Why do fish behave differently in ponds than in large natural systems?
Excellent question. Let's explore that, shall we.......
Whether it's gamefish like bass or walleye.....
Or Watergarden friends like goldfish and koi....
Freshwater fish (and marine fish too) behave differently in small spaces than they do in their natural, much larger, native habitat.
There is stress that comes with living in close proximity to not only your fellows of the same species, but your food, and potential competitors. This creates special challenges that we, as responsible managers of our resource, get to deal with.
If your pond is larger than 3 acres or so, these stresses are easier to handle, as there's usually enough space to go around. Alas, when things go wrong in these larger systems, they are much harder to fix..... In most cases, they require years to balance out and can be labor intensive and/or expensive.
For the rest of us, we need to manage just about every aspect of the fish's life cycle in order keep them happy and healthy.
I often come across ponds that have stunted fish, or way too many fish. Here are some indicators that I have seen that tell you, you need to change your management strategies to bring your pond back into balance.
Roaming packs of predators:
Normally, solitary predators like Largemouth and Smallmouth Bass and Northern Pike do not travel in groups. If you walk around your pond and see marauding packs of bass, that means there is not enough food in your pond, or you have too many fish.
Stunted fish & Overabundance:
I hear customers comment everyday that they only ever catch/see small fish. It is up to you, the property owner, to keep the size structure of your pond in balance. This means: harvest small fish so that you can grow a few larger ones. You should almost never be able to catch a fish with every cast. If you can, you have too many hungry fish. Your pond can only naturally provide so much forage. Even if you feed them or stock forage (minnows) on a regular basis, most any pond can get out of whack in terms of how many small fish reside in the system.
Small ponds are fantastic incubators for small fish. These small habitats lack the natural predation and other factors that cull young fish in lakes and rivers. The problem lies in the lack of large fish to control the reproduction of small fish species. For example: you need a 16in Largemouth Bass to eat a 3in Bluegill. If you do not have any large bass, or very few large bass, too many Bluegills will survive to reproductive age. This will continue until there are too many sunfish for your pond, and their growth will stunt due to shortages of food and habitat.
Remove the less important fish from your pond so that the rest may become larger and healthier. Take out a bunch of 8-12in bass and 3-5in sunfish so that the food they would have eaten is now available for the larger fish in the system.
In watergardens, too many fish looks a little different. In these very small systems, overabundance presents as algae blooms and disease problems. Koi and Goldfish like to school up. They are both related to forage species (minnows) and are comfortable in large groups. The potential issue resides in the lack of habitat and water volume.
If your pond is 20x20 the above picture represents WAY too many Koi.
The problems for Koi ponds are very similar to those found in professional aquaculture (or fish farming). When population densities are very high, disease and parasites can run rampant. The aeration system and filtering waterfalls cannot possibly keep up with all the fish waste, so your nutrient levels get too high and oxygen levels drop. This all leads to vulnerable fish susceptible to infection and death.
Lack of Good Habitat:
Most small ponds never have enough good habitat. BFR's (big fu&$ing rocks), coarse woody debris (stumps and large branches), and submerged vegetation are the best and easiest ways to give your fish a place to relax and ambush their next meal. You need to provide habitat that closely resembles what your fish would find in their native range. These creatures have evolved to live and utilize a variety of structures. When they cannot find suitable habitat, they will constantly look for it. This search leads to stress, and no one likes to be stressed (kind of like when someone removes the coffeemaker from the break-room, productivity suffers...everybody's stressed out).
Long story short, make your pond resemble a natural waterbody.
I think here is a good time to talk about Mother Nature. She is a colossal bitch! She is undefeated and stubborn as all get-out. Cross her at your peril..... Any waterbody that is managed not in concordance with Her will, will be summarily punished. These punishments come in the form of costly weed and algae treatments, sick/dead fish, and little joy to be taken from a pond that is trying to run outside of the rules set up by a tyrant that's been operating since time in memorial.
I'm SURE Ms. Nature will make me pay for these comments, so I hope you all appreciate the hit I am taking for you! (Tell Mom that I love her....)
Mother Nature has set up her fish minions to live, grow and reproduce in environments best suited for their needs. Most of the ponds I know about fit only some or none of those needs naturally and therefore need to be managed properly in order to produce large, healthy fish.
What does that mean for you?
Aeration, habitat, and population control.
Properly aerating your pond will triple the carrying capacity of the system. Among plentiful other benefits that a good air system brings, it creates an oxygen-rich environment that is the base to any good, stable food chain. This high oxygen environment can also reduce the mortality of our scaly friends due to improved vigor. That is, a healthy, strong fish can fight off disease and is less susceptible to parasites because it has a less stressful environment with plenty of food and habitat.
Aeration can also help out a Koi pond. Aeration systems are cheaper to run than your filter falls (though running falls as much as you can will always be the best option) and will provide oxygen to the very bottom where it is needed the most.
Here's some good aeration systems:
There are many other strategies that produce big healthy fish, and I will delve into those on a subsequent article, so stay tuned.
Thanks so much for taking the time to read this. I have only been able to graze the surface of a lot of these topics here on this blog, so please ask questions in the comments section. I will be able assist you more specifically with whatever your current issues are.
Just remember, when in doubt.........