Predation of stocked Brook Char Salvelinus fontinalis by Short-finned Eel Anguilla australis and interactions with other salmonids in Wollondibby Creek in the high country of south eastern Australia

This study was initiated to investigate poor survival of stocked Brook Char Salvelinus fontinalis in Wollondibby Creek, a tributary of Lake Jindabyne in the south eastern highlands of NSW, Australia. Sampling of the creek following stocking was carried out on two separate occasions by poisoning 17.6 km, almost the entire length of the creek in 19 sections. Collection of fish was shown to be 78% effective. Five species of fish were present in the creek: Salvelinus fontinalis, Salmo trutta, Oncorhynchus mykiss, Anguilla australis and Galaxias sp. Population density in terms of numbers of fish per hectare and kilograms of fish per hectare of all species present was determined. Recovery of stocked S. fontinalis was low (0.38% in 1977 and 0.15% in 1979). Distribution of salmonid populations in the creek was significantly affected by physical barriers and eel predation, not cormorants as first thought. Eel predation was confirmed by the presence of salmonids in eel stomachs and extensive fin damage as a result of eel attack. Only five S. fontinalis in the first sampling event and one in the second sampling event had reached angling size (250 mm). It is suggested that stocking of S. fontinalis not be carried out in areas where A. australis occurs and that careful consideration be given to the location of physical barriers in the creek when stocking and the presence of native fish.