Atlas of the maturity stages of Mediterranean fishery resources

This atlas stems from an experience on fish maturity staging carried out at the Mediterranean level. It aims to present sound approaches to maturity sampling for a wide range of Mediterranean species, based on an accurate and precise determination of the different maturity stages. It includes macroscopic photos of gonads belonging to the main species, and for some of them, a validation-based histological analysis is also presented. The main categories investigated in the atlas are bony fish, cartilaginous fish, both oviparous and viviparous, crustaceans and cephalopods. Maturity is one of the most relevant biological parameters used in stock assessment programmes. Indeed, the macroscopic stage of gonadal development is an essential feature in estimating the maturity ogive and spawning stock biomass. It is also useful for determining the spawning season of a species and for monitoring long-term changes in the spawning cycle, as well as for many other research needs related to the biology of fish. In current data collection programmes carried out in the Mediterranean which cover extensive samplings of maturity stages, some specific technical aspects have not always been taken into consideration, and collected data cannot reach the required precision levels. Also, the coding schemes in use and the uncertainty in the interpretation of particular stages can give rise to misinterpretations of the actual maturity stage leading to inaccurate spawning stock biomass estimations. Several stock assessments are therefore based on time-invariant maturity ogives and only partially cover the spatial distribution of the stocks. Hence, on several occasions, the need has been expressed to improve the identification of the macroscopic maturity stages through a standardization of operational procedures and terminology. Hence, one of the solutions for overcoming these problems was to develop an atlas of the macroscopic and histological maturity stages of the main species of commercial interest in the Mediterranean.