Research shows that black rockfish are affected by marine heat wave but not always for the worse

New research from Oregon State University shows that fry produced by black rockfish, a main focus of the West Coast’s commercial fishing industry for the past eight decades, fared better during the last two years from unusually high ocean temperatures than feared.

“The study is important for gauging conditions and developing management plans that will impact species survival as the ocean faces increased variability due to climate change,” said Will Finney, lead author of the study.

The results have been published in Nature’s Journal Scientific reports.

Rockfish, a diverse genus with many species, is a group of ecologically as well as economically important fish found from Baja California to British Columbia.

They are known for lifespans that can reach triple digits, the ability to produce huge numbers of offspring and to survive through their early life stages, during which they are extremely sensitive to environmental conditions.

“Oceanographic conditions dictate water temperature, which affects larval dispersal and food availability — and this affects the early development and survival of fish larvae,” Finney said. “Larval survival and subsequent performance can influence later life stages – for example, rapid larval growth contributes to increased survival of juveniles after settling on stony reefs.”

Finney, a former Oregon State doctoral student now with the National Oceanic and Atmospheric Administration, worked with University of Oregon College of Science researchers Sue Sponogle and Kirsten Groud Culvert on the study.

The research involved analysis of samples of juvenile black rockfish collected during a long-standing collaboration between Oregon State, the Oregon Department of Fish and Wildlife, and the Oregon Coast Aquarium. Samples were collected near shore from 2013 to 2019, a time frame that included a marine heat wave between 2014 and 2016.

“The goal was to shed light on how oceanographic conditions affected the early growth and survival of the black rockfish,” Finney said. “We found that despite concerns about the blues with the recent anomalous warming of the waters off the Oregon coast, some black rockfish grew faster as the temperature rose, and surprisingly there was high and low survival during different years of the heatwave.”

He added that survival was the highest in years that were characterized by moderate larval growth rates, low predation and sufficient food to support growth. When growth was at its highest, rockfish survival was very low, likely due to a lack of food to sustain such high growth.

According to ODFW. It is dark gray to black above, with a lighter belly, and has black spots on its dorsal fins. An adult black rockfish can reach over 2 feet in length.

Starting at about the age of five, the female can release thousands of swim-able larvae at a time. As they develop and grow, young fish are an important food source for a range of predators.