Carp Summer Report

The big wet of winter and spring in 2009 reinvigorated many fisheries around the State, benefiting freshwater anglers and fisheries management. Unfortunately, however, the rising water levels at lakes Sorell and Crescent also benefited pest carp, bringing an unprecedented challenge for fisheries management and an intensive response by the Inland Fisheries Service carp management team.

Carp spawning activity is triggered by rising water levels and temperatures. Adult fish aggregate and seek out marsh areas in which to spawn. The increased water levels last year led to an inundation of extensive areas of wetlands around both lakes at the start of spring providing ideal spawning habitat. This situation, coupled with the onset of warmer weather in spring and summer, resulted in the best possible conditions for carp spawning in Tasmania since the carp management program began in 1995.

In preparation for the expected summer spawning season, the IFS carp team installed barrier fences and traps during the winter months to prevent carp from entering the marsh areas to spawn. The team then commenced a period of intensive work in October, monitoring carp activity in both lakes seven days a week during daylight hours using the male ‘radio-tracker fish’ as indicators of spawning behaviour.

Over this period, there were multiple aggregations of small numbers of carp at many different locations across the lakes and a good number of female carp were removed from Lake Sorell. Although the fish in Lake Crescent were active, no female carp were detected in the aggregations and there does not appear to have been any successful spawning again this year. Recent surveys at Lake Sorell however, indicate that several spawning incidents did occur, resulting in the recruitment of a significant number of juvenile carp.

The IFS has responded to the situation as a priority with teams of up to a dozen IFS staff working to capture and remove juvenile fish which have concentrated in the marsh areas at Lake Sorell. This was an immediate strategy to prevent the young fish returning to the main part of the lake as the marshes begin to drain and has resulted in the successful removal of a large number of carp over the past two weeks.

The IFS will continue this effort to eradicate juvenile carp at Lake Sorell and closely monitor the activity of adult fish at both lakes. A full assessment of the extent of the spawning and resulting carp numbers will be undertaken over the next three months. Further information will be available at that time, including detail on the success of the carp eradication response strategies.