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  • Author: Rafał Bernaś x
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Piotr Dębowski, Rafał Bernaś, Michał Skóra and Jacek Morzuch

Abstract

The European eel, Anguilla anguilla L., is an endangered species. Barriers to its downstream spawning migration are one of the greatest threats this species faces. There are hundreds of hydroelectric plants (HEP) on rivers in Poland (> 600), and thousands throughout Europe. Eel that pass through HEP turbines as they migrate downstream suffer high mortality, but this depends mainly on local and technical conditions. Silver eel mortality was estimated and the possibility of the fish bypassing the turbines was studied between November 2013 and June 2014 at a typical HEP in northern Poland. Two telemetry methods were used with 49 eel: passive integrated transponder (PIT) system and acoustic telemetry. Fifty five percent of eel migrated downstream in fall 2013, soon after their release, and 45% migrated the next spring. The eel did not use the fish passes designed for upstream migration; thus, they were forced to go through the turbines, which resulted in 55% mortality. HEPs cause interruptions and delays in eel spawning migrations and are responsible for high eel mortality. This can make implementing an eel restitution plan difficult or even impossible in river systems with many barriers.

Open access

Anna Wąs-Barcz, Rafał Bernaś and Roman Wenne

Abstract

Many countries in the Baltic Sea basin have initiated enhancement programs for Baltic migratory sea trout, Salmo trutta L., to compensate for losses stemming from anthropogenic pressure that has resulted in the declining population abundance of this species. Regular stock enhancement has been conducted in Poland since the 1960s. Currently, over one million sea trout smolts are released into Polish rivers annually. In most Baltic countries, including Poland, stock enhancement depends on hatcheries producing material using spawners caught in native rivers. However, increasing difficulty obtaining spawners in recent years in Poland has meant that stock enhancement performed in the Vistula has been done largely with material obtained from broodstocks. Simultaneously, there is a lack of information regarding the proportion of wild and cultured sea trout in this river basin. This paper is a review of methods applied to identify individuals from natural and artificial sea trout spawning in rivers, and it proposes using genetic techniques as an alternative to traditional marking methods. A set of 13 microsatellite loci are proposed that are characterized by high selectivity. Using negative controls while simulating the assignment of parental pairs revealed that the number of loci in the set was highly significant and should not be reduced. This method could be useful in the proposed assessment of the proportions of wild and cultured fish in Polish rivers.