Abstract
摘要:東海涵蓋西北太平洋範圍最大的陸棚區域,根據漁業統計,中國大陸超過40%的漁獲量都是來自此海域,再者東海也是臺灣東北沿近海非常重要的漁場。然而東海的漁業資源從1980年代便逐年減少,主要的原因與過渡漁業捕撈以及環境破壞有關。長江沖淡水攜帶大量的營養鹽進入東海,並且造成基礎生產力升高。理論上,高基礎生產力應該可以藉由食物鏈傳遞到人類能夠利用的較高食物鏈階層,並且增加漁產量,但是過多營養鹽(優氧化)也會導致異營性細菌生長,大量消耗氧氣,而致使大部份的底棲生物無法生存。上述這些因子如何影響東海底棲性生物,包括魚類,到目前為止還是所知有限,因此對於該海域的海洋生態運作機制必須深入探討,才能有效恢復東海海洋生態系統以及讓漁業資源達到永續利用。
本研究的目的在於瞭解營養鹽濃度與海洋生態系結構的關係。底棲性魚類一生通常都棲息於特定範圍內,很少進行長距離遷徙,因此底棲性魚群聚結構深受該海域的水文特性影響。我們將收集並分析相關的底棲性魚類的生物資料,如豐富度,生物多樣性與均勻度,並且與海洋環境資料進行分析,以瞭解該海域的底棲性魚類如何受到環境因子的影響與限制。另外,本研究也會發展穩定性同位素的方法,以瞭解該海域的生地化作用機制,藉由分析底棲性魚類的肌肉組織中穩定性碳氮同位素組成,並且配合其他相關的生物與環境資料,我們將從無機營養鹽,初級生產者到高級消費者的食階作用過程,進一步解析東海生態系統的動態變化,例如優氧化,與海洋底棲性魚類群聚的關連性。
Abstract: The East China Sea (ECS) covers an extensive continental shelf in the northwestern Pacific and provides more than 40% of the total marine catch of China. The ECS also provides very important fishing grounds for Taiwan neritic and offshore fisheries. The fishery resource of the ECS has decreased significantly since the 1980’s, due to intensive exploitation and habitat degradation. The Chang-Jiang River discharges bring rich nutrients into the ECS and subsequently promote a high primary productivity, which theoretically can enrich fishery production by the transfer of energy and material through the food web. However, excessive nutrient input, such as anthropogenic pollution, may cause eutrophication and degrade the marine habitat. The natural and anthropogenic factors that may affect the demersal fish community are still largely unknown in the ECS. These basic ecological processes deserve further investigation and study in order to determine what actions to take to effectively restore the marine ecosystem and subsequently to enhance fishery production to a sustainable level.
The aim of this study is to evaluate the relationship between nutrient levels and marine community structure (eutrophic, mesotrophic and oligotrophic) in the ECS, mainly focusing on the demersal fish community. Demersal fish usually stay within a relatively limited area and most do not make large-scale migrations. Therefore, the community of demersal fishes will be deeply influenced by local oceanographic conditions. The biological data for biodiversity, evenness, biomass and abundance will be also analyzed. Environmental factors, including the levels of various nutrients, oxygen levels and primary production, will be also measured and collected during the same cruise by other researchers. The biological and environmental data will be analyzed to clarify their interactions. We will also develop a stable isotope technique to study the biogeochemical process for different marine ecosystem statuses. The isotopic composition of carbon and nitrogen in marine organic materials provides a method to investigate marine ecosystem response to environmental change. By analyzing the isotope composition of demersal fish tissues collected from different environmental conditions, we will be able to evaluate the responses of the fish community to environmental changes e.g., eutrophication.
The results of this study will permit us to better understand the dynamic variation within trophic levels in the ECS ecosystem from inorganic nutrients, to primary production and to consumers at higher trophic levels. More specifically, studying the stable isotope composition of the demersal fish community will enable us to better understand the interactions and responses of the demersal fish community to environmental change, especially in continental shelf areas which are largely disturbed by anthropogenic activities.
Keyword(s)
底棲魚類
海洋群聚
環境變遷
Demersal Fish
Marine Community
Environmental Changes