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標題: | 台灣東部海域瑞氏海豚(Grampus griseus)分佈與社會結構 Distribution and social organization of Risso's dolphins (Grampus griseus) in coastal waters of central-eastern Taiwan |
作者: | Ching-Yi Lin 林靜宜 |
出版年 : | 2003 |
學位: | 碩士 |
摘要: | 為瞭解台灣東部海域瑞氏海豚(Grampus griseus)之分佈與社會結構,在2001年到2002年的四月至九月期間,在花蓮縣石梯港進行海上調查。群體隻次與群體組成用以分析瑞氏海豚之時間與空間分佈,於2001年拍攝到的背鰭照片則提供作為個體辨識與社會結構之分析。另外,在樣區重複出現的瑞氏海豚,則使用half-weight index與SOCPROG軟體分析其結群模式(association pattern)。調查期間紀錄到204群次的瑞氏海豚群體,夏季的群體隻次顯著高於春季與秋季,顯示樣區內的瑞氏海豚豐度可能在夏季較高,此現象可能與其食物之一:南魷(Sthenoteuthis oualaniensis)的夏季高豐度有關。瑞氏海豚的出現率在水深500-1500公尺顯著高於500公尺以淺與1500公尺以深。此外,自春季至秋季,瑞氏海豚會季節性地向近岸移動。此現象可能表示其秋-冬季的主食:武裝魷(Enoploteuthis chunii)在樣區的近岸區域,於秋季有高豐度的發生。瑞氏海豚的群體組成依其體色與幼兒存在與否分為:灰色個體群、白色個體群、混合群與育幼群。除了灰色個體群之外,其餘三種群體的隻次和每日時間(10點至18點)呈現正相關,推測可能與瑞氏海豚的夜間覓食行為有關;最大群體(120-200個體)在早上與下午時段的發現率顯著高於中午時段,顯示黃昏前的大群體可能是覓食集結(feeding aggregation)。幼兒在夏季與秋季的發現率最高。求偶行為則最常在春季與夏季發生且最常在混合群出現,顯示灰色與白色個體結群成為混合群的現象,可能與求偶有關。夏季可能是重要的交配季節,因為混合群於該季的發現率最高。至少有670隻個體被辨識出來,其中有94隻重複出現於樣區,有些個體棲息在樣區至少有三至四個月。白色個體間的結群模式顯著為非隨機的狀態,且結群強度較強。相反的,灰色個體的結群模式為隨機狀態且結群強度較弱。先前的文獻與本研究均推測白色的瑞氏海豚可能為雄性,灰色的瑞氏海豚則可能為雌性,此推測值得進一步的研究。 In order to research the distribution and social organization of Risso's dolphins (Grampus griseus) in the central-eastern waters off Taiwan, a photo-identification survey was conducted in the waters near Shir-ti, Hualien, during the periods from April to September 2001 and 2002. Observations were not conducted during winter due to the rough sea state. Data regarding group size and composition was used to analyze time-scale and space-scale distribution. Photos obtained in 2001 were used to identify individuals by their dorsal fins. Half-weight index and the SOCPROG program were used to analyze association patterns of resighted animals. A total of 204 groups of Risso's dolphins were observed. Group sizes in summer were significantly larger than in spring and fall. This suggested a higher summer abundance of Risso's dolphins in the study area. This seasonal increase might correspond to an increase in summer prey, Sthenoteuthis oualaniensis. Sightings of Risso's dolphins were significantly higher in 500 - 1500 m water depth. A shoreward movement from spring to fall was also observed. This seasonal switch in habitat might correspond to a high winter abundance of its predominant winter-prey, Enoploteuthis chunii, in the nearshore water of the study area. The group compositions of Risso's dolphins were categorized into 4 groups based on the skin color patterns and presence of calves: grayish-adult, whitish-adult, mixed, and calving groups. Except for grayish-adult groups, the sizes of the other three groups were significantly correlated with the daylight hours of 10:00 to 18:00, with group size increasing from noon to dusk. Sightings of large schools containing 120 to 200 animals were significantly greater in the afternoon. This phenomenon could be related to the nocturnal feeding habits of Risso's dolphins. The large schools might be feeding aggregations. Sightings of calves were highest in summer and fall. Courting behaviors occurred more often in spring and summer and were often observed in the mixed groups. This finding suggests that the function of mixed groups might be related to courtship. Summer might be an important mating season because the occurrence of mixed groups peaked in this season. At least 670 individuals were identified and of these, 94 animals were resighted in 2001. Some of the resighted individuals inhabited the study area for at least 3-4 months. Whitish adults showed significantly non-random and stronger association among whitish individuals, while grayish adults showed random association. Previous studies and this data suggest that whitish adults are likely males and grayish adults are likely females and this subject merits further investigation. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75366 |
全文授權: | 未授權 |
顯示於系所單位: | 動物學研究所 |
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