Fisheries oceanographers Tien-Shui Tsou and Jeremy S. Collie at the University of Rhode Islands Graduate School of Oceanography are estimating fishing and predation mortalities by year and age group of predator and prey species on Georges Bank using Multispecies Virtual Population Analysis (MSVPA).
This method of analysis integrates virtual population analysis with data on the food consumption rates and diet composition of the major predator and prey species.
In a recent study, reported in the Canadian Journal of Fisheries and Aquatic Sciences, Tsou and Collie tested the reliability of MSVPA by applying the method to the highly productive and long exploited Georges Bank fish community. Over the past several decades the structure of the Georges Bank fish community has changed significantly, with increases in sharks, rays, herring, and mackerel and decreases in groundfish and flounders.
As part of NOAAs Coastal Ocean Program, Georges Bank Predation Study, Tsou and Collie constructed a nine-species MSVPA of the fish community on Georges Bank to investigate the feeding dynamics between predator and prey. The species included cod, haddock, herring, yellowtail flounder, silver hake, mackerel, sandlance, spiny dogfish, and winter skate. To construct their model, they used catch and diet data gathered by the Northeast Fisheries Science Center from 1978-1992. The diet data come from thousands of stomach samples from marine fish that have been collected along the northeast coast of North America.
The results of the MSVPA agree with previous conclusions that predation is a dominant source of mortality in the Georges Bank fish community. Cod and silver hake were the most important predators, but have been replaced by sharks and rays as the dominant fish eaters in more recent years. The predator diet composition shifted to herring and mackerel as these prey species became more abundant in the late 1990s, but the predation pressure was insuffic
Contact: Lisa Cugini
University of Rhode Island