Diel feeding periodicity, daily ration and relative food consumption in some fish populations in three reservoirs of Sri Lanka Auteur(s) : Weliange, Wasantha S. Amarasinghe, Upali S. Moreau, Jacques Villanueva, Ching-maria Éditeur(s) : EDP Sciences Résumé : Twelve diel surveys were carried out in three reservoirs of Sri Lanka viz. Minneriya, Udawalawe and Victoria, to investigate diel feeding patterns, daily ration and relative food consumption in fish populations. Stomach content weights of different size classes of various fish species in the three reservoirs in 12 diel surveys were analysed using an iterative method, MAXIMS. Predominantly herbivorous or detritivorous fish species such as Amblypharyngodon melettinus and Oreochromis niloticus exhibited one peak in the diel feeding pattern. Two peak feeding periods were evident in predominantly insectivores and/or zooplanktivores (e. g., Puntius chola and Rasbora daniconius) and interestingly in macrophyte feeders (i.e., Etroplus suratensis, Puntius filamentosus and Tilapia rendalli). It might be possible that all species with two feeding peaks in diel feeding patterns rely on vision for feeding. Food consumption per biomass (Q/B ratio) defined as amount of food consumed per unit weight of an age-structured population of fish was estimated on the basis of the average quantities of food consumed over a long period of time by various size classes in order to minimize the bias of estimates. Douze séries d'échantillonnage ont été effectuées dans trois lacs-réservoirs du Sri Lanka : Minneriya, Udawalawe et Victoria, afin d'étudier le modèle journalier d'alimentation, les rations journalières et à la consommation relative des populations de poissons. Les poids des contenus stomacaux de différentes classes de taille ont ainsi été analysés en utilisant une méthode itérative, MAXIMS. Les espèces herbivores ou détritivores telles que Amblypharyngodon melettinus et Oreochromis niloticus montrent un pic dans l'activité de nutrition. Tandis que les espèces détrivores et/ou zooplanctivores en présentent deux (ex., Puntius chola et Rasbora daniconius) de même que des espèces se nourrissant de macrophytes (ex., Etroplus suratensis, Puntius filamentosus et Tilapia rendalli). Il est possible que la vision joue un rôle chez ces espèces présentant deux pics journaliers d'alimentation. La consommation de nourriture par rapport à la biomasse (le rapport Q/B) est défini comme la quantité d'aliment consommé par unité de poids d'une population de poissons structurée en âge, sur la base de quantités moyennes de nourriture consommée sur une longue période de temps et par diverses classes de taille, afin de minimiser les biais dans les estimations. Aquatic Living Resources (0990-7440) (EDP Sciences), 2006-07 , Vol. 19 , N. 3 , P. 229-237 Droits : 2006 EDP http://archimer.ifremer.fr/doc/2006/publication-2134.pdf DOI:10.1051/alr:2006023 http://archimer.ifremer.fr/doc/00000/2134/ | Partager Voir aussi Cichlidae Cyprinidae Trophic modelling Freshwater fish Feeding chronology Diel feeding pattern Télécharger |
Foraging of the green sea turtle Chelonia mydas on seagrass beds at Mayotte Island (Indian Ocean), determined by acoustic transmitters Auteur(s) : Taquet, Coralie Taquet, Marc Dempster, T Soria, M Ciccione, S Roos, David Dagorn, L Éditeur(s) : Inter-Research Résumé : We studied the foraging rhythms of green sea turtles Chelonia mydas on the seagrass beds of N'Gouja Bay, Mayotte Island (Comoros Archipelago) with acoustic transmitters and moored listening stations. We monitored 8 tagged turtles (4 probable males, 3 probable females and 1 immature), from 70 to 109 cm curved carapace length (CCL), for durations ranging from 5 to 92 d. The turtles exhibited a regular diel pattern: they foraged mainly during the day (on average 87% of seagrass detections were between 06:00 and 18:00 h) and rested on the inner reef slope during the night. Night time feeding activities were observed on the seagrass bed when the night light was high. The presence of turtles on the seagrass bed at night was significantly correlated with a night light index (r = 0.54, p = 0.002), which included both moon light and cloudiness indices. Behaviour of the only immature individual observed was similar to adult turtles, although it rested more frequently around noon. All turtles displayed a high fidelity to 1 foraging site within the seagrass bed. Acoustic transmitters and permanent listening stations are an appropriate technique for long-term behavioural studies of turtles, with no human interaction with turtles during tracking, and represent a suitable technique to assess the possible effects of environmental changes or human activities upon green turtle behaviour. Marine Ecology Progress Series (0171-8630) (Inter-Research), 2006 , Vol. 306 , P. 295-302 Droits : Inter-Research 2006 http://archimer.ifremer.fr/doc/2006/publication-3616.pdf DOI:10.3354/meps306295 http://archimer.ifremer.fr/doc/00000/3616/ | Partager Voir aussi Foraging rhythm Listening station Acoustic transmitter Green sea turtle Mayotte Southwestern Indian Ocean Chelonia mydas Télécharger |