This study investigated the level of seabird mortality caused by the domestic trawl fleet (freshies) for hake (among other less important targets) operating in waters off central Patagonia (37-481S), analyzing the effect of environmental and operational variability on the level of seabird interactions. With a total of 135 vessels, the fleet is one of the largest in Argentina. Specifically tasked seabird observers were placed onboard trawlers during the summer and winter seasons of the years 2006 and 2007. The type and number of seabird interactions (i.e. contacts with fishing gear) were recorded during shooting and hauling operations, covering 72 days of observation and 328 trawls. Black-browed albatrosses, white-chinned petrels Procellaria aequinoctialis, southern giant petrels Marconectes giganteus and southern royal albatrosses Diomedea epomophora were the most abundant species interacting with trawlers. Confirmed mortalities of black-browed and southern royal albatrosses were the result of collisions and entanglement with the warp cable while birds were scavenging. The estimated total mortality rate was 0.017 birds h À1 and 0.105 birds per vessel per day. The intensity of interactions (in terms of the number of contacts per unit time) was largely explained by the distribution of the fishing effort. Seasonality and the incidence of discards were the strongest factors explaining the occurrence of seabird interactions. The total annual mortality in the trawl fleet under investigation was roughly estimated to be from several hundred to over a thousand albatrosses. However, these figures should be considered preliminary due to the limited spatial and temporal coverage of data and the fact that estimations were based on a low number of observed mortalities. The implementation of a strategic discard management may significantly reduce the number of seabird mortalities from collisions with warp cables or improve the effectiveness of other complementary mitigation methods. Urgent implementation of mitigation measures is needed in this fleet to reduce the mortality of albatrosses and petrels along the Patagonian shelf.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. University of California Press and CooperOrnithological Society are collaborating with JSTOR to digitize, preserve and extend access to The Condor. Abstract. We analyzed the effect of the shrimp fishery on Magellanic Penguins (Spheniscus magellanicus) in two ways: (1) we determined whether penguins were incidentally killed and the magnitude of incidental take, and (2) estimated the overlap between penguin diet and fish by-catch of the shrimp fishery (total capture excluding shrimp and seabirds). We worked with the fishing fleet operating at Golfo San Jorge with onboard observers over 200 days in 1995-1997, sampling fishery by-catch and entangled birds. Penguins were affected during the austral summer. Estimations of mortality rates showed 0.33% of the breeding population at Golfo San Jorge is incidentally killed by the shrimp fishery every summer. By-catch in shrimp fishery nets was composed of species important as penguin prey (anchovy and hake) in higher proportions during summer. The daily by-catch of these species was higher than the total calculated daily intake for all penguins breeding in the Golfo San Jorge. This could have a significant effect on birds. We recommend that an observer program be implemented to monitor seabird mortality and that fishing gear should be improved to reduce the indirect effect of the fish by-catch on penguins.

SummarySeabird colonies often constitute valuable tourist attractions. Different species differ in their sensitivity to human disturbance and, although birds may habituate to visitors, inappropriate intrusions at poorly managed sites may result in adverse effects on breeding individuals. The rapid growth of wildlife-based tourism and recreation in coastal Patagonia, Argentina, presents opportunities for significant economic benefits but also raises concerns about the potential effects on seabird colonies. Sixteen seabird species breed along the Patagonian coast, with Magellanic Penguin Spheniscus magellanicus being one of the main tourist attractions. At least 27 sites where seabirds breed are currently visited by people either through organized tourism or for recreational purposes, 19 of which are included in coastal protected areas. The number of visitors per year varies from 50 to more than 100,000, depending on the site. Negative effects on seabird reproduction in Patagonia are through direct destruction of nests or their contents and desertion of offspring, particularly at locations where seabirds nest in association with or near to colonies of avian predators. Tourism and recreation activities are growing in extent and intensity at most coastal sectors in Patagonia. Current trends in coastal recreation activities may result in negative effects on breeding seabirds unless management guidelines are developed and enforced. Information shows that tourism in coastal Patagonia is compatible with seabird conservation if appropriately managed. Given the rapid increase in the interest in visiting seabird colonies in Patagonia, several management tools such as sanctuaries, the limitation of visitor numbers and both temporal and spatial zoning, need to be implemented in the short term.

