Wild brown trout are the only species of trout recorded at Arthurs Lake and this has been the case since the 1960’s. Arthurs Lake is known for its good catch rate of wild brown trout. Arthurs Lake brown trout population is totally self-sustaining with ample recruitment coming from the creeks that flow into the northern and western shores.
Each year the spawning run is monitored to gauge the average size of the fish making up the adult population. In recent years the average weight in the spawning run has been around 850 grams with the size ranging from 200 to 1800 grams. The condition of the fish in the spawning run is of a good standard and this is usually the case in the fish caught by anglers in the lake during throughout the season. Each year fish in excess of the old fashioned benchmark of 10 pounds are caught and fish of up to 16 pounds have been caught in recent years.
Two species of indigenous fish are endemic (only found at) to Arthurs Lake and the nearby Woods Lake, the Saddled galaxias (Galaxias tanycephalus) and Arthurs paragalaxias (Paragalaxias mesotes). Both species are threatened and listed as vulnerable and endangered under the Tasmanian Threatened Species Protection Act 1995.