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 fishing mortality alone is responsible for variation in fish survival. While it may be sufficient to forget predation in short-term prediction and management, this will not further longer-term prediction and management. The predation experienced by a population is influenced by environmental and biological factors that vary spatially, seasonally, annually, and with the abundance of itself, other prey species, and the predator species. Predation call directly regulate prey numbers and indirectly regulate their survival via habitat availability, individual growth, and trophic structure. Despite predation'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 simplest symmetrical predator-prey interactions, where ontogenetic changes in predator diet and prey vulnerability have been accounted for. Knowledge of the effects of predation in marine fisheries will be furthered by an ongoing commitment to test and explore the properties of managed fisheries, while preserving, as necessary, the productivity and buffering capacity of the natural system. (C) 1998 International Council for the Exploration of the Sea.