Kaifu K.,University of Tokyo |
Maeda H.,Fukui Marine Park Center |
Yokouchi K.,Nagasaki University |
Sudo R.,University of Tokyo |
And 5 more authors.
Environmental Biology of Fishes | Year: 2014
The Japanese coastlines along the Sea of Japan (Japan Sea) have been thought to be one of the margins of the distribution range of the Japanese eel Anguilla japonica, and there is evidence that eels had naturally recruited into these areas several hundred years ago. However, recruitment there is uncertain recently, because there seems to be no study that reported glass eel or elver recruitment into the coasts along the Japan Sea for a couple of decades, and the eels inhabiting these areas were probably stocked by fisheries cooperatives. In order to improve understanding of the present-day natural geographic distribution range of this species, we searched for naturally recruited wild eels in the Hayase River system, Fukui Prefecture, which flows into the Japan Sea. Multiple approaches including investigation of glass eel recruitment, comparison of body size, and estimation of habitat use types was employed. During the observation period (from January to July 2010), no glass eels were found at the river mouth of the Hayase River in monthly sampling. Of eels collected in this study (n = 127), no eels smaller than the initial body size of eels for stocking were found in this water system and none were identified as being of wild origin based on the habitat use type classifications from otolith microchemistry (n = 48). This lack of evidence of Japanese eels recruiting into Japan Sea coast waters suggests most eels present there may be stocked eels. Japanese eels could have been distributed naturally along the Japan Sea coast more than in recent years, indicating a possible decrease of the natural distribution range of this species. © 2013 Springer Science+Business Media Dordrecht. Source
Matsuzaki S.I.S.,Japan National Institute of Environmental Studies |
Terui A.,University of Tokyo |
Kodama K.,Fukui Marine Park Center |
Tada M.,Fukui Marine Park Center |
And 2 more authors.
Biological Conservation | Year: 2011
The quality of habitat at and around a spawning site, and the availability of movement between spawning and nonspawning habitats are likely to be important determinants for population persistence in a degraded and fragmented landscape. We assessed the influence of habitat connectivity, habitat quality and invasive species for distributions and local abundance of eggs and larvae of crucian carp (Crassius auratus complex, which is listed as " data deficient" on the Japanese Red List) in agricultural landscapes surrounding Lake Mikata, Japan, where drainage ditches and paddy fields are extensively utilised for spawning (lake or river shores are also used). We investigated the presence and abundance of eggs and larvae of crucian carp and habitat components at 146 sites across a range of presumed spawning habitats. Egg presence was affected strongly by connectivity to the lake (watercourse distance from the lake), and egg abundance was significantly influenced by both connectivity and habitat quality. In contrast, larval presence was primarily related to habitat quality. Larval abundance was influenced by connectivity and habitat quality, but the effect of connectivity was relatively low. Furthermore, larval abundance was negatively related to the presence of the invasive species red swamp crayfish (Procambarus craki) and bullfrog (Rana catesbeiana). Our findings indicate that connectivity, habitat quality and the presences of invasive species are crucial in determining suitable spawning and nursery habitats, but their relative importance may vary depending on egg and larval life stages. We suggest that restoring connectivity, improving habitat quality and removal of invasive species could be effective conservation strategies for the declining populations of crucian carp in agricultural landscapes. © 2011. Source
Matsuzaki S.-I.S.,Japan National Institute of Environmental Studies |
Terui A.,University of Tokyo |
Takeshima H.,University of Tokyo |
Sato T.,Fukui Prefectural University |
And 5 more authors.
Japanese Journal of Conservation Ecology | Year: 2011
Identifying the ecological and life history correlates of local extinction can help us to predict and target extinction-prone species, and to understand the causes and consequences of species extinctions. We examined temporal changes in the native, strictly freshwater, fish fauna around Lake Mikata, a component of the Ramsar wetland, by collecting and integrating fragmentary fish monitoring data for 1978-2007, as well as by conducting broad fish samplings in rivers, ditches, and the lake in 2009 and 2010. We also performed a trait analysis for 22 freshwater fish in an attempt to identify the ecological traits of the species that have disappeared since 1988, when the fish diversity was higher. The integrated monitoring data showed that 5 of the 22 species had disappeared, including endangered species. The generalized linear mixed models incorporating the phylogenetic effects revealed that dependency on spawning substrate (e.g., cobbles and mussels) was the only significant predictor; the species with high dependency on spawning substrate were more likely to disappear. Our results suggest that the loss, degradation, and fragmentation of spawning habitats are the main direct cause of the local extinction of freshwater fish fauna in and around Lake Mikata. Monitoring, investigating, and restoring spawning habitats should be the focus of proactive conservation or management strategies. Source