Report of the

U.S. GLOBEC Georges Bank

Science Meeting

18 - 20 November 2003, Rhode Island

 


Cover Page

Acknowledgements

Introduction

Narrative

Presentation Abstracts

Poster Presentations

Appendix I: Agenda

Appendix II: List of Participants

Appendix III: List of Planned Publications


Production of Fish and Benthos on Georges Bank

Collie, J.1, A. DeLong1, and R. Bell1

1Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882

The objective of this study is to elucidate the benthic invertebrate and fish components of the Georges Bank energy budget. Available estimates of benthic production are on the order of 100 kcal m-2 yr-1, of which 60% is suspension feeders and 40% deposit feeders. However, there is considerable temporal and spatial variation, some of which is attributable to fishing activity. On gravel habitats on the northern edge of Georges Bank, benthic production is approximately four times higher in unfished areas than in fished areas. Bottom fishing therefore has indirect effects on energy flow, beyond the direct removals of target species. Preliminary estimates have been made of energy flow through the Georges Bank food web. The microbial loop is more important than was previously thought, with 80% of the production derived from recycled nitrogen. The upper components of the food web are supported by zooplankton and benthic production. Based on our preliminary estimates, the upper trophic levels do not appear to be food limited, especially during periods of depleted fish stocks. We have constructed biomass-dynamics models of the three trophic guilds of fish: benthivores, planktivores, and piscivores. Decadal shifts in the abundance of these trophic guilds can be simulated with bottom-up forcing and/or by altering the fishing mortality regime. These models will be refined to fit the actual biomass trajectories of the three fish guilds.

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