宜蘭地區日本鰻及鱸鰻生長率之比較

Abstract

過去關於鰻魚生長之研究曾指出，鰻魚的成長有性別二態化的趨勢，且鰻魚的成長率與其棲息地緯度有著負相關的關係。但過去鰻魚成長之研究多侷限於特定區域及單一物種，缺少對於同域比較不同種鰻魚之成長。台灣位於亞熱帶及熱帶地區，溫帶鰻及熱帶鰻共同生存在台灣溪流中，因此本研究嘗試進行同域比較台灣宜蘭地區不同種鰻魚之成長，並針對不同性別、生長時期及種間進行體長、年齡與年成長率比較。自2011至2018年從宜蘭河中、下游及宜蘭地區各養殖池分別進行野生日本鰻、鱸鰻及養殖日本鰻採樣，取樣之後，會進行總體長測量與性別、生長時期辨別，利用耳石讀輪得到魚體年齡並回推計算出年成長率，並將其代入von Bertalanffy 成長曲線進行未來成長趨勢的擬合。在性別比較部分，野生及養殖日本鰻體長與成長率於黃、灰鰻時期無性別差異，但於銀鰻時期則出現顯著性的性別差異。另外，除了鱸鰻以外，野生及養殖日本鰻體長與年成長率也出現顯著的生長期差異。依據種間比較結果，顯示在雌鰻體型年齡與成長率，野生鱸鰻皆高於野生及養殖日本鰻，雄性鰻部分除了體型及成長率以外，年齡也出現相似的差異。在von Bertalanffy生長曲線中，兩種鰻魚的雌鰻理論極限體長較雄鰻來的大，且鱸鰻理論極限長度比日本鰻大，未來成長趨勢分別也證實性別二態化及種間差異現象的存在。

In previous studies, sexual dimorphisms were indicated in most of anguillid eels. Furthermore, a negative correlation between the latitude of growth habitat and growth rate was also indicated. However, it’s still a lack of comparison between different eel species in the same habitat. Taiwan located in subtropical and tropical area, and previous studies indicated temperate and tropical eels coexist in several Taiwan rivers. Therefore, this study tried to compare the growth characteristics among three anguillid eels in Taiwan. In addition, we focused on the sexual, stage and interspecies comparison of age, size, and growth rate of them. From 2011 to 2018, wild A. marmorarta and A. japonica were captured in the middle and lower reach of Yilan River, and cultured A. japonica were collected from the eel farms in Yilan. Measurement of total length of each eel and the identification of gender and growth stage were conducted after sampling, and the sagittal otoliths of each eel were removed for age determination. Then, the back-calculation of annual growth rate of each eel was used to fit into the von Bertalanffy growth curve. In the early stage (gray and yellow eel), there were no significant sexual difference in growth among three anguillid eels, but the sexual difference existed in wild and cultured A. japonica while reaching the silver eel stage. Except for A. marmorata, there were significant stage difference in total length and growth rate of wild and cultured A. japonica. According to the result of interspecies comparison, it showed that the growth rate of female eels was higher in A. marmorata than that in wild and cultured A. japonica. Except for total length and growth rate of male eels, the age of male anguillid eels also showed similar pattern. In von Bertalanffy growth curve, female eels tend to have greater maximum length than male eels in both anguillid eels, and A. marmorata have greater maximum length than A. japonica. It also confirmed that gender dimorphism and interspecific differences might exist in anguillid eels.