Coral recruitment patterns in high-latitude coral communities in southwestern Shikoku, Japan

Larval recruitment plays an important role in determining the structure and dynamics of coral communities. We examined the recruitment pattern of scleractinian corals using artificial substrates at three sites of high-latitude coral communities along the coast of southwestern Shikoku, Japan. At each site, 8 or 10 settlement plate pairs were deployed for 2 months at 1to 2-month intervals for 2 years. Coral recruitment was observed on settlement plates deployed from May to September. Recruit densities were highest in July-September 2007 and June-August 2008, with 1.7 and 2.1 recruits per plate pair, respectively. Recruitment was dominated by Pocilloporidae, which accounted for 72.1% of the total recruits, while Poritidae and Acroporidae represented 12.6% and 6.0%, respectively. This was inconsistent with the coral community structure in the study area. Each taxonomic group exhibited a distinct recruitment pattern. Pocilloporidae recruited between May-July and September-November, mostly in the early half of those periods, which corresponded to times of observed larval releases in the study area. Poritidae also recruited in the same period, with no apparent peak. Acroporidae recruited over a relatively short period from July to August, which corresponded to the observed period of their spawning in the study area. Larval coral recruitment in the study area was characteristic of high-latitude coral communities in having lower settlement rates and a higher proportion of Pocilloporidae to total recruits than do Pacific coral reef communities.