The application of yield-per-recruit models to two South African sparid reef species, with special consideration to sex change

Yield-per-recruit models were applied to Chrysoblephus laticeps and Chrysoblephus cristiceps, both of which are important to the line-fishery industry in South Africa. Sex change and slow growth were investigated, particularly with respect to the ratio of males to the total number of mature fish in the population. Predictions based on the yield-per-recruit and spawner biomass-per-recruit models were viewed with caution owing to the rapid decline in the number of survivors past the age of recruitment, and their failure to take into account the effects of sex change on the reproductive potential of the population. Model predictions correlated well with observations that indicated a relationship between population structure and the level of exploitation. Considering the options for the management of these and similar reef fishes, the tactic of protection through marine reserves is supported.