Microsatellite alleles

Microsatellite analysis was done by ABI 3100 capillary sequencer (Fig. 1).

Fig. 1. Fragment analysis by the ABI 3100 capillary sequencer of three perch individuals DNA samples for microsatellite Pfla-L10 loci detection.

Several individuals of each species were analysed to check usefulness of selected primers. Results are presented in tables 8, 9-and 10.

Table 8.Microsatellite alleles detected in Latvian perch samples

Microsatellite Alleles

Pfla-L1 124 132

Pfla-L6 131 132

Pfla-L2 245 250 263 273

Pfla-L4 128 130 132 138 140

Pfla-L5 147 149 154

Pfla-L10 221 227 253

Pfla-L9 no product

Svi-L7 199 221 230 243

Svi-L1 393 395 396 400 401

Svi-L10 no product

Table 9. Microsatellite alleles detected in Latvian pikeperch samples

Microsatellite Alleles

Pfla-L1 no product

Pfla-L9 182 190 213

Pfla-L8 164 183

Svi-L7 199 220 221 222 230 235 243

Svi-L10 232 240

Svi-L11 114

Svi-L8 104 133 135 137 144

Svi-L2 no product

Table 10. Microsatellite alleles detected in Latvian eel samples

Microsatellite Alleles

AJMS-3 82 84

AJMS-10 173 177 211

AF237901 171 172 180 182

AF237900 163 171 172 177 180 182

AF237899 180 181 183 184 187 200

AF237902 192 219 222 225 229 231

AF237898 103 105 126 132 145

References

EPRI, 2001. Review and documentation of research and technologies on passage and protection of downstream migrating catadromous eels at hydroelectric facilities. Report No.

1000730, Electric Power Research Institute (EPRI), Palo Alto, CA

Hadderingh RH, Baker HD, 1998. Fish mortality due to passage through hydroelectric power stations on the Meuse and Vecht rivers. In: Jungwirth M, Schmutz S, Weis S (eds) Fish Migration and Fish Bypasses. Fishing News Books, Oxford, p 315-328 ICES, 2006. Report from the ICES/EIFAC Working Group on Eels, Rome 23-27 January 2006.

Annex 3: Report on the eel stock and fishery in Latvia. ICES CM 2006/ACFM Leclerc D., Wirth T., Bernatchez L., 2000. Isolation and charactertization of microsatellite loci in

the yellow perch (Perca flavescens), and cross-species amplification within the family Percidae. Molecular Ecology, 9, 995-997.

Ojaveer, E., Pihu, E., Saat, T. (eds.). Fishes of Estonia. Tallinn: Estonian Academy Publishers, 2003, 416 p.

Stiebrins O., Väling 1996. Bottom Sediments of the Gulf of Riga. 1:200 000. Riga, 54 pp.

Wirth T., Saint-Laurent R., Bernatchez l., 1999. Isolation and charactertization of microsatellite loci in the walleye (Stizostedion vitreum), and cross-species amplification within the family Percidae. Molecular Ecology, 8, 1960-1963.

2.4 GENERAL CONCLUSIONS AND RECCOMENDATIONS FOR STUDIED FISH SPECIES MANAGEMENT

CONCLUSIONS:

• European eels recruited in natural way predominate in Lithuania and Latvia coastal waters;

• Some eels in coastal waters are of the restocked origin. Restocked eels in silver eel stage reach the Baltic Sea and migrate together with naturally recruited individuals for spawning to Sargasso Sea along Latvian coast in Riga Gulf; eel of restocked origin numbers in silver eel stage increase and predominate in coastal waters during migration phase in Riga Gulf;

• Inland eel fishery in both countries depends on artificial eel restocking. No evidences of natural recruitment to inland lakes were observed during the study;

• Naturally recruited eels spend from 1 to 10 years (mean 5 years) for migration to reach the area of study; this suggests that ell recruitment at the glass eel stage (which is typical recruitment stage in other sites of the range of European eel distribution) should not be expected in the studied area, i.e. eels reach Lithuania and Latvia in yellow eel stage;

