Significance of Habitat and Stock Re-Testing for Enhancement of Natural Fisheries: Experimental Analyses with Queen Conch Strombus gigas

The queen conch Strombus gigas is a large, commercially important gastropod mollusc native to the Caribbean region that has become severely depleted because of overfishing and habitat destruction. Over the last 10 yr attempts have been made to rehabilitate conch stocks through releases of hatchery-reared stocks, but successes have been few. Some of the reasons for high mortality in hatchery-reared conch are elucidated by recent experiments conducted at Lee Stocking Island in the central Bahamas.
Field experiments with juvenile queen conch indicate that sites with similar depths, sediments, and macrophyte cover do not provide equivalent food and shelter for conch. Transplants of conch were successful only in sites known to be historically significant as nursery grounds. While small-scale transplants can be used to screen potential outplant sites, only comprehensive understanding of the habitat requirements, behavior, feeding ecology, and predator-prey relationships will lead to long-term enhancement of fishery stocks. Differences in morphology, behavior, and habitat utilization between wild and hatchery-reared stocks also had significant effects on the survivorship and growth of outplanted stock. Therefore, hatcheries must develop culture methods that do not reduce the natural fitness of wild stock. Successful enhancement of natural fisheries through outplanting of hatchery-reared stocks depends upon: 1) development of hatchery animals sufficiently well adapted to survive in the field; and 2) release of the stock in suitable habitats at the optimal time. Close linkage between laboratory and field research, and hatchery operators will he necessary for the ultimate success of stock enhancement efforts.