Salmon Steward

salmon Steward magazine 5 Seals: Taking a Bite Out of Salmon Survival SALISH SEA BREAKTHROUGHS 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 commenced the effort in 2014, with a project that used a high-tech seal "beanie" to measure exactly how many juvenile salmon were being consumed; the project also included the collection of seal scats (a.k.a. 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 the total number of seals and how much each seal eats. "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," says Nelson. "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," Thomas explains. "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," he says. "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 in the Salish Sea Marine Survival Project will help fill in the blanks as to what precisely is compromising young fish in the Strait. "Another question that has come out of this," says Nelson, "is whether the abundance of hatchery fish in the Strait is signalling seals to feed on juvenile salmon rather than other species." Nelson would like to see future efforts launched in collaboration with hatcheries, varying the number and timing of fish released to see if it makes an impact on seal predation. u Seals lounge on log booms around Cowichan Bay on Vancouver Island. Above & Below: Ben Nelson on an expedition to collect seal scats.

• Cover