Hatchery ponds, much like any intensive fish farming pond, are unique in that they are regularly, completely harvested. Other types of fishponds are only intended for gradual harvests, rather than as many fish as possible coming out at once. This can be a difficult or easy task depending on how well the ponds are designed to accommodate the work. Putting in a few extra features, including a durable pond liner, can reduce or eliminate the need to drain the pond when harvesting fry or hatchlings. If you do prefer to drain water out at least seasonally, keep these challenges in mind to prevent damage to your ponds.
Building Secondary Harvest Structures
Adding harvest structures directly to the shape of the pond will require a little extra work during installation, but it can pay off tremendously with higher survival rates during harvest and transport. Harvest structures are commonly known as kettles and are generally designed as lower boxes or pools at the bottom of a production pond. As the pond is drained, the fish gather in the water that’s naturally trapped in these lowest points. This has been a traditional way of harvesting fish for centuries, but it’s usually improvised with fish getting trapped in puddles that are naturally left behind from draining. Using kettles, that will stay deep enough for the fish to breathe comfortably, will prevent stress and damage from any of them getting caught in the shallows.
Exposing the Liner
Draining the pond may keep it from freezing over the winter or make harvesting easier, but it exposes the liner more than ever to damaging UV rays. Thin layers of water ,that gather on the liner after draining, freeze harder than if the whole pond was filled and can cause cracks to form. If you must drain the pond completely and clean out all the muck for the winter, try using a cover over the liner to protect it. Replacing a cover once every few years due to wear and tear is still less expensive than trying to reline to the entire pond more often than what’s necessary.
Cleaning Up Sludge
Draining the pond at the end of a cycle or season does make it easy to remove sludge and muck. While this is necessary eventually, don’t assume you must remove it every year. It’s better to leave some organic material at the bottom of a pond to keep the bacterial colonies intact that are responsible for breaking down fish waste. If you completely scrub and sterilize the pond between uses when there’s no specific disease risk, you’ll find that water quality is less stable and takes more time to reach a balanced point. Temper your need to clean out waste, with the idea of leaving some sludge behind for bacterial reasons, to get just the right amount of muck removal each off season.
Dealing with Pumping
One big reason not to drain your fishponds between seasons or cycles is to avoid the hassles of pumping. You’ll have to haul heavy duty pumps and hoses out to each pond, find somewhere to discharge the water without causing flooding or runoff issues, and then deal with what’s left in the pond. If it’s possible to leave the ponds at least partially full between uses, consider skipping draining altogether and rely on seines and other tools to harvest the fish.
Replacing the Water
Water replacement cost is another major reason to avoid a full drain of each pond. Even if the replacement water can be obtained at no specific cost per gallon, there’s still the cost of pumping it, treating it, filtering it, and even warming it to the correct temperature. Saving last year’s pond water, by draining the pond as little as possible at the end of a cycle, can save you a significant amount on water costs over the course of each year.
Hatchery ponds were traditionally drained often as a water quality control measure and to combat the fact that earthen ponds naturally lose and gain water. Lining a pond is recommended if you don’t plan to drain it regularly. Find the liners you need for both types of hatchery ponds at BTL Liners.
