On the interdependence of sequential fisheries: The brown shrimp, Farfantepenaeus aztecus, fisheries in the northwestern Gulf of Mexico

This contribution deals: with some aspects of sequential shrimp fisheries, particularly the relation between survival after catch in inshore waters an d recruitment to the offshore fishery. This relation is described for the b rown shrimp, Farfantepenaeus aztecus, in the northwestern Gulf of Mexico, u sing a modified catch equation, the solution of which is approached using c atch data, with a delay between catch-at-migration time (inshore waters) an d recruitment to the offshore fishery. Recruitment decreases as a logarithm ic function of catch, the form of which is defined by fishing mortality and migration rate. For a period of 8 years of monthly data, the explained var iance of recruitment at the offshore fishery was more than 60%, but fur the average pattern it increases to 80%. The main concept behind this model is to identify a desirable survival level in inshore waters after catch, that permits a number of recruits to the offshore fishery to maintain stable yi elds. The model described above was unable to be directly used for manageme nt purposes, because of a large variance along the catch axis. The second d erivative of the model was used to represent increments in survival late (t o offshore fishery) as a function of inshore catch. Several tendencies were explored, but inshore catch that stabilizes survival is tentatively sugges ted as the more appropriate to be used as a criterion fur management. In pr actice, the desired survival level can be approached by monitoring fishing in inshore waters.