短報 SHORT COMMNICATION
Diference of ratio of dead lnversiunio jokohamensis individuals between two ditches where presence of temporary drying up and the environmental property are different
Wataru KAKINO1)*, Toshishige ITOH2), Yutaka YOSHIDA3), Atsushi KOBAYASHI4)
1)National Research Institute of Aquaculture, 2482-3 Chugushi, Nikko, Tochigi 321-1661, Japan2)Enoshima Aquarium, 2-19-1 Katasekaigan, Fujisawa, Kanagawa 251-0035, Japan
3)Tochigi Prefectural Fisheries Experimental Station, 2599 Sarado, Ootawara, Tochigi 324-0404, Japan
4)Keika Boys Junior & Senior High School, 5-6-6 Shiroyama, Bunkyou, Tokyo 112-8612, Japan
1)独立行政法人水産総合研究センター内水面研究部増養殖研究所 〒321-1661 栃木県日光市中宮祠2482-3
2)新江ノ島水族館 〒251-0035 神奈川県藤沢市片瀬海岸2-19-1
3)栃木県水産試験場 〒324-0404 栃木県大田原市佐良土2599
4)京華学園中学,高等学校 〒112-8612 東京都文京区白山5-6-6
Abstract: The captured lnversiunio jokohamensis individuals and their inhabiting environment were investigated in the east side ditch (Site 1,drying up ditch) and the west side ditch (Site 2,not drying up ditch) in a valley after a period of temporary drying up to assess the influence of drying up on the Inversiunio jokohamensis individuals in Site 1 and consider ditch structure to relieve the influence on September 18 and October 24, 2010. As a result,the ratio of dead individuals and the body length distribution had a significant difference between both sites (P<0.01). In addition,dead individuals of all body length sizes were confirmed in Site 1. The number of individuals has decreased accompanying growing of the body length in Site 1. Methods to modify the ditch structure to relieve influence of temporary drying up are considered essential to maintain the population.
Key words: hill-bottom valley, earthen ditch, body length distribution, dehydration, bottom sediment
摘要
一時的な水涸れ(2010年9月1日〜9月15日(延べ15日間))によるヨコハマシジラガイ個体群への影響を調べるために,2010年9月18日に栃木県東部の谷津の水涸れが確認された西側水路(Site1)で,10月24日に,確認されなかった東側水路(Site2)で採捕調査と生息環境調査が行われた.その結果,両水路間で斃死率に有意な差が認められた.また,斃死率が高かったSite1において,採捕された全ての殻長規模で斃死個体が確認された.さらに,Site1では一時的な水涸れが生じた際に岸側(山側)がコンクリート化されていたために湧水供給が無かったことを踏まえ,水涸れ時に湧水供給(根垂れ水)が可能な岸辺の確保,個体が潜行し,水涸れ期間中に退避できる底質について指摘した.
Received 14 February 2011, Accepted 12 July 2011* e-mail: kakino@vmas.kitasato-u.ac.jp
Present Address : Department of Environmental Bioscience School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada, Aomori 034-8628, Japan
現所属:北里大学獣医学部生物環境科学科 〒034-8628 青森県十和田市東二十三番町35-1
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