Predatory reactions of juvenile stages of sea trout (Salmo trutta trutta L., 1758) fed with three feeding regimens

Restocking is used in rivers to restore fish populations. The biological value of stocking material derived from hatcheries is low, which is reflected in low survival rate in natural environment after stocking. For this reason, in pre-rearing, attention is increasingly paid to minimize the undesired hatchery-rearing effects, which greatly reduces the biological value. The quality of stocking material can be improved by introducing live food to the diet. The aim of the study was an attempt to determine the biological quality of trout larvae reared in three feeding regimens by determining the predatory behavior. The experiment started with a 30-day rearing of fish in three feeding variants: starter feed and algae, starter feed, and live brine shrimp larvae. Best weight and length gain of the fish and the survival rate were recorded in the group of fish fed exclusively Nutra HP 0.3 starter feed (Skretting). Pre-reared larvae of sea trout from three feeding variants were released in reservoirs, in which ide Leuciscus idus larvae were introduced as live food. It was observed that sea trouts most effectively caught their prey in a variant, in which sea trout larvae had been previously fed brine shrimp larvae, Artemia sp. The results indicate that the type of first food can model the predatory behavior of juvenile stages of sea trout.