若狭湾産マダイの年令と成長
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概要
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In the present paper, growth pattern and age composition of the sea bream, Chrysophrys major, are estimated by scale length and fork length of the fish. During the period from April 1958 to September 1959, 1010 specimens caught in Wakasa Bay were examined in the Nishi Maizuru Fish Market, Kyoto Prefecture. They were measured in the fork length, body depth, head length, body weight and on the scales. In this case the scales were collected from the mid part of the body, namely the 5th and 6th scales in the vertical line downwards from the 13-15th lateral line scales. Scale length and each annual ring size were measured along the line from the focus to the basilateral angles. The results obtained are the following. 1. The monthly change of growth rate of marginal region (α) on scale with 1-5 annual rings (under 5 years old) of the fish were examined so as to conjecture the month when the annual ring was formed. Succesive collections of the scales throughout the year have led the writer to believe that scale annual ring is formed in the spring, from March to May (Fig. 2). 2. Average actual annual ring sizes (rn, γn+1) of the scale are plotted against each age in accordance with Walfords growth transformation (Fig. 3). Each point is so well distributed on two lines that these meat at the 6th point. 3. Estimated annual ring size is given from the result of the Walfords growth transfor-mation (Table 1). Fig. 4 shows the relation between fork length (L in mm) and scale length (R in mm). The relation formula is as follows: L=34.2+16.5R+1.7R2. 4. In Table 1, estimated fork length at the time when each annual ring of scale was just formed is obtained by application of the estimated annual ring size of each age to the relation formula. Although results obtained present slightly lower rate, they agree in general with the average actual fork length on the whole, especially whithin the first dozen years or so. Compared with the sea bream of the Inland Sea of Japan, it seemed to me that the sea bream of Wakasa Bay has inferior growth rate about one year in early stage (from 1 to about 7 years old) and two or three years in older age.
- 公益社団法人 日本水産学会の論文