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#540445 10/09/21 11:41 AM
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[Linked Image]Have a small 60' x 70' pond with minnows, mosquito fish, and crawdads. This is what the water has looked like the last 3 weeks (split pea soup) - even with adding some clean river water every few days. I have two larger ponds - 1/2 ac and 2/3 ac and never see anything like this in them. Is this a matter of too many fish (50 or so minnows, 500 mosquito fish, and unknown number of crawdads) for such a small pond ....................or ??

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That pretty rich water. Are those strings stretched across the pond to deter birds? Are you feeding the crayfish and minnows? Did you once grow other fish there with feed ... eg catfish? It's nutrient rich for sure. Fish and crayfish aren't going to make it nutrient rich (though their standing weight might be relatively high due to the richness of the water). Only you would know how the nutrients were loaded ... so .... from where did the nutrients come from?


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The strings are to keep the Cormorants out of the pond - seems to work pretty well and less labor intense than a large deep sea fishing net I was using before that.

Yes- I am feeding the minnows 3 times a week with some Purina Fish Chow ground up in a blender.

No other fish raised there except the minnows, mosquito fish, and crawdads.

The 2/3 acre pond next to this small pond looked like that the first year it filled and never since then.

The only other thing I can think of is there is a fairly new house a 100 yards up the hill that is on a newer style septic system - but I never smelled any sewage odor or noticed any wetness in the ground from the pond clear up to this house.


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I'm betting that there are no underwater plants in there to utilize the excess nutrients, so the phytoplankton stepped up to fill that void.


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Because the water in the pond has always been stained - yes, there are no plants due to no sunlight penetration I assume.

Can something like this lead to a fish kill if not corrected ?


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Originally Posted by Pond Star
Because the water in the pond has always been stained - yes, there are no plants due to no sunlight penetration I assume.

Can something like this lead to a fish kill if not corrected ?


Absolutely.


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You mentioned filling with water from the river ... so ... it kind looks like maybe it doesn't have much watershed and water is pumped to maintain level? If so then there is very little flushing of the nutrients you are adding by feeding and so they accumulate. Any idea of how much weight of feed you've added through the years?

If you witnessed a sudden intense bloom ... it may be that a fish/crayfish kill has already occurred. When I look at the image, the fish population is not evident at all. I am seeing thousands of GAMs (mosquitofish), for example, in most ponds that have them near me. They have predators in those ponds and yet the every square meter within a couple of meters of shore has dozens visible near the surface. The bloom is reminiscent to me of a nearby pond that fish-killed three years ago. Only mosquito fish remain as far as I can tell and their numbers are very sparse. My son and I went to see if the water had recovered this summer but absolutely no fish were caught on small flies (size 12). Nor were there any takes or nibbles. My son discovered the GAMs ... just 2 of them in a 2.5 acre pond. Was a very sad sight for us to see as only 5 years ago it was a vibrant fishery with lots of fair sized LMB and various species of lepomis.

Anyways, you have a hyper-eutrophic pond now and this is what you can expect if you don't do something. Get with esshup. He can tell you how to kill it out and then floc the nutrients to roll back clock a bit. Be ready to perform these tasks periodically ... especially if you continue feeding.


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Originally Posted by Pond Star
[Linked Image]Have a small 60' x 70' pond with minnows, mosquito fish, and crawdads. This is what the water has looked like the last 3 weeks (split pea soup) - even with adding some clean river water every few days. I have two larger ponds - 1/2 ac and 2/3 ac and never see anything like this in them. Is this a matter of too many fish (50 or so minnows, 500 mosquito fish, and unknown number of crawdads) for such a small pond ....................or ??

I use strings across my forage pond to discourage cormorants, as well. Seems to have kept predation way down.


