TPWD 1955 F-5-R-2 #167: Inventory of Species Present in San Angelo Reservoir

‘ STATE Texas PROJECT N0. F~5~R-2z Job 3-3 / a V! PERIOD June 222 1951+ .. Max 12 1955 xiflfiégr Segment Completion Report Lawrence S. Campbell Project Leader William G. McClelland Assistant Project Leader Inventory of Species Present in San Angelo Reservoir. OBJEQTIVES To determine the species present and their relative abundance as well as to determine the ecological factors influencing their distribution. PROEEDURE Thirtynnine gill net collections were made at twelve netting stations in San Angelo Reservoir. 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 pro- *essiweiy in each following section at onewhalf inch intervals beginning with oneminch 3s.h and terminating with a three inch mesh section. Ni.neteen seining collections were made at fourteen localities along the lake 1” shore. In nearly all collections both 26 ft. i” mesh bag seines and 15 ft. 3 mesh comm non sense seines were used. To estimate relative abundance at each seining station a {3313 mot was made of all individua.ls taken in two ha.u1s with a 26 ft. i” mesh bag seine. In additi.on. a four ft. common seine with 1/16” mesh was used to collect samples of fry ,wliQWlng spring spawning We .ter analysis for dissolved carbon dioxide and oxygen content was taken ea ch moo.n and surface temperature, pH and the climatic conditions were recorded for each ne+fioc collection. In net collections, most fish were identified; counted. weighed, measured and sexed in the field. A sample number of each species was examined for stomach content and a scale sample taken. On occassion it was necessary to preserve an individual. its stomach or some other organ for more detailed examination in the laboratory. When this was required? the specimen was preserved in 10% formalin. FIEDINQ During the segment the reservoir receded from elevation 1893 to elevation 1885, a loss of a.pproximately 12 .107 acre feet volume. In 195M the city of San Angelo purchased all water stored between elevations 1886 a.nd 1908 from the Upper Colorado River Authority. efirst water withdrawn for city use was released during the late spring months of 1955. use method of lowering the lake and the time of the releases may have been detrimental to in Co the spawning activity of several game species, primarily largemouth black bass {Micropm terns salmoides). The lowest dissolved oxygen content recorded during the segment was :Imppm. and the maximum carbon dioxide content obtained from water analysis checks was 7 ppm.“ Minimum surface water temperature recorded was 510 F. and the maximum record was 88U F. Turbidity, except following the rainfall runmoff in June l95h, was 0.0. dotting Collections: Thirtymnine net sets captured 1,3h5 individuals of twelve species. As re“ corded in Table No. I, few significant population ratio changes are indicated by this method of sampling. Numerical increases for gizzard shad (Dorosoma cepedianum), river carp suckers (Carpiodes carpio), and white bass (Morons chrysopsi are apparent, and per~ centages for southern channel catfish (Ictalurus punctatusi, white crappie (Pomoxis annularis), and largemouth black bass (Micropterus salmoides) decreased. No flathead catfish EPilodictus olivaris) were taken in netting collections, but a number of these fish.are known to have been taken by sportsmen. a n1! .ifllgg noilectiOflSE Co (7‘ During the segment nineteen seining collections captured 1,7t2 individuals of sixteen species. Mosquito fish (dambusia affinis), giszard shad {Dorosoma cepem disses}. and spotted sunfish (Le omis pgnctatug} were less numerous than in 1953m54, and percentages for red shiners Emotropis lutrensis), Blacktail shiners (hotropis EEEEEEEEEB and parrot minnows (Pimephales vigilaxj increased. Juvenile white bass thoronngnrysops) were taken for the first time in October 195a. Because recession of the lake made it necessary to move the location of several seining stations, a dupiication of the first segment work was impossible. emar Kid} ii A continuance of this jot has been requested and approved for next segment. SUMMARI gum} The'volume of the lake was decreased by 12,107 acre feet during the segment. 5, The method and time of withdrawal of water for municipal purpuses may have been detrimental to the spawning of some game species. Notahly largemoath black bass. 3. Netting results indicated an increase in giaaard shad, river carp suckers, and white bass and a decrease in southern channel catfish, largemouth black bass, and white crappie. .ining collections indicated increases in red shiners, blacktail shiners, and parrot minnows. Decreases were noted in mosquito fish, gisaard shad d. 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