TPWD 1956 F-4-R-3 #246: Inventory of Species Present in Benbrook Lake, Texas

--- Page 1 --- LOWMAN JOB COMPLETION REPROT 3 STATE l LE ae ia rroject No. F4R3 Name Fisheries Investigations and Surveys of the Waters of Region 4-B, Job No. B-5 Title Inventory of Species Present in Benbrook Lake, Texas. Period Covered: June 1953 - October 1956 ABSTRACT 1. Benbrook Lake is located about 15 miles southwest of Fort Worth, Texas in Tarrant County. The dam was completed in September 1952. 2. The lake will impound 3,769 surface acres of water at top of conservation pool level, but has filled to only one-third of that capacity to date. 3- The fish population was sampled with gill nets each month during the three and one-third year period. 4. The population of fish has changed from predominately game fish to predomin- ately rough fish during the past three and one-third years of study. 5. Largemouth bass have decreased from a former 84.77 percent to the present 3.80 percent of the total fish population. 6. The white crappie has increased from a former 0.27 percent ot the present 21. °9 percent of the total fish population. {- Benbrook Lake was closed to fishing from September 1953 to June 1954. Bs Largemouth bass suffered from overcrowding during the period that the lake was closed to fishing resulting in extensive parasitism, loss of weight, predation upon like species, and reabsorption of eggs. 9. Largemouth bass grew much faster after the lake was opened to fishing. 10. Mainutrition, parasitism, and the reabsorption of eggs was not present after the crowded game fish condition was alleviated. ll. A rapid change in fish population, either in types or numbers, may upsét the lake balance causing it to fluctuate from one extreme to another. 12. Benbrook Lake was offering fairly productive bass and crappie fishing at the close of the present study. 13. Fishing should be more productive. when the lake catches enough water to inundate the remaining two-thirds of the proposed lake area. OBJECTIVES To determine the species present and their relative abundance as well as the --ological factors influencing their distribution. --- Page 2 --- INTRODUCTION This paper reports on the work done during the third segment of a three-segment survey and summarizes the results of data collected during the entire three and one- third years of study. The project had as its primary aim the accumulation of data which would show the progression of a new lake during the first few years of its existence. Emphasis was given to the study of changes in the fish population and the problems ass- ociated with such changes. HISTORY OF LAKE Benbrook Lake is located in Tarrant County about 15 miles southwest of Fort Worth, Texas. Closure of the dam was made September 29, 1952. The lake will impound 3,769 surface acres of water at top of conservation pool level. A severe drought allowed the impoundment to catch only enough water to fill to about one-third of its normal capacity. The lake is usually clear but sometimes stirred by winds until it is slightly dingy. The lake was stocked with 550,000 fish in 1953 of which 370,000 were largemouth bass. Table 1 lists all fish that have been stocked in Benbrook Lake by State and Federal Hat- cheries. The impoundment was closed to fishing in September 1953 and remained closed until June 1, 1954. Fishing pressure was extremely heavy the first few days of the open season but not so intensive thereafter. COLLECTING METHODS The fish population was sampled each monthwith gill nets during the three and one-third years os study which began in June 1953 and ended in October 1956. The nets were 100 or 125 feet long, eight feet deep, and had meshes of 1 to 3 inches square measure’ The bulk of the sampling was donc with nets having meshes 14 inches in size. Periodic checks were also made with minnow seines of various types and sizes. The seined samples were preserved in 6 percent formalin and taken to the laboratory for identification. The fish collected by gill nets were worked to obtain their length, weight, gonadal develop- ment, and stomach content. A checklist of fish collected from Benbrook Lake is recorded in Table 2. DISCUSSION Consideration will be given to each major species of fish and the changes that took place in the population of those species throughout the period of study. The effect of the changes in the composition of the fish population on the lake as a whole will be discussed. Table 3 shows the results of the seine collections made during the third seg- ment of the survey. Heavy stocking of the lake with fry prevented the