Is Ocean Warming Changing the Spatial Distributions and Abundances of Gadoids in Southern Newfoundland Waters?

Climate-driven shifts in spatial and depth distributions can lead to restructuring of marine ecosystems, changes in community composition, and local-to-regional colonization and extinction. Therefore, quantifying distributional shifts is important for understanding species interactions, population management, and conservation. Given strong gradients in bottom temperatures, the shelf, slope, and channel waters immediately south of the island of Newfoundland represent a known thermal transition zone that contains the northern range endpoints of multiple gadoid species. Using acoustic-directed bottom trawl spring surveys conducted across shelf slopes and channels, the distributions and local abundances of ‘southern’ gadoids pollock (Pollachius virens) and silver hake (Merluccius bilinearis) were studied in a region that previously housed large abundances of haddock (Melanogrammus aeglefinus) and was historically dominated by Atlantic cod (Gadus morhua). We quantified recent biophysical changes in this system where Atlantic cod’s dominance has decreased and where in 2014, silver hake replaced Atlantic cod as the dominant piscivore. Silver hake has been used as a climate indicator species in adjacent regions and as the increase in its biomass has led to stakeholder interest in pursuing a fishery in this region, this study will provide insights for management.