One of the main criteria for judging the status of an exploited fish population is the size of the spawning stock or spawning stock biomass (SSB). Maturity data are the basic information to estimate maturity ogives that allow the estimation of the SSB. Maturity ogives are estimated based on length/age stock structure and sex ratio. Traditionally, fish maturity has been determined macroscopically, based on morphological features of gonads both, testis and ovaries. Nevertheless, maturity ogives based on histological data give more accurate estimation of SSB, however this approach is not always feasible due to the cost, both in time and resources, of histological process. Because of these, several alternative maturity indices, easier and quicker estimated, are being developing. Usually, macroscopic maturity scales change not only among species but also between laboratories. The lack of common criteria makes comparison between labs studies difficult. International efforts to harmonize maturity staging criteria has been or are being carried out trough Workshops organization (WKMSHM-2007, WKMSCWHS-2007, Workshop on Gonadal Histology of Fishes-2009, Workshop on Maturity of Greenland halibut and redfish-2010, etc.), nevertheless, there is not a standard guide to coordinate different laboratories protocols. This chapter standardizes maturity staging criteria in order to create maturity scales bases on easily identifiable morphological features of gonads, both, testis and ovaries. Besides, different histological samples processing and treatments are presented as well as microscopic maturity scales for species that present different reproductive strategies (gonochoristics vs hermaphrodites; determinate vs indeterminate, synchronous vs asynchronous, etc.), for both sexes. On the other hand, alternative, indirect and accurate maturity classification methods based on somatic and biochemical indices are described. Finally, application of this information to estimate maturity ogives by different methods is also presented.

In Handbook of applied fisheries reproductive biology for stock and management