Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Ecology


Standardization of the body area for scale sampling for growth studies of fish becomes more essential if the a value in the Fraser-Lee equation is to be standardized as suggested by Carlander (1982). In a study on yellow perch (Perca flavescens) from West Okoboji Lake and Clear Lake in Iowa, the body area located at the tip of the pectoral fin below the lateral line was found to be the best area for scale sampling. This area exhibited the lowest variability in scale size and the lowest frequency of regenerated scales of the 10 areas sampled. The optimum number of scales to be sampled from the best area was three scales if at least one readable scale is sought. No significant difference in the body-scale relationship was found between sexes nor among the four seasons in which fish were sampled. There was a significant difference in the a value of the regression equation between West Okoboji and Clear Lake samples. The number of scales along the lateral line did not differ significantly among various fish lengths nor between sexes or the two sampled populations. The scale shape (scale radius/diameter ratio) changed in young fish as the fish grew in length until a total length of about 100 mm was reached, beyond which the scale shape remained constant. This feature of change in the scale shape contributes to curvilinearity in the body-scale relationship in young fish. Key scales sampled in two previous studies varied more in scale radius and in body-scale relationship than scales sampled from the best area;Reference;Carlander, K. D. 1982. Standard intercepts for calculating length from scale measurements for some centrarchid and percid fish. Trans. Amer. Fish. Soc. 111:332-336.



Digital Repository @ Iowa State University,

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Ahmad Hassan Abdu-Nabi



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119 pages