A Study of a Conservation and Management Plan for Natural Monument No. 27 Jeju Anguilla marmorata via Landscape Analysis and Food Source Analysis

서지정보

· 발행기관 : 한국전통조경학회
· 수록지 정보 : 한국전통조경학회지 / 18권 / 28 ~ 41페이지
· 저자명 : 이성경, 정상우, 손석준, 황호성, 김창현, 오정우, 현보라, 김동현, 민홍기, 조성호, 강정훈, 변성훈, 한정호

초록

This study aimed to provide basic data for preserving the Anguilla marmorata habitat by surveying the fish status of Cheonjiyeon Waterfalls, which is the designated habitat of the A. marmorata, and by identifying the habitat environment and food source of the A. marmorata. Fish surveys were conducted in Yeonoe and Jungmun Stream from July 2019 to October 2020. The survey showed that cliffs, waterfalls, spring water, and water-based tuff layers form a geotope in the A. marmorata habitat region, while the Cheonjiyeon warm temperate forest and elaeocarpus, rare plants and subtropical southern province evergreen forest, the A. marmorata habitat, and the Yeonoe Stream and Seohongcheon are all components of the biotope. In addition, the geographic names and legends related to the landscape of Cheonjiyeon Waterfalls are transmitted, and the waterfall, topographical landscape, river landscape, and evergreen forest form the anthropotope as visual elements.
A total of five A. marmorata were captured at Cheonjiyeon Waterfalls, and the habitat could not be confirmed in Jungmun Stream, which was the control group stream. In Jungmun Stream, where Cheonjeyeon Waterfalls three is located, there are a total of two artificial prairies; whereas, there are a total of five artificial weirs in Yeonoe Stream, indicating that Yeonoe Stream has more obstacles that may decrease the rate of fish ascending upstream. Analysis of the physico-chemical water quality characteristics showed that the water temperature was 15.8-17.9°C in Yeonoe Stream and 15.8-17.8°C in Jungmun Stream.
Unlike in the general stream, there was little change in water temperature due to seasonal differences, and dissolved oxygen (DO) levels were 7.11 and 9.88mgL-1 in Jungmun Stream and Yeonoe Stream, respectively. Both streams had the correct conditions to support A. marmorata. In the fish survey, in the lower part of Cheonjiyeon Waterfalls where the A. marmorata inhabits, there are abundant fishes(Rhynchocypris oxycephalus, Rhinogobius giurinus) for A. marmorata to consume, but the emergence rate upstream is very low. Therefore, we determined that the fish food sources were insufficient to support A. marmorata.
In the length-weight relationship, the b value of the regression coefficient that can determine the nutritional level was 2.466 for Yeonoe Stream and 3.121 for Jungmun Stream. This meant that the Anguillidae captured in Yeonoe Stream had poorer nutritional conditions than those from Jungmun Stream. In addition, study of the distribution of benthic macroinvertebrates, the main food sources of the A. marmorata, identified 20 species in Yeonoe Stream, accounting for 46% of the total species in Jeju Island, while 39 species were found in Jungmun Stream, accounting for about 90% of all species. It was found that benthic macroinvertebrates, the main source of food for A. marmorata, were significantly less abundant in Yeonoe Stream.
This result could be explained by the five artificial weirs between Yeonoe Stream to the Cheonjiyeon Waterfalls, the habitat for A. marmorata, which prevents fishes from ascending upstream. In particular, due to the dredging conducted in 2017, disturbances in riverbed structure are believed to have made it difficult for benthic macroinvertebrates to inhabit the area, leading to insufficient food source phenomena.
Therefore, Cheonjiyeon Waterfalls, which is South Korea's only habitat for the A. marmorata, must be preserved. To allow an increase in the A. marmorata population and their sustainable survival, Cheonjiyeon Waterfalls must be always connected to the sea by removing the artificial weirs or by installing fishways in the weirs that are located upstream, as the A. marmorata must move to the sea for spawning and return to the mother stream for growth. Moreover, efforts should be made to create a variety of habitat environments such as large stones, sand, and prairies so that food sources such as shrimp and aquatic insects can be secured. In particular, dredging and river maintenance work performed for aesthetic reasons should be prevented, and long-term countermeasures are necessary for the continuous conservation of natural monument habitats.

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