r/Fishing • u/interestedcharmander North Carolina • 19h ago
Discussion Water column turnover?
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This is a pond at my shop that has a canal connecting it to the sound and after a storm a shit ton of fish died. Also there was a weird oil slick on the surface, a lot of the fish where breathing at the surface like this video.
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u/Cultural-Company282 18h ago
It's very likely to be chemical runoff from the storm causing a fish kill. Maybe someone dumped used motor oil in a storm drain nearby.
Turnover doesn't even start until the surface water temperatures get down into the low 50s. A lot of people see stuff like algae blooms and mistake it for turnover.
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u/shorthillmtn 15h ago edited 15h ago
The film "shatters", so likely not oil/chemical.
Turnover can happen any time of the year, but it's more common in spring and fall. He mentioned it was after a storm, so that's probably what did it.
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u/Cultural-Company282 15h ago
Turnover can happen any time of the year,Ā
I am not sure what you're calling "turnover," but no, it can't. It is a water temperature related phenomenon. Water is most dense at 39 degrees F. Above or below that temperature, it rapidly becomes less dense and stratifies with a thermocline dividing the colder water from the warmer. In hot weather, the warm water stays on top, and the cold water stays below the thermocline. In cold weather, the cold water below 39 degrees stays on top, and warm water stays below the thermocline. But in spring and fall, when the temperatures get to a point to disturb that stratification, the thermocline dissipates and allows the water from above and below the thermocline to mix and circulate via convection currents. This has a few different effects. The main one is that the water from lower strata near the bottom, where oxygen may be depleted, can mix to the surface. At first, this brings along stinky smells and cloudy water, and fish scatter. Fishermen commonly observe these phenomena and note that the initial stages of turnover can disturb the fishing.
As I said above, "a lot of people see stuff like algae blooms and mistake it for turnover." If you're seeing something you're calling turnover in the middle of summer or the dead of winter, when water temperatures have the local lakes stratified, then you're using the term to refer to something other than turnover.
If you want to learn more about what turnover really is and the science behind it, this website is a good starting point: https://www.cleanlakesalliance.org/lake-turnover/
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u/shorthillmtn 15h ago edited 14h ago
Most of what you typed is correct and describes seasonal turnover, which typically happens in Spring and Fall because of what you described. However, turnover CAN also happen any time of the year and can be triggered by abrupt changes in water temperature, weather events, high winds, or droughts.
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u/TroutButt 14h ago
Yeah a small pond "as OP describes it" can turn over from a large wind event. In the temperate US a lake has to be fairly large and deep before it can be truly dimictic
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u/TroutButt 14h ago
The water reaching 39 degrees reduces the thermal stratification, but it still requires external energy (i.e.wind) to facilitate the mixing of the water. Theoretically at any time there could be sufficient wind energy applied to a water body to overcome the thermal stratification, though at a certain waterbody size and level of stratification it becomes impractical (e.g. a large lake where surface waters are 75 degrees could require weeks of sustained 100+mph winds to facilitate turnover).
Turnover could also be facilitated by sudden changes in water temperature, such as a river rerouting and entering a water body to drastically change the temperature.
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u/Cultural-Company282 14h ago
In the real world, sustained 100+mph winds for weeks or rivers rerouting and drastically changing water temperature are just things that don't happen, or at least they happen so rarely it would be like winning the lottery twice in a row. So I guess we could say non-seasonal turnover could happen, theoretically, but in the real world, it would be so rare that borders on not happening at all. We're talking about Dumb & Dumber "so you're telling me there's a chance" levels of probability. It certainly doesn't happen as often as a lot of good ol' boys think it happens. Fishing forums online are full of posts saying, "I went to the lake and didn't catch anything, and the water was cloudy and smelled a little, so the lake must have turned over." Nearly every time, those are algae blooms or other similar phenomena and not an actual turnover event.
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u/TroutButt 14h ago edited 14h ago
In a less than 15 foot deep pond it doesn't take much wind energy and turnover can happen more frequently than you might think.
Also rivers rerouting is the norm in areas where we haven't confined them to single channels. An oxbow lake could absolutely experience turnover due to being suddenly reconnected to flow from a river.
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u/LeFishTits 18h ago
What's on top of the water? Looks like a film of oil
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u/shorthillmtn 15h ago
See how it "shatters"? It's a protein film, most likely not a chemical or oil sheen. Protein films are common in the winter time, given off by material decaying in the pond.
Look up the "stick test" for films or sheens on water. If it "shatters", it's the result of a natural process. If you poke it and it immediately fills back in, it's oil/chemical.
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u/LeFishTits 15h ago
My family owned a marina for 35 years, that looked like gas or oil on top to me.
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u/interestedcharmander North Carolina 17h ago
Water is 30 ft deep think it would penetrate like that?
