The significance and prediction of predation in marine fisheries

Predation is a pervasive but ephemeral feature of marine fisheries. Losses to predation can exceed losses to fisheries, yet is is often assumed fishin g mortality alone is responsible for variation in fish survival. While it m ay be sufficient to forget predation in short-term prediction and managemen t, this will not further longer-term prediction and management. The predati on experienced by a population is influenced by environmental and biologica l factors that vary spatially, seasonally, annually, and with the abundance of itself, other prey species, and the predator species. Predation call di rectly regulate prey numbers and indirectly regulate their survival via hab itat availability, individual growth, and trophic structure. Despite predat ion's pervasity, its complexity and variability complicate its prediction. Models of predation have shown assumptions made in single-species models to be incorrect, but numerical prediction may be reliable for only the simple st symmetrical predator-prey interactions, where ontogenetic changes in pre dator diet and prey vulnerability have been accounted for. Knowledge of the effects of predation in marine fisheries will be furthered by an ongoing c ommitment to test and explore the properties of managed fisheries, while pr eserving, as necessary, the productivity and buffering capacity of the natu ral system. (C) 1998 International Council for the Exploration of the Sea.