worms‘in the viscera but adverse effects were not apparent. Stomach analyses of 35 stomachs 'show that while they ate almost anything, in the spring and winter they cropped heavily on Mayfly larvae. Many were taken by sportsmen, especially among the thick trees in Coffin Bay. Trotlines were usually stretched very tightly between trees so that the hooks baited with white laundry soap, cut buffalo, beef heart or livm or would just touch the top of the water. Often called willow cat by the fishermen the maximum size reported was about 8 pounds. Sex ratio 56 males, 105 females, 172 not discernible. lctalurus furcatus m Blue Catfish. Found in all parts of the lake at all seasons, this was the most important game fish in the lake. Largest taken in the job was 16 pounds but twenty and thirty pounders are frequently taken by fishermen and one over 60 pounds was reported. Table 12 shows their fnquency at the 9 nations durm ing the months of the year and Table 19 shows the percentage infested with visceral worms. Only 7 Shecimens wereiudunl that were ready to spawn or had just spawned, in may 1954. Sex ratio, 75 males, 320 females, 392 not discernible. m' '2‘! Station 8 and several were taken on a trotline in Beldon Hollow. Both bullheads were sometimes taken by fishermen around weed beds or log drifts. They seemed to prefer the clearer water of boys isolated behind water hyacinth mats from the rest of the lake and the impounded river channel. Ameiurus melee w Black Bullhead. Rare, only one was taken in routine netting at Ameiurus natalgg a fellow Bullhead. Uncommon, four were taken in experimental note, all at.station 7 and several were taken at the same place on a trotline. Some were taken by fishermen in the State Park Slough. Pilodictus clitoris m Flathead Catfish. Although commonly caught on trotlines fished deep with live bait, they were uncommon in netting collections. Seventy pounders were reported and one mania catch that weighed a total of #99 pounds was seen. He fished about 200 hooks baited with live Rio Grande perch for fee days near the Dam. Schilbeodes mollis m Tadpole Medtom. Not common but sometimes encountered during spring and summer while seining protected beaches with out books and some water hyacinths, they apparently hid in the roots of these plants. Three were taken from the stomach of a flathead catfish caught in Beldon Hollow. Anguilla rostrats m American Eel. Never taken during the job, several were rem ported caught from the lake by fishermen. Many youg from h to 8 inches long were found below the dam in the early summer of 1953. 8., Gambusia affinis u Gambusia. Very common at all stations, principally in the warm months. They stayed in very shallow water or aroundthickly matted water hyacinths. Mollienisia latipinna m Sailfin molly. Fairly common at all stations but in small numbers. They seemdd to prefer shallow beaches with a gently sloping silt bottom. Menidia berylippgmm Tidewater Silversides. Taken in large numbers at all stations, they were apparently most common from February to June. In spite of their availabil- ity, none was found in any stomach opened and no fish was caught while using them for bait on several crappie fishing trips. Micggpterus salmoides. Largemouth Black Bass. Not common in spite of the many fry and fingerlings stocked by the Game and Fish Commission prior to 1952. Larger fish were taken in nets at Stations 2, 3 and 7 and fingerlings were taken in seines in; February and May through August at Station 7. Crappie fishermen sometimes took bass around brush piles and Scir us beds. Reports indicated that during the years before the lake silted up badly iprior to l9h0) there was good base fishing,especially in the creeks and bays on the west side of the lake. During this job the water at Station 7 cleared sufficiently for plug fishing only at low water stages and on calm days. The excessive siltation of the lake had apparently reduced the spawning success of bass and sunfish to such a degree that good fishing pepulations could not maintained. Chaenobryttus coronarius w warmouth. Occurred in all parts of the lake throughout the year but in small numbers. lepomiibpyanellus _ Green Sunfish. Rare, only 9 were taken, all from Stations 8 and 9 from January through.March. They were much more common in the rivers feeding the lake. Lepomis microlophus w Redear Sunfish. Common but in rather small numbers, taken at all stations at all times except in May and April. Lepomis macrochirus m Bluegill. The most common sunfish in the lake but not numeru ons enough for good fishing. Taken at all stations throughout the year. .Most of the seined specimens were fry or fingerlings. may.“ Mr Lepomis megalotis - Longear Sunfish. Fairly common in small numbers, taken at all stations except o in all months except March and June. figmggig annularis m White Crappie. Very common, they were taken at all stations throughout the year. Greatest numbers were taken from February through June at Stations 2 and A. They were frequently infected with round worms as shown in Table 19. Reports indicated that during l9h9 and 1950 many were taken from therState Park docks but no one on the lake now sells minnows and very few fishermen try for crappie. Seveal brush piles of staked willow limbs were built in the fall of 195M to try to encourage crappie fishing. Although the fish responded, as shown by not sets around some of the brush piles, very few fishermen have made use of the artificial cover. These fish spawn from February through June. Sex ratio, 213 males, 379 females, 223 not discernible. Aplodinotus grunniens m Freshwater Drum. The most common fish taken in operimental nets, they were considered rough fish in this lake because of their large numbers and little desirability. Found at all stations at all times of the year, they occurred in least numbers in the clear water of Station 7. They spawn from March through July and netting collections during this period often consisted largely of males. Sex ratio , #76 males, 675 females, 275 not discernible. Many were infested with visceral round worms as shown in Table 19. 