Research Document - 2006/065

Atlantic Halibut on the Scotian Shelf and Southern Grand Banks (Div. 3NOPs4VWX5Zc) – Industry/DFO Longline Survey Results to 2005

By Armsworthy, S., S. Wilson, and R.K. Mohn

Abstract

The industry/DFO Atlantic halibut longline survey has been in operation for eight years. During this time, there has been no indication of a change in halibut distribution within the management unit area, 3NOPs4VWX. Overall, there appears to be relative stability in the adult abundance within the fixed station survey, and its size composition indicates there has been no depletion of large fish from the population. The commercial index catch rate shows a decline from 2002 to 2004; however this index is more complex than the fixed station survey, and not all sources of variability have been considered at this time. The number of pre-recruits (fish < 81cm) from the fixed station declined from 2001 to 2004; but in 2005 pre-recruits increased in both the DFO research vessel (RV) survey and the halibut long-line survey, however, there is some uncertainty over the survey’s 2005 data point. Given this information, there was no basis to advise a change in the current fishing levels for 2006-07. Station coverage and NAFO division coverage has been erratic over the course of the survey. A reduction in participation in 2005 was a result of increased cost of fishing operations. It is vital that the survey consistently covers the 72 stations that have been completed in every year of the survey, and that the survey consistently covers the entire management unit area, including 3NOPs. The longline survey is effectively monitoring the direction of change in relative population abundance of Atlantic halibut over time, and its continued operation is essential to the management of the fishery. Results from new research projects including an otolith aging study and a mark-recapture project are expected to provide a greater understanding of the population status, and are anticipated for 2008.

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