Using fish stomachs as samplers of the benthos: integrating long-term and broad scales

Abstract

Sampling benthic organisms in a synoptic manner is difficult, particularly at the scale of large marine ecosystems. Several known omnivorous and benthivorous fishes were evaluated as pos- sible samplers of the benthic community on the scale of the US northeast continental shelf ecosystem, collected from the early 1970s to 2001. Frequency of occurrence of organisms in the diet across time was examined as an index of relative abundance. Other prey and sampling caveats were accounted for by considering only those predators that met criteria such as adequate sample size, appropriate diet compositions, asymptotic stomach-prey curves, and relative constancy of all major prey groups comprising the diet. The geographic distribution of a suite of benthic organisms found in the stom- achs of predators was also examined. The benthic organisms focused on were ophiuroids, echinoids, holothuroideans, asteroids, octopods, stomatopods, cumaceans, pagurids, aphroditids, anthozoans, hydrozoans and caprellids. Of these 12 prey groups, only 3 showed a decline over time based on evi- dence from multiple predator stomachs. Most benthic organisms exhibited non-negative trends in an index of relative abundance, and 2 showed an increase over the time-series. Additionally, many of the organisms were widely distributed, with some concentrated more on Georges Bank and others more in the Gulf of Maine. Only 1 of 9 organisms showed a shift in distribution compared to studies from 50 yr earlier. I conclude that at broad spatial and temporal scales, the routine and systematic sampling of fish stomachs can be a useful indirect method for inferring information about benthic communities on continental shelves.