The trophic fingerprint of marine fisheries

Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and...

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Bibliographic Details
Published in:	Nature (London) Vol. 468; no. 7322; pp. 431 - 435
Main Authors:	Branch, Trevor A, Watson, Reg, Fulton, Elizabeth A, Jennings, Simon, McGilliard, Carey R, Pablico, Grace T, Ricard, Daniel, Tracey, Sean R
Format:	Journal Article
Language:	English
Published:	London Nature Publishing Group UK 18-11-2010 Nature Publishing Group
Subjects:	704/158/2445 704/158/2446 704/158/670 Animal and plant ecology Animal, plant and microbial ecology Animals Applied ecology Aquatic Organisms - isolation & purification Aquatic Organisms - metabolism Biodiversity Biological and medical sciences Biological diversity Biomass Commercial fishing Databases, Factual Ecosystem Ecosystems Environmental changes Environmental Policy Estimates Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.) Fisheries Fisheries surveys Fishes - metabolism Fishing Food Chain Food chains Food webs Fundamental and applied biological sciences. Psychology Human Activities Humanities and Social Sciences Invertebrates - metabolism letter Marine ecosystems Marine fish Models, Biological multidisciplinary Plankton Plankton - metabolism Predators Science Science (multidisciplinary) Sea water ecosystems Synecology Threatened species Trawling Trends Trophic levels United States Marine environment Trophic chain Aquatic environment Fishery Trophic level Biological indicator Fishing Biodiversity
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Summary:	Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse ("fishing down marine food webs") and when low-trophic-level fisheries expand ("fishing through marine food webs"). The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0028-0836 1476-4687
DOI:	10.1038/nature09528