How does the alaska blackfish survive in waters with temperatures of 5ºf?

Alaska blackfish have the ability to survive in harsh conditions, they can live in temperature range of  5ºF because of certain adaptations. They live in benthic zone which has low amount of dissolved oxygen. When the amount of oxygen is too low it comes on the surface for the oxygen. Most of the fishes becomes inactive to save their energy and to slow down their metabolic processes.

Thus, the ability to survive in low concentration of oxygen helps them to survive at this temperature.