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 possible 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 stomachs 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 evidence 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.

Trawling disturbance effects on the trophic ecology of two co-generic Astropectinid species

“…In relation to trawl intensity the two species showed a highly opportunistic feeding strategy and co-occurred at all sites by showing differences in their diet preferences (Ribi et al, 1977) and shifting in size-frequency distributions. Our results support the hypothesis that bottom trawling affects the fitness of benthivorous organisms by altering the food availability and generating a positive response of facultative scavengers to carrion (Demestre et al, 2000;Link, 2004;Dell et al, 2013;Johnson et al, 2015).…”

“…Here, we tested the hypothesis that bottom trawling affects the diet of benthivorous organisms by altering food availability and generating a positive response of facultative scavengers to carrion. Benthic scavengers feeding on the benthic community that results from the effects of trawling might represent costeffective samplers, hence diet studies may provide insights into the trophic consequences of such community changes for other components of the ecosystem (Link, 2004;Dell et al, 2013;Johnson et al, 2015).…”

Trophic ecology of the gopher rockfish Sebastes carnatus inside and outside of central California marine protected areas

“…Subtidal surveys conducted by the Partnership for Interdisciplinary Studies of Coastal Oceans in the general geographic regions included in this study documented larger organisms like bat stars and anemones but not most species consumed by the gopher rockfish. Based on the assumption that a generalist predator will show little selectivity in feeding, the stomach contents of generalist feeders can be used as a means to sample the marine environment (Frid & Hall 1999, Link 2004. The large number of prey types encountered in this study supports the assumption that gopher rockfish are not highly discriminate feeders.…”

It takes guts to locate elusive crustacean prey

“…a fish biosampler) has been an effective tool for surveying prey distribution. This technique has been applied to a diverse array of prey species, from isopods (Rachlin & Warkentine 1997) to ctenophores (Link & Ford 2006), and has been used to measure benthic species richness (Frid & Hall 1999, Link 2004. Further, this approach has been used to sample capelin through cod diet analysis (Fahrig et al 1993) and to detect effects of mobile bottom fishing gear (Smith et al 2013).…”