Using line fishing to count fish
Science Centres: Fisheries
Workshop participants with Michael Sigler (standing) fifth from right.
In several important New Zealand fisheries relative abundance may not be adequately indexed by fishery catch and effort data. Such fisheries, which are not readily assessed by trawl surveys or acoustic survey methods, include the bluenose (Hyperoglyphe antarctica) fishery.
A recent NIWA workshop in Nelson brought together scientists working on bluenose in Australia and New Zealand, and sablefish in Alaska, with commercial fishers from New Zealand to assess the feasibility of using line fishing gear quantitatively to assess relative abundance. This method is new to New Zealand, but has been successfully used in Alaska (sablefish, Pacific halibut), the U.S. east coast (Atlantic halibut), the Azores (alfonsino, bream), and New Caledonia (alfonsino).
Keynote speaker Dr Michael Sigler, from the Auke Bay Laboratory of the U.S. National Marine Fisheries Service, described line fishery research methods successfully used to estimate the abundance of Alaskan sablefish (Anoplopoma fimbria). Compared with sablefish, bluenose has a patchy distribution, and a successful survey will require careful determination of appropriate stratification and sample size.
The workshop agreed that a quantitative line survey was the most viable fishery-independent assessment method for species such as bluenose. Data from the Industry Logbook Scheme in the BNS 1 line fishery would be used to determine fine-scale variability in catch rate within fishing grounds and among fishing vessels, and to identify appropriate areas for a pilot survey using standardised commercial longline gear set at random locations within defined strata.