International Year of the Salmon Expedition helps IOF researchers map North Pacific food webs

Researchers from UBC’s Institute for the Oceans and Fisheries (IOF) who participated in the International Year of the Salmon (IYS) 2022 Pan-Pacific Expedition returned recently with a trove of important data and samples in tow. What they collected will expand our knowledge of the critical and poorly understood open ocean life stage of North Pacific salmon.

For scientists in the IOF’s Pelagic Ecosystems Lab, the trip represents a chance to trace the outline of North Pacific food webs, in which salmon play a central role as both predator and prey.

“Food web models illustrate the important components of ecosystems, and how different species that share the same space interact with one another through what they eat,” said Genyffer Troina, a postdoctoral fellow who travelled through the Gulf of Alaska on American ship NOAA Bell M. Shimada.

By getting a clearer picture of who is eating who in the North Pacific, the research team will better understand how salmon populations are affected by heat waves and other climate-change driven problems that may deplete salmon prey, or render salmon prey less nutritious.

Troina is using two biochemical tools – stable isotopes and fatty acids – in pursuit of this mission. These two “biomarkers” are like fingerprints that can reveal what an organism has been eating, and can be used to map out the North Pacific food web, from plankton to salmon.

Early insights from the trip have already begun to shape the questions that will guide Troina’s work in the coming months.

“We saw that the catch was either dominated by a lot of different species of jellyfish and then only a few salmon and not much else,  or almost no jellyfish at all and then a lot of juvenile squid and forage fish, some krill, some bigger squids, and more salmon,” she said. “What is driving that difference in the dominance of species? Does it relate to temperature, or is there a missing competitor in the jellyfish-dominated ecosystem?”

While Troina is busy modelling the food web, Anna McLaskey, another Pelagic Ecosystems Lab postdoctoral researcher, will be looking into the nutritional value of some species inhabiting the North Pacific.

Specifically, McLaskey wants to understand how zooplankton are affected by nutritional changes to phytoplankton, the ocean plants on which zooplankton feed. These nutritional changes may work their way up to salmon and other fish that prey on zooplankton.

The data collected on the IYS trip will help to produce a map of how the nutritional value of zooplankton  varies across the North Pacific. Since zooplankton are the cornerstone of salmon’s diet, this information is key to understanding spatial differences in salmon health.

“It’s interesting being able to cover all of that space in a couple weeks and see the differences in the zooplankton communities, especially north to south,” said McLaskey, who was on board Canadian ship CCGS Sir John Franklin.

During the easternmost section of the Pacific leg of her journey, McLaskey inspected salmon stomachs to see exactly which zooplankton the fish were consuming.

“It was really cool to see the specific zooplankton we research,” she said. “All of these different zooplankton are important, not just one species.”

For Brian Hunt, the principal investigator of the Pelagic Ecosystems Lab, the IYS expedition is a rare opportunity to collect data from the open ocean, and least-known life stage of Pacific Salmon. It will be crucial for understanding how salmon respond to climate change.

“You are what you eat. Without healthy food webs, salmon will not get the nutrition they need. This means that they won’t grow well, they will have less speed to escape predators, they will be more susceptible to disease, they are more likely not to successfully make it back to their spawning rivers, and will produce less healthy eggs and young,” Hunt said. “That’s why we care about the food web.”

Now that the expedition is finished, Hunt thinks that the team will start to uncover new findings by as early as this summer.

“We’ve been working towards these expeditions for three years,” he said. “It’s a big endeavour, and it takes a lot of people just to organize the logistics and collect samples. You can’t do something like this as an individual— it’s a team effort. Now we move into the lab phase, which is really exciting. It feels as though every sample yields new information, and we are slowly shedding light on this ocean life stage that has always been thought of as a black box.”
 

 
Tags: Anna McLaskey, Brian Hunt, Faculty, food webs, Genyffer Troina, Gulf of Alaska, International Year of the Salmon, IOF postdoctoral fellows, jellyfish, plankton, Research, salmon, squid, zooplankton