The trophic role of lutjanid fish and impacts of their fisheries in two ecosystems in the Gulf of Mexico

The trophic role of snappers was evaluated on the continental shelves of th e south-western Gulf of Mexico and the Yucatan in the south-eastern Gulf of Mexico. Mass-balanced, steady-state trophic models of the two ecosystems w ere constructed with Ecopath and perturbations were simulated in the ecosys tems with Ecosim by increasing fishing mortality. Impacts were measured by changes in biomass of snappers and other groups, and in some indices of sta bility: persistence, recovery time and resilience. The snapper populations differed between ecosystems. The western Gulf of Mexico system appeared mor e complex and more stable than the Continental Shelf of Yucatan. Although o verall stability indices between ecosystem suggested a similar structure an d function, there were clear differences at a group level. Correlation of s tability attributes between groups suggested differences in the role of sna ppers between the ecosystems suggesting that each stock should be managed i ndividually. (C) 1998 The Fisheries Society of the British Isles.