a1 Schools of Medical and Biological Sciences, University of Sydney, Australia
a2 Department of Systems Ecology, Stockholm University, 106 91 Stockholm, Sweden
Population density and the presence of fission products of Holothuria (Halodeima) atra were investigated in surveys taken over 5 years (2006–2010) in the Capricorn Bunker Group, Southern Great Barrier Reef. These surveys were undertaken to document population density over time and assess the potential that asexual reproduction contributes to population maintenance. Over the 5 years a low incidence of fission was evident year-round, with an increase in July and August (13 and 27% of the population, respectively). There was a positive correlation between population density and the presence of fission products across all surveys. Although density fluctuated, there was no significant difference between months or sites. Despite the potential increase that might be expected from fission followed by regeneration, density fluctuated around a mean of 0.77 ind. m−2. Examination of gonads of the small (asexual and sexual reproduction) and large (sexual only) morphs of H. atra indicated a difference in reproductive pattern. Many small morphs lacked gonads during winter and, when they developed gonads, the gonad index (GI) was low. The GI pattern of the small morph indicated that they spawned in summer. In comparison the large morph had conspicuous gonads through the year. The GI of the large morph was high in winter and summer indicating greater, more prolonged spawning activity in these individuals.
(Received February 04 2012)
(Accepted February 12 2012)
(Online publication April 03 2012)