Theme F: Enhanced knowledge on populations and ecosystems from releases of cultured animals
47. DOES STOCKING AUSTRALIAN NATIVE PREDATORY FISH PROVIDE A CONTROL OPTION FOR INVASIVE EUROPEAN CARP (CYPRINUS CARPIO)?
Katherine Doyle
University of Queensland
katiedoyle190@hotmail.com
Stocking activities support a number of vital objectives in fisheries management, including native fish enhancement, improved water quality (biomanipulation), recreational fishing and biological control. We examined the potential for stock enhancement of Australian native fish to control invasive European carp (Cyprinus carpio) through predation. We selected two factors for quantification that may influence predation rates on carp; prey size and relative abundance, and the habitat type in which a predator forages. In tank trials, Murray cod (Maccullochella peelii peelii), golden perch (Macquaria ambigua) and Australian bass (Macquaria novemaculeata) had no significant preference for any particular species offered. When offered a carp of varying sizes, golden perch and Australian bass consumed the smallest carp available, whereas Murray cod showed no size preference. In Australian rivers, adult carp select inundated macrophytes in shallow, peripheral marginal habitats that are relatively free from predators to spawn. Juvenile carp therefore have the opportunity to grow rapidly in these habitats and soon reach a size that is free from predation by gape-limited predators. Predators with a preference for smaller carp may not have any impact on reducing carp populations. In mesocosm trials, Murray cod prey preferences were altered by the available habitat type, but there were still no strong preferences for carp when native prey were available. These results suggest that foraging activities and predation rates in aquatic systems are influenced by particular combinations of abiotic factors, such as habitat type and complexity, and biotic factors such as prey size and food availability. Evaluation of prey preferences under varying conditions is crucial prior to stocking predators for biological control to avoid potentially devastating and irreversible impacts on non-target species.
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