data taken at the seine stations from being too indicative of the success of the local spawns. Table is a tabulation of data taxen from the gill net collections during the third segment of the survey. Table 5 records the frequency of occurrence of fooditems observed in the stomachs of the netted specimens. LARGEMOUTH BASS Largemouth bass were caught in large numbers in each net that was set in the lake from August 1953 through May 1954. The lake had been heavily stocked with bass in 1953 and was closed to fishing in September of that year. The bass averaged 94 ounces in weight when the netting was begun in August. The fish gained nearly 14 ounces per month for the next two months. Then their growth slowed down and they even lost some wei, until they averaged only 11 1/3 ounces in May 1954 just before the lake was reopened to fishing. The effect of severely crowded conditions, accompanied by heavy infestations of parasites and a shortage of food, resulted in poor health of the bass. --- Page 3 --- 3. Once a hundred foot gill net with 14-inch mesh was checked after being set out “or only 45 minutes. The net contained 45 bass. The incident points out how crowded the fish were and shows the vast amount of movement that took place as the starving fish fought among themselves for the small amount of natural food available in the lake. Bass ate bass and anything else in the lake that they could swallow. An artifical lure moved through the water attracted dozens of small bass and they would fight over the lure until the hooked fish was removed from the lake. Effects of the overcrowded condition were many. All bass were heavily parasitized. Some died from one cause or another, perhaps many of them starved to death. The mature fish reabsorbed their eggs and if there were any successful spawns there was no indication that any of them escaped the hungry and emaciated adults. Many thousands of bass were caught June 1, 1954 when the lake was opened to fishing. A fair harvest, but in rapidly decreasing numbers, was made during the next few days. Then bass fishing was very poor for a long time. Our gill nets caught only 18 bass from June through September after the lake was opened to fishing, as compared to dozens and sometimes hundreds of bass that were taken in each net that was set in the lake when the bass population was so highly overcrowded. Larger catches of bass were made in the nets during the lake fall months but never in numbers that would compare with the previous large catches. However, the bass were growing and were showing the effects of an avail- able food supply. By December 1954 fat bass weighing 2 and 3 pounds were caught. The bass population had begun to revive. Although not present in numbers as great as in the previous year, the health and general condition of the bass was excellent. The bass population remained fairly good throughout the rest of the study. It apparently dropped some in numbers during the last segments survey but gained in average weight and coeff- iciency of condition of individual fish. Table 6 shows the average catch per net set and average weight and "K" factor of bass captured during each segment of the survey. WHITE CRAPPIE White crappie are the only species of crappie that have been taken from Ben- brook Lake, although: it was stocked with about two to one in favor of the black crappie in 1953. In August and September of 1953 five crappie were caught in gill nets. They were thought to be specimens that were in the river system prior to formation of the lake. There were no more caught for one year then a few, mostly small ones, were captured each month from October 1954 to August 1955. In September of that year the first good catch of crappie was taken with gill nets. A large harvest of 6 to 8 ounce size crappie was made in November and good catches were netted rather consistently each month thereafter. Reports from fishermen of their hook and line harvest indicated that their first good catches of crappie coinsided very closely with our first favorable net catches. It will be noted that it took the crappie from a4 to 3 years to build up a population that showed up favorably in either our net catches or the fishermen's harvest. We do not know what effect the stocking of crappie had on the lake with the exception that the black crappie did not survive. It is possible that the present population of crappie were spawned from the few specimens that were in the drainage system when the lake was impounded. One reason for the rather slow increase in the number of crappie may be attributed to the small