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Background and interpretation of the 'Marine Trophic Index' as a measure of biodiversity


Pauly, D and Watson, RA, Background and interpretation of the 'Marine Trophic Index' as a measure of biodiversity, Philosophical Transactions of the Royal Society B: Biological Sciences, 360, (1454) pp. 415-423. ISSN 0962-8436 (2005) [Refereed Article]

DOI: doi:10.1098/rstb.2004.1597


Since 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.

Item Details

Item Type:Refereed Article
Keywords:Ecosystem impact; Food webs; Overfishing; Predatory fishes; Trophic level; biodiversity; ecosystem approach; environmental indicator; index method; overfishing; trophic level; Pisces; animal; article; biodiversity; biological model; food chain
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Fisheries sciences
Research Field:Aquaculture and fisheries stock assessment
Objective Division:Animal Production and Animal Primary Products
Objective Group:Fisheries - wild caught
Objective Field:Wild caught fin fish (excl. tuna)
UTAS Author:Watson, RA (Professor Reginald Watson)
ID Code:84060
Year Published:2005
Web of Science® Times Cited:236
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2013-04-16
Last Modified:2013-04-16

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