Reduction of oyster waste: Establishing best practices for controlling wild spat under commercial production

The challenge

Australia’s aquaculture industry currently produces ~9,000 tonnes or $110 million-worth of oysters annually (FAO, 2022; FRDC, 2022), with the Sydney Rock Oyster (SRO) industry accounting for 55% of production (5,000 tonnes and $60 million). However, the SRO industry continues to suffer from extensive crop losses and is far from reaching its full potential. A major cause of these losses is due to ‘overcatch’ or ‘fouling’, whereby juvenile oysters (wild spat) or other aquatic organisms attach themselves to semi-mature oysters. Without timely intervention, the oysters often become unmarketable, leading to substantial proportions of product being discarded or having growth rates considerably slowed (Adams et al., 2011; Watson et al., 2009).

Growers typically attempt to mitigate this fouling using methods like air drying or heat immersion; but both are labour intensive and can result in significant mortalities or even total crop loss if undertaken incorrectly (Mayrand et al., 2015). An estimated 30–50% of SRO grown in Qld and northern NSW are consequently wasted, with a potential value of >$20 million/annum. Under the REDUCE programme, this project aims to address this systemic problem by determining the best pre-harvest treatments for increasing post-harvest oyster yields and avoiding food waste.

Our plan

The proposed project seeks a long overdue opportunity to compare the efficacies and viabilities of various existing and emerging technologies for controlling overcatch / fouling on SRO under commercial production (using the same location, stock and environmental conditions), with the ultimate goal of benchmarking best overcatch management practices and reducing food waste.

Specifically, the key objectives are to:

a. Improve knowledge and establish critical information for controlling overcatch using existing air drying and hot water immersion (boiling) methods in commercial production settings.

b. Provide oysters growers with new technologies that offer more efficient and effective control of overcatch in commercial production settings.

c. Reduce oyster losses/deaths, as well as labour requirements, associated with controlling overcatch, when compared to current practices.

d. Develop practices that can be used for demonstration and training to the wider oyster-growing community and public.