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The scientific name Cottus kazika has been used for over a century as valid for the catadromous fourspine sculpin endemic to Japan. However, recent DNA sequence analyses have indicated a sister relationship between two catadromous species, so-called C. kazika and Trachidermus fasciatus with a great phylogenetic divergence, separated from a monophyletic freshwater spawning clade including the other Cottus species and Baikalian sculpins. Morphological, life-historical, ecological, and karyological characteristics have also suggested that the fourspine sculpin so-called C. kazika is neither a member of Cottus nor Trachidermus. Therefore, the fourspine sculpin is transferred to the genus Rheopresbe. The genus and R. kazika are re-described. The genus Rheopresbe is discriminated from related genus Trachidermus by not having bony ridges on both nape and cheeks and also by presence of entopterygoid, and from the genus Cottus by having teeth on palatines and four spines on preopercle ridges.

Acanthopagruslatus and A.schlegelii (Sparidae) are closely related species distributed in northern tropical to temperate coastal waters of eastern Asia. Early life histories of the two species were investigated by seine net sampling in the Tien Yen estuary, northern Vietnam, which is probably the southernmost co-occurrence locality for these species. In northern Vietnam, early juveniles of both the Acanthopagrus species occurred in the Tien Yen estuary from December to March (A.schlegelii) or December to April (A.latus) when temperatures ranged from ca. 16 to 25 °C. The given temperature range is observed twice (spring and autumn) a year in Japan, and A.latus and A.schlegelii early juveniles are abundant respectively in each season. Thus, a thermoperiodicity of early juveniles of the two Acanthopagrus is common Asia-wide. The two species occurred as the same developmental stage, being markedly more abundant and having larger sizes in A.latus. The Acanthopagrus early juveniles inhabited bank waters of the estuary. Although waters continued to be mixed horizontally by temperatures but to be stratified by salinities during the study period, there was little variation in developmental stage and size among stations for both species. The two Acanthopagrus species from Vietnam spawn for the same season and their early juveniles simultaneously use the same nursery ground.

The original version of this article unfortunately contained mistakes introduced during the production process. Tables 1 and 2 were presented incorrectly. The original article has been corrected.

To examine regional specific diversity in development and growth of Ayu (Plecoglossus altivelis) larvae, we collected and compared collections from the Kalong estuary in Vietnam, and the Shimanto and Muko estuary, and the Niigata coast in Japan. Among the four areas, most of the morphometrics through ontogeny were similar except that the snout tended to be shorter and the anus hardly migrated in Kalong larvae. The snout length increased gradually with growth in the Vietnamese larvae, while this value increased significantly until ca. 10 mm BL, subsequently being constant up to 30 mm body length (BL) in the Japanese larvae. The water temperature when the larvae were collected was higher in the Kalong than in most of the Japan sites. Growth-rates estimated from otolith increments were from highest to lowest, Niigata (mean = 0.54 mm/day), Kalong (0.47), Shimanto (0.38) and Muko (0.34). The higher growth-rates were obtained not in Niigata of highest latitudinal region, but in Kalong of lowest latitudinal region. This indicates that Ayu could experience their early developmental stages from the cool temperate to tropical regions, implying the potential biodiversity of this fish species in the world.

To examine the importance of the upper estuarine areas of Ariake Bay as a nursery ground for fish, assemblages of larvae and juveniles were compared among various aquatic habitats. The upper estuaries of the bay (the Rokkaku and Hayatsue estuaries) are brackish, highly turbid waters with high tidal velocities, and differ substantially from the Isahaya area, which has been separated from the bay by a man-made dike, to the middle estuary (the Kikuchi estuary). Abundances of larvae and juveniles were higher in the estuaries than in the open bay and Isahaya areas. Abundant species in the upper estuaries were similar to each other, but differed from those of the middle estuary. This was primarily due to larvae and juveniles of fishes that occurred almost entirely in the upper estuaries, such as Acanthogobius hasta, Boleophthalmus pectinirostris, Coilia nasus, Cynoglossus abbreviatus, Nibea albiflora, Odontamblyopus lacepedii, Trachidermus fasciatus and Tridentiger barbatus. These results suggest that the upper estuaries play an important role as nursery grounds for fishes.

