Size-specific predation of juvenile queen conch Strombus gigas: implications for stock enhancement

Abstract

Mariculture has long been considered a mechanism for restoring populations of queen conch, Strombus gigas Linné, which have been seriously over-fished throughout the Caribbean. The extremely high mortality of small juveniles and differences in survivorship between hatchery and wild stocks are severe obstacles that must be overcome. We conducted a tethering experiment to determine optimal release size and to examine differential predation among ten size classes of juvenile conch from 20 to 130 mm in shell length. Smaller animals (20–75 mm) were hatchery-reared, and larger animals (75–130 mm) were from the wild. Mean mortality of 75 mm hatchery conch was significantly higher than that of 75 mm wild conch. After 54 days all 20–40 mm conch and 10% or fewer of the 90–130 mm conch were killed. Based on our survivorship curve, we recommend a minimum release size of 75–90 mm. Actual release size, however, will inevitably represent a compromise between the high survivorship of large animals and the low cost of producing small ones.