Research Document 2019/037

Preliminary results from the groundfish and shrimp multidisciplinary survey in August 2018 in the Estuary and northern Gulf of St. Lawrence

By Bourdages, H., Brassard, C., Desgagnés, M., Galbraith, P., Gauthier, J., Nozères, C., Scallon-Chouinard, P.-M. and Senay, C.

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 (phytoplankton and zooplankton) oceanographic conditions, monitor the pelagic ecosystem, take inventories of marine mammals and seabirds, and collect samples for various research projects. In 2018, the survey was conducted between August 2 and September 2 on board the CCGS Teleost. The survey successfully carried out 168 trawl tows as well as 109 CTD water column casts, and 73 zooplankton samples.

This report presents the results from catches from the 168 tows. In total, 93 fish taxa and 230 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 Acadian Redfish (Sebastes fasciatus) and Deepwater Redfish (Sebastes mentella) is significant; they alone accounted for more than 80% of the catches. 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), Longfin Hake (Phycis chesteri) and Witch Flounder (Glyptocephalus cynoglossus), while the biomasses of Northern Shrimp and Greenland Halibut are decreasing.

A preliminary analysis of water temperature data collected in 2018 shows that conditions were slightly warmer than normal at 150 m and 200 m depth, and have warmed further at 300 m. The surface water and cold intermediate layer temperatures were near normal in August.

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