Defining the stock structures of key commercial tunas in the Pacific Ocean II: Sampling considerations and future directions

Moore, Bradley R. and Adams, Tim and Allain, Valerie and Bell, Johann D. and Bigler, Mark and Bromhead, Don and Clark, Sangaa and Davies, Campbell and Evans, Karen and Faasili, Ueta and Farley, Jessica and Fitchett, Mark and Grewe, Peter M. and Hampton, John and Hyde, John and Leroy, Bruno and Lewis, Antony and Lorrain, Anne and Macdonald, Jed I. and Marie, Amandine D. and Minte-Vera, Carolina and Natasha, Janice and Nicol, Simon and Obregon, Pablo and Peatman, Thomas and Pecoraro, Carlo and Phillip, N. Bradley and Pilling, Graham M. and Rico, Ciro and Sanchez, Caroline and Scott, Robert and Phillips}, Joe Scut and Stockwell, Brian and Tremblay-Boyer, Laura and Usu, Thomas and Williams, Ashley J. and Smith, Neville (2020) Defining the stock structures of key commercial tunas in the Pacific Ocean II: Sampling considerations and future directions. Fisheries Research, 230 . p. 105524. ISSN 0165-7836

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Abstract

Delineating the stock structure of highly-mobile, wide-ranging fishes subject to exploitation is a challenging task, yet one that is fundamental to optimal fisheries management. A case in point are stocks of skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus) and albacore tuna (Thunnus alalunga) in the Pacific Ocean, which support important commercial, artisanal, subsistence, and recreational fisheries, and contribute roughly 70 % of global commercial tuna catches. Although some spatial and temporal structuring is recognised within these stocks, growing evidence from a range of approaches suggests that the stock structure of each tuna species is more complex than is currently assumed in both stock assessment and climate change models, and in management regimes. In a move towards improving understanding of the stock structure of skipjack, yellowfin, bigeye and South Pacific albacore tunas in the Pacific Ocean, an international workshop was held in Nouméa, New Caledonia, in October 2018 to review knowledge about their movement and stock structure in the region, define and discuss the main knowledge gaps and uncertainties concerning their stock structure, and develop biological sampling approaches to support the provision of this information. Here, we synthesise the discussions of this latter component. For each tuna species, we identify several general sampling considerations needed to reduce uncertainty, including i) the need for broadscale sampling in space, ideally covering each species’ distribution, targeting adults in spawning condition and adopting a phased approach; ii) the need for temporally-repeated sampling of the same geographical areas to assess stability in observed patterns over time; iii) the need to resolve patterns in spatial dynamics, such as those resulting from movements associated with the seasonal extensions of poleward flowing currents, from underlying stock structure, iv) the importance of adopting a multidisciplinary approach to stock identification, and v) the need for careful planning of logistics and coordination of sampling efforts across agencies. Finally, we present potential sampling designs that could be adopted to help overcome uncertainties around the initial identification of stocks and the provenance, mixing and proportional contributions of individuals in harvested assemblages, as well as how these uncertainties could be accounted for in fisheries management via the use of management strategy evaluation.

Item Type:	Journal Article
Uncontrolled Keywords:	Tuna, Pacific Ocean, Movement, Spatial dynamics, Stock structure, Fisheries management
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > Q Science (General) Q Science > QH Natural history > QH301 Biology
Divisions:	School of Agriculture, Geography, Environment, Ocean and Natural Sciences (SAGEONS)
Depositing User:	Fulori Nainoca - Waqairagata
Date Deposited:	24 Dec 2020 02:58
Last Modified:	24 Dec 2020 03:14
URI:	http://repository.usp.ac.fj/id/eprint/12514

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