.. leES STATUTORY MEETING 1993 C• M. 19931M: 1 6 AnadromouB and Catadromous -Flah Committee Ref.J. .' PRESENT SITUATION OF THE VISTULA SEA TROUT by / R.Bartel Inland Fisheries Institute River Fisheries Laboratory Reduta Zbik 5. 80-761 Gdanak. Poland ABSTRACT The alm of the paper wan to show a present status of ViHtula !H~a trout. Pollution of water .in t.he Vistula River llave brought to reduce population of Yistula sea trout. Wllen Hle Vistula River was dammed in 1969 Yistula sea trout population drasticaly dropped. In 1972.-199c. there were released into the Yistula River from 3~0 000 to 314 000 smolts and from none to 446 100 alevins, yearly. In t111s period the sea trout catches in the Vistula River varied from 30.9 to 12.9.1 t ..Effectivenes of Btocking based ~n sea trout • catches in the Yistula mOl1th and the Vistula River was in average c.95.5 kg/lOOO smolts. C. ~1.1993/t·1: 16 ICES STATUTORY NEETING 1993 Anac~t Fish.Comm Ref.J PRESEHT SITUATIO~OF THE.VISTULA RlVER SEA TROUT Ryszard Bartel Inland Fisheries Institute in Olsztyn River Fisher~eß Lab?ratory in Gdartsk i. Introduction • Vistula river, the blggest Pollsh river, had in the past and still has the biggest popUlation of the se;:ltrout. A steady process of the environment degr~dation, and in concequence worsening of water quality in the Vistula's main stream ehannel as weIl as in the tributary rivers, resulted in a gradual decreRse in catches of fish, also migrating ones, and then in elosing down of fisheries cooperRtives 0perating in the upper Rnd middle ViRtula wRters. The following fisherjes cooperatives were cloRed down: in Krak6w in 19~8, in Wyszogr6d in 1968, .in TarnObr7.eg in 1971 ~nd in ePlliRWY in 1976 (Wisniewolski, 1978; Fig.I),· The other evident proof of worsening of ecological situat.ion in the Vistula river is a decreasing number of the sea trout spawners on the spawning grounds in the Vistula's upper tributary rivers. The very last sea trouts were caught in Sola in 19~6, in Raba in 1957, in Dunajec in 1968 (Bieniarz, ~ysak. 197~; Fig. 1), The fact of catching of the last sea trouts in Dunajec river coincided with construction of the dam in Vistula Rlv~r , in W}oc}awek, Though this dam has a fish pass but the latter does not fUlly comply with the requirements as only limited number of individuais of sea trout passes above it and only single - 2 - individuals are caug~t in vicinity of Nowy Dw6r and Pulawy (Bartel , Zieli().ski, 1991). The recent observations of sea trout migration, by means of sonic tagging (unpubl ished material S of InRt.i t'lt.e of the Russian Ac~demy of Scienees at Rarok and of the Inland Fisheries Institute in Gda().sk) proved that the sea trout had difficultles in finding the entranee in the fish pass positioned in the dam in Wloc}awek. Eeologieal degradation as weIl as the influence of the barriers eonstrueted in river's streams, hindering or making it even impossible for the spawners to reaeh the spawning grounds, have been observed in the Vistula river and some other Polish 4t rivers (Fig.l). Positioning of the dam in the Vistula river in Wloelawek resulted in a eonsiderable decrease in number of smolts migrating from the Vistula eatchment area down to .the Baltie Sea. The number of these smolts, estimated in the 50's and at beginning o f the 60' s, thus prior the other effects, namely state of the environment and dam eonstruction, was on the level of 500 thous. to million (Backtel , BarteI, 1967), while at the present time, it is not higher than about 30 thous. After the dam construction ·aeross the Vistula river in Wloe}awek the river Drw~ea remained the single bigger tributary river having the conditions for nat.ural spawning of the sea trout. Though its potential possibilitiel'l underwent limitations resulting from pollution prOblems and construetlon of artifieial barriers aeross Drw~ea's tribl1tary rlvers, the role of thil'l river, with respect to population of Vistula river sea trout, is essential, aB it favours an inerease of the genetjc variability of Vistula SBa trout pO~11ation due to the fact that the fish spawns in natural conditionR. BeBtdes, in Drw~ca there spawn the sea trouts represent.lng winter popülat.ion (Borz~eka,. personal communieation). - 3 The importance of sp~wning of winter sea trout in Drw~ca riv~r should be emphasized as the rearing of smolts of this particular sea trout is not carried out at present. The aim of this worK IR to present the Vistula sea trout management in the recent years. Z. Materials ~d methods. Materials from the "Information Service on Salmon Management" initiated in 197e and iRsued in the form of manuscripts of the Inland Flshery Institut~, Rupplem~nt~d with m~terials from the i9~ • "Gospod~rka (R~rtpI, R~rtel~ Rybna" 19766 Zielirtski, 1977, 1978, ,~lj6 >i",-,b,.l gÖCL1.1b, ~'3 B 1~,b,--t'3 M. IIBlI 1979,{~8"11982, 1984\1and wlth the materials collected for the "-I"'). rii'jnie wol ... ki '50 Ll&!c("("j~~1)/' "Information S~rvic~ "but not. published - w~re llsed to prepare this pap~r. Construction of Vistula dam In W}oc}awPK c~uRPd changl" in fish~ry relations in the Vistula river. This ch~ng~ fOllnd its ~ reflection in catches of migrating species such as vimba and sea ·.