Tactics and demographic attributes in the European eel Anguilla anguilla in the Gironde watershed, SW France
Tactics and demographic attributes in the European eel Anguilla anguilla in the Gironde watershed, SW France
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DOI：
10.3354/meps307247
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发表时间：
2006-01-01
影响因子：
2.5
通讯作者：
Tomás, J
中科院分区：
文献类型：
--
作者：
Daverat, F;Tomás, J
通过测定耳石中Sr和Ca的含量，研究了270尾欧洲鳗鲡（Anguilla anguilla）的栖息地利用模式及其相对比例。锶：钙值以外的幼鱼标志歧视居住在同一栖息地，直到捕获（淡水，河口，或海）从切换的栖息地以下3种模式：从淡水到河口，季节性运动的限制河口，或切换的栖息地从半咸水到淡水（下游游牧民族）。结果表明，居住梯度从淡水（100%），河口（44%），海洋（24%）。最丰富的（30%）替代居住在河口及其附近的沿海网站是下游游牧民族，这集中在沿海地区和河口的下部离开淡水后。总体而言，分析的鳗鱼中有50%在淡水中度过了一段时间。淡水中的鱼类生长率低于流域内的其他任何地方。对鱼的年龄大小的反算表明，在所有通过淡水的鳗鱼中，居民是缓慢的生长者，而下游的游牧民是快速的生长者。后者迁移到河口在年龄2+和3+，当他们的大小大于河口居民。结果显示，较低的河口和海洋栖息地的殖民地由黄色，而不是玻璃鳗鱼。这表明，与河口居民和下游游牧民族的竞争，防止过早定居的玻璃鳗鱼在河口和海洋栖息地。
The patterns of habitat use and their relative proportions were investigated for 270 eels Anguilla anguilla sampled in coastal areas, the estuary and the river of the Gironde watershed, by measuring Sr and Ca concentrations in the otolith. Sr:Ca values outside the elver mark discriminated residence in the same habitat until capture (freshwater, estuary, or sea) from a switch of habitat following 3 patterns: a shift from freshwater to estuarine, seasonal movements within the limits of the estuary, or a switch of habitat from brackish to freshwater (downstream nomads). Results show a gradient of residency from freshwater (100%) to estuary (44%) to the sea (24%). The most abundant (30%) alternative to residence in an estuary and its adjacent coastal site were the downstream nomads, which concentrated in coastal areas and the lower part of the estuary after leaving freshwater. Overall, tip to 50% of the eels analysed had spent a period in freshwater. Fish growth rates in freshwater were lower than anywhere else in the watershed. Back-calculation of fish size-at-age showed that, of all eels passing through freshwater, residents were slow growers, while downstream nomads were fast growers. The latter migrate to the estuary at Ages 2+ and 3+, when their size is greater than estuarine residents. Results revealed that lower estuarine and marine habitats are colonised by yellow rather than glass eels. This suggests that competition with estuarine residents and downstream nomads prevents precocious settlement of glass eels in estuary and marine habitats.