, ARCHIVES FISHERIES RESEARCH BOARD OF CANADA Transla^ion Series No. 363 RESULTS OF THREE YEARS OF OBSERVATIONS ON FISH BELOW THE LENIN,.HYDROELECTRIC STATION ON THE VOLQA By A.. T. Diûzhikov (Saratov Branch at the State Institute-for Lake and River Fisheries--GosNIORKh) Original title: Rezultaty t^ekhletnikh nabliûdeni^ za rybami v nizhnem befe volzhskoi GES im. V. I. Lenina. From: Voprosy Ikhtiologii, Vol. 1, No. 1(18), pp. 69-78,: 1961. Moscow. Preliminary translation by W. E. Ricker Distributed by the,.AFisherdes, Res:éaroh:,Board of Canada Biological Station, Nanaimo, B. C. 1961 .e* This is a preliminary translation prepared for the use of the Fisheries Research Board of Canada. It is not a definitive English version of the article, and it has not been checked or approved by the author. The Volga River below the ci^y of Kuibyshev was closed off by.the Volga Hydroelectric Station in the autumn of 1955. The Kui.byshev reservoir was filled in three stages: autumn 1955, spring 1956, and spring 1957. The right bank below the hydro- electric station is steep: the Zhigulev Mountains.come ri,ght down to the water. On the left side, for 12 km the river is held back by the dam of the navigation canal, which prevents the exit of the water from the main channel into the system of side channels. On the side of the river adjacent to the hydro- electric station there is an accelerated current speed especially at high water. In addition to its seasonal fluctua- tions, the level of the water below the dam is subject to sharp weekly changes, caused by the working plan of the hydroelectric $tation, In comparison with the former regime of the Volga, below the dam there has been some reduction in the height of high water, and some increase in the mean level, as well as slower warming of the water in spring and cooling off in autumn. In the channel of the river sandy bottom prevails, but along the right bank there is a zone of gravel bottom, expanding locally into bars where lithorheophilic fishes spawn. In the part of the left bank region lying near the hydroelectric station, on islands and on narrow strips of the inundated parts of the right bank, lithorheophilic iish can reproduce. The directions of the currents below the dam change in relation to the flow of water through the sluiceways of the dam and the turbines (Diûzhikov, 1958). Species composition and concentration of fishes Below the dam there are found 6 anadromous species of fish and 25 river speçies. Among the anadromous fishes the following occur in commercial numbers: the Russian sturgeon or osëtr [Acipenser üldenstëdtii], beluga [Huso huso], inconnu [Stenodus leucichthysJ, and in some years the black-backed shad [Alosa kesslerT . The Caspian lamprey [Cas.piomyzon wagneri'] appears there in abundance at the end of winter and early spring, a time when the break-up of the ice and ice movements interfere with its capture. Among the river fishes, those usually occurrin in the commercial catches are the sterlet, ci enser ruthenus^, bream [Abramis brama], white bream. [B1 icça;., .' oel-ian _., blue bream [Abramisaal^lérus , white-eye [Abramis sapa zander [•Stizostedion lucio erca], Volga zander LS. vol ensis], perch [Perca fluviatilus , pike [Fsox lucius], ide Leuciscus idus], asp LAspi.us aspius], catfish LSilurus lanis , chekhon Pelecus cultratus], burbot [Lota lota , roach Rutilus rutilus], and rarely other speciès. Infine-méshed experimental fishing apparatus the gudgeon [Gobio gobio] has been taken in consider- able quantities, and raréT-ythe sculpin [Cottus gobio] and spiny loach [Cobitis taenia]. Before the closing of the river by the Volga gydroelectric Dam the most numerous fish were bream, white-e'ye, blue bream 2 and white bream, which we will link together as th^"bream group, and sterl.ets were numerous, After closing of the xiver. the fish fauna below the dam began to'changé; In 1956:the"relâtive abundance of the species was that typical.of "rive.r "species, -but in the following two years the.,percentage of sterlets and,of the bream-group decreaseda while the.percentage of'pi-ke and percids increased sharpl.y (Table 1). Considerable accumul.itions developed,, below the dam9 of " adult anadromous hi6mal os"UYr .