Recursos Pelagicos

Montevideo, Uruguay

Recursos Pelagicos

Montevideo, Uruguay
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Passadore C.,University of the Republic of Uruguay | Passadore C.,Research Center y Conservacion Marina | Domingo A.,Recursos Pelagicos | Szephegyi M.,University of the Republic of Uruguay | Secchi E.R.,Grande Rio University
Journal of the Marine Biological Association of the United Kingdom | Year: 2014

Killer whale (Orcinus orca) is frequently encountered in coastal and high productive pelagic waters, near the shelf break. In the south-western Atlantic Ocean, spatial and temporal occurrence patterns are poorly known. However, the monitoring of the interaction between killer whales and longline fishery suggests that the species is frequent in this region. We analysed the killer whale presence within the Uruguayan pelagic longline fishing zone. Data were collected from 1996 to 2007, during 2189 fishing events, by vessel skippers and on-board observers. We estimated the sighting rate (SRÂ =Â sightings days/fishing days * 100) for different time scales and in 1 × 1 degree grids. Generalized linear models were used to evaluate the effect of spatial, temporal, environmental and operational variables on the species presence. Killer whales were sighted in 100 fishing days (SR = 4.5%), this occurrence being explained by distance from shore and sea surface temperature, varying among months and fishing boats. Although sightings occurred year round, they were more frequent in autumn and winter, at 150-400 nautical miles (nm) from shore (mean = 250 nm) and in waters with temperatures ranging from 19 to 24°C (mean = 22°C). Sets took place between 19°-40°S and 21°-54 °W, while killer whales occurred mostly from 34 °-37°S and 48°-53°W. In this region, the high productive Brazil-Malvinas Confluence Zone is located, and concentrates fishing effort and also killer whales. © 2012 Marine Biological Association of the United Kingdom .

Pons M.,Recursos Pelagicos | Pons M.,Research Center y Conservacion Marina | Domingo A.,Recursos Pelagicos | Domingo A.,Research Center y Conservacion Marina | And 6 more authors.
Aquatic Living Resources | Year: 2010

The population abundance estimates used in stock assessments or required to establish management measures, depend on the sampling of the entire demographic spectrum of a population resident in a given area. However, for sea turtles, most population estimates are based mainly on nesting beach survey data and only consider a fraction of the population. The Southwest Atlantic Ocean (SWA) is an important foraging and development area for juveniles of the loggerhead sea turtle Caretta caretta where reproductive stocks from various nesting beaches mix. Declines in C. caretta populations have been observed in many parts of the world and bycatch rates of this species in the SWA are among the highest worldwide. This study standardizes the catch rates of loggerheads caught by pelagic longline fisheries in the region, using data collected by observer programs from Brazil and Uruguay. Generalized linear models (GLM) with a delta lognormal approximation were used. The variables used in the model take into account spatial and temporal variations as well as the characteristics of the fleet. In total, 6 272 344 hooks were observed between 1998 and 2007, with minimum effort registered in 2000 (12 010 hooks) and maximum effort in 2005 (1 989 431 hooks). During this period 3778 loggerheads were incidentally captured. The catch rates of loggerheads by the Uruguayan and Brazilian pelagic longline fisheries show oscillations through the years without a clear tendency; however, a low negative trend was observed from 1998 to 2005 with an increase in the last two years (2006 and 2007). The capture per unit of effort (CPUE) values varied between 0.38 to 1.78 ind/1000 hooks in 2005 and 2007, respectively. Distinct zones with differential catch rates were identified, with the higher CPUE values over the continental slope of Uruguay and adjacent waters. The incidental catch rates of this species are influenced, not only by fishing area, but also by year, season, sea surface temperature and gear type. In consequence, these variables and other potential ones should be considered in bycatch estimates by different fisheries because the loggerhead sea turtles are not uniformly distributed. This study intends to contribute not only to the general knowledge of loggerhead sea turtles in the SWA but to a future assessment of their populations at a global scale. © 2010 EDP Sciences, IFREMER, IRD.

Jimenez S.,Recursos Pelagicos | Jimenez S.,Natural Environment Research Council | Jimenez S.,Research Center y Conservacion Marina | Domingo A.,Recursos Pelagicos | And 3 more authors.
Marine Pollution Bulletin | Year: 2015

Plastics and other marine debris affect wildlife through entanglement and by ingestion. We assessed the ingestion of marine debris by seven albatross species in the southwest Atlantic by analyzing stomach contents of birds killed in fisheries. Of the 128 specimens examined, including four Diomedea species (n = 78) and three Thalassarche species (n = 50), 21 (16.4%) contained 1-4 debris items, mainly in the ventriculus. The most common type was plastic fragments. Debris was most frequent in Diomedea species (25.6%) and, particularly, Diomedea sanfordi (38.9%) and very rare in Thalassarche species (2.0%), presumably reflecting differences in foraging behavior or distribution. Frequency of occurrence was significantly higher in male than female Diomedea albatrosses (39.3% vs. 18.0%). Although levels of accumulated debris were relatively low overall, and unlikely to result in gut blockage, associated toxins might nevertheless represent a health risk for Diomedea albatrosses, compounding the negative impact of other human activities on these threatened species. © 2015 Elsevier Ltd.

Jimenez S.,Recursos Pelagicos | Jimenez S.,Natural Environment Research Council | Jimenez S.,Research Center y Conservacion Marina | Phillips R.A.,Natural Environment Research Council | And 4 more authors.
Biological Conservation | Year: 2014

Pelagic longline fisheries in the southwest Atlantic are a major conservation concern for several threatened seabirds, including four species of great albatrosses: wandering albatross (Diomedea exulans), Tristan albatross (Diomedea dabbenena), southern royal albatross (Diomedea epomophora) and northern royal albatross (Diomedea sanfordi). The aim of this study was to examine the spatial and temporal variation in bycatch rates of these species, and to identify the contributing environmental and operational factors. We used data collected by observers on board pelagic longliners in the Uruguayan fleet in 2004-2011, and on Japanese vessels operating in Uruguay under an experimental fishing license in 2009-2011. Bycatch rates for northern and southern royal albatrosses were higher than expected based on previous reports, particularly over the shelf break. Wandering and Tristan albatrosses were caught predominantly in pelagic waters, where there are numerous fishing fleets from other flag states. Bycatch of great albatrosses was highest in April-November, with the peak for royal albatrosses in June-July, and for wandering and Tristan albatrosses in September-November. A range of vessel operational practices and habitat variables affected bycatch rates, among which setting time, moon phase, area and season are useful in terms of risk assessment, and in the development and improvement of conservation measures for these highly threatened species. © 2014 Elsevier Ltd.

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