2019 was a bad year for salmon returns coast-wide in British Columbia, and an international team of scientists has been trying to figure out why. This March, the research team travelled back to the open Pacific for a second expedition to study the ocean survival of salmon, and this year CCIRA’s Field Technician, Tristan Blaine, joined the expedition.
Tristan was part of a team composed of leading salmon researchers from Canada, USA, Russia, Japan and Korea. Together they surveyed 697,500 km2 of the Pacific Ocean looking for salmon. “It was amazing to see researchers from all over the Pacific working together so well,” says Tristan, who was contributing by processing salmon samples, putting cameras in the nets, drone work, and processing any shark bycatch.
The major objective of the research is to identify the mechanisms that control salmon survival in the open ocean. One working hypothesis is that total adult salmon abundance is influenced by the number of salmon that survive to the end of their first year in the sea. The researchers suspect this is strongly tied to the production and timing of the things that salmon eat. But, as our climate changes, scientists have a lot to learn about the implications of the corresponding changes in ocean conditions and how they affect things like salmon and their food. This expedition was striving to fill in some of those knowledge gaps and conducting this research with our neighbours in the Pacific makes sense for fish that cross borders.
“It was incredible to be out there with leaders in the field,” says Tristan. “These scientists are amazing. They can identify salmon from a distance by sight. It was incredible to see how much they know about salmon and all the other species we caught. And, yet,” he says, “at the end of the day we’d sit down to have cookies and coffee and we would talk about how nobody knows anything about where the salmon are going in the open Pacific and what they’re doing.”
In absolute numbers the 2020 research expedition caught slightly more fish than in 2019. But the distribution of the catches was vastly different. “In 2019, they caught small numbers of fish, say, 10 or 20, in the majority of their tows,” explains Tristan. In essence they caught small numbers of fish just about everywhere they went. By contrast, in 2020 they came up empty in the majority of their tows but had some catches of up to 300 salmon in a single tow. “The differences in the distribution of catches between the two expeditions really highlights how much we still need to learn about open ocean salmon survival,” says Tristan. “We just don’t know what is normal, or what we should expect to find out there, and we really need to understand these things better if we want to manage the fishery well.”
Featured photo of pink salmon by Ilja Herb https://www.iljaherb.com/