TPWD 1957 F-5-R-4 #324: Inventory of Species Present in Imperial Reservoir

Report of Fisheries Investigations Inventory of Species-Present in Imperial Rese1.“vo:i.:'n‘g9 near Imperial? Texas by Lawrenee Dé Campbell Eroject Leader DingellmJfihnS@n Erajeet FmSéRmhg Job Bm20 April 15» 1956 m April 169 1957 Ho D. Dodgen m Executive Searetary Texag Game and Fish Commission Aufiting Texas Marion Tfiole William E; Brawn Coordinatar ASSEO Gfiordinat®r J03 COMPLETIQN REPORT State of TEXAS Project No. #EEEEH_wflm Name: Fisheries Investigations and Surveys of the waters”" Joe No. BwEQ Title: “Inventorf of §}ec1es Present in Imyerial_Reservo1r m Period Covered: Amman Inventory data indicated a complete dominance of this reservoir by white bass. The water is highly saline, slightly turbid most of.the timeg and hecanse of the sandy bottom and other factors. the reservoir has a very high productivity of game species. The reservoir is drained at irregular intervals throngh irrigation processes. OBJECTIVES: To determine the species present and their relative abundance and to determine the ecological factors influencing their distribution. PROCEDURE: Twelve gill nets were set at five locations in the reservoir. Experimental nylon gill nets measuring 125 feet long by eight feet deep and made up in five‘9 2§ foot sections were need. Mesh size for these nets increased progressively in each following section at halfmineh intervals beginning with a eneminch mesh section and terminating with a threeminch mesh section. Eight seining collections were made at eight coining stations in the reservoir. In nearly all calf lections, both 26.foot l/t inch mesh'hag seines and 15 foot: l/h inch common sense seines were used. To estimate relative abandance. a count was made of all individ= nals taken in two'hanls with a 26foot . l/t ineh.mesh fry seine water analysis to determine dissolved oxygen content and the quantity of dissolved oath n dioxide was taken for each netting collect1on. Surface temperature. pH and weather conditions were recorded for each netting and seining collection. anhiditg'was taken on two occasions. ‘ In netting collections? samples from each collection and for each species were weighed; measured and sexed. This work was done in the field. A scale sample was taken from a sample number of individuals for each species and stomachs preserved for laboratory analysis. Description a Imperial Reservoir is located ten miles northwest of the city of Imperial near the meeting of the tilirattzaegv'tti'esmi‘9 and Pecos Gonnty lines. The reservoir was formerly'cafled i 2. Zimmerman Reservoir. The reservoir is part of an irrigation system and is used for raisin and controlling releases from Red Bluff Reservoir into the Pecos River. Releases are then diverted as required. Maximum storage is about 2,800 acregfeet and at that elevation the reservoir has about 895 surface acres. The lake is owned by Red Bluff Power and water District and is fished extensively'by sportsmen: from Pecos,‘Midland and disses. The water is usually very high in chlorides (h, 570 ppm to 2,970 ppm), is very hard (3,500 ppm) and has total dissolved solids of about (10,500 ppm). No oxygen deficiencies were recorded, the minimum recorded being 11 ppm and pH was 8.2 to 8. h. The lake, slightly turbid on occasions, has a sandy'bottom and is shallow. The reservoir was constructed by adding dykes to a plays lake. The lake is virtually drained once each eighteen months. Netting_Collections a The following data is the catch recorded by setting fifteen hundred feet of experimental gill net at five locations in the lake. As shown, white bass (Rescue opgxoogs) completely dominated the fish populations. Since it is known that the reservoir was virtually drained about eight months before netting collections were taken the significance of this dominance in relation to the proposed fishery management program is apparent. Gill Rotting Collections from Imperial Reservoir White Bass 161 82 07 18.5 89.51 238 Channel Catfish 1.5a 21.0 .6h . 