Pacific Salmon have a unique lifecycle, spending parts of their lives in freshwater and saltwater. This opens them up to a broader scope of impacts not limited to one specific area. Understanding Pacific Salmon Lifecycles is fundamental in addressing the challenges that face them. Let's look at some of the key issues.
Although average temperature and rainfall amounts hasn't fluctuated a noticeable amount over time in our area, the frequency and severity of extreme weather events has increased from climate change. We are more frequently seeing periods of heavy rains (atmospheric rivers) and extended droughts. Heavy rains increase the risk of washing out or silting in salmon redds and can lead to decreased survival for both adult and juvenile salmon in river depending on the time of year. Coho, sockeye, and specific populations of chinook are more susceptible to increased droughts as they spend a longer amount of time in freshwater.
Plastic Pollution is another issues affecting marine life, including Pacific Salmon. Upon consumption, marine plastics can physically and chemically affect zooplankton and fish. Physical effects from eating it can obstruct their mouths and throats, block their digestive track, artificially fill their stomachs, and be absorbed into other parts of their body (Cedervall et al. 2012; Cole et al. 2013; Rochman et al. 2013; Desforges et al. 2014, 2015)
Rivers and streams are at risk of major negative impacts when riparian zones are altered. This can happen through various means, but industry such as private land logging, agriculture and urban development can impede too close to watersheds. Clearing of trees, bushes, and grasses can destabilize river banks leading to increased runoff and channelization of watersheds.
Salmon face many predators at all life stages, and humans are one of the most impactful. Commercial and recreational fisheries all put a strain on salmon populations, and can impact non target species (bycatch) such as steelhead and trout. Commercial fishing of smaller baitfish such as herring and eulachon also negatively affect salmon by straining the food web that salmon rely upon.
Dams, weirs, and improper culvert placement have been known to greatly reduce the amount of viable spawning grounds salmon have access to.
Salmon face an ever growing population of predators. Seal and Sea lion populations on North Americas West Coast have been growing steadily since 1970, with nearly 105,000 harbour seals in BC alone. Resident Orcas also eat a large number of salmon.