Using mark-recapture methods, the movements of the fluvial form of masu salmon (Oncorhynchus masou masou) in a mountain stream on the island of Kyushu, Japan, were studied. Most (78%) of the masu ...salmon were recaptured in the pool in which they had been originally caught and tagged. Of those that moved between pools, the proportion of individuals that moved during the breeding period was not significantly higher than the proportion that moved during the non-breeding period. However, during the breeding period, a higher proportion of larger salmon moved than did smaller fish. The proportion of mobile large males during breeding period was higher than that for small males. Also, it was found that a few individuals showed long-range movement in the autumn. As a long-term movement, 78 individual fish (65%) that were recaptured more than three times showed high sedentary tendencies. Sixteen individual mobile fish (13%) moved and returned to the original pool. Fluvial form of masu salmon in Kyushu show a high sedentary nature; however, large mature males seem to actively move in search of female during breeding period.
The fourspine sculpin Cottus kazika is indigenous to Japan and found in Honshu except for the waters facing the Seto Inland Sea, and was also found in southern Shikoku and eastern Kyushu. This ...species has a catadromous lifestyle and migrates as juveniles from the sea to the middle reaches of rivers to grow. The growth pattern of this fish was investigated by a mark-and-recapture method from July 1994 to December 1996, in the Nigorikawa River, a tributary of the Gonokawa River system, Shimane Prefecture. 0-year-old fish of 50-70 mm total length (TL) occurred in the study area from June to July, grew to 90-140 mm TL by the following April, and attained 160-210 mm TL by December. This fish grew rapidly in September-November and April-July, almost ceasing to grow in July-September. It seems that this stagnant growth phase in summer is a characteristic of the seasonal growth pattern of C. kazika. A rearing experiment indicated that the growth rate of C. kazika was higher at 16-22 deg C than at 12-14 and 24-26 deg C. This result supports the field evidence of a stagnant growth phase in summer in the Nigorikawa River.
Yamame are a fluvial population of masu salmon Oncorhynchus masou (also known as cherry salmon) that typically live in the mountain streams of Kyushu Island, Japan. We estimated the seepage of water ...through spawning redds by injecting carbon ink into the redds and periodically sampling the intragravel water. We found that the survival of yamame from egg deposition to the eyed stage was strongly dependent on the permeability of the gravel. We estimated permeability during two periods, just after spawning was completed and after eggs had reached the eyed stage. We found reduced permeability from the time of spawning to the time when the eggs reached the eyed stage. These results imply that the permeability of redds is one of the most important factors in the survival of embryos from fertilization to the eyed stage of development.
The seven species of freshwater sculpins inhabiting the Japanese Archipelago (6 Cottus and 1 Trachidermus) exhibit various life history characteristics, such as catadromous, amphidromous, lacustrine ...and fluvial (Goto, 1990). Both the fourspine sculpin, C. kazika, and roughskin sculpin, T. fasciatus, have a catadromous life style. The former is indigenous to Japan, being found in Honshu, Shikoku and Kyushu Islands. The species migrates from the middle and lower reaches of rivers to the sea for spawning in late autumn and winter (Miyadi et al., 1976; Nakamura, 1963). However, little is known about its reproductive ecology, the only available evidence being a collection of egg clusters and attending males taken at the mouth of the Nagara River, where salinity ranged from 16 to 18 ppt (River Bureau, Ministry of Construction and Water Resources Development Public Corporation, 1992). This paper reports further aspects of the reproductive ecology of C. kazika.
To understand the geographical patterns of genetic variation in freshwater fishes in western Japan, the genetic structures of populations of Tanakia lanceolata and T. limbata (Teleostei, Cyprinidae) ...in this area were investigated using mitochondrial DNA (mtDNA) cytb sequences. Neighbor-joining trees of mtDNA haplotypes revealed four and three genetically divergent groups in T. lanceolata and T. limbata, respectively. Each group was restricted to one or the other of the geographical regions in the area studied. The patterns of geographical divergence in the two species showed some similarities, which seem to reflect common historical events experienced by freshwater fishes distributed in western Japan. On the other hand, dissimilarities were also found in the patterns, indicating that species-specific historical processes also occurred. Within one region, T. lanceolata was less differentiated than T. limbata, suggesting a difference in the dispersal abilities of the two bitterlings. In addition, several individuals in Kunichika River on Shikoku island were morphologically identified as T. lanceolata but had mtDNA haplotypes of T. limbata. We tentatively suggest that these individuals are hybrids of the two species, but further studies employing nuclear markers are necessary to validate this hypothesis.
