TPWD 1958 F-6-R-5 #363: Report of Fisheries Investigations: Basic Survey and Inventory of Fish Species Present in Fort Brown Lake

--- Page 1 --- Report of Fisheries Investigations Basic Survey and Inventory of Fish Species Present in Fort Brown Lake by L. V. Guerra Assistant Project Leader Dingell-Johnson Project F-6-R-5, Job B-8 July 1, 1957 - August 31, 1957 H. D. Dodgen, Executive Secretary Texas Game and Fish Commission Austin, Texas Marion Toole William H. Brown Coordinator Asst. Coordinator --- Page 2 --- JOB COMPLETION REPORT State of TEXAS Project No. FOR5 Name: Fisheries Investigations and Surveys of the Waters of Region 8-B. Job No. B-8 Title: Basic Survey and Inventory of Fish Species Present in Fort Brown Lake. — Period Covered: July 1, 1957 - August 31, 1957 ABSTRACT: 1. The fish populations of Fort Brown Lake, near Brownsville were investigated for a period of two months. Eight netting and two seining collections were made. 2. .Chemical analysis was conducted and the lake was found to have adequate but not optimum conditions for fish propagation. 3. <A physical description of the area is given including the physiography, soil types and geology. 4. The results of the netting and seining collections are discussed and pre- sented in table form. 5. Stomach analysis, coeffecient of condition, ranks by weight and number are presented in table form. 6. Fort Brown Lake is a long, murky, winding, shallow, silty bottomed, ox~-bow type lake that has long ceased to have any natural connection to the Rio Grande or other waters. Rough fish predominate and the populations are so high that the only recourse open for a sound fisheries program is a complete kill and subsequent re-stocking. Ade- quate fish screens should first be placed at the pump discharge to prevent re-introduction of undesirable fish from the Rio Grande. OBJECTIVES ; To determine the chemical and physical characteristics of the lake and the fish species present. PROCEDURE: During the course of the survey ten collections were made consisting of two seining collections and eight netting collections. Gill net collections were made with experimental nets 125 feet long and eight feet wide. The mesh ranged from one to three inches square, graduating one-half inch every twenty-five feet. The nets were set at the designated locations in July and August (Map 1.). Seining collections were unorthod-~, --- Page 3 --- as the sharp, cliff-like banks made regular seining impossible. Collections were made y "flipping" the net out from the bank and then lifting up. Water analysis tests made in the field consisted of air temperature, water temperature, pH, dissolved oxygen, carbon dioxide, ph-th alkalinity, methyl orange alka- linity, and salinity. Jackson turbidimeter readings were done in the laboratory from a well shaken water sample. Surface water samples were collected at the center of the lake to represent the apparent single ecological condition. : PHYSICAL CHARACTERISTICS AND DESCRIPTION: Fort Brown Lake is located two miles east of the city of Brownsville and like many in this area was at one time part of the "resaca system" that has long been isolated from the river and no longer has a natural connection with the Rio Grande. A twelve-inch pump is connected to the Rio Grande to bring in water to the lake at times of excess water in the river and thus prevent its entry and loss into the Gulf of Mexico. This lake is owned and operated by the City of Brownsville, and is used to furnish recreational facilities to the people of the area. Fort Brown Lake has a surface area of 32.68 acres, with a total volume of 168.78 acre feet. The deepest part of the lake is seven feet but the average is slightly over five feet. The lake is long and narrow, curving around Southmost College on the north- west and private homes on the east. The bottom, for the most part, is silt with some areas of sandy silt that support some stands or emergent vegetation in the form of willows, other vegetation is relatively absent. Fort Brown Lake is in the Gulf Coastal Plain physiographic region and is a seg- ent of the great coastal plain across the southern states and crosses the Rio Grande into Mexico, gradually narrowing as it swings through Texas and southward. The lake is more precisely located in the Coastal Prairie sub-region of the Gulf Coast Plain. Geologically the lake is located in the coastal syncline of the Rio Grande Embayment. In this area the substructures dip generally to the southeast. The surface structures of the whole Coastal Plain in this area are of the quaternary geologic period. The soil types found in this area are characteristic of the Rio Grande Plain soil belt that occupies the southern part of Texas. ‘The area is generally broad, very