Barbs and Backlashes


Ah, spring is in the air . . . by whitetips
March 18, 2010, 9:24 am
Filed under: Fishing | Tags:

Can you smell it?  Spring is in the air.  Ah, the smell of decaying fish.

What?  Have I lost my mind?  Nope, well at least I do not think so, I am referring to the dead fish that are showing up in some waters as the ice thaws this spring.

Let me ramble on about winterkill for a little bit.  First of all, winter is hard on most living creatures, including fish.  It is not unusual to have some dead fish show up every spring as the ice thaws.  Some species of fish in Nebraska waters, gizzard shad would be a good example, are not tolerant of cold water and experience die-offs every winter.  So, if you see a bunch of dead fish and they happen to be gizzard shad, that does not mean anything–just a normal winter die-off of shad.  But if you see hundreds of dead fish as the ice thaws, a variety of species and sizes of dead fish, then there may have been a “winterkill”.

Let me explain what I mean by “winterkill”.  In some waters oxygen levels can decline underneath the ice to the point where fish cannot survive.  Some waters are more likely to experience winterkills and of course some winters will be worse than others.  Generally smaller, shallower bodies of water are more likely to experience a winterkill.  Deep waters will have more oxygen “stored” in the greater volume of water during the winter while shallower waters are more likely to have higher amounts of organic matter that can deplete oxygen levels.  Another factor in winterkill is the amount of sunlight that penetrates into the water.  During the winter, even under the ice, algae and aquatic vegetation can produce oxygen via photosynthesis, but a winter with a lot of snow on the ice reduces sunlight penetration.  Less sunlight due to prolonged periods of cloudy weather does not help either.  So, there are several factors that can influence winterkill and it can be difficult to predict whether winterkills will occur or not.  It is not unusual to see stressed or dying fish in waters that are experiencing low oxygen levels during the winter.  At times anglers may even see fish swim into their ice holes!  If one has a dissolved oxygen meter it is easy to document low oxygen levels, but usually we wait until ice-out and see what shows.

BC cartoon scanned from a recent edition of the Omaha World Herald.

If you are a pond owner, or you have a favorite private pond you like to fish, especially in eastern Nebraska, you may want to check it in the next week or two to see if there was a winterkill.  Again if you see just a few dead fish you probably have nothing to worry about; keep your eyes open for signs of live fish while you are looking.  If you see dead shad in a private pit or pond as the ice thaws, that does NOT mean you had a winterkill, shad die every winter (although I would tell you that if you have gizzard shad in a pit or pond you have other issues, another story for another time).  If you see hundreds of dead fish of a variety of sizes and species, well then your pond probably had a winterkill.  If you have a pond that occasionally has some sort of a fish kill, again that is a symptom of bigger problems (e.g. excessive siltation, too shallow).  But, I am afraid with the winter we had, especially in eastern Nebraska with an extended period of snow cover on top of the ice, there are going to be some waters with dead fish this spring, waters that usually would not have had any winterkill problems.  Sandpits are less likely to winterkill, but again if you have a sandpit or fish a private sandpit, it would be a good idea to check things out in the next week or two.

What can be done if you had a winterkill?  Obviously nothing can be done now.  On those ponds where you have had occasional fish kills there may be some major problems that need to be addressed by deepening or some other rehabilitation practice.  Aeration is an option for some waters, but I will tell you that aeration is not some “magic bullet”, sometimes it does not improve the situation as much as would be expected.  On a very small pond, clearing snow off of the ice can help, but with the winter we had this winter, that would not have been a practical solution on many waters.

Keep in mind that winterkills usually do not kill all fish.  Often there will be at least some fish survive.  Now that also can create other problems because species like black bullheads and common carp are more tolerant of low oxygen levels and may survive a winterkill that killed most of the other more desirable fish.  Probably the most important thing is to evaluate what survived and proceed from there.  If there were plenty of fish that survived, especially plenty of desirable game fish, then you may not need to do anything.  If most of the fish perished, then it is important to know if this was a rare occurrence due to the severity of this past winter or if it was due to a pond that needs major rehabilitation.  If additional fish kills are not likely, then re-stocking may be a valid management option.

If you need more information and perhaps some assistance, let me mention a couple of things.  First of all, if you own a pit or pond we have a Nebraska Pond Management book that you should have.  You can view that online or have a hard-copy sent to you, http://www.ngpc.state.ne.us/fishing/pdfs/pondmanagement.asp .  You can find additional information on our private waters program and possible management assistance here, http://www.ngpc.state.ne.us/fishing/guides/fishguide/FGprivate.asp .

Most of my comments have been related to private waters, but I am afraid we also are going to see some dead fish on public waters this spring.  In southeast Nebraska I already know of dead fish or suspected winterkills on several waters:  Carter Lake, Benson Park Lagoon, Louisville #1 and #3, possibly Memphis (I saw mostly dead shad there, will wait until more of the ice melts to see what else shows up), Killdeer, Cottontail, and even Jenny Newman.  Again before panic sets it, we will wait to see how bad some of those kills might have been; we might have to wait until we can see what survived.  We will keep folks posted as we know more.  I will also tell you I have looked at several waters in the past few days where I saw nary a dead fish.

Obviously not a dead fish, but a very healthy early spring bluegill!

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6 Comments so far
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Nooo!! Not Jenny Newman!!

Comment by fishinwithdad

That is exactly what I thought when I started walking around and found the dead fish there. Let’s wait and see what survived, hopefully it was not bad.

Daryl B.

Comment by whitetips

took a look at Jenny Newman, lots of bluegills on the shore… a few catfish and carp…no bass…but a pretty good bluegill die off…I would imagine some survived?

Comment by patrick

I spent a little bit of time there last week; did not see any live fish, but the water was still very cold. We will have to “wait and see”.

Daryl B.

Comment by whitetips

The sand hill lakes are so shallow any word on they faired this winter. Way too much snow this year

Comment by Bob

No problems on the sandhill lakes; I have not heard any reports of winterkills on those lakes. They did not have nearly the snow cover “out west” that we had in eastern Nebraska this winter. Another thing that helped is the water levels on most of the sandhill lakes were higher than they were a couple, three years ago. Many of the sandhill lakes have a few spring areas that help too.

Daryl B.

Comment by whitetips




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