SummaryWe present information on the current population status of seabirds that breed along the Patagonian coast obtained between 1993 and 1995. A total of 16 species, including two penguins, one petrel, five cormorants, three gulls, three terns and two skuas, breed along the 3,400-km coast from southern Buenos Aires (38°58'S) to Tierra del Fuego (54°5o'S). Breeding seabirds are not as abundant in coastal Argentina as was previously thought. Eleven of the 16 species have less than 5,000 pairs. The most abundant seabird is the Magellanic Penguin Spheniscus magellanicus with 964,000 pairs, an order of magnitude higher than all other species. As well as Magellanic Penguins, Kelp Gulls Larus dominicanus, and Imperial Cormorants Phalacrocorax atriceps are relatively abundant and have a wide distribution. Other seabirds, such as Red-legged Cormorants P. gaimardi, Olrog's Gulls L. atlanticus, and Dolphin Gulls L. scoresbii, have a highly restricted distribution or nest in small colonies at a few sites in Argentina. The Patagonian coast is one of the most pristine coastal ecosystems in the world and, thus far, few seabirds are seriously threatened. However, oil pollution and commercial fisheries are having a negative impact on some seabirds and some colonies have shown recent declines. Current threats and impacts, including pollution, fisheries, human disturbance, guano harvesting, and introduction of alien species are discussed. There are currently 34 protected coastal areas, although in many cases protection measures are not adequately enforced and some areas with high seabird diversity and abundance still lack legal^and effective protection. Conservation actions and requirements, including direct actions, monitoring and research are suggested.

Radiotelemetry was used to assess the distribution and diving behaviour of Rock Shags Phalacrocorax magellanicus and Red‐legged Cormorants Phalacrocorax gaimardi breeding in sympatry, and Rock Shags breeding in isolation. When breeding in sympatry there was little overlap in the foraging locations of the two species, with the highest densities of each species separated by 10 km. Red‐legged Cormorants fed significantly closer to the breeding colony than did Rock Shags and undertook shorter foraging trips, making almost twice as many foraging trips per day as Rock Shags. Rock Shags breeding in isolation had a shorter foraging range than the birds breeding in sympatry with Red‐legged Cormorants and foraging trip duration was significantly shorter. However, the number of feeding trips per day was similar between areas of sympatry and allopatry. Differences in the foraging ecology of Rock Shags in areas of sympatry and allopatry may be due to interspecific competition, which forces niche differentiation. The distance between foraging sites, the speed of movement of the prey, a species tendency to move into prey‐depleted areas and the length of the breeding season (during which the birds are constrained to be in the same area) may play critical roles in determining the extent to which differential area use by competitors is a strategy that benefits both parties.

used stable isotope ratios of carbon and nitrogen in feather and bone to characterize the diet and foraging patterns of male and female penguins in the South atlantic at the beginning of the 2009-2010 and 2010-2011 post-breeding seasons (feathers) and over several consecutive breeding and migratory seasons (bone). The mean δ 13 C and δ 15 n values of feathers showed no differences between the sexes in any of the three regions considered or in the diet composition between the sexes from identical breeding regions; however, Bayesian ellipses showed a higher isotopic niche width in males at the beginning of the post-breeding season. Stable isotope ratios in bone revealed the enrichment of males with δ 13 C compared with females across the three regions considered. Furthermore, the Bayesian ellipses were larger for males and encompassed those of females in two of the three regions analyzed. These results suggest a differential use of winter resources between the sexes, with males typically showing a larger diversity of foraging/migratory strategies. The results also show that dietary differences between male and female Magellanic penguins may occur once the constraints imposed by chick rearing activities cease at the beginning of the post-breeding season. Communicated by S. garthe. l. Silva (*) • D. Vales • e. a. Crespo