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Fraser salmon face many challenges in their life cycle
Once again sockeye salmon are heading through the Strait of Georgia and into the Fraser, as they make their way to spawning grounds in the upper reaches of the river.
They come in waves by cohort: Early summer, summer, and late run. More than 200,000 early Stuart salmon passed the observation station at Mission and are already on their spawning grounds in the northernmost part of the Fraser basin.
The famous Adams River salmon are part of the Shuswap Late Run and spawn in the fall.
This is a dominant year of the cycle and fisheries scientists have issued a pre-season run forecast of 22.9 million sockeye.
The fish heading upstream today grew from spawn following the 2010 run, the largest since 1913, with more than 30 million fish.
That exceptional run took everyone by surprise. The year before had seen the great salmon crash when after years of decline only 1.6 million returned. The demise of the sockeye led to the 18-month-long Cohen Inquiry.
The resulting three volume report made many recommendations but concluded there was no single cause for failing salmon populations.
The environment is intensely complex and the combination of effects from habitat loss, disease, fish farms, climate change, and overfishing was too difficult to disentangle.
The 2010 lineage seems to be a stronger bunch, as they have generally done better than other classes.
This year’s returning salmon face huge challenges as they head upstream.
The river water is 0.7 degrees C warmer than average for this time of year, and flow is 11 per cent lower at Hope.
These differences may appear small, but salmon are very sensitive. Sockeye need an ambient temperature between 12 and 15 degrees C to survive.
They need clear, running water in shaded streams lined with gravel in which to spawn and deposit their eggs.
The tailings dam breach at Mount Polley mine, northeast of Williams Lake, washed millions of cubic metres of turbid water and sediment into tributaries of the upper Fraser, which could potentially smother sensitive gravel beds downstream in the renowned Horsefly region.
While the water has so far tested safe by drinking water standards, it will need to be tested for traces of copper and other minerals that are safe for humans but not for fish.
The salmon heading through the Fraser estuary have huge challenges to face to successfully complete their life cycle.
Let’s hope they make it safely.
Anne Murray is a local naturalist and writer and blogs at www.natureguidesbc.wordpress.com. Her books on Delta’s natural and ecological history, A Nature Guide to Boundary Bay and Tracing Our Past, a Heritage Guide to Boundary Bay, are available in local stores or from www.natureguidesbc.com