Changes in Biological Indices and Abundance of Salmon, Sea Trout, Smelt, Vimba and Twaite Shad in the Coastal Zone of the Baltic Sea and the Curonian Lagoon at the Beginning of Spawning Migration

Abstract

Investigations of the abundance and biological indices of salmon and sea trout were carried out in 1990–2001 while those of smelt, vimba and twaite shad were performed in 1998–2002. Pollution of rivers and the lagoon having abated and the Strait of Klaipėda having been deepened, stocks of the majority of migratory fish have increased in recent years. Stocks of salmon and sea trout are much more abundant at present than they used to be 15–20 years ago. The article presents the characterization of meristic, plastic and biological features of these fishes caught over past years and submits proposals concerning the protection and enlargement of salmon and sea trout stocks. Although commercial catches of vimba have considerably grown up at present, their age structure remains stable. The article also presents changes in biological and biochemical indices in smelt during spawning migration and spawning. The abundance of twaite shad in the Baltic Sea and the Curonian Lagoon has been steadily increasing since 199...