Why is the River that Colour
Salmon in the Silt
As more glacial silt and volcanic dust wash into the Mamquam River, the water gets cloudier — and that makes life tougher for fish. Scientists measure this cloudiness using something called NTU (Nephelometric Turbidity Units). The higher the number, the murkier the water.
For reference:
Around 40 NTU, young salmon like coho start having trouble seeing food.
By 60 NTU, they may stop feeding and avoid certain parts of the river.
Some species, like sockeye and chinook, can still hunt in much cloudier water — up to 200 NTU — but even they get stressed from the extra hard work.
Turbid water can also smother eggs and cover up the gravel that salmon need to spawn. Chronic murk is not a simple condition to adapt to. As turbidity rises, protecting cool, clear patches of river is becoming more important than ever.
