A preliminary study on quantitative relations among growth, reproduction and mortality in fishes

• Published in: Population Ecology
• Main Authors: Kitahara, Takeru, Hiyama, Yoshiaki, Tokai, Tadashi
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1987
• Subjects: atlantic cod
• Online Access: http://dx.doi.org/10.1007/bf02515427; https://onlinelibrary.wiley.com/doi/pdf/10.1007/BF02515427

Summary As a quantitative approach to the life histories of fishes, the present paper attempted to predict a relation among reproduction, growth and mortality numerically with a technique of control theory, the discrete maximum principle. A method for predicting the relation was derived on the postulate that natural selection maximized the net reproductive rate subject to a few constraints. The derived method was applied to Atlantic cod and Atlantic herring populations in the Southern Gulf of St. Lawrence as numerical examples. The examples demonstrated that the theoretical reproductive effort and body weight were well consistent with the observed ones every age but the theoretical survival rates were slightly different from the observed ones. For the reasons mentioned below, however, it should be interpreted that the examples rather support the adopted postulate to a certain degree. First, in general, it is very difficult to obtain good estimates of the rates with traditional methods. Second, intense fishing pressure possibly changes the life history parameters to some extent in fish populations. Moreover, the examples also suggested that, to examine the postulate in further detail, similar analyses had to be made with the data of many fish populations on which intense fishing pressure had not been exerted.