Many times I have clients ask me:
"Why don't I have any big fish?..."
Or, "All I have are a million stunted fish..... . "
Or, "Why don't my koi/game fish reproduce?..."
In small systems (waterbodies under 5 acres or so), it is necessary to manage your fishery to gain, then maintain, large fish in abundances that are healthy.
This discussion is mostly focused on bigger ponds, but the theories work well for the water gardeners out there too.
Small ponds are most of the time closed systems...very little movement in the way of new organisms entering and leaving the system. This lack of recruitment poses a problem for ponds; this leads to shortages of forage and cover.
There is only so much food a pond can produce by itself. The insects, frogs, and small fish (forage species like fathead minnows, shiners, etc.) that make up the bulk of the forage base are finite, and in most cases.... limited. So, it is up to you to balance the fishery and make it more self-sustaining.
If you have a 3 acre(ish) pond or smaller... all the way down to the 500 gallon watergarden... the small forage species have nowhere they can hide for long (unless the pond was constructed with abundant fish habitat as its sole purpose). These systems provide no constant sources of food. This leads to protracted periods of time between the availability of quality meals, thusly leading to poor growth and condition of your fish and next to no reproduction.
What to do:
1. Provide cover.
Big Fu&%*ing Rocks:
This means large rock piles with big gaps between the stones (known affectionately as BFR's in the fishery community). These not only provide cover for smallish forage (like crayfish), they are also a favorite hangout for most species of gamefish. Small rocks are for wimps.....and communists...and landscapers, BOOOOO.
Large woody debris:
While sinking your old Christmas tree in the pond is great for the wee tykes of the pond, it's not awesome for the lunkers. You need large stumps, fallen trees, stacked logs. These provide the large gaps for fish and insects, as well as the preferred cover for bass. If trees aren't your thing, try sinking some stacked hardwood pallets...
Fish always relate to where the food hangs out, as any fisherman will tell you. Aquatic plants are vital for cover for all fish in small ponds, as well as a source of sustainable food for the entire food chain/web. Please allow aquatic plants to colonize your pond.... At times they can be a pest, and we can control them if necessary, but they are the hardest working organisms in the pond; not only for your fish, but for water quality too. I will post an entire article about this soon..... stay tuned (OOOOOOO, I can't wait!)
2. Provide forage.
Feed your koi, and they'll be happy. They are also very good at rooting around and finding sustenance for themselves, as they can eat just about anything (like goats... but more colorful).
Feed your gamefish too. Just about all hatchery reared fish were raised on pelletized food. They can be converted back to that kind of sustenance, but I hate that. Ideally, stock your pond (twice per year) with whatever your most available forage species are. Around here it's fathead minnows.
These critters can reproduce two or three times per season (under good conditions),and they are kinda dumb, which makes them very available to be eaten. Whatever your forage of choice, make sure to stock enough that they last long enough to reproduce at least once in your pond. It is harder than it sounds, as most ponds lack the cover needed to make reproduction successful. The rates at which I usually recommend are 100 lbs of minnows per acre, twice per year. Now, this is an expensive proposition as these fish are about 5-6 dollars per pound, so it behooves you to upgrade your habitat to make your forage last longer.
3. HARVEST YOUR FISH!
Every fishery on this planet is harvested regularly. Whether it's by natural predation or by the knuckle-dragging human consuming machine, fish get removed from the resource.... and that's OK.
It's actually more than OK; it's a vital function of the food chain/web. Mother nature never intended there to be more predators than prey. In fact, if the balance shifts even slightly, whole fisheries can collapse under the weight of tertiary predator dominance. In other words.... Too many predators = unhealthy (at best) fishery/ecosystem.
In a balanced system, the total biomass of the fish population is concentrated in the youngest and smallest of the fish. To state that differently, if you own a 1/4 acre pond and you have more than 2, 4 lbs of bass living there.... that's out of whack and therefore unsustainable. Your food/energy/mass diagram should look like a triangle where most of the available biomass is concentrated on the bottom, leaving ample food for the few (very few) large predators at the top.
The above pic from the internet (pssst, that's where I get most of my pics) illustrates the concept well. Now imagine that the top of this pyramid (the fish) is expanded where it's the smallest fish at the bottom and your Bass, Pike, Trout, Salmon, Sharks, Whatever.... are at the top, the same theory applies.
This concept was the basis for like.... three college courses, so I fear I'm getting too far into the weeds here. (get it..... weeds....Plants,Plants,Plants,Plants,Plants,Plants, anyhoo...)
Ahem... Catch some fish! They are great on the grill, deep fried, or fertilizing a tree somewhere. Too many predators spoils the potential for the gloriously large specimens that is the potential for ALL ponds. There are WAY TOO MANY ponds out there with a marauding pack of a dozen 10in bass. Remove the biomass so it can settle into the largest and smallest fish. That way your reproduction is good, you select for the best genetics, and everybody has enough to eat.
Koi ponds are no different. There is only so much biomass that a watergarden can sustain without becoming a cesspool. If you have (or want) large koi, remove the smallest (or least attractive) of the bunch so that your bestest pals can get even bigger and more enjoyable. With more abundant food and space the Koi will be healthier, grow faster, and have brighter colors.
A combination of these three points will maintain an environment that is conducive to/for big fish, all while maintaining a healthy ecosystem for your pond. This is a huge complex topic, and I have much more to reveal for you with upon request or as I come up with topics that I want to share, so please ask away.
Thanks again for taking the time....