Newswise — NEWPORT, Ore. –New findings suggest that elevated ocean temperatures, indicative of climate change and more frequent marine heatwaves, may contribute to heightened levels of Chinook salmon bycatch in the Pacific hake fishery.
In periods of elevated sea surface temperatures, such as during a marine heatwave, there was an increased likelihood of Chinook salmon and Pacific hake overlapping. This overlap raised the risk of bycatch as the Chinook salmon sought refuge from the higher temperatures.
According to Megan Sabal, the lead author of the study, the findings, which draw from two decades of bycatch data and ocean temperature records, offer fresh understanding of the ecological mechanisms that contribute to bycatch. Bycatch refers to the unintentional capture of non-targeted species.
Megan Sabal, who participated in the research as a postdoctoral scholar at Oregon State University, emphasized the potential cultural, economic, and ecological implications of ocean warming on bycatch. Both the hake and salmon fisheries hold significant value, amounting to millions of dollars. Moreover, the preservation of salmon is crucial for maintaining the cultural heritage of Indigenous tribes and ensuring the health of ecosystems.
Michael Banks, a co-author of the study and a professor specializing in marine fisheries genomics, conservation, and behavior at Oregon State University, highlighted the significance of Pacific hake, also known as Pacific whiting, as the largest commercial fishery by tonnage on the U.S. West Coast. While the bycatch rate is currently low, the welfare of the Chinook salmon population remains a concern in relation to bycatch.
“The hake fishing industry is very sensitive to the impacts of bycatch on salmon and has been diligent in reducing it, but changing climate conditions might become an increasing issue,” he said.
The research was just published in the journal Fish and Fisheries.
Pacific hake school in midwater depths off the West Coast from southern Baja California to the Gulf of Alaska. Hake is commonly used in surimi, a type of minced fish used to make imitation crab.
The researchers pointed out that the majority of hake fishing activities take place at depths ranging from 200 to 300 meters, whereas Chinook salmon typically inhabit shallower depths. Therefore, if alterations in water temperature influence the distribution of salmon, there is a possibility of increased salmon bycatch.
Kate Richerson, a co-author from the National Oceanic and Atmospheric Administration's Northwest Fisheries Science Center Newport Research Station, emphasized the importance of developing a mechanistic understanding of how environmental conditions can influence bycatch. Such understanding can aid in future preparedness and facilitate the adaptation of current strategies to cope with a changing world.
To gain a deeper comprehension of the effects of evolving ocean conditions, the researchers utilized a wealth of data spanning 20 years, obtained through NOAA's At-Sea Hake Observer Program. This program involves placing observers on hake catcher-processor vessels and motherships, where they document crucial information about fishing depth and location, species composition, and other relevant details related to the catch that is received and processed.
Sabal and her coauthors modeled observer data and genetic stock identification to show salmon moving lower into the water column during higher temperatures.
“These behavioral changes can provide important information for researchers and can also inform creative conservation solutions,” Sabal said.
Additionally, the researchers discovered that restricting night fishing, which is a common strategy employed to mitigate bycatch, is expected to become less effective when there are warmer sea surface temperatures near the surface. This finding suggests that alternative approaches or adaptations may be necessary to effectively address the issue of bycatch during periods of elevated surface temperatures.
Based on the findings, Michael Banks emphasized the need for the development of new strategies to mitigate bycatch in the hake fishery. He proposed that advancements in technology could enable fishermen and fishery managers to forecast the impacts of bycatch using real-time ocean condition information. This, in turn, would facilitate adaptive management decisions, allowing fishing strategies to be adjusted based on the prevailing conditions. Such an approach could enhance the effectiveness of bycatch mitigation efforts in the hake fishery.
“As the oceans and the world are changing, the conflict between the two fisheries is showing up in new ways,” he said, “and we may need to shift strategies based on this understanding.”
Michael Banks holds affiliations with both the Department of Fisheries, Wildlife, and Conservation Sciences in the College of Agricultural Sciences and the Coastal Oregon Marine Experiment Station at Hatfield Marine Science Center, both of which are part of OSU (Oregon State University). Megan Sabal, during her involvement in the project, was affiliated with the Cooperative Institute for Marine Ecosystems and Resources Studies and the Coastal Oregon Marine Experiment Station. Currently, Sabal serves as a quantitative fisheries scientist at the Oregon Department of Fish and Wildlife.
In addition to Michael Banks and Megan Sabal, other co-authors of the study include Taal Levi from OSU's College of Agricultural Sciences, as well as Paul Moran and Vanessa Tuttle from NOAA's Northwest Fisheries Science Center in Seattle. Their contributions and expertise further enriched the research findings.
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