A New Muscle Biopsy Technique for Sex and Sexual Maturity Determination in Large Pelagic Fishes

In many fisheries, fish are either landed already gutted or the value of the flesh prohibits ventral opening and the determination of sex and sexual maturation. The objective of the present study was to provide new molecular endocrinological techniques to make this possible in order to assist stock assessment and management. A muscle biopsy punch which can be used in the field or at the market to obtain muscle biopsy samples from live or dead bluefin tuna (Thunnus thynnus) or swordfish (Xiphias gladius) has been developed. These samples can then be assayed using standard ELISA methods for sex hormones and vitellogenin. A correlation was found between plasma and muscle sample levels for steroids in tuna. The future role of a muscle biopsy is discussed together with “molecular markers”.