Arthurs Lake is a wild brown trout recreational fishery that has not been stocked for 70 years. The inflowing streams provide large of areas suitable for spawning and thus the lake gets ample recruitment when conditions are favourable. Between 2009 and 2014 good rainfall events enabled successful recruitment to the lake for five consecutive years. The population of brown trout since this period has been large and resulted in a reduced potential for growth and consequently a small average sized fish, less than 400 grams.
The Inland Fisheries Service as managers of the brown trout fisheries in Tasmania have sought to improve the average size of trout at Arthurs Lake with the aim of achieving an average weight of one kilogram. The installation of barriers to upstream migration on three of the lakes spawning creeks together with trapping facilities was completed in 2014 in order to achieve that aim. The quantum of fish to be removed from the fishery to achieve the aim has not been determined, neither has the current size of the brown trout population in the lake.
Determining the size of the population of brown trout at Arthurs Lake is problematic due it is a large storage of 65km2 and 511,550Ml at full supply level. Further to this, the actual number of fish in the lake has never been quantified thus the upper limits are unknown.
A mark and recapture study is proposed for 2017 utilising spawning trout as the marked population. An in-lake recapture phase will occur post spawning period after sufficient mixing with the non-spawning population of fish. Using the 2016 spawning run a pilot study has commenced to examine tag loss, mixing time and other factors that may influence the estimate.