Channel Catfish for Aquaponics

Channel Catfish, or channel cats, or their scientific name: Ictalurus Punctatus are used in traditional aquaculture throughout the midwest. Catfish are also part of many stocking programs and pay to fish lake programs so there are numerous case studies and research available. This article will focus on how and why to raise and breed the best tasting catfish in aquaponics.

Photo Courtsey of FWS.gov

Appearance of Channel Catfish

Catfish change color depending on their age, and the type of water where they live. Older males are generally darker and no longer have spots. Catfish from muddy water have a yellowish tint, and catfish from clear water have a dark almost blue appearance. Albino catfish are uncommon but not rare. Channel catfish have a rounded anal fin with 24 to 29 rays. They also have a deeper fork in the tail than other types of catfish, but without side by side comparison this is hard to see.

Why Use Channel Catfish for Aquaponics

• Catfish are hardy fish
• Catfish can take extreme temperatures
• Catfish are easy to feed being omnivorous, and with commercial feed readily available
• Catfish co-exist well with bluegill and sunfish
• Catfish is a familiar fish that many people are happy to eat
• In aquaculture they can take extremely high stocking density

Disadvantages to Catfish

There is only one disadvantage to using catfish in aquaculture and that is their relatively slow growth rates compared to tilapia. However, catfish can live in environments that tilapia cannot, as they are a native fish to many regions of the US and Canada.
Another thing to be careful of when handling catfish are the three spikes they have. The Dorsal fin (on their back), and their two pectoral fins each have a single, large, sharp spike that is actually connected to a venom gland. This venom is not enough to kill a human, but it is painful. Anyway, it hurts to have a huge spike jammed through any part of your body as the fish is thrashing around. A hammer to the back of the head on a hard surface is recommended when processing the fish, and even then, be careful of partially functioning nervous systems up to several hours after they stop moving. Handle catfish carefully. To stun them you can also drop them in a bucket of ice water as the shock will make them immobile enough to handle for processing (in case you don’t like the hammer method, which is admittedly a bit gruesome).

Environment Required for Raising Channel Catfish

Dissolved Oxygen (DO)

Less than 1 ppm is lethal. Between 4 and 5 ppm is ideal. Growth slows below 4ppm. In a dense tank you might need aeration at night because the plants will absorb oxygen from the water and choke the fish. Higher temperatures also do not hold as much Dissolved Oxygen (DO) as colder water, so extra aeration when water temperatures go above 85F won’t hurt. When fish feed, they exert themselves in a frenzy, reducing oxygen too. If you notice your fish gasping at the surface, you have DO problems!

pH

Ideal pH is 7.0 with the range of 6.0 to 9.0 acceptable. Measure pH weekly and adjust slowly, no more than .2 per day. Do not use pet store pH adjusters in aquaponics! Use vinegar and boiled clam shells in a stocking to lower or raise pH.

Temperature

Catfish can live in waters 35F to 95F, but these are not ideal and will cause stress on the fish at these extremes. Ideal temp is about 80F with the range of 65F to 90F pleasant and healthy for the fish. Colder temperatures slow metabolism, growth food consumption and thus nitrate output, so warmer fish will mean more growth for your plants and fish. With that said, catfish are great because in most climates they do not need a green house to survive (though that will be ideal).

Stocking Density

One pound of adult fish per gallon of water is the maximum recommended by the studies referenced. I would strongly suggest that you plan on 3 to 5 gallons of water per fish though to give them more available oxygen and reduce stress. You still need the standard 1sqf of grow-bed per pound of fish too. As a system ages and has a stronger bacteria culture with heavy feeding plants, you can go a little bit beyond the 1lb per 1sqf rule, but for the first year stick with 1lb to 1sqf of grow space.
Here are some examples in typical containers and setups of using catfish for aquaponics:

55 Gallon Barrel

6lbs of fish suggested, using 2 barrel halves as the grow bed (about 6 sqf). The grow bed space is the limiting the factor, not the tank. You will need at least a 75 gph pump at 3 feet head height. Fish growth may be limited because of the size of the container.

275 Gallon IBC

Using 200 gallons for the tank and 75 gallons for the grow-bed by cutting the IBC provides about 12 sqf of grow space. 15 lbs of fish is suggested. If you triple the grow bed space, you can easily hold 40 lbs of fish in the 200 gallon tank because now you’ll have 36 sqf of grow space. You’ll need at least a 250 gph pump at 3 foot head height.

275 Gallon IBC with Sump

Assuming you build out 2 grow beds for a total of 64 sqf, and are using a 275 gallon tank with at least a 200 gallon sump, you should be able to hold 75 to 90 lbs of fish in a mature system. You’ll need a 500 gph pump (at 3 foot head height). Adding a 3rd grow bed would be safer and is recommended (total 96 sqf)

Growth Rates of Channel Catfish in Aquaponics

Most fish take about 2 years to mature to plate size (1.5 lbs), and catfish grow slightly faster in the first few years than as they get older. A channel cat allowed to reach maximum size could get up to 40-50lbs in ideal conditions. Ideal conditions for catfish growth are regular, consistent feeding and temperatures between 50F and 90F, however fastest growth is at 85F. Every 18F away from 85F halves the catfish’s metabolism, thus slowing their growth and eating requirements.
There is a formula for estimating a fishes weight in proportion to their weight, but I will give some typical examples instead:

Most commercial catfish are harvested at 18 months.

