TPWD 1954 F-5-R-1 #76: Inventory of species present in Oak Creek Reservoir at Blackwell, Texas

STATE Texas WW mum—“mm Segment Completion Report by Lawrence Campbell TITLE Inventory of species present in Oak Creek Reservoir at Blackwell, Texas. OBJECTIVES To determine the species present and their relative abundance as well as to determine the ecological factors influencing their distribution. PROCEDURE Sixtywsix gill net collections were made at twelve netting stations in Oak Creek Been ervoir. Experimental nylon gill nets, measuring 125 ft. long x 8 ft. in depth and made up in five, 25 ft. sections were used. Mesh size for these nets increased progressively in each following section at one—half inch intervals, beginning with oneuinch mesh and termim nating with a threewinch mesh section. Twentymthree seining collections were made at eleven seining stations in the reser~ vo In nearly all collections, both 26 ft. % inch mesh bag seines and 15 ft. e” common— sense seines were used. To estimate relative abundance a count was made of all individuals taken in two hauls with a 26 ft. %" mesh bag seine for each collection. In addition to that work other seining collections were made to determine seasonal distribution of species and to secure samples of fry after the spring spawning of fishes. For this latter work, four ft. common sense seines with a“ mesh and others with lflé" mesh were used. Water analysis for dissolved carbon dioxide and oxygen content was taken each month and surface temperature, pH and climatic conditions were recorded for each netting and seinm ing collection. Turbidity was taken for six collections. The netting collection samples for principal species were weighed, measured and sexed in the field. A sample of each individual‘s scales was saved and stomachs containing food were preserved for laboratory study. Similar work for seining collections included identim fication and counting oniy and where the identity of an individual was questionable, the fish were preserved in 10% formalin. FINDING Oak Creek Reservoir is located approximately three miles southeast of Blackwell, Texas. The impoundment creating the reservoir is about six miles east of the confluence of Bushy and Oak Creeks. The dam is 3,800 ft. long, earth fill construction, and was completed in 1952 by Campbell Construction for the municipalities of Sweetwater, Bronte and Blackwell. The impounded water is conserved for the municipal and industrial consumption of those cities. fspillway _ When at emergencyflevel, the lake will have 1,500 surface acres and will store about 52,900 feet of water. At that elevation the reservoir will have about twenty miles of shore~ line. , ' 2. The contributing watershed of 222 square miles is primarily San Angelo sandstone for~ mation and top soils are usually Frio clays, black lime sands and sandy loams. Climate for rhe watershed is semi-arid, having an average rainfall of 24.35 inches. Reliable informs» in pertaining to the average annual discharge of Oak Creek was not available. However, there is no permanent stream flow above the reservoir and run-off is extremely variable. Vegetative cover for the contributing area is predominantly mesquite-grassland association and the area is employed for farming and ranching. The lake's water is clear to shghtly turbid. A maximum turibidty of 5 was recorded in May 195M. Maximum carbon dioxide recored for the period was 12 ppm and a minimum dissolm ved oxygen content of h ppm was recorded at that time. Dissolved carbon dioxide is usually about 8 to 11 ppm and dissolved oxygen about 6 to 8 ppm. Maximum surface temperature re- corded was 76 degrees F. and a minimum of #9 degrees F. was taken. pH was 8.2 ~ 8.h. FINDING Excepting algae and a few concentrations of pond weeds (Potomogeton natans) there is no aquatic vegetation in the lake. 'Willows (Salix niger) and pecan (Hicoria sp.) are numerm one near the mouth of Bushy Creek. The remaining shore vegetation is mesquite (Prosopis julifloria.) Gill Netting Collections Only threemhundred individuals of eleven species were taken in sixtywsir experimental gill net sets, average of .0029 fish per ft. net. In Table 1, netting collections indicate that the largemouth black bass pepulation may be increasing gradually or at hast maintainw ing itself and that bullheads (Ameiurus natalis), river carpsucker (Carpiodes carpio) and white crappie (Pomoxis annularis) appear to be increasing more rapidly. However, there is r obvious trend toward dominance by any species and since the average catch was only one l .h per 286 ft. of net, it is concluded that the sites selected for netting were not repre- sentative of the lake andfor there are so few individuals of the species named present that the lake may be considered to be under populated. Oak Creek has been increased by a series of rain from 8,000 acre feet in August 1953 to 32,000 acre feet in June 195M. However, as shown in Table l, the number of individuals taken in each collection have increased for the last half of the year. Seining Collections Twentywthree seining collections captured 1,732 individuals of fifteen species. Be~ cause greater confidence is usualy expected in a larger sample, it is believed that the perm centages for smaller forage fishes (Gambusia, Notropis and Pimephales) may be more accurate within that group than percentages for other species. Numerical increases in largemouth black bass (Micropterus salmoides) and white crappie (Pomoxis annularis) taken by seining during the last quarter, indicate successful 1953 spawns by those fishes and although not shown in Table 111 tabulations, largemouth black bass and river carpsucker fry (Carpiodes carpio) were taken with a fry seine in June 195M. REMARKS It is apparent that sampling has been insufficient to indicate fish populations in this lake. For that reason and because the lake has increased to four times the original body to be surveyed, it is necessary that at least twelve months additional work be done be- for the inventory can be completed. Checklist of Fish Species for Oak Creek Reservoir June 22, 1953 to June 22, 195h Common Name Scientific Name 1. Longnose gar Lepisosteus osseus 2. Giazard shad Dorosoma cepedianum 3. Smallmouth buffalo Ictiobus bubalus a. River carpsucker Carpiodes carpio 5. Carp Cyprinus carpio 6. Blacktail shiner Notropis venustus 7. Red shiner NotrOpis lutrensis 8. Parrot minnow Pimephales vigilax 9. Southern channel catfish Ictalurus punctatus 10. Yellow bullhead Ameiurus natalis 11. Common mosquitofish Gambusia affinis l2. Largemouth black bass Micropterus salmoides 13. Warmouth bass Chaenobryttus coronarius 1%. Green sunfish Lepomis cyanellus 15. Redear sunfish Lepomis microlophus 18. Spotted sunfish Lepomis punctatus 17. Bluegill Lepomis macrochirus 18. Western longear sunfish Lepomis megalotis 19. Freshwater drum Aplodinotue grunniens SUMMARY U.) (3‘3 Sixty—six gill net collections were made at 12 netting stations in the reser- voir. Twenty-three seining collections were made at 11 seining stations. Water analysis was taken each month and climatic conditions recorded. All fish taken by netting were identified and counted, and in all seining er» cept where fry seines were used, the catch was identified and counted. 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