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Basking shark bycatch review, (PDF, 1,569K)

Summary

Basking sharks are caught incidentally in New Zealand trawl and set net fisheries. Previous studies have shown that unstandardised observed trawl catch rates were much higher in 1988–91 than at any time since then.

This study tested the hypotheses that (a) the fluctuations in apparent abundance were driven by environmental factors, and (b) that changes in the composition of trawl fleets, and the way that they operate, have reduced the level of interactions between sharks and trawlers.

Raw catch per unit effort (CPUE) indices were calculated for three large fishery areas off east coast of South Island (EC), west coast of South Island (WC) and Southland–Auckland Is (SA), and compared with three environmental variables (two sea surface temperature indices and sea surface height), vessel nationality, and seven operational trawl variables (vessel length, tow speed, tow duration, headline height, seabed depth, latitude and longitude).

Publication information

Authors: Malcolm Francis and Philip Sutton, National Institute of Water and Atmospheric Research Ltd