Coral propagation for aquarium specimens.

Abstract

Coral reefs are being destroyed and degraded by natural and anthropogenic processes. Live corals are becoming increasingly popular as marine aquarium specimens, in both the commercial and private sectors, leading to the degradation of coral reefs. This often has serious economic implications for the fishing, aquarium and tourist industries. It is clear that there is a need for the management and protection of these fragile ecosystems. The artificial propagation of coral is desirable as it will alleviate the demand for wild coral specimens, and will also provide a stock for the rehabilitation of damaged reefs. Although corals are being propagated worldwide by hobbyists, reports on their work are mainly anecdotal and there is little in the scientific literature on the specific requirements for optimal growth rates and survival in suitable coral species. This study thus focused on developing techniques to propagate a range of appropriate coral species and to promote their optimal growth. The results revealed that different morphological groups of scleractinian corals require specialised techniques of fragmentation and attachment to ensure survival. The corals were broken using a hammer and chisel. Attachment techniques varied from the use of superglue (which is widely used in the United States), to thermoplastic glue. The mean mortality using superglue was 73% (n=120, ±0.167), using epoxy, 62% (n=120, ±0.127) and with thermoplastic glue it was 11% (n=120, ±0.108) Superglue was extremely difficult to work with and proved ineffective, especially when attempting to glue uneven surfaces. Certain species did not survive using this adhesive due to exposure of the coral to air. The most effective method of rapid attachment was the use of thermoplastic glue that set rapidly underwater. The use of electrolysis to promote the attachment of coral nubbins was tested as an alternative to the various adhesives. This method increased the survival of the nubbins and eliminated exposure to air. It has proven suitable for both coral propagation and in situ reef rehabilitation. Growth experiments revealed that the manipulation of current flow, light and the addition of different feeds had different effects on the growth rates of selected candidate species. A suite of optima was thus developed for each species. The majority of species grew best in a bi-directional current flow, with yeast as feed, under actinic blue light. An experiment that combined the optimal current flow, feed and light conditions, revealed that the majority of species grew best under mixed light with yeast as feed. The trade in corals is sensitive in terms of their handling, transportation and CITES (Convention on International Trade in Endangered Species) status. Having established the viability of their propagation, consideration was given to appropriate regulatory and marketing procedures to accommodate this sensitivity of the cultivated material.