Anglers, Boaters Urged to Report Fish Kills This Summer


Massachusetts Fish & Wildlife is reminding boaters and fishermen to be alert for “fish kills” that may occur as lakes and ponds heat up. The state also points out that the vast majority of summer fish kills are natural events.

Natural fish kills are generally the result of low oxygen levels, fish diseases, or spawning stress. Depletion of dissolved oxygen is one of the most common causes of natural fish kills. Water holds less dissolved oxygen at higher temperatures; in shallow, weedy ponds oxygen can be especially low as plants consume oxygen at night. Spawning of fish such as sunfish, bluegill, and largemouth bass in late spring and early summer occurs in shallow waters along the shore. These densely crowded spawning areas can be the site of disease outbreaks, especially as water temperatures increase. The result is an unavoidable natural fish kill, usually consisting of only one or two species of fish.

To be sure there isn’t a pollution problem, report fish kills. When a fish kill report comes in, a MassWildlife fisheries biologist determines if the kill is a natural event or the result of pollution. In general, pollution impacts all kinds of aquatic life; therefore, the most important piece of evidence for the biologists is the number and variety of fish associated with the incident. When pollution is the suspected culprit, MassWildlife notifies the Department of Environmental Protection, which then conducts a formal investigation of the water and affected fish to determine the source of pollution.

To report a fish kill, contact the Environmental Police Radio Room at (800) 632-8075