The Influence of Artificial Reef Associated Fish Assemblages and Varying Substrates On Coral Recruitment

摘要

This study examined enhancing coral recruitment to artificial substrate by manipulating fish assemblages and the use of coral attractant substrates. One hundred sixty artificial reef modules were organized into 40 four-module replicate configurations (quads) of varying complexity to induce different fish assemblages. The deployment array consisted of the 40 quads, each in a square configuration with three to four-meter sides (approximately 1 m separation between modules) measured from the outside corners. The quads were divided into four fill treatments of differing complexity: Empty, Small, Mixed, and Large. Each quad had four potential coral attractant treatments on settlement plates: CaCO3, iron, coral transplants, and control. Each module in a quad contained a different attractant. Fish counts were conducted quarterly (January, April, July, October) for three years. During the study, fishes comprised of 166 species from 40 families were counted. Twenty-six species accounted for 90% of the fish counted with bluehead wrasse (Thalassoma bifasciatum), juvenile grunts (Haemulon spp.), and slippery dicks (Halichoeres bivitattus) making up over 55% of the fishes counted. Fish abundance and species richness were significantly less on Empty treatment quads than the other three treatments while species richness was less on the Empty and Small treatments than the Mixed and Large. Because of low coral recruitment rates, a single survey was conducted at the end of the study period to record the number and species of coral recruits. A total of 186 coral recruits were counted on a sub-sample of modules. Porites astreoides was the most abundant recruit (47.8%) followed by Agaricia agaricites (13.4%). Coral recruits were categorized by size and, based on an assumed 12 mm/yr-1 coral growth rate, separated into year classes post reef deployment. Size classes were then compared with fish abundance data. Correlations were found with Year 1 coral recruits and damselfishes (Pomacentridae), reef butterflyfish (Chaetodon sedentarius), and grunts (Haemulon spp.). Additionally, correlations were found between Year 3 recruits and all fish species combined, and between Year 4 recruits and reef butterflyfish. Thirty coral recruits were counted on the settlement plates, with P. astreoides making up over 63% of the recruits. Due to the low number, rigorous statistical analysis could not be performed on the data; however, CaCO3 plates had almost twice the number of recruits than the other attractants. Recommendations from this study include design of artificial reef with holes and shadowed refuge, placement of reef near natural hard-bottom or reef, and use of limestone aggregate to enhance coral recruitment. Additionally, coral transplantation may be an effective coral recruit attractant, but care should be taken in transplant species selection and collection methodology.