World Abalone Fisheries and Stock Enhancement. Where in the world are we at? Is it worth it?
This report gives an over view of the world’s wild harvest abalone fisheries, how they are managed, and the findings of what stock enhancement has been occurring. The countries explored are Australia, New Zealand, Japan, USA and the Republic of South Africa. Hong Kong and The Peoples Republic of China was also visited to explore the market for abalone and customers’ perceptions of hatchery spawned but wild raised abalone.
The world’s wild abalone fisheries production is declining while abalone aquaculture production has been increasing. Australia’s wild harvest abalone production remained relatively stable since the commercial dive fishery started in the 1950’suntilabout 2010. Total allowable commercial catch(TACC),commonly called quotas, were implemented in all harvesting regions by the mid to late 1980’s.Successful abalone recruitment is the key issue for a sustainable fishery. There was a low biomass post the implementation of quotas but now fishing pressure was controlled and reduced. A slow recovery occurred from a low spawning biomass until very good recruitments in the late 1990’s, from 2002 to 2006 there was a large spawning biomass on the reefs, the largest it had been for 15 years; recovery was occurring.
Unfortunately, since 2010, despite the large spawning biomass and controlled fishing pressure, production has decreased at an alarming rate. What is happening to recruitment? Why are the abalone larvae not surviving? How can it be overcome? Something is happening when the abalone are in their early larva land settlement stage, at their most vulnerable stage. Can they be nursed through this stage in a hatchery, reseed them when they are stronger and enhance the reefs and commercial production? These questions were the motivation to visit the world’s wild harvest abalone countries.
Abalone stock enhancement is in its infancy, except for Japan where 30 plus years of stock enhancement sees 30% of their total annual harvest consisting of seeded abalone that achieves a survival rate of 10-15% of what is released. All other countries have undertaken experiments, some for decades with varying results. Further research particularly around the ecology of release areas and large scale projects are needed to determine and improve success. This will be long-term investment requiring substantial money and resources. It is therefore crucial that there is confidence in government to provide protection to the reseeded abalone from any external factors which may interfere with the abalones’ survival.
Not all locations will be conducive to successful stock enhancement and keeping the handling of the juvenile abalone to a minimum is important for survival. No release method stands out as the most successful. The ideal release size appears to be about 30 millimetres shell length. This size is the best because of genetic fitness. The juvenile abalone is strong enough to not succumb to the environmental factors inhibiting recruitment in the first place and is small enough not to be too domesticated from being raised in a hatchery.
Genetic diversity contributes to the genetic fitness and the brood stock parents consisting of tens of males and tens of females should be sourced from the area the juveniles are intended to be released to achieve the greatest survival. The parents should be replaced after each spawning season.
Stock enhancement, combined with resting areas, will be the best way to rebuild the biomass of abalone on the reefs and therefore commercial production. Utilising technology in a fully transparent commercial fishery will be the way to monitor and manage harvesting pressure to find optimum efficiency, quality and reef production.
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