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Using stable isotopes of carbon and nitrogen to reveal the food sources of estuarine detritivorous fish
|關鍵字:||13C;13C;15N;Detrivore;Detritus food chain;Estuarine plants;Food source;Liza macrolepis;Stable isotope;Stomach content;15N;食碎屑者;碎屑食物鏈;河口植群;食物來源;大鱗鮻;穩定同位素;胃內容物||出版社:||植物學系||摘要:||
河口以碎屑食物網為主。為瞭解碎屑的來源以及對食碎屑魚類的重要性，於台灣西南沿海大鵬灣及北部關渡針對河口有機物質來源，包含維管束植物、附生藻類及漂浮性顆粒進行採樣，以台灣河口最常見之食碎屑魚種大鱗鮻（Liza macrolepis）為目標魚種，計算胃內含物的加權指數百分率來了解各類餌食在胃內含物中的重要性，並分析穩定性同位素13C和15N含量來追蹤這些食碎屑魚種之可能食物來源。由胃內含物分析結果得知，大鱗鮻胃內含物50 ％以上皆為碎屑，但無法辨識其來源，其餘則反映不同環境所含的不同植群，且容易因採樣時間與個體差異而有變異。關渡濕地之大鱗鮻胃內容物除碎屑外以維管束植物為優勢植群。而大鵬灣在胃內容物上，則由大型海藻與動物碎片或附生微藻取代維管束植物之地位。穩定同位素分析結果顯示，關渡地區附生微藻重要性高於維管束植物，大鵬灣則是大型藻類與附生微藻的重要性高於維管束植物。就目前所捕獲之體長範圍，相同地點的大鱗鮻並不會隨成長而改變碳來源，而是隨環境、季節改變食物組成比例。但體長小於40mm的魚體其氮源則有所變化。總結而言，附生藻類對食碎屑魚種的貢獻高於維管束植物，而與過去認為的紅樹林及草澤植物為河口生物有機碎屑食物主要來源的觀念有所差異。
The biomass, production and yield of fish in estuaries are often higher than those in other aquatic ecosystems. In order to understand the food and relative contribution of each primary producer to detritivorous fish, I collected the sources of estuarine organic matter, including vascular plants, periphyton, and seston, from Tapong Bay and Kuandu wetlands, respectively. I used detritivorous fish (Liza macrolepis) as a model fish to examine its stomach contents by evaluating the percentage of weighted point value and to trace its food sources by analyzing stable carbon and nitrogen isotopes ratio. The results from the examination of stomach contents revealed that more than 50% of the contents is detritus, which can not be identified its sources. In addition to the detritus, the stomach contents of L. macrolepis in Kuandu were dominated by vascular plants. In contrast, macroalgae and benthos or microalgae have replaced vascular plants in stomach contents of L. macrolepis in Tapong Bay. The results of stable isotope analysis showed that the contribution of microalgae to the food of the fish is more important than vascular plants in Kuandu. The contribution of microalgae and macroalgae is more important than vascular plants in Tapong Bay. In the size range of L. macrolepis, the organic carbon sources do not shift with size, but the ratio of food changes with environment and season. However, the nitrogen source is different changed in the fish whose size is less than 40mm. As a result, the contribution of periphyton to detritivorous fish is more important than vascular plants. These results were different from the paradigm that mangroves and salt marsh plants are the major food source for estuarine detritivorous fish.
|Appears in Collections:||生命科學系所|
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