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Background and interpretation of the 'Marine Trophic Index' as a measure of biodiversity
journal contribution
posted on 2023-05-17, 17:05 authored by Pauly, D, Reginald WatsonReginald WatsonSince the demonstration, in 1998, of the phenomenon now widely known as 'fishing down marine food webs', and the publication of a critical rejoinder by Food and Agricultural Organization (FAO) staff, a number of studies have been conducted in different parts of the world, based on more detailed data than the global FAO fisheries statistics originally used, which established the validity and ubiquity of this phenomenon. In this contribution, we briefly review how, rather than being an artefact of biased data, this phenomenon was in fact largely masked by such data, and is in fact more widespread than was initially anticipated. This is made visible here by comparing two global maps of trophic level (TL) changes from the early 1950s to the present. The first presents the 50-year difference of the grand mean TL values originally used to demonstrate the fishing down effect, while the second is based on means above a cut-off TL (here set at 3.25), thus eliminating the highly variable and abundant small pelagic fishes caught throughout the world. Based on this, we suggest that using mean TL as 'Marine Trophic Index' (MTI), as endorsed by the Convention on Biological Diversity, always be done with an explicitly stated cut-off TL (i.e. cutMTI), chosen (as is the case with our proposed value of 3.25) to emphasize changes in the relative abundance of the more threatened, high-TL fishes. We also point out the need to improve the taxonomic resolution, completeness and accuracy of the national and international fisheries catch data series upon which the cutMTI is to be based. © 2005 The Royal Society.
History
Publication title
Philosophical Transactions of the Royal Society B: Biological SciencesVolume
360Issue
1454Pagination
415-423ISSN
0962-8436Department/School
Institute for Marine and Antarctic StudiesPublisher
The Royal Society PublishingPlace of publication
United KingdomRepository Status
- Restricted
Socio-economic Objectives
Wild caught fin fish (excl. tuna)Usage metrics
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