In order to study the physiological characteristics of neoteny in teleosts, the development of the thyroid axis and digestive tract of the ice fish, Salangichthys microdon (Salmonoidei), were examined using wild caught samples in the Yura River and its estuary. In all developmental stages examined in this study, the digestive tract was straight, and no gastric gland was observed, even in adults. Since these features are only observed in larval stages of a related species, ayu, Plecoglossus altivelis (Salmonoidei), it is suggested that the ice fish retains larval features, not only in appearance but also in internal organs. Additionally, the thyroid axis exhibited a unique characteristic. Until the end of the juvenile stage, thyroid glands remained inactive, and no thyroid stimulating hormone (TSH) cells were observed. Activation of the thyroid gland and the first appearance of TSH cells occurred in adults. Since activation of the thyroid axis was generally known to occur by the time larval have transformed to juveniles in several teleosts, a delayed functioning of the thyroid axis was suggested as a specific characteristic, and probably a major factor contributing to neotenic development of the ice fish.

The escape behavior of wild and hatchery-reared juvenile Japanese flounder Paralichthys olivaceus from a dummy predator, gray goblinfish Minous monodactylus, was investigated under artificial light in an experimental tank. When the dummy predator approached, both the juveniles quickly emerged from the sand, escaping primarily by swimming close to the bottom (benthic swimming) rather than off the bottom (off-bottom swimming). It is suggested that juvenile flounders might escape in this manner from a diurnal visual feeder in the daytime, owing to the flounder being virtually undetectable visually when close to the bottom. The average escape swimming speed of an individual of 9.3 total length (TL)/s in wild fish and 9.8 TL/s in hatchery-reared fish was similar to the maximum speed of many fish species. Juvenile flounder escaped more quickly and had a higher swimming speed (v cm/s), when their distance (d cm) to the dummy predator decreased (v = −2.7d + 82.1, r = −0.33; anova, P

Larval and juvenile ayu from seven year-groups (1986, 1987, 1992, 1995, 1996, 1999 and 2000) were collected in the Shimanto Estuary and adjacent coastal waters. The present study focuses on the variation among year-groups in the hatching period estimated by age determination using the otolith. The hatching period of the dominant cohorts in the 1986, 1987 and 1992 year-groups occurred from late October to mid-November. A delay of the hatching period of the dominant cohort was observed from the 1995 year-group, which occurred in late November to early December, and the dominant periods in the 1996, 1999 and 2000 year-groups were observed from early to late December. It appears that the delay of the hatching period of dominant cohorts was not due to a delay of spawning, but a high mortality of early hatched larvae. The water temperature in autumn in the coastal waters adjacent to the Shimanto River has tended to rise over the past 20 years and this trend was especially notable in the late 1990s. The delay in the hatching period of the dominant cohort observed from the 1995 year-group was likely to be related to the rise in seawater temperatures in autumn.

To elucidate the recruitment and movement process of larval ayuin the surf zone of a sandy beach facing Tosa Bay, 31 collectionswere made with a small seine net at intervals of approximately 5days from November 1990 to April 1991. On the basis of seasonalvariations in larval abundance, size, age, duration of residence,and the occurrence patterns of ayu in the surf zone, larval ayuwere classified into two groups: short-term resident (

To clarify the habitats of the ayu in the early stages of development in the Shimanto Estuary, the size and hatching date of the larval and juvenile ayu were examined. Sizes of larvae and juveniles were larger in the center of the flow area than in the waters adjacent to the estuary’s banks, which suggests that larvae shift habitat to the center of flow from the waters along the estuary’s banks. This shift began at approximately 20 mm body length. However, the resident term in the waters adjacent to the estuary’s banks changed with the hatching dates; that is, the early and late-hatched larvae became short and long-term residents, respectively. A similar phenomenon was found also in the juveniles collected in the freshwater section that were migrating upstream. The growth rates of larval ayu in the waters adjacent to the banks tended to decrease with hatching dates. The fluctuations in growth rate with hatching date appear to be a factor leading to the variation of resident term.

