台灣東南海域鯨豚種類、分佈與棲地特性

Abstract

為瞭解台灣東南海域鯨豚種類、分佈和其棲地特性，本研究使用船隻和漁民回報的方式做調查，船隻調查部分有兩種方式：自1997年4月至1998年8月採用非穿越線調查法，共執行62航次（天），在1998年5月至1999年8月則採用系統性的穿越線（line-transect）調查法，共執行60航次。目擊率估算僅採用穿越線調查法的資料。先前此海域的鯨種記錄僅有5種，本研究再增加了14種，加上調查期間的其他研究，台灣東南海域鯨豚種類至少有20種。本研究在海上調查共確認14種鯨豚，最常見的鯨豚依發現群次多寡為：瑞氏海豚（Grampus griseus）、長吻飛旋原海豚（Stenella longirostris）、熱帶點斑原海豚（Stenella attenuata）、瓶鼻海豚（Tursiops truncatus）、弗氏海豚（Lagenodelphis hosei）和小虎鯨（Feresa attenuata）；漁民回報資料又增加了2種：一種為抹香鯨（Physeter macrocephalus），另一種為熱帶瓶鼻鯨（Tropical bottlenose whale）的新記錄種。穿越線調查期間有效執行4662.4公里，有效目擊75次，平均目擊率為1.61次／100公里；比較兩年間重複調查月份（5-8月），發現1998年（1.93）和1999年（1.82）的目擊率無顯著差異；在不同月份上，7、8月發現鯨豚的機率顯著較3?6月低。地理分佈上，由北至南的在A（2.15）、B（0.89）、C（2.05）和D區（1.57）間也無顯著差異。最常見鯨豚種類在出現的海表水溫上，彼此無顯著差異，但是在離岸距離和水深上則有顯著差異，例如：長吻飛旋原海豚和小抹香鯨屬通常出現在較淺水域，小虎鯨則出現在較深水域。本研究應證此海域鯨豚種類有棲地區隔（habitat partition）之現象。

A boat-based survey was conducted to investigate the fauna, distribution and habitat features of cetaceans in coastal waters of Southeast Taiwan from April 1997 to August 1999. Two survey methods were used: sixty-two days of non line-transect survey were performed from April 1997 to July 1998 and sixty days of line-transect survey were conducted systematically from May 1998 to August 1999. The estimation of sighting rates was based on the data collected from line-transect survey. Relationships between sighted species and its surrounding oceanographic environmental variables were also analyzed. There were five species before this study, and this study found another fourteen species. Combined with all literature records, there are at least twenty species in this area. Fourteen cetacean species were identified in this study. The six most common sighted species were: Grampus griseus, Stenella longirostris, Stenella attenuata, Tursiops truncatus, Lagenodelphis hosei and Feresa attenuata. The records of Physeter macrocephalus and tropical bottlenose whale obtained from fisherman report. The tropical bottlenose whale is a new record in Taiwan. Total on effort of line-transect survey was 4662.4 km and 75 sightings were recorded. The average sighting rate was 1.61 sightings/100km. Between-year comparison of sighting rates during the period of May and August showed no significant difference between 1998(1.93 sightings/100 km) and 1999(1.28). Among-area comparison of sighting rates were no significant difference among the A region(2.15 sightings/100km), the B region(0.89), the C region(2.05) and the D region(1.57). The occurrence of all the six most common sighted cetaceans was not significantly associated with its surrounding sea surface temperature, but was significantly associated with (1) its distance away from the land, and (2) the water depth. For example, sightings of S. longirostris were consistently occurred in the shallowest water, while F. attenuata were found in the deepest water. The result suggests the existence of habitat partition between these most common sighted cetaceans.