© 2004 International Council for the Exploration of the Sea
Using fish-processing time to carry out acoustic surveys from commercial vessels
National Institute of Water and Atmospheric Research Private Bag 14-901, Kilbirnie, Wellington, New Zealand
*Correspondence to R. L. O'Driscoll: tel: +64 4 386 0300; fax: +64 4 386 0574. e-mail: r.odriscoll{at}niwa.co.nz.
In some fisheries large factory freezer trawlers have periods of down time as the catch is processed. By utilizing this time, scientific acoustic surveys can be carried out between commercial-fishing operations without compromising fishing success. Examples are presented from three acoustic surveys for hoki (Macruronus novaezelandiae) in New Zealand waters during 2002 and 2003 conducted from a commercial vessel fitted with a scientifically calibrated SIMRAD ES-60 echosounder. These surveys confirmed the presence of a new spawning area for hoki and provided biomass estimates from known fishing grounds. The approach described works well for small-scale acoustic surveys adjacent to areas of high catch rates and is cost-effective because the vessel "pays for itself" by fishing commercially. The major limitation is that the boundaries of the survey area are determined by the time available during processing, which is related to the size of the catch and the time required to search for a suitable location for the next commercial trawl. In the New Zealand hoki surveys, processing time was typically 3–8 h, which was sufficient to carry out about 10–70 km of acoustic transects. Acoustic research was also limited to periods of relatively good conditions by the use of a hull-mounted transducer.
Keywords: acoustic survey, commercial fishing, hoki, New Zealand
Received 21 June 2004; accepted 9 November 2004.