Impact of the 2012 Ocean Heat Wave on Fish and Fisheries

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In 2012, a vast stretch of the North Atlantic was more than 1°C warmer than normal. This “ocean heat wave” was the largest, most persistent sea surface temperature anomaly ever recorded in this region. The Gulf of Maine was at the apex of this event, with surface and subsurface temperature anomalies exceeding 3°C for much of the year. The conditions during this event were similar to the mean conditions expected by the end of the century. The response of fish and invertebrate populations to this event differed depending on their mobility. Warm-water fish and squid not normally found in the Gulf of Maine rapidly expanded northward. Less mobile species such as American lobsters exhibited a marked change in their phenology. Temperatures in the Gulf of Maine also reached levels that would be stressful to cod, challenging the recovery of this stock. The northwest Atlantic is currently warming faster than any other region in the global ocean. Experience in 2012 suggests that shorter-term events could be more important than changes in the mean.