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Age, growth, and sexual development of the exploited stocks of eastern Pacific albacore, Thunnus alalunga. Partlo , John Middleton

Abstract

Age determinations of albacore are based on concentric marks on the centra of vertebrae. These are shown to be annual by several tests. The 1950 British Columbia albacore fishery was supplied by four age classes III, IV, V, and VI , whose mean lengths at the time of capture 53.4, 61.3, 71.0, and 80.5 centimeters coincide with the mean lengths of size groups in the commercial catch 54.3, 62.3, 71.3, 79.7 centimeters . The relationship of body length to vertebral radius is shown to be rectilinear, and reveals a correlation coefficient of 0.948. The body length weight relation is expressed by the formula, log W = 5̄.088 3.13 log L, where W is the weight in kilograms and L Is the length in centimeters. A histological study of the gonads indicates that the fishery is supported by immature stocks. Male fish showed greater sexual development than female fish of comparable size and age. Gradients of germ cell development were observed within the testis and ovary. Larger gonads showed a centripetal and anterior-posterior degree of spermato and oogenesis.

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