Influence of Capture Methods on Blood Characteristics and Mortality in the Rainbow Trout (Salmo gairdneri)

Blood characteristics and mortality were compared between rainbow trout which were captured by (1) angling with artificial lures, (2) electroshocking, and (3) seining. The hemoglobin concentration, erythrocyte sizes, plasma protein concentrations, and plasma protein fractions varied according to the method of capture. Mortality was negligible in the shocked and seined lots, but was above 85% in the hooked fish group. Mortality was delayed and the symptoms suggest progressive shock. Definite differences in behavior were noticed in the postcapture fish and included prolonged fasting (shocked and hooked fish), hyperexcitability (shocked fish), and lethargy (hooked fish). The authors believe that presently used methods of capturing and handling fish should be re-evaluated, particularly if the fish are to be used in toxicological or management studies.