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According to tamu, phosphorous comprises up to 8.5% of the weight of aquaculture feeds. I presume the highest quality feeds contain also the highest quantity of phosphorous due to the use of higher proportions of fish meal to source the protein content of the feed. It's not entirely clear if we could limit feeds like Optimal and Purina AM to this number. These are essentially pet feeds that are too expensive for fish producers to give any credible consideration to. Not dissing these feeds, its just they don't compete in any meaningful way for the production of food fish. They are pet feeds where the purpose isn't optimizing profits. Their higher prices justify the use of more fish meal (and phosphorous) and the consumer should expect its there (otherwise why pay extra for it?). In any event, it would be a nonsensical argument to claim than the recreational pet food is lower in phosphorous than say relevant feeds used in the production of food fish which are much cheaper and presumably of lower quality. Soooo ... I will use 8.5 % of dry weight to estimate the phosphorous added when feeding a high quality feed like Purina AM or Optimal.

So a common fertilization technique where free phosphorous is limiting the productivity is to add 1/2 to 1 gallon per acre of 37% phosphorous liquid fertilizer. This is sufficient to cause blooms of <20" secchi depth. Water that maintains such blooms is defined as hypereutrophic and of poor quality. Now such conditions are normal and even required to maximize production of food fish and this is also what many recreational fisheries are trying to maintain. But make no mistake ... the risk of fish kill is elevated under such strategies and efforts and expense should be undertaken to mediate the risk. Aeration for example. But in a pond with high water quality and low fertility, the effect of such a treatment appears to be temporary. The phosphorous is sequestered in living things and is only recycled when these creatures die. So the living creatures store it away in a greater food limited carrying capacity. A balance is reached by annual mortality which recycles phosphorous. The phosphorous freed by mortality stimulates production of the autotrophs which are sufficient food to fuel the replacement of that annual mortality .. something we call production. Its a beautiful cycle really ... a cycle of renewal.

As it pertains to us, feed inputs load nutrients into our ponds and this expands the carrying capacity (and yes even the annual mortality). It seems a rather widespread notion that feeding is necessary and can be carried on indefinitely. With the exception of myself and one other member, I have read absolutely nothing that encourages the curtailment of feed use when sustained eutrophic conditions are achieved. I would like to say I do not understand why that is but I the fact is ... anyone with any common sense can figure it out. As my grandpa use to say, "Just follow the money, there is your answer"

Pond Star, we can calculate the phosphorous addition to your pond from feed simply by dividing the dry weight of feed by the proportion of phosphorous in the feed. We can also relate it to a fertilization treatment. For example, if we fertilize with 3/4 gallon of 37% P fertilizer per acre ... we are adding ~2.25 lbs of phosphorous. An equivalent quantity is introduced with ~26.5 lbs of feed. Your 70x60 pond is 9.64% of an acre and so you would provide a treatment of phosphorous fertilizer for every 2.5 lbs of feed that your introduce into your pond. At this point it is unclear what quantity of feed your are feeding but to mimic monthly fertilization of 3/4 gallons of 37% phosphorous fertilizer you only need to add 1.33 ounces of feed per day or 4 ounces every 3 days. (this ignores the addition of other nutrients like protein, lipids, and carbs).

Pond Star, your situation could be exacerbated if your pond doesn't have much flow through. If it is an evaporation basin ... it retains nutrients except for those you move to your other ponds or what the cormorants might take. Even without feed, the river water could be very fertile and you wouldn't have to feed to have nutrients to accumulate to ridiculously high levels. So every pond is different in how it deals with nutrients and some can take more additions than others due to flushing of diluted water. But I think your pond could be more sensitive than most if it rarely runs over. I just wanted to give you an idea of how little feed it takes to make a pond hyper-eutrophic.

Feed is one of the cheapest ways you can grow fish if the density of fish is higher than can occur under natural fertility. Its highly concentrated nutrition. But its costs are not limited to feed. Aeration, herbicides, nutrient flocking, pond dyes, etc. are all costs of feeding and/or fertilization. Add all these costs to the cost of feed and/or fertilizer and then divide that by the weight of feed and this is the true cost of feed/fertilizer. The optimum efficiency occurs where the fertility of the water does not need these additional interventions and a person will never grow fish more cost effectively than when his pond supports all its fish with just its native nutrients and the Sun. If one will focus on working keeping his water's fertility limited to less than hyper-eutrophic conditions, there will be other benefits. Better water quality leads to longer life and faster growth. The key to working with water of any fertility is maintaining appropriate populations of fish. This is only made more difficult when pushing water into hyper-eutrophic conditions.


