La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Fisheries and daily activity cycles of Audouin's Larus audouinii and Yellow-legged Gulls L.cachinnans breeding at the Chafarinas Islands (Moroccan coast)
Auteurs :	Jacob González-Solís, Auteur ; Xavier Ruiz, Auteur ; Lluis Jover, Auteur
Type de document :	Article
Dans :	Vogelwarte (40(1-2) Oct., 1999)
Article en page(s) :	52-56
Langues:	Allemand
Résumé :	From 1993 to 1995 we analysed the influence of purse-seine and trawler fisheries on the activity cycle of Audouin's Larus audouinii and Yellow-legged Gull L.cachinnans at the Chafarinas Islands (Moroccan coast). Yellow-legged Gulls showed an activity cycle mainly diurnal. However, they take advantage of the fish attracted to the surface by purse-seine boats during the night and dawn. Purse-seine fisheries use powerful lamps that aid the gulls in localizing and exploiting schools of fish concentrated around lamps. Audouin's gull did not show any activity peak either during the day or at night. Although Audouin's Gulls showed conspicuous activity peaks depending on the trawler time-table in other colonies, the difficulty of predicting trawling fishery discards at Chafarinas Islands probably underlies the absence of clear peaks of activity linked to this fishery. Data suggest that parents foraged and relieved each other continuously. The capacity to maintain a continuous trophic activity, day and night, could be an additional advantage when the energetic costs increase during the reproductive period.

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