Australian Capital Territory Implementation Report 2004–2005

Driving Action 6: Managing Fish Translocation and Stocking

Highlights

Recreational fish stocking

A total of 79,355 fish was stocked into ACT waters as part of the urban lakes recreational fish stocking program. Murray Cod and were released into Lake Tuggeranong and Yerrabi Pond and Golden perch were released into Lake Burley Griffin and Gungahlin Pond (Table 1).

Threatened species stocking and translocation

Trout cod fry

Photo: Karen Markwort

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As part of the ACT recovery activities for the endangered Trout cod, 30,000 fry were stocked at Angle Crossing on the Murrumbidgee River in December 2004. This is the largest stocking of this species conducted in the ACT, with fish provided by NSW DPI as part of the national recovery effort for this species. A total of 99,500 Trout cod have been stocked at this site since stocking commenced in 1996.

The Two-spined Blackfish is declared vulnerable in the ACT, and now only occurs in the ACT in the Cotter River. It was present in the Murrumbidgee and the Paddys Rivers in the ACT until the early 1960s, but no records exist for the species after that date. It is not known why the species disappeared from these streams, but is possibly related to sedimentation from inappropriate land management, as well as impacts from alien species. In late 2004 a total of 59 Two-spined blackfish (39 juveniles and 20 adults) were translocated from the Cotter River to the Paddys River, in an attempt to re-establish a population in this stream. Monitoring of the survival of released individuals will be conducted in 2005–2006.

Two-spined blackfish

Photo: Janet Pritchard

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Trial re-introduction of Trout cod

A trial re-introduction of the endangered Trout Cod was conducted in the Murrumbidgee and Cotter Rivers in the ACT in late 2004. Previous re-introduction efforts for this species in southeastern Australia have involved the release of small fingerling fish (approximately 3–5 cm long), However, in this trial sub-adult fish (approximately 33–42 cm long) from a commercial hatchery were used, and fish were fitted with radio-transmitters to monitor their movements after release. In an unexpected result, the sub-adult fish suffered considerable mortality over a period of six months after release, with predation by birds and/or water rats suspected as significant causes of mortality. Predation of captive-reared animals after release is a relatively common issue worldwide for reintroduction programs for threatened terrestrial species, but has not previously been documented for aquatic species in Australia. ‘Naïve’ animals from captive-rearing programs are thought to lack the learned predator recognition or avoidance skills that ‘wild’ animals have. Presumably high levels of sedimentation in pools of the Cotter River post-bushfire also reduced the availability of predator refuges for Trout cod. Further investigation into measures to minimize predation or educate fish is planned.