Under good growth conditions, 1-gram fish are cultured in nursery ponds to 1 to 2 ounces (20 to 40 grams) in 5 to 8 weeks and then restocked into growout ponds. In monosex growout ponds under good temperature regimes, males generally reach a weight of ½ pound (200 + grams) in 3 to 4 months, 1 pound (400 + grams) in 5 to 6 months, and 1.5 pounds (700 grams) in 8 to 9 months. To produce 1-pound (400- to 500-gram) fish, common practice is to stock 6,000 to 8,000 males per acre in static water ponds with aeration or 20,000 to 28,000 males per acre where 20 percent daily water exchange is economically practical.
After 6 months of feeding with good quality feeds, such ponds can produce 5,000 to 7,000 pounds per acre and 18,000 to 20,000 pounds per acre, respectively. If growout cycles are longer than 5 to 6 months (in an attempt to produce a more marketable size fillet) there is a risk that offspring from reproduction of the few females that were unintentionally included in the ”all-male” culture will have time to reach sexual maturity and overpopulate the pond.
Consequently, a farmer who wishes to produce fish yielding 5-ounce fillets (a 2-pound fish) is often forced to add a second growout phase so females and fingerlings can be eliminated from the growout ponds, or to stock a predaceous fish with the males. Dressout percentage on tilapia is relatively low compared to species such as trout and catfish. Tilapia generally has a dressout of 51 to 53 percent of live weight for whole-dressed fish (head-off) and 32 to 35 percent for fillets (pin bones along the lateral line removed).
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Health Articles
An Open Letter regarding recent reports that low-fat fish like tilapia are unhealthy. (July 16, 2008)
Eating fish, especially oily fish, at least twice per week is recommended for heart disease prevention. Fish is low in total and saturated fats, high in protein and essential trace minerals, and contains long-chain omega-3 fatty acids (EPA and DHA). Oily fish rich in these healthy omega-3s include salmon, trout, albacore tuna, sardines, anchovies, mackerel and herring. Our omega-3 needs can also be met by eating less-oily (lower-fat) fish more often.
Tilapia and catfish are examples of lower-fat fish that have fewer omega-3s than the oily fish listed above, but still provide more of these heart-healthy nutrients than hamburger, steak, chicken, pork or turkey. Actually, a 3 ounce serving of these fish provides over 100 mg of the long chain omega-3 fatty acids EPA and DHA. Considering that this is about the current daily intake of these fatty acids in the US, even these fish should be considered better choices than most other meat alternatives. Since they are also relatively low in total and saturated fats and high in protein, they clearly can be part of a healthy diet.
US Department of Agriculture statistics indicate that farmed tilapia and catfish contain somewhat more omega-6 fatty acids than omega-3. Most health experts (including organizations such as the American Heart Association and the American Dietetic Association) agree that omega-6 fatty acids are, like omega-3s, heart-healthy nutrients which should be a part of everyone's diet. Omega-6 fatty acids are found primarily in vegetable oils (corn, soybean, safflower, etc) but also in salad dressings, nuts, whole-wheat bread, and chicken.
Replacing tilapia or catfish with "bacon, hamburgers or doughnuts" is absolutely not recommended.
Signed:
William S. Harris, PhD, FAHA
Sr. Scientist and Director
Metabolism and Nutrition Research Center
Sanford Research/USD
Sioux Falls, SD
(605) 328-1304
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