Fish kills are not common in our area but certainly do occur given the right set of conditions.
Locally, late summer is a time one would most likely expect a fish kill. The fall of 2007 was a time of conditions favoring a fish kill, with quick changes in temperatures causing a pond turnover event.
While winter fish kills have been very rare in recent years, conditions are very favorable currently for a winter fish kill event.
During winter, oxygen produced from plants during photosynthesis is minimized. Plant material from summer continues to decompose and use oxygen. But thankfully, fish need less oxygen and are very immobile relative to other times of the year while typically during winter, oxygen levels in water are higher. The problem comes about when ponds freeze over, thus minimizing the oxygenation of water from the air and is further compounded when snow covers the pond. Snow cover blocks sunlight, thereby shutting down photosynthesis, which contributes oxygen to water.
The critical level is four parts per million of dissolved oxygen. In cold water, oxygen levels less than 2-3 parts per million for an extended time will begin killing fish.
During the recent week, some have inquired about what one can do to remedy the problem. It is not recommended that folks try to remove the snow on the pond, particularly with the depth of snow on the ice contributing significant weight.
Snow acts as insulation and may compromise the ice. In fact, just a week ago, individuals fell through the ice in Owen County, which was believed to be due to a spring that had compromised the ice in a particular area of the pond.
Larger and deeper ponds will result in the fish coming through this event most successfully.
Keeping summer plant growth minimized will also help for future reference. Furthermore, ponds with steep sides help minimize plant growth, which helps as well.
Drilling holes in the ice will not help. In years where there is a long period of ice with minimal snow cover, removing 25-50 percent of the snow cover from the pond surface will help. But again, it is not recommended that individuals try this at this time given the depth of the snow cover being too risky and major to move. Warm temperatures are predicted for this weekend and early next week. Hopefully, some ponds will see some ice melt so the fish have a break.
Ohio state publication A-8-01, entitled, "Winter and Summer Fish Kills in Ponds," is an excellent resource on this topic and is online.
You can contact the local Purdue Extension office by calling 829-5020 Ext. 14 in Owen County or 448-9041 in Clay County for more information or publication copies regarding this week's column topic or to RSVP for upcoming events. It is always best to call first to assure items are ready when you arrive and to RSVP for programs. While most publications are free, some do have a fee. All times listed are Eastern Time.
Feb. 14 -- Business Management for Horse Stables, Noblesville, 8:30 a.m.,
Feb. 16 -- Fruit Tree Growers Program (commercial), Martinsville, 9 a.m.,
Feb. 19 -- Clay SWCD Annual Meeting, 4-H Fairgrounds, 6:30 p.m.,
Feb. 26 -- PARP Program, Vigo County Fairgrounds, 8 a.m.
Feb. 27-28 -- Indiana Cattle and Forage Symposium, Indianapolis,
Feb. 28 -- Indiana Sheep Symposium, Noblesville,
March 10 -- Aquaculture Program, Spencer, 7 p.m.,
March 31 -- Fish Cage Construction Workshop, Spencer, 6 p.m.