Research Document - 2012/068
Results from the 2011 sentinel bottom-trawl survey in the southern Gulf of St. Lawrence and comparisons with previous 2003 to 2010 surveys
By L. Savoie
Abstract
A sentinel bottom-trawl survey was undertaken in NAFO division 4T each August from 2003 to 2011. This survey used a stratified-random sampling design along with standardized fishing protocols. Four commercial vessels participated each year. Formal statistical tests revealed significant differences in relative fishing efficiency between vessels. Estimates of relative efficiency were used to adjust catch levels with respect to a reference vessel. Length frequency distributions of fish caught by each vessel were also compared informally. Standardized abundance indices and total length frequencies, and maps of annual catch distribution are presented for commercial groundfish species (Atlantic cod, white hake and various flatfish) and Atlantic herring. Since 2003, there have been statistically significant decreases in the abundance of Atlantic cod, American plaice, winter flounder and yellowtail flounder, and a non-significant decrease in white hake abundance. The abundance of Atlantic herring and Atlantic halibut varied without trend over the same period. Various issues related to the formal modeling and testing are discussed.
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