PHYSICAL AND BEHAVIORAL CONTROLS ON THE OCEANIC DISTRIBUTION AND MIGRATION OF LEPTOCEPHALI
PHYSICAL AND BEHAVIORAL CONTROLS ON THE OCEANIC DISTRIBUTION AND MIGRATION OF LEPTOCEPHALI
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DOI：
10.1111/j.1095-8649.1993.tb01191.x
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发表时间：
1993-12-01
影响因子：
2
通讯作者：
MCCLEAVE, JD
中科院分区：
文献类型：
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作者：
MCCLEAVE, JD
远洋的、长寿的细头鳗是鳗鱼家族中常见的，无论幼鳗生活在公海、陆架沃茨还是河口和淡水沃茨。成功的大陆物种的细头蚴必须离开开阔的海洋，而海洋物种的细头蚴必须避免来自开阔海洋的平流。迁徙物种的小头虫的迁移在概念上应被视为一个扩散死亡问题。根据小型（最近孵化的）leptocephali的分布，北大西洋西部的马尾藻海被确定为降河产卵的美洲和欧洲（angui llid）鳗鱼、西大西洋大陆架生活的Congereels以及许多海洋物种（如Nemichthys spectopaceus、Serri voiner beanii、Derichthys serpentinus和Nessorhamplms ingolfianus）的产卵区。在马尾藻海，副热带辐合带是一个狭窄的纬向带，北方和南方的热密度锋带出现，特别是在冬季。产卵的两个降河产卵鳗鱼和两个西部海鳗似乎是有限的南部带的前，南马尾藻海水发生的地区或南部。大多数海洋物种的产卵都发生在这些锋面的两侧。锋面区或南部沃茨的某些特征，如气味，可能作为一个信号，触发停止迁移和开始产卵的降河产卵鳗鱼。因此，这两种鳗的钩端螺旋体的来源可能是动物性的。由于水汇合成锋面，并导致向东的急流，锋面可能是许多大陆架栖息物种的一部分细头蚴的汇，这些细头蚴可能被平流输送离开合适的幼鱼栖息地。leptocephali的大小分布表明，在西南马尾藻海，安的列斯群岛电流，和佛罗里达电流巴哈马群岛北部的环流是出口的路线鳗和康格里德鳗鱼。较短的幼虫期和更北的产卵有利于保留海洋物种D。serpentinusandN，ingolfianusin the western Sargasso Sea.美洲鳗的leptocephalus阶段的持续时间比欧洲鳗短，美洲鳗和欧洲鳗leptocephali在变态前的时间长度具有可塑性，这使得大多数leptocephali在墨西哥湾流-北大西洋洋流系统上漂流到达适当的大陆。这个洋流系统确实可以运送这两个物种，但大多数美洲细头鳗只在西部发现，而欧洲细头鳗则遍布北大西洋洋流及其分支。欧洲大陆外从南到北的欧洲鳗leptocephali的长度逐渐增加，被用作证据，证明北大西洋洋流的漂移不是运输机制，必须发生积极的游泳。最近的迹象表明，加那利盆地的水向北输送。马尾藻海的向东急流和太平洋盆地范围的向东逆流的证据导致了大西洋可能存在向东逆流的假设，这将是向欧洲漂移的第二条更南的路线。强有力的遗传证据表明，冰岛的欧洲鳗鱼中存在两种安圭拉的杂交种，这是一个悖论，因为连接马尾藻海和冰岛的独特水流的存在是非常有问题的。
A pelagic, long‐lived leptocephalus is common to families of eels, whether the juveniles inhabit the open ocean, shelf waters, or estuarine and fresh waters. Successful leptocephali of continental species must leave the open ocean, while those of oceanic species must avoid advection from the open ocean. The movements of leptocephali of migratory species should be considered conceptually as a dispersal‐mortality problem. On the basis of the distribution of small (recently hatched) leptocephali, the Sargasso Sea in the western North Atlantic Ocean is identified as a spawning area for the catadromous American and European (angui llid) eels, western Atlantic shelf‐dwellingCongereels, and numerous oceanic species, e.g.Nemichthys scolopaceus, Serri voiner beanii, Derichthys serpentinusandNessorhamplms ingolfianus. Within the Sargasso Sea, the Subtropical Convergence Zone is a narrow latitudinal zone where northern and southern bands of thermal density fronts occur, especially in winter. Spawning of the two catadromous eels and the two western conger eels seems to be limited to areas in or south of the southern band of fronts, where southern Sargasso Sea water occurs. Spawning of most of the oceanic species occurs on both sides of these fronts. Some feature of the frontal zone or the southern waters, such as odour, may serve as a signal to trigger cessation of migration and initiation of spawning in catadromous eels. Thus the source of leptocephali of the two species ofAnguillamay be zotially restricted. Because of confluence of water into fronts and resulting eastward jet‐like currents, fronts may be sinks for a portion of the leptocephali of numerous shelf‐dwelling species, which may be advected away from suitable juvenile habitat. The size distributions of leptocephali suggest that gyres in the southwestern Sargasso Sea, an Antilles Current, and the Florida Current north of the Bahamas are routes of exit for anguillid and congrid eels. Shorter larval duration and more northerly spawning facilitates retention of the oceanic speciesD. serpentinusandN, ingolfianusin the western Sargasso Sea. Shorter duration of the leptocephalus stage of the American eel than the European eel, and plasticity in length of time prior to metamorphosis in both American and European eel leptocephali cause most leptocephali drifting on the Gulf Stream‐North Atlantic Current system to arrive at the appropriate continent. This current system does transport both species, but most American eel leptocephali are found only in the west, while European eel leptocephali are found all across the North Atlantic current and its branches. A dine of increasing lengths of European eel leptocephali from south to north off the continent of Europe has been used as evidence that drift on the North Atlantic Current cannot be the transport mechanism and that active swimming must occur. Recent indications are that there is northward transport of water in the Canary Basin. Eastward jets in the Sargasso Sea and evidence for a basin‐wide eastward countercurrent in the Pacific Ocean lead to the hypothesis of a possible eastward countercurrent in the Atlantic that would be a second more southerly route of drift toward Europe. Strong genetic evidence shows the presence of hybrids of the twoAnguillaspecies among the mostly European eels in Iceland, presenting a paradox because the existence of unique currents connecting the Sargasso Sea and Iceland is highly problematic.