Application of a stage-specific matrix model and length-cohort based analysis to assess the anchovy fishery in Catalan coastal waters (NW Mediterranean Sea)

This study describes trends in anchovy (Engraulis encrasicolus) population biomass in Catalan coastal waters of the northwestern Mediterranean Sea and relates empirical data to the demographic models in order to understand its dynamics and shed some light for future management of the stock. Classical fisheries models (length-cohort analysis and yield-per-recruit analysis) are applied together with the stage-specific Lefkovitch matrix model to detect population growth. Estimates of rates of growth, mortality, and fecundity were assembled for each biological stage. The results confirm and quantify the importance of early life stages on population trends and indicate how sensitive the overall biomass is to rate variations. Both approaches an consistent in indicating stable biomass conditions at the current exploitation level, even though environmental variability is not considered, and might cause changes. In view of the fishermen's effort reduction, a 10% fishing mortality decrease on the fishery was also examined in a dynamic model to forecast the yields, simulating different stock-recruitment patterns. (C) 1997 Elsevier Science B.V.