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Sexual dimorphism and natural movements of the American eel(Anguilla rostrata) in Rhode Island streams and estuaries
Geschlechtsdemorphismus und Wanderaktivität des Amerikanischen Aales(Anguilla rostrata) in Fließgewässern und Flußmündungen von Rhode Island
Helgoländer wissenschaftliche Meeresuntersuchungen volume 27, pages 156–166 (1975)
Kurzfassung
Der Augendurchmesser männlicher Amerikanischer Blankaale(Anguilla rostrata) war beträchtlich größer als derjenige von Amerikanischen Gelbaalen. Blankaalmännchen hatten eine wesentlich geringere Durchschnittslänge als Blankaalweibchen. In kleinen Fließgewässern dominierten die Männchen, in Flußmündungen war der Weibchenanteil vergleichsweise größer. Die Abwanderung ins Meer fand hauptsächlich während der Monate September bis November statt und war verstärkt bei nennenswerten Regenfällen sowie während des dritten und vierten Mondviertels. Die Untersuchungen erbrachten in vieler Hinsicht ähnliche Ergebnisse, wie sie vom Europäischen Aal bekannt sind. Es wird angenommen, daß hinsichtlich der Stimuli für Beginn und Aufrechterhaltung der Laichwanderung eine große Zahl von funktionellen Sicherungen vorhanden ist, welche die Vermehrung gewährleisten.
Summary
1. The eyes of silver males were much enlarged, but not thoses of femaleAnguilla rostrata specimens.
2. Silver males were smaller than silver females.
3. Males predominated in freshwater and the proportion of females increased in estuaries.
4. In trap catches from 1969 to 1972, most silver eel runs occurred from September through November and came after rains or in the third and fourth lunar quarters. More yellow eels are also caught at this time.
5. Based on records from an electronic fish counter, silver eels moved primarily from just after sundown to 2300 hr.
6. It is suggested that with regard to stimuli initiating migration, a great deal of redundancy is built into the system so that reproduction is assured.
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Winn, H.E., Richkus, W.A. & Winn, L.K. Sexual dimorphism and natural movements of the American eel(Anguilla rostrata) in Rhode Island streams and estuaries. Helgolander Wiss. Meeresunters 27, 156–166 (1975). https://doi.org/10.1007/BF01611803
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DOI: https://doi.org/10.1007/BF01611803