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Relation between exploitation and production in experimental populations of Poecilia reticulata
Author(s) -
Nagoshi Makoto,
Kanda Takeshi,
Horiya Kenji
Publication year - 1978
Publication title -
population ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 59
eISSN - 1438-390X
pISSN - 1438-3896
DOI - 10.1007/bf02512973
Subject(s) - biology , poecilia , guppy , productivity , biomass (ecology) , population , ecology , fish <actinopterygii> , reproduction , fishery , demography , macroeconomics , economics , sociology
Summary In order to make researches on the effect of exploitation upon fish populations, six populations of guppy were maintained during a period of 331 weeks under conditions of space, light, temperature, pH, and food controlled as much as possible. The six populations were divided into three groups two by two: a control group without exploitation, a 10% rate of exploitation group and a 20 and 33% rate of exploitation group. All the populations repeated an increase and a decrease in number and in biomass about once a year. The exploitation affected the age composition in the populations: in the non‐exploited population adults occupied the largest part, and the more intensive the exploitation the larger the part fry occupied. The exploitation decreased the biomass of exploited populations, but productivity increased with increasing of of rate of exploitation. The relationship between adult and fry could be represented by Ricker's reproduction curve. The form of the curve was changed by an intensity of exploitation. It was thought that exploitation acts as a preventer of aging of populations by removing old fish and results increasing number of fry and productivity.