Southern Newfoundland Waters Under Changing Ocean Conditions: Dietary Analysis of Emerging and Re-Emerging Gadoids within Northwest Atlantic Fisheries Organization Division 3Ps

In marine ecosystems, climate-driven alterations of competition, growth rates, and size-specific predation rates influence population and community structure. In Newfoundland and Labrador waters, the warmest, most spatially variable sea temperatures occur off the south coast of Newfoundland. This region contains complex temperature and species richness gradients spanning cold (<1°C) shallow shelf habitats to warmer (4-7°C) shelf slopes. Recent increases in this region’s bottom temperatures have reduced thermal habitat areas <0°C and increased areas >2°C. This warming may lead to the establishment of species that favour warmer temperatures, with potential implications for resident species. Acoustic-directed bottom trawls conducted aboard the RV Celtic Explorer in 2012 and 2013 yielded samples of haddock (Melanogrammus aeglefinus), pollock (Pollachius virens), and silver hake (Merluccius bilinearis). These gadoids are typically more abundant further south and near their northern range limits in this area. Analysis of stomach contents and spatial distributions of four gadoids (including resident Atlantic cod, Gadus morhua) quantified potential competition and predation among these species. Stomach contents help estimate functional overlap among Atlantic cod, and three ‘southern’ species. We explored the extent to which these three species could alter ecosystem dynamics and affect the economically important Atlantic cod fishery in the area.