Bio-Geomorphological Evaluation of the Depression “Katama” Located in the Reef Front as a Fishery Ground

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  • 礁前面の凹地「カタマ」の漁場としての生物地形学的評価
  • ショウゼンメン ノ オウチ 「 カタマ 」 ノ ギョジョウ ト シテ ノ セイブツ チケイガクテキ ヒョウカ

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This paper aims to （1） construct the distribution map of depressions in the reef front， called katama as avernacular term， by literature search for the local history and folklore， and （2） examine the organic linkage among the morphology， deposits， organisms and fishing activities in katama recognized important grounds for local fishermen， by bio-geomorphological research and interviews with fishermen in Yamato Village， Amami-Oshima Island， in the summer of 2015.Our analysis of the distribution map shows that katama is found over the Central Ryukyus （Amami Islands and Okinawa Islands）， but not over the Southern Ryukyus （Miyako Islands and Yaeyama Islands）. We observed that katama was circular or oval in a plan view， and linked to open sea by some narrow grooves. The floor was covered with numerous flat gravels or/and boulders， 5 to 30 cm in diameter. There were small organisms （e.g.， Porifera，Ectoprocta， Mollusca， Crustacea， Echinodermata and Ascidiacea） under the gravels/boulders. According to ourinterview with fishermen， fishes turn the gravels and feed these kinds of small organisms. It shows that fishermen have recognized katama as important fishing grounds with their traditional ecological knowledge. In recent studies， gravel-bed environment （the floor covered with numerous flat gravels or/and boulders） has been noted as important microhabitat of biodiversity in coral reef， especially its function as the feeding ground for fishes. By our interview and literature investigation （e.g.， Nanto-Zatsuwa， an ancient document written approximately 130 years ago）， it is clarified that local fishermen have recognized katama as microhabitat for small organisms, and have been used it as an important fshing ground over many generations. However， the importance of gravel-bed environment has just been attracted by scientists on reef study or marine biology. It is necessary to reconsider the holistic conservation measures of coral reef， with understanding the gravel-bed environment as microhabitat for small organisms.

Journal

  • 沖縄地理

    沖縄地理 (16), 1-18, 2016-06

    沖縄地理学会

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