Hi,
I'm new to this forum and I joined based on advice from a local lake management company owner. He said that if I needed information on anything and everything ponds, this would be the place to go.
My BSAA(biological science with applications in agriculture) teacher gave us a project that requires me to analyze a problem in a pond. The pond's situation is this:
Landowner found fish gulping at surface one evening and returned the next day to find fish of all kinds and sizes floating dead.
Pond Info: 6 acre S.A., drains 500 acres of farm land, used for cattle watering, fed by intermittent stream, pH of 4.7, avg. depth- 4 ft., contains bass, bluegill, channel cat, green sunfish, white crappie, grass carp, pumpkinseed
Based on this information, I need to come up with a reason for the fish kill and a solution to the problem. Just wondering if anyone could point me in the right direction.
Thanks, student96

Welcome to the forum!

First question: Hopefully you're a better student than I was, and this is not due tomorrow. When's your deadline? You'll get lots of help and interest here, and hopefully learn a thing or two...

Second: What do you think happened to the fish? Hypothesize a bit, give your reasoning, we'll help.

Are you needing possible causes, or definitive?

The project is due Friday morning so I have a little bit of time.
My partner and I believe that the cattle watering is causing some erosion that is adding to the water turbidity. Also, the area had experienced a long period of hot weather and the warm water is lowering the oxygen levels in the pond. Finally, the area that the pond is draining is largely unproportional to the surface area of the lake and this might be be causing a pH imbalance from the pesticides off of the fields. The intermittent stream may also be a factor in the poor aeration of this pond. That's all we have at this point. Thanks for responding!
-student96

I would look at the overall depth and weed growth.

Our overall theory is that oxygen levels are too low in the pond? Does this sound correct? Could it be due to an algal bloom?

It might be helpful if you could post all the information your teacher gave you-seemingly small details can make a difference, such as cloud cover, wind or lack thereof, acute changes in turbidity [did cattle just rotate into that field],etc. Wouldn't want to steer you down the wrong path.

You've got a lot of good ideas already. Develop a hypothesis, then test it against available data. In this scenario, it would probably be most helpful to start at the end....what do you think killed the fish? [Toxin/low 02/low pH/alQaida/etc]

Do some research into Biological Oxygen Demand.

Actually searching for biochemical oxygen demand will provide more results.

A couple variables stand out. 1. Fish gulping at the surface and all sizes dead next day. 2. Low pH of 4.7. This low pH value likely stresses the fish and makes them more vulnerable to other factors such as low DO. pH needs to be between 6.5 and 9 for healthy fish and invertebrate communities.
Cattle access to the water and maybe the stream can contribute lots of manure, and manure has nutrients (N & P plus others) to grow excessive plants that when decomposing, consume lots of DO especially at night. Is the water green with algae? Too much phytoplankton at night consumes lots of dissolved oxygen with lowest values at dawn. Decaying cattle manure also consumes lots of DO 24/7. Warm water holds less DO than cold water, thus the DO will be consumed faster ("less in the bank") when less is present to enter the night period.

You won't positively know the reason for the fish kill unless DO measurements were collected while fish were dying.
Stream water could be contributing to the low pH. Pollution spill upstream???? If pH of pond always 4.7 to 5??? This is not normal pH values for reproducing healthy fish communities.

Here is an analogy to use. What happens if you run an engine to hard/fast for to long. It stresses and breaks. Same for the lake. Bad conditions (water quality) , to productive (high BOD) and weather hot water then clouds and or cold rain. Turnover of lake ( destratification)causing low DOs.

Bill both phrases have the same max search results here - 200 for each.

Both are correct terms see

http://www.polyseed.com/misc/BODforwebsite.pdf

Eric, in reading that, I see no mention of fish or invertebrates. What catagory would they be placed? I'm assuming biological, but you know what assumed means.

Total demand is "all". All sources.

One one of the first things I always ask a pond owner is if they can identify the time of day they witnessed the piping, and possibly a time of day that the die-off event peaked.

It's very common for lakes/ponds with high nutrient loads to experience algal monocultures, which caught significant wax/wanes of DO, dependent on available sunlight. Very interestingly, all five fish kills I can remember around here that I witnessed in the last two years involved fish piping early a.m. one day, followed by an early a.m. die off the following day--presumably because the algae were respiring from the lack of sunlight.

It would be good and very interesting to hear the teacher's answer to the project problem. I hope the student returns with a summary of the answer and the teachers response.

My “Holiday Inn Express” Assessment:
"Evening piping" and the demise of ALL sizes and species of fish within a very narrow time-span indicates that an acute catalyst (versus a chronic condition) impacted the typical diurnal cycle, in which DO and pH normally peak in the evening.

Factors & assumptions for this assessment:
1) 4’ pond-depth is too shallow for stratification to pose much concern.
2) No weather events (rainfall, in-flows or extended durations of cloud-cover) were indicated immediately prior to the observed piping and large-sale fish-kill.
3) No abrupt changes to livestock watering-patterns and associated disturbances were mentioned. IMO, perimeter-usage by livestock represents an unlikely factor on a 6-acre pond.
4) The impact from extended hot weather periods is usually gradual and cumulative, and not so abrupt that fish of ALL species and sizes would succumb in unison due to temperature-induced DO issues.

With no other details regarding potential causal factors, I would redirect my focus toward the pond owner. Specifically, did the owner aggressively apply a fast-acting herbicide or algaecide to the pond (especially diuron, which is illegal for aquatic use) within 24-72 hrs prior to the fish-kill? If so, the rapid and large-scale die-off of weeds or algae will stimulate BOD and drop the pH as microbial degradation (of the dead biomass) accelerates – especially under warm-water conditions. Ultimately, this chain-reaction can easily (and often does) produce lethal DO-levels in a very short time-period.

Thanks to all for your help on this assignment! Finally finished at 2:30 am friday morning:)Will know next week what grade we got and hopefully the correct answer to the problem. Thanks again,
-student96

Oops! I failed to pay attention to the project's due date.
As Bill indicated, it will prove interesting to hear the "correct answer".
Please keep us posted.