On spring and summer spawning of Baltic sprat in the years with different hydrological regimes

Abstract

The size-age structure of the spawning stock, the spawning efficiency, the regularities of egg and larval distribution and the conditions of reproduction affecting sprat (Sprattus sprattus balticus) year-class abundance are considered during three years (1974, 1975 and 1977). Two groups of sprat larvae and fry were determined: The spring (of larger size) and summer (small) larvae. The difference of larval sizes in modal groups was 30 mm. The spring generation, the area of which coincides with the area of cod in winter-spring period, is subjected to a greater influence of predators than the summer one.