Lithuanian National Report on Salmon by Vytautas Kesminas VU Institute of Ecology

Transcription

1 Lithuanian National Report on Salmon by Vytautas Kesminas VU Institute of Ecology

2 INTRODUCTION Monitoring and restoration works of salmon and sea-trout have been carried out in accordance with Lithuanian Salmon Action Plan, Monitoring took place in 80 rivers inhabited by salmonids, sites Responsible institutions are Institute of Ecology of Vilnius University and University of Klaipėda

3 Lithuanian Salmon and Sea-trout restoration and protection program for Action plan: Juridical institutional regulation, Protection of migration ways and spawning places, Restoration of natural spawning places, Scientific research and monitoring, Artificial rearing, Education and teaching.

4 Material and methods Monitoring of smolt migration. Lower reaches of Mera, Siesartis and Veiviržas rivers Monitoring of parr abundance of salmonids. Electrofishing (Zippin, 1958; Seber, Le Cren, 1967; Bohlin et al., 1977; Junge & Libosvarsky, 1965; Guidelines.., 1997) Monitoring of spawning nests. Žeimena, Mera, Vilnia, Upper Minija, Veiviržas, Šalpė rivers

5 Material and methods Telemetry study Tagging study Genetic study Migration of salmon and sea-trout (CPUE) into the Nemunas river basin

6 Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Mera Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Žeimena Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Šventoji Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Neris Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Bartuva Venta Venta Venta Šventoji (Baltic) Minija Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Nemunas Jūra KALININGRAD REGION Salmon and sea-trout rivers Sea-trout rivers Lost or unimportant river sections Monitoring stations: salmon and sea-trout - 50 st. sea-trout st. POLAND Dams LATVIA BELARUS Baltic Sea Curonian lagoon

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8 Tons, utilization Catches of Salmon. Fishing quota (Nb of individuals) Total catch (Nb of individuals) Utilization (%) Total catch (Tons) Year Nb of individuals

9 3.6. Age and Length Composition and Mean Weight of the Catches Data of 68 migrating adult salmon caught in Curonian lagoon been analyzed. Total length of salmon varied from 51,6-120 cm, weight g. Majority of analyzed salmon spent 2 years in the fresh water. Salmon sea life ranged from few months up to 6 years and majority of salmon spent 1-2 years in the sea. Male consist only 12 % of all caught salmon

10 Length classes of migrating salmon caught in Curonian lagoon in autumn of 2006 m. 3 2,5 2 vnt. 1,5 1 0, , , , ,9 Kūno ilgis L, cm

11 Fishery regulation During salmon and sea-trout migration, commercial fishery is under regulation in Klaipėda strait and Curonian lagoon. Fishery is prohibited the whole year round in the Klaipėda strait from northern breakwater to the northern border of 15- th fishing bay. From September 1 till October 31, during salmon and sea-trout migration, fishing with nets is prohibited in the eastern stretch of Curonian lagoon between Klaipeda and Skirvyte, in 2 km distance from eastern shore. From September 15 till October 31 fishing is prohibited in 1 km radius from Šventoji and Rėkstyne river mouths and from southern and northern breakwaters of Klaipėda strait. License fishing is allowed from 1st January of 2007 till 1st of October in designated stretches of listed rivers. The minimum size of salmon and sea-trout for commercial fishery is L 60 cm

12 4.2 STATUS OF WILD SALMON POPULATIONS here are 12 rivers in Lithuania inhabited by salmon populations of different abundance. The status of these rivers differs. Purely natural salmon population inhabits Žeimena River and its tributary Mera, Saria. Mixed, i.e. natural and reared populations are in the rivers Neris, Šventoji, Vilnia, B. Šventoji, Dubysa, Siesartis. Populations formed of reared salmon inhabit Virinta, Vokė, Minija rivers and some smaller their tributaries. In the latter rivers artificially reared salmon juveniles are being released for several years already.

13 Dynamics of salmon parr abundace in the Žeimena River catchement 6 Lašiša 5 vnt/100 m Žeimena Mera Maž. intakai Vidurkis baseinui

14 Dynamics of salmon parr abundace in the Neris River catchement 8 Lašiša vnt/100 m Neris Did. intakai Maž. intakai Baseinas

15 4.3. POTENTIAL SALMON RIVERS Salmon density was higher in some larger tributaries of Neris and Šventoji River. Salmon parr were recorded at 18,2 ind./100 m² density in one stretch of Šventoji, average densities in this river were 6,1 ind./100 m². In Siesartis tributaries salmon parr densities were estimated at 36,2 and in Širvinta 10,9 ind./100 m² respectively. In other potential salmon rivers parr density was low.

