River levels in southern B.C. are low, and their temperatures are warmer than normal. Fish are seeking shelter in deeper, larger, cooler pools wherever they can. With fish pooled in creeks and rivers, disease spreads more readily, and predators have an easier time making their catches of the day.
Returning salmon, of course, can’t choose to spend their final months hiding out in cool pools. Their biology drives them to reach their gravel beds of origin in time to spawn. While they may rest in deeper pools en route, the imperative sends them away from shelter into whatever channels contain enough water to allow them to fight their way upstream, no matter the water’s temperature.
Warm water causes fish to use more energy and tire faster. Warm temperatures can change freshwater chemistry, affecting the amount of oxygen dissolved in the water and available to fish and other critters. More »
