台灣東部沿海密毛龍蝦之脫殼成長研究

Abstract

甲殼類的成長研究比魚類較為複雜，因為其成長依賴脫殼活動，且缺少可用來估計年齡的硬組織。為瞭解台灣東部沿海密毛龍蝦族群之脫殼與成長，本研究利用蓄養方式來進行研究，實驗期間(2007年9月至2009年3月)記錄其脫殼成長量、脫殼間期、水溫及斷足再生率等資料。實驗總樣本數為133隻，其中雄蝦65隻，頭胸甲長(CL)範圍：42.4 - 112.1 mm；雌蝦68隻，頭胸甲長範圍：40 - 92.8 mm。研究結果顯示，密毛龍蝦終年都有脫殼活動發生，主要脫殼活動集中在夏季，共使用156筆脫殼成長量及130筆脫殼間期資料，主要分佈在頭胸甲長 40 - 70 mm；平均脫殼增加量為0.68 ± 0.51 mm (mean ± standard deviation)；脫殼增加量不隨著水溫變動及龍蝦體型大小而受影響；脫殼間期(IP)與CL之關係為：雌性：IP = 66.019 + 0.945 × CL; 雄性：IP = 50.467 + 1.2709 × CL。脫殼間期會隨著水溫之升高而縮短，隨著體型之增加而延長；脫殼後其斷失步足再生長度比率為0.80 ± 0.18，斷足再生長度比率在雌雄間沒有顯著差異，但與龍蝦體型大小有關，斷失步足不影響其脫殼增加量。本研究分別利用三種成長模式(von Bertalanffy growth equation (VBGE)、脫殼成長模式及隨機脫殼成長模式)描述台灣東部沿海密毛龍蝦之脫殼成長。所估得VBGE參數如下，雌蝦CL∞ = 87.68 (mm)，k = 0.137 (yr-1)；雄蝦CL∞ = 86.04 (mm)，k = 0.207 (yr-1)。脫殼成長模式結果顯示雄蝦較雌蝦成長快速，推測雌雄別最大平均頭胸甲長約為75及90 mm。利用隨機脫殼成長模式，考慮龍蝦個體間脫殼成長之變異，預測其成長軌跡及未確定性，其結果顯示密毛龍蝦個體間成長變異很大。本研究結果與其他研究相比，結果顯示本研究密毛龍蝦之成長較其他研究來的緩慢。本研究建議利用隨機脫殼成長模式來描述台灣東部沿海密毛龍蝦之脫殼與成長，結果可進一步用來建立龍蝦年齡-體長表(Age - length - key)，作為資源評估模式輸入資訊，以期能達到保護及資源永續利用的目標。

Growth study of crustacean is more complex compared to that of fish, because crustacean growths only after molting and they don’t have any hard parts for aging (such as otolith, spines, vertebrae and scales) for aging. The objective of this study was to quantify the growth of spiny lobster, Panulirus penicillatus, in the eastern coast of Taiwan by rearing them in a laboratory. A total of 133 lobsters (65 females, ranging from 42.4 to 112.1 mm, CL; and 68 males 40 to 92.8 mm CL) were reared from September 2007 to March 2009, and 156 molt increments (MI) and 130 intermolt periods (IP) were recorded (maily from lobsters of 40-70 mm CL). Results showed that molting occurred throughout the year with a peak in summer. No significant relationship was found between MI and CL or water temperature, and the mean MI was 0.68 ± 0.51(S.D.) mm. However, the IP was affected by the size of lobster. The relationship between IP and CL was IP = 66.019 + 0.945 × CL for females and IP = 50.467+1.2709 × CL for males. The mean limb regeneration ratio was 0.8 ± 0.18. The limb regeneration ratio was independent of sex, but dependent on the size of lobster, and there was no effect of losing limb on molt increment. Three growth models (von Bertalanffy growth equation (VBGE), molt-process growth model, and stochastic molt-process growth model) were used to describe the growth of P. penicillatus. The estimated VBGE parameters were CL∞ = 87.68 mm，k = 0.137 yr-1 for females and CL∞ = 86.04 mm，k = 0.207 yr-1 for males. The results of molt-process growth model indicated that males were growing faster and attaining a larger size than females. Using the stochastic molt-process growth model to account for the variation in growth, the results suggested that there was a high variability in size-at-age between individuals. Compared to other studies, the results suggested that P. penicillatus grow slower in this study. This study suggests that using stochastic molt-process growth model for modeling the molt and growth of spiny lobster P. penicillatus in the eastern coast of Taiwan. Furthermore, the recommended model can use to develop the important age-length key (with uncertainty) as input for the stock assessement.