Distribution of the oriental weatherloach, Misgurnus anguillicaudatus, in paddy fields and its implications for conservation in Sado Island, Japan

Abstract

The distribution of the oriental weatherloach, Misgurnus anguillicaudatus, together with related environmental factors were surveyed at 185 paddy field locations on Sado Island in Japan. This was associated with the reintroduction of the Japanese crested ibis, Nipponia nippon, which prefers to feed on the loach. Loach were found to be present at 90 locations (49%). Analysis with GIS, GLM and AIC revealed that positive factors for the loach distribution included the presence of an earth ditch, the connections at outlets and the proportion of paddy field area within an 800 m radius. Conversely, pumping-up water irrigation and flow irrigation affected loach distribution negatively. In an interview survey that was conducted concurrently, older farmers in the area recalled that the loach had once been distributed over almost the entire island (89/96, 93%) about half a century ago. The farmers also suggested that the impact of agricultural chemicals was one of the main reasons for loach reduction or local extinction. A map of the current potential loach distribution was made using the best fit model from GIS variables. The loach was expected to be distributed in the Kuninaka region with high probability (60-100%) and in patches in the Osado and Kosado regions with low-medium probability (10-50%). As a feasible scenario for the conservation of the loach, another predictive map of the loach distributions was made using a model fit based on the GIS variables and outlet connection, in which the all of the outlets were presumed to be connected to the ditches without gaps. In this case, the loach were expected to be distributed almost throughout the paddy fields with medium-high probability (40-100%). In another scenario that presumed the complete land consolidation of all the paddy fields, the probability of loach occurrence was low (0-30%) throughout the island with the exception of the island's center in the Kuninaka region.

Predicting distributions of seven bitterling fishes in northern Kyushu, Japan

“…Because most of these fishes are endemic (Arai and Akai 1988;Arai et al 2007), Japan is regarded as a hotspot of bitterling diversity (Miyake et al 2011). However, Japanese bitterlings are now under the threat of extinction because of anthropogenic effects (Katano and Mori 2005) and are consequently listed in the Japanese Species Red List (Ministry of the Environment 2007).…”

Habitat factors affecting the distribution and abundance of the spinous loach Cobitis shikokuensis in southwestern Japan

“…Although these species are commonly characterized by their benthic lifestyle and elongated body morphology, they exhibit species-specific adaptations to various benthic habitats; for example, Misgurnus anguillicaudatus inhabits muddy habitats of paddies and their associated ditches (Kano et al 2010) and adapts to feed on detritus (Watanabe and Hidaka 1983), whereas Niwaella delicata prefers cobble-boulder substrates in middle to upper reaches of rivers and feeds primarily on attached algae (Niwa 1976;Hiramatsu 2004). Owing to such species-specific habitat requirements, many of them are sensitive to habitat degradation by human activities (e.g., sedimentation, channel modification) and are now listed as threatened (e.g., Kirchhofer and Hefti 1996).…”

Potential distribution of Tridentiger barbatus (Günther 1861) and Tridentiger nudicervicus (Tomiyama 1934) in the Seto Inland Sea, western Japan

“…These models have been applied to terrestrial conservation and restoration programs, providing an effective first step toward establishing land management priorities (Scott et al 2002). In recent years, studies of freshwater fishes using SDMs based on GIS have been increasing in Japan (Kano et al 2010;Sato et al 2010;Onikura et al 2012). However, previous research focusing on shallow water fishes had been limited to species considered as important fishery resources such as red sea bream and flounder (Hori 2012).…”