On the Trophic Composition of Catched Fishes

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概要

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• The author reported in the previous paper that total weight of catch except that of shells and weeds from various bays of Japan was proportional to annual average quantity of suspensoid in the water of the bay. Accordingly, it is disirable for fisheries economics to have a fish population in the bay of such composition as to be expected to give the most valuable products, since the weight of catch in total is controlled by the condition of the bay. Here the species in the catches in 1949 from various bays in Japan are grouped into three trophic categories, plankton-feeder (2nd consumer which feeds on producer the plants and 1st consumer) benthos-eater (3rd consumer) and pisci-predator (from 3rd or 4th to higher consumer). And a equation. C=2+7.3K+27K2 is obtained, where C is percentage fraction in weight of the 3rd group and K=Cl0•D•B/10000 (Cl0 is annual average of Cl‰ in the surface layer of the bay, D the average depth in m. and B the breadth in km. of the mouth of it). The more oceanic character has a bay, the more increases the C-value until it attains to Ca. 30 the value for all coastal fisheries in Japanr in 1949. While this value for past 35 years varies from 11 to 33 as shown in Fig. 2, where it is comparedd with the results studied by H. S. SWINGLE on the populations in 88 fertilized ponds in Alabama, United States, though the correlation between those in sea and fresh-weter ponds is not clear. The effect of change in C-value in outside water upon that in bay, and the cause of such change in the sea are left for future study.

• 社団法人 日本水産学会の論文

著者

• 花岡 資

  内海区水産研究所

関連論文

• 海水中の懸濁質に関する研究-IV : 懸濁質係数と消散係数および濁度との関係
• Studies on Suspended Matter in the sea-I:On "Suspension Factor" and its Meaning
• On the Trophic Composition of Catched Fishes

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