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jpsdad, let me get in touch with Optimal, I know their levels of P in the feeds is relatively low compared to other feeds.


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Originally Posted by esshup
jpsdad, let me get in touch with Optimal, I know their levels of P in the feeds is relatively low compared to other feeds.

Sure. I recall Dusty mentioning that he formulated a lower P feed that would still grow fish. So get us the numbers for both Optimal and that feed. Since we are talking P, might be great to understand what lower P really means for the feed. For example, what ingredients are being swapped out to produce feed with lower phosphorous.


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Originally Posted by jpsdad
Originally Posted by esshup
jpsdad, let me get in touch with Optimal, I know their levels of P in the feeds is relatively low compared to other feeds.

Sure. I recall Dusty mentioning that he formulated a lower P feed that would still grow fish. So get us the numbers for both Optimal and that feed. Since we are talking P, might be great to understand what lower P really means for the feed. For example, what ingredients are being swapped out to produce feed with lower phosphorous.

Since the claim is that Optimal relatively low compared to other feeds, we should get the numbers for them to.


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esshup,

I misread the tamu article. The percentage dry weight of phosphorus in feed is <1.5%. Semicolons and commas flustered my reading of the allocations. See an excerpt below:

Quote
Most fish farmers use complete diets, typically made up of the following components and percentage ranges: protein, 18-50 percent; lipids, 10-25 percent; carbohydrate, 15-20 percent; ash, <8.5 percent; phosphorus, <1.5 percent; water, <10 percent; and trace amounts of vitamins and minerals.

This is in the lower range for whole fish on a dry weight basis:
[Linked Image from researchgate.net]

Correct the equivalent feed rate of 2.25 lbs phosphorous per acre from 26.50 lbs feed/acre to 150 lbs feed/acre. That's a pretty big difference. Still its there and one cannot feed without increasing the nutrient load. Of interest, the vast majority of phosphorous in fish is in the skeleton, the fins, and scales. The rest is concentrated mostly in organs. Phosphorous is essential to the growth of fish and insufficient quantities in the feed can lead to low growth (basically due to not having sufficient nutrients to grow bones, fins, and scales)


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Get the soil checked. I bet it is very rich and the plankton bloom is a direct result of soil (nutrient) , light and water. It happens a lot.
















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I hate to muddy the waters but I am sure your crawdads beat me to it. They call them "mud bugs" for a reason. It's not a matter of too many fish, it's a matter of, too many crawdads.

Hopefully they are signal crawdads? As bad as signal crawdads are, any other species n your area would be worse and irresponsible.

Crawdads will voraciously feed on fish spawn. As a result, zoo plankton will increase and DO will decrease causing blue algae, like, gleotrichia to spike since it is a less desirable food source.

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Originally Posted by Joey Quarry
I hate to muddy the waters but I am sure your crawdads beat me to it. They call them "mud bugs" for a reason. It's not a matter of too many fish, it's a matter of, too many crawdads.

Hopefully they are signal crawdads? As bad as signal crawdads are, any other species n your area would be worse and irresponsible.

Crawdads will voraciously feed on fish spawn. As a result, zoo plankton will increase and DO will decrease causing blue algae, like, gleotrichia to spike since it is a less desirable food source.

If it was crawdads, the water would be a lot more muddy looking vs. the split pea soup color.

jpsdad, given that there is P in the food. how much of that P in the food is retained in the fish? (to grow the bones, scales, etc.)

From the Optimal Website:
Optimal Bluegill Junior P min 1%
Optimal Bluegill P min 1%
Optimal Bass P min 0.75%
Optimal Hand Throw P min 0.75%
You can see the complete label (levels of Protein, fat, etc) on the Optimal Website store.

The low P feed is specifically made for a pond management company. It isn't on Optimal's website.
The label reads:
Min Crude Protein 42%
Min Crude Fat 10%
Crude Fiber (max) 4%
Phosphorus (max) 0.9%
Ash (max) 8%

Last edited by esshup; 10/12/21 10:29 AM. Reason: Updated the information

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Originally Posted by esshup
jpsdad, given that there is P in the food. how much of that P in the food is retained in the fish? (to grow the bones, scales, etc.)

