Reproductive failure in Baltic sea trout (Salmo trutta) compared with the M74 syndrome in Baltic salmon (Salmo salar)

The results from an investigation performed at the Ar Laboratory, Gotland, Sweden during the period 1994-1998 revealed no reproduction disturbances in brown trout similar to those found in Atlantic salmon from the Baltic sea. Female-specific mortality of yolk-sac fry never exceeded 11%. The mean tot al thiamine concentration in yolk-sac fry (5.5 +/- 1.4 nmol g(-1); n = 20) well exceeds the threshold limit interval reported from Baltic salmon fry a ffected by M74 (0.31-0.34 nmol g(-1)). Analyses of astaxanthin in eyed eggs showed levels above values reported from Baltic salmon eggs that later dev eloped into fry with M74. However, the levels are lower than the values rep orted from the salmon population of Lake Vanern and from the rivers Lagan a nd Gotaalv on the Swedish west coast. Total carotenoid levels (mg carotenoi d kg(-1)) in eggs from Gotland spawners decreased significantly with female size. Baltic sea trout from the Swedish river Ava have experienced high yo lk-sac fry mortality rates with the peak mortality in 1992 (35 +/- 20%). In addition, reproduction disturbances in sea trout are reported from 3 Swedi sh rivers along the Baltic coast (Dalalven, Indalsalven, and Umealven). Dif ferences in life histories of sea trout and salmon from the Baltic Sea are discussed in relation to the lower incidence of mortality in yolk-sac fry o f Baltic sea trout.