Warmer ocean temperatures increase risk of salmon bycatch in Pacific
hake fishery

Date:
July 12, 2023
Source:
Oregon State University
Summary:
Rates of Chinook salmon bycatch in the Pacific hake fishery rise
during years when ocean temperatures are warmer, a signal that
climate change and increased frequency of marine heatwaves could
lead to higher bycatch rates, new research indicates.


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FULL STORY ========================================================================== Rates of Chinook salmon bycatch in the Pacific hake fishery rise during
years when ocean temperatures are warmer, a signal that climate change
and increased frequency of marine heatwaves could lead to higher bycatch
rates, new research indicates.

During years when sea surface temperatures were higher, including during
a marine heatwave, Chinook salmon were more likely to overlap with the
Pacific hake and raise the risk of bycatch as they sought refuge from
higher temperatures.

The findings, based on 20 years of bycatch data and ocean temperature
records, provide new insight into the ecological mechanisms that underlie bycatch, which is the incidental capture of a non-targeted species,
said the study's lead author, Megan Sabal.

"The impact of ocean warming on bycatch has potential cultural, economic
and ecological consequences, as the hake and salmon fisheries are each
worth millions of dollars and salmon are critical to both Indigenous
tribes' cultural heritage and healthy ecosystems," said Sabal, who worked
on the project as a postdoctoral scholar at Oregon State University.

Pacific hake, also known as Pacific whiting, is the largest commercial
fishery by tonnage on the U.S. West Coast. The rate is low but bycatch
remains a concern for the Chinook salmon population, said Michael Banks,
a marine fisheries genomics, conservation and behavior professor at
Oregon State University and a co-author of the study.

"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.

Most hake fishing occurs at depths of 200 to 300 meters and Chinook salmon typically occupy more shallow depths. If changing water temperature
affects salmon distribution, that could increase salmon bycatch, the researchers noted.

"Developing a mechanistic understanding of how environmental conditions
might impact bycatch can help us prepare for the future and think about
how to adapt current strategies to keep up with a changing world,"
said co-author Kate Richerson of the National Oceanic and Atmospheric Administration's Northwest Fisheries Science Center Newport Research
Station.

To better understand the impacts of changing ocean conditions, the
researchers tapped into 20 years of data collected through NOAA's At-Sea
Hake Observer Program. Observers are placed aboard hake catcher-processor vessels and motherships that receive catch to process and record
information about fishing depth and location, species composition
and more.

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.

The researchers also found that limiting night fishing, a common
mitigation strategy to reduce bycatch, will likely become less effective
when sea surface temperatures are warmer near the surface.

The findings suggest that new strategies may be needed to continue
mitigating bycatch in the hake fishery, Banks said. As technology
improves, fishermen and fishery managers might be able to forecast bycatch impacts based on real-time ocean condition information and make adaptive management decisions about fishing strategy based on those conditions.

"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." Banks is affiliated with
OSU's 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. Sabal was affiliated with
the Cooperative Institute for Marine Ecosystems and Resources Studies
and the Coastal Oregon Marine Experiment Station while working on the
project and now works for the Oregon Department of Fish and Wildlife as
a quantitative fisheries scientist.

Additional coauthors are Taal Levi of OSU's College of Agricultural
Sciences and Paul Moran and Vanessa Tuttle at NOAA's Northwest Fisheries Science Center in Seattle.

* RELATED_TOPICS
o Plants_&_Animals
# Fish # Fisheries # Marine_Biology # Sea_Life
o Earth_&_Climate
# Oceanography # Environmental_Awareness # Global_Warming
# Climate
* RELATED_TERMS
o Fishery o Atlantic_salmon o
Attribution_of_recent_climate_change o Salmon o Coho_salmon o
Population_dynamics_of_fisheries o El_Nin~o-Southern_Oscillation
o Global_warming

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Story Source: Materials provided by Oregon_State_University. Original
written by Michelle Klampe. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Megan C. Sabal, Kate Richerson, Paul Moran, Taal Levi, Vanessa
J. Tuttle,
Michael Banks. Warm oceans exacerbate Chinook salmon bycatch in
the Pacific hake fishery driven by thermal and diel depth‐use
behaviours. Fish and Fisheries, 2023; DOI: 10.1111/faf.12775 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230712124601.htm

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