Tracking blue cod in Fiordland
Science Centres: Fisheries
Details of relative abundance and movement rates of blue cod in Fiordland are important to determine the best scale for management of this species. Blue cod are susceptible to localised depletion, and small-scale management may be needed in areas of high fishing pressure.
The Guardians of Fiordland’s Fisheries believe that Milford Sound, one of two access points for fishers visiting Fiordland, no longer supports a blue cod fishery of the quality formerly offered. Doubtful Sound is the second access point, and there are concerns that increasing recreational pressure will lead to the depletion of blue cod in the Sound and its associated waterways
In a project commissioned by the Ministry of Fisheries, NIWA staff tagged 4082 blue cod with “T-tags” over 15 days in October 2001. Fish were released in five areas in Dusky Sound to study their movement and mixing rates within Dusky Sound and between the outer coast and neighbouring fiords. Blue cod were caught by commercial cod pots covered in a 1-cm soft mesh. Catch rate data were recorded and will be used to estimate relative abundance in the recovery phase of the project this spring. To assist with the calculations, catch data collected in logbooks by volunteer fishers during the tagging programme will also be used.
The T-tags have a clearly visible logo, and tag returns are encouraged by offering a tee shirt for each fisher’s first tag; for each subsequent tag they go into a prize draw.
By the end of September 2002, 200 tags had been returned. Glen Carbines, the scientist responsible for the programme, commented that although the return rate was encouraging, he hoped for more detailed information from fishers on the time and location of recaptures.