Research Document 2018/036

Preliminary results from the groundfish and shrimp multidisciplinary survey in August 2017 in the Estuary and northern Gulf of St. Lawrence

By Hugo Bourdages, Claude Brassard, Mathieu Desgagnés, Peter Galbraith, Johanne Gauthier, Claude Nozères, Caroline Senay, Pierre-Marc Scallon-Chouinard and Andrew Smith

Abstract

Fisheries and Oceans Canada conducts an annual multidisciplinary survey in the Estuary and northern Gulf of St. Lawrence. The objectives of this survey are varied: assess the biodiversity of species found near the sea bottom, estimate the abundance of groundfish and invertebrates, assess physical and biological oceanographic conditions (phytoplankton and zooplankton), monitor the pelagic ecosystem, take inventories of marine mammals and seabirds, and collect samples for various research projects. In 2017, the survey was conducted between August 2 and September 2 on board the CCGS Teleost. The survey successfully carried out 170 trawl tows as well as 105 CTD water column casts, and 73 zooplankton samples.

This report presents the results from catches from the 170 tows. In total, 79 fish taxa and 215 invertebrate taxa were identified during the mission. Historical perspectives (catch rates, spatial distribution and length frequency) are presented for 23 taxa. These commercial fishery-independent data will be used in several stock assessments including cod (Gadus morhua), redfish (Sebastes spp.), Greenland Halibut (Reinhardtius hippoglossoides), Atlantic Halibut (Hippoglossus hippoglossus) and Northern Shrimp (Pandalus borealis).

The increase in the biomass of Deepwater Redfish (Sebastes mentella) is significant, alone, it constituted nearly three quarters of the total catch. The biomasses of several other groundfish species are increasing or exceeding their historical average in the northern Gulf such as Black Dogfish (Centroscyllium fabricii), Atlantic Halibut, Silver Hake (Merluccius bilinearis), White Hake (Urophycis tenuis) and Witch Flounder (Glyptocephalus cynoglossus), while the biomasses of Northern Shrimp, Greenland Halibut and Cod are declining. Capelin (Mallotus villosus) is less present in catches in recent years.

A preliminary analysis of water temperature data collected in 2017 shows that the surface water and cold intermediate layer temperatures were near normal in August. At 150 m depth, the conditions have become less warm than in 2016, remained warm at 200 m and have warmed further at 300 m.

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