That's a great a great question esshup and its one that I have been seeking. Its complicated but I will share some things that I am learning from available research documents.

First, it in part it depends on the fish. Some fish put more investment into the structures that require P. For example, BG and LMB put more investment into scales, fins, and bones than to rainbow trout.

Second, it "might" partly depend on the concentration of P in the feed. One reference stated findings that a reduction from 1.2%P to 0.8%P led to a 33% decrease of P in effluent in a rainbow trout facility. Interesting thing is 0.8 is 1/3 less than 1.2% and so it would seem the amount retained is to some degree dependent on the amount consumed.

We can make a ball park estimate of P retained from FCR. For example, for 1% P feed with FCR of 2 and a fish whose dry weight is 20% and whose dry weight concentration of P is 1.5% the P Consumed and retained is:

Pcon = .01 per lb feed consumed

Pret = .2*.015/FCR = .0015 per lb feed consumed

So the proportion retained is:

PropPret= .0015/.01 = .15 or 15% is retained, 85% discharged in feces

This proportion of retention keeps pretty well with the 10% assimilation rule. In the example above, the proportion of P in feed is less than that of fish and so the calculation is greater than 10% retention. It is probably more accurately somewhere between 10% and 15% retained and 85% to 90% discharged.

Some other interesting facts. Increasing P in feeds creates leaner longer fish and reduces conversion efficiency (increases FCR). Decreasing P in feeds creates fatter (higher lipid content) shorter fish and increases conversion efficiency (lowers FCR). Above we a assume a minimum P is present in the feed below which the metabolic needs for P are not met. This particular circumstance is very interesting to me. A low P feed might produce slower growing ... more energy dense prey for predators than a high P feed. A high P feed might produce fish more capable of reaching trophy potential because it better builds the frames trophy fish have.

There is a lot more to learn here. But some of the answers to questions I have be exploring are coming to light. One of things I have learned, for example, is that harvesting fish cannot meaningfully control P additions unless the P additions are pretty much the same as P in the harvested animals. For example, feeding 100 lbs of feed will add 50 lbs of wet weight fish to your pond but to remove the P of 100 lbs of 1% P feed one must remove more than 300 lbs of wet weight fish (whose dry weight P is 1.5%). So I retract any prior statements that fish harvest is part of adequate control of nutrient accumulation. It hardly makes a difference at all. One of the keys to science is to listen to evidence and to allow evidence to reshape one's thinking. One must be ready to abandon a preconceived notion ... no matter how much sense it seemed when first conceived.

The evidence clearly demonstrates there is no way to manage P introduction with harvest unless other organisms convert the P in feed excrement into food for the harvested fish. In the example above, this would require a whole pond FCR of .333 where 250 lbs of the gain from the necessary harvest came from pond organisms utilizing the waste P. What this tells us is that P addition requirements are very low in a harvested system where Sun and native nutrients are providing the food for growth each year. Most systems naturally accumulate more P than required to replace the P in harvests that are appropriate for balanced populations.

Last edited by jpsdad; 10/12/21 04:13 PM.

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Thanks for this twist on the difficulties of nutrient management, specifically phosphorus, in our ponds, jpsdad.

This begs the question of what else can we remove/harvest to diminish P? Say we target unnecessary vegetation. I pull FA and elodea each summer from our 1/4 acre BOW, as in many hundreds of pounds wet weight. This probably helps. It would be informative to understand just how much benefit we are achieving through this unpleasant task.

What else could a pond owner remove other than fish, crayfish, and bottom muck to lessen the nutrient loading? We pull some thousands of gallons of water from the pond each year for irrigation purposes, replenished by rather infertile Dolores river water. There is no irrigation runoff returning to the pond.

Thanks again for your scientific analyses of many topics on this forum. I'm able to follow along, and to gain insight into all the subjects you consider. We're very fortunate to have you participating.

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I struggle with scummy floaty "stuff" in my 1/4 acre pond. It looks much like yours, often, during the warmest parts of the summer. This is my uneducated guess as to what is going on with my funky outbreaks...

