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Ortega L.,Direccion Nacional de Recursos Acuaticos DINARA | Castilla J.C.,University of Santiago de Chile | Espino M.,Instituto Del Mar Del Peru | Yamashiro C.,Instituto Del Mar Del Peru | Defeo O.,Direccion Nacional de Recursos Acuaticos DINARA
Marine Ecology Progress Series | Year: 2012

Coastal shellfish are being threatened by several drivers acting at multiple temporal and spatial scales, including fishing, climate, and globalization of markets. We evaluated largescale and long-term combined effects of fishing, climate, and economic variables on 2 congeneric clams that inhabit sandy beaches of the Pacific (Mesodesma donacium) and the Atlantic (M. mactroides) in South America. Bioeconomic and climatic variables, such as coastal sea surface temperature anomalies (SSTA) and broad-scale climatic indices (Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation), were related to variations in clam populations in a differential way according to latitude and oceanographic features. For M. donacium, the nature and sign of the relationships between landings and explanatory predictors markedly differed between bioclimatic units. El Niño Southern Oscillation events negatively affected landings in Peru and northern Chile, whereas landings increased in southern Chile and showed a positive correlation with increasing SSTA, suggesting a positive effect at the southernmost edge of the species distribution. Long-term trends in the abundance of M. mactroides were related to fishing intensity and SSTA. As anticipated by basic economic theory, deficit of supply relative to demand, exacerbated by very low harvesting costs, pushed the price up and has driven these clam species to levels close to extinction (anthropogenic Allee effect). The lack of response of the stocks to long-term closures suggests that these systems exceeded critical thresholds (tipping points). Information on early warnings of tipping points is needed to help manage coastal shellfisheries that are increasingly threatened by long-lasting and large-scale stressors. © Inter-Research 2012.

Dono F.,Grande Rio University | Montealegre-Quijano S.,Grande Rio University | Montealegre-Quijano S.,São Paulo State University | Domingo A.,Direccion Nacional de Recursos Acuaticos DINARA | Kinas P.G.,Grande Rio University
Environmental Biology of Fishes | Year: 2014

Age and growth estimates of shortfin mako sharks Isurus oxyrinchus from the western South Atlantic Ocean were obtained through the analysis of vertebral sections of 245 specimens (126 females, 116 males and 3 with undetermined sex), ranging in size from 78 to 330 cm fork length (FL), using a flexible growth model (Schnute model) and a Bayesian approach. A significant linear relationship was found between FL and vertebral radius for sexes combined. Marginal increment analyses were inconclusive about periodicity of growth band deposition and an annual periodicity was assumed to make age estimations. Specimens were estimated to be between 0 and 28 years of age. The Schnute model provided a good description of the individual growth for both sexes up to 15 years of age. Shortfin mako growth during the first year of life was 33.9 cm (ICr95% = 19.9–40.8) for females and 30.5 cm (ICr95% = 25.6–35.4) for males. Until approximately 15 years of age, both sexes showed similar growth and reached ~217 cm FL. Sigmoid shaped growth curves obtained for both sexes indicated a change in the growth pattern close to 7 years of age. Inconclusive results about periodicity of growth band deposition in the study area make necessary the application of more robust validation techniques in the future. Meanwhile, a precautionary approach that assumes an annual deposition pattern in the western South Atlantic can be used for the assessment and management of stocks of this species, characterized by low fecundity and late maturity. © 2014, Springer Science+Business Media Dordrecht.

Rodriguez D.H.,CONICET | Dassis M.,CONICET | Ponce de Leon A.,Direccion Nacional de Recursos Acuaticos DINARA | Barreiro C.,Direccion Nacional de Recursos Acuaticos DINARA | And 3 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2013