(Berg.1 1934), They arrived at the dam toward the end of summer and early autumn-;. at the end of September in the clear water [page 70,] a h;i__gh concentration of sturgeon could already be observed,The maximum catches of' one "vozmilkall per night in September 1956 were 15420 sturgeon, in 1957 10y15, and in 1958 10-15. By trawling"with a small trawl from a seiner in September 1958 2-3 sturgeon were c^pu.ght per minute. The catch of a 100-metre series of 60-rmm fixed gill nets set in the quiet zones at the sâmé time was 6-7 sturgeon per night. The inconnu was encountered near the Volga Hydroelectric Station from early spring to late autumn, but its catches were not very great, in all 3-5 fish per night per floatin"g. gill net. Lampreys in 1956 and 1957 were caught as occasional_,... specimens in early spring. In May 1958, at the 15ui:.^c^^.r^^.)h,ou^;ing the hydroelectric station, a massive accumulation of lampreÿs was observed; many of them were caught with bag-liké nets made of inetal. Occasional specimens of beluga were encountered,_but according to the fishermen they were more frequent than formerly. The akhany and "vozmilki", used to catch sterlets below the dam" frequently were torn by the beluga--even those made from kapron 60-mm mesh webbing. Hence the catches do not reflect its true abundance. Black-backed shad were caught occasionally in June and July, at a distance of 10-20 km below the hydroelectric station... In 1956 400-metre seines caught several tons of shad in the:main channel 25 km below the dam. Of the river fishes, in 1957 and 1958 accumulations were observed below the dam of pike only, which were.moving down- stream in large numbers from the Kuib.yshev'reservoir. The abundance of pike below the dam began to,grow in the autitmn of 1956 and gradually increased during the two following years. In the 100-metre series of 50-60-mm kapron fixed gill nets 5-10 [per day?] were caught in the spring of 1957, 20-25 in summer, and 35-40 in autumn; in the autumn of-1958 the average catch amounted to 50 individuals, and pike comprised 40% of the numbers and 90% by weight of all fish caught at that time below the dam (Diûzhikov, 1959). Few other river fishes were encountered here. This is to be explained by the absence of a 3 Table 1. [page 70] Species distribution of catches below the Volga Hydroelectric Station (%). Total Anad- Ster- Bream Per- Year romàus let group cidae Pike Ide Others %. Pieces 1956 9.2 17.1 59.9 2.9 0.1 7.0 3.8 100.0 2816 1957 6.2 13.0 30.1 11.1 30.4 5.2 4.0 100.0 2898 1958 4.8 7.7 31.4 11.1 39.5 2.7 2.8 100.0 1797 Table 2. [page 71] Length distribution of osetr [Acipens-er 21:11denstgdtii] below the Volga Hydro- - electric Station. Body length to tip of tail, cm Year 0-50 50-100 100-150 150-200 nn 1956 9 66 132 5 212 1957 17 72 310 10 409 1958 32 12 183 10 237 r. Table 3. [page 71] Weight distribution of osëtr below the Volga Hydroelectric Station. Time Weight, kg of catch 0-5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 Fall 1956 4 32 11 3 - 1 - 1 52 Fall 1957 • 20 88 84 41 18 10 5 - 266 Fall 1958 2 19 31 11 3 1 - - 67 4 sufficiently large ^pawning stock below the hydroelectric dam and in the reservoir. .6 The composition of the stock of certain species of fishes The stu^geon below the dam were re.presented by fish of very varied size and weight (Tables 2 and 3). However the sexually mature part of the stock was well separated from the immatures; individuals in stage III of maturity were lacking near the dam. In 1956 and 1957 the fillin,g.-of the Kuibyshev reservqir was in progress and immature sturgeon in large numbers weré encountL-red near the dam in the sprin.g and summer, f-ewer in autumn. The appearance of young sturgeon in these years near the Volga dam was associated with their downstream movement out of the filling reservoir. Apparently young fish of the older age groups, which are very numerous.in the middle Volga, moved downstream especially intensively (Lukin, 1937, 1947)_ Thbs I— predomlnânce in 1956 and 1957 [page 71] of fi-sh of a length of.. more than 50 cm among the immature sturgeons is to be e.xplairied in this way. In 1958 individuals more than 50 cm were rarely encountered in the sexually immature part of the stock. The sexually mature part of the stock of s.turgeon near the dam was represented by not -particularly large fish ,(less than 150 cm and less than 20 kg). In almost all samples femalés comprised about 20% of the total number of individuals (Tables-;4 and 5). But at the end of the spawning season a sharp increase in percentage of males was observed, occasiôned by their prolonged stay on the spawning grounds (spring of 1956).