{rout. Catches of the latter species increased below the dam whil~ dropped nearly to zero above the dam (Fig.2 Sych, BarteI, 197Q). tho!? The decre~sing number of smolts inVVistula has been observed mllch ~~rlier and ther~fore the attemptR w~remade to replenish the unR~tisfactory Vistula trout's spawninq by stocKing with the parr reared in hatcheries. As the number of eggs obtained from th~ ViRt\lla t.rout. was not suffieient it was d~eid~d that the Vlstu]a eatchment area would be stocked with the material reared from eggs originating from th~ R~a troutB of Pomerania rivers. Though the number of r~ared atocKing indiy.iduals,· released in - 4 - the ViRtul~ catchment area was continually increasing it did not find itR ~eflection in tti~ Rea'tr6u~ catches. O~the contrary, beqinning from the l~te 70's, a steady decrease of catches of sea trout in Vlstula and ItR estuary, has heen ohserved (Fig.3). Lack of effects of stocking lied in the fact of preference of stocking with parr and presmolts. Elimination of the stocking material originating in Pomerania rivers, from the ViRtul~ stocking, decreased the possibility of stocking with reared smolts and the crossing of the Vistula with dam in Wloclawek almost entirely excluded the upper Vistula triblltary rivers from n~tural spawning. In conRequence there was 4t danger of drastic decrease in sea trou~ population in Vistula. Some hope for improvement of the situation appeared when in 1967 some basins, provided for keeping the Rea trout spawners, were \!)(oS'>(\.kc.,;;ki .~jC·!lt open for exploitation at Swibno in Vistula estuaryv:That enabled obtaining the eggs of Vistula trout for smolts rearing. ThP importance of this object singnificantly increased when the Fishery Cooperative "Certa", fishlng below the dam in Wloclawek. relinquished obtaining of the eggs in 1985. In the years 1972-1984 this Cooperatjve obtained 4.270.000 eggs from spawners kept in @"-fi~l.~I:3IiJ1'jj.Jd . ~18 -\'!1~ -1~~·1 ,(032~, 1'1SG'1~Z;"""h -j'1ZC ... ,b A~gr_: • earth ponds in Nies~Bartel, Zfelinskr;'19"m. I It can bp said that t.he present stat.e of Vistllla t.rout population is the re!'!ult of two positive fact!'! - the presence of basins in Swibno and the stocKin~ with smolts reared from eg~s ori~inating from the .~pawners call~ht in the Vistula pstuary. Number of eggs procured by the Fishery Cooperative in Swibno in the recent cO years ranged from 181.000 in 1979 to nearly 2.000.000 in 1992. while numbpr of smolts released in the same time to Vistul~'s catchement area ranged from 3P..OOO in 1985 to 314.300 in 1990. Number of rel~~Bp.d B~olts to Drw~ca in the years - 5 - 197e-19ge fluctuated from zero in 1973 and 1974 to 128.000 in 19QO and number of released fish in Vi'stula estuary varied from zero in 1975 to 186.300 smolts in 1990 (Fig.4). Besides, certaln numbers of trout alevin were released into the Vlstula rlver. The numbprs of released smolts werp affected not only by the number of obtained eggs but also by the breeders competence in " rearing' andtheir willingness to produce the stocking maie~ial. - The breeders' skills have continually been improving while thelr inclination to real' the smolts was connected wlth the flnancial abilities of the CommiRslon for Stocking and Salmon Management. the latter strictly depending on finances allocated hy thp Ministry' of Agriculture. Ministry of Transportation and Maritime Economy and the Minlstry of Environment Protection. Some insignificant funds were provided by the fishermen catching the sea trout, and by some Provincial Councils. In the conRidered period t97e-1991' the sea trout catches in the Vistula river, between its pstuary and Wloclawpk. ranged from 30.9 tonnps in 19841.0 1e9.1 tonnes in 1990 (Fig.~). At the same t.ime the numher of Rmolt.R, migrat.in!! t.O the sea fluctuat.ert from 74.000 in 10B~ to 348.000 in 1000 (Fig.5).