Investigating fragment size for culturing reef-building corals ( Porites lobata and P. compressa) in ex situ nurseries

• Published in: Aquaculture 2006-11, Vol.261 (1), p.89-97
• Main Authors: Forsman, Zac H., Rinkevich, Baruch, Hunter, Cynthia L.
• Format: Article
• Language: English
• Subjects: Animal aquaculture; Animal productions; Anthozoa; Aquaculture; Biological and medical sciences; Cnidaria. Ctenaria; Coral aquaculture; coral culture; Coral growth rates; Coral reefs; corals; Echinoidea; Ex situ coral nursery; Fundamental and applied biological sciences. Psychology; General aspects; Invertebrates; mariculture; Mortality; Phestilla sibogae; Physical growth; Porites; Porites compressa; Porites lobata; Size-specific mortality; Tripneustes gratilla
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2006.06.040

Culturing small propagules of coral has the potential for high yield with low environmental impact, provided that mortality is low. This study investigated the size-specific mortality and growth of minute fragments (as small as 5 polyps) of two of the most abundant reef-building corals in Hawaii ( Porites lobata and P. compressa). Two ex situ nursery systems differing in cost, design complexity, and labor intensity were compared. The first nursery experiment lasted for four months in a large tank with high water motion/surge and extensive manual cleaning to remove competitive algae. The corals were then transferred to a simple low-flow tank containing sea urchins ( Tripneustes gratilla) and reduced cleaning, where they were grown for six more months (Nursery II). ‘Nursery I’ resulted in 92% of P. lobata and 73% of P. compressa fragments surviving and nearly doubling in area, in spite of a brief infestation by a nudibranch ( Phestilla sibogae) that primarily fed on larger P. compressa fragments. There was a significant positive relationship between fragment size and growth rate, and survivorship was significantly different between donor colonies (genets), but there was no evidence of size-specific mortality. ‘Nursery II’ on the other hand had clear size-specific mortality and higher urchin damage for smaller fragments, resulting in moderate survivorship (78% for P. lobata and 76% for P. compressa), and only a slight increase in the total area covered by coral tissue. Fragments larger than 3 cm 2 were undamaged and had the highest survival and growth rates. This study illustrates how size-specific mortality can be reduced by ex situ nursery conditions.