To clarify the characteristics of the larval and juvenile fish community in a Japanese estuary, monthly collections were conducted in the shallow waters of the Shimanto Estuary, Japan from July 1985 to June 1987. A total of 49 101 fishes of more than 100 species from 44 families were sampled over the 2-year period. Numerically, Gerres equulus was most common, accounting for 20.02% of the total abundance. Rhyncopelates oxyrhynchus was ranked second, followed by Acanthopagrus latus, Acanthogobius flavimanus, Mugil cephalus cephalus, Parioglossus dotui, and Acanthopagrus schlegeli. Thus, fishes observed in the estuary were mostly marine species that spawn in the sea. The majority of these fish first appeared within the estuary at late postlarval and/or early juvenile stages. Based on their utilization of the shallow waters in the estuary, the majority of species could be categorized as residents. In the Shimanto Estuary, shallow waters are studded with shelters, especially eelgrass beds, which serve as important nursery grounds for coastal and euryhaline fishes.

Meristic counts of early and late wild settled juveniles of Japanese flounder, Paralichthys olivaceus (Paralichthyidae), in Wakasa Bay, Japan, were compared, with specimens collected from 26 sites spread along ca. 1700 km of coastline facing the Japan Sea. Mean dorsal and anal ray counts of the early settled group at Kyoto were significantly larger than those of the late settled group. A discontinuous geographic boundary in mean dorsal and anal ray counts was found around Wakasa Bay and the Noto Peninsula with both means significantly larger in the southern group than in the northern group. Mean ray counts of the early and late settlers at Kyoto were similar to those of the southern and northern groups, respectively. The effect of water temperature on meristic characters was tested on two groups of laboratory-reared juveniles. Mean dorsal and anal ray counts were larger in juveniles reared at higher water temperatures. The early and late settler groups were estimated to hatch in late February and late April, respectively, representing negative response of meristic characters to water temperatures if these two groups hatched out in Wakasa Bay. Differences in the dorsal and anal ray counts between the early and late settled groups at Kyoto can, therefore be attributed to genotypic, not phenotypic variation. This suggests the possibility of transport of larvae of the early group from areas further south to Wakasa Bay by the warm Tsushima Current, a branch of the Kuroshio, which flows northeastward along the coast of the Japan Sea, particularly when the temperature gradation between the south and north areas during these seasons is considered.

To clarify the early life history of Cottus kazika (Cottidae), the ontogeny, osteology, distribution, migration and food habit were examined based on larvae and juveniles collected from coasts and estuaries in western Japan. The sequence of fin completion was pectoral (P1)-dorsal soft-ray part (D2)-anal (A)-dorsal spine part (D1)-pelvic (P2). However, that of calcification was P1-P2-D1-D2-A. Larvae and juveniles of C. kazika are distinguished from those of coastal sculpins of Japan by large preopercle spines, conspicuous parietal spines, the large and densely pigmented pectoral fin and the relatively deep body. C. kazika and Myoxocephalus polyacanthocephalus plus Enophrys bison share these four ontogenetic characters. From the relationship between the growth ring count on the sagittae and total length, the size of embryos at hatching is estimated at 5.2 mm. Larvae are estimated to reach 7 mm in 10 days, 9 mm in 20 days and 11 mm in 30 days after hatching. Hatching dates for larvae collected in the Shimanto estuary in 1987 peaked during the period around the new moon in January. Many free embryos ranging from 4.3 to 5.9 mm were collected using an aqualamp at a rocky shore outside the Yura River mouth, at high salinity (> 33 ppt), but none were collected in the estuary. From beach samples, seasonal changes in body size varied from year to year, and no consistent growth pattern was found, although juveniles were generally larger in late March and April than in January and February. Very few larvae were collected along shorelines where there were no adjacent rivers. Food habit of larvae and juveniles changed with growth. Polychaete larvae, cladocerans and copepods were found in preflexion larvae less than 6 mm. Gammarids were one of the important food items for larvae over 6 mm. Juveniles over 12 mm almost exclusively fed on gammarids. In the Shimanto estuary, larvae and juveniles stayed near the river mouth in January and February, within a stagnant layer where temperature and salinity remained about 12 °C and 20 ppt, respectively. Juveniles tended to move in March when the stagnant layer disappeared in the estuary.

