Fisheries in large marine ecosystems: Descriptions and diagnoses

We present a rationale for the description and diagnosis of fisheries at the level of Large Marine Ecosystems (LMEs), which is relatively new, and encompasses a series of concepts and indicators different from those typically used to describe fisheries at the stock level. We then document how catch data, which are usually available on a smaller scale, are mapped by the Sea Around Us Project (see www.seaaroundus.org) on a worldwide grid of half-degree lat.-long. cells. The time series of catches thus obtained for over 180,000 half-degree cells can be regrouped on any larger scale, here that of LMEs. This yields catch time series by species (groups) and LME, which began in 1950 when the FAO started collecting global fisheries statistics, and ends in 2004 with the last update of these datasets. The catch data by species, multiplied by ex-vessel price data and then summed, yield the value of the fishery for each LME, here presented as time series by higher (i.e., commercial) groups. Also, these catch data can be used to evaluate the primary production required (PPR) to sustain fisheries catches. PPR, when related to observed primary production, provides another index for assessing the impact of the countries fishing in LMEs. The mean trophic level of species caught by fisheries (or ‘Marine Trophic Index’) is also used, in conjunction with a related indicator, the Fishing-in-Balance Index (FiB), to assess changes in the species composition of the fisheries in LMEs. Also, newly conceived ‘Stock-Catch Status Plots’ are presented which document graphically, for each LME, both the increase in the number of stocks that moved from the fully exploited to the overexploited and collapsed stages, and the relative biomass of fish extracted from stocks in these various stages. Finally, original time series of estimated catch data are presented for the six LMEs of the coast of North Siberia, Arctic Alaska and Arctic Canada (all entirely contained within FAO Statistical Area 18), for which even crude catch estimates were previously unavailable. Altogether these descriptors of fisheries and ecosystem states over the last 50+ years allow a diagnosis of the fisheries of each LME, and inferences on global trends, as LMEs are the source of 80% of the global marine catch.

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