Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Reducing fish biomass

A customer needed to reduce some of the fish biomass in his 1/2 acre pond. We will do the same thing within 7-10 days. It was a marathon fish cleaning session as he hasn't cleaned any fish in a long time and was trying to re-learn how to do it. Dull knives, small fish cleaning space, etc. all made for a 4+ hour cleaning session. That and I was trying to teach him how to fillet all over again. He was getting the hang of it by the time we finished, and he's got a Bubba Fillet Knife on order. That will be here tomorrow.

We caught (in the span of 2 1/2 hours) the following:

12 Yellow Perch, all between 12.5" and 13.25" in length, from 1# to 1.35#
8 LMB One 1 1/4#, all the rest between 4# and 4.2#, all were 18"-19" long
35 HBG, all between 9.25"-10.25", and between 1# - 1.2#
2 HSB both right at 4# and IIRC 21" or so.

All fish were caught on a redworm or a 1/64th oz pink jig head and a wax worm. All 2.5'-3' below the surface.
Cooler 1


Cooler 2


Cooler 3


HBG


HBG Wt


HSB


HBG


YP1


YP2


YP Wt

Are some of those YP full of eggs??? If so, what are you doing with the 'caviar?'

Great report!!

So, what was the deal with that one skinny LMB? Same length, but way low on weight?

Caviar was cooked. 2 were males, all the rest were females,but not all had the same degree of egg development. 3 females were empty - they spawned already.

The one LMB had a plastic "creature" in it's intestine that it couldn't pass. It had to be like that from last Fall.

Now that is definitely removing biomass! Pretty awesome esshup. ~93 lbs harvest from a 1/2 acre pond in 2.5 hours. What did the 4 lb LMB take, was it the redworm or jig or maybe both? Were the LMB feeding on forage or are they also eating pellets? Anyways well done there. Time to grow more now. That frees up 180 lbs of Optimal BG to grow the next batch. I am just curious. The next harvest in a week. What is the goal and what do you estimate will be remaining?

Very nice! I'm about ready to go through that same exercise on my pond, but in the interest of time, I'm going to use a fyke net to do the catching.

That seems UNREAL! My quarter acre pond wouldn't produce 10% of that biomass.
How does he/you achieve that production?

It's gotta be a feed program....

All fish hit on both presentations. (2 people fishing).

I honestly haven't sat down and put pencil to paper on the total fish biomass. A quick SWAG says there is a minimum of between 600 and 1,000 pounds of fish in that 1/2 acre pond. It has an average depth of 10 feet and he pays attention to water quality parameters. He has the means in place to add enough water to flush excess nutrients out of the pond.

The goal is to reduce the biomass in the pond to allow water quality to stay high without intensive management.

The pond has steep banks so there is minimal fish reproduction in the pond.

Augie, a fyke net works great but I have found that it doesn't work very well if you are targeting any of the bass species including HSB.

There is very little production in the pond from the stocked fish - the bottom is clay and the sides are VERY steep - steep enough that the fish can't make beds.

He feeds the fish daily and he adds Fatheads & Golden Shiners in the Spring and Fall. Like I said earlier, he keeps close track of water quality and has the ability to add water from a well to flush out excess nutrients. He has a Vertex Bottom Diffusion aeration system plus a Volcano type surface agitator that he runs when the water temps are 70°F and above so the O2 stays high. He doesn't add Tilapia but he does use a peroxide based algaecide. When the algae floats he kills it then turns on the water and flushes it out of the pond before it sinks and decomposes.

Water clarity stays 18"-24" most of the year due to a number of 24"+ koi in the pond.

I'm primarily looking to substantially reduce the BG numbers and get a good sample of YP numbers.
I can't have more than 10 HSB left. Those fish are super easy to catch on rod-n-reel so I'm ok with them avoiding the net.

Thanks esshup. That is some focused management, and not what I could pull off with our pond.
Good on him.

esshup,

I "think" I remember you talking about the same pond many times before. Is this the pond that is fed water from the tile system of the surrounding fields? Also is this the pond where mother nature intervened taking a good number of 2 lb HBG? Also, is this the same client that is trying to keep RBT alive into the summer months?

