1988 Fiscal Year Final Research Report Summary
Study on the Estimation of Catching Efficiency of Gillnet
| Project/Area Number |
62560190
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General fisheries
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| Research Institution | Tokyo University of Fisheries |
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Principal Investigator |
HIRAYAMA Nobuo Tokyo University of Fisheries, Faculty of Fisheries, 水産学部, 教授 (00017039)
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| Co-Investigator(Kenkyū-buntansha) |
SAKURAMOTO Kazumi ditto, 水産学部, 助教授 (60111689)
YAMADA Sakutaro ditto, 水産学部, 助教授 (60017077)
MATUDA Ko ditto, 水産学部, 助教授 (90026485)
KOIKE Atsushi Tokyo University of Fisheries, Faculty of Fisheries, 水産学部, 教授 (60017027)
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| Project Period (FY) |
1987 – 1988
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| Keywords | fisheries management / catching efficiency / catching system / soaking time of gear / rate of escapement / gillnet / mesh selection |
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| Research Abstract |
In order to obtain the decision factors for catching cotrol management, the catching mechanism of gillnet based on the catch and catching efficiency were studied in mathematical model, and the methods of these estimation were investigated. Likewise, studies on relationship between catch and fish behavior were conducted using rainbow trout. The results were as follows:
(1).Catching model and catching efficiency; the catch C(t) of a unit of fishing gear and catching efficiency x(t) at a certain soaking time t are shown to be C(t) = k_1 /(k_1 -k_2 ) No{exp( -k_2t ) - exp( -k_1 t )} ・・・ (1) x (t) = C(t)/No ・・・ (2), where k_1 is the enmeshing factor, k_2 the escape factor and No the weight of catchable fish school. The estimated values are k_1= 5.00, k_2 = 0.229, No = 1.203kg in case of flat fish. Using Eq.(1), we get the parametors needed for the management of fishing operation.
(2).Relationship of fish behavior and catch; using rainbow trout in an outdoor water tank, fish behavior analysis in darkness was conducted. Also, the relationship of light intensity to catch was investigated by statistically devised experimental method during each experiment. It was observed that the catch increased during sudden decrease of light intensity gradient at a certain time.
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