My pond's info,

- 1/4 acre, 10 foot deep with mostly steep banks.
- Excessive water shed (about 20 plus acres) that really flushes the pond in the spring and sometimes fall.
- 24/7 aeration, about 4 turnovers pew day(does not run during the winter months).
- Muddy from crawdads and possible ground water run-in (even though it is not a ground water pond).
- No submerged vegetation. Likely due to the muddy waters.
- Ample emergent vegetation along the 100' dam, but little elsewhere due to the steepness and young age of pond.
- Previous water tests show low to non-existent nitrates, ammonia, or phosphates...PH consistently between 7 and 8.
- Very little wind action and limited sunlight due to being surrounded by trees on 2 sides and a rather high dam on the third side. Rain or wind action can dispel a surface outbreak for a day or so, but once this action ceases...it comes back quickly during the hot months.

I believe there is enough nutrients in the pond as a whole to support blooms of various kinds, but not enough clarity to support them much below the surface. Due to the aeration, these blooming organisms get exposed to the surface and grow enough to "head to the light" or surface where they float and prosper, and often get really nasty looking. Once the heat of the summer passes, the pond stays mirror like on the surface.

Keep in mind I said "uneducated", but the above are my moderately experienced thoughts on the topic.

Here's a nice guide to pond scums that might help...

https://www.townofchapelhill.org/home/showdocument?id=28866

I have often thought about clearing the water with Alum (or whatever) to promote some submerged plant life, but I have not convinced myself the money and effort would pay off due to the excessive water throughput. I do trap out the crawdads daily during the summer months (for the last 2 years) and I have seen no clarity improvements even though I took out over 1500 last year and over 1000 this year (3-5 inches long).


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I updated the feed info.


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Originally Posted by 4CornersPuddle
Thanks for this twist on the difficulties of nutrient management, specifically phosphorus, in our ponds, jpsdad.

This begs the question of what else can we remove/harvest to diminish P? Say we target unnecessary vegetation. I pull FA and elodea each summer from our 1/4 acre BOW, as in many hundreds of pounds wet weight. This probably helps. It would be informative to understand just how much benefit we are achieving through this unpleasant task.

I think it definitely helps much more than removing fish from a population that one is maintaining balance. The wet % of many aquatic plants are in the 90ish range but with say 800 lbs from your 1/4 acre bow we are talking in the neighborhood 80 lbs dry or 320 lbs dry weight to the acre. Compare that to 15 lb weight fish harvest (60 lbs/acre) where the dry weight is 12 lbs/acre. Plants require phosphorus so you know you are removing at the very least what it took to grow the amount you removed. To be certain you could weigh a sample, then sun dry it to understand it's dry weight content. This sun dried sample could be sent to your state's agriculture lab for analysis just like you can do for hay. This would be a way to make a very good estimate of phosphorus content removed from a wet volume or a wet weight measurement. Alfalfa hay has ~0.21 % phosphorus and so I think that might be starting place to make a roughish estimate. I may have underestimated the wet weight of what you are removing. A quarter acre could grow much, much more than that. I read the other day an author's estimate of phytoplankton production in catfish production ponds over the growing season. It was in the tens of tons per acre. So a lot of detrital rain are in these heavily fed production ponds. Zooplankton are just not able to keep up with it..

Quote
What else could a pond owner remove other than fish, crayfish, and bottom muck to lessen the nutrient loading? We pull some thousands of gallons of water from the pond each year for irrigation purposes, replenished by rather infertile Dolores river water. There is no irrigation runoff returning to the pond.

