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Size-based indicators show depth-dependent change over time in the deep sea


Mindel, BL and Neat, FC and Webb, TJ and Blanchard, JL, Size-based indicators show depth-dependent change over time in the deep sea, ICES Journal of Marine Science, 75, (1) pp. 113-121. ISSN 1054-3139 (2018) [Refereed Article]

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Copyright Statement

Copyright International Council for the Exploration of the Sea 2017. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.1093/icesjms/fsx110


Size-based indicators are well established as a management tool in shelf seas as they respond to changes in fishing pressure and describe important aspects of community function. In the deep sea, however, vital rates are much slower and body size relationships vary with depth, making it less clear how size-based indicators can be applied and whether they are appropriate for detecting changes through time. The deep-sea fish stocks of the North Atlantic underwent a period of exploitation followed by management and conservation action that relieved this pressure. We used data from a deep-water bottom trawl survey in the Rockall Trough, at depths of 3002000 m, to test whether size-based indicators changed over a 16-year period, during which fishing pressure decreased. We applied four indicators to these data: mean body length, mean maximum length, large fish indicator (LFI), and the slope of the biomass spectrum. Patterns were analysed within four different depth bands. The LFI and slope of the biomass spectrum showed positive change over time, suggesting recovery from fishing pressure. This response was generally most apparent in the shallowest depth band, where most fishing activity has been distributed. Values of the LFI were much higher overall than in shelf seas, so the same reference points cannot be applied to all marine ecosystems. These findings imply that size-based indicators can be usefully applied to the deep sea and that they potentially track changes in fishing pressure in the medium term.

Item Details

Item Type:Refereed Article
Keywords:size-based indicators, deep sea, fish communities, body size, demersal fish, deep-sea fishing, size structure
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Community ecology (excl. invasive species ecology)
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Assessment and management of Antarctic and Southern Ocean ecosystems
UTAS Author:Blanchard, JL (Professor Julia Blanchard)
ID Code:120917
Year Published:2018 (online first 2017)
Web of Science® Times Cited:7
Deposited By:Ecology and Biodiversity
Deposited On:2017-09-01
Last Modified:2022-07-01
Downloads:138 View Download Statistics

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