Despite an elevation advantage that mitigates warm water in the summertime, trout streams in southwest Virginia, particularly during summers of little precipitation and high heat, can reach temperatures that stress trout. Across the state, water temperatures typically peak at the end of July and early August. So, if trout fishing during this period, it’s wise to understand the relationship between trout health and water temperature, and plan your fishing strategically.
As most anglers are aware, fish don’t have lungs for breathing atmospheric oxygen. Rather, they intake oxygen that is dissolved in the water through their gills. Specifically, gills feature countless filaments, each with thousands of small folds called lamellae. When water passes over a fish’s gills, dissolved oxygen passes through thin membranes in the lamellae, where it is incorporated into their blood stream.
For a fish to live, it must consume food and covert glucose into energy, a process known as metabolism, which requires oxygen in the bloodstream. The more energy a fish needs, the more dissolved oxygen it needs for the metabolic process. The warmer the water, the less dissolved oxygen it can hold.
Continue reading at dwr.virginia.gov.