Research Document - 2012/161

Comparative survey between Digby and Miracle drag gear for scallop surveys in the Bay of Fundy

By S.J. Smith, A. Glass, J. Sameoto, B. Hubley, A. Reeves, and L. Nasmith

Abstract

Annual surveys using four-gang Digby style drag gear have been used to monitor the scallop grounds in the Bay of Fundy and Approaches since 1989. This gear had been originally designed for the Canadian Coast Guard vessel J.L. Hart, which was used for the surveys until it was retired in 2004.& Surveys were conducted on the fishing vessel Royal Fundy from 2005 to 2011 with this same gear. The decision was made to replace the survey gear in 2012 with the more modern nine-gear Miracle gear in response to the fishing industry’s concern about the effect of the widespread distribution of the bryozoan Flustra foliacea on the performance of the Digby gear and the anticipation that heavier gear would be required for the new Coast Guard vessel being built to replace the J.L. Hart. In the end, the new Coast Guard vessel was not delivered to the Maritimes Region and another fishing vessel with the new Miracle gear was used under contract for the survey in 2012. A comparative fishing experiment was conducted during the 2012 survey to compare the Digby and Miracle gears. The results presented here show that, for scallops, there were no significant differences between the two gears in terms of numbers caught or shell height frequencies when corrected for the same swept area, and, therefore, abundance estimates from the new time series with the new vessel and gear can be used as is with the previous time series of survey estimates. While differences between gears for the catch of skates were found, these differences were only significant when the Digby gear towed first. For all non-scallop species recorded during the scallop survey, it was not possible to determine a conversion factor. Therefore, survey trends for these other species including skate should be treated as separate time series by gear.

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