Research Document - 2000/132
Results of data conversions for American plaice in Div. 2J and 3K from comparative fishing trials between the Engel otter trawl and the Campelen 1800 shrimp trawl.
By M.J. Morgan and W.B. Brodie
Abstract
In the fall of 1995 the Department of Fisheries and Oceans changed its survey trawl from an Engel 145 high rise otter trawl with bobbin gear to a Campelen 1800 shrimp trawl using rockhopper gear. In the 2+3K area there was also a change in vessel from the Gadus Atlantica to the Teleost. In order to establish a link between the two sets of survey data, comparative fishing trials were conducted in 1995 to develop length based conversion factors between the two fishing gear/vessel combinations. The application of the conversion factors results in a large increase in the abundance of small sizes. When age length keys are applied to the converted data the age compositions are shifted towards younger fish with large increases in the numbers of fish less than age 7 or 8. Trends in total abundance are the same for the original and converted data, with abundance levels being greater for the converted series. The same result is clear for biomass, with both series showing large declines over the time period but with the level of biomass being greater for the converted series.
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