Native fish in the Cotter River are exposed to a number of potential threats including river regulation and interactions with introduced species, particularly from trout. Recreational angling also occurs along part of the Cotter River with self-sustaining populations of trout in close proximity to the city of Canberra. Regular fish monitoring has been conducted along the Cotter River since 2001 and provides information on the distribution of several threatened native fish, as well as Brown and Rainbow Trout. Fish monitoring results suggest that there may be a pattern of low trout and high Two-spined Blackfish (Gadopsis bispinosus) numbers, particularly at sites that are more accessible by anglers. It is hypothesised that take from recreational angling for trout may benefit threatened Two-spined Blackfish by reducing trout abundance. A project is proposed that will investigate interactions between anglers, trout and Two-spined Blackfish in the Cotter River. A number of different options are being considered to investigate this interaction, including re-analysis of existing data and a survey of anglers.