Lauren R. Stevens: In times of drought, consider the fish

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WILLIAMSTOWN — Parts of New England, including Massachusetts, have been in a moderate drought, according to the federal Drought Early Warning System. Some Berkshire communities are limiting non-essential water use. Weather forecasters anticipate that drought conditions will last through the summer, as the recent rains, though frequent, have mostly been scattered.

But consider the fish. Although the showers have relieved the situation temporarily, during most of June in county rivers not controlled by dams, the flows of water flirted with historic lows. Fish are stressed by low water in brooks and streams in several ways. Their variety of reactions reflects the variety of species.

In general, though, fish prefer to move up and down stream freely, for safety, for food, for spawning, to seek out more comfortable temperatures. As flows decrease, they may have to seek out deeper pools just too have sufficient water for swimming. That can place them at greater risk from predators, whether terrestrial like raccoons or avian like eagles. Or, for that matter, human fisherfolk. Furthermore, some species are adapted to living in riffles, not pools, and are therefore at a disadvantage.

Trout and other species need cold water. Air temperature, while it does not translate directly to water temperature, does influence it. Shallow water, moreover, especially when it isn't shaded, is likely to be warmer, as the sun reaches nearer the bottom. In warmer weather fish often have to retreat from main stem to tributaries, originating in these parts at higher elevations and therefore tending to be colder. The tributaries may not benefit the trout in other ways, such as providing food, however.

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When fish crowd together, whether in pools or tributaries, they can suffer from increased competition for food. Larger fish will eat smaller ones. And heated conditions can reduce bugs and other organisms fish feed on.

Fish take in oxygen from the water and release carbon dioxide, through their gills. They therefore thrive in oxygenated water, normally the result of the mixing that occurs as a stream tumbles over rocks or cascades. The froth is a combination of air and water. Low water holds less oxygen, because of reduced mixing.

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Berkshire rivers are likely to continue to flow, even in drought conditions. (Some rivers in the eastern part of the state may dry up.) Yet climate change is throwing traditional regimes of dry and wet out of balance, even here. For example, Berkshire used to rely on snowpack in the hills to prolong full river flows through the spring, but snowpack is diminishing. Both wet and dry conditions are becoming more extreme. Such changes have a significant effect on river ecology — and the health of the fish population.

Increasingly warm weather, as witnessed by lengthening Berkshire growing seasons, threatens our most charismatic fish population: the brown, the rainbow and, especially, the native brook trout. Droughts, whether moderate or extreme, are also related to a changing climate — yet another reason to believe trout days in southern New England might be numbered.

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The message is twofold. If the time comes when you are asked not to wash your car or water your lawn, consider that these inconveniences pale in comparison to the life-threatening situation the fish are in. People need to work together to avoid or at least mitigate the worst effects of a changing climate.

And, secondly, wise fishermen urge against adding to the stress on fish created by fishing in low-water conditions. Give the fish a break.

At least, that's how it looks from the White Oaks

Lauren R. Stevens is a writer and an environmentalist.


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