Growth of Florida fighting conch, Strombus alatus, in recirculating systems.

Abstract

With the increased interest in water conservation and the need to reduce the discharge of effluent from aquaculture production systems, there has been a shift from open, flow-through systems to recirculating aquaculture production systems. In 2001, Harbor Branch Oceanographic Institution developed the first recirculating conch aquaculture program. Two important aspects of conch aquaculture are detennining the stocking density and water quality parameters in growout systems that yield the fastest growth rate and the highest survival. . An experiment was conducted from March 11 - June 3, 2003 at two Florida sites, Harbor Branch Oceanographic Institution and Mote Marine Laboratory, to compare survival and growth of juvenile conch in a recirculating growout system. The recirculating system consisted of raceways troughs with an elevated sand substrate. The three replicate raceway troughs at each site were stocked with juvenile (16.9 ± 1.9 shell length) Florida fighting conch, Strombus alatus at 75 conchlm2 (l09 and 140 conch per replicate at Harbor Branch and Mote, respectively). In 12 weeks, the conch grew 18.8 mm or 0.22 mmI day at Harbor Branch and 22.5 mm or 0.27 mmJday at Mote. There was a significantly faster growth rate at Mote, which appeared to be due to a lower stocking density throughout the experiment. There was an 83 % and 70 % overall survival rate at Harbor Branch and 1tlote, respectively. Temperature, salinity, and pH averaged 26.7°C, 31.6 %0, and 7.9, respectively at Harbor Branch, and 26.4°C, 34.9 %0, and 8.2, at Mote. The feed conversion ratio was 1.3 at Harbor Branch and 2.2 at Mote. The recirculating aquaculture systems utilized at each site had optimal stocking densities and water quality for growing juvenile conch.