This map shows a snapshot of modelled larval distribution. Blue areas have the least larvae; red areas have the most. The arrows show the direction and speed of currents. An eddy has formed in the lee of the headland at the entrance to Tolaga Bay and larvae are concentrating near the centre of the eddy.
Shellfish larvae are transported along the coast by marine currents, but how far do the larvae spread and how effectively do they settle? These questions have implications for the location of marine reserves.
NIWA has been working with the Department of Conservation, using numerical modelling to study how currents carry larval paua on the Gisborne open coast.
Our results show that an ideal paua management system would space marine reserve areas at intervals of 15–40 km along the coast to ensure larval supply to areas between reserves. Of course there’s a lot more to deciding where to put marine reserves than just the spread of shellfish larvae, but these results show that much needed quantitative information can be provided when marine reserves are being considered.
This work was funded by the Foundation for Research, Science & Technology.