利用耳石元素組成和標識放流實驗研究日本鰻在河川內的洄游環境史及棲地利用特徵

Migratory environmental history and habitat use of Japanese eel Anguilla Japonica in the river as revealed by otolith elemental composition and mark-recapture experiment

林世寰(Shih-Huan Lin)

指導教授 ： 曾萬年

共同指導教授 ： 韓玉山

國立臺灣大學/生命科學院/漁業科學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.00121

摘要

為了瞭解日本鰻在河川內的空間分布、移動行為以及棲地利用特徵，本研究從2002年至2006年，在台灣南部的高屏溪及大鵬灣，總計放流了3263尾標識的野生黃鰻及養殖的黃鰻和4800尾鰻線。一共用了五種不同的標識方法，包括 (1) 液態氮烙印鰻魚體表， (2) 剪鰭標識，(3) 氧化四環黴素 (OTC) 和茜素 (ALC) 螢光染劑標記耳石，(4) 動物晶片植入魚體，以及 (5) 微磁鐵金屬編碼標籤植入魚體。放流之後，從大鵬灣的3個測站和高屏溪的15個測站調查漁民每天利用蛇籠所漁獲的再捕鰻及天然鰻數量。同時也採取水樣測定環境因子。水樣和耳石的微量元素組成 (鍶鈣比：Sr/Ca、鋇鈣比：Ba/Ca) 和鍶同位素比 (87Sr/86Sr) 分別以感應耦合電漿質譜儀 (ICPMS)、電子微探儀 (EPMA) 和熱離子源質譜儀 (TIMS) 測定之。結果發現日本鰻進入河川後具有領域行為，放流後的鰻魚大都停留在2公里範圍內，較少有長距離的移動者，回收率會隨著時間的經過而驟降。從天然野生鰻及部分回收的標識鰻的耳石微化學及鍶同位素分析結果，發現天然鰻的洄游環境史的類型之比例以河口型 (高屏溪：75.5%；大鵬灣：60%) 較高，其次為淡水型 (高屏溪：22%；大鵬灣：25%)，海水型 (高屏溪：2.5%；大鵬灣：15%) 的比例較低。被捕獲的放流鰻的耳石Sr/Ca與天然鰻相似，顯示放流鰻也是喜好半淡鹹水的河口域。
耳石的87Sr/86Sr較Sr/Ca更敏感，可以進一步將Sr/Ca所呈現的淡水型細分為中游及下游的不同兩群。結合標識放流實驗及耳石元素組成，能進一步了解高屏溪日本鰻洄游行為和微棲地利用特徵。

關鍵字

日本鰻 ； 耳石微化學 ； 標識放流 ； 洄游行為 ； 棲地利用

並列摘要

To understand the distribution, migratory behaviors and habitats use characteristics of Japanese eels Anguilla japonica in the continental waters, 3263 wild and cultured-origin yellow eels and 4800 elvers were marked and released in the Kao-ping River estuary and Da-pong Bay in southwestern Taiwan over four years since 2003-2006. Five different tagging methods were used to mark the eel, including: (1) liquid nitrogen marking on the fish body surface, (2) fin clipped, (3) oxytetracycline and alizarin complexone marking on otoliths, (4) micro-chips, and (5) coded wire tags. The recapture of marked eels were monitored after release by local fisherman using the traditional shrimp net in the 3 stations in the Da-pong Bay and the 15 stations in the Kao-ping River. The chemical composition in water and otolith of the eel including strontium: calcium ratios (Sr/Ca), Barium: Ca ratios (Ba/Ca) and Sr isotope ratios (87Sr/86Sr) were measured by Inductively Coupled Plasma Mass Spectrometry (ICPMS), Electron Probe Micro Analyzer (EPMA) and Thermal Ionization Mass Spectrometry (TIMS), respectively. The recapture rate of marked eel sharply decreased with increasing distance from the released site and the maximum dispersal distance of the eel was less than 2 km, indicating that the eel may have a territorial behavior after recruitment to the river. The recapture rate also sharply decreased with time, indicating that heavy harvesting of the eel occurred over a short time after release. According to the level of otolith Sr/Ca ratios of the wild eel, it revealed that estuarine contingents (river: 75.5%, bay: 60%) were higher than freshwater contingents (river: 22%, bay: 25%) and seawater contingents (river: 2.5%, bay: 15%). The otolith Sr/Ca ratios of recaptured eels indicated that the marked eels also preferred a brackish environment similar to wild population.
The otolith Sr isotope ratios are more sensitive than Sr/Ca ratios which could separate freshwater contingents into lower reach and middle reach groups. The combination of mark-recapture methods and otolith chemical composition can look insight into migratory behavior and micro habitats use of the eels in continental waters.

並列關鍵字

Anguilla japonica ； otolith microchemistry ； mark-recapture ； migratory behavior ； habitat use

參考文獻

Lin YJ, Tzeng WN (2008) Effects of shrimp net and cultured eels on the wild population of Japanese eel Anguilla japonica in Kao-Ping River, Taiwan. Journal of Fisheries Society Taiwan 35 (1): 61-73.

鍾小良 (2002) 二仁溪河水地球化學和同位素初探。國立成功大學地球科學研究所碩士論文。

Aarestrup K, Okland F, Hansen MM, Righton D, Gargan P, Castonguay M, Bernatchez L, Howey P, Sparholt H, Pedersen MI, McKinley RS (2009) Oceanic spawning migration of the European eel (Anguilla anguilla). Sci. 325: 1660 pp.

Aberg G (1995) The use of natural strontium isotopes as tracers in environmental studies. Water Air Soil Pollut. 79: 309-322.

Arai T, Limbong D, Tsukamoto K (2000) Validation of otolith daily increments in the tropical eel Anguilla celebesensis. Can. J. Zool. 78: 1078-1084