Winter fish kills can be expected

January 14, 2009 by admin.

Here is an ‘official’ response to recent reports of fish kills in Grand Lake:

“Gizzard shad mortality during late fall and winter is a common observation at Grand Lake St. Marys and other Ohio water areas.  Based on my observations in southwest Ohio since 1979, many of these shad die offs occur either during periods of rapid water temperature decline in late fall, or during periods of extreme cold and ice cover.

Grand Lake St. Marys has a long history of shad winterkills.  The following is taken from the publication titled “Lake St. Marys and Its Management” by Clarence Clark (ODNR 1960): “Winter kills of gizzard shad are almost an annual occurrence.  The largest kill, in recent years, took place during the winter of 1947-1948… Windrows of shad were piled on the beaches and were hauled away by the dump truck load.”

Other references to winter mortality of gizzard shad include:
“It [gizzard shad] winter-killed readily, especially the young.”  “Large autumnal killings of the young of the year still occur in parts of Lake Erie and in some impoundments…” (Trautman, M.B.  1981.  The fishes of Ohio with illustrated keys, revised edition. Ohio State University Press. P. 203).

Cold water temperatures are related to large winterkills of gizzard shad in Lake Erie, Black Hawk Lake in Iowa, and several reservoirs in New Mexico.  Although small young-of-year shad were the most common winterkill victims, older shad were killed when the kill was prolonged or the water temperature was below 36 ° F. (Jester, D.B. 1979.  Biology, trophic status, and ecology of the gizzard shad.  Unpublished manuscript.)

Granted, fish mortality at this time of year could be related to a runoff-related pollution event, or perhaps an oxygen depletion under heavy snow-covered ice.  However, given the long history of shad winterkills at Grand Lake St. Marys, I’m more inclined to believe that the recent observation of dead shad is related to something as mundane as water temperature.

Doug Maloney
Fish Management Supervisor
ODNR, Division of Wildlife
1076 Old Springfield Pike
Xenia, Ohio 45385
phone 937.372.9261
FAX 937.376.3011
doug.maloney(at)dnr.state.oh.us “

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