TPWD 1955 F-4-R-2 #157: Inventory of Species Present in Benbrook Lake, Benbrook, Texas

STATE Texas PROJECT NO. Fun-.34 Job 35 PERIOD June 1,1955 ~ Oct. 31, 1955 SEGMENT COMPLETION REPORT BY ROBERT N. HAMBRIC ASSISTANT PROJECT IEADER TITLE Inventory of Species Present in Benbrook Lake, Benbrook, Texas. OBJECTIVES To determine the species present and their relative abundance as well as the ecological factors influencing their distribution. 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 which is 69h feet above sea level. Rainfall has been light during the last few years over the entire drainage area, which permitted the lake to fill to only about onemfcurth or one« third of its normal capacity. The lake was stocked with 550,000 fish during 1953, of which 370,000 were largemouth bass. Table 1 lists all fish that have been stocked in Benbrook Lake by State and Federal Hatcheries. The impoundment was closed to fishing in September 1953 and remained closed until June 1, I954. Fishing pressure was extremely heavy the first few days of the span season, but not so intensive theremafter. COIIECTING METHODS The fish population was sampled each month by gill nets with meshes of i to 3 inches Square measure. Periodic checks were also made with minnow seines measuring 30 by 6 feet with % inch mesh. 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 development, and stomach contents. A checklist of the fishes collected frcm Benbrook Lake is recorded in Table 2. RESULTS OF SEINING COLLECTIONS Seven seine collections were made to catch 621 specimens of fish numbering 19 species. Table 3 records the number of each species collected and the percentage of the total number that it represents. Minnows and other forage fish were scarce during the time that the predaceous species, mainly largemouth bass, were abundant. (The beginning of the present survey coincided with the initial large bass harvest from the lake, but work done immediately preceding the present study corroborates the above statement.) Only two small shad were caught in the sei.ne samples taken in July 195%, indica.ti.ng the spawn of that species had been heavily prayed upon and adequately ”“RbellPd when largemouth base were abundant in the lake. It was further noticed that fry and fingerling bass were also absent from the seine collections taken during the summer and fall of l95h. If hatching had been successful the spawn evidently had fallen prey to the larger fish. As the forage fish in the lake began to multiply they were naturally taken in larger quantities in the seine collections. Shad became so abundant during the fall of 1954 and in 1955 they accounted for 53.h8 percent of all the specimens collected. This was a very high increase over the 1.58 percent that they represented in the seine samples of the previous survey. RESUITS OF NETTING COLLECTIONS A total of 79 gill net sets were made from June 195h through October 1955 to produce 981 specimens representing 19 species. A tabulation of data from the net collections is given in Table A. The fish population in Benbrook Lake changed from predominately game fish to mostly rough fish during the 17 month period of this study. Table 5 offers a comparison of the present game fish and rough fish odpulations of the lake with those of the previous survey. The rapid increase in the rough fish population in Benbrook Lake has been an interesting development and is due, in part, to the unique history of the lake which immediately preceded this survey. A better understanding of the problem may- be had by a study of Table 6 which compares the results of the present ahd last segments net collections by species, showing the percentage of the total catch by both number and weight and the average ”K” factor for each period. During the time that the lake was closed to fishing the overcrowded bass were continuously hunting for food. Nearly all types of animal life were heavily prayed upon, ins eluding other base. Although, they could not have existed forever under such starvation conditions the base were quite effective in devouring the spawn of all fish before it had a chance to grow off. Then when some 250, 000 base, plus many f.ish of oth.er species, were harvested from the lake during the first part of dune l95t it left the impoundment with insufficient predators to adequately control the spaw.o of the remaining species. It was during the summer and fall of 195a that the spawning of carp, shed and spotted sucker was so successful. The writer believes it is worthy of note that three of our better predators are not found in the lake. These are the gars, flathead catfish, and white bass. Sim gill net sets made during June and mideuly, following the heavy fishm ing pressure in early June, produced only 9% specimens of which onemhalf were large mature shad. Inspection of last segmentis records revealed that each set ' averaged 75 fi.sh per net duri.ng that period of inventory. Large carp and shed accounted for 30 percent or more of the few fish caught from June to October. A great many unmolested schools of small shad were seen on the surface for the first time in October denoting a build up of food and a scarcity of predatory fish at that time. Adequate samples of fish were caught in the nets from October 195% through October 1955. Shad were the most abundant species captured, followed by base, carp, and spotted sucker. Many of the bass caught were probably those stocked during the fall of 195M as little evidence of a successful bass spawn was