台灣東北海域齒鰆之年齡與成長研究

Abstract

本研究針對台灣東北海域齒鰆 (Sarda orientalis)嘗試以第一背鰭之硬棘、脊椎骨及耳石做為年齡查定之形質，進行年齡與成長之研究。樣本來自2013年12月至2014年11月於宜蘭東澳新協發定置網與南方澳漁港扒網船之漁獲物，另加入7尾收自台東成功漁港的樣本 (延繩釣)，共195尾齒鰆，樣本尾叉長範圍為30.8-80.2公分，體重 (全重)範圍為0.42-7.69公斤，樣本體長體重關係式為RW = 0.0128 × FL3.0406。 初步研究發現齒鰆的第一背鰭脈管化的情況嚴重，而脊椎骨因無法判讀日輪估計1歲以下樣本的日齡，使得成長參數的估計結果有誤差，因此將第一背鰭之硬棘及脊椎骨捨棄使用。耳石樣本經年輪判讀之後，將判讀為1歲及1歲以下的樣本進行日輪判讀。結果發現日輪介於113天到451天之間，尾叉長接近54公分時年齡約滿一歲，重複判讀之平均百分誤差 (APE, average percent error)為0.81%，變異係數 (CV, coefficient of variation)為1.05%；而年輪判讀結果為1到5歲，耳石年輪判讀之APE值為5.30%， CV值為7.13%。以245天為界線，分別套適Gompertz和von Bertalanffy兩種成長方程式，結果顯示日輪245天以下以Gompertz成長方程式的套適度較好，而日輪245天以上則以von Bertalanffy成長方程式的套適度較好，雌雄合併的Gompertz成長參數為極限體長(Linf) = 61.189 cm、反曲點的瞬時成長率(G) = 2.909 yr-1、體長為零時的年齡(t0) = 0.181 yr，von Bertalanffy的成長參數為Linf = 84.015 cm、成長係數(k) = 0. 322 yr-1、t0 = -2.074 yr。齒鰆的孵化日經日輪回推後，主要介於1到6月之間，與生殖生物學估計產卵季節相近。

Age and growth of striped bonito, Sarda orientalis, in the waters off northeastern Taiwan were examined based on counts of growth rings in the first dorsal spine, stained vertebra and sectioned sagittal otolith. A total of 195 fish was collected from the catches of set-net, danish seine and longline in Dong’ao, Nanfang’ao and Chenggong fishing ports respectively during December 2013 and November 2014. Body sizes of the collected fish ranged from 30.8 to 80.2 cm in fork length, and 0.42 to 7.69 kg in round weight. The relationship between round weight and fork length was RW = 0.0128 × FL3.0406 with r2 = 0.9729. In the preliminary tryout, the first dorsal spine was discarded due to serious vascularization, and the growth parameters estimated using stained vertebra had big bias owing to the lack of daily increments, thus, the sagittal otolith were used for age determination throughout this study. Daily increments on sectioned sagittal otolith were read for fish younger than 1 year while annuli were read for fish older than 1 year old. The numbers of daily increments ranged from 113 days to 451 days, with the average percent error (APE) of 0.81% and coefficient of variation (CV) of 1.05%. For the numbers of annuli ranged from 1 to 5 rings, the precision was 5.30% in APE and 7.13% in CV. The length of fish that reached 1 year old was around 54 cm in fork length. All data were separated at 245 days into two groups for fitting Gompertz growth function and von Bertalanffy growth function, respectively. The Gompertz growth function fitted the fish younger than 245 days was Lt = 61.189 × e(– e -2.909(t -0.181)); the von Bertalanffy growth function fitted the fish older than 245 days was Lt = 84.015 × (1 – e -0.322(t + 2.074)). Back-calculated hatching dates span from January through June closing to the spawning season estimated by reproductive biology study of striped bonito in the waters off northeastern Taiwan.