Age, growth and maturity of the bagrid fish Pseudobagrus aurantiacus from the middle reaches of the Chikugo River, Kyushu Island, Japan were studied by examination of vertebral centrum and ...histological observations. Marginal increments of vertebral centrum formed annual rings from March to April. The growth of this fish was expressed by von Bertalanffy's equation as L sub(t)=340.41-exp{-0.131(t+0.759)} for males and L sub(t)=266.81-exp{-0.146(t+0.920)} for females, where L sub(t) is standard length (SL) in mm and t is age in years. Males grow faster and live longer than females. The spawning period of this population was considered to take place from July to August (mainly July). The minimum size at maturity was 77.6 mm SL for males and 90.0 mm SL for females. The age at which 50% of the fish reached maturity was 1-year-old for males and 2-year-old for females. The earlier maturity of males may be related to their faster growth.
Embryonic, larval and juvenile development of the catadromous roughskin sculpin,Trachidermus fasciatus, were described using eggs spawned in an aquarium. The eggs, measuring 1.98–2.21 mm in diameter, ...were light reddish-yellow and had many oil globules, 0.05–0.18 mm in diameter. Hatching occurred 30 days after spawning at 2.3–11.3°C. The newly-hatched larvae, measuring 6.9–7.3 mm BL, had a single oil globule, 9–10+25–26=34–36 myomeres and 6 or 7 large stellate melanophores dorsally along the gut. The yolk was almost resorbed, number of pectoral-fin rays attained 16–17, and two parietal, one nuchal and four preopercular spines were formed, 5 days after hatching, at 8.2–8.4 mm BL. The oil globule disappeared, and one supracleithral spine was formed, 11 days after hatching, at 8.9–9.5 mm BL. Notochord flexion began 15 days after hatching, at 9.7–10.3 mm BL. A posttemporal spine was formed 20 days after hatching, at 10.7–10.9 mm BL. The first dorsal fin spines (VII–VIII), second dorsal fin and anal fin rays (18–19, 16–18, respectively) appeared 23 days after hatching, at 12.0–13.7 mm BL. The pelvic fin spine and rays (I, 4) were formed and black bands on the head and sides of the body began to develop 27 days after hatching, at 13.8–15.8 mm BL.Newly-hatched larvae swam just below the surface in the aquaria. Preflexion larvae (8.9–9.5 mm BL), in which the oil globule had disappeared, swam in the middle layer, while juveniles (13.8–15.8 mm BL) began swimming on the bottom of the aquaria. Swimming behavior observed in the aquaria suggested that the fish started to change to a demersal existence at the juvenile stage.
According to conventional views, the rosy bitterling, Rhodeus ocellatus, comprises two subspecies, R. ocellatus kurumeus and R. ocellatus ocellatus, the former being native to Japan whereas the ...latter was introduced into Japan from China during World War 2. To examine the genetic structure of Japanese R. ocellatus, part of the mitochondrial cytochrome b gene from 48 individuals collected from various locations in Japan was sequenced. Three major mitochondrial lineages were found. Based on historical evidence, two of these represent R. ocellatus ocellatus and the third R, ocellatus kurumeus. The existence of two distinct lineages of R. ocellatus ocellatus in Japan suggests at least two colonizations. Some local populations comprised purely R. ocellatus kurumeus, but those from Kashima and Ogori included both subspecies. Because the proportion of R. ocellatus ocellatus in Kashima increased from 1994 to 1995, invasion by R. ocellatus ocellatus into R. ocellatus kurumeus habitats is apparently in progress.
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