Evaluation of lethal and nonlethal assessment methods of muscle fat content in European eel (Anguilla anguilla)

Abstract

Individual fat reserves are considered a key factor for the reproductive fitness of the endangered European eel (Anguilla anguilla). In contrast with most established standards, microwave measurements enable the determination of fat contents without sacrificing individual fish, offering a broad range of ecological applications. To test the reliability of nonlethal assessment methods of the muscle fat content in eels, the performance of microwave measurements was compared with the prevailing standard of measuring fat in a distinct subsample of muscle tissue by solvent extraction. Results indicate that either method is prone to error due to physiological and morphological changes during the sexual maturation of eels. Since microwave measurements were systematically affected by life stage and body length, it was possible to calibrate the method accordingly, putting it at least on par with the prevailing standard and further facilitating its use for scientific purposes.