“Oceanographic habitats of southern rockhopper penguin (Eudyptes chrysocome chrysocome) from Staten Island during winter”

A RAYA REY; K PÜTZ; RAYA REY A

Ushuaia

Workshop; International Workshop “Interaction between Magellan Region and Antarctic; 2003

We characterized the movements and oceanographic habitats of southern rockhopper penguins during the winter dispersion. Also, we tried to highlight whether these species use predictable habitats, and if so, to define the factors influencing their marine distributions. Ten southern rockhopper penguins from Staten Island were fitted with platform terminal transmitters in March 2002, to determine foraging behaviour throughout the winter dispersion in relation to oceanographic data.   Analyses of satellite telemetry data in conjunction with remotely sensed sea surface temperature (SST) and bathymetry revealed two main foraging areas: one situated to the north of Staten Island off the coast of Tierra del Fuego and the other one to the south of Staten Island in the vicinity of the Antarctic Polar Front. Most of the birds commuted between the two zones. The area to the south of Staten Island seemed to be of particular importance for wintering rockhopper, because five out of nine birds initially headed towards it, and two other followed later in the season. However, rockhopper penguins from Staten Island did not leave their breeding colony in any preferred direction, since they headed, variously, northwest, northeast or south.   In the area to the north of Staten Island birds used shallow coastal waters characterized by predictable tidal fronts, which is a well-known highly productive region. Moreover, penguins spent 47% of their time at sea in those areas. By contrast, the area to the south included pelagic waters (> 3000m) and penguins spent 43% of their time in those waters. This area, in the region of the Drake Passage, included the Polar Frontal Zone (PFZ), an important water mass with high phytoplankton concentration, specially in its southern and northern limits (polar front PF and sub-Antarctic front SAF, respectively). Oceanic fronts were identified by sharp temperature gradients between water masses of 1.35º C. Penguins seemed to take advantage of those highly productive areas. The majority of them spent most of the time within the PFZ in water mass boundaries (eddies, fronts) that enhance water column mixing stimulate localized production, and aggregate planktonic prey at secondary convergence zones. Moreover, one of them at the beginning of its winter dispersion went directly to the southern boundary of the Antarctic Circumpolar Current, an extreme highly productive area. Another penguin followed the SAF during all its winter dispersion.   Water masses greater than 8ºc SST were preferred in March and April (along the Atlantic coast of Tierra del Fuego), but also in April two birds spent a large amount of time in waters less than –2 ºc (Antarctic waters), given a large percentage also to these water masses. From May to July penguins spent more than 50% of time in water masses between 4-6ºc (PFZ based on the published and widely used locations of water masses and fronts). However, when considering only the values of SST for the definition of water masses and fronts, the PFZ would be extending into the Patagonian shelf (specially during June and July). Although, this is unlikely due to bathymetry restrictions in this region of the Antarctic Circumpolar Current. This difficulty is overcome when gradients in SST are considered for defining fronts. Our analysis of fronts is consistent with the fact that the fronts and zones moves to the north during winter time, even though constrained by the restriction in the circumpolar circulation by the opening of the Drake Passage.   These results highlight the significance of macro-mega scales of (1000 to 3000 km) water mass distribution and smaller coarse-meso scale of (10 to 100 km) hydrographic processes for the winter dispersion of rockhopper penguins, and underscore the need to identify and understand how this oceanographic processes and features develop (specially during winter time).