amount of water and the very few specimens of crappie that were present when the dam was constructed. The progression of the crappie population is shown in the lower part of “igure 1. It may be of interest to note that the average "K" factor of white crappie creased as the number of fish in the lake increased. The converse is true of the large- mouth bass which showed an increase in the average "K" factor as the population of that species decreased. The crappie population was good at the end of the survey (October 1956) and will probably offer productive fishing for the next several years. --- Page 4 --- CHANNEL CATFISH The channel cat population has not fluctuated too severely in the lake. It is true that the best net catches of channel cat were made during the first segment of the survey when 32 channel cat were captured with an average weight of 2.73 pounds per fish. Evidently many or all of them were fish that were in the pot holes of the river when water was impounded in the lake. Evidently, their growth was quite rapid due to the expansion of the lake which offered very fertile feeding grounds and new food supplies. The bulk of the catches of channel cat during the last two periods of the survey consisted of smaller fish. Reference is again given to Table 6 which shows that the number of fish per hundred feet of net dropped considerably during the second segment but began to increase during the last survey period. The increase in numbers and decrease in average size indicates that spawning has been successful. Spawning facilities are good and as forage fish are abundant the channel cat population should continue to be pretty good in the lake. There are no yellow cats (flatheads) in the lake. BLACK AND YELLOW BULLHEAD CATFISH The bullhead population has been relatively high during the entire period of study. The impoundment has a number of creeks entering it from the drainage area and a consid- erable amount of shallow brushy areas that are conducive to good bullhead production. Both black and yellow bullheads are present but the yellow bullhead is rapidly disappear- ing from the lake and should soon become extinct. The black bullhead may also be dec- reasing in numbers but evidence of such is much less conclusive than the decrease in- dicated for the yellow species. It is uncommon for the bullhead species to remain in large numbers very long after a lake has been formed in this area. It is possible that the absence of a yellow cat population, which is normally found in most of our lakes a is often given credit for preying on bullheads, is the reason that the bullhead population has been able to sustain itself in Benbrook Lake. Bullheads are found quite often in the fishermens' creel, especially those of young children and colored people. SPOTTED SUCKER The rapid expansion of the population of spotted suckers in Benbrook Lake has been an interesting development. The species has not been found in any of the other local lakes, although none are on the same drainage as Benbrook, therefore it should probably be considered as indemic to the Clear Fork of the Trinity River. The first spotted sucker netted was an adult specimen caught October 13, 1953. Several additional fish wre captured during the following January, March, and April. Each weighed about one pound and those taken during March and April were ready to spawn. Young suckers averaging 5 to 6 ounces in weight were caught during October and November of 1954. Other mature fish were collected during the spring of 1955 and many that weighed almost a pound each were taken in late fall of 1955. The catch of spotted suckers was high during the remainder of the netting study. Gonadal development indicates that the fish spawn in April and May and netting catches show that the young weigh 5 to 7 ounces by the end of that year. These fish seem to be capable of spawning when they are two years old and have attained a weight of about a pound. The largest sucker captured from the lake weighed 1 pound and 12 ounces. The expansion of the sucker population has been very rapid. The few specimens that originally populated the Clear Fork of the Trinity three years ago developed into one of the major species of Benbrook Lake. Figure 2 shows the incre ~e in the spotted sucker populationas indicated by the percentage of the total net catch that the species represented. COMPARISON OF THE GAME FISH AND ROUGH FISH POPULATION --- Page 5 --- Be Table 7 records the data regarding the game fish and rough fish populations and shows the changes in the composition of the population during the three