226 Giasard_8had 26 13 3h h.o 3.12 181 River carp Suckers 8 n.08 28.0 6.73 2&0 Seining_0ollections n The following information and comments are based on coining collections taken at six locations on the reservoir. As previously stated the reservoir has a sandy bottom and is clear of obstructions. For that reason the more extensive coining effort probably resulted in sampling more indicative of the true importance of several species, notably Carp ( Sprinusc carpio ), gimsard shad (Dorosoma cepedianam) and freshnater ram (Aplodinotus ziunniens}. It was obvious, when consideration was given to the entire coining effort, that in the particular seining hauls made in order to estimate population ratios (using the customary twentyasix foot bag seine) that the findings thus obtained by chance were entirely misleading and were significantly distorted as to the tree interrelationship as it was shown to exist by more complete coining with lighter ego uipment. In order to prevent such a misrepresentation, the coining information obtained is included in the following check list. Check List of Speoies by Seining discard shad (Dorosomac cepedianum) a very numerous and at the time this work was done, uniform in sine averaging about 135 mm. “arp (Cyprinus carpio) a less numerous than river carpsuckers but very abundant n localities. Larger specimens than are usually taken by this method of sampling were obtained and there was a conspicious uniformity of size averaging about 25 cm. A number of these fish were found dead along the shore; however the exact cause of this mortality was not determined. River carpsuckers ( Carpiodes carpio) a abundant, taken at all areas coined. Pecos river killifish (Fundulus sp.) a This is prObably the most numerous species for the reservoirg however as indicated later in stomach analysis and as is apparent in work on the Pecos River; the utility of this species as forage is questionable. Redhorse shiners (Notropis lutrensis) a numerous and unusually brilliantly colored. The only shiner taken from the reservoir. Mosquitofish (Gambusia $2,) a taken from the canal supplying the reservoir, but not included in coining collections from the lake. White bass (Roccus chrysops) = Only-two of these fish were captured by coining; however these individuals were aboutifime same size as those taken by gill note. This is regarded as supporting evidence of the uniformity of growth of this species and as an indication that these fish were prObably introduced from the Pecos River then the reservoir was filled in the early spring. Freshwater drum'(Aplodinotus gaunniens) a common occurrence throughout the reservoir. Individuals of_this species were found at five of the six localities seined. gshgdjrstufiigypuhfiflgommeuts e since it is known that the reservoir is usually drained every eighteen months and is greatly reduced-in the winter and then refilled in the early spring, the large numbers of white bass are concluded to have been introduced in the form of fertilised eggs, fry, and/or fingerling sine fish. The size of the fish captured is regarded as indicative of their potential growth rate under favorable conditions, and because of their high ratio and :tho (reservoir-'1iiishdfildl‘iy.i<dl<dlassailant a pest: fishing. There is no known evidence to support the possibility of spawning by this species in the reservoir, and the extreme reduction during the winter months (to a capacity of about l00 acre feet with about 35 surface acres) further indicated that possibility as improbable. The irrigation methods employed by the water and power district (i.e., periodic draining and refilling) offer the possibility of controlling the fish populations within this reservoir by screening or otherwise controlling the fish that are introduced at the time of the winter or spring refilling. If the apparent rapid growth aptitudes of white bass are to be utilised, consideration must be given to means or methods for their introduction as the success of spawning by the species in_the Pecos River is probablthoo unreliable. Recommendation a do managerial effort is deemed necessary at this time. It is recommended that imperial Reservoir be included in and considered as an integrated part of future management plans or programs for the Upper Pecos watershed. It is proposed that under annual recourvey work for the region, this reservoir be included in order to obtain additional data. w Fifteen hundred feet of experimental gill not were set at five locations within Imperial Reservoir. One hundred and ninetyusix individuals of four species were captured. Of this number 161 (82.07 percent) were white bass. 2. Six localities along the reservoir shore were seined extensively and the results of this work indicated that several species were more numerous than indicated by gill net collections. Freshwater drum, carp, and gizzard shad were numerous and uniform in sise° 3. The reservoir is unusually high in chlorides (h,570 ppm to 2,970 ppm) is used bwaed Bluff Power and water District to control releases from Red Bluff Reservoir for irrigation purposesy and is subject to extremezfluetuetiuns. “ ho Imperial.Reservoir because of management practices offers definite fishery management possibilities) and it is recommended that further study of the lake be included in future plans. Prepsred by: Lewrence D. Campbell Approved by: ' Profile“ leader Date? .. _. . Pas-1°11 ._ _. .