PARENT SESSION
Oral Session #12: Aquatic Ecology: Marine.
Presiding: R. Lewison
Monday, August 5. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
Pelagic marine food web responses to fisheries management scenarios: a modeling exercise.
Hinke, Jefferson*,1, Kaplan, Isaac1, Kitchell, James1, Watters, George2, Olson, Robert3, 1 University of Wisconsin-Madison, Madison, WI2 Pacific Fisheries Environmental Laboratory, Pacific Grove, CA3 Scripps Institution of Oceanography, La Jolla, CA
ABSTRACT- We used the biomass dynamics modeling tool Ecopath with Ecosim to examine alternative fishing scenarios in two Pacific Ocean ecosystems. We considered scenarios for two cases that are motivated by concerns about the effects of overfishing in an ecosystem context: the elimination of the use of fish aggregating devices in the Eastern Tropical Pacific and the 1992 United Nations ban of pelagic driftnet fishing in the Central North Pacific. In both cases, a suite of non-target species occupying upper trophic levels are caught and discarded in the process of fishing for tunas. Simulations revealed that the general food webs configurations and catch compositions are robust to changes in fishery management actions. This stability persists even in cases where target species are depleted by or released from fishing pressures. In contrast, fishing mortality rates of both target and bycatch species, such as tunas, sharks, and sea turtles, are highly sensitive to changes in fishing effort, often changing by 20% - 50%. All fishery yields respond to changes in fishery practices demonstrating a high degree of fishery interaction mediated by the overlap of their supporting food webs. Climate forcing tends to exacerbate the magnitude of response to these scenarios, particularly for fisheries that target lower trophic levels.
KEY WORDS: Pacific, fishery, food web