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Passadore C.,Laboratorio Of Recursos Pelagicos | Passadore C.,University of the Republic of Uruguay | Passadore C.,Research Center y Conservacion Marina | Passadore C.,Flinders University | And 3 more authors.
ICES Journal of Marine Science | Year: 2015

This study analyses depredation by killer whales (Orcinus orca) and false killer whales (Pseudorca crassidens) on catches of the Uruguayan pelagic longline fishery in the Southwestern Atlantic Ocean between 1998 and 2007. Data were collected by scientific observers from the National Observer Program of the Tuna Fleet operating in the area between 19°-40.5°S and 20°-54°W. Depredation occurred in 67 of the 1029 sets and was restricted to the area from 25°-40.5°S to 27°-53°W, though larger proportions of depredation (DP: percentage of total fish caught damaged by cetaceans) were observed in the Brazil-Malvinas (Falkland) Confluence area (34°-37°S and 51°-53°W) where most of the fishing effort was concentrated. Depredation occurred year-round though intra-annual variability in its intensity was recorded. The overall DP was 0.37% and was slightly higher in autumn. The spatial analysis showed that DP within grids of 1 × 1° was homogeneous and generally <2.5%. Ten out of 57 fish species caught by the fishery were depredated by cetaceans. Swordfish (Xiphias gladius) showed the highest DP per species (1.17%). Using the frequency of resources selectivity index of Ivlev, it was determined that swordfish was selected as a preferred prey in 43.9% of the sets with depredation. Generalized linear models indicated that distance to coast, year, and vessel were significant variables in explaining the number of fish depredated per fishing event. The presence of killer whales in the fishing ground seems not to affect the catch per unit effort by the longline fishery. The losses caused by depredation of cetaceans on the catch are low with probably minor economic effects to the Uruguayan longline fishing industry. © 2015 International Council for the Exploration of the Sea 2015. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Passadore C.,Laboratorio Of Recursos Pelagicos | Passadore C.,University of the Republic of Uruguay | Passadore C.,Research Center y Conservacion Marina | Passadore C.,Flinders University | And 3 more authors.
ICES Journal of Marine Science | Year: 2015

Bycatch is one of the main causes of human-caused mortality and population decline of many marine mammals. Monitoring bycatch is the first step to understand the impact of the fisheries on the species affected. Understanding how the interaction between marine mammals and fishing operations varies in space and time, and how it is influenced by environmental variables, is essential for designing mitigation strategies to reduce bycatch mortality. In this paper, we use data gathered by scientific observers and a fishing skipper to analyse marine mammals bycatch by the Uruguayan pelagic longline fishery operating in the Southwestern Atlantic Ocean from 1996 to 2007. The total bycatch per unit effort (Bcpue) was 0.0150 marine mammals/1000 hooks and the highest values (∼0.2) were recorded between 37°-38°S and 49°-51°W. Total cetacean Bcpue during the study period was low (0.0051 cetacean/1000 hooks) and occurred between 32°-37°S and 46°-54°W. Generalized additive models showed that cetaceans' bycatch was mainly affected by the depth, sea surface temperature, and season. Although cetaceans were captured year-round, the highest values were registered in spring months, most bycatch events occurred over the continental slope (median = 619 m) and in waters with a median temperature of 19.7°C. The bycatch of pinnipeds was influenced by depth, location, and season. Pinniped bycatch occurred mainly in winter, in waters ranging from 80 to 5000 m of depth (median = 2366 m) between 34°-37°S (median = 35.9°S) and 54°-49°W (median = 51.8°W). The spatial analysis showed that most bycatch events occurred within the Brazil-Malvinas Confluence zone, an area of high productivity where the pelagic longline fleet concentrates its fishing effort and where marine mammals probably concentrate to feed. © 2015 International Council for the Exploration of the Sea 2015. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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 .

Yorio P.,CONICET | Yorio P.,Wildlife Conservation Society | Branco J.O.,Vale do Itajai University | Lenzi J.,Research Center y Conservacion Marina | And 3 more authors.
Waterbirds | Year: 2016

In South America, Kelp Gulls (Larus dominicanus) breed from Chilean Tierra del Fuego north to Río de Janeiro, Brazil, on the Atlantic coast and to Piura, Peru, on the Pacific coast. This review presents the first synthesis of information on the distribution and size of Kelp Gull colonies at the country level in coastal environments of Uruguay, Chile and Peru; provides an update on the breeding situation of the species in Brazil and Argentina; and allows the first evaluation of the overall coastal breeding population in South America. The breeding population in South America is now estimated to number at least 160,000 pairs. The largest population (at least 106,000 breeding pairs) is found in Argentina. Colonies of more than 1,000 pairs are uncommon. Population trends differed among coastal sectors, and important increases in numbers and formation of new colonies were only observed in Argentina. Available information suggests that predictable and abundant anthropogenic food subsidies, such as fishery discards and urban waste, are key factors contributing to the population growth in some coastal sectors. There is no strong evidence that Kelp Gulls are currently expanding their breeding range. However, given the population expansion in some areas and the potential conflicts with humans, ongoing monitoring efforts and population evaluations are necessary as they will provide the information required to support management decisions.

