In the first reported event of its kind, researchers from Harbor Branch Oceanographic Institution's Aquaculture Division have determined that female queen conch (Strombus gigas) can lay egg masses in captivity. The spontaneous spawning event was recently documented in rearing tanks that communally house queen conch along with three other conch species (Florida fighting conch Strombus alatus, milk conch S. costatus, and hawkwing conch S. raninus ). These animals are part of a recently initiated HBOI conch research project aimed at designing methods leading to commercial cultivation of alternative species to the queen conch, a popular fisheries species that has been the subject of mariculture efforts since wild populations began to decline in the 1970s.

For several years, Dr. Megan Davis - Director of Harbor Branch Aquaculture's ACTED aquaculture education program and head of the Harbor Branch conch project group, has conducted research on improving the culture techniques of conch in Florida and the Caribbean. This is the first time that Dr. Davis has not had to resort to collecting queen conch eggs from the wild. Captive spawning of other conch species occurs readily under appropriate rearing conditions. Although they attain a smaller adult size than queen conch, captive spawning success in other conch species made it likely that culture of one or more of these alternate species would eventually fill some market niches initially developed for queen conch. But the knowledge that queen conch also now appear capable of reproducing under culture conditions may change that.

"This event is exciting," notes Dr. Davis, "because it strongly suggests that we will be able to close the cultured life cycle of the queen conch, and end our reliance on natural sources of eggs."

Successfully growing animals "from egg to entree" - and through successive generations - is the goal of closed-cycle aquaculture. And it is a particularly important research plateau to reach in the case of the queen conch, because eggs and larvae spawned in one geographical location very often are the animals that ultimately recruit (settle) to new locations, sometimes a hundred or more miles away. It is known that overfishing of adult conch in a location that serves as a larval source pool may have negative implications for recruitment success within larger and/or more distant settlement locations.

To a much smaller extent, conch hatchery operations can contribute to the same problem. If a hatchery must always resort to wild egg collection then they are not necessarily just robbing the cradle in terms of local recruitment success - they may be negatively affecting recruitment success over a much larger geographical region as well. Closing the queen conch culture cycle will guarantee that success of the aquaculture operation does not occur at the expense of already impoverished wild stocks.

Dr. Davis and research assistant Jerry Corsaut believe the fact that the successfully spawning queen conch were housed communally with actively mating individuals of other conch species may well have been instrumental in triggering the queen conch to mate and spawn. The species are physically isolated from one another by means of partitions, but waterborne pheromones or other chemical spawning cues may have been transmitted by one conch species and picked up by neighboring queen conch.

Most importantly, the laying of the egg mass was not a one-time event. The same female queen conch has produced four separate masses so far, on February 12, February 21, March 4, and March 11. As of the time of this writing (March 15), approximately 2,000 animals emerging from the first egg mass have been successfully brought through an 18-day larval rearing period and have metamorphosed to benthic post larvae. Animals from the second egg mass are currently 6-lobed planktonic larvae that have spent 16 days in the water column, while those from the third clutch hatched out earlier this week. Larval queen conch from the most recent egg mass are due to hatch out within a couple of days.

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Cultured Conch Lifecycle - Quicktime format - (exerpted from The Conch's Life Story)