RESTOCKING FISH SPECIES

Australian Centre for Applied Aquaculture Research (ACAAR) has expertise in the restocking of estuarine and marine fish. In collaboration with Murdoch University, ACAAR started work in this field in 1992. Black bream were identified as being in decline in the Blackwood River Estuary and 220,000 juvenile cultured black bream were restocked in 2001 and 2002. These fish were monitored and are now contributing to natural recruitment.  The ACAAR/MU partnership was honoured with the Best Recreational Enhancement Project award at the inaugural 2006 National Recreational Fishing Awards and the Environment Award from the WA Fishing Industry Council for rehabilitating a fishery in 2010. Today, over two thirds of the legal catch of black bream in the Blackwood River are restocked fish.

ACAAR has been culturing black bream (Acanthopagrus butcheri) since 1992, principally for student training and restocking.

The Blackwood Project
Restocking of estuarine and marine fish is a contentious issue for some in WA, but the ACAAR of the Challenger Institute of Technology made the pragmatic decision to start work in this field in 1992 at a time when fish stocks did not appear to be at risk in WA. This decision was made however with the historical knowledge that fish stocks around the world have declined over time. So Western Australia needed to be ahead of the field when or if that time came along, to understand the issues and to be able to restock responsibly and to have world-class expertise.

Black Bream was the first species investigated, specifically in the Blackwood River, as stocks were in significant decline and under threat of localised extinction.

The sole commercial fisherman in the Blackwood River Estuary, Mr Trevor Price, has seen the numbers of Black Bream decline dramatically in the system over his lifetime. Mr Price significantly reduced his fishing effort for Black Bream in the river in 1995 due to the low numbers of the species. The Fisheries Research and Development Corporation funded the Challenger Institute, in collaboration with Murdoch University, to undertake a pilot restocking of the Blackwood River Estuary from 2000 – 2005 (Jenkins et.al. 2006.)

Mr Price was very supportive of the restocking trial and captured all of the required broodstock for the program. A total of 56 female and 50 male mature Black Bream were collected from the Blackwood River Estuary and transported to the Challenger Institute Hatchery in Fremantle to produce the juveniles required for restocking this estuary.
A total of 220,000 Black Bream were cultured, marked and released in 2001 and 2002, survived well and comprised 75% and 92% of catches of Black Bream of the 2001 and 2002 year classes, respectively. The broodstock fish were also released back into the estuary.

Mr Price recommenced his previous level of fishing effort for this species in the Blackwood in 2005 when the restocked fish first reached legal size and were abundant. These restocked fish are still being monitoring and in 2007, as mature fish, accounted for a total of 67% of the commercial catch in the Blackwood by Mr Trevor Price. Even more importantly, for the first time in over 15 years, Mr Price has recently observed large numbers of small Black Bream in the estuary, indicating a significant successful spawning and recruitment of this species. Given the high percentage of mature restocked Black Bream in the system, this successful recruitment can clearly be attributed to the restocking program.

This project has clearly demonstrated that the fishery for Black Bream in the Blackwood River Estuary has been significantly rehabilitated through the introduction of cultured fish. The commercial fisherman has recommenced fishing for the species in the estuary and significant recruitment is now taking place as a direct consequence of the increased number of broodstock in the river.