The stocks of Southern sea lions (Otaria flavescens, SSL) and South American fur seals (SAFS) that breed on coastal islands of Uruguay constitute the most important focal concentration of pinnipeds in South America, with a significant increase in SAFS and a steady decrease of SSL over the past decades. Because females are a key element of population dynamics and no information exists on the post-breeding pup rearing period, we studied the foraging patterns of SSL females in the La Plata River Estuary (LPRE) during mid and late lactation (late austral autumn and winter), analyzing the foraging performance, geographic coverage and ontogenetic differences in foraging strategies for a period of 1-5 months. At-sea movements of 22 SSL females (6 subadults and 16 adults) from Isla de Lobos (IL, 35°01'28"S-54°52'59"W, Uruguay) were monitored using satellite transmitters (SPOT4, SPOT5 and STDR-S16, Wildlife Computers) in 2007 and 2010. An algorithm [McConnell, B.J., Chambers, C., Fedak, M.A., 1992. Foraging ecology of southern elephant seals in relation to the bathymetry and productivity of the Southern Ocean. Antarct. Sci. 4, 393-398.] with a maximum transit speed of 3ms-1 was applied to the Argos information, resulting in a total of 2522 filtered locations. A daily mean of 3.5±1.74 filtered locations per animal was received. One hundred and eighty three foraging trips (FT) were recorded with no significant differences (p<0.05) between subadults and adults in the duration of FT (6.1±3.15 day), distance traveled per FT (237.2±105.25km), mean distance from IL (57.2±25.90km), maximum straight line (Spider) distance (100.2±41.40km) and transit speed (1.1±1.04ms-1). SSL showed directional fidelity to foraging sites, indicated by high mean vector (r) values (0.74±0.14) calculated from FT mean bearings. Kernel ranges for 50% and 95% of all FT locations were 5420km2 and 36,222km2, respectively, and the extension of the foraging areas appeared to be influenced by a combination of bathymetry and ecological boundaries within LPRE. Regardless of their reproductive condition, females showed a strong fidelity to IL, and their foraging activity was restricted to relatively shallow areas (10-100m) on the continental shelf. During autumn and winter, SSL females made significantly longer FTs than during the breeding season, when lactating females decrease FT duration by increasing transit speed but maintain a similar spatial coverage compared with FT later in lactation. Although several aquatic areas of high priority for conservation in LPRE have been identified and proposed, only 15% of the foraging habitat of SSL females is currently included in these areas. This emphasizes the importance of the inclusion of the at-sea foraging distributions of central point foragers in marine protected areas. If conservation efforts focus only on coastal breeding concentrations, key elements of the life cycle are excluded with potential unpredictable effects. © 2012 Elsevier Ltd.

Ortega L.,Direccion Nacional de Recursos Acuaticos DINARA | Celentano E.,University of the Republic of Uruguay | Finkl C.,Florida Atlantic University | Finkl C.,Coastal Education and Research Foundation | And 2 more authors.
Journal of Coastal Research | Year: 2013

Oretga, L.; Celentano, E.; Finkl, C., and Defeo, O., 2013. Effects of climate variability on the morphodynamics of Uruguayan sandy beaches. Effects of long-term trends in climatic variability on the morphodynamics of a reflective and a dissipative sandy beach in Uruguay (SW Atlantic Ocean) were analyzed. The Atlantic Multidecadal Oscillation (AMO) alternates between warm and cold cycles with a periodicity of roughly 70 years, with a shift toward a warm phase since 1995, resulting in an increase of sea surface temperature in the study area. Wind speed anomalies (WSA) also increased through time and were associated with an increasing speed of southerly winds, particularly after 1997. Beach morphodynamics showed no statistically significant trends in grain size, but long-term morphodynamic patterns differed between beaches: the dissipative beach showed an increase in swash and beach width, Dean's parameter, and the Beach Index (a measure of beach morphodynamic state). At the same time, the slope decreased, augmenting the beach's dissipative characteristics. The reflective beach showed an increase in slope and swash width through time, and a decrease in the Beach Index, indicating an intensification of reflective characteristics. Long-term morphodynamic changes were more evident in the dissipative beach and related to climate forcing (e.g. WSA). A higher resilience was observed in the reflective beach, even though an increasing frequency of storms is affecting both beaches. Accelerating erosion, rising sea levels, and expanding urban development in the Uruguayan coast could affect biodiversity and critical habitats. Multidisciplinary investigation programs and conservation strategies are needed to mitigate negative anthropogenic effects on these ecosystems. © 2013 Coastal Education & Research Foundation.

Lorenzo M.I.,Direccion Nacional de Recursos Acuaticos DINARA | de Astarloa J.M.D.,CONICET | Norbis W.,Direccion Nacional de Recursos Acuaticos DINARA | Cousseau M.B.,CONICET
Brazilian Journal of Oceanography | Year: 2011

Demersal fish assemblages from trawl surveys in the Rio de la Plata estuary and its inner continental shelf were analyzed from 1975 to 1995. The first two factors of Principal Component Analysis explained 48% of the variance in species distribution, and they are consistent with the results of a cluster analysis. The analysis indicated the existence of three spatially and temporally distinct fish assemblages: internal and external estuarine and inner continental shelf (Uruguayan coastal assemblages). These assemblages were persistent considering the environmental characteristics and their species composition. Despite the changes registered in the species density during the period surveyed, the fish assemblages tend to persist over time. It was demonstrated that the assemblages can be considered as open systems and that there exists a reciprocal flow of organisms between adjacent associations. However, each assemblage showed high spatial and temporal persistence in accordance with the environmental characteristics of the system analyzed. Therefore, and according to the multispecies fisheries operating in the system, each assemblage defined could be considered a unit of management.

