Seeking biogeochemical signatures of fish harvesting in the recent sediment record

Abstract:

Fish removal was the earliest major human influence on the marine environment and global fishing effort has increased by orders of magnitude since its ancient origins, depleting predatory fish biomass by as much as 90% (Myers and Worm, 2003). It stands to reason that any impact this may have had on ocean biogeochemistry could have been preserved in existing high-resolution palaeoceanographic records. A severe depletion of upper trophic levels may result in a top-down ecological regime shift, manifesting in the form of trophic cascades and alterations to nutrient cycling and carbon export. Changes of this nature might be recorded in the sedimentary record through proxies such as fish remains, total organic carbon, ¹⁵N, and microfossil assemblages. However, these high-resolution proxies are more typically interpreted as reflecting climatic or oceanographic changes. This project searches for sedimentary signals of fish harvesting by compiling existing paleoceanographic data and comparing it to historical and archaeological records of ecosystem exploitation. Hypotheses of potential sedimentary signatures and methods of analysis will be discussed and results from case studies such as the Peruvian Upwelling Zone, North Sea, and Scotian Shelf will be presented. Identifying a sedimentary signature of fish harvesting will clarify interpretations of recent palaeoceanographic proxies and help define the role that fish can play in biogeochemical dynamics. This will aid in parameterizing upper trophic levels in ocean biogeochemical models and establishing pre-human baselines for ecosystem-based fisheries management.

References:

Myers, R. A., and B. Worm (2003), Rapid worldwide depletion of predatory fish communities., Nature, 423(6937), 280–3, doi:10.1038/nature01610.