Population Structure of IOTC species and sharks of interest in the Indian Ocean

In 2017, CSIRO (Australia) in collaboration with AZTI Tecnalia (Spain), IRD (France) and RITF
(Indonesia) commenced a 3-year collaborative project on tuna, billfish and sharks of the Indian
Ocean. The aim of the project was to describe the population structure and connectivity of a range
of tuna and tuna-like species within the Indian Ocean (and adjacent Pacific and Atlantic waters as
appropriate), as well as some of the key shark species that interact with Indian Ocean Tuna
Commission (IOTC) fisheries. A combination of genetics and micro-chemical analysis of hard parts
(otoliths, shark vertebrae) was used as complimentary techniques in investigating population
structure. The project also aimed to develop and extend research networks among partners and
contribute to technical capacity building in participating coastal states, where possible.
The project is now nearing completion with 2 years of sampling completed, almost 6,000 samples
collected of which 3,635 have been genotyped and 689 processed for otolith microchemistry. Initial
data analyses have been completed for the majority of the species for genetics. A summary of the
preliminary results from these analyses are presented in this working paper. Micro-chemistry
analysis are complete for swordfish, albacore, skipjack and yellowfin tuna and the preliminary
results from these are also included here. The micro-chemistry for the neritics species and bigeye
tuna is in progress and will be reported on in the near future.
The sample collection and processing phases of the project have provided a sound foundation for
many of the species, but improvements/additions are needed for others before substantive
interpretations and conclusions about population structure will be able to be made. Very
preliminary results suggest structure for some species while not providing evidence for others.
Further detail analysis required before any substantive conclusions can be drawn. We invite initial
comment and input from the Scientific Committee on the work completed to date and the very
preliminary results presented here. There will be further opportunity for to review more substantive
results and initial interpretation in the draft final report (due 20 Dec 2019) which will be followed
by the final report (due 31 March 2020) and subsequent papers to the relevant working groups in
2020.