HIGH-RATE CHANNEL CATFISH FINGERLING PRODUCTION IN THE PARTITIONED AQUACULTURE SYSTEM

The objective of this 4-year research project was to evaluate the performance of channel catfish (Ictalurus punctatus) fingerling production in the Partitioned Aquaculture System (PAS). The goal was to demonstrate production of 80-gram minimum sized fingerlings in a single growing season, allowing for 100% market-size fish production after one additional season in the grow-out PAS. A series of 2-inch airlift pumps fed by a single 3-hp low-head blower was found to be capable of supplying sufficient water flow-rate (in 2005, 2006, and 2007) of gpm per container to 9 cohorts. A series of 0.75-hp axial flow pumps (in 2005, 2006, and 2007) were required for each 1/4th inch net-pens providing an average flow of gpm/cohort. In 2008 it was found that sufficient water flow to both fry/fingering containers and cells could be maintained using the paddlewheel generated flow (passive flow) yielding an average flow rate of gpm/cell but produced as lower cell cross-sectional flow- rate of 0.34 ft/sec as compared to 1.82 ft/sec. Passive flow reduced overall power consumption by 58% to 7,409 kw-hr/acre-yr. Under passive flow conditions a flow deflector of 12\u27 by 12\u27 positioned at an angle of 45 degrees in the water path was found to be necessary to generate a flow vortex within the container to provide feed retention within the containers and prevent fry disorientation. Over the four year culture period, average morning water temperatures ranged from 25.6-27.7 ¡C. Average morning dissolved oxygen concentrations ranged from 4.3-5.3 mg/L with an average dissolved oxygen drop across the fingering containers ranging from 0.20-0.84 mg/L. Average total ammonia-N concentration ranged from 0.6-1.2 mg/L. Over the four year period, optimal stocking into fry and fingerling containers was determined as: initial stocking (3-5 days after hatching) into 1/16th inch mesh container at average weight of g/fry for a growth period of days, after which the fingerlings were moved into 1/8th inch mesh containers at average weight of g/fish for a growth period of days, followed by transfer to 1/4th inch net-pens at average weight of g/fish where the fingerlings remained for the remainder of the growing season. Optimal feed application rates required to grow catfish from a 0.05 g fry to a 115 g fingerling was observed to be (from combined observations during the 2005 and 2006 seasons) with %Fd = percent of catfish wet body weight to be fed per day (as dry feed), and AvWt = average individual fingerling wet weight. The optimum catfish-fry stocking rate was determined (in 2005 and 2006) to be 5,000 fry per 162 ft3 cell. In 2005, stocking at a rate of 10,000 fry/162 ft3 was observed to reduce fingerling growth by 47%. In 2006, stocking at a rate of 3,000 fry/162 ft3 was observed to reduce final cohort density by 26% with no increase in fingerling growth. Maximum total system carrying capacity of 4,695 lb/acre was observed during 2007, with fry stocked at 5,000 fry/162 ft3 cell, and fed at previously determined optimal feeding rate, yielding an average catfish fingerling size of 113.9 g/fish, with overall fry survival rate of 91%. Market-size catfish yields from conventional pond fingerling production combined with conventional pond grow-out was projected at an overall fish yield of 3,279 lb/acre of 1.63 lb fish, as opposed to 10,137 lb/acre of fish projected from conventional fingerling production coupled to PAS fish grow-out, and 11,280 lb/acre of market-sized fish yield projected from PAS fingerling production coupled to PAS grow-out. Additional advantages offered by PAS fingerlings grow-out include the potential to stage more harvests throughout the growing season due to a larger stocked fingerling, which would increase yearly harvest for a given carrying capacity; the elimination of the need to over-winter fish in the grow-out PAS; high survival rate; ease of disease treatment; ease of harvest; and no discharge into the environment, with the disadvantages including higher energy inputs and more intensive management of algal culture