McClory: Fish kills may not be as worrisome as they seem

With warm weather heating up lakes and ponds, the Division of Fisheries and Wildlife (MassWildlife) has already fielded nearly two dozen reports about fish kills discovered in some bodies of water. Half of these calls have been since the beginning of June. The sight of dead and dying fish along the shores of a favorite lake or pond can be distressing and trigger concerns about pollution. Fish do act as the “canary in the coal mine,” so it’s natural to think a fish kill is an indicator of a problem with human-caused pollution. However, the vast majority of fish kills reported 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. As pond temperature increases, water holds less oxygen. During hot summer weather, oxygen levels in shallow, weedy ponds can further decline as plants consume oxygen at night. This results in low early morning oxygen levels that can become critical if levels fall below the requirement of fish survival. In addition to reduced oxygen levels, late spring and early summer is when most warm water fish species, such as sunfish (bluegill, pumpkinseed, largemouth bass) begin to spawn. At this time, large numbers of these species crowd into the shallow waters along the shore vying for the best spawning sites. These densely crowded areas become susceptible to disease outbreaks, especially as water temperatures increase. The result is an unavoidable natural fish kill, usually consisting of one or two species of fish. When a caller reports a fish kill, a MassWildlife fisheries biologist determines if the kill is due to pollution or is a natural event. Generally, pollution impacts all kinds of aquatic life; therefore, the most important piece of evidence for the biologists is knowing the number of fish species associated with the fish kill. Fish kills in which only one or two species are involved are almost always a natural event. To report a fish kill Mondays through Fridays between 8 a.m. and 4:30 p.m., contact Richard Hartley at (508) 389-6330. After normal business hours or on holidays and weekends, call the Fish Kill Pager at (508) 722-9811 or contact the Environmental Police Radio Room at 1-800-632-8075.New hunters of all ages are reminded that it is never too early to sign up for a Basic Hunter Education Course. First-time license buyers in Massachusetts are required to show proof that they have taken a basic hunter education course in order to purchase a hunting or sporting license. Basic courses are available across the state and many begin in August and September. Course schedules are posted online at www.mass.gov/dfwele/dfw/education/hed/hed_basic_listing.htm, or by contacting the office directly at (978) 632-7648.From the Kittery Report, togue (lake trout) fishing at Sebago Lake is still phenomenal. The fish are still scattered in several depths and not all on bottom as is usual for this time of year. Sewed-on shiners, both fresh and pickled, are working best for the togue. Salmon fishing at Winnipesaukee is starting to pick up again now that a thermocline has begun to set up at around 30 feet. Most of the action on salmon and trout has been on lures with orange or any combination of colors with orange being the hot color.As a last-minute reminder, all bow, shotgun and muzzleloader deer hunters are reminded they must possess an antlerless deer permit in order to take any antlerless deer during any deer hunting seasons. The July 16 application deadline is fast approaching.All for now.