Sessile Organisms on PVC Panels in the Waters around a Coral Reef of Ishigaki Island, Yaeyama Islands, Japan, Immediately after the Catastrophic Coral Bleaching in 1998

Sessile organisms on PVC panels suspended inside and outside coral reef at Ishigaki Island, Yaeyama Islands, Japan, was monitored for 20 days just after the wide-spread incident of coral bleaching in September, 1998. The settlement of a total of 16 species of algae and invertebrates was recorded. Generally, Enteromorpha sp. (Chlorophyceae) dominated the panels. The percentage area cover, number of species, biomass and algal growth were significantly greater in waters outside the reef

Foraging ecology of the reef fish Dampieria cyclophthalma (Pisces: Psuedochromidae) at Kuchierabu Island

亜熱帯水域に位置する口永良部島の磯においてメギス科魚類の1種メギス Dampieptia cyclophthalma の食性と採餌行動について研究した。146個体の胃内容物の分析によると、本種は底生の無脊椎動物から魚類まで捕食していた。死サンゴ礁の棚や岩の下に生息し、行動圏の広さは9-37㎡であった。本種は岩の下や側面で待ち伏せし、突然飛びついて餌を捕捉した。1回の待ち伏せ時間は平均26から37秒間であり、10分間に7-15回場所をかえて待ち伏せした。岩の下や側面に沿って移動し、待ち伏せ場所間の平均距離は1.4から2.1mであった。本種が待ち伏せ場所をかえるのは、餌の移動範囲が極めて狭く、同じ場所で長時間待っても新たな餌の接近が期待されないためであろう。Diet and foraging behavior of Dampieria cyclophthalma were studied on shallow reef habitats at Kuchierabu Island (30°28'N, 130°, 10'E), southern Japan. This species was especially common at reef in living under ledges and rocks and interstices of dead coral rocks. Most of prey were small fish and benthonic invertebrates, including crabs, shrimps, gastropods, urchins, and polychaetes. Its charachteristic foraging method was to lie in wait for prey species to come near enough for capture and then lunged suddenly and rapidly. After waiting for short periods, the fish moved short distance to another ambush site. Its ambush site was changed frequently, because prey animals did not move about wide ranges

Water movements around the spawning sites of Halichoeres marginatus (Pisces: Labridae)

浮遊性卵を生む磯魚の産卵は、産み出された卵を沖合いに運び出すのに都合のよい場所で行なわれるといわれて来た。しかし、実際に産卵場所の水流が調査された例は極めて少ない。そこで、南西諸島の口永良部島の西浦湾において、浮遊性卵を産むカノコベラの産卵場所の水流が、染料を使って調査された。その結果、産卵場所で投入された染料は、数時間以内にほとんどすべてが沖合いへと移送された。以上のことから、カノコベラの産卵場所は今までの仮説に言われて来たように、産み出された卵の沖合いへの早期移送に適していると思われる。The locations of pelagic spawning sites of inshore reef fish have been believed to favor the quick removal of eggs offshore. However, few studies have measured water movements around such spawing sites. Water movements around the spawning sites of Halichoeres marginatus in Nishiura Bay, Kuchierabu-jima Island, southern Japan, were studied using dye releases. These showed the dye to be almost entirely transported offshore from the sites within several hours. The spawning sites of H. marginatus apparently favor the rapid removal of eggs offshore, as hypothesized

Feeding Ecology of Labrid Fishes at Kuchierabu-jima

南西諸島口永良部島の磯水域において小型のべラ科魚類カミナリベラ属(Stethojulis)の3種、ハラスジべラ Stethojulis strigiventer、カミナリベラ Stethojulis interrupta terina、アカオビベラ Stethojulis bandanensis の成長に伴う食性変化を調査し、ニシキベラ Thalassoma cupido、ヤマヅキベラ Thalassoma lutescens、ツユベラ Coris gaimard のそれらと比較した。小型のベラ類のハラスジベラ、カミナリベラ、アカオビベラの全長約10cmまでの個体、ニシキベラの全長6cm以下の個体、及び中型のべラ類のヤマブキベラ、ツユベラの全長10cm未満の個体では、コペポーダ類、ヨコエビ類等の小型甲殻類が主な餌生物であった。これら小型個体の摂餌場所は小型藻類が繁茂している基質表面(微小藻場)であった。口永良部島の磯水域に生息する主なべラ科魚類において、全長約10cmを境として、それより小型の個体の重要な餌生物は徴小藻場に豊富に生息している小型甲殻類であることが明かとなった。これらのことは、ベラ科魚類において食性は口の大きさなどと関連する体長によって規定されていることを示している。Ontogenetic changes in the diet of three small labrid fishes, Stethojulis strigiventer, Stethojulis interrupta terina and Stethojulis bandanensis, found on shallow reefs around Kuchierabu-jima Island, southern Japan, were analyzed and compared with those of Thalassoma cupido, Thalassoma lutescens and Coris gaimard. Small individuals, less than 10 cm TL in five of the species and less than 6 cm TL in T. cupido, preyed mainly on small demersal crustaceans (e. g., copepods and gammarideans). These small individuals feed from small algal mats growing on the surface of substrate. In conclusion small crustaceans, that are abundant on the small algal mats at Kuchierabu-jima, were the most important prey group for small individuals (less than 10 cm TL) of several species of labrid fishes. The results of this study suggest that feeding habits of labrid fishes are influenced by their body length, which are related to their mouth sizes etc

