Which Salmon are you?
The five species of Pacific salmon that swim through waters off the BC coast differ somewhat in appearance, but their habits and preferences also set them apart from each other.
Orca whales, sea lions, and seals all rely on salmon as a food source in the ocean. Commercial, sport and First Nations fisheries depend on salmon too.
When the number of salmon decreases, it affects all of the other species that depend on them, so an oversupply of one kind of predator – human or natural – can have an enormous impact.
High-tech Beanie Reveals Seal Strategy
Harbour seals came under federal protection in 1970. After decades of over-zealous hunts, fewer than 5000 seals remained around the Strait of Georgia. By 2008 seal numbers had rebounded - skyrocketing to about 40,000 or an eight-fold increase. Chinook and Coho salmon, on the other hand, declined sharply in the same waters in the same four decades despite enhancement programs aimed at increasing salmon stocks.
Read MoreThe relationship between the two is now the subject of investigation. In one study, radio frequency ID “beanies” were glued to the heads of twenty seals, and 40,000 juvenile coho salmon were tagged before they were released from the Big Qualicum Hatchery on Vancouver Island. Every time a seal with a beanie ate a tagged salmon, it was recorded.
Dr. Austen Thomas of the UBC Institute for Oceans led the study. In related research over the same period, UBC doctoral student Ben Nelson analyzed seal scats for evidence of salmon DNA.
Early findings after mathematical modeling of the data revealed a specific pattern – the seals are not going after just any salmon. They are targeting juvenile Coho and Chinook that are heading from freshwater out to the Salish Sea.
The research suggests as many as 40 to 60 per cent of all juvenile Coho and 30 to 50 per cent of juvenile Chinook in the months from May to October could be lost to the expanded harbour seal population.
Now the researchers are turning their heads to the question of why these juvenile salmon are such choice targets. Are they already compromised in some way due to lack of refuge habitat, or weakened by pathogens? Removing the seals would not necessarily solve the problem – the researchers point out another predator could just move in to fill the void.
These studies by Thomas and Nelson are part of a much larger joint Canada-US research project focussed on finding out more about the ocean life of salmon.
Pacific salmon that make their way to the ocean from BC’s lower mainland and Vancouver Island head into the body of water now known as the Salish Sea. It encompasses Puget Sound, the Strait of Georgia and the Strait of Juan de Fuca and it is currently the site one of the largest scientific salmon sleuthing expeditions ever. What’s their quest? To find out why salmon are dying in the Salish Sea.
Salish Sea Survival Project Sampler
The goal of the Salish Sea Marine Survival Project is to better understand the life of salmon in the ocean – and critically – why the fatality rates are now so high for some salmon species during their time in the marine environment.
The research is both bottom-up and top-down. Bottom up investigation is about factors such as plankton, weather and water that affect the salmon’s ability to eat.
Canadian projects include the impact of diminished shoreline vegetation and food webs as well as large scale oceanographic data capture by the owner-operators of small boats who have volunteered as citizen scientists.
Top down research focuses on the limits to salmon survival imposed by their predators, competitors – and any other elements that weaken juvenile salmon.
Canadian studies in this area includes genome research into pathogens and other stressors for young salmon, as well as individual investigations into a number of different types of predators.
Sixty organizations including universities, the public and private sector and First Nations in Canada and the U.S. are working together under the coordination of the Pacific Salmon Foundation and Long Live the Kings.
The odds are stacked against salmon at every stage of their lives. Select from the tiles below to see some of the hazards they face, and how many salmon will make it through to the next stage in their journey.
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No one knows for sure how the salmon find their way back to the exact stream where they were born. Research points to a form of internal compass - or a sophisticated sense of smell that can detect differences in river water to guide them all they way to their home stream.
Certainly, the instinct that drives wild salmon to venture afar and then turn for home is relentless. And their timing is impeccable.
