Assessing the effects of internal and external acoustic tagging methods on European flounder Platichthys flesus

Fish telemetry studies give unique information about fish movements (migrations), but there are still several methodological constraints. A critical step is the choice of an appropriate tag and tagging method, essential to guaranteeing that the tagged fish is representative of the general wild population. The effects of two tagging methods with acoustic transmitters on the behavior, survival, condition, and growth of the European flounder Platichthys flesus (L.) were evaluated in tank experiments. Two 33-day assays were conducted: one with adult flounder to test intracoelomic (internal) and external tagging with Vemco V7-2 L dummy tags, and a second assay with juveniles using only external tags. Intracoelomic implantation resulted in very low survival rate (10%), fish lethargy, and a lack of response to food. External tagging did not affect behavior but had negative effects on the final condition of adult flounder, and on the specific growth rates (SGR) of smaller-sized fish. The external tagging method is the most appropriate for P. flesus because of the technique's simplicity, expedience, and fewer negative effects upon the fish.