gently undulating to rolling plain with a gradual slope to the southeast. Soils are generally clay with occassional intrusions of marsh type soils which are high in saline content. DRAINAGE AREA:. The water supply for this lake is direct from the Rio Grande by means of a twelve- inch centrifugal pump. At times of excess water in the river, water is pumped into the lake to prevent its loss into the Gulf of Mexico. This is one of the lakes in the whole valley that has possibilities for a fisheries management program, because of its regulated water inlet and supply that can be screened. Because of the high banks of the lake there is no run-off water, but water can be drained from the lake by means of pumps at the south- east end. AQUATIC VEGETATION: Except for a few stands of willows along the east end of the lake and some deep rooted Bermuda grasses along the edges the lake does not have much in the nature of --- Page 4 --- vegetation, either of a beneficial or detrimental nature. The high turbidity found in this lake is probably due to bottom feeding rough fish that prevent the establishment and growth of subsurface vegetation. CHEMICAL ANALYSIS: The results of the chemical analysis from a central location (Map. 1) in Fort Brown Lake are shown in Table 1. Samples were taken from the surface as the lake depth averages only five feet. The table shows the readings for the months of July and Aug- ust and the general average for the two-month study period. There are not any definite conclusions that can be formed from the short period of tests on water, however, sign-~ ificant results of the high saline contents of the water are clearly shown. In all prob- abilities this is a direct result of the high saline content of the ground underlying the lake and this salinity is significant because it is over 600 p.p.m. over that of nearby lakes and the average is over 400 p.p.m. of the Rio Grande water during flood stages. RESULTS OF FISH COLLECTIONS : Seining Collections Two seining collections were made in Fort Brown Lake during the project period. Collections show a large number of bass fingerlings, and juveniles, with some small year- lings. Analysis of the seining collections can not be considered because the seining method used was the only one possible and does not establish a fair criteria for analysis of the small fish present in the lake as may be seen on Table 3. Stocking records for this lake show that 10,000 bass fry were stocked on March 3, 1955, 15,000 on March 30, 1956, and 10,000 on March 4, 1957. Also 7,000 catfish fry were stocked on November 1, 1956. Seining collections show a large percentage of game fish, this may be accounted for by the recent heavy stockings, that the non-game fish have not had a chance to crop off because of the abundance of other forage fish such as shad and topwater minnows. Fishing pressure on this lake is small but evident, as water skiers using this lake prevent any still shore fishing and make other methods impos- sible. Seining collections and their relative abundance may be seen on Table 2. Netting Collections During the survey four netting stations were selected. These represent essen- tially the same ecological conditions but were so selected to insure accurate results over the two-month study period. The netting results are tabulated on Table 3. Rough fish comprise 98.16 percent of the total number and 95.53 percent by weight of the fish caught in experimental nets. Freshwater drum have not been considered in this report as a game fish because of their undesirability by the fishermen of the area. The present fish population of Fort Brown Lake is typical of the old ox-bow lakes of this area, often flooded by "resaca" run-off water. Although isolated from all sources of water except the Rio Grande the lake still shows a typical "resaca" liminological conditions and aquatic environments. A check list of the fish found in Fort Brown Lake is shown on Table 4 and their relative abundance is noted. Pounds and numbers of game and rough fish as well as per- centages, ranks by weight, and numbers have been combined into one master table.(Table 3) --- Page 5 --- success of experimental gill netting table has not been included in this report oecause of the small number of collections. Table 5 shows the ranks, lengths, weight and "K" factors of fish caught. A table of sexual condition is not shown because the short period of time would not indicate any trends at this time of the year. STOMACH ANALYSIS: Stomach analysis were conducted on all fish that had food in their stomachs. The reason was two fold, one to see if the fish contained other foods besides fish and to see if the rough fish of the lake were cropping off what few game fish were present. (Table 6). Fifteen stomachs contained either game or forage fish. One cat- fish contained one bass fingerling, while the rest contained shad and top water minnows. RECOMMENDATIONS : 1. Because of the heavy rough fish populations, a complete kill of the fish populations and subsequent re-stocking with game fish is recommended. 