Survival rates of juvenile coral reef fishes differ between patchy and continuous habitats
Authors: Nanami, Atsushi; Nishihira, Moritaka
Source: Bulletin of Marine Science, Volume 69, Number 3, November 2001 , pp. 1209-1221(13)
Abstract:Predation has been thought to be a major factor organizing coral reef fish assemblages, and some reports have suggested that predation pressure varies according to the habitat type. We hypothesized that variation in predation pressure is caused by the spatial patterns of coral colonies, i.e., a continuous or a patchy distribution. We conducted field experiments to determine whether (1) survival of juvenile varies between sites with different habitat characteristics, (2) predation pressure is density-dependent, and (3) small-sized juveniles are susceptible to predation. For experiments, juvenile Dascyllus aruanus were released into model coral colonies, covered or not covered with a cage, set at two contrasting sites (continuous habitat: continuous reef; patchy habitat: sandy bottom) on a coral reef in Okinawa. The density of predators was not significantly different between continuous habitat (continuous reef) and isolated habitat (sandy bottom). Just after the start of the experiment, a higher proportion of juveniles moved out from the model colonies at continuous reef, while a smaller proportion of them tended to stay in the colonies at sandy bottom. Fish survived significantly better in the uncaged treatment at continuous reef than at sandy bottom. The survival of large juveniles was greater than that of small juveniles, although it was not significantly different. Although predation pressure did not have a density-dependent effect on juvenile mortality, the trend toward density-dependent survival was stronger at sandy bottom than at continuous reef, suggesting that a density-dependent effect of predation might occur more frequently in isolated habitat. Our findings indicate that predation pressure is affected by the habitat structure.
Document Type: Research Article
Publication date: November 1, 2001
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