Relationships between ayu Plecoglossus altivelis altivelis ...
Transcript of Relationships between ayu Plecoglossus altivelis altivelis ...
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Relationships between ayu Plecoglossus altivelis altivelis andother organisms in stream communities
Osamu KATANOïŒ1, Shinichiro ABEïŒ1 and Tomoyuki NAKAMURAïŒ2
Abstract Although ayu Plecoglossus altivelis altivelis did not change the abun-dance of inorganic nutrients such as phosphorus and nitrogen, ayu decreased theabundance of diatoms and increased the abundance of blue-green algae such asHomoeothrix. The intensive scraping of ayu also reduced the number of chironomidand tipulid larvae that mainly inhabit the upper surface of cobbles and boulders, andincreased the percentage of ephemeropteran nymphs such as Ephemeroptera. Ayu hada negative effect on other omnivorous fishes such as Japanese dace Tribolodonhakonensis and pale chub Zacco platypus. In contrast, the presence of Japanese dace,pale chub and pike gudgeon Pseudogobio esocinus esocinus enhanced ayu growth bydecreasing the number of algivorous invertebrates and increasing the algal biomassthrough trophic cascades. Interspecific relationships in stream ecosystems are thoughtto be very important for the management of biodiversity and ayu growth.
Key words: aquatic insect, ayu, benthic algae, stream community, trophic cascade
2005幎11æ30æ¥åçïŒReceived: November 30, 2005ïŒïŒ1 äžå€®æ°Žç£ç 究æå æ°Žé¢ç ç©¶éš ã386-0031 é·éçäžç°åžå°ç§1088ïŒNational Research Institute of Fisheries Science, Freshwater Fisheries Di-
vision, 1088 Komaki, Ueda, Nagano 386-0031, JapanïŒïŒ2 äžå€®æ°Žç£ç 究æå æ°Žé¢ç ç©¶éš ã321-1661 æ æšçæ¥å åžäžå®®ç¥ 2482-3ïŒNational Research Institute of Fisheries Science, Freshwater Fisheries
Division, 2482-3 Chugushi, Nikko, Tochigi 321-1661, JapanïŒ
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Fig. 4. Relationship between dietary overlap calcu-lated using the Schoener index T and degree ofgrowth facilitation for ayu that was calculated as(mean growth rate of ayu in pools with other spe-cies or 10 ayuïŒ/ïŒmean growth rate of ayu inpools with only 5 ayuïŒ. Broken 1 line indicatesthe growth rate in pools with 5 ayu. AfterKatano et al.ïŒ2006ïŒ
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ç©é¢ä¿ã«ããšã¥ã矀éç解ã®è©Šã¿â. çççæ 9,
1-10.
å·é£éšæµ©å, 1972: ã¢ãŠã®ç€ŸäŒæ§é ã®é²åå²çæ矩ã«ã€
ããŠ. æ¥çæ èª, 22, 141-149.
å®®å°äŒäžé, å·é£éšæµ©å, æ°Žé信圊, 1976: åè²æ¥æ¬æ·¡æ°Ž
éé¡å³é. å šæ¹èšæ°ç.ä¿è²ç€Ÿ, 倧éªïŒ462 pp.
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