Sex steroids of black scabbardfish, Aphanopus carbo, in relation to reproductive and migratory dynamics

Abstract Black scabbardfish, Aphanopus carbo, is a commercially important species that takes distant migrations throughout its life cycle. Sex steroids were measured by radioimmunoassay in the blood plasma of specimens caught off Madeira Archipelago and mainland Portugal to link this migratory path with reproductive Furthermore, pilot study using Mozambique tilapia (Oreochromis mossambicus) was designed evaluate effect sample freshness on steroid levels because black scabbardfish collected at separate times after caught. The changes T 11-KT concentrations between time extraction preservation did not statistically differ among different methods applied. Therefore, directly used subsequent data analyses. In females, E2 peaked late stage vitellogenesis. concentration significantly females each area. Clustering from all developing resulted separation two distinct groups, independently their geographical males, maturity stages. hepatosomatic index males relatively high. This may reflect mechanism for storing energy will later be consumed during migration spawning grounds. trend sex sexual maturation consistent morphological indicators shows evidence pattern hypothesised NE Atlantic.