title: Spawning behaviour of Allis shad Alosa alosa: new insights based on imaging sonar data.
abstract: Spawning behaviour of Alosa alosa was observed by high resolution imaging sonar. Detected clouds of sexual products and micro bubbles served as a potential indicator of spawning activity. Peak spawning time was between 0130 and 0200 hours at night. Increasing detections over three consecutive nights were consistent with sounds of mating events (bulls) assessed in hearing surveys in parallel to the hydro acoustic detection. In 70% of the analysed mating events there were no additional A. alosa joining the event whilst 70% of the mating events showed one or two A. alosa leaving the cloud. In 31% of the analysed mating events, however, three or more A. alosa were leaving the clouds, indicating that matings are not restricted to a pair. Imaging sonar is suitable for monitoring spawning activity and behaviour of anadromous clupeids in their spawning habitats.
authors.affiliation: Institute of Zoology, University of Cologne, Ecological Research Station Grietherbusch, 50674, Cologne, Germany.|LFV Hydroakustik GmbH, 48159, Münster, Germany.
authors.forename: M C
authors.initials: MC
authors.lastname: Langkau
authors.affiliation: Association MI.GA.DO., 47520, Le Passage d'Agen, France.
authors.forename: D
authors.initials: D
authors.lastname: Clavé
authors.affiliation: LFV Hydroakustik GmbH, 48159, Münster, Germany.|Landesfischereiverband Westfalen und Lippe e.V., 48159, Münster, Germany.
authors.forename: M B
authors.initials: MB
authors.lastname: Schmidt
authors.affiliation: Institute of Zoology, University of Cologne, Ecological Research Station Grietherbusch, 50674, Cologne, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Borcherding
mesh_terms: D000162:Acoustics; D000819:Animal Communication; D025041:Animal Migration; D000818:Animals; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D008297:Male; D012098:Reproduction; D012726:Sexual Behavior, Animal
keywords: DIDSON; bull; hydro acoustic; mating; spawning activity