Author
 |
Tucker, Craig |
|
Brown, Travis |
|
Submitted to: Aquaculture America Conference
Publication Type: Abstract Only Publication Acceptance Date: 12/10/2014 Publication Date: 2/20/2015 Citation: Tucker, C.S., Brown, T.W. 2015. Design and fish culture considerations for catfish farming in split ponds. Aquaculture America Conference. P.477. Interpretive Summary: Technical Abstract: Split ponds are simple, pond-based aquaculture systems constructed by dividing an existing catfish pond into two unequal basins with an earthen levee. Fish are confined in the smaller basin (usually about 15-20% of total water area) while the larger basin serves as a waste-treatment lagoon. A high-volume pump circulates water between the lagoon and fish-holding basin during daylight and aerators maintain adequate dissolved oxygen in the fish-holding basin at night. Split ponds are relatively easy to manage and allow the genetic potential of fish to be expressed by maintaining favorable environmental conditions for growth. The original split pond design was based on overcoming limitations associated with dissolved oxygen availability. Daytime pumping rate and nighttime aeration rate were established by oxygen mass-balance calculations. Ultimate production limits are governed by climate (growing season length) and the finite capacity of the pond ecosystem to process and remove fish metabolic wastes. Theoretical considerations and field results set the production limit at about 20,000 pounds/acre per year although realized production is affected by the type of fish raised, pond size, and system design (especially daytime pumping rate). Only hybrid catfish Ictalurus punctatus x I. furcatus should be used in split ponds. Channel catfish survival and growth is inferior in split ponds and the high cost of system construction argues for using only the best-performing fish. Practical experience indicates that the fish-holding basin should not be larger than approximately 2 acres. Oxygen management in larger basins is difficult and fish biomass may become so great that problems are encountered with harvest and marketing. Accordingly, ponds larger than 8 to 10 acres should not be used as starting points for construction. Aeration requirements are easy to calculate from target fish biomass and aerator oxygen transfer rates, but optimum daytime pumping rate has been more difficult to quantify. Pumping rate in the original design was approximately 1,200 gallons per minute (gpm) per 10,000 pounds of final fish biomass. Pumping rates in most commercial systems are less than 700 gpm per 10,000 pounds of fish. Low pumping rates cause chronically low daytime dissolved oxygen concentration near the end of the cropping cycle, which reduces fish growth rate. Equipment considerations for use in split ponds should include dissolved oxygen monitoring systems to control pump and aerator operation, fish barrier screening material, and inverter-duty electric motor-driven pumps with variable frequency drives. Dissolved oxygen monitoring systems should be reliable with minimal maintenance requirements. Fish barrier screening material should have the greatest open surface area without allowing fish to escape. Variable frequency drives should be NEMA 4 rated and installed in NEMA 4 rated enclosures. |
