Looking back to go forward- Recreating a world class Chinook salmon fishery in Victoria's western crater lakes
Taylor Hunt, Paul Brown and Khageswor Giri
The release of hatchery bred Chinook salmon into Victoria's western crater lakes in the mid 1900's (stocking) was successful in creating exceptional trophy fisheries in waters such as Lake Bullen Merri and Lake Purrumbete (Butcher 1947; Clements 1988). Particularly in the late 1970s, 1980s and early 1990s, these fisheries were heralded as one of only a few land-locked Chinook salmon fisheries in the world, generating extraordinary interest, angler participation and associated economic and social benefits. More recently, it is thought the performance of these Chinook salmon fisheries has declined.
The recreational fishing community is keen to recreate a world class Chinook salmon fishery in Victoria's western crater lakes. To do this, it is necessary to determine what factors contributed to the high performance of this fishery in the past.
The objectives of this project were to:
- Analyse available stocking, fisheries assessment and angling club data to develop time-series that describe the changes in the Chinook salmon fisheries over time.
- Assess available data to determine if suitable to construct a simulation model that can be used to inform stocking strategies. If suitable, provide details and potential costing of modelling project.
- Identify stocking strategies to re-establish high quality Chinook salmon fisheries at Lakes Bullen Merri and Purrumbete. If suitable, recommend a three-year stocking plan.
The study found:
- Major fluctuations in fishery performance between 1978 and 2008 for Lake Bullen Merri and 1969 and 2009 for Lake Purrumbete
- The more Chinook salmon yearlings stocked into the lakes, the higher the catch rates (in the same year of stocking)
- The fewer Chinook salmon yearlings stocked into the lakes, the higher the return to anglers in terms of the size (weight) of fish caught
- The average weight of angler caught Chinook salmon in Lake Purrumbete decreased when greater numbers of other species had been stocked in the lake over a four year period
- A trade off relationship between catch rate and fish size from numbers stocked found for Lake Purrumbete will be valuable in helping fisheries managers and stakeholders plan fish stocking to optimise fisheries management goals for stocked crater lakes, and potentially, other waters.
- Density dependent growth with respect to stocking in Lake Purrumbete will be suitable to use in a simulation model to help refine the stocking strategies for the crater lakes. These data will be useful to construct a multi-species simulation model to investigate how stocking affects the performance of other species such as rainbow trout; Oncorhynchus mykiss and brown trout; Salmo trutta.
- Depending on the desired outcome of type of Chinook salmon fishery, three different options were suitable to be applied annually over the next three-year period in each lake:
- Maximum return to angler of Chinook salmon = 20,000 yearling Chinook salmon and zero trout per year.
- Optimal return to angler of Chinook salmon at 50% of current trout stocking = 15,000 yearling Chinook salmon and 15,000 yearling trout per year.
- Optimal return to angler of Chinook salmon at current trout stocking = 10,000 yearling Chinook salmon and 25,000 yearling trout per year.
- Evaluation of the revised stocking strategies using one of three options provided will be essential to learn from and improve these fisheries further.
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