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Deepwater redfish Sebastes mentella will be among the most important resource-sustaining commercial bottom-fish fisheries in the years to come in the Estuary and Gulf of St. Lawrence (EGSL). In 2011, 2012, and 2013, three strong cohorts were recruited to the stock; their abundance in 2018 was 80 times higher than that of the 1993–2012 period. The main goal of this work was to deepen our knowledge of their growth regulation and metabolism in order to identify molecular indicators and determine how they are influenced by natural environmental conditions. Fish weight and water temperature explained 11% of the variation in relative mRNA levels of specific gene targets in liver and muscle among seven sites where deepwater redfish were captured in the EGSL. The relative expression of liver insulin-like growth factor-1 (igf-1) and white muscle A-chain lactate dehydrogenase (ldh-a) correlate positively with weight, whereas heavy chain muscle myosin (myo), heart citrate synthase (cs), and white muscle pyruvate kinase (pk) correlate negatively. The relative expression of heart cytochrome c oxidase subunit 1 (cox-1) and white muscle igf-1 receptor isoform a (igf-1ra) correlate negatively with temperature. Deepwater redfish from the estuary were smaller than those caught at other sites. Since the growth potential of deepwater redfish was strongly correlated with temperature (being enhanced by higher temperatures), this study suggests an ecological advantage for this species in a climate-warming context. [ABSTRACT FROM AUTHOR]

Climate change has led to major shifts in the timing of biological events, with many studies demonstrating earlier phenology in response to warming. However, few of these studies have investigated the effects of climate change on the phenology of larvae in marine species. Phenological shifts can result in mismatches between consumers and prey and hence affect growth and survival of individuals, and ultimately population demography. We investigated the temporal changes in phenology and abundance of the larvae of dominant brachyuran crabs in the southern Gulf of St. Lawrence (eastern Canada) based on plankton collections spanning 1982–2012. The Gulf of St. Lawrence has warmed since the early 1990s, and our analyses revealed that larvae of snow crab (Chionoecetes opilio) and toad crabs (Hyas spp.) exhibited a significant trend towards earlier phenology over the 30‐year study period. This shift in phenology appeared to be a consequence of the effect of climate warming on both the timing of hatching and larval development rate. Larval abundance responded differently by crab taxon to climate warming, likely due to differences in thermal tolerance. The warming trend was unfavourable to snow crab, which is the most cold‐adapted and stenothermic of the taxa examined in this study. The abundance of snow crab larvae was lower when sea ice retreat occurred earlier than day 110 of the year and sea surface temperature was higher than 8.5°C. On the other hand, larval abundance of rock crab (Cancer irroratus), which prefers higher temperatures, was positively related to surface temperature. [ABSTRACT FROM AUTHOR]

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 fisheryindependent 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. [ABSTRACT FROM AUTHOR]