Why'd the Fish Die? Scenario I

[Chad]

Why'd the Fish Die? is a forum series designed to identify the causes of various fish kills. Each scenario will tell a story of a fish kill and then ask three critical questions:

1) Why did the fish die?
2) What could have been done to prevent it?
3) What should be done now that it has happened?

Everyone is welcome to throw in their .02. Answer all three questions or just one - no rules. Heck, derail the thread and talk about how the wipers ate all your crappie, if you want to.

Smarter anglers make better anglers... usually ,
- Chad

******************************
It’s late August and you decide to get up early and enjoy the dawn while fishing at a private pond nearby. As you leave the house in the pre-dawn hours, you hear the crickets, feel the heat and humidity, and can see easily with the clouds – a constant for the past few days - reflecting light. You’re happy for the continued still conditions and decide to grab the fly rod and hip waders to search for a lunker LBM along the pond's extensive shallow weed growth.

The sun is just creeping over the horizon as you pull on waders and string up the fly rod, but a beautiful morning turns heartbreaking quickly as you approach the pond. Despite a chorus of bullfrogs and “healthy” sounds coming from the pond, you discover a fish kill has taken place. Even more concerning, it seems that some of the largest specimens have suffered the most. You bend down to examine the lunker you might have caught that morning lying dead on the bank - she's 5lbs if she's an ounce. As you look up, you see other large fish dead along the shore and can hear and see other fish gasping for air at the surface. Perplexed and disappointed, you sit down to figure it all out.

1) Why did the fish die?

2) What could have been done to prevent it?

3) What should be done now that it has happened?

[Alex T.]

Chad,
Are you obsessed with this farm pond thing or just tired of winter??

Alex

[AnglerX]

Is the water clarity good? Is there a farmland in the watershed? Is the weeds still green? Did it rain alot in the days before?

[burrodebo]

Originally Posted by Alex T.

Chad,
Are you obsessed with this farm pond thing or just tired of winter??

Alex

Alex,

You are hardly the one that should be talking about being obsessed.

[Chad]

Originally Posted by Alex T.

Chad,
Are you obsessed with this farm pond thing or just tired of winter??

Alex

Obsessed.

[Alex T.]

Bo,
It's personal with snow geese not an obsession.

Alex

[AnglerX]

You guys going to talk duck? Or is Chad going to answer my questions?

Originally Posted by AnglerX

Is the water clarity good? Is there a farmland in the watershed? Is the weeds still green? Did it rain alot in the days before?

[Chad]

Sorry, Andrew... I had to get a workout in over the lunch hour...

To answer your questions:

Is the water clarity good? It was before this morning. Now, you're not really sure... still to dark to tell from shore. Venture out there and stick your hand under the surface and let us know.

Is there a farmland in the watershed? Yes.

Are the weeds still green? Some appear to be browning.

Did it rain alot in the days before? No, just been real cloudy.

[AnglerX]

Well I'm at loss. It didn't rain and it's cloudy and the weeds are browning. I would say the fish are suffering from depression and beaching themselves.

[wneb.fisher]

Sounds like there could be a deficit of the oxygen content in the water. If there is a farm on the water shed there is also the possibility of chemicals in the runoff from irrigated crops. This may explain the browning of the weeds.

[vrentropy]

Originally Posted by Chad

1) Why did the fish die?

2) What could have been done to prevent it?

3) What should be done now that it has happened?

1) -- The fish saw the flyrod and laughed themselves to death.

2) -- Not waving around the Fairy Wand.

3) -- Put that silly lookin stick away and get a real man's rod!






Or:

1) -- Lack of Oxygen. This most likely due to the cloud cover of a few days, the lack of wind and the heat, all which would reduce the waters ability to contain dissolved O2.

2) -- Making sure that the drainage area did not have the chemicals that caused what may currently be a dying algae bloom.

3) -- Buy that paddle boat in the for sale forum and paddle that sucker around to get some oxygen splashed into the water! -- Or add an aerator or water sprayer to help to get some O2 dissolved into the pond.

How'd I do?

[Shorty]

The fish died from a Dissolved Oxygen (DO) sag caused by the dying vegetation and or a wanning summer algae bloom. A strong cold front followed by several days of cloud cover was the likely culprit. A herbicide application that washed into the pond from surrounding farm fields could also be another possible cause.

An good aeration system could have prevented this in a small pond.

A damage assessment should be done now that the fish have died to see if this was a total fish kill or if the fish kill affected one species more than another, if there are survivors this could put the pond out of balance.

[houghty26]

In August somebody used a fungicide that is deadly for fish on their corn crop and you had a late night rain right after applied at 7 pm (b/c they are very rainfast). Ground doesn't have to be irrigated for runoff. Or if it was spring and farmers didn't use a buffer strip or grass waterways and you had a major rain after fertilization large amounts of phosphorus or nitrogen (depending on how it is applied) running off into the water could cause an algal bloom down the road. I work in ag so I know that it is a balance of both worlds, if it wasn't for farmer's you wouldn't have "farm ponds." Those are some potential causes, there is a lot farmer's are doing with buffer strips, applying certain chemicals a specified distance from water sources, etc. all on the govm't label. Just playing Chad's game. If I had a "dream" pond it would be stocked with unicorns

[Chad]

Some good insights here. From reading the responses, three main possibilities were advanced.

1. Depression, Resulting in Suicide
2. A Toxic Substance
3. A DO Sag

#1 may be right on (there's no way to prove otherwise )


#2 is possible, but wasn't what I had in mind. The fact that frogs and other aquatic organisms are doing fine would be evidence against this since a toxic substance would affect frogs, insects and fish.

"Despite a chorus of bullfrogs and “healthy” sounds coming from the pond..."

This theory may also be less likely given the absence of recent rain.

Did it rain alot in the days before? No, just been real cloudy.

The final clue was the fact that larger fish suffered the most.

Even more concerning, it seems that some of the largest specimens have suffered the most. You bend down to examine the lunker you might have caught that morning lying dead on the bank - she's 5lbs if she's an ounce.

#3 is exactly what I had in mind... Consecutive days and nights of cloudy, hot, still conditions with high water temps prevented plants from producing oxygen. The lack of wind prevented mixing of oxygen into surface water. Aquatic organisms’ respiration and plant decomposition depleted available oxygen. As mentioned, this was a pond with "extensive shallow weed growth," making it more vulnerable to this kind of summer kill.

Shorty and Entropy had some great suggestions aimed at adding DO to the pond.

Buy that paddle boat in the for sale forum and paddle that sucker around to get some oxygen splashed into the water! -- Or add an aerator or water sprayer to help to get some O2 dissolved into the pond.

A good aeration system could have prevented this in a small pond.

Ultimately, an aeration system may be the most feasible route, but a "natural" solution may produce an ultimate fix, if feasible. Drain the pond and regrade. Folks smarter than me recommend that the slope from the shore to 4 or 5 feet of depth should be roughly 1 foot vertical drop for every 3 horizontal feet. Additionally, there shouldn't be more than 20% of the pond that contains water with a depth less than 2 feet, with 35% (or thereabouts) of the pond at least 10 feet deep.

If the pond isn't going to be drained and regraded, shorty's suggestion to conduct, "A damage assessment should be done now that the fish have died to see if this was a total fish kill or if the fish kill affected one species more than another, if there are survivors this could put the pond out of balance."

Thanks for playing everyone!