Feeding Catfish

Catfish are omnivorous and will eat just about anything that fits into their mouth. However, rancid commercial pellets, or rotten carcasses and certain types of algae will give them a muddy taste. If your water stinks, your catfish meat is going to taste muddy too.
In the winter they won’t eat much or at all, and in the spring and and fall they’ll have a hearty appetite, especially for other fish or crawfish depending on their size. In the warmest parts of summer they tend to eat more algae and moss.
Catfish naturally eat all types of other insects, fish, frogs, clams, crustaceans, birds, and even small mammals and algae. After they reach 18 inches, it is estimated that 75% of their natural diet is other fish. In aquaculture system they are fed a floating 32% protein pellet as they will consume in 20 to 25 minutes. To maximize profits on commercial systems, food is carefully measured, controlled and adjusted once per week. Commercial catfish aquaculture uses the following guidelines, which are a good start for smaller backyard aquaponics system too:

If water temperatures exceed 90F you should prepare ways in advance on how to cool the water and provide additional oxygenation. The two easiest ways to lower temperatures are:

• Freeze jugs of water and float them daily to lower a small tank
• Aerate the water with a fountain to increase evaporation

The bad thing about commercial fish food is what it is made from. Most commercial fish feed are made from non renewable sources, notably sea fish. Some commercial fish feeds are made from sick slaughterhouse animals, unfit for consumption. You may want to grow your own crickets, roaches, worms, meal worms, super worms, and/or black soldier fly larvae. All of these home grown colonies of insects and larvae are excellent food sources with the perfect mix of nutrients, fats and proteins. Most of them grow from very cheap base or from food scraps. Commercial feed is definitely easier but it may not provide the additional macro and micro nutrients that plants need. For example crickets and other shelled insects contain phosphorous naturally. Even if you are not able to feed your fish a natural diet like this, you can easily supplement the commercial feed with these types of home grown feeds to increase the health of your fish, your plants, and ultimately you. You’ll also be doing the environment a favor by not consuming sea fish (an already depleted resource), and by limiting your waste through composting.
Be careful of commercial feed pellets stored longer than 90 days or in high temperatures. The oils will break down causing it to go rancid, and affecting the flavor and nutrient value of your fish.
An interesting fact about catfish is how they sense food. Their entire body is a taste bud, with most receptors concentrated on their whiskers. They can detect minute traces of amino acids and odors in the water and this allows them to identify each other by pheromones. In the wild catfish are often caught with bait that stinks such as: wd-40, ivory soap, chick livers, marshmallows, ‘stink bait’, and live fish.

Breeding Catfish

Catfish can breed when they are about 2 to 5 years old, but usually by age 3. A female spawns once per year and lays an estimated 3,000 to 4,000 eggs per pound. The male will prepare a quiet place in a crevice or under a log out of the currents and fan out all of the debris he can. The female lays eggs and then leaves. The male guards the nest and fans oxygenated water on them until the fry hatch. Males can spawn several times per year if the eggs are removed.
You would need to isolate a breeding pair away from other fish or the male will be too busy guarding the nest to actually fertilize and care for the fry. Catfish will also prefer low turbulence and slow moving current for their spawning. Temperatures are optimal at 80F but they will spawn between 75F and 85F. It’s possible to spawn as low a 65F, but many of the eggs will not hatch.
At 78F eggs spawn in about 8 days. Temperatures up or down by 2F add 1 day to the spawning process. Fry have a yolk sac that nourishes them for the first 5 days, and then they’ll begin eating small insects and other types of food. For the breeder, wingless fruit flies are a good option, or smaller floating commercial pellets. Fry will gulp air to maintain buoyancy.
The male will guard his nest by changing colors momentarily to alert other fish, and by making clicking/grating sounds that reverberate off of his swim bladder. All catfish can detect and recognize individual pheromones, and these are used to alert danger, warnings, etc.
Most of the stocking fish that are sold are about 45 grams and growth rates are based on having these fingerlings available at the beginning of the two growth seasons (Apr to Oct growth or Oct to Sept growth) for financial reasons. In aquaponics for self sufficiency – we need to plan the harvest of the fish to coincide with the cost and ability to feed them.
Don’t forget that you need a special license from your state to transport or sell live fish!

References

The following sites and studies provided bits and pieces of my research, many of them having overlapping information:

• http://www.fishbase.org/summary/Ictalurus-punctatus.html
• http://www.thefishsite.com/articles/118/channel-catfish-life-history-and-biology
• https://srac.tamu.edu/index.cfm/CategoryDetails/whichcategory/3/
• http://www.fda.gov/Food/FoodScienceResearch/RFE/ucm079751.htm
• https://www.tpwd.state.tx.us/regulations/outdoor-annual/fishing/freshwater-fishing/catfish-identification
• http://www.aa-fishing.com/az/arizona-catfish-fishing.html
• http://www.fws.gov/refuges/FishingGuide/species_catfish.html

All information was taken in January of 2014.