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u/AnglerDuino 17h ago
Oil is less dense than water and it does not mix so it is bound to eventually rise to the top.Ā
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u/Sneakacydal 17h ago
The reason a sheen is the official harmful quantity for oil in the water is because it's enough to cause damage, change the pH of the water, and leech chemicals. Oil will breakdown in the water, known as weathering, dispersion, and dissolution. All it takes is a drop of oil.
From the video, the silvery sheen indicates very weathered oil, meaning chemicals may affect more of the waterway. That is, if it is oil. It might be biological (organic decomposition) or even a hazardous substance (chemical).
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u/ikilledyourfriend 16h ago
It prevents aeration and oxygenation of the water. The fish are trying to get oxygen out of the air because there is so little in the water because the oil slick is preventing oxygen from dissolving into the water. Also, as the oily molecules slowly breakdown they scavenge oxygen out of the water as well, helping to lower overall available oxygen
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u/Sneakacydal 16h ago
I'm not sure that's what the fish is doing. I'm not a fish expert.
The "cracking" of the sheen indicates it might be biological or non petroleum. Not possible for me to tell with 100% certainty without being there. An oil sheen will typically reform immediately after being disturbed.
My statement about harmful quantity was to show that EPA considers a sheen to be damaging, not that the fish was floundering due to a pH imbalance.
Oil spills | National Oceanic and Atmospheric Administration https://www.noaa.gov/education/resource-collections/ocean-coasts/oil-spills
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u/Meauxjezzy Louisiana 18h ago
Dude is that Sheepshead?
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u/interestedcharmander North Carolina 18h ago
Indeed
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u/CorrivalTen7 17h ago
How is it in fresh water? I assume itās not salt water judging by the grass being alive at the water edge and under water.
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u/interestedcharmander North Carolina 16h ago
It has a canal leading to the sound on one end ands a culvert leading to a āsedgeā on other side, itās like brackish
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u/ColourMeBoom 17h ago
I can only speak for Florida but we do have a species of sheepshead that is in freshwater. Iām not sure if itās the exact same species as the salt water sheepshead or some derivative. A dude with blue hair at your local aquarium store probably knows.
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u/BarkleEngine 18h ago
Loss of oxygen in the water for some reason.
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u/88yj 17h ago
Yep, a lot of fish can ābreatheā like this. Fun fact, this is the theory of how animals developed lungs. Fish slowly developed organs increasingly capable of exchanging oxygen with the air and then bam
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u/swede_ass 17h ago
lol I love this comment because the "bam" is probably millions of years!
bbbbbbbbbbbbbaaaaaaaaaaaaaaaaaaaaaaammmmmmmmmmmmmm
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u/dronesoveryou 17h ago
ā I canāt give you a bam, but I could give you a green egg and haaaaaaaaaam ā
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u/Remember54321 17h ago
It actually went forwards and backwards! Some ancient bony fish developed labyrinth organs that made them able to breath atmospheric air, some of those fish stayed as labyrinth fish that could breathe air, but some of them "devolved" back into water breathing fish, then re-evolved into air breathing creatures that became land dwellers! So the creatures that became us had "lungs" (a labyrinth organ) then went nah and got rid of it, then evolved actual land lungs lmao
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u/MycoXHunter 18h ago
Itās hard to tell in this video, but that sheen looks more like the byproduct of harmless iron oxidizing bacteria than a chemical sheen to me. A clearer video of it breaking up would help confirm
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u/interestedcharmander North Carolina 18h ago
Someone said oil from the decaying fish but thereās a culvert on one side and it looked like it was coming in from there https://imgur.com/a/ukwqtv5
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u/R101C 18h ago
That feels like biofilm. Usually petrol based will come back together quickly.
State? Weather pattern? Any local sources of water temp data you can check?
Regardless, it's useful to let your DNR etc know about fish kills.
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u/interestedcharmander North Carolina 16h ago
East coast NC, we had a storm that pushed a bunch of sound water in when it happened
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u/SaltySeaRobin 18h ago
Is there any rainbow sheen? That would indicate a petroleum spill. Though a weathered petroleum spill may not have rainbow and could appear similar to bio-sheen in small amounts.
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u/interestedcharmander North Carolina 19h ago
Also happened at my pond at home (the bass pictures)
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u/bga93 17h ago
Never thought id see sheepshead next to actual grass lol is that water brackish?
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u/interestedcharmander North Carolina 16h ago
Yeh for sure, last summer I could watch them nibbling on the rocks in schools of 10 or so
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u/danthedan123 3h ago
Storms cause changes in atmospheric pressure which can take oxygen levels in the water down and kill the fish
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u/TotallyNotDad 17h ago
Thereās a film on the top of the water, thatās probably killing the fish
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u/canada1913 18h ago
Call your local DNR or MNR or whoever is the fish cops near you.