Research Document - 2014/010
Preliminary results from the groundfish and shrimp multidisciplinary survey in August 2013 in the Estuary and northern Gulf of St. Lawrence
By Diane Archambault, Hugo Bourdages, Claude Brassard, Peter Galbraith, Johanne Gauthier, François Grégoire, Jean Lambert and Claude Nozeres
Abstract
In 2013, the annual summer survey for the assessment of abundance and distribution of groundfish and shrimp in the Estuary and the northern Gulf of St. Lawrence was conducted from August 1st to September 1st aboard the CCGS Teleost. One of the primary objectives was to estimate abundance and biomass indices for the main groundfish species (Cod Gadus morhua, Greenland Halibut Reinhardtius hippoglossoides, Atlantic Halibut Hippoglossus hippoglossus and redfishes Sebastes fasciatus and S. mentella) and for the Northern Shrimp Pandalus borealis, and to identify the spatial distribution and biological characteristics of these species. The two other main objectives of the survey included monitoring the biodiversity of the Estuary and the northern Gulf, and describing the environmental conditions observed in August for the sampling area.
This report describes the preliminary results on the catch rates and distribution of twenty taxa, as well their size frequency distribution. These results were compared with results from the historical survey series began in 1990, taking into account the equivalency factors used to convert data from the tandem CCGS Alfred Needler-URI to the tandem CCGS Teleost-Campelen. In 2013, the abundance and/or biomass indices of many species were stable or decreased compared to 2012. In fact, Cod (biomass only), Longfin Hake (Phycis chesteri) and Snow crab (Chionoecetes opilio) showed indices values close to or lower than the lower reference limit of their respective averages calculated for the comparative period of 1990-2012. Although in 2013, the American Plaice Hippoglossoides platessoides, Black Dogfish Centroscyllium fabricii and Greenland Halibut indices decreased from 2012 to 2013, they were comparable or higher than the averages estimated for the 1990 – 2012 period. For about ten species, indices (abundance: Atlantic Halibut, Smooth Skate (Malacoraja senta); biomass: Witch Flounder (Glyptocephalus cynoglossus); abundance and biomass: Common Lumpfish (Cyclopterus lumpus), Hagfish (Myxine glutinosa), Silver Hake (Merluccius bilinearis), White Hake (Urophycis tenuis) and the two species of redfishes) increased in 2013 and showed values comparable to or higher than their respective averages for the period 1990-2012. However, increases for among of these three species indices (Acadian and Atlantic redfishes, Silver Hake) were such that the values observed in 2013 were among the highest for the period 1990-2012. The geographic distribution of catches recorded for the different species in 2013 showed the same pattern as in previous years. Finally, the size distributions ranges determined for each species remains relatively stable for the entire time of the historical series, except for the common lumpfish which showed a slight decrease (~ 5 cm) at the maximum size. In addition, for some species (Cod, Greenland Halibut, Hagfish, Acadian and Atlantic redfishes, Silver and White hakes), some size classes observed in 2013 were clearly dominant, and their abundance well above the calculated average distribution average for the comparative period.
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