2. Repeated stocking with game fish principally bass and catfish should be discontinued until such time the city of Brownsville, that has shown an earnest desire to improve this lake constructs a fish screen to prevent rough fish entry into the lake when filled by pumping from the Rio Grande which is heavily populated with rough fish. 3. Brownsville City Manager E. W. Watts is to be commended for his efforts to improve this lake to provide fishing facilities for many winter visitors in the area and has shown a willingness for the city to do the rough fish clean up when the complete jill takes place. t Liz Ot aete Prepared by L. V. Guerra Approved by AO /CAAp tore Assistant Project Leader Chief Aquatic Biologist Date October 18, 1957 --- Page 6 --- Table 1. Chemical Analysis of Fort Brown Lake, Brownsville, Texas. Date Oxygen Carbon ph-th M. O. pH Salinity Turbidity Degrees Dioxide Alkalinity Alkalinity p-p-m. Fahr. July 9.4 2.2 _ 0 158 Jo2 1346 160 87 August 9.4 2.6 0 160 8.8 880 165 85 Average 9.4 2.4 © 159 9.0 1113 163 86 --- Page 7 --- Table 2. Seining Collections, Fort Brown Lake, Brownsville, Texas, July through August 1957. Species Total Number Relative Abundance D. cepedianum ho Abundant A. fasciatus m. 2 Rare I. bubalus ~ 3 Rare C. varigatus v. 18 Moderate G. affinis a. 36 Abundant M. latipinna 2 Rare M. beryllina 18 Moderate M. salmoides 25 Abundant L. cyanellus 6 Few a. cyanoguttatum 12 Moderate pee @) ct ny - n --- Page 8 --- Table 3. Fish Caught in Experimental Gill Nets from Fort Brown Lake, July through August 1957. Four Experimental Gill Nets Per Month, A Total of 8 Net Sets. Species Total % by Weight Weight % by Number Number in Grams in Pounds Weight Spotted gar 5 1.82 5274 11 lbs. 10 oz. 5.60 Gizzard shad 47 17.10 5180 ll lbs. T7oz. 5.55 Smallmouth buffalo 93 34.20 19084. 42 lbs. 102. 20.55 Carp 23 8.20 20563 45 lbs. 5 oz. 21.85 Blue catfish 4 1.37 3700 8lbs. 2 oz. 3.90 Flathead catfish 43 15.70 20989 46 lbs. 4 oz. 22.43 Largemouth bass 1 0.35 4.82 llb. loz. 0.48 Freshwater drum 58 21.14 13699 4O lbs. 3 0z. 19.53 Game Fish 5 1.72 4182 9 lbs. 3 oz. 4.38 Rough Fish 269 98.16 84.789 196 lbs. 14 oz. 95.53 Totals 27h 88971 206 lbs. loz. 99.91 Ranks by Number Rank by Weight 1. Smallmouth buffalo 1. Flathead catfish 2. Freshwater drum 2. Carp 3. Gizzard shad 3. Smallmouth buffalo 4, Flathead Catfish 4, Freshwater drum 5. Carp 5. Spotted gar 6. Spotted gar 6. Gizzard shad 7. Blue catfish 7. Blue catfish 8. Largemouth bass 8. Largemouth bass --- Page 9 --- Table 4. Check List of Fish Species Recorded from Fort Brown Lake, Brownsville, Texas. Scientific Name Lepisosteus productus Dorosoma cepedianum Astyanax fasciatus m. Ictiobus bubalus Cyprinus carpio Ictalurus furcatus Pylodictus olivaris Cyprinodon varigatus Gambusia affinis Molliensia latipinna Menidia beryllina Micropterus salmoides Lepomis cynellus Aplodinotus grunniens Cichlasoma cynoguttatum 8. Common Name spotted gar gizzard shad banded Tetra smallmouth buffalo carp blue catfish flathead catfish Sea pupfish Gambusia sailfin molly silversides largemouth bass green sunfish freshwater drum Rio Grande perch Abundance few abundant few abundant abundant rare abundant common. abundant rare common rare few abundant common --- Page 10 --- 9. Table 5. Ranks, Lengths, Weights, and "K" Factors of Fish Caught in Experimental Nets from Fort Brown Lake, Brownsville, Texas, July through August 1957. Species Rank By Standard Length in mm. Weight in Grams "K" Factor No. Wt. Min. Max. Ave. Min. Max. Ave. Min. Max. Ave. L. productus 6 5 479 632 540 369 1706 908 0.68 0.69 0.68 D. cepedianun 3 6 133 160 146 52 269 146 1.46 1.85 1.53 I. bubalus i 3 126 274 236 60 1134 436 0.72 3.30 3.02 C. carpio 5 2 119 435 369 59 1814 1203 2.08 3.30 2.48 I. furcatus 7 T 202 536 362 128 2438 1ohkk 1.30 1.58 1.46 P. olivaris 4 1 185 KT 315 100 1162 527 1.37 1.60 1.48 M. salmoides 6 8 285 482 2.07 A. grunniens 2 4 132 408 239 61 1701 596 2.20 2.63 2.54 --- Page 11 --- 10. Table 6. Stomach Analysis Showing Number of Stomachs Containing Various Food Items. Species No. of Stomachs Total Volume Crayfish Game Fish Forage With Food in cc. Fish L. productus 3 262 ¢) ©) 3c P. olivaris 8 95 2 0 6° I. furcatus 1 9 0 1° 0 M. salmoides dL. 18 1 O ie) A. grunniens T 80 2 0 5° a: Bass fingerling bs Shad and Gambusia ec: Silversides --- Page 12 --- GoAT RAMP EASE FORT BRCWN LACE, BROWNSVILLE, TEXAS @: NEPTING starrons a] CHEMICAL STATION store | SEINING BACH