RECENT CHANGES IN THE GROWTH AND FEEDING OF BALTIC HERRING AND SPRAT IN THE NORTHEASTERN BALTIC SEA

The mean weight at age ofj Baltic herring remained rather stable from the 1940 s to the 19605.Since the second half of the 19705, the mean weight of herring began to increase in most regions of the Baltic Sea.High values of the mean weight and length in all age groups were observed until the mid-1980s; then a sudden drop in all growth parameters followed.Since the 1990 s a decrease can be observed in the growth of Baltic sprat.The results of feeding investigations conducted in 1982-92 show changes in the prey composition and an increase in the proportion of fish with empty stomachs.These changes, probably induced by hydrological conditions prevailing since the mid-eighties, may at least partly be responsible for drastic alterations in fish growth.Preliminary calculations show that the Guli of Finland herring and sprat stocks without the 0-group consume 15.2)X10° t of zooplankton and 3.9X10° t of nektobenthic organisms.