New information on the concentrations of Cd, Cu, Hg and Zn in the liver, kidney and muscles of eight marine benthic and pelagic sub-Antarctic fish species are presented to determine the importance of these metals in the marine systems of the Kerguelen Islands. Compared to the reported metal concentrations in other Antarctic fish species, the present results are globally within the same range of concentrations, although Cd displayed a very high interspecific variability in liver and kidney. Indeed, the highest Cd concentrations in liver, ranging from 10.0 to 52.1 mg g dry y1 wt. but also the lowest Cd concentrations in muscles (-0.030 mg g dry wt.) have been displayed by the pelagic y1 Myctophidae Gymnoscopelus piabilis. Metal concentrations differences might be related to diet and feeding habits of benthic and pelagic fish species. However, Cd and Hg concentrations in the edible muscle are lower than the French limit values ((0.155 mg Cd g dry wt. and (1.51 mg Hg g dry wt.) for these toxic metals as well as for edible y1 y1and non-commercially interesting fish species. Results for Cd in fish tissues are consistent with the hypothesis of Cdenrichment in the polar food webs typically explained by essential elements depletion. In fact, Zn concentrations in fish from the Kerguelen Islands are comparable to those of other areas but low Cu concentrations in fish livers, ranging from 0.9 to 24.7 mg g dry wt., might indicate low availability of this essential element in these sub- y1Antarctic waters. ᮊ

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Numerous animals move vast distances through media with stochastic dynamic properties. Avian migrants must cope with variable wind speeds and directions en route, which potentially jeopardize fine-tuned migration routes and itineraries. We show how unpredictable winds affect flight times and the use of an intermediate staging site by red knots (Calidris canutus canutus) migrating from west Africa to the central north Siberian breeding areas via the German Wadden Sea. A dynamic migration model incorporating wind conditions during flight shows that flight durations between Mauritania and the Wadden Sea vary between 2 and 8 days. The number of birds counted at the only known intermediate staging site on the French Atlantic coast was strongly positively correlated with simulated flight times. In addition, particularly light-weight birds occurred at this location. These independent results support the idea that stochastic wind conditions are the main driver of the use of this intermediate stopover site as an emergency staging area. Because of the ubiquity of stochastically varying media, we expect such emergency habitats to exist in many other migratory systems, both airborne and oceanic. Our model provides a tool to quantify the effect of winds and currents en route.

ABSTRACT:The food and feeding ecology of the blue petrel Halobaena caerulea was investigated over 4 consecutive chick-rearing periods at Iles Kerguelen. In all years, blue petrels fed on a large diversity of crustaceans and fish, with a small proportion of squid and other organisms. Crustaceans ranked first by number (98%) and second by reconstituted mass (37%). The hyperiid Themisto gaudichaudii and the euphausiid Thysanoessa sp. were the dominant prey items, accounting each for 42% by number, and for 12 and 4% by mass of the diet, respectively. Other important crustacean prey were the Antarctic krill Euphausia superba (2% by number and 10% by mass) and the large shrimp Pasiphaea scotiae (<1 and 5%, respectively). Fish were minor items by number (<1%) but, owing to their large size, they dominated the diet by reconstituted mass (57%). Mesopelagic fish of the families Myctophidae (14% by mass) and Melamphaidae (12%) were the main fish prey together with the gempylid Paradiplospinus gracilis (19%). Adult blue petrels use a 2-fold foraging strategy, performing short trips (ST, 2 d on average) and long trips (LT, 7 d) during the chick-rearing period. Birds fed more on T. gaudichaudii during ST and more on Thysanoessa sp. during LT. The subantarctic krill Euphausia vallentini were found in ST samples, and Antarctic krill and stomach oil were found in LT samples. Biogeography of the prey shows that blue petrels fed in a wide variety of marine habitats. During ST, they foraged in the kelp belt and over the shelf, but favoured oceanic waters in the vicinity of the archipelago. During LT, the occurrence of Antarctic krill indicates feeding in southern Antarctic waters, >1000 km from the breeding colonies, but blue petrels also foraged on their way back to Iles Kerguelen from these distant foraging grounds to feed their chicks. A comparison of the stable carbon and nitrogen isotopic compositions of chick and adult feathers reveals that adult blue petrels fed at the same trophic level during the chick-rearing and moulting period, and that they renew their flight feathers in Antarctic waters. KEY WORDS: Euphausia superba · Mesopelagic fish · Seabirds · Stable carbon isotopes · Stable nitrogen isotopes · Themisto gaudichaudii · Thysanoessa Resale or republication not permitted without written consent of the publisher INTRODUCTIONThe blue petrel Halobaena caerulea is a small procellariiform species that is taxonomically closely related to the prions (genus Pachyptila). It is the sole member of the genus and inhabits the subantarctic and Antarctic zones of the Southern Ocean (Warham 1990). The species is circumpolar and nests colonially in burrows at 6 locations close to the Antarctic polar front. The main population of blue petrels is in the southern Indian Ocean and at Diego Ramirez (Chile) with smaller numbers at Macquarie and South Georgia (Marchant & Higgins 1990). At Iles Kerguelen, the species is numerous (100 000 to 200 000 pairs), and it breeds sympatrically with 3 different prion species: the fairy prion P. turtur a...