Feeding-related morphologies and feeding ecology of larvae and juveniles of the gempylid, Nealotus tripes, were analyzed from 73 specimens, 2.3-16.5 mm SL. Morphological changes occurred at about 6-8 mm SL. Feeding took place in daytime, the main food organisms changing with growth as follows: <6 mm SL, copepod eggs, nauplii and copepodites;> 6 mm SL, copepod adults, fish larvae and mysis of macrura.
To clarify the distribution and genetic characteristics of the Ayu Plecoglossus altivelis altivelis on islands in the Tsushima Current area, ecological and genetic investigation was made at eight islands in four major islands or islandgroups, i.e. Cheju Island, Gotou Islands, Tsushima Islands and Oki Islands. We found the Ayu at seven islands in all the four island-groups. Genetic examination with allozyme electrophoresis revealed considerable allele frequency differences between populations of Dougo Island and the other areas at the PGM-1 locus (p<0.001) and also between those of Fukue Island and the others at the GPI-1 locus (p< 0.001). Although size of these two populations on relatively small islands seemed to be small, genetic variability within each population did not appear so small. These suggest that genetic differentiation of these populations has been primarily due to random genetic drift on smaller islands but has accumulated during a considerable length of time, say several thousand years. We discussed importance of protection of their habitats to conserve these genetically unique populations of the Ayu on small islands.
Two specimens of a carangid fish, Scomberoides commersonnianus Lacepéde (568 and 716mm in fork length), were collected by set nets off the northwestern side of Oshima Island, Meitsu, Nango-cho, Miyazaki Prefecture (Pacific coast of Japan) and off Yokata, Toyama City, Toyama Prefecture (Sea of Japan). The specimens represent the first reliable record from Japan and the northernmost record of the species.
We collected two specimens of the temperate bass, Lateolabrax latus, from the Mukai River (10m above the sea level, 1km from the river mouth, chlorinity 26.9 ppm), Tanegashima Island, Kagoshima Prefecture, Japan. These specimens are the first reliable record from freshwater habitats and also the southernmost record of this species.
A specimen of Hoplolatilus marcosi Burgess, 1978 (Perciformes: Malacanthidae), collected from Okinawa Island, Ryukyu Islands, Japan, represents the northernmost record of the species and the first record from Japanese waters. The species is easily distinguished from other members of the genus in having a longitudinal red stripe on the body.
Morphological characters and isozyme patterns of selected specimens of the genus Squalidus were investigated so as to elucidate the nature of an unusual variant in Lake Biwa. Two specimens proved to be of intermediate type on the basis of principal component analysis of 16 external characters and five vertebral counts, and allelic composition of their isozyme patterns. They were considered to be hybrids between S. chankaensis biwae and S. japonicus japonicus.