Salmon Steward

8 2019 psf.ca F orage fish form a bedrock of the ecosystem, feeding most predatory marine creatures that outsize them – including salmon. But while there are studies on commercially fished species like herring, there is a giant gap in our understanding of other forage fish species that are just as important. The Adult Salmon Diet Study, funded by PSF via the Salish Sea Marine Survival Project (SSMSP), is using salmon stomachs and volunteers to fill that gap. According to Jennifer Boldt, DFO research scientist: "Forage fish are generally di…cult to assess because their numbers vary highly depending on location and time of year. Examples of forage fish species in the Strait of Georgia include Pacific herring, Northern anchovy, eulachon and Pacific sandlance. Forage fish abundance can be aŠected by environmental conditions, the timing, availability and quality of food, predators, and competitors." "We are using salmon to understand their own ecosystems," says study lead Will Duguid, a PhD student at the University of Victoria. "Rather than going out and sampling the ecosystem ourselves, we're trying to sample it from the salmon's perspective." This fisheye view of the state of the Salish Sea food web was inspired by anecdotal reports from anglers who noticed the stomach contents of salmon they caught varied widely at diŠerent times of the year and diŠerent locations. Though interesting to researchers, these reports didn't stand SALMON TELL THEIR OWN STORY The Adult Salmon Diet Study uses salmon stomachs (and the volunteers who collect them) to fill key data gaps up as usable scientific data – they did, however, highlight the need for more fulsome monitoring methods. Cumulative findings from the SSMSP highlight the necessity to understand what salmon are eating and what is aŠecting them during winter – a key reason PSF funded the expedition to the Gulf of Alaska this winter (read more on p. 23). But traditional sampling doesn't cover this critical period. "Traditional sampling involves going out on a large vessel and trawling with a net," Duguid explains. "The area covered is necessarily large and, because it's a really costly process, the number of times you collect samples in a given year is limited and only produces snapshots of the situation. While it is a very useful tool, we needed a complementary program that was aŠordable to help fill those data gaps." Adds Isobel Pearsall, PSF coordinator for the SSMSP: "The nets used in traditional sampling do not retain species such as sandlance very well, so we have very little information on long-term changes in their abundance."šš šSo, a pilot study was launched in 2017 with the help of volunteer citizen science group the Avid Anglers. Anglers were asked to save and freeze the stomachs of salmon they caught, fill out a data card for each fish, and drop stomach contents oŠ at designated tackle shops. By engaging multiple volunteers with small vessels, the team was able to collect data from all over the Strait throughout the year. "We've analyzed more than 1,000 fish over a couple of years and it's giving really interesting year-round data," Pearsall explains. Results so far indicate that Pacific herring are by far the most important prey for both Chinook and Coho, providing a food source all year long. In June, small, recently hatched herring feed juvenile Study lab manager Jessica Qualley and lead technician Katie Innes clean salmon before removing their stomachs. BY FIONA MORROW

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