Spawning Migration and Population Condition of Twaite Shad (Alosa fallax, Lacépède 1803) in Lithuania

Abstract

Basic biological information on a twaite shad population (Alosa fallax, Lacépède 1803) is presented based on a 2-year study involving 273 adult and 18 juvenile specimens. The fish were caught in the Curonian Lagoon and the coastal zone of the Baltic Sea. At the end of July, 2004, the intensive and record late spawning of twaite shad was observed. At the end of May, 2005, the beginning of spawning migration of this fish was noted. Twaite shad was one of the key fish species caught with 38-50 mm mesh size nets at the material sampling location. The fish catch per unit of effort (CPUE) in different mesh size gill nets fluctuated from 2.7 to 32 individuals. In the spawning shoal male individuals were predominant. The standard body length of twaite shad females varied from 322 to 430 mm. The standard body length of males varied from 280 to 390 mm. Twaite shad ranged from 2+ to 9+ years, but the majority were from 4+ to 7+ years old. Females exhibited higher condition factor (CF) and gonadosomatic index (GSI) values than males. Young fish were caught at 7 stations out of 17, although their abundance was not high. Besides the twaite shad, there were juveniles of 18 more fish species caught in the coastal zone.