Arctic cod (<i>Boreogadus saida</i>) hatching in the Hudson Bay system

Buoyant Arctic cod (Boreogadus saida) eggs are found at the surface or ice-water interface in winter. While winter temperatures saline waters fall below 0°C, temperature areas affected by under-ice river plumes is slightly higher. Under-ice may therefore provide thermal refuges favoring survival of vulnerable early life stages cod. Thermal would allow hatchers to survive, benefit from a long growing period, and add number individuals recruiting adult population: These expectations define freshwater refuge hypothesis. More than 42 rivers drain into Hudson Bay making it particularly well suited test this Whereas bulk observed hatch between mid-April June, some larvae as January. We used two independent but complementary methods hypothesis: (1) Lagrangian model simulations that traced back planktonic trajectories sampled (2) measurements concentration strontium-88 otolith cores. Throughout system, revealed were more likely lower salinities reaching larger prewinter lengths have hatched near within estuaries. Analysis microchemistry showed with low core, indicating salinity location, had earlier thus longer growth period before freeze-up. results show potential for persistence where input projected increase ice regime predicted become seasonal, provided remain embryonic larval lethal limits.