The near-shore migration and settlement phases of Japanese and American flounders of the genus Paralichthys are compared and discussed relative to differences in coastal environments. Field sampling was conducted in Wakasa Bay, Kyoto Prefecture, Japan, where the shelf is narrow, estuarine habitat limited and tidal range slight, and in Onslow Bay, North Carolina, USA, where the shelf is broad, estuarine habitat extensive and tide relatively strong. Distribution of larvae and juveniles suggests Japanese flounder spawn in close proximity to nursery grounds relative to flounder in Onslow Bay. Sampling of planktonic and benthic flounder just seaward of nursery grounds resulted in capture of a wide range of developmental stages in Wakasa Bay (early planktonic to juvenile), but was limited to metamorphosing larvae in Onslow Bay. Vertical distribution of larvae during the night also differed between the Bays. At night most larvae in Wakasa Bay remained near the bottom regardless of tidal stage. In contrast, larvae in Onslow Bay exhibited selective tidal stream transport. Laboratory experiments conducted to examine the behaviour of recently captured wild and laboratory-reared larvae indicated that wild flounder from Onslow Bay had an endogenous rhythm of activity that corresponded to the tide at the time of capture. In contrast, wild flounder from Wakasa Bay and laboratory-reared larvae showed no distinct activity pattern. These results suggest that physical characteristics of the environment influence the early life history patterns of flounders by modifying behaviour of migrating larvae.

In the amphidromous form of ayu Plecoglossus altivelis Temminck et Schlegel, generally the prelarvae hatched in rivers in autumn are drifted down into the sea, where they live throughout the larval and early juvenile stages until spring. In the Shimanto estuary, however, an appreciable number of postlarval ayu occurred not only during March to May, but also during October to February. Furthermore, there was little difference in the size and age between the larvae occurring in the estuary and sea. In the estuary, they reside in the bank waters, during 10-75 day ages and 10-30mm SL. Thereafter, they seem to ascend the river without going out to the sea. The growth rate estimated from the otolith daily rings was higher in the estuary than in the sea beach.

In Shijiki Bay of Hirado Island, diel discrete-depth horizontal tows with a larva net in May 1983 resulted in a total of 2, 350 larval and juvenile red sea bream (2.1-10.7mm SL), and 347 larval black sea bream (2.4-6.2mm SL) being collected. During the daytime, black sea bream larvae were concentrated near the surface, but red sea bream larvae near the bottom, with these tendencies becoming more evident with their growth. During the nighttime, the larvae of both species were dispersed throughout the water column. In the surf zone of the sandy-beaches located in the innermost part of the bay, collections with a small seine net in June and July 1983 gave a total of 241 late-larval and early-juvenile black sea bream (6.2-20.1mm SL), but no red sea bream. The separation of juvenile habitats between these related species seemed to be a consequence of the species-specific vertical distribution pattern differentiated during the pelagic larval period. A possible mechanism for inshore migration in the black sea bream was discussed in relation to their surface occurrence.

Fish larvae and juveniles were collected in the waters of wading depth along sandy beaches of western Japan with a 0.7-mm-mesh, 1.3- by 5-m seine. Presence of Chanos chanos, Salangichthys microdon, Plecoglossus altivelis, Allanetta bleekeri, Gerres oyena, Sparus sarba, Acanthopagrus schlegeli, A. latus, and Lateolabrax latus and absence of Engraulis japonica, Gonorhynchus abbreviatus, Upeneus bensasi, and Macrorhamphosus scolopax distinguished the larval ichthyofauna of surf zones from those in other known biotopes of fish nursery. The surfichthyofauna was usually more diverse in spring and summer than in autumn and winter. Monthly total catches of individuals fluctuated greatly according to the abundances of a few influential species such as Clupanodon punctatus in spring and Plecoglossus altivelis in autumn to winter. Most larval fishes seemed to inhabit surf zones only during daytime. An influence of tidal phases on occurrence of larval fishes was not apparent. Categories of pelagic and demersal components were suggested for surf zone ichthyofauna., Transactions of the American Fisheries Society: Vol. 114, No. 4 pp. 609?618; 1985