Krill (Euphausia superba) abundance and Adélie penguin (Pygoscelis adeliae) breeding performance in the waters off the Béchervaise Island colony, East Antarctica in two years with contrasting ecological conditions.
S. Nicol1*, J. Clarke1, S.J. Romaine2, S. Kawaguchi1, G. Williams3, G. W. Hosie1
1 Australian Antarctic Division, Department of Environment and Heritage, Channel Highway, Kingston 7050, TAS, Australia.
2 Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, B.C., V8L 4B2. Canada.
* Primary Correspondence: Steve.Nicol@aad.gov.au
In 2001 and 2003 small-scale acoustic surveys of Antarctic krill (Euphausia superba) distribution and abundance were conducted offshore from a colony of Adélie penguins that has been monitored for 15 years. Although the distribution of krill was similar between the two summers, their abundance in 2001 was estimated to be three times higher than in 2003. This biomass difference was reflected in the breeding performance of the penguins at the monitored colony. Penguin parameters that showed significant differences between the two seasons included: foraging trip duration during chick rearing, breeding success, meal mass and dietary composition. Penguins travelled further to forage in 2003 than 2001, stayed away longer and brought back smaller meals. Fish (mostly Pleuragramma antarcticum) contributed significantly to the diet in 2003 but was only a minor component in 2001. Differences between years were particularly apparent during the late guard to early crèche stages of chick rearing, coinciding with the timing of the krill survey. Chick mortality peaked during this period also. Krill demographics and population processes showed little difference between the two years; however, the physical environment appeared to be significantly different. Relative to 2001 the surface mixed layer was colder, fresher and less developed (i.e. shallower) in 2003, indicative of a seasonal lag in the break-out and melting of sea-ice in this region. Satellite observations showed that winter fast-ice along the Mawson coast broke out in early January in 2001 but persisted for several weeks longer in 2003
04/30/07: Received final version with U.S. GLOBEC contribution number assigned (532).