Dynamic catch-effort model for brown shrimp Farfantepenaeus californiensis(Holmes) from the Gulf of California, Mexico

We analyzed the catch and effort data for the brown shrimp (Farfantepenaeus californiensis) fishery over 22 years. We used a biomass dynamic model in a stochastic version to analyze the catch-per-unit effort of the trawl fish ery in the Gulf of California, Mexico. Two hypotheses were proposed: the fi rst (observation error) assumes that the catch-per-unit effort (CPUE) is me asured with error, while in the second (process error), the variability of the population is produced by factors not included in the model. The result s show that the hypothesis of the process error was accepted. In this case, the hypothesis of the process error recognizes several sources of perturba tion in the model. For example, changes in the size structure of the shrimp population, changes in the natural mortality, variations in the fecundity or recruitment, and changes in the environment. Evidence of the relation be tween the environment and the shrimp population is discussed, as is the pos sibility of proposing a biological hypothesis for the trends of the populat ion and the CPUE.