Diving behaviour of albatrosses: implications for foraging ecology and bycatch susceptibility
Résumé
Diving is an ecologically important behaviour that provides air-breathing predators with opportunities to capture prey, but
that also increases their exposure to incidental mortality (bycatch) in commercial fisheries. In this study, we characterised
the diving behaviour of 26 individuals of three species, the black-browed albatross Thalassarche melanophris, grey-headed
albatross T. chrysostoma and light-mantled albatross Phoebetria palpebrata, breeding at Bird Island, South Georgia. Individuals
were tracked using Global Location Sensor (GLS)-immersion loggers and time-depth recorders (TDRs) and, for two
species, Global Positioning System (GPS) loggers. Although the TDRs recorded 589 dives (defined in this paper as submersion
> 1 m), average dive depths and durations were just 1.30–1.49 m and 2.5–3.3 s, respectively, for the three species. In
addition, many individuals (22% of black-browed, 20% of grey-headed, and 57% of light-mantled albatrosses; total n = 9, 10
and 7 individuals, respectively) did not dive at all. Most dives occurred at the distal end of foraging trips and were rare during
the commuting phase. No dives took place in darkness, despite long periods spent on water at night. The limited and shallow
dive activity contrasts with impressions from a previous study using capillary-tube depth gauges (which are less accurate
than TDRs) and has implications for the susceptibility of albatrosses to bycatch on longlines. This study provides further
support for regulations requiring night setting and increased sink rates of baited hooks to help mitigate albatross bycatch.
Domaines
Sciences de l'environnementOrigine | Fichiers produits par l'(les) auteur(s) |
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