Recent studies on the population delineation of yellowfin tuna in the Indian Ocean – considerations for stock assessment

The Indian Ocean yellowfin tuna (YFT) stock assessment by Indian Ocean Tuna Commission (IOTC) is undertaken based on the assumption of a single stock for the entire Indian Ocean. However, molecular studies by Kunal et al. (2013), based on the Mitochondrial DNA D-loop analysis identified three discrete populations of yellowfin tuna in the Indian waters (Northern Arabian Sea, Lakshadweep Islands and rest of Indian Seas). A larger study with samples from all the oceans using whole-genome sequencing in concert with a draft genome assembly also indicated possibility of a distinct yellowfin tuna population in the Arabian Sea in addition to Atlantic and Indo-Pacific populations (Barth et al., 2017). The probable existence of distinct yellowfin populations in the Indian Ocean raises important management considerations for this species, which need to be addressed at the earliest for ensuring sustainability of the species.