The effects of commercial fishing on Octopus pallidus populations in northern Tasmanian waters
2009
The Octopus pallidus Fishery (OPF) is one of the few expanding fisheries in Tasmania, with
annual catches approaching 100 t and a strong established market for fresh and value added products. Regardless of this, detailed information on the basic biology of O. pallidus has been unavailable until very recently, thus limiting investigations into the potential effects
commercial fishing on stocks. The aim of this research is to determine the sustainability of
preset fishing practices in the OPF. To achieve this catch per unit of effort (cpue) and
biological information from a fixed position experimental research line were investigated for
consistency in stock status patterns and compared with commercial fishery cpue trends. The
research line results revealed that cpue could remain stable regardless of size-selective fishing mortality potentially impacting recruitment. Cpue in the commercial fishery was highly
seasonal and dominated by females in autumn, when both cpue and spawning periods peaked,
thus increasing the potential for negative fishery impacts on egg production. The inability of
cpue to account for the effects of continual fishing pressure on recruitment or seasonal
changes in sex-specific catchability indicates that cpue alone cannot provide sufficient
information on the status of the OPF. In order to minimise the potential impacts of size
selective fishing mortality, it is recommended that annual catch limits be based on half degree
fishing blocks and that present biological catch sampling requirements are continued. Thus
helping to ensure that the OPF remains environmentally and economically sustainable.
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