segment survey. Figure 3 shows the percentage, by number and weight, of the total net catch represented by game species. STOCKING Benbrook Lake has been heavily stocked with game fish. There were 1,654,295 largemouth black bass fingerlings or fry stocked in the lake between 1953 and 1956, both years inclusive. This averages more than 1500 bass per surface acre. Bass fishing has been fairly good at times and very poor at other times on the lake. There were also 23,650 black crappie reportedly stocked in the lake during 1953. A17 month creel census and a 3 i/3 year netting survey failed to produce any specimens of that species. Evid- ently the lake is not suitable for the production of black crappie and additional stock- ing of that species would be futile. POLLUTION AND FISH KILLS There are no known sources of serious pollution affecting Benbrook Lake. No doubt there has been some siltation but so far it has not been serious. There are no cities or factories emptying their effluent into the drainage system. But there have been a few fish kills on the lake. Several small kills occurred during the summer in isolated water holes far up the Clear Fork of the Trinity River. Chemical analysis of such areas, taken early in the morning, revealed a very low oxygen content. Lack of oxygen during the latter part of the night probably caused the fish to suffocate. Almost every year, during early spring, fish die on the main body of the lake from apparently unknown causes. Usually the kill is not serious but during the spring of 1956 a large number of mature bass died. A few specimens of other species were aff- ected but the bulk of the fish that died were two to four pound bass. The cause is not known but there seems to be certain conditions that can be correlated between Benbrook kills and similiar incidents that have happened on other lakes. These conditions will be watched closely during the coming spring. FUTURE OF LAKE Benbrook Lake has two major factors in its favor for good fisheries production during the next few years. The first and probably most important item is the large area of land that has not yet been inundated. There still remains about two-thirds of the normal lake that will be flooded for the first time when the impoundment fills. A great deal of the new area is composed of fertile flatlands that shoulda add considerable to the pro- ductivity of the.lake. The second factor in favor of good fishing in the near future is the large numbers of local anglers available for fishing the lake. It seems that a fair- ly heavy fishing pressure is preferred for most lakes. On the other hand, there are a few factors present that could be detrimental to the success of the future fishing on the lake. Number one is the rapidly increasing rough fish population, composed primarily of spotted sucker, that may affected the game fish production. Number two is the insistence of various local citizenry on heavy stocking, restricting of harvest or in other ways interfering with the normal development and harvest of the game species. RECOMMENDATIONS It is recommended that the monthly netting of Benbrook Lake be discontinued bit that some provision be provided for an occasional check on the lake in order to obtain data regarding any future major changes in the fish population. --- Page 6 --- It is further recommended that some consideration be given to methods of contrc or harvest of the rapidly expanding spotted sucker population. \ Prepared by Robert N. Hambric Approved by ded Go be_ Assistant Project Leader Chief Aquatic Biologist Date April 10, 1957 --- Page 7 --- Table 1. Hatchery Stocking of Fish in Benbrook Lake, Texas, May 1953 through October 1956. Species 1953 1954 1955 1956 Total Largemouth black bass 370,325 109,000 34,970 1,140,000 1,654,295 Redear sunfish 50, 525 12,660 53,333 116,518 Bluegill sunfish 22,325 12,660 Dapoo0 88, 318 Yellowbelly sunfish 12,660 53,333 65,993 Total 4h3 175 109,000 72,950 1,299,999 1,925,124 --- Page 8 --- 8. Table 2. Checklist of Fish Species from Benbrook Lake, Texas, 1953 - 56. Common Name Scientific Name Gizzard shad River carpsucker Grey redhorse Spotted sucker Carp Suckermouth minnow Redfin shiner Brazos river shiner Blacktail shiner (Spottail) Red shiner (Redhorse) Silvery minnow Plains minnow Parrot minnow Fathead minnow Stoneroller Southern channel catfish Black bullhead Yellow bullhead Tadpole madtom Blackstripe topminnow Gambusia Kentucky spotted bass Largemouth black bass Warmouth Green sunfish Small sunfish Redear sunfish Bluegill sunfish Orangespotted sunfish Yellowbelly sunfish White