Larval escape through abalone culture effluent systems: An analysis of the risk

Expansion of abalone culture in Western Australia has resulted in the acquisition of juvenile stock (Haliotis laevigata) from interstate, particularly South Australia. This movement has raised concerns about the possibility of compromising the genetic integrity of domestic wild stocks of abalone with exotic genetic material. Such a compromise could arise from the escape of larvae from a production system in the event of a spawning event during the growing period. The use of a fine mesh filter may reduce this risk but is considered impractical because of frequent blockage. A risk model was constructed, which interfaces with an abalone growth model, to predict spawning events and the likelihood of viable larvae surviving in the open sea until they mature and spawn again. The model predicts that the probability of a spawning event leading to larvae escaping, maturing and spawning again in the wild is in the order of 3.7 x 10-6 per production cycle (about 3 y), and if such an event occurred, around IO abalone would reach maturity, or about 17 in the absence of a settling pond for effluent water before discharge. Sensitivity of the model to input variables and implications for further research are discussed