한국 근해 고래류의 섭식 생태 이해를 위한 생화학적 방법의 활용

Abstract

In order to understand the feeding ecology of three cetaceans (minke whale, long-beaked common dolphin and Pacific white-sided dolphin), lipid contents and composition with stable isotope were examined in their blubbers and 16 potential prey species. The stratification of lipid content appeared with the increase from the inner layer to the outer layer in the blubber of all three cetaceans, although total lipid content in the blubber of minke whale was a significant difference with by-catch date and region. FA composition of the blubber of all three cetaceans was stratified with a higher level of monounsaturated FAs (14 to 18 carbons) in the outer layer and a higher level of saturated FAs and polyunsaturated FAs in the inner layer. FA composition in the inner layer related with the diets differed substantially to potential prey species, whereas stable isotope values of cetaceans and potential prey species provided the information on the origin of carbon and trophic level. Also, it was confirmed through stable isotope values that Pacific white-sided dolphin was the highest trophic level among three cetaceans. However, it was difficult to track the preferential preys of three cetaceans using only FA composition and bulk stable isotope ratios. Because lipid components in the blubber were mainly modified through the vertical layers of the blubbers, the additional analysis of compound-specific stable isotope in the cetaceans and potential prey species could help to understand not only lipid metabolism but also the feeding ecology of cetaceans.|한국 근해에 서식하는 고래의 먹이 생태를 이해하기 위해 2002년부터 2009년까지 동해에서 혼획된 밍크고래 (Balaenoptera acutorostrata), 참돌고래 (Delphinus capensis), 낫돌고래 (Lagenorhynchus obiquidens) 피하지방층과 먹이생물의 지방 및 안정동위원소비를 분석하였다. 모든 피하지방층 시료의 지방은 대부분이 트리아실글리세롤로 구성되어 있었으며, 외층이 내층에 비해 지방 함량이 더 높았다. 피하지방의 지방산 성분 중에서는 18:1(n-9)과 16:1(n-7)을 포함한 단일불포화지방산 (monounsaturated fatty acid) 이 모든 시료에서 가장 많았으며, 특히 탄소 14~18개의 단일불포화지방산은 내층에서 외층으로 갈수록 증가하였다. 그러나 긴 사슬 불포화지방산 (polyunsaturated fatty acid) 과 포화지방산 (saturated fatty acid) 은 내층에서 외층으로 갈수록 감소하였다. 이러한 피하지방층별 지방 함량 및 지방산 구성의 차이는 피하지방층에 따른 지방의 기능과 역할 (내층: 에너지 저장, 외층: 보온 및 부력) 이 다르기 때문인 것으로 보인다. 이와 더불어 해양생태계에서 고래의 영양학적 위치를 비교하기 위해 고래 피부의 탄소, 질소 안정동위원소비를 분석한 결과, 밍크고래와 참돌고래는 유사한 영양학적 위치에 있었으며, 낫돌고래는 밍크고래와 참돌고래에 비해 더 상위의 먹이를 섭식하는 것으로 나타났다. 그러나 지방과 안정동위원소를 통한 고래의 먹이 생태를 확인하기는 어려웠다. 피하지방층 내에서 지방은 생리, 생태적인 요인에 의해 변형되기 때문에, 고래의 먹이생태와 지방 대사작용을 이해하기 위하여 추가적으로 고래와 먹이생물의 각 지방산 안정동위원소비 분석이 유용하게 활용될 수 있을 것이다.; In order to understand the feeding ecology of three cetaceans (minke whale, long-beaked common dolphin and Pacific white-sided dolphin), lipid contents and composition with stable isotope were examined in their blubbers and 16 potential prey species. The stratification of lipid content appeared with the increase from the inner layer to the outer layer in the blubber of all three cetaceans, although total lipid content in the blubber of minke whale was a significant difference with by-catch date and region. FA composition of the blubber of all three cetaceans was stratified with a higher level of monounsaturated FAs (14 to 18 carbons) in the outer layer and a higher level of saturated FAs and polyunsaturated FAs in the inner layer. FA composition in the inner layer related with the diets differed substantially to potential prey species, whereas stable isotope values of cetaceans and potential prey species provided the information on the origin of carbon and trophic level. Also, it was confirmed through stable isotope values that Pacific white-sided dolphin was the highest trophic level among three cetaceans. However, it was difficult to track the preferential preys of three cetaceans using only FA composition and bulk stable isotope ratios. Because lipid components in the blubber were mainly modified through the vertical layers of the blubbers, the additional analysis of compound-specific stable isotope in the cetaceans and potential prey species could help to understand not only lipid metabolism but also the feeding ecology of cetaceans.