Leptocephali collected in light traps near coral reef habitats of Ishigaki Island in the southern Ryukyu Island chain

The habitats used by leptocephali are poorly known except for a few studies on their depth distributions or collections of recruiting leptocephali in some areas. Leptocephali have been reported to be collected by light traps in tropical coastal habitats, but their species composition or development stages have not been clarified. We report the collection of small numbers leptocephali in light traps set within and adjacent to coral reef habitats along the west coast of Ishigaki Island of the Ryukyu Island chain of Japan. Four muraenid and one ophichthid leptocephali at the early-metamorphosis stage were collected at the outer reef edge in May and June of 2007 and 2008. Two pre-metamorphosis stage Muraenesox cinereus leptocephali were collected between the inner and outer coral reefs in August 2006. Visible gut contents in the muraenesoscid larvae suggested they were feeding near the reefs. These collections clarify that both metamorphosing and pre-metamorphosing leptocephali can be caught in light traps, but it remains questionable if light traps effectively sample for leptocephali in near-shore habitats. Future research needs to evaluate the degree to which light traps can collect leptocephali by comparing their catches to other evidence about the presence of leptocephali in the same habitats at night

Compositions of prey taxa and size in piscivorous fishes at Kuchierabu-jima, soutern Japan.

魚食性魚類に餌として利用されている魚類の分類群とその大きさを明かにするために、南日本の口永良部島の磯において肉食性魚類の消化管内容物を調査した。調査対象種14科31種723個体中、アオヤガラ Fistularia petimba、ワヌケトラギス Parapercis cephalopunctata、アカエソSynodus ulae、ギンガメアジ Caranx sexfasciatus などの14科31種156個体によって合計339個体の魚類が捕食されていた。この中で、表層性のキビナゴ Spratelloides gracilis が最も多く利用されていた。また、口永良部島の磯においては、体長19.0mmから55.0mm、体高4.0mmから8.0mmの魚類に対する捕食圧が高いことが明らかになった。The gut contents of piscivorous fishes (14 families, 31 species, 723 specimens) collected at the reefs of Kuchierabu-jima, southern Japan, were examined to determine the composition and size of their fish prey. One hundred fifty six of predators in 31 species and 14 families, including Fistularia petimba, Parapercis cephalopunctata, Synodus ulae, Caranx seafasciatus, fed on 339 items of prey. Piscivorous fishes at the reefs ate mainly the pelagic fish, Spratelloides gracilis. The feeding pressure was particularly high in fishes with body length 19.0-55.0 mm and body depth 4.0-8.0 mm at these reefs

Leptocephali collected in light traps near coral reef habitats of Ishigaki Island in the southern Ryukyu Island chain

The habitats used by leptocephali are poorly known except for a few studies on their depth distributions or collections of recruiting leptocephali in some areas. Leptocephali have been reported to be collected by light traps in tropical coastal habitats, but their species composition or development stages have not been clarified. We report the collection of small numbers leptocephali in light traps set within and adjacent to coral reef habitats along the west coast of Ishigaki Island of the Ryukyu Island chain of Japan. Four muraenid and one ophichthid leptocephali at the early-metamorphosis stage were collected at the outer reef edge in May and June of 2007 and 2008. Two pre-metamorphosis stage Muraenesox cinereus leptocephali were collected between the inner and outer coral reefs in August 2006. Visible gut contents in the muraenesoscid larvae suggested they were feeding near the reefs. These collections clarify that both metamorphosing and pre-metamorphosing leptocephali can be caught in light traps, but it remains questionable if light traps effectively sample for leptocephali in near-shore habitats. Future research needs to evaluate the degree to which light traps can collect leptocephali by comparing their catches to other evidence about the presence of leptocephali in the same habitats at night

Colonization of coral rubble by motile cryptic animals: Differences between contiguous versus raised substrates from the bottom

Recent studies have demonstrated that interstices of coral rubble harbor rich and diverse assemblages of motile cryptic animals. Habitats of coral rubble are prone to frequent physical disturbances, so colonization is an important process to maintain the assemblages of these cryptic animals. In order to examine the pattern of colonization, field experiments were carried out using mesh traps with defaunated coral rubble: one treatment placed on the bottom and the other raised 15 cm above the bottom (throughout as "raised") to restrict colonizers to only organisms that are able to invade via the water column. Results of nMDS and PERMANOVA showed significant differences between the assemblages of the bottom and raised treatments. Species-specific variations in the rate of colonization, which were estimated by fitting the von Bertalanffy equation, contributed to the variations in the cryptic assemblages. Generally, decapods and gastropods colonized via the benthic pathway with colonizing individuals moving on the surface of the bottom substrate, while copepods and non-shelled gammarids colonized via the planktonic pathway. Variations in cryptic assemblages in coral rubble microhabitats may be partly due to differences in contributions via the two colonization pathways