Some fish, like herring and whiting, are moving toward the polar regions in search of cooler water. Sudden warming can decimate these fisheries. They need stable water temperatures within specific ranges to spawn and maintain healthy populations.
Other fish, like black seabream, are moving away from coastal areas into deeper water, which can further environmental injustices. This can have a profound effect on small-scale, artisanal fishers, who don't have vessels equipped for longer distance, deepwater fishing—deepening inequities between under-resourced coastal communities and large-scale industry.
Species that live or spawn in coastal habitats, like mangrove forests and coral reefs, can die off. For example, coral bleaching events from warm, acidified water have been found to affect the behavior and nutrition of reef fish like butterflyfish, which in turn impact the surrounding wildlife and the dynamics of the whole ecosystem.
Species that already live in deep, cold waters are disappearing. The Alaska snow crab fishery collapse earlier this year had complex causes, but NOAA confirms that factors related to "heatwave conditions," even as deep as the ocean floor in the Bering Sea, contributed to the die-off.
Marine mammals and seabirds are affected, too. There are hundreds of thousands of other non-human species like whales and other marine mammals that feed on migrating fish and other prey species like krill that now have to travel much longer distances to find food, and are potentially experiencing challenges in birthing and rearing their offspring. Bird species that are consumed by subsistence-based communities, like auklets, can also experience mass die-offs as the location of their marine food sources move away from historical locations. And species that rely on sea ice for hunting food, like polar bears, are particularly vulnerable as seas warm.