I am taking a look at fish other than tilapia for a proposal. Koi has got enough info for me, but as there are many people here with practical experience with catfish, I'd like to find out what recommended AP ratios of catfish stocking densities (fish to cube of water) could be. In South African commercial aquaculture operations, our local catfish (Clarias sp.) can be pushed to phenominal densities but I need to try to figure out what feasible densities for aquaponics would be. Anyone here with knowledge of stocking densities for large systems using catfish?
Have you found out the answer to your question? Im doing my university dissertation on clarias in aquaponics systems. Having trouble coming up with mass balance equations for feed rate and nitrogenous build up which will ultimately determine my max stocking density! Want to pre-calculate it before I start. Any ideas?
I don't know how much Kobus is getting onto the site lately as I think his new job may be keeping him rather busy. You might try friending him to see if you can send him a private message that he may get a regular e-mail notice about.
Thanks! Will try that.
We raise catfish here in our multitorphic pond. We calculate at one cubic length of adult fish. ie an adult catfish two foot long needs at least two cubic feet (provided oxygen levels can support all the fish including catfish). Catfish is one species, like talapia and their human counterpart (Asian people) can handle close quarter living so suitable for raft type AP or for even more production, multi tier production(verticle stacking). You may want to give them more space to encourage faster growth.
Thanks Carey! Good effort. Will take that into account!
This may not help you with AP calculations, but for the aquaculture side, we ran a stock densite at 50,000 for ponds sized around 1000 m3. We ran 10 ponds at this level. The story is a long and involved one, but essentially we survived a growth cycle that lasted more than 180 days at that kind of density, with less than 7% total mortality loss. .
That stockage figure works out to 50,000 fish around 240,000 gallons, or 1 fish per 5 gallons. At the harvest, each pond produces about 12700 Kg of fish (averaging 10 ponds together)... Water volumes carried at that time were about 480,000 per pond, so the fish mass density averaged out to 0.close out density at harvest averaged 0.264 Kg / gallon or about 0.58 pounds / gallon, or near to 3 pounds of fish per 5 gallon volume.
It is difficult come up with an " average fish" in a uniform pond that started with a single stocked size. Despite reasonable feeding practices, a full size distribution results. Fish ranged from large fish 1+ Kg each in size to smaller sizes that averaged 5 to 6 per Kg. It has to do with food competiion and feeding agression patterns.
The fish were seperatly sampled across ponds and tested for flavor / quality with good observations across all ponds. In general the fish were considered to be (even at that density) with fairly low incidence of any observed conditions during the harvesting process. But to achieve those conditions and very low mortality. Pond water and conditions were monitored often, and water exchanges (10% freshening as needed) took place as needed (by observation) during the 2nd half of the cycle.
Based on seeing how well the fish responded - would specuate that with the generally higher water quality that should go with an AP system - Cats could probably be stocked at 1/2 the mentioned density, with the idea that the fish will be kept untill all are approaching the 2 pound size.
This is just a suggestion based on observing the how well the cats survived. The ponds were run with a total salt concentration of around 200 PPM or about 0.2 Tpm. That salt level was above the minimum levels needed for good Catfish health, but it was kept near this level as a preventive measure, because nitrate levels were elevated without a lot of remediation efforts. The salt prevents brown blood disease, by allowing a nitrogen build in the fish. Brown blood disease is a significant risk factor for high density Cat cultivation.
Without haveing AP working with these ponds, a significant amount of the nitrogen was consummed in the proliferation of green water culturel items (algea, plankton, and invertibrates). Water exchanges were performed when nutrient loading were sufficient to cause the green blooms to show signs of collapsing. It can be observed from both pond culture, and additional by trace odors that develope to reveal anaerobic processes to start to develop. The use of spray rings in the ponds, increased that abiitity to pick up scents from pond culture, and was a factor (along with perceptible dips in Daytime bright sun O2 level readings) to detect decline in photosynthetic oxygen creation from the green water components. These observations allowed ranking which ponds needed water exchanges to be done in sequence, since pumping was limited to exchanging water in only one pond on any given day.
I hope that this helps your concerns and considerations
In the end
Hope that this helps.
When I'm growing out Channel Catfish in Aquaponics, I tend to stock about 1 fish per 10 gallons of fish tank (provided I have ample filtration for that amount of fish.) Channel catfish can get big and the smallest tank I would personally try to grow them in anymore is 300 gallons and I prefer bigger, deeper tanks for them The 700 gallon 4' deep tank actually worked really well for them and Now I am growing them in 1000 gallon tanks that probably have 900 gallons of water in them. 75-90 growing channel catfish in that size tank is reasonable for aquaponics. I tend to grow them big so as they get to small eating size, we will harvest some to make more room for the others to grow bigger. In my climate they can reach 10 lb if I keep them for two years.
In Aquaponics where algae is generally kept to a minimum, the issues of muddy or off tastes seem not to be an issue so far in my experience.
In closed systems the African catfish allows the density around 450 kg/m3.
I had the experience of growing 9 catfish of 2 inches to> 16 inches (weight 0.7kg) - 6 months. The amount of water was 60 liters.