New research shows juvenile rockfish boomed during “the blob”

Pacific Ocean Perch is a common species of rockfish. (Photo by Kathy Hough for NOAA)

“The blob” is the ominous nickname used by fishermen and marine biologists to describe warm ocean conditions that appeared in the North Pacific in 2014. It lingered for about two years and the negative impacts on Alaska’s marine ecosystem were widely reported. But for some species, it wasn’t a bad thing. New research indicates that young rockfish were thriving during this period.

Pacific rockfish were drastically overfished up and down the West Coast in the 20th century. In Alaska, most of the fleet wasn’t local. 

“You know our story is a little bit different,” says Pete Hulson, a biologist with NOAA Fisheries in Alaska. “Up here the story is more like the Japanese fleets and Russian fleets decimated not just Rockfish but most of our groundfish species.”

Rockfish numbers have rebounded thanks in part to careful management. Fisheries managers have slowly increased commercial catch limits. Although it is not the most valuable fish, rockfish now make up a sizable amount of the trawl catches in Kodiak and the Western Gulf of Alaska. 

Hulson says it isn’t just management practices that led to the rebound in the population.

“I mean of course we would love to pat ourselves on the back,” Hulson says. “But I don’t think we can say it’s just that. I think there’s definitely been some natural environmental things that have occurred that helped the population.”

Oregon Scientists are now investigating how “the blob” led to a banner year for juvenile rockfish. 

During “the blob’s” final months in 2016 researchers at NOAA’s Northwest Fisheries Science Center noticed dramatic changes in the ecosystem off the Oregon Coast. Laurie Weitkamp, a researcher with the Northwest Fisheries Science Center, says that while she was conducting a survey of Chinook salmon she was struck by the changes she was seeing in other marine species. 

“If you tow a net out in the ocean you catch a lot of other stuff besides salmon,” Weitkamp says. “It was really these other species that it was like wow that’s really different.”

Weitkamp says her net was getting clogged by all sorts of unusual creatures.

“For example, one of the things we started catching are pyrosomes,” Weitkamp says. “Sea pickles, I guess.”

She noticed high numbers of juvenile rockfish as well.

“We just had this big bloom of those, and talking to researchers up and down the coast from California to British Columbia and up into Alaska even, other people were seeing the same event.” 

Weitkamp and her colleagues recently published a paper on their findings. They suggest that a decline in jellyfish that eat juvenile rockfish helped their numbers.

Hulson says that while Alaska experienced the same spike in juvenile rockfish in 2016, it’s unclear if it had anything to do with other species. 

“I don’t think we have a good understanding of why rockfish seem to be doing well in these conditions and these other fish don’t,” Hulson says. “It seems to be coinciding with these warming temperatures. What the mechanisms of that is we don’t really know. It at least kind of points us in a direction that we can start asking more questions and doing a little bit more research.”

Other groundfish species such as sablefish experienced a similar boom during the blob. Fishermen are already looking at ways to protect them until they reach maturity and can be sold commercially.

Hulson says at this point, the increase in juvenile rockfish hasn’t had any impact on the way Alaska’s fisheries are managed. Rockfish can live upwards of 100 years, and it takes a long time for them to grow to adulthood. Stock assessments for commercial fisheries focus more on adult rockfish populations. 

Weitkamp says that unprecedented ocean conditions make it difficult to make predictions about the future of commercial fisheries. 

“With these recent unusual conditions there’s winners and losers. You know we’re expecting predictable resources that we’ve harvested for millennia in the case of lots of people on the coast. Things are changing in ways that we don’t really understand. Some things are doing good and others not so much,” Weitkamp says.

If these rockfish numbers keep increasing, the species might just be an unexpected winner.