金門地區中國鱟（ Tachypleus tridentatus）的生活史、稚鱟棲地特徵與保育策略之探討

Abstract

中國鱟（Tachypleus tridentatus）為活化石，在演化研究、醫學應用及潮間帶健全指標上，都相當重要。一、二十年前曾廣泛分佈於臺灣西部沿海，近年來由於人類對沿海及潮間帶嚴重的污染與破壞，中國鱟有滅絕之虞，僅剩金門潮間帶在長期戰地政務的保護下，尚有鱟的棲息繁衍之處。然而隨著解除戰地政務所帶來的各項開發計畫，金門的中國鱟也面臨生存危機，急需進行復育與保育的工作。 由野外調查所得的稚鱟體長頻度分佈，配合書鰓數的觀察，已經能確認一至五齡稚鱟的體長分佈範圍。1997年後豐有稚鱟與無稚鱟區的微棲地特徵有顯著的差異，但1998年的調查中則沒有顯著的差異。1998年後豐、北山與瓊林三地稚鱟的微棲地特徵均沒有顯著的差異，但隨著稚鱟年齡的增加，樓地由高潮線漸向低潮線方向移動。 實驗室內成對的成鱟可籍由潮信及砂床的誘引自然產卵。在人工飼育水箱中，鱟卵孵化與稚鱟成長所需要的時間隨著溫度的增加而減少。由孵化時間、稚鱟齡期、稚鱟體長及積溫效應等結果顯示，實驗室內飼養稚鱟的最適溫度為28℃至31℃。 保育策略方面，依據我國現行法規，中國鱟的保育可從物種保育與棲地保育兩方面著手。金門縣政府已於1999年依據漁業法劃設「金門古寧頭西北海域潮間帶鱟保育區」，並自2000年1月1日起至2004年12月31日止訂為禁漁期，藉此使民眾重視生態，進而珍愛自然環境，達到中國鱟保育的目的。

The horseshoe crab, Tachypleus tridentatus, is known as a living fossil. It plays a very important role in evolution and medical research. It is also an indicator species of a healthy intertidal zone. Tachypleus tridentatus once distributed widely along the west coast of Taiwan island decades ago. However, it is almost eliminated from the coast as a result of pollution and degradation. In Taiwan, Tachypleus tridentatus can only be found in Kinmen, a place which was under the protection of the order of martial law. The order was called off in 1992, and the increasing exploitation started to affect the coast. Tachypleus tridentatus in Kinmen is facing survival crisis. Thus, conservation needs to be done in no time. The carapace length distribution of the first-to the fifth-instar was studied by examining carapace length frequency distribution and number of book gills in the field. Characteristics of microhibitats in areas with or without juveniles in Hou-feng were significantly different in 1997, but not in 1998. In 1998, microhibitat characteristics among Hou-feng, Bei-shan and Chiung-lin were not significantly different. We also found that population of juveniles migrated from high-tide mark to low-tide mark with their growth. In laboratory, paired adults could be induced to breed by the lunar cycle and sands in tanks. Duration for egg hatching and juvenile development decreased with increasing temperature. Results from the hatching time, juvenile intermolt period, carapace length and day-degree rule showed that 28?31℃ was the most appropriate rearing temperature for juveniles. The conservation of Tachypleus tridentatus can be done on species itself or on their habitats. According to the ‘Law of Fisheries’, the Kinmen government set up’ The Horseshoe Crab Conservation Area’ in the coast of Gu-ning-tou in 1999, and fishing horseshoe crabs is prohibited from January 1th, 2000 to December 31th, 2004 in this area.