Jimenez S.,Research Center y Conservacion Marina | Jimenez S.,University of the Republic of Uruguay | Domingo A.,Research Center y Conservacion Marina | Abreu M.,Research Center y Conservacion Marina | Brazeiro A.,University of the Republic of Uruguay
Endangered Species Research | Year: 2011

The region of the southwest Atlantic influenced by the Brazil-Malvinas Confluence (BMC) is important for globally threatened species of albatross and petrel. This applies particularly to the area of the continental slope, due to the high rates of incidental catch from pelagic longliners. We analyzed the temporal variation in the seabird assemblage associated with this fishery, identified the species that make use of discards, and evaluated their interactions while foraging. During 20 commercial fishing trips between 2005 and 2008, we completed 415 bird counts and recorded behavior in 172 of these. The observed species richness (≥38 species) is greater than that reported for any other fishery in the region and was highest from October to April, although many species in the assemblage were significantly more abundant between May and September. Only 14 species made significant use of discards, and all of these were albatrosses and petrels captured incidentally. We observed within- and between-species competition for access to discards. In general, the frequency of intraspecific competition was greater in the most abundant species, during the period of their greatest abundance. Albatrosses were more successful in interspecific competitive interactions, and we observed a dominance hierarchy related to body size. We conclude that the composition and seasonality of the seabird bycatch is determined by the spatiotemporal dynamics of the assemblage and by the observed pattern of interspecific interactions. Discards from pelagic longline fleets operating in the BMC may be an important food source for at least 8 species of globally threatened seabirds. Understanding the effect of discards on these populations could generate useful information for conservation, although reducing bycatch levels should be considered the main goal. © Inter-Research 2011.

Jimenez S.,Research Center y ConservaciOn Marina | Jimenez S.,University of the Republic of Uruguay | Domingo A.,Research Center y ConservaciOn Marina | Abreu M.,Research Center y ConservaciOn Marina | Brazeiro A.,University of the Republic of Uruguay
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2012

Species of petrels and shearwaters with high diving ability could facilitate the catch of albatrosses in pelagic longline fisheries, because they retrieve bait to the surface from depths that albatrosses cannot reach. Once on the surface, large seabirds such as albatrosses can easily displace smaller species thus gaining access to baited hooks which increases their likelihood of getting caught. This paper evaluates the extent to which diving species (i.e. Procellaria aequinoctialis, Procellaria conspicillata and Puffinus gravis) increase the susceptibility of albatross to bycatch in pelagic longline fisheries. In 48 sets, attacks on baits were quantified. When more than one bird (of the same or different species) tried to attack the same bait this was defined as a multiple attack. There were 384 attacks on baits, of which 260 were made by a single individual and 124 by more than one. Multiple attacks were the largest source of bycatch of albatrosses (22 of 27 albatrosses whose attacks were observed). Of the baits attacked by albatrosses (n=244), 17% were indirectly facilitated by diving medium-sized petrels. Considering only the multiple attacks in which albatrosses participated (n=114), 36% were initiated by these medium-sized petrels. Eleven (41%) of the albatrosses captured, and whose attacks were observed, resulted from a diving medium-sized seabird species first having contacted the terminal tackle. This paper shows that medium-sized petrels, with a strong ability to dive, increase considerably the access to bait, and indirectly, the incidental bycatch of albatrosses. Observations made in the absence of mitigation measures also provide useful information to improve the performance of tori lines. Based on the seabird behaviour, it is recommended that tori lines should have a minimum aerial coverage of 50 m. © 2012 John Wiley & Sons, Ltd..

