2011/762 Recovering a collapsed abalone stock through translocation

By Anthony Hart

In the summer of 2010/11, the abalone stocks in Kalbarri region of Western Australia suffered a devastating mortality as result of a sustained period of elevated water temperatures, now being termed the "2011 marine heatwave" off Western Australia. Both commercial and recreational abalone fisheries have subsequently been closed to fishing to protect any remaining animals and promote natural recovery. Unfortunately however, the severe extent of the mortality (>99.9%) means that natural recovery is unlikely within the next 10-20 years. One of the key predictions of the impacts of a changing environment on fisheries is increased variability as well as increased average SST, with consequent effects of range contractions or extension of species at the edges of their natural range. This particular case represents a perfect example of this effect, as this abalone fishery (Area 8 fishery) is located at the northern end of the species (Haliotis roei) range.

The question now being asked by stakeholders is whether recovery of this fishery can be assisted using the latest knowledge in translocation, stocking and restocking methodology, which the Department holds particular expertise in. This incident provides an opportunity to test an important management strategy, namely will the establishment of a founder population be a viable tool for fishery restoration, particularly in stocks like abalone that have localised recruitment? This can be determined by comparing natural and assisted recovery rates and evaluating the genetic contribution of existing and founder populations. Such a study is relevant to all Australian abalone fisheries and an integral part of understanding how fisheries populations can be sustained in a changing environment.

This project aimed to:

1. Establish founder populations of roe's abalone in areas of mass mortality
2. Evaluate the genetic structure of existing and founder populations
3. Compare natural and assisted recovery rates of roe's abalone populations
4. Evaluate the genetic contribution of existing and founder populations to stock recovery