The distribution patterns of seven Cobitis species are analysed, namely, C. takatsuensis, C. biwae, the yamato complex, the Kyushu form of C. striata (small race), C. striata (middle race), the Hakata form of C. striata (middle race), and the Onga form of C. striata (middle race) in the northern Kyushu Island, Japan. C. takatsuensis is distributed in the upstream areas of some rivers in the northeastern part of the island. The yamato complex is widely distributed in the northern part of the island. The other five species are distributed in five areas separated by mountains. Although the yamato complex and the four striata complex species are often distributed in the same river system, the former inhabit upstream areas, while the latter inhabit the downstream reaches. The results of this study reveal that habitat fragmentation by mountains and the difference in longitudinal distribution lead to this complicated distribution pattern.
Habitat selection of the spined loach yamato complex (Cobitidae) was investigated at the River Saigo, Fukuoka Prefecture, Kyushu Island, Japan, during both the non-spawning (from January to March) and spawning (from April to June) seasons. The study site had one pool, two riffles, and one flood region during the spawning season and is 140 m long, located 4 km stream from the river mouth. The number of yamato complex individuals was checked, and 10 physical environmental parameters were measured to assess the microhabitat in 45 quadrates. The number of individuals was counted each month, and environmental measurements were conducted four times from January to June 2010. Akaike’s Information Criterion (AICc) and Generalized Linear Model (GLM) were utilized for analysis to verify the effect of the important environmental variables on the habitat of the yamato complex. A total of 184 individuals were captured during the non-spawning and spawning seasons. The populations of yamato complex correlated positively with the water depth during the non-spawning season and with short emergent hydrophytes during the spawning season. Individuals of the yamato complex were observed in the riffle part of the river with depth during the non-spawning season and in the temporary water area with vegetation during the spawning season.
Although the Onga River system is relatively small, it is home to three spined loach species, Cobitis takatsuensis, C . sp. ‘yamato’ complex, and C. striata (the Onga form of the middle race). The aim of the present study is to examine the relationship between the distribution pattern of the species and the physical parameters of the habitat. We mapped the distribution of these three species and measured six environmental factors at 86 points in this river system. Model selection was performed with a generalized linear model (GLM) using the AIC (Akaike’s Information Criterion) to find the best model for the distribution pattern of each species. The dependent variable was the presence/absence of each species, and the independent variables were six environmental factors. The environmental factors that had a positive effect were turbidity for C. takatsuensis, turbidity and river gradient for C. sp. ‘yamato’ complex, and turbidity, river gradient and width of dry riverbed for C. striata. In addition, the coexisting fish species also differ among the three loaches. These results revealed that the three spined loach species select particularly different habitats and can therefore coexist in this small river system.
Size-related changes in feeding habits of the dwarf loach Kichulchoia brevifasciata were studied by assessing the gut contents in 43 specimens collected between March 2006 and April 2007. The food items showed rapid changes when the fish reached approximately 35-40 mm of standard length. On the basis of the index of the relative importance of the gut contents (IRI), we identified that small individuals mainly fed on the amoebozoa Difflugia and larvae of the aquatic insect Ephemeroptera, while large individuals mainly fed on the diatom algae Navicula and larvae of the insect groups Chironomidae and Trichoptera. The results indicate that a suitable habitat for this highly endangered species has to contain a very diverse community of small benthic invertebrates to allow recruitment across all ontogenetic stages.