Abstract

As natural populations of queen conch are depleted, aquaculture of conch may prove necessary for restocking efforts or for supplementing the wild catch. In aquaculture systems rapid growth and high culture density of juveniles are economic necessities. We examined growth of juvenile queen conch for 19 weeks at two densities (SO and 150 conch/m2) and in three grow-out systems: rectangular fiberglass tanks, cages within tanks, and upwell chambers. We also tested the effect of size hetemgeniety on growth conch held in cages and upwells. Conch growth in homogeneous (mean size=61.8, range 60.6-63.2 mm shell length, SL) size treatments, held at 50 conch/m*, was compared to growth in high and low density treatments (mean size-61.5, range=51.7-69 mm SL). Initial mean size of conch was 61.5 mm shell length. Up to 15 conch/treatment were tagged for weekly, repeated measurement. Greatest growth occurred in homogeneous-size caged treatments (14.8-17.6 mm total growth); tank treatments had the least growth (8.5-12.6 mm total growth). Conch in high density tank treatments had the lowest growth. No significant difference in growth among any upwell treatments was found (13.5-15.3 mm total growth). Density alone had little effect on growth in cages. Placement of cages within tanks relative to water inflow may have an equal or greater effect on growth than density. Although upwell treatments exhibited generally greater growth than other treatments, the cost and complexity of upwells systems may be pmhibitive. The slow growth in tank treatments may have been due to excessive handling associated with tank cleaning. Cage treatments may reduce stress or shell damage due to handling. Cost of cage systems may be offset by higher growth rates of juvenile conch, particularly if conch are separated into size classes.

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