found for that year. Internal inspection revealed that malnutrition had caused many of the mature bass to reabsorb their eggs. Carp and spotted suckers have multiplied fast and at various times each has composed a major part of the net catch- White crappie were collected in limited numbers from October until July. Most of them were small. Good catches of crappie that weighed more than 8 ounces each were taken in August and September. There was no previous indication that this sizengroup of crappie were in the lake in appreciable numbers. The crappie has increased from almost nothing to better than 8 percent of the total net catch. The bullhead catfish population is stillghigh and during the last 17 months has more than doubled in representative percentage of the total fish-netted. The yellow bullhead was slightly the mCre abundant of the two species during the previous study but was outnumbered 2 to l by the black bullhead in the present survey. It seems possible that the yellow bullhead may disappear from the lake in the future. The channel catfish population has remained relatively stable during the past three years. One of the more interesting developments of the lake has been a marked change in the largemouth bass population. This species has decreased from a former 85 percent to the present 16 percent of the total net catch. Such a drop would seem natural when one considers the large harvest of bass taken from the lake in 195M. It is apparently better to have a smaller number of healthy bass in an impoundment than to crowd the water with more fish than it can support. An examination of the past records of the lake revealed some interesting changes in the health and general condition of the bass. The extensive parasitism, malu nutrition, slow growth, and predation upon like species that was present during the crowded condition was noticeably lacking in the present study. Neither was there any indication of reabsorption of eggs by base during the last spawning season, and the increase in growth rate was accelerated when forage fish became abundant in the lake. Bass that averaged 10% ounces when the lake was closed to'fishing in Sept~ ember averaged only 11% ounces when the lake was reopened to fishing the following June. During the next 17 months, while the lake was opened to fishing, the bass more than doubled in weight for an average of 1.58 pounds for all fish netted. The stomachs of the fishes were examined to note all conspicuous food present. Many of the food items listed as unidentifiable fish remains were quite possibly shad. Table 7 records the food items found and the frequency of their -occurrence for each species of fish studied. By an inspection of the data collected during the past and present surveys on Benbrook Lake it is noted that a rapid change in fish population, either in types or numbers, may upset the lake balance causing it to fluctuate from one extreme to another. It is recommended that further study be made of Benbrook Lake in order to follow the development of that impoundment. SUMMARY 1. Benbrook Lake was sampled with minnow seines and gill nets from June 1, 19st to October 31, 1955. 2. A total of 621 specimens were collected by seines and 981 fish were taken with nets. 3. Shad accounted for 22 percent of the total net catch as compared with less than 3 percent found in the previous study. 4. Largemouth bass represented 16 percent of the fish netted as compared with 85 percent found in the previous survey. 5. The fish population changed from predominately game fish to mostly rough fish during the 17 month period of this survey. ' 6. Bass grew much faster after the lake was opened to fishing. 7. Malnutrition, parasitism, and the reabsorption of eggs was not present after the crowded game fish population of the lake was alleviated. 8. A rapid change in fish pepulation, either in types or numbers, may upset the lake balance causing it to fluctuate from one extreme to another. HmaHe H. mmdoweew maooWHom om Wear so woodeoow wemmeeowec Zm% we Hmmw a Qmaoaee my“ mem. memosmm mew Hemp swam eoamsm QWmBSmH omdwwmr flHodeGWCm sooamdomv Howmmeoodw wmmm AZHowowdewom mmHEOMmemv flmwaooaw wemm mowmeooee dam noeoomchmv wemmee msowwmw He.oewm awoeowo wow“ mwoomHHH moowwmr Hewoswm smoHoowMHomv Hofimmmw msowwmw Abewoewm aemmHOdem MeHHosdewww mcomew memoewm mswwdomv SWwae mewmwm Awoeoxwm mooswmwwmw wwmmw oemwwwe Avosoxwm owmeosmoowmdva Table 2. Checklist of Fish Species from Benbrook Lake, Texas, 195h-55. Common Name Scientific Name 1 Gizzard Shad Dorosoma cepedianum 2. River Carpsucker Carpiodes carpio 3. Grey Redhorse .Moxostoma mcongestum M Spotted Sucker Minytrema. melanops 5. Carp Cyprinus carpio 6. Redfin Shiner NotroEis umbratilis 7. Brazos River Shiner Notropis brazosensis 8. Blacktail Shiner (Spottail) Notropis venustus 9. Red Shiner (Redhorse) Notropis lutrensis 10. Parrot Minnow Pimephales vigilax -11. Fathead Minnow Pimephales promelas 12. Southern Channel Catfish Ictalurus punctatus 13. Black Bullhead Ameiurus melas 1H. Yellow Bullhead Ameiurus natalis 15. Blackstripe Topminnow Fundulus notatus 16. Gambusia Gambusia affinis ‘7. Largemouth Black Bass Micropterus salmoides 3. warmouth Chaenobryttus coronarius 19. Green Sunfish Lepomis cyanellus 20. Redear Sunfish Lepomis microlophus 21. Bluegill Sunfish Lepomis macrochirus 22. Yellowbelly Sunfish Lepomis auritus 23. White Crappie Pomoxis annularis 2H. Dusky Barty Hadropterus scierus 25. Logperch Percina caprodes 4. 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