ASSESSING THE COMMERCIAL POTENTIAL FOR COLLECTION OF GREENSHELL™ MUSSEL SEED IN THE HAURAKI GULF, NEW ZEALAND

Greenshell™ mussel production in New Zealand is constrained by three main factors. The first being the highly seasonal nature of Greenshell™ mussel production. In northern New Zealand mussels spawn mostly from July to November and during much of this period mussels cannot be harvested due to their poor condition. The second is the industry's heavy reliance on a single source of beachcast wild seed which supplies around 80% of the spat used in the country's mussel aquaculture industry.  Finally, the loss of mussel seed from nursery ropes can be as high as 100%, but is usually between 50 and 70%. This wasteful use of mussel seed is thought to cost the industry between NZD$6-10 million annually. Anecdotal evidence suggests that mussels from the Hauraki Gulf region may develop and spawn at a different time of the year to seed from the main commercial seed source.  If this were the case and mussel seed could be collected commercially in the Hauraki Gulf this could potentially extend the harvesting season as well as provide an alternative source of mussel seed. This study focused on the following aims; 1) determining whether seed mussels obtained from two different sources have different annual condition cycles, and growth rates, 2) determining the yearly pattern of seed arrival in the Hauraki Gulf, and 3) comparing the retention rates between the two seed sources.