Modeling the Effect of Fisher Behavior on CPUE in the Gulf of Mexico Reef Fish Fishery

In order to understand the effect of fishing on fish populations, it is necessary to not only study the population dynamics of the fish, but also the population dynamics of the fishers themselves.  A spatially explicit individual-based model of the West Florida Shelf in the Gulf of Mexico is presented which tests the performance of estimation methods for relative abundance when fisher behavior impacts catch per unit of effort.  Fisher behaviors were parameterized using discrete choice models developed from logbook data and fisherman surveys for handline and longline gear.  The spatial distribution of five commercially important reef fish species was estimated by combining large-scale fishery-dependent catch per unit of fishing effort from logbook data, with small scale fishery-independent video survey observation:  gag grouper (Mycteroperca microlepis), mutton snapper (Lutjanus analis ), red grouper (Epinephelus morio), red snapper (Lutjanus campechanus), and vermilion snapper (Rhomboplites aurorubens).  A biased random walk model with homing was incorporated to represent ontogenetic movement of reef fish from inshore nursery habitat occupied by juveniles to offshore reef habitat inhabited by adults in order to represent a spatially explicit stable age structure.  Simulation scenario results quantify the magnitude and direction of bias from fisher behavior that contributes to relative abundance estimation.  Alternative ways to treat the catch and effort observations through incorporating information from the fishing fleet into abundance estimation will be discussed.