Abstract
Fishing Mortality and Effort BARANOFF in 1918 formulated most of the present theory of the relation of the catch to rate of fishing, rate of natural mortality, of growth and of recruitment. His exposition, in the Russian language, was, however, somewhat inaccessible, and various other workers have discovered parts of the theory without knowing of Baranoff's work. William E. Ricker (Copeia, No. 1; 1944) has been back to Baranoff's paper, and has also corresponded with most of the other workers interested. He has now produced a clear and comprehensive development of the necessary definitions and equations. Formulæ are derived by which the expected catch can be calculated under different rates of fishing—given knowledge of the catch at one rate of fishing, and of the rates of natural mortality, of recruitment and of growth. Such calculations are necessary for advising immediately whether increase or decrease of fishing should take place, and Ricker's statement will therefore serve a practical purpose. He realizes, however, that no method exists at present by which one can extrapolate to determine the best rate of fishing, or the yield in any state very different from the one observed, unless Graham's approximation of 1935 is generally applicable—which remains to be seen. The difficulty in applying, in extrapolation, the kind of formulae developed by Baranoff is that the rates of mortality, growth and recruitment are expected to vary with population density (growth-rate certainly does), and the law of their variation is not known. Graham's approximation assumes a simple law, which may be too crude; but it is regarded by Ricker as possibly the most interesting recent development in the theory of fishing.
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Research Items. Nature 154, 366–367 (1944). https://doi.org/10.1038/154366a0
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DOI: https://doi.org/10.1038/154366a0
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