Winter fieldwork – Not for the faint of heart

The season began with steady winds, cold rain, and a lot of waiting. But as the end of 2025 approached, weather windows finally opened up to allow Ocean Wise’s field research team to get back out on the water and start collecting data.

This winter the goal is to survey the Salish Sea and, if we’re lucky, collect prey and environmental DNA (eDNA) samples from Resident killer whales to better understand what they’re eating in winter, a season we know far less about.

This work builds on a project Ocean Wise launched in 2023 to address key winter data gaps identified in recovery strategies for at-risk whales in the region, namely the endangered Southern Resident killer whales and threatened Northern Resident killer whales. Historically, Southern Residents relied heavily on the inner Salish Sea during summer months, following Chinook salmon runs toward the Fraser River. As those salmon stocks have declined, so has the whales’ summer presence. Fall and winter are now proving to be increasingly important seasons, as whales target winter salmon in the region.

Prey Sampling – No Easy Feat

With short days, rougher weather, and fewer reliable sightings reports, just finding the whales can be a challenge in its own right. In winter, they’re often spread across the Strait of Georgia searching for prey. Patience is everything: waiting, scanning, and watching for subtle shifts in behavior that signal a hunt.

When a feeding opportunity appears, it becomes a race against time. The vessel must move close to the action, but far enough away so as not to disturb the chase. Once the whale has secured the fish, we can carefully approach the area hoping to find those shimmering salmon scales before they sink. Every time the surface skimmer comes up with a scale, there’s a surge of excitement on board. These winter prey samples are critical for understanding which fish are drawing whales into the Salish Sea, helping to inform good conservation priorities.

Following the Clues in Every Scale: What Resident Whales Are Eating

Since 2023, we’ve collected 15 prey samples from both Southern and Northern Resident killer whales. The Northern Resident A5 pod, in particular, regularly visits these southern waters in winter, making short trips to the Sunshine Coast. Over the past two years, we’ve been able to take advantage of those visits and gather valuable data.

Field collection is only the first step. Samples preserved in ethanol are sent to Fisheries and Oceans Canada’s Pacific Biological Station on Vancouver Island for analysis through their Sclerochronology (aging) Lab and Molecular Genetics Lab. From a single scale, scientists can determine the salmon species, age, and even its river of origin.

Results from 12 of the 15 samples are back and, unsurprisingly, Chinook salmon made up all but one sample (the outlier was a steelhead salmon caught by a Southern Resident killer whale known as J47). Most fish were between 3–5 years old and originated from rivers in southern Puget Sound, Vancouver Island, and mainland British Columbia. About one-third of the fish were hatchery-origin, while two-thirds were wild. Interestingly, one sample from a Northern Resident and one from a Southern Resident came from the same stock, suggesting partial winter overlap in prey use.

Alongside prey samples, we’ve also been collecting paired eDNA samples to test whether predation events can be detected without a physical sample. These are processed in-house at the Ocean Wise eDNA Lab and contribute to a growing dataset supporting eDNA as a minimally invasive research tool.

As we push further into the winter months of 2026, you’ll find us out there aboard our small research vessel Skana, bundled up and scanning for whales, and the scraps of meals they leave behind. The season started tough, but conditions have improved, and we’ve already secured our first Southern Resident prey sample of the year.

Fieldwork can be slow, wet, cold, and unpredictable. But when a single shimmering scale lands in the net, it makes it all worth it.