11th ICRS Abstract book - Nova Southeastern University

18.649
The Effects of Increased Seawater Temperature upon Butterflyfishes (Family:
Chaetodontidae) at the Satsuma Peninsula, Southern Japan
Daisuke NASHIKI* 1 , Satoshi NOJIMA 2 , Sekio SHINAGAWA 3 , Noritaka
MOCHIOKA 1 , Shigeo KAWAGUCHI 1 , Akinobu NAKAZONO 4
1 Faculty of Agriculture, Kyushu University, Fukuoka, Japan, 2 Amakusa Marine
Biological Laboratory, Graduate School of Sciences, Kyushu University, Amakusa,
Japan, 3 Nutritional and Health, Shimonoseki Junior College, Shimonoseki, Japan,
4 Kyushu University, Fukutsu, Japan
Satsuma Peninsula, which is influenced by the seasonally warm waters of the Kuroshio
Current, is located about 70km north of the northern limit of coral reefs in Japanease
waters. Many butterflyfishes are seasonal in that they fail to survive lower water
temperatures that occur during winter. Recently, the average seawater temperature of the
Kuroshio Current has been rising. If seawater temperatures keep rising, butterflyfishes
will likely over-winter and reproduce. Habitat structure is important, as well. Many
butterflyfish species display preferences for habitat, especially corals. The purpose of this
study was to determine the relationship between butterflyfish assemblage structure and
coral cover to determine if favorable habitat exists that could be utilized while overwintering
should seawater temperature increase. Underwater video surveys were
conducted at 27 stations in September, 2006. From this footage, fish species richness and
abundance were estimated. Coral cover was estimated also and partitioned into six
categories based upon structural features. The communities at each site were clustered
into three groups using ordination and fuzzy c-means method based on the similarity of
species composition between sites. Fish species were clustered also by the same method
into three groups. A significant relationship between one species group and coral cover
was found for some structural categories, thus indicating that favorable habitat to
butterflyfishes existed. The size of individuals included in this group were mostly small
less than 6cm in total length (TL), with one individual only exceeding 10cm TL. This
indicated that most individuals had been transported north by the Kuroshio Current
within the same year and had not over-wintered, but that over-wintering is possible. If
seawater temperatures in winter keep rising, these fishes may over-winter because
favorable habitat exists.
18.650
Small-Scale Variations in The Effects Of Coral Bleaching in Rodrigues
Emily HARDMAN* 1 , Nathalie STAMPFLI 2 , Jules THOMA 3 , Sydney PERRINE 1
1 Shoals Rodrigues, Rodrigues, Mauritius, 2 Department of Environmental Sciences, Swiss
Federal Institute of Technology Zurich, Zurich, Switzerland, 3 School of Ocean Sciences,
University of Wales Bangor, Anglesey, United Kingdom
Rodrigues was one of the few reef locations in the Western Indian Ocean to escape the
mass coral bleaching event of 1997 – 1998, however shallow reef sites suffered from
coral bleaching during 2002, 2005 and 2007. In all years, there were small-scale spatial
variations in the severity of bleaching and associated mortality. In 2002 and 2005,
bleaching was most severe at the northern reef flat sites with mortality occurring at
depths of 0.5 - 2m. In contrast, in 2007 bleaching-induced mortality severely affected one
patch reef in the southern lagoon, although nearby reefs (60%) with low live coral cover (