Early Rearing of Channel Catfish Fry in Above Ground Raceways and its Impact on Fry Survival in Farm Fingerling Production in Western Alabama
Lisa M. Bailey, J. C. Jones
John R. Morrison
U.S. Department of the Interior
Alabama has a rapidly growing catfish farming industry which has made its largest strides in the wake of the earlier development in Arkansas and Mississi-ppi. Currently, catfish farming in Alabama is experiencing unparalleled growth in terms of increasing water acreage and numbers of farms. It is now the most active sector of agriculture in the state.
The majority of Alabama catfish farms are either partially or completely dependent on an outside source of fingerlings to stock into their production ponds. Relative scarcity of groundwater supply prevents most catfish farmers in Western Alabama from using the time-honored methods employed by the large-scale catfish fingerling producers in the Delta regions of Arkansas and Mississippi. Alabama fingerling ponds must be filled gradually with water from low capacity wells and rainwater runoff from large watersheds. Due to the lengthy filling period and dependence on surface water, predation by insects and wild fish can be devastating until catfish fry attain 1 to 2 inches (2.5 to 5 centimeters) total length in these ponds. We proposed an above ground raceway rearing system with well water supplied by gravity flow or relift pump from a water storage reservoir. Fry were raised from swim-up stage in raceways until 1.25 to 2-inch (3 to 5 centimeters) size before stocking into rearing ponds on a Western Alabama catfish farm and at the Southeastern Fish Cultural Laboratory (SFCL). Survival of fry raised in this manner was compared with that of swim-up fry stocked directly from the hatchery into rearing ponds.
Both raceway systems used well water from a reservoir containing no fish other than a few grass carp (20 fish/acre) to control aquatic vegetation. Water flow was regulated to permit 5 exchanges/hour in each of the raceways used. Inflowing water entered raceways from behind a head wall which eliminated turbulence from the screened compartment which contained the catfish fry. A flow baffle wall at the opposite (rear) end of each raceway enabled exchanged water to be discharged from the bottom. This prevented accumulation of solid waste, most of which exited through the rear standpipe drain. Well water made a single passage through raceways and was then used to fill other fish production ponds. Diffused air aeration was continuously provided to each raceway by a low-pressure air blower and several airstones per tank. Channel catfish fry (swim-up stage) from hatchery rearing troughs were stocked at a density of 1,000 fish/cubic feet into raceways after a few days of feeding on a finely ground 50 percent protein trout starter diet (Purina Mills, St. Louis, Missouri).
Volume or weight estimates were used to determine fry numbers. Feeding was continued in the raceways on the same diet three to four times daily according to observed feeding response. Feed particle size was increased as fish grew. Raceway walls and bottoms were cleaned by scrubbing each morning prior to feeding. Fry were then given a static water treatment of 50 ppm (mg/L) formalin (Paracide F) for 20 minutes to control external bacterial infections.
At both raceway facilities, catfish fry attained 3 to 5 centimeters of total length within a 24- to 27- day period with an average survival of over 95 percent. Of nearly one million fry reared on the commercial catfish farm in two 1,000 gallon raceways during May to July 1995, over 700,000 survived further rearing to 6-inch fingerling size. This surpassed previous survival rates achieved on this farm in several years of operation.
At the Southeastern Fish Cultural Lab., when raceway-reared fry were stocked into ponds for further growth, 86.4 percent survived to 5-inch fingerling size. Other ponds stocked with swim-up fry directly from the hatchery yielded 82.7 percent survival. Although, in this instance, survival of raceway-reared and pond-reared groups was high, overall study results indicate that stocking larger fry can help assure higher, more consistent survival from ponds that typically yield poor survival. Raceway rearing may be a means to improve fingerling production efficiency on catfish farms and reduce the need for purchasing fingerling stocks from distant producers.
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