Journal of Aquaculture Research & Development

Abstract

Effect of Diet and Stocking Densities on Life History Traits of Clea helena (Philippi 1847) Reared in Captivity

Ana Rita Coelho, Maria Teresa Dinis and Joaquim Reis

The freshwater gastropod Clea helena has recently been targeted by the freshwater ornamental industry due to its predation abilities on other snail species. This work describes for the first time some life history traits of this species, including reproduction, growth and development under laboratory conditions. Additionally, appropriate stocking densities were studied in order to assess the production viability of healthy snails in close-circuits systems. The species is dioecious and breeds under laboratory conditions but fertility rates presented were low. Hatching occur 52 ± 6 days after oviposition, at 25.0°C. Development is direct and juveniles hatch at shell length SL=3.1 ± 0.3mm (n=20) and resemble the adults in shell shape and color. Growth rates during a maximum period of 60 days were compared between snails fed on three different diets and results showed they were influenced by the different diets treatments (P<0.05). Growth performance experiments at three stocking densities (5, 10, 20 snails/L) with three replicates per treatment were also performed. During the first month, individuals stocked at 5 snails/L had significantly faster growth rates than those stocked at 20 snails/L. No significant growth responses were found during the second month among all densities and overall growth rates for this experiment also revealed no density dependent growth responses.