Statistical analyses of external morphological characters and biological parameters estimation of swimming crab, Portunus sanguinolentus, in the waters off southwestern Taiwan.
Date Issued
2004
Date
2004
Author(s)
Chang, Hsiao-Chuan
DOI
en-US
Abstract
The swimming crab, Portunus sanguinolentus (Herbst), is an edible crab that has been exploited for several decades in Taiwan. It is one of the most common and economically important crabs caught in the southwestern and northern waters throughout the year. Only a few studies on stock status of P. sanguinolentus populations on Taiwan Banks have been conducted. Management measures are difficult to undertake because that the population parameters and status are not yet known. Therefore, the objective of this study was to estimate population parameters in relationship of morphometric characters, growth and mortality by time series size-frequency data collected from beam trawl fishery on Taiwan Banks (22°30’ – 23°N latitude and 118°20’ – 119°30’ E longitude) from November 1997 to April 2000.
The biological parameters were estimated, i.e., relationships between carapace width and some selected morphometrical characters were investigated by regression models. The results revealed that the relationships of body weight (WG) vs. carapace width (CW) were expressed by power equations: WG = 1.2953 x 10-4 CW2.8324 for immatures and juveniles; WG = 4.4805 x 10-5 CW3.0660 for mature females; and WG = 9.3287 x 10-6 CW3.3944 for mature males.
The length of molt increase was observed by Bhattacharya method. It revealed that scale in female was larger then male in each molt. Seasonal von Bertallanfy growth formula was used for age determination and growth curve was estimated. The growth can be described by the following fitted von Bertalanffy equations, for female: ;
and for male: , respectively.
And further, size converted catch curve was used to estimated instantaneous total mortality (Z); the Pauly’s empirical equation was used to estimate instantaneous natural mortality (M). The results were Z= 2.85/year (r = -0.996) and M= 0.96/year for females; and 2.29/year (r = -0.980) and M= 1.01/year for males. Accordingly, the instantaneous fishing mortality (F) was estimated as 1.89/year for females and 1.28/year for males; the exploitation ratio (E) was estimated as 0.66 for females and 0.56 for males, respectively. The results obtained in this study should conduct a better understanding of P. sanguinolentus population on Taiwan Banks. In further advanced studies, the population dynamic is recommended to understand the stock status in future.
Subjects
紅星梭子蟹
生物參數
外部型態統計
external morphological character
Portunus sanguinolentus
biological parameter
SDGs
Type
thesis
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