“Things are changing so much, it’s hard to say what’s normal these days”
Marine biologists have documented a rapid shift in key fish species in the Pacific Ocean. Anchovies, sardines and hake started spawning much earlier in the year off the coast of Oregon and Washington. Anchovies are also spawning for a longer period of time than documented previously, the scientists reported in a new study published in the journal Global Change Biology.
The study was focused on the last few years, when a warm blob of water persisted in the northeastern Pacific, and the researchers said the shifts may offer a preview of future conditions if ocean warming continues. The shift means anchovies and sardines became less common off California. In 2015 and 2016, the researchers found the highest concentrations of sardine, anchovy and hake larvae in the Northern California Current, off the Pacific Northwest, than they have in any year since collections began in 1998.
“Changes in spawning timing and poleward migration of fish populations due to warmer ocean conditions or global climate change will negatively affect areas that were historically dependent on these fish, and change the food web structure of the areas that the fish move into with unforeseen consequences,” the study found.
The data was collected off the central Oregon Coast in an area called the Newport Hydrographic Line, where scientists have regularly measured ocean conditions for decades.
Scientists have never collected anchovy, sardine and hake larvae off the Northwest as early in the year as they did through 2015 and 2016, and have never found anchovy larvae throughout as much of the year. The presence of anchovy larvae through almost the entire year indicates the species was spawning nearly continuously through the winter, far longer than its usual summer spawning period in the region, researchers found.
Anchovies and sardines typically spawn offshore, within the Columbia River plume. In the last few years, though, researchers have found their eggs and larvae within about a mile of shore.
“We’re getting these species that usually just spawn off the Northwest in the summer time, and now they’re spawning year-round,” said Ric Brodeur, a NOAA Fisheries research scientist at the Northwest Fisheries Science Center’s research station in Newport, Oregon, and coauthor of the paper. “Things are changing so much, it’s hard to say what’s normal these days.”
Scientists also found larvae of unusual species such as Pacific pompano, which normally spawns in the southern California Current in the spring and summer. It was the first documented occurrence of pompano larvae off Oregon in at least 19 years.
The presence of fish such as anchovy and sardine earlier in the year may provide an additional food source for other species such as young salmon that have just migrated to the ocean, Brodeur said. At the same time, they may also have other impacts on the food web that have yet to be measured, including possibly competing with typical winter-spawning fishes for food.
“As is often the case with ecosystem change, some species may benefit from changes in distribution and timing of prey whereas others may not be able to adapt and subsequently decline,” said Toby Auth of the Pacific States Marine Fisheries Commission and lead author of the paper. “Only through continued, regular surveys will we be able to discern the signals of future anomalies and their relationship to global climate change.”