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Sunday, March 11, 2018

Friday in Rohnert Park, California, the Southwest and Northwest Fisheries Science Centers presented findings showing that the two-year heat wave in the waters off the northwest coast of North America is subsiding and discuss its implications for fishing and ecosystems.

“Overall we’re seeing some positive signs, as the ocean returns to a cooler and generally more productive state,” said co-author Dr. Toby Garfield and Acting Director of the Southwest Fisheries Science Center. “We’re fortunate that we have the data from previous years to help us understand what the trends are, and how that matters to West Coast fishermen and communities.”

In 2014, a continent-spanning pocket of warm water nickednamed “the Blob” hit the west coast. It was followed in 2015 by an unusually strong El Niño, a water current that often forms after Christmas, named after the Spanish-language term for the Christ Child. This caused alterations in the populations of many types of marine organisms. Among other issues, colder water can hold more oxygen, and large pockets of low-oxygen water formed, one very substantial one off the coast of Oregon. Whales began to follow their prey closer to shore, which caused run-ins with fishing equipment. Plankton communities, specifically copepods, shifted toward leaner species that provided poorer fodder for commercially important fish, such as salmon, but they are now shifting back to cold-water phenotypes.

Although salmon populations did not appear to have returned to pre-Blob levels, researchers cautioned that the fish’s long lifespan suggests a lag of about three years behind improvements in its environment and food supply.

Among other indicators, researchers also noted that sea lions on San Miguel Island produced normal numbers of pups, which scientists say means the mothers were able to eat enough prey to keep them nursed and that the prey consisted of more preferable species, such as anchovies and hake rather than market squid and rockfish that the sea lion mothers scrounge up in leaner times.

The report also preliminarily discusses changes in the yields of yellowfin tuna, yellowtail and other edible fish by human fishing projects and their social implications for coastal communities economically dependent on fishing. It concludes by recommending an early warning system for changes in ocean current and a program of dynamic bycatch management to prevent endangered loggerhead turtles and other vulnerable species from falling prey to fishing systems.

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