Satellites track tiny silvery fish of enormous importance to marine life

A new scientific effort has taken to the skies using high-tech drones and satellite images to better understand the annual spring herring spawning, vital for salmon and wildlife on the West Coast.

Between February and March each year, the frigid ocean waters transform into a tropical-looking milky turquoise green as male herrings release milk to fertilize the countless eggs laid by the females in seagrasses, kelp and kelp that line the coasts. coastal.

Unpredictable and dramatic, the small silverfish spawning event is large and best monitored from high altitudes, said Loïc Dallaire, a researcher at the University of Victoria’s SPECTRAL Remote Sensing Laboratory.

“It’s one of the few animal formations we can see from space, excluding human developments and cities,” Dallaire said.

“The idea behind remote sensing (technology) is to be able to monitor huge areas while spending less money than large field expeditions that are very, very expensive.”

Dallaire has been rushing to areas of the east and west coasts of Vancouver Island to obtain drone images and scientific samples at spawning events over the past few weeks.

Their work will help unravel how and why spawning distribution has changed and declined over time as part of a larger study of herring and their habitat being conducted by the Pacific Salmon Foundation (PSF) through 2026.

The collaborative research project, which also involves First Nations coastal communities, will address Key knowledge gaps on herring ecology and the importance of their role in the Strait of Georgia, particularly for salmon.said Jess Qualley, project manager for the PSF studio.

Herring is a small forage fish with a huge role in the marine food web and is important not only for juvenile and adult salmon, but also for a host of animals such as whales, sea lions, eagles and seabirds, Qualley said.

A new scientific effort has taken to the skies using high-tech drones and satellite images to better understand the annual spring herring spawning, vital for salmon and wildlife on the West Coast.

The PSF study will also examine how changes in herring spawning events could affect the availability of those minnows as a food source for juvenile salmon, Qualley said.

Another line of research involving Qualley’s scientific work aims to learn more about non-migratory or resident herring populations that live in the Strait of Georgia year-round and their importance in the food web under the stress of climate change and other pressures.

The study will incorporate traditional ecological knowledge about the past abundance of herring and how it influenced the traditions, distribution and settlement of coastal First Nations in the region.

Once-abundant herring populations spread along the British Columbia coast missing in the southern Salish Sea following colonial industry and development in the Lower Mainland.

Overfishing led to the near collapse of other herring stocks along the coast in the 1960s, followed by a brief period of recovery and a subsequent continued decline in herring stocks beginning in the 1990s. has led to the closure of commercial fisheries on the Central Coast, western Vancouver Island and Haida Gwaii.

The only remaining region with an extensive commercial herring fishery is in the Strait of Georgia off the coast of central Vancouver Island, stretching roughly from Nanaimo in the south to the waters north of Comox.

Herring eggs laid on seaweed after spawning. Photo by Loïc Dallaire / Pacific Salmon Foundation and UVic SPECTRAL Remote Sensing Lab

It’s still unclear what specific factors are preventing herring populations from recovering in each coastal region, Qualley said.

In addition to fishing pressures, the cumulative effects of climate change (warmer, more acidic and less oxygenated oceans, changing food sources and more extreme weather conditions in tidal zones), together with the loss of key habitat for human development and concerns about water quality from urban areas and wastewater runoff may be affecting herring, research suggests.

In some cases, herring can adapt or benefit from changes in the marine ecosystem, Dallaire said. While critical seagrass nurseries are declining in some regions, herring appear to be taking advantage of a invasive algae called Japanese sargassum as a new place to lay eggs, he said.

To fill gaps in knowledge about how herring spawning has changed over decades, Dallaire plans to analyze archives of coastal satellite images dating back to the 1980s along with historical data from Fisheries and Oceans Canada (DFO). .

Aerial surveys conducted by DFO tend to focus on spawning events in major commercial fishing areas, Dallaire noted.

However, it is likely that satellite imagery can detect and track smaller or more transient spawning events along British Columbia’s extensive coastline that might be overlooked but are important to First Nations eager to document the activity. of herring in their territories.

In addition to analyzing the role of herring in salmon food webs, the PSF project will help discover what causes variability in the size and location of spawning events, Qualley said.

“Why do some herring select certain habitats and not others? That’s an unknown question,” she said, noting that spawning can sometimes be unpredictable and surprising.

Seabirds, including common terns, flocked to Cortes Island to gorge on herring eggs that washed ashore after a storm. Photo by George Sirk.

This year, much of the herring spawning in the Central Strait of Georgia bucked a years-long trend and emerged farther south, near the Qualicum area, after largely taking place in waters near the Comox Islands and Hornby and Denman.

The waters off Cortés Island, which normally experience infrequent spawning events, were a hive of activity this spring, said biologist Sabina Leader Mense, marine management coordinator for the Society of Friends of Cortés Island (FOCI).

A major spawning event occurred on the southern tip of the island on March 6, followed by a series of strong storms that stirred up masses of eggs laid on seaweed and dumped them centimeters deep onto the surrounding beaches.

Studies will likely be conducted to try to determine the degree of damage to spawning and eggs in the island’s tidal zone, Mense said.

naturalist and Radio Cortés host George Sirk said it was the most abundant herring spawning. had seen in the 50 years he had lived on the island and the seabirds flocked to the feast.

Centimeters-deep herring eggs were washed ashore by storms off southern Cortes Island after a large spawning run on March 6. Photo by George Sirk

Dallaire agreed that herring spawning is a natural spectacle that causes a flurry of activity among humans and wildlife alike.

Witnessing the event live while doing field work and collecting samples to confirm what is happening on the ground with information from satellite and drone images is a great thrill.

“The fish were jumping out of the water while the sea lions were coming from below and the seagulls were coming from above,” he said.

Up to 30 commercial fishing boats surrounded the colorful waters off Qualicum, as people gathered along the beach to watch or cast nets into the shallow waters to catch herring, he said.

“It was very, very impressive to see all this happening in the same place and at the same time. It’s kind of the beginning of summer.

“It’s a real party.”

Rochelle Baker / Local Journalism Initiative / Canada’s National Observer

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