Studies on the Recovery of Bleached Corals in Andaman: Fishes as Indicators of Reef Health

Abstract

The corals in Andaman and Nicobar Islands suffered extensive bleaching during April 2010 to the extent of 60-70 % due to elevated sea surface temperature (SST) and a significant portion of that is hitherto dead. This study evaluates the degree of recovery of the coral reefs and reef fishes, a year after the event. Line intercept transect (LIT) surveys were conducted in three sites, namely, North Bay, Tarmugli and Chidiyatapu for assessing coral cover together with visual census of reef fishes along the same transects. It was observed that all sites were quite badly affected during the bleaching period with more than 95 % of the corals being fully or partially bleached. Out of the bleached corals, only 54 % recovered at North Bay, whereas Tarmugli and Chidiyatapu exhibited 81 and 86 % recovery, respectively. The collapse of coral reef systems affected the abundance and diversity among fish species. Due to recovery and new recruitment of corals, live coral cover has increased, and consequently,, abundance of fishes seems to have increased. Understanding the associations of fishes and corals could possibly lead to selection of certain species of fishes as indicators of reef health. The results of the study lead to the hypothesis that fishes, especially those belong to the families, Chaetodontidae, Pomacentridae, Acanthuridae and Scaridae can be potential indicators of reef health.

Mixed-species groups of herbivorous reef fishes show variable responses to ecosystem perturbations in the Lakshadweep Islands, India

“…Unfortunately, a direct comparison between grouping before and after the bleaching event is not possible, since no data are available on mixed-grouping in fishes from these regions before the bleaching event. However, after the 1998 mass-bleaching event, studies reported roving mixed-groups of herbivores in both Lakshadweep and the Andaman Islands [22,32], although the species composition of these groups was not documented.…”

“…The death of corals can also lead to a reduction in the structural complexity of the reefs, eliminating shelter, which can affect the intensity of predation pressure and competition [17][18][19]. Generally, the higher trophic guilds and corallivorous fishes are most susceptible to decline in these situations [20] and herbivores tend to increase in abundance, probably owing to an increase in the algal cover [20][21][22]. Whether mixed-species grouping in herbivorous reef fishes is influenced by these changes or not remains unknown.…”