ABSTRACT
The Gulf of Mexico has been one of the last frontiers for fisheries in United States waters. But traditional Gulf fisheries, such as those for penaeid shrimp 2 and menhaden, have reached their harvesting limits, as have many newer fisheries, such as those for reef fish, coastal migratory pelagic fish, and large oceanic pelagics. Now fisheries are developing for the smaller, lesser known species, which appear to be very abundant but may be the food source sustaining many currently valuable fishery species, such as king and Spanish mackerel. Ecological approaches are needed to determine how the growing harvests of prey species will affect the populations and, consequently, the harvests of their predators.
In this report we quantify the consumption requirements of upper-trophic-level species in the Gulf of Mexico fisheries of both the United States and Mexico. We compare this to first approximations of the biomass of the middle-trophic-level species that are their prey. We estimate that the total consumption requirements are approximately 6.6 million metric tons (mmt) annually, whereas the biomass of potential prey species that we have quantified is approximately 8.4 metric tons (mt). This suggests that approximately 78% of the estimated standing biomass of prey species may be
consumed annually by fishery species. Fisheries currently catch approximately 15% of estimated prey biomass. This means that reproduction and growth rates of prey species (the production/biomass (P/B) ratio) must be at least 0.93 to maintain biomass stability.
The estimated total catch of prey species in both U.S. and Mexican waters of the Gulf of Mexico is 1.3 ramt, including discards. Menhaden, with an annual catch of 0.6 mmt in 1988, accounts for approximately one-half the catch of prey species. The by-catch of the shrimp fishery, most of which is discarded, is estimated at 0.5 mmt.
