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School-based indicators of tuna populations status


Dell, J and Hobday, AJ, School-based indicators of tuna populations status, I C E S Journal of Marine Science, 65, (4) pp. 612-622. ISSN 1054-3139 (2008) [Refereed Article]

DOI: doi:10.1093/icesjms/fsn032


Theory and limited observation suggest that fish schools consist of more individuals of similar size when populations are large than when they are small. The hypothesis that population size might be indicated by school structure is tested for southern bluefin tuna (SBT), a commercially important large pelagic species, which has undergone an estimated 60% reduction in juvenile biomass since 1960. Fish size data are used to determine whether there have been changes in schooling behaviour that can be used as simple indicators of abundance. During tagging studies, juvenile SBT are removed sequentially from a school, measured, tagged, and released. These sequential size measurements are used here to describe school composition from different years in two locations using simple school metrics (including mean fish size, variance in size, and mean difference in size between sequential fish). Trends were significant in most metrics over the 40-year period analysed, and were inversely related to independent estimates of population size. Simple school metrics are cost-efficient and easily interpreted by stakeholders. Monitoring population trends in near real time through school composition metrics may indicate further decline or recovery of SBT and, therefore, assist future management of tuna and other schooling species. © 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.

Item Details

Item Type:Refereed Article
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Fisheries sciences
Research Field:Fisheries sciences not elsewhere classified
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Marine biodiversity
UTAS Author:Dell, J (Dr James Dell)
ID Code:51677
Year Published:2008
Web of Science® Times Cited:3
Deposited By:TAFI - Zoology
Deposited On:2008-04-18
Last Modified:2011-10-07

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