ESTIMATION OF SEA TROUT (Salmo trutta m. trutta) PRODUCTION IN A SMALL POMERANIAN RIVER

Abstract

Abundance of one year old sea trout smolt in the Gnilna River was assessed by means of two methods. One method involved estimation of the difference between the fish abundance before smolt emigration and that after the emigration. The second method was based on a single estimate of abundance (before emigration) and on the bimodality of fish length distribution. The resulting data were compared with catches of smolt in traps. The two methods overestimated smolt abundance. The second one was less time consuming and less biased than the other one. Its accuracy depended on precision of the estimation of fish abundances in the river.