The pH scale is a measure of the acid and base concentration of a solution. A pH of 7 is neutral; 0-7 is the acid range and 7-14 is the base or alkalinity range.

The presence of dissolved carbonates, bicarbonates, and hydroxides in water is associated with alkalinity. The presence of dissolved organic matter in water causes it to be more acidic in nature.

Fast growing fish are associated with alkaline waters; whereas slow growing fish are associated with acidic waters. Alkaline waters enhance the amount of aquatic foods


and weed beds. On the other hand, acidic waters curtail this production of aquatic foods and weed beds.

Acid rain can cause water to become too acidic for life, causing both fish and insect kills. A spring snowmelt can concentrate the acid in the bottom layer of the snowbank. When this last layer melts, high concentrations of acids are released into the watershed. This can be disastrous to aquatic life.

Local areas of a lake can vary in pH. Serious bass fishermen frequently measure the water’s pH to determine where bass may be concentrated.

In general, I avoid the acidic lakes and streams in favor of the alkaline ones. Perhaps this explains why so many Pacific Northwest waters are poor producers of non-anadromous fish. They are nearly barren of aquatic insect life. The abundant rainfall is so intense that these waters become soft and acidic, and the carbonates and alkaline elements have been depleted. The organic matter has concentrated in them. High desert waters favor alkalinity because less rainfall does not wash away the alkaline elements. Their weed bed growth and abundant insect life provide more ideal conditions for fast growing fish. I’m always amazed that a desert state like Nevada has such productive water while the rain forest of the Oregon Coast has an abundance of waters that are nearly void of residential fish. If it weren’t for anadromous fish, many coastal streams would not have fish.

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