9. Cichlasoma cyanoguttata m Rio Grande Perch. Of common occurrence in rather small numbers throughout the lake. They were apparently most common in July, August and September-at Station 2, T and 9. Considerable numbers are brought in from the San Antonio River by fishermen and then released when the fishermen leave. Eleotris pisonis - Spinycheek Sleeper. One specimen was received from a fisherman who took it fishing with dead shrimp ”at the head of the lake.” Several specimens have been identified from below the dam. MWMHCIMEWEMMEE There were several invertebrate species in Lake Corpus Christi, some of which formed important food items for the fish. Probably the most important was-the .freshrater shrimp (Paleomonetes). very large numbers of these were taken in seining collections at all stations, especially during the summer months. Although of small size, they undoubtedly were an important food item for small fish. A few were found in the stomachs of seven species of fish. The large prawn, Macrobrachium acanthurus, occurred in the lake. Ninety of them were taken in a hoop net with lead seine which was set for three nights in the State Park Slough. One specimen of Macrobrachium carcinus was taken in a seining collection. These prawns, especially the young, probably were eaten by the catfish. The crawfish was very commonly found principally in water hyacinth roots. Blue catfish fed on them frequently but many fishermen rem ported that they could never catch any fish while baiting with crawfish on trotlines. The small oraufish were good bait for freshwater drum. Three species of large fresh water mussels were found in large numbers on silt batons in three to six feet of water. Channel catfish and blue catfish, especially the smalkr ones, often had their stomachs and intestines filled with the shells of small mussels. Although mayflies were seldom seen in large swarms, many Catfish stomachs contained nothing but the larvae of these insects. Dragonfly and damselfly larvae were common in the lake and were frequently eaten by catfish and crappie. AQDATIC VERTEBRATES .OTHER TEaN FISH Large flocks of ducks and geese winter on the lake, staying mostly in upper Coffin Bay. The parts of the lake in Live Oak and San Patrhio Counties fears a game refuge. Other common water birds, most common in the winter, were Mexican cormorants, anhingas, costs, great blue herons, American and snowy egrets, green here one, night herons, white and wood ibis, shite pelicans, sea gulls and terns. Turtles, although rather common, are seldom seen. Both the soft shell turtle (Amyda ferns) and the slider (Pseudemys scripts) were found. For frogs were found on the lake; the most common was the tree frog (H la cinerea) with some leopard frogs (Rana pipiens) and cricket frogs (Aerie crepitans.§ No bullfrogs were seen or heard. The shore frog numbers are probably.kept in check by the large numbers of raccoons that occur around the lake. Some alligators (Alligator mississippiensis) occur in the lake and a large one was caught by the foot on a trotline just below Lagarto Bridge. PARASITES Only four kinds of parasites were noticed on the fish of Lake Corpus Christi: fish lice (Argulus), a small brown leech, visceral round worms and tape norms. The fish lice were noticed on almost all the large alligator gars examined, usually around the head and gill covers. The leeches were found on gore and blue catfish, usually attached beneath the mouth of the fish. Tape worms were often found pustules in the connective tissues of the body cavity.- Table 19 shows the percentages of infection and the ”K" factors of the four species of fish Which most commonly had these worms. The worms not only did no apparent harm to the fish but, according to the data, the “K” factor of the infected fish was greater than those not infected. 100 The redear sunfish was also quite often infected with these worms. RECOMMENDATIONS The lake is in very bad condition from most aspects. Its primary use as a water reservoir for Corpus Christi has been reduced to a dangerous minimum by silm tation. It now contains onlyzbout 30,000 acre feet of water, about onewhalf its original capacity when it was built in 193%. This siltation is due primarily to the large watershed area as compared to the small size of the lake. From available re: ports of fishermen, the lake formerly provided good fishing for both black bass and catfish. It is non principally a rough fish lake with many gars ,. smallmouth bufm falo , catfish, crappie and freshwater drum. water hyacinths have covered many of the bays that were the best fishing areas. Conditions are such that the onlyf way to appreciably increase the game fish population is to build a larger dam to flood this old lake. Plans are now under way by the Lower Nueces River water Supply District to build a new dam just below the old one which will raise the water level to 9h feet above mean sea level, 20 feet above the old lake. Such a lake shouh contain clear water for a good many years and provide ecologicalhsuitable water for game fish. A project is now in progress to kill the water hyacinths, and it is hoped that in this may, they will not infest the new lake. When the new dam is comm plated, it will probably be practical to repeat this study to investigate the changes in fish populations brought about by the flooding of the old lake. SUMMARY The fish populations of Lake Corpus Christi were investigated by netting and seining monthly at nine stations for the period July 1, l953_through June 3), 1955. A description of the stations and the methods used is given and the kinds and numbers of fish taken are discussed. The seasonal changes in numbers and percentages of the varies species is analysed and shown in tables. Short notations of each spew cies are given and the common invertebrates, vertebrates and parasites are consideru ed. Stomach analysis, sizes and coefficient of condition are shown in table form.