Jimenez S.,Research Center y Conservacion Marina | Jimenez S.,Laboratorio Of Recursos Pelagicos | Marquez A.,Laboratorio Of Bioquimica Of Organismos Acuaticos | Abreu M.,Research Center y Conservacion Marina | And 4 more authors.
Emu | Year: 2015

Albatrosses are killed or injured through by-catch in longline fisheries and by collisions with warp cables in trawl fisheries. Detection of areas where albatrosses interact with fisheries is important for their conservation. Shy (Thalassarche cauta) and White-capped (T. steadi) Albatrosses are difficult to study from vessels as they are phenotypically similar. However, the two species can be identified by molecular analysis. The six-fold difference in the size of the total populations of these two species could mask by-catch of the less-abundant Shy Albatross, particularly when available sample sizes of by-catch are small. Here we document the species of a sample of 29 shy-type albatrosses killed as fisheries by-catch to confirm the observation that White-capped Albatrosses are the dominant shy-type albatross in the south-western Atlantic Ocean and exposed to the pelagic longline fishery there. Using a test based on a single nucleotide polymorphism (SNP) previously reported in the mtDNA of both species, 28 specimens were identified as White-capped Albatross. The SNP test and phylogenetic analyses suggested that the remaining bird was a Shy Albatross. Further analyses with other independent markers could confirm the identification of the latter. This result indicates the possibility that Shy Albatrosses reach the south-western Atlantic Ocean. There is no doubt that White-capped Albatrosses, which are a regular visitor to Uruguayan waters, is the predominant shy-type albatross in the south-western Atlantic. However, a small proportion of shy-type albatrosses in this region could be Shy Albatross but further analysis is needed to confirm this. Journal compilation © BirdLife Australia 2015

Jimenez S.,Research Center y Conservacion Marina | Jimenez S.,University of the Republic of Uruguay | Domingo A.,Research Center y Conservacion Marina | Abreu M.,Research Center y Conservacion Marina | Brazeiro A.,University of the Republic of Uruguay
Aquatic Living Resources | Year: 2012

Bycatch in longline fisheries is considered one of the main threats for the conservation of albatrosses and petrels worldwide. However, the relative impact of fisheries on all the affected populations or species still remains poorly understood. This paper applied a Productivity and Susceptibility Analysis (PSA) and the concept of "Potential Biological Removal Level" (PBR) to assess the relative impact caused by the Uruguayan pelagic longline fishery on several populations. This two-step approach allowed us to obtain an objective view of the relative impact of the Uruguayan pelagic longline fleet on most of the populations or species of albatrosses and petrels with high association with this fishery. Of fifteen species considered, fourteen were finally assessed and a ranking of risk derived. The concept of PBR was applied to the nine most at-risk species. The impact of fishing on populations could not be straightforwardly inferred from their bycatch rates. Results indicate that large albatrosses (Diomedea spp.) and Thalassarche chlororhynchos are more affected than some of the main species caught by the fishery (i.e. Thalassarche melanophrys and Procellaria aequinoctialis). Diomedea exulans from South Georgia is likely to be the population most affected by the Uruguayan fleet. This work should be seen as a case study of the fisheries operating in the southwestern Atlantic. The Uruguayan fleet within its operation area was responsible for only the 4.3% to 12.5% of the total annual effort deployed by the different fleets during 2004-2008. The combined impact of these fleets could be sufficiently high to account for many of the observed declines in the populations of D. exulans, D. dabbenena and T. chlororhynchos. However, the seabird bycatch numbers for most of the pelagic longline fleets that operate in the southwest Atlantic remain unknown. Applying mitigation measures to reduce the impact of pelagic longline fleets operating in this region should be considered a high priority. ©2012 EDP Sciences, IFREMER, IRD.

Pereyra S.,University of the Republic of Uruguay | Garcia G.,University of the Republic of Uruguay | Miller P.,Direccion Nacional de Recursos Acuaticos | Miller P.,Research Center y Conservacion Marina | And 2 more authors.
Fisheries Research | Year: 2010

The narrownose smooth-hound shark Mustelus schmitti is a coastal species endemic to the Southwest Atlantic Ocean. As this species is an important fishery resource, there is interest in knowing its genetic population structure. In this study, we used mitochondrial cytochrome b gene sequences to examine the genetic structure of the narrownose smooth-hound populations within the Río de la Plata and its Maritime Front in the SW Atlantic Ocean. We found no evidence for genetic structure in the analyzed samples. Low levels of pairwise ΦST values indicated high connectivity and suggested genetic homogeneity at this geographic range. Additionally, notably low nucleotide and haplotype diversities found in this species could indicate that M. schmitti experienced a population bottleneck, recent expansion or selection. The results presented here indicate that M. schmitti exists as a single demographic unit in the Río de la Plata and its Maritime Front. The low genetic diversity values found in the present study, together with the low resilience to exploitation of this species, raise considerable concern over the conservation status of M. schmitti. © 2010 Elsevier B.V.

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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