Are Indian Ocean tuna populations assessed and managed at the appropriate spatial scale? Brief review of the evidence and implications

Tuna species managed under the auspices of the Indian Ocean Tuna Commission have generally been assumed (explicitly or implicitly) to be highly mobile and consist of a single panmictic spawning population for the purposes of stock assessment and management. In this paper, we: i) briefly review evidence that questions this assumption (largely based on recent population genetics and tagging studies), ii) qualitatively discuss the implications of violating this assumption, and iii) outline some elements of a collaborative research plan to resolve these issues and mitigate the consequences of getting this assumption wrong. This paper is intended to stimulate discussion within the IOTC scientific community about the potential importance of population structure within the Indian Ocean and extent to which it should be considered a research and management priority.