Anyways, is there any way to estimate how much this client is feeding annually? For example, are you supplying the feed? That would be a great number to share with all of us and the brand/protein content of the feed being fed.

No to the tiles, yes to the RBT and he was able to do it 1 year.

I will ask about the food as I will be there next week.

As to the amount of minnows stocked, last 2 years it was 120# Fatheads, 120# Golden Shiners total, split between 2 different stockings.

esshup,

Your results certainly do sound like an extraordinary amount of biomass for a small pond.

However, we are all used to ponds that have a "normal" distribution of fish sizes.

If the pond literally has zero reproduction of LMB, BG, and YP, then might all of the biomass be tied up in a few big fish and not as badly pushed against the impending crash line as we expect?

(I know that a few big fish would account from much more biomass than countless little fish. But how about a pond that essentially has zero "medium-sized" fish for each of the existing species?)

Rod, you are probably correct. We have not caught a BG less than 9" in the pond, but that may change as water temps warm. That may take a while as it's currently 36°F and snowing now at 11 am.

With lower visibility and very steep banks there really isn't any place for reproduction.

esshup,

I look forward to your updates on this pond. It will be interesting to see if you do sample some fish over the course of this year that indicate the degree of reproduction in the pond.

There have been threads on Pond Boss where there was no potential habitat for channel catfish to reproduce, yet there were little CC in the pond. Life always tries to find a way! I wonder to what degree it is possible to suppress LMB, YP, and BG reproduction? I would imagine that BG would be the most irrepressible. I wonder if it makes a difference that they are Hybrid Bluegill?

Finally, there are lots of people on Pond Boss that post to try and create a "trophy" fishery. I wonder if someone could re-create this pond with even more severe restrictions? I was thinking of steep banks with pond liner run down to the bottom. If you inhibited all spawning, then you could ladder stock your trophy species. However, I would imagine you would need a separate grow out pond to annually introduce enough forage. However, that way you could have some control on the size of the forage to maximize growth of your trophy fish. Maybe even need two grow-out ponds?

However, imagine the filamentous algae problem in a pond with zero rooted plans going down the side slopes! Maybe tilapia would be one of the trophy fish.


P.S. I do appreciate your posts about the ponds you have under management or semi-management. Usually, you have made one big change to the pond and then document the effects for a few years. That is great for amateur pond owners to learn from, since that is how most of us are able to manage our ponds.

FishingRod,

I am not sure if your reference to impending crash line refers to oxygen depletion, ammonia concentration, other factors, or all or many. Anyways did want to contribute some context because I know you will appreciate it.

Fish use oxygen but this isn't where the risk of oxygen depletion comes from. Usually this risk either deals with excessive plant respiration at night or deals with the oxygen consumption related to decaying organic matter (like an algae or plant die off or the mixing of accumulated organics previously stored in an anoxic bottom layer). The standing weight of autotrophs usually always greatly exceed the fish weight and so they influence DO drawdown more than fish do. Also bacteria probably almost always have a greater standing weight than fish do depending on the load of decaying organic matter they have available for consumption. Generally speaking, the conditions that would cause fish kills would happen without the fish oxygen demand. IOWs managing oxygen depletion fish kill risk by managing the numbers or biomass of fish is not an effective measure.

jpsdad,

Thanks for the clarifications. I was just working off of the title of this thread. I just assumed that esshup and the pond owner were worried about exceeding the carrying capacity of the pond and suffering a fish kill due to the myriads of possible reasons.

You're welcome FishingRod.

