Spatial models of tunas
One of the most exciting projects being undertaken by Ocean Environmental is an investigation into the spatial dynamics of open ocean tunas. We are looking at methods to evaluate the impact of tagged fish movement and mixing assumptions using high resolution spatially explicit population dynamics models.

We are updating and developing a generalised spatially explicit statistical catch-at-age population modelling tool (the Spatial Population Model). With this, we can can model complex population dynamics and multiple species within a high-resolution spatially explicit framework.

With world tuna catch being worth more than US$42 billion annually, understanding how to sustainably manage open ocean tuna fisheries is critically important. Tag data provide a potential means to understand population size and dynamics, and research into the spatial dynamics of tagged fish and the wider population is one of Ocean Environmental's contributions to this understanding.

We are working with NIWA and the Indian Ocean Tuna Commission (IOTC) to research yellowfin tuna. The IOTC is mandated to manage 16 species of tuna and tuna-like species, with the primary objective to conserve and provide for optimum utilisation of the stocks while ensuring long-term sustainability. Tropical tuna (yellowfin tuna, skipjack tuna, and bigeye tuna) have accounted for about 55% of total catches of all IOTC managed species in recent years and are of major commercial importance to Indian Ocean coastal states as well as the distant water fishing nations.

In this project, we have developed a spatially explicit operating model for yellowfin tuna in the Indian Ocean using the Spatial Population Model. We use the catch rates, length frequencies and tag movements along with environmental variables such as sea surface temperature and concentration of Chlorophyll-a to model the spatial distribution of yellowfin tuna, and use these to understand the spatial dynamics of yellowfin tuna.

This research is enabling us to understand how tuna populations respond to the natural environment - and helping inform the scientific advice on the levels of catch that ensure sustainability.

For more information, contact us at Enquiries@OceanEnvironmental.co.nz

Home | Research | What we do | Contact