16 Dynamics of salmon parr abundace in the Šventoji River catchement 18 Lašiša vnt/100 m Šventoji Did. intakai Baseinas

17 4.4. Status of reared population Summarizing, the results of restocking efficiency of salmon and sea-trout this year were better, than in previous one. However, they significantly differed. It was established, that restocking efficiency in smaller rivers is much greater than in larger ones. The survey indicates that in the larger rivers mortality of juveniles is greater, the estimation error being greater, though. No salmon releases were conducted in 2007.

18 4.6. Smolt production Estimated salmon smolt production in Lithuania amounts to individuals. Compared with the last year (2006, 5741 ind.) smolt production increased 2,4 times. Biggest index increase was estyimated in Neris, Žeimena, Šventoji and Siesartis rivers. 86 % of total smolt production originated from these rivers. Smolt production in other salmon rivers is significantly lower and ranges from 0 to 412 individuals.

19 Fig. 3. Total salmon smolt production in Lithuania in years Smolt production Years

20 Sm olts, ths 4. Fig. Salmon smolt production in Lithuanian rivers in years according to electrofishing surveys Years Žeimena Neris Šventoji Siesartis Vilnia Other

21 Comment on salmon smolt production in Lithuanian rivers Salmon restocking program in Lithuania started in 1998 and there are lots of measures implemented every year to increase salmon population, including artificial rearing, construction of fish ladders, protection of spawning ground, stock monitoring, and scientific projects. Despite the measures taken, according to the data of salmon monitoring smolt production in Nemunas basin increased very slowly. Strong increase in production was observed only during the recent years. Smolt density increased from 5741 ind. in 2006 to ind. in This could be influenced by good hydrological conditions and means directed towards protection of spawning grounds which were carried out for three subsequent years. Implementation of these measures helped to stabilize salmon population in Lithuania and prevented possibility for salmon extinction in Lithuania. Also salmon smolt production is affected by other factors as well. Water temperature in Lithuania rivers was well above average during the last few years and water levels were bellow normal. Also one of main concerns in salmon rivers remains pollution. Another important factor is the fact that Lithuanian rivers are lowland type and there is a lack of habitats for salmon as only some stretches are suitable for smolts. Quite high mortality rate caused by predators is another problem. Predators density is significantly higher in Lithuanian rivers compared with typical salmon rivers in north Baltic.

22 9. TAGGINGS 2006 in total about 1026 salmon smolts were tagged with Carlin and anchor tags individuals were tagged just before releasing in River Minija and 26 ind in River Siesarties then performin migration monitoring in total about 500 sea trout smolts were tagged with Floy anchor tags n total about 300 salmon and sea trout smolts were tagged with Floy anchor tags. No fin clipping was made in Lithuania.

23 Inventory of spawning places Inventory of spawning places was conducted in November 2007 in 4 rivers of Neris catchment (Žeimena, Mera, Vilnia, Siesartis), and 5 rivers in Minija catchment (Minija, Sausdravas, Žvelsa, Veiviržas and Šalpė). Spawning intensity in the Neris catchment was estimated based on number of spawning nests in 1 km length of river stretch and total area m². In the Minija catchment, density (Nb) and total area (m²) of nests per ha of river were recorded. Only those greater than 0.3 m2 were considered. In the river Žeimena the number of spawning nests is relatively 1,1 times higher, in the Mera River it is 3,2 times higher, as in the last year and in the Vilnia River it is 2,3 times higher. In the Siesartis River number of spawning nests density a little decreased, when in 2006 m. In the last river spawning intensity was relatively high.

24 Inventory of spawning places in Žeimena river m. Bendras plotas ,2 1,3 1,4 1,33 0,85 1,12 1,45 1, ,32 5 4,5 4 3,5 3 2,5 2 1,5 1 0,5 0 Tankis ir vid. plotas bendras plotas, m tankis, vnt/km vid. plotas, m 2 2

25 Stirnelė-Dubinga Pabradė Jusinė Žeimena Skerdiksna SUTARTINIAI ŽENKLAI: Upės Lizdavietės Neris Gyvenvietės Geležinkeliai Keliai

26 Efficiency of functioning of fishways Belmontas fish-way on Vilnia River Valtūnai fish-way on Siesartis River

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