Research Document - 2014/053

Preliminary results from the September 2012 and 2013 bottom-trawl surveys of the southern Gulf of St. Lawrence and comparisons with previous 1971 to 2011 surveys.

By L. Savoie

Abstract

Each autumn since 1971, a standardized research vessel bottom-trawl survey has been conducted in the southern Gulf of St. Lawrence (NAFO Division 4T). The primary objective of this survey is to obtain abundance indices for the major demersal fish resources in the area. This report presents the preliminary results of the survey conducted from 4-27 September 2012 and from 4-28 September in 2013 and comparisons with previous 1971 to 2011 surveys.

The biomass indices for southern Gulf cod, in 2011 and 2012 were at the lowest levels observed in the 43-year survey record, indicating that the abundance and biomass of this stock continue to be very low compared to the levels observed in the late 1970s and during the 1980s. The biomass index for 2013 increased to near the value observed in 2009.

Indices from the 2012 and 2013 surveys suggest that the abundance and biomass of white hake remain extremely low compared to the indices observed in the late 1980s and early 1990s.

The abundance and biomass indices of American plaice reached their highest levels in the late 1970s. The stock has since declined and has reached its lowest level in recent years. In 2011-2013, the overall biomass index for American plaice remained near the lowest levels observed in the survey.

The abundance and biomass survey indices for witch flounder have fluctuated between relatively low and high values during the 2004 to 2013 period. In 2013, the abundance and biomass indices were above the long-term average.

The survey index for winter flounder abundance has been below the long term average in recent years and the biomass index has been generally declining since the late 1980s.

The abundance index of yellowtail flounder in 2012 and 2013 remained comparable to the long-term average. In contrast, the biomass index has declined since the mid-1990s, reaching a value in 2012 that was one-half of the long-term mean, though the 2013 value was near the mean. The abundance and biomass indices for the areas surrounding the Magdalen Islands (strata 428 and 434 to 436) have increased in the past six years.

Bottom temperatures were colder over the central Magdalen Shallows and increased shoreward as depth decreased and along the Laurentian Channel as depth increased. Almost no sub-zero bottom temperatures have been recorded in September throughout the survey area since 2005 and the area covered by waters colder than 1°C decreased in 2013.

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