Stocking success and management of a recreational fishery, Glenbawn Dam, NSW, Australia.
Stocking is a management tool frequently used to enhance or create recreational fisheries. Determining the success of past stockings is essential in order to attempt to manage these fisheries. Many factors could affect the survival of stocked fish but these remain to be quantified.
We used incremental ageing techniques to determine year-class strength in a large coastal reservoir, Glenbawn Dam, in New South Wales. Year classes were correlated with environmental variables to determine factors associated with increased survival of stocked fish. Australian bass (Macquaria novemaculeata) and golden perch (Macquaria ambigua) live for up to 12 years but there were marked differences in growth rates for each species. There are large variations in length-at-age in both species. Australian bass took up to 8 years to reach 300mm whilst golden perch took up to 10 years. Survival of stocked bass and golden perch fingerlings did not occur every year. Both species were generalist carnivores preying on a variety of macrocrustaceans, insects and fish. Dietary analysis revealed high dietary overlap between both species suggesting increased competition for available resources.
Almost 2,000,000 golden perch and 1,000,000 Australian Bass have been stocked into Glenbawn dam. Previously, managers have stocked without any information to assist in deciding the correct numbers to release. In some years, up to 500,000 fingerlings have been released and in other years as little as only 3,000 were released. This study will aid future stocking events by identifying factors which are most likely to result in the survival of stocked fish.