- 學位論文
台灣西南海域產紅星梭子蟹外部型態統計及生物參數估計
Statistical analyses of external morphological characters and biological parameters estimation of swimming crab, Portunus sanguinolentus, in the waters off southwestern Taiwan.
摘要
紅星梭子蟹 (Portunus sanguinolentus) 是台灣周圍海域中甚具經濟價值之大型食用蟹，其資源開發以台灣西南海域的椼桿拖網漁業和北部海域的籠具漁業為主。棲息於西南海域的台灣淺堆系群，雖經長其開發，但因缺乏相關研究，以致目前對該資源的生物訊息仍未有較為詳盡的瞭解，因而無從訂定管理策略。有鑑於此，本論文利用從1997年11月至2000年4月，每月自作業於台灣淺堆海域 (約北緯 22°30’∼23° 、東經118°20’∼119°30’) 的椼桿拖網漁業漁獲隨機取樣，進行外部型態統計、生物參數估計，期能對該蟹種有較深入的探究。 所取得之標本經整理分群後，先由廻歸模式估算生物參數，以了解所選定的各形質與甲殼長 (carapace width，CW)之間的關係式。結果顯示，體長(CW)－體重(WG)關係式呈現指數次方的關係，且不同生活史之相對成長率亦有所不同。幼蟹的體長－體重關係式為：WG = 1.2953 x 10-4 CW2.8324、已達性成熟的雌蟹為WG = 4.4805 x 10-5 CW3.0660 而已達性成熟的雄蟹則為 WG = 9.3287 x 10-6 CW3.3944。 以Bhattacharya法估算每次脫殼成長量，顯示：雌蟹每次脫殼成長量較雄蟹大。由月別時間序列體長頻度分布，以季節性范氏成長方程式估算成長參數。估得各成長參數分別為：雌蟹K＝1， L∞＝200mmCW，雄蟹K＝1.1， L∞＝206mmCW。其季節性年齡成長，雌蟹為： ; 雄蟹則為 。而由體長轉換漁獲量曲線的方法，估算瞬間全死亡率(Z)及利用Pauly 的經驗方程式，估算自然死亡率 (M)分別為：雌蟹Z＝2.85 /年 (r = -0.996)，M＝0.96 /年；雄蟹Z＝ 2.29/年 (r = -0.980)，M＝1.01/年。由此推算可得：雌蟹的漁獲死亡率 (F) 為 1.89/年，雄蟹則為 1.28/年。相較之下，雌蟹顯然有較高的漁獲死亡率和總死亡率。此外，雌蟹的開發率為0.66，亦較雄蟹0.56為大。 綜合上述結果，對於該系群的生物參數已有初步的瞭解，進一步的族群動態分析，將是未來的研究方向。
並列摘要
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.