For clearer copies of the data sheets, production run, and graphs, see the copy on reserve at the library. It is also available electronically from the Library Reserves web site.
Profitably Growing Lithuanian Carp
SC 120, Section 4
November 11, 2002
I knew from the introductory material that my fish, the Lithuanian carp, was adapted to living in slow muddy streams, this would also mean that it could tolerate low oxygen, since warm water holds less oxygen than cold water and slow streams get very little aeration. The introduction said that it could live on low-protein food, and tolerate high ammonia concentrations. This information helped me to set my initial values and concentrate on particular tests.
First I used the tank to see the minimum amount of oxygen my fish could tolerate (Fig. 1). Aeration is expensive, so I wanted to set the emergency aeration pumps to go on only when necessary. I found that the fish died at 4 mg of oxygen per liter of water. At 5 mg/l they all lived, but the cost was $0.95 per kilogram of fish. At 4.5 mg/l, the cost was $0.86 per kilogram. I tried values slightly higher or lower, but this was still the best. I repeated the experiment with this value and got a slightly higher cost $0.88, but it was still the best.
Next I used the tanks to find the best percent protein to use in my feed (Fig. 2). I wanted enough to keep the fish healthy, but not too much, because thatís expensive and extra protein can poison the water. I started at 30% because the catfish did best with that. The cost was $0.86/kg fish. I tried a higher protein level (40%), but that cost a lot more and the FCR (feed conversion ratio) was higher, so I was not only paying for more expensive feed, it was taking more feed to produce a kg of fish. I tried 15%, and got a cost of $0.72/kg. I tried higher and lower values, but this was the best. The closest values were 13%, which cost $0.84 but had a high FCR, and 20%, which cost $0.73. At 20%, the FCR was lower than at 15%, and maybe I should have paid more attention to that.
I used the tank experiment to see whether my fish could tolerate the highest temperatures it might encounter in the pond (Fig. 3). I didnít know how hot that might be, but 40 oC was the maximum the program allowed. I tried 30 oC, and the fish did fine. The cost per kilogram was $ 0.72. At 32 oC and above, the fish died. Lowering the temperature to 25 oC reduced the cost to $0.49 per kg of fish, and the fish got bigger, but using groundwater drastically reduces the size of pond you can use, so I decided it was probably not worth using groundwater to cool the ponds.
I finally used the ponds to find the optimal stocking density (Fig. 4). I Used 4.5 mg/l O2 for my emergency aeration level, 15% for my feed protein (variable at 2% of body mass), no ground water or antibiotics, and harvested at the end of the season. I tried a stocking density of 5,000 fish/ha3. I lost money. The pathologistís report said many had starved, so I increased the protein to 20% and tried again. I made $23,271. I increased the fish to 6,000 and made over twice as much, so I tried 10,000 fish, but I lost money. At 8,000 fish, I made $213,436. This was a big improvement. I tried slightly higher and lower, but this was the best. I repeated it at 8,000 and got a bit less profit, but it was still high.
The Lithuanian carp can be cultured profitably in South Carolina ponds if the aeration level is kept at 4.5 mg oxygen/liter. Stocking density in the ponds should be 8,000 fish/cubic hectare. Feed should be about 20% protein. With these values, I got an average profit of $185,044 in five runs, with a range of $164,822 to $203,861.
If I were to run the experiment again, I would try different values for the protein in the feed. When I moved to the ponds, the lowest protein value didnít work and I just picked a higher one rather than trying to find the optimal one.
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