台灣東北部卯澳灣海域之海膽生物多?性與年齡決定研究

Abstract

台灣東北部海域由於其特殊的地理位置，擁有相當豐富又多樣的海洋生物資源，其中靠近三貂角的卯澳灣擁有豐富的九孔、龍蝦、海膽等等海洋生物資源。為瞭解目前該海域海膽的種類、族群量、分佈與年齡，本研究以二階段方式調查台灣東北部卯澳灣海域的海膽種類及數量。首先依據該海灣底質特性劃分為第 I 、II 、 III 、 IV 及 V 區五個小海區。第一階段，在第 I 、 II 、 IV 區三個小海區中分別隨機選取 1 個點，第 V 區隨機選取 2 個點，以長 100m ，寬 lm 的穿越線，進行垂直海岸的抽樣調查；第二階段再依據第一階段的結果，分別選取水深 3m 、 6m 、 9m 三種深度，進行等深線的詳細抽樣調查。調查過程中，記錄海膽的種類、數量及深度，並輔以拍照。此外並分析紫海膽間步帶骨片之氧穩定同位素，及利用氧穩定同位素與溫度的逆向關係，推估溫度所對應之成長月份，以決定海膽之年齡。 在第一階段垂直海岸的抽樣調查中，所有海膽種類密度隨著深度的不同呈現顯著差異。在第二階段 27 條等深線的調查中，共記錄了 5 科11 種2,901隻海膽，其中以白尖紫叢海膽（Echinostrephus aciculatus ）的密度最高，其密度為88.81隻／ 100㎡ ，梅氏長海膽（Echinometra mathaei ）次之，其密度為 16.33隻／100㎡ ，其餘種類密度均低於 10 隻／100㎡ ，依序分別為紫海膽（Anthocidaris crassispina ) ，紫叢海膽（Echinostrephus molaris ) ，口鰓海膽（Stomopneustes variolaris ) ，環鋸棘頭帕海膽（ Pionocidaris baculosa ) ，刺冠海膽（Diadenma setosum) ，冠棘真頭帕海膽 ( Ecuidaris metularia ) ，白棘三列海膽（Tripeustes gratilla ) ，環刺棘海膽（ Echinothrix calamaris ) ，及藍環冠海膽（ Diadema sevignyi ）。在整個海域中，白尖紫叢海膽的密度與其他 10 種海膽的密度有顯著差異，其數量在第 I 、 II 、 IV 區，大多數集中在 3m 的深度， 6m 次之， 9m 非常少，而在第 V 區則大多集中在 9m 的深度。歧異度指數值無論在小海區或深度均低，而且整個海域歧異度指數值隨著優勢種白尖紫叢海膽密度增加呈現遞減趨勢，顯示本海域海膽種類隨著海區、深度、及底質不同呈現多樣性分佈。 藉由氧穩定同位素分析的結果得知，海膽間步帶骨片的成長是由中央環狀的生長層向內側及外側生長。三隻編號分別為 AC004 、AC018 、AC015 的紫海膽，估計出其從定著開始至被採集的年齡分別為 4 . 4 個月、4 . 4 個月、及 1 . 4 個月，顯示海膽的成長是相當快速的。

Northeastern Taiwan coasts, by its unique geographic position, possess abundant and diverse marine bio-resources. There are abundant marine bio-resources of abalone, lobster, and sea urchin in Maoao Bay, northeastern Taiwan. In order to know the species composition, population sizes, distribution, and age of sea urchin in this area. The species and abundance of sea urchin were investigated using two-stage-survey method in this study. The gulf is divided into five sub-areas, i.e., I, II, III, IV and V according to its geological characteristics. One transect line with 100m length and 1m width in sub-area I, II, and IV as well as two transect lines in sub-area V were adopted separately at the first stage survey. Based on the results of the first stage survey, 27 transect lines on depths of 3m, 6m, and 9m contours were adopted at the second stage survey. The species, abundance, depths and photographs were recorded at each survey. Age of sea urchin was determined by the inverse relationship between oxygen isotope values and temperature. The results of the first stage survey showed that the densities of overall species were significantly different by depths. A total 2,901 individuals of five families and 11 species were gotten under the 27 sampling lines at the second stage survey. Among them, the density of Echinostrephus aciculatus was the most one with density88.81 individuals/l00m? and that of Echinometra mathaei was the next one with density 16.33 individuals/ l00m?. The densities of other nine species were all less than 10 individuals/ l00m?. Ranking from high density to low one in order were Anthocidaris crassispina, Echinosrephus molaris, Stomopneustes variolaris, Pionocidaris baculosa, Diadema setosum, Ecuidaris metularia, Tripeustes gratilla, Echinothrix calamaris, and Diadema sevignyi. For whole area, the density of Echinostrephus aciculatus and those of other 10 species showed significant differences. The abundance of Echinostrephus aciculatus on depth of 3m was the most, that of 6m was the next, and that of 9m was lowest in sub-areas I, II, and IV, while that of 9m was the most in sub-area V. The values of species diversity indices were low on all areas and depths. The species diversity indices of whole area showed decreased trends when the densities of dominant species, Echinostrephus aciculatus, increased. They indicated that sea urchin showed diverse distributions according to sub-areas, depths, and geological characteristics in this area. The growth directions of interambulacral ossicle were from central-cyclic growth zone to inside and outside according to the analysis of stable oxygen isotope. The age of three sea urchins (Anthocidaris crassispina) coded AC004, AC018, AC015 were estimated as 4.4 months, 4.4 months, and 1.4 months, respectively. They indicated that the growth speed of sea urchin is fast.