SUMMARY OF A FOUR-YEAR PROJECT EVALUATING AN IN-POND RACEWAY SYSTEM
In-pond raceways systems (IPRS) can have higher fish yields than conventionally managed catfish ponds (8,000 kg/ha) with IPRS units having annual fish production greater than 15,000 kg/ha . A four-year project at Auburn University was initiated with the objective of evaluating the performance and economic efficiency of fish produced in IPRS units . For this four-year trial, a f loating IPRS unit was placed into each of four 0.4 ha ponds . In year 1, Ponds B1 and B2 had 64 m3 (4.9 m x 10.7 m x 1.2 m deep) IPRS units place into them, and ponds B3 and B4 had 45 m 3 (3.1 m x 12.2 m x 1.22 m) units. Each pond had a total of 3 HP of aeration: a 1.5 HP blower for the IPRS unit, plus a 1.5 HP blower for the in-pond water mover-destratification unit. First-year production of h ybrid catfish (channel catfish, Ictalurus punctatus , ♀ x blue catfish, I. furcatus, ♂) used 41 g fingerlings stocked in March 2016 and were fed 35 % and 32% CP. In year 2, t he same IPRS units were used, and to improve the system an additional 1.0 HP aerator was added to each pond and Channel c atfish (Ictalurus punctatus ) fingerlings (44 g) were stocked into IPRS units in April 2017 and fed a 35 % and 32% CP. In year three, a n additional "stocker generator", a smaller f loating IPRS unit 14 m3 (1.8 m x 5.8 m x 1.30 m) was placed into each of four 0.4 ha ponds next to the existing "grow-out" units . Also, an additional 1.0 HP aerator was added to each pond bringing the total to 5.0 HP per pond . Hybrid catfish , mean weight 31 g, were stocked into IPRS units in April 2018 and in the "stocker generator ", 29 g hybrid fingerlings were stocked in July 2018 and fed a 35% and 32% CP. In year four, the l ast year of study (current year) a n additional floating tilapia cage ( 36 m3 , 4.26 m x 7.16 m x 1.20 m) was placed into 2 of t he 4 ponds (B2 and B4) with no aeration. There was a total of 5 HP of aeration in each pond . Hybrid c atfish fingerlings for the growout units (B1 and B4) came from the third-year's project " stocker generator" and weighted 322 g . Ponds B2 and B 3 were stocked with 28 g fingerlings. The stocker generator unit was stocked on June 2019 with 28 g fingerlings and the tilapia (120 g) were stocked in July 2019. Catfish were fed a 35% CP feed and tilapia were not fed and allowed to grow through ingestion of phytoplankton only .
Water quality parameters have been in acceptable ranges for all trials. The total production from 2016 to 2018 reached the amount of kg/ha produced in conventional catfish production systems. Results from years 1-3 and partial 4th year results are summarized in Table 1. It is expected that 2019 production will be greater than prior years . Full four -year trial results and enterprise budgets will be presented at the WAS meeting.
