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DocumentOther documentWCPFC: Evaluation of tag mixing assumptions for skipjack, yellowfin and bigeye tuna stock assessments in the western Pacific and Indian Oceans. 2013. WCPFC-SC9-2013/SA-IP-11 2013
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No results found.ng (or mark-recapture) studies generally require the assumption that tagged and untagged individuals (of a particular demographic group) are equally likely to be captured. For tu, this usually translates into the assumption that tagged fish released from a relatively small region (selected for logistical reasons) mix rapidly over a much broader region of interest. In this paper, we apply the Comparison of Paired Recovery Distribution (CPRD) alysis to skipjack (Katsuwonus pelamis), yellowfin (Thu nnus albacares) and bigeye tu (Thunnus obesus) from large-scale tagging programmes in the Western Pacific and Indian Oceans. The CPRD alysis uses chi-square and nearest neighbour permutation statistical tests to calculate the probability that two tag recovery distributions from different release events are drawn from the same spatial distribution. The release events were separated in space and/or time and recovered in the same time window. If there is evidence that the two recovery distributions differ, it follows that tags from the two release events are not fully mixed with each other, such that at least one would also not be mixed with the untagged population either. Recovery events were defined with spatial boundaries corresponding to the most recent stock assessments, and alyses were restricted to release areas that were entirely within the recovery region. In the WCPO, there was strong evidence of incomplete mixing for 5 quarters following release for skipjack and yellowfin tus a nd 1 quarter for bigeye tu. For all 3 species, the observed periods of incomplete mixing is clearly a minimum, as there were insufficient observations to make inferences with respect to longer periods at liberty. In the Indian Ocean, there is strong evidence for incomplete mixing for skipjack for 3 quarters following release, 2 quarters for yellowfin and 1 quarter for bigeye. In contrast to the WCPO, useful numbers of CPRD events of longer duration were identified but did not show consistent com pelling evidence of incomplete mixing. The difference between the Pacific and Indian Ocean results may reflect genuine characteristics of mixing rates (e.g. tu in archipelagic waters seem to migrate shorter distances on average that tu in oceanic waters). However, the failure to detect incomplete mixing in the Indian Ocean may also reflect methodological limitations arising from the opportunistic ture of tag observations (e.g. the spatial distribution of Indian Ocean tag releases and recoveries was more restricted than in the WCPO). We expect that the mixing problem is serious enough to potentially introduce large biases to at least some of these stock assessments, but the magnitude of the biases may not be easy to quantify. -
MeetingMeeting documentComparative analysis of the exploitation of bigeye tuna in the Indian and Eastern Atlantic Oceans with emphasis on purse seine fisheries 2013
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MeetingMeeting documentUpdated growth estimates for skipjack, yellowfin and bigeye tuna in the Indian Ocean using the most recent tag-recapture and otolith data 2013
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Book (stand-alone)ProceedingsProceedings Of The Programme Inception Workshop: Forestry Information Processes And Planning - Bangkok, Thailand
Information and analysis for sustainable forest management: linking national and international efforts in South and Southeast Asia
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No results found.Summary of conference proceedings incorporating the text of papers presented -
Brochure, flyer, fact-sheetBrochureJoint Programme on Gender Transformative Approaches for Food Security and Nutrition
2022 in Review
2023Also available in:
No results found.The 'JP GTA - 2022 In Review' offers a snapshot of the milestones, achievements and activities of the Joint Programme over the course of the past year, with links to articles, publications and event recordings. The report is structured along the four pillars of the JP GTA, with sections focusing on knowledge generation, country-level activities, capacity development and learning, and policy support and institutional engagement. The page on 'knowledge generation' offers an overview of resources published or facilitated by the JP GTA in 2022. Under 'country-level activities' readers will find a summary of the key activities and achievements of the Joint Programme in Ecuador and Malawi. The section on 'capacity development and learning' delves into the JP GTA’s initiatives to share lessons from the Programme and build colleagues' and partners' knowledge and skills. The final pages on 'policy support and institutional engagement' highlight major global and corporate initiatives supported by the JP GTA. -
Book (series)GuidelineResponsible fish utilization 1998These guidelines have been produced to support the implementation of the Code of Conduct for Responsible Fisheries particularly with regard to the need for responsibility in the post-harvest sector of the fish producing industry. The industry that produces fish for food has three major areas of responsibility: to the consumer of the food to ensure that it is safe to eat, is of expected quality and nutritional value, to the resource to ensure that it is not wasted and to the envir onment to ensure that negative impacts are minimized. In addition the industry has a responsibility to itself to ensure the continued ability of many millions of people throughout the world to earn a gainful living from working within the industry. Article 11.1 of the Code of Conduct for Responsible Fisheries and other related parts of the Code are concerned particularly with these responsibilities. This publication provides annotation to and guidance on these articles to assist those c harged with implementation of the Code to identify possible courses of action necessary to ensure that the industry is conducted in a sustainable manner.