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| Calculation of Relative Body Weight Index of Chub Mackerel in Central East China Sea |
| CHEN Yan,ZHOU Congyu,WANG Yingbin |
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Abstract The relative body weight index (mr ) was calculated in chub mackerel (Pneumatophorus japonicus) based on the fork length and body weight data collected during 2009 and 2010 in the Central East China Sea in or‐der to evaluate the pressure of surrounding environment on chub mackerel stock .T he equation obtained by standard weight (ms ) was established as lg ms=0 .104574L2 +2 .945479L-2 .014981 based on the mid‐values of lg10‐trans‐formed fork length and body weight .The frequency of relative body weight and fork length showed that the range of mr was varied from 45 to 166 at fork length of below 10 cm ,and the range of mr was varied between 82 and 109 at fork length of about 15 cm .The frequency of the variation of mr tended to follow normal distribution ,although the variation of mr was relative large when the fork lengths were within smaller than 10cm and close to 20 cm .The calculation of mr of chub mackerel in the Central East China Sea provided convenience for the comparison of chub mackerels among different seas ,and provided baseline of the status of chub mackerel stock in surveyed area for fu‐ture studies .The index is not affected by the errors of the variation of fish body size ,and can be used in accurate comparison of the individuals derived from different populations with different temporal and spatial characteristics for future exploitation and management .
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Received: 25 March 2016
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