Karyotypes and nuclear DNA contents of Pseudolabrus eoethinus and P. sieboldi were studied. Until a recent revision, the two species had been consid-ered a single species (Pseudolabrus japonicus), although two clearly distinct kary-otypes had been reported on several occasions. The karyotype of P. eoethinus was confirmed as 2M+2SM+44ST-A (2n=48, NF=52) and that of P. sieboldi, as 20M+8SM+14ST-A (2n=42, NF=70). Nuclear DNA content in the two Pseudolabrus species and 4 other labrid species from Japan was measured by flow cytometry, and provisionally expressed relative to that of a puffer fish, Canthigaster rivulata, used as an internal standard. The relative nuclear DNA content of P. eoethinus was 2.91±0.03 (n=5), that of P. sieboldi being 3.00±0.05 (n=6). Al-though the two values differed significantly (Mann-Whitney U test, P=0.01, Ucal=0.5), the very small difference between them (average value of latter 103% of former) together with karyotype comparisons suggested that both pericentric inver-sions and Robertsonian fusion had played a major role in the establishment of the more derived karyotype of P sieboldi.
The larval and juvenile development of Icosteus aenigmaticus are described, based on 21 specimens (5.2-54.6mm in body length, BL) collected from waters off north-eastern Japan, and compared with 3 larval specimens (5.5-25.5mm BL) from Northeast Pacific. This report represents the first record of larvae from Northwest Pacific and the first description of juvenile of this species. Initially, larvae had a slender body obscured by thick membrane, but the body deepened with the growth. Head spines were small and limited to the preopercle outer mar-gin from onset of flexion through juvenile stages, number of spines variable 4-7. The final fin-ray complements being established at about 25 mm BL. Postflexion larvae and juveniles had pigmented blotches laterally on the trunk. Juveniles had 10+9 branched caudal-fin rays, a greater number than usual in percoids.
Little was known about the early life history of Ariake icefish Salanx ariakensis, listed as an endangered species. We described the morphology of lar-vae, based on wild specimens (5.0-24.0mm BL) collected in the Chikugo estuary, Ariake Bay, in 1998. Yolk-sac and early pre-flexion larvae appeared in freshwater or very low salinity regions [salinity (PSU): 0.0-1.0, water temperature: 10.4-12.6°C] with a larva net, but most larvae of S. ariakensis were collected at brack-ish areas [salinity (psu): 20.5-31.1, water temperature: 12.6-16.2°C] in November and December. They could be distinguished from larvae of the other Salangid species by following diagnostic characters: occurring seasons (fall and winter), pre-anal myomere counts over 50, relative location of dorsal and anal fins (anal fin originates under the 6th dorsal ray), and melanophore patterns on the tail.
A total of 23, 404 larval and juvenile fishes, representing over 65 species from 28 families, were collected by monthly seine-net (surf-net) and beam trawl sampling along the littoral zone of a tidal flat in north-eastern Ariake Bay, from March 1998 to May 1999. Dominant species were Konosirus puctatus (63% of total fish number) in spring, Leiognathus nuchalis (12%) in summer, Plecoglossus altivelis altivelis (5%) in autumn and winter (surf net), Favonigobius gymnauchen (31%) and Acentrogobius pflaumii (16%) year-round and Acanthogobius flavimanus (9%) in spring (beam trawl). Characteristically, juveniles of gobiid and some important commercial species, also common in other enclosed bays around Japan, were frequently collected, whereas larvae and juveniles of species endemic to Ariake Bay were rarely collected. Salinity at the study site was almost constant through the tidal changes, being relatively high (ca. 30). The bottom type was a mixture of sand and mud. The results suggested that tidal flat littoral zones not di-rectly influenced by rivers are used as long-term and/or juvenile-stage nurseries for various common non-commercial and commercial species, although it rarely used by early stage larvae of endemic species.
The geographical distribution of the endangered bagrid catfish, Pseudobagrus ichikawai, in Gifu Prefecture, was investigated utilizing literature records, questionnaires and field surveys. The results showed that populations of this species had originally been distributed widely in the middle reaches of rivers of the Kiso, Nagara, Ibi and Shonai River systems, flowing into Ise Bay (facing the Pacific Ocean), but have been decreasing and fragmenting in upper-middle river reaches and branches. The threatened situation of the populations, especially in middle to small scale branches, is noted. Limiting factors of the original distribu-tion range of this species in each river system are also discussed.
A single specimen (HUMZ 178190; 324.0 mm SL) of synodontid lizard fish, Saurida micropectoralis Shindo and Yamada, 1972, was collected by angling at Nago Fishing Port (26°34'N, 127°59'E), Nago City, Okinawa Island, Okinawa Prefecture, Japan, in October 2001. It represents the first record of the species from Japan and the northernmost record of the species in the Indo-Pacific Ocean. The specimen is described and a new Japanese name “kosode-eso” is proposed for the species.
Microhabitats of spawning sites of the three salmonids (honmasu salmon Oncorhynchus masou, which was a probably hybrid of masu salmon O. m. masou, red-spotted masu salmon O. m. ishikawai and biwa salmon O. m. subsp., brown trout Salmo trutta and Japanese charr Salvelinus leucomaenis) were investi-gated from mid September to early December in 1995 and from mid September to late November in 1996 in four rivers (Toyamasawa, Yanagisawa, Yokokawa and Kannonsui rivers), which discharge into Lake Chuzenji, central Japan. Spawning behaviors of honmasu salmon, brown trout and Japanese charr were observed from mid September to late October in all rivers, from late October to early December in all rivers and from late October to early December in the Toyamasawa River, re-spectively. Spawning redds of honmasu salmon and brown trout were observed in a wide range of reaches in the three rivers, while those of Japanese charr were re-stricted in the upper reach of the Toyamasawa River. Honmasu salmon spawned in deeper sites with larger sized substrates than do brown trout. Japanese charr spawned in sites with slow current velocities. Redd superimpositions were ob-served in all species and brown trout and Japanese charr frequently superimposed on the redds of honmasu salmon. The results suggest that the competition between honmasu salmon and brown trout-Japanese charr for spawning sites is reduced by their different spawning periods, but redd superimpositions by brown trout and Japanese charr decrease the breeding success of honmasu salmon.
Examinations of two boxfishes, Ostracion immaculatus Temminck and Schlegel, 1850 and O. cubicus Linnaeus, 1758, based on 37 and 12 specimens respectively, revealed that they are distinguished from each other by the depth of anterior portion of body (36.5-42.1% SL in O. immaculatus vs. 30.8-35.3% in O. cubicus). This morphological character is helpful to identify the two species when their color faded away in preserved specimens.