Comparing Macroscopic and Quantitative Histological Methods to Determine Sexual Maturity in the Female European Plaice
Résumé
To implement regulations in fisheries, like the minimum catch size for a species, data on the species' biological parameters must be collected and analyzed. Among these parameters, sexual maturity of the fish is evaluated. Multiple methods exist, and in this paper we used the macroscopic method (visual appreciation of the sexual organ to classify the fish into a maturity phase) and the stereological method (identifying and counting cells inside the fish's sexual organs to determine the maturity phase). The methods put forward try to minimize the subjectivity brought on by the human agent that will determine the maturity phase, through the implementation of guidelines and calibration exercises. Beyond lowering the human assessment bias, this article also shows that the macroscopic method, used to collect data that will later be exploited to set up fishery regulations, accurately determines the sexual maturity of female plaice only 40.4% of the time. This leads to estimations of size at first maturity of 28.6 cm for the macroscopic method compared to 20.6 cm when using stereology, differences in sizes that could have a major impact when setting up fishery regulations.