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Seals: Taking a Bite out of Salmon Survival
Wednesday, 30 November 2016

When you donate to the Pacific Salmon Foundation today, your donation will be matched by donor Rudy North. And for every $100 donation, you will receive one entry to win one of two draw prizes: a rod, reel and tackle package donated by PEETZ Outdoors or a fridge stocked with PSF Lager!

Your donation will support salmon research and restoration efforts in the Strait of Georgia through the Salish Sea Marine Survival Project. Thanks to donors there are already some preliminary results rolling in including research on how much salmon those cute little seals are eating. 

There's been alot of fingerpointing at seals when it comes to salmon declines, but with little hard data to back it up. Thanks to research through the Salish Sea Marine Survival Project we can finally quantify how many juvenile salmon seals are actually consuming (spoiler alert - it's a lot!)

The Project

When seals became federally protected in 1970, their numbers increased exponentially around the Strait of Georgia from 5,000 in 1970 to 40,000 in 2008. These numbers coincided with a precipitous decline in Chinook and Coho salmon returns to the region, triggering research efforts through the Salish Sea Marine Survival Project to determine how many juvenile salmon seals are eating. Preliminary results have finally confirmed some long-held suspicions.

Lessons Learned

Dr. Austen Thomas started efforts with a project in 2014 using a high-tech seal 'beanie' that measured exactly how many juvenile salmon were being consumed, and included the collection of seal scats (poop) from sites around the Strait of Georgia. UBC doctoral student Ben Nelson, analyzed the scats for salmon DNA and plugged the results into a mathematical model that takes into account how much each seal eats and the total number of seals. "We discovered that from May to October, about 40 to 60 per cent of total juvenile Coho, and about 30 to 50 per cent of juvenile Chinook, could be lost to seal predation," said Nelson.

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"What's interesting about this is that there are significantly more Chum juveniles in the Strait, but the seals are targeting Chinook, Coho and Sockeye," said Thomas. "This is likely because they are larger than Chum when they enter the salt water, so it's more worthwhile for seals to target them."

According to Thomas, simply removing the seals won't necessarily solve the problem. "The key question is why seals are now targeting these juvenile salmon?" said Thomas. "We suspect that juveniles in the Strait could be compromised due to pathogens, poor food supply, or a lack of refuge habitat, which in turn makes them more vulnerable to predation. So if you remove the seals, another predator may simply move in to fill that void." Other initiatives through the Salish Sea Marine Survival Project will help fill in the blanks as to what is compromising young fish in the Strait

Ben Nelson at Cowichan Bay Seal haul out sites

"Another question that has come out of this," said Nelson "Is whether the abundance of hatchery fish in the Strait is signaling seals to feed on juvenile salmon rather than other species." Nelson would like to see future collaborations with hatcheries to vary number of fish released and timing to see if it makes an impact on seal predation.

Donate today to support more projects like this and help bring our fishery back!