Research Document - 2010/062

Vessel calibration results for redfish (Sebastes sp.) from comparative fishing between the CCGS Teleost research vessel and the MV Cape Beaver fishing vessel

By N.G. Cadigan and D. Power

Abstract

The DFO research vessel CCGS Teleost and the fishing vessel MV Cape Beaver (or sister vessel MV Cape Ballard) have been used in stratified-random bottom trawl surveys for redfish (Sebastes sp.) in the management area UNIT2 (NAFO Div. 3P4V). The two vessels may have different stock-catchabilities, mainly because of differences in the vessel classes, fishing gears and fishing protocols. Adjustment or calibration of their catch rates was explored to combine survey data for each vessel into a single time-series of stock size indices. A paired-tow fishing experiment with 24 sets was carried out in August 2000 to calibrate the vessels. These data were analyzed using a generalized linear mixed model to provide a length-based conversion formula to calibrate Cape Ballard survey catches to Teleost catches. The model also accounted for within-pair random differences in the length distributions of fish encountered by each vessel. The results indicated that there was no overall significant difference in catch rates, but that there was a significant length effect such that the Teleost will catch more small fish (< 30 cm) and the Cape Ballard will catch more large fish (> 30 cm).

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