I love strategies that use the nutrients. For example, I think your use of the enriched water for irrigation is a great idea. I like organisms that prevent the accumulation of muck. Such organisms like crayfish and TP are literally able to convert this material into edible flesh. I like that too. At sufficient density, these organisms expose sediments to help get nutrients suspended in the water column. So together with flushing they certainly have potential. Though your pond may be too cold for TP when the Dolores water comes through it ... TP are absolutely amazing. You can't hurt a pond by taking them out at the end of growing season so the only limit is how much the pond can grow. They will reach harvestable size ~6" in as little as 90 days from hatching. So TP (in monoculture) can produce up to 1500 lbs of fish just on rich water. They can grow in cages at remarkable rates ... unfed ... except for green water flowing through the cage. 1500 lbs/acre, if fully harvested, will remove 300 to 350 lbs dry weight/acre AND make a lot of meals. If the feed is 1% P and TP 1.5% P then this is like removing 450 to 525 lbs/acre of feed from the nutrient store of a pond. The effect would be greater if the dry weight percent of P in tilapia is greater than 1.5% ... and the probably are. Any organism that feeds very low on the food chain and can achieve high biomass is a candidate for such nutrient sequestration. In essence, you are already doing this at the primary level by removing primary production biomass of elodea and FA.


Quote
Thanks again for your scientific analyses of many topics on this forum. I'm able to follow along, and to gain insight into all the subjects you consider.

I appreciate this. I would just say something that I have said before. I have taken much more from here than I have given. Pretty much everyone here has shared experience that I value in the same way. Your comment encourages me and it lets me know participating is worthwhile. Thank you for that.


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That is a lot of crawdads on your bow, Quarter Acre. As much as I love a good crawdad boil, I would never put a mud bug in my pit. They are the most detrimental species in a closed system.

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J
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J
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Some interesting numbers. See links below.

https://feedtables.com/content/fish-meal-protein-65

https://www.sites.ext.vt.edu/newsletter-archive/dairy/2006-07/phosphorus.html

The Dry Matter % of P in fish meal is ~2.86. So if a feed is 1% P it probably contains less than 1/3 Fishmeal. Since fishmeal averages 65% protein, the fishmeal contribution to protein would probably only be 21.66 or little over half of a 40% protein feed. This would mean that 67% of weight of the feed must contain 18.33% of the total or be 27% protein itself. This could come in part from meat byproduct or soybeans. It would probably mostly come from one or both of these two sources. Both are relatively low in phosphorus but each have some and so do other materials. So a 1% P feed probably doesn't contain fishmeal as the primary component by weight. In the end, does it convert to fish and are you satisfied ... that's what matters. They continue to break ground on fish meal replacements and this can only help reduce P loading.


Common sense is not so common - Voltaire

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers


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A
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Originally Posted by Joey Quarry
I would never put a mud bug in my pit.

What do you do to keep them out of your pit?

Is there some sort of fundamental difference between a crayfish that moved from the creek to the pond of its own accord,
and a crayfish that was snatched out of the creek and tossed into the pond by a human?

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I'm with you Augie. They're probably in Joey's pond whether he wants them there are not.

While the crayfish experience wasn't what QA anticipated I am hard pressed to conclude it was any sort of disaster. More than 200 lbs of crayfish have been removed as potential food, vastly more than he could have ever harvested in fish keeping the fish population balanced in a 1/4 pond. This doesn't take into account the forage they provided. Crayfish just aren't ideal prey for HSB I guess and so populations reached higher levels than they otherwise would have with a predator more suited to preying on crayfish. I recall Lusk posting that crawfish supplemented as forage don't last long in a trophy LMB lake. This may be because they are higher energy density than BG and easier to capture than BG. According to Lusk, LMB while stop feeding in BG when crayfish are abundant. The CC and BG in QA's pond will eventually gain the upper hand on them. Meanwhile, I would bet that QA has had very little accumulation of muck thanks in part to the crayfish. As with everything balance is key and a lot of all of this depends on goals.

I have considered, for example, using crays simply for production of personal food in a yearly cycle in combination with TP in a small pond. Harvesting the crays around June 1st (reserving a sufficient number of females and males for restocking in holding water) at which time a specified number of TP hatchlings go in. By October the TP are ready to harvest and have produced a couple of broods. One would remove the adults (reserving sufficient numbers to produce next years crop of fry) and later in December return the goldilocks number of adult crays to produce a crop of large harvestable crayfish ... they would convert the dying broods of the harvest TP. Things that can go wrong? Too many crays survive the TP ... so I am sure it would be a learning curve.


Common sense is not so common - Voltaire

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers


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