• The growth of naturally recruited eels did not differ significantly between the brackish Baltic coasts and the freshwater Curonian lagoon (opposite some other studies);

• Three migratory patterns, seawater-residents, freshwater-residents and inter-habitat shifters, were identified from the Curonian Lagoon and Baltic coasts; no significant growth differences among migratory groups were found although such growth differences occur in other anguillid eels;

• Significantly larger the lengths-at-age between 4-7 years for stocked eels leads to hypothesis that the artificial restocking allows the energy savings due to non-migration, while naturally recruited eels have to allocate energy for long distance migration that stocked eels do not. After the arrival of naturally recruited eels in the Baltic Sea, any differences in length might be reduced by compensatory growth;

• It was found that the growth of the eels might be more enhanced in estuary and coastal waters than in freshwater lakes. In this study, it was further suggested that the productivity and longevity of the growing season, rather than the salinity, might play a more important role in growth of the eels because that of the eels in the nearly freshwater lagoon was higher than in freshwater lakes;

• The analysis of eel otolith samples provides the first confirmation that vaterite zones can exist in the aragonite otoliths of the European eel. The prevalence of otoliths with mosaic vaterite was found in nearly half of the eels examined. If mosaic vaterite is not distinguished from aragonite, the fish migratory history may be misidentified when otolith elemental signatures are used as biological tracers;

• Naturally recruited and restocked eels belong to different populations and differ genetically from each other; eel populations from different lakes can differ as well hypothetically depending on the stocked eel originating area (the area from which eels in glass eel stage were translocated; the distance between restocking and glass eel catch site are thousands kilometers usually);

• The study indicates that the Percid fish migration to brackish water is rather irregular than regular. Percids perform migrations to the Baltic Sea in later age, while juveniles stay in fresh water. However, to reveal the migratory history of Percids completely, further

• The results of the genetic studies on Percid fish populations is in accordance with the observed irregular Percid fish migrations revealed by microchemical analysis. The data of genetic studies do not support the hypothesis of two “migrating” and “non-migrating”

subpopulations existence in the Curonian Lagoon: according to the study results, Percid fish population in the Curonian Lagoon should be considered as a “single population”;

• The hypothesis of “migrating pikeperch” spawning grounds in the Northern part of the Lagoon was denied during the study. Field observations enable to conclude that pikeperch in the northern part of the Lagoon concentrate before their migration to the Sea awaiting favorable temperature conditions in the Baltic Sea;

• Percid fish populations in Lithuania and Latvia should be considered as different subpopulations due to observed genetic.

RECCOMENDATIONS FOR STUDIED FISH SPECIES MANAGEMENT:

• Eel stocks in both Lithuania and Latvia should be considered and accordingly managed as consisting of two differently originated populations: naturally recruited, which predominate in the coastal waters and restocked, which predominated in the inland lakes;

• Eel stock managers in Lithuania and Latvia should use precautionary approach and avoid mixing of natural stocks with restocked, i.e. should not stock water sites where natural recruits prevail using transported glass eels from other areas of the distribution range to avoid possible genetic over mixing of “local populations” with restocked eels;

• The abilities of restocked eels to contribute to reproduction (to reach spawning grounds and spawn successfully) is disputable; therefore stock protection should focus on naturally recruited eels primarily;

• Data obtained during the study concerning eel stock structure, recruitment timing, growth rate, maturation, abiotic and biotic effects on eel growth should be used preparing European eel management plans in Lithuania and Latvia; both countries are obligated by European Union to complete plans until the end of 2008;

• Perch and pikeperch stocks should be considered as one single stock and managed accordingly; the study failed to find two different “migrating” and “non-migrating”

subpopulations;

• The study denied hypothesis about “migrating” pikeperch spawning grounds in the northern part of the Curonian Lagoon and this area should be managed as pikeperch concentration area but not spawning ground; spawning grounds in the area of the Curonian Lagoon where found in Nemunas river delta only.

• Perch and pikeperch stocks between Lithuania and Latvia are isolated by means of distance and should be managed as separate stocks.

The collaborative research study between Lithuania, Latvia and Taiwan (ROC) contributed to