台灣東北部卯澳灣九孔(Haliotis diversicolor supertexta Lischke)放流最適體長之研究

Abstract

九孔(Haliotis diversicolor supertexta Lischke)為臺灣的重要經濟性貝類，廣泛分佈在臺灣沿岸的岩礁海域，近年來由於野生九孔數量大幅減少，一些沿海縣市均曾進行九孔放流以增加海域資源量。稚貝養殖成本及不同放流體長會對放流成敗產生關鍵性的影響，適宜的放流體長能使放流九孔存活率增加、減少放流成本，達到放流增殖的目的。因此，本研究之目的即在於找出台灣東北部卯澳灣海域九孔最適放流體長。試驗分為兩部分，養殖池部分，藉由收集養殖池中死殼量來估算飼養時間別之存活率；海域放流試驗部分，進行1.0cm,1.5cm,2.0cm, 2.5cm,3.0cm五體長組稚貝放流，並於放流後第3天、第7天、第14天、第21天、第28天進行回捕，以獲得各體長組之時間別存活率，並合併養殖池與放流後存活率，藉此探討那一個體長組稚貝擁有最高存活率，亦即最適合做為放流體型，結果如下：(1)隨著養殖期間的增長，稚貝存活率呈指數式下降趨勢，(2)放流後五個體長組之存活率均隨著時間的增加呈下降趨勢，(3)在第3天2.5cm與3.0cm二體長組之存活率分別為55.8％及60.8%，第7天均為41.7%，第14天均為27.5%，都明顯高於其他體長組，(4)在合併養殖池與海域放流存活率後，顯示放流後第14天之前，2.5cm組之存活率均明顯高於其他體長組，再考量2.5cm組稚貝所需養殖成本又較3.0m組低，因此，由本研究結果推論台灣東北部卯澳灣海域最適合的九孔放流體長應是2.5cm。

Abalone(Haliotis diversicolor supertexta Liscbke) is a valuable shellfish ranges around the coastal areas of Taiwan. In recent years, the wild abalone resources has undergone a severe decline. In order to enhance the wild abalone population, several coastal counties released the hatchery-reared juvenile abalone to the sea. The optimum size of released abalone could increase the survival rate and reduce the cost, i.e., the size and cost of released juveniles are the critical factors for the seeding program. The purpose of this study is to select the optimum releasing size of abalone in the Mao Aw Gulf, Northeasthern Taiwan. The study included two parts. Firstly, the shells of dead abalone were collected to estimate the survival rate during the culture period. Secondly, five length classes jveniles, i.e., 1.0cm, 1.5cm, 2.0cm, 2.5cm and 3.0cm, were released to the sea. After that,in 3rd, 7th，14th, 21th and 28th days the abalone were recaptured. The result are as follows: (1) the survival rates of juveniles in the cultural ponds showed an exponential decreasing;(2) all the survival rates showed decrease trends for the released abalone of five length classes; (3) after postseeding, in 3rd day, the 2.5cm and 3.0cm juveniles had higher survival rate as 55.8% and 60.8%, respectively. In 7th day, the 2.5cm and 3.0cm juveniles had the highest survival rate as 41.7%. In 14th day, the 2.5cm and 3.0cm juveniles still had the highest survival rate as 27.5%. (4) after combining the survival rates of juveniles in the cultural ponds and the sea releasing, the 2.5cm class juveniles have the highest survival rate before the 14th days. Moreover, the cost of 2.5cm class juveniles are cheaper than that of 3.0cm. Therefore, the optimum releasing size should be 2.5 cm for this study.