crappie Dusky darter Logperclt -_—_—_——— Dorosoma cepedianum Carpiodes carpio Moxostoma congestum Minytrema melanops Cyprinus carpio Phenacobius mirabilis Notropis umbratilis { Notropis brazosensis Notropis venustus Notropis lutrensis Hybognathus nuchalis Hybognathus placita Pimephales vigilax Pimephales promelas Campos toma anomalum Ictalurus punctatus Ictalurus melas Ictalurus natalis Schilbeodes mollis Fundulus notatus Gambusia affinis Micropterus punctulatus Micropterus salmoides Chaenobryttus gulosus Lepomis cyanellus Lepomis symmetricus Lepomis microlophus Lepomis macrochirus Lepomis humilis Lepomis auritus Pomoxis annularis Hadropterus scierus Percina caprodes --- Page 9 --- 9. Table 3. Results of Seining Collections by Number of Each Species, Benbrook Lake, Texas, 1955 - 56. ea Species Number Collected Percent of Total rrr in Gizzard shad 174 18.41 Redfin shiner 53 5.61 Brazos river shiner 26 2 TS Blacktail shiner (spottail) ko Me Yd Red shiner (Redhorse) 390 41.27 Plains minnow 3 0.32 Parrot minnow 63 6.67 Yellow bullhead 1 0.11 Blackstripe topminnow 3 0.32 Gambusia 83 8.78 Largemouth black bass 20.: 2.12 Green sunfish 13 Le37 Bluegill sunfish’ 66 6.98 Orangespotted sunfish 5 0.53 Yellowbelly sunfish 1 O..41. Logperch 2 0.21 ee a eee eae Total Oh5 100.00 then etre enn tenets pte uanndneivennrsttnennsenencemnanner --- Page 10 --- Table 4. Tabulation of Data from Net Collections from Benbrook Lake, November 1955 through October 1956. ett cern seennwenetnecenne erent Species Number Percent of Pounds Percent of Average Wt. No. of Fish Lbs. Fish Caught Total No. Caught Total Weight in Pounds Per 100' Net Per 100' Net EE ee OUST AN Ser ee Ne Shad 153 11.75 27.66 3.35 0.20 3.31 0.66 Carpsucker 3 0.25 8.81 1.07 2.94 0.07 0.21 Spotted sucker 609 51.48 555.92 67.30 0.91 14.50 13.24 Carp 15 1.27 T43 0.90 0.50 0.36 0.18 Channel cat 29 2.45 27 Uh 3.32 0.95 0.69 0.65 Black bullhead 59 4.99 17.28 2.09 0.29 1.40 0.41 Yellow bullhead 9 0.76 3.80 0.46 O.4e 0.21 0.09 Largemouth bass 45 3.80 74 ue 9.01 1.65 1.07 1.77 Bluegill sunfish 22 1.86 3.46 0.42 0.15 0.52 0.08 White crappie 253 21.39 99.79 12.08 0.39 6.02 2.38 Total 1183 100 .00 826.01 100.00 28.15 19.67 --- Page 11 --- il. Table 5. Frequency of Occurrence of Food Items from Fish Collected by Gill Nets, Benbrook Lake, Texas, November 1955 through October 1956. eee Species Shad Unidentifiable Insects Algae and Number of Fish Fish Remains Vegetation Examined ee Largemouth black bass 3 6 0 0 hs White crappie 8 126 2 1 251 Southern channel catfish 3 5 2 9 29 Black bullhead fe) 2 1 14 59 Yellow bullhead O O 6) 1 9 Bluegill sunfish eo) O 0 3 el --- Page 12 --- le. Table 6. Comparison of Fish Caught Per 100 Feet of Gill Net and Their Average Weight and "K" Factor, Benbrook Lake, Texas, 1954-1956. Species No. of Fish Avg. Weight Average "K" Per 100' Net Pounds Factor Bass 1954 63.03 0.73 2.56 1955 1.96 1.58 2.65 1956 1.07 1.68 2.72 White Crappie 1954 0.02 0.55 3.07 1955 1.02 0.57 2.86 1956 6.02 0.39 2.76 Channel Catfish 1954 1.10 2.73 LTT 1955 0.31 1.92 1.74 1956 0.69 0.95 1.74 Yellow Bullhead 1954 2.52 0.88 2.81 1955 0.66 Osk7 2.32 1956 0.21 0.42 2.32 Black Bullhead 1954. 2.31 0.80 2.27 1955 1.14 0.39 2.36 1956 1.40 0.29 2.49 --- Page 13 --- 13. Table 7. A Comparison of the Changes in the Game Fish and Rough Fish Populations of Benbrook Lake, Texas, 1953-1956. RnR en eee Aug. 1953 June 1954 4% Change June 1955 % Change from Percentage Chg. through through from First through Previous between First May 1954 Oct. 1955 Segment October 1956 Segment and last Segment Avg. Wt. Per Specimen for all Fish Netted 0.75 0.88 17.33 0.70 ~20.45 -6.67 Avg. Wt. Per Game Fish 0.75 1.15 53.33 0.59 -48.70 ~21.33 Ave. Wt. Per Rough Fish 0.80 0.67 -16.25 0.74 10.45 ~7.50 Percent Game Fish by No. 89.07 32.62 -63.38 29.50 9.56 -66.88 Percent Rough Fish by No. 10.93 67.38 516.47 70.50 4.63 545.01 Percent Game Fish by Wt. 88.32 45.39 -48.61 ah 82 -45.32 -71.90 Percent Rough Fish by Wt. 11.69 54.61 367.15 75.18 37.67 543.12 --- Page 14 --- BASS M L CRAPPIE Ww 1954 1955 1956 1954 1955 FIGURE | YEARLY POPULATION TREND AND CC RESPONDING AVERAGE "K" FACTORS OF TWO SPECIES, BENBROOK LAKE 1954-1956 PERCENT OF TOTAL NET CATCH AVERAGE "K" O 10 20 30 40 90 60 3.0 2 : 2 & g 8 FACTOR a) 2.0 --- Page 15 --- FIGURE 2 INCREASE IN THE SPOTTED SUCKER POPULATION, BENBROOK LAKE 1954-1956 PERCENT OF TOTAL NET CATCH O 10 20 30 40 30 60 TO 80 90 100 1954 1955 1956 --- Page 16 --- FIGURE 3 BENBROOK LAKE DECREASE IN THE GAME FISH POPULATION 1956 55 9 1954 BY NUMBER T PERCEN PERCENT BY WEIGHT Oo o oO oO Ww) vT HOLVO LAN W101 JO LN3OY3d < 10