Distributional survey of large branchiopods of rice paddies in Shiga Prefecture,Japan: a Lake Biwa Museum project based on lay amateur participation

A distributional survey of the large branchiopod crustaceans of the rice paddies of Shiga Prefecture, Japan, was conducted by the Lake Biwa Museum in May and June of 1999 and 2000. Collecting kits were issued to over 100 lay Field Reporters, who returned all samples, usually dried, to the museum for processing. Their 242 species-lots were augmented by 146 from Grygier, 46 from Ida, and 41 from other museum staff. Apart from this survey, 50 additional records in 1997–2000 were also taken into account. Seven species were recorded in the prefecture's southern half: Branchinella kugenumaensis (Ishikawa), Caenestheriella gifuensis (Ishikawa), and Lynceus biformis (Ishikawa) with wide distributions; Triops longicaudatus (LeConte) and Leptestheria kawachiensis Uéno limited to paddy areas around the south end of Lake Biwa; and Eulimnadia sp. mostly in remnant paddy areas threatened with urban development in Otsu city, with Triops granarius (Lucas) at a single such site in Otsu. In the prefecture's northern half, only B. kugenumaensis and C. gifuensis occurred to a limited degree. Possible reasons for these differences are discussed. Data pertaining to species co-occurrence and occurrence relative to the ongoing program of paddy field consolidation in the prefecture are presented and discussed. Success of the survey was due to the use of Field Reporters, who were able to provide a high degree of coverage of the study area, as well as the clearly defined habitat, the low number and easy recognizability of species, and the collection of voucher material from all sites. Conservation-related results included the listing of Eulimnadia sp. as a `rare' species by Shiga Prefecture.