I agree with regard to carry capacity and natural mortality resulting from the effects of food limitation. Harvesting fish should reduce this type of mortality significantly. Only thing of course is that the mortality happens anyway whether harvested or not. But it far better for that mortality to be in the fridge than rotting in the pond. Fish reach the carry capacity fairly soon after the initial stocking (usually subsequent year) and so their growth in weight slows to be equal to the weight of the mortality. In that sense, harvest is means of helping fish grow. You brought up a really great point above. About how a few large fish equal far more numerous smaller fish in weight. So the removal of few large fish can indeed create a lot of room for subsequent growth. When most efficient, there will be just enough smaller fish that stand a good chance to evade predation replacing those removed. IOWs the population remains stable but the removal of the few large fish lowers the standing weight below the carry capacity each year allowing for growth into the carry capacity following harvest. This allows the surviving fish to grow individually. The key is mortality, whether natural or harvest, but preferably harvest. I would bet that esshup has a plan for replacing the large fish being removed with smaller fish that are not likely to be consumed by predators in the pond.

I might be wrong, but my impression differed just a little from yours. I don't think the pond owner was aware of the need to harvest without esshup urging. It's really good advice that esshup is providing to the pond owner and this is going to be very good for the pond's fish. Had the pond owner over the years harvested and restocked replacements, it is very likely that the ultimate weights achieved would have been higher ... as remarkable as they were anyway. All the remaining fish will grow better as result of this action.

Since FA first grows on the bottom, if sunlight penetration is limited due to a phytoplankton bloom or dye, then in a pond with very steep sides, there won't be much substrate that it can grow on. Phytoplankton could be a much worse problem in such a pond, but in this pond, the owner uses a peroxide based algaecide, then turns on the water to flush out the dying algae from the pond - helping to mitigate nutrient loading on the pond.

In this pond, the owner knows that harvest is an integral part of pond management, but knowing and doing are two different things. So, me going there to harvest got him out there harvesting too, and me being there also helped him to remember how to fillet fish. He was having a problem with that (I believe) and that was part of his reluctance to harvest fish. Why harvest when you can't clean them? I showed him some different ways to do it, and he ordered some tools to help him fillet easier than what he was attempting prior. He says that the fish from cool water taste better than fish from warm water, so the main harvesting time is now and late Fall. Winter typically would be a great time to harvest the fish through the ice, but we only had a 1 week window this year where there was safe ice.

The pond owner used to grow Koi, and he has a large live rock saltwater aquarium in the house that he maintains himself, so he is aware of water quality issues and how that will impact the fish in the pond.

He has Walleye in the pond too, and since we saw a white grub on one of the HBG, AND he's never caught a RES out of the pond even though we've stocked 700 RES between 2.5" and 6" over the past 4 years, we are going to put in another 500 of the biggest ones I can source this year. Hopefully the WAE don't eat them all. He caught a WAE that was either 22" or 27" (I cant remember) last Fall and returned it to the pond.

Thanks for all of the updated info.

However, the sentence above caught my attention. When I see people talk about "cool water" fish tasting better, I thought they were referring to the species. For example, I think walleye and YP are two of the tastiest North American fish that I have eaten. I definitely have not noticed a taste difference based on the actual water temperature. But I generally fish when I can get out of all of my other duties.

Does anyone in this thread definitively note a taste improvement of their fish on the table when caught in cool water compared to warmer water?

Well you had to say definitively, LOL. I am more or less like the BOW owner, I prefer fish caught in cool water. The flesh seems firmer and there are not so many odd smells like the when the water is warm enough to take a bath in. LOL. There doesn't seem to be as much in guts as they are eating less or less frequently. I like to fish throughout the year but most of the fish I keep are from October through April.

Talk to Bill Cody. There are warmer water algae that will impart an "off" flavor to fish.

I think it has a LOT to do with how the fish is handled after the catch.. Iced water in livewell? Fish on a stringer setting in shallow warmer water maybe.
I pour a bag of ice into cooler with fish on way home, meat stays firm.

I believe whatever the fish are eating that time of year has the greatest effect on taste, certainly how the fish dies & is kept afterwards. Immediate icing best & certainly can't hurt nor:

https://en.wikipedia.org/wiki/Ikejime

Somewhere on the Web I watched a video of a women who enjoyed raw fish. She noticed the difference in taste & texture between Ikejima & a normal slow death of a fish. It is easy to learn to do & a modern ikejima device can be found on eBay.