PubMed | CONICET, Direccion Nacional de Recursos Acuaticos DI.NA.R.A., University of Alaska Fairbanks and National University of Central Buenos Aires
Type: Journal Article | Journal: Biological trace element research | Year: 2016

Levels of zinc (Zn), copper (Cu), potassium (K), calcium (Ca), magnesium (Mg), and phosphorus (P) in plasma of Otaria flavescens females (n=29) were evaluated. Reference intervals were established for each element, being the first report for this species.

PubMed | CONICET and Direccion Nacional de Recursos Acuaticos DINARA
Type: Journal Article | Journal: Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology | Year: 2016

The goal of this study was to characterize for the first time the electrocardiogram (ECG) of the southern sea lion (SSL) Otaria flavescens.Thirteen wild SSL females were captured at Isla de Lobos (Uruguay) and anaesthetized with isoflurane. Electrocardiographic recording was performed on anaesthetized animals at ventral recumbence following standardized procedures.The ECG recordings showed normal sinus rhythm. Amplitude and duration of P and T waves, QRS complex, PR interval, QT intervaland ST segment (STS) were determined for all animals in all leads. QT correctedwas determined in lead II. P wave polarity was consistent among animals (positive in LI, LII, LIII and AVF leads and negative in AVL and AVR leads for all animals), but T wave polarity did not present any constant pattern among animals, being either positive, negative or biphasic in different leads and different animals. The PR interval (0.150.2s) was similar to the allometric prediction for most of mammalian species including humans. The STS were normal in 10 of the SSL but showed STS depression in three of the animals. Almost all animals had a negative electrical axis (-30 to -120), with one exception that showed a positive electrical axis (120). Mean eupnoeic heart ratewas 104.6110.06 (range=88-120) beats per minute.This study was the first ECG description for this species, and provides valuable information for cardiac monitoring during anaesthesia.

D'Anatro A.,University of the Republic of Uruguay | Pereira A.N.,Direccion Nacional de Recursos Acuaticos DINARA | Lessa E.P.,University of the Republic of Uruguay
Environmental Biology of Fishes | Year: 2011

Micropogonias furnieri is widely distributed in the southwestern Atlantic Ocean. In Uruguay, Laguna de Rocha and Río de La Plata estuary have been reported as reproductive and nursery areas. In Laguna de Rocha, individuals reach maturity at smaller total length than their oceanic counterparts. It has been difficult to establish whether Laguna de Rocha represents a biologically distinct population or simply ecophenotypic variation. More generally, the possible presence of several distinct populations of white croakers in Uruguayan waters has been hypothesized, but limited data exist to substantiate them. A recent mitochondrial DNA analysis suggested divergence between the Río de La Plata and the Oceanic front populations. Using seven microsatellites loci, we studied the population structure of M. furnieri in the nursery areas suggested by the literature, as well as in three additional localities to test these hypotheses. The individuals of Laguna de Rocha showed a moderate genetic differentiation with respect to some of the other populations surveyed. Specimens of Montevideo showed the higher genetic distinctiveness. Given the apparent absence of geographical barriers, other factors may be responsible for the observed differentiation. The complex pattern of forces interacting in this system makes it difficult to disentangle the causes of the population structure found. The adaptation to local environmental conditions could be playing an important role in population differentiation, as well as the possible selective pressures imposed by fisheries. The results obtained in this work offer clues about the processes responsible for differentiation of fishes in estuarine and marine environments. © 2011 Springer Science+Business Media B.V.

The present study analyses the seasonal (summer: January, February, March; autumn: April, May, June; winter: July, August, September and spring: October, November, December) and annual (2006, 2007 and 2011) length-weight relationships and condition factors of Micropogonias furnieri and Cynoscion guatucupa from Río de la Plata and the Uruguayan ocean coast from data collected throught monthly landings by the Uruguayan coastal fleet in the Montevideo port (Uruguay). A total of 9,146 individuals of M. furnieri ranging from 15 to 69 cm total length (LT); and 5,285 individuals of C. guatucupa, ranging from 21 to 54 cm LT were analyzed. For both species, the allometry coefficients showed that growth in the majority of seasons were negative (b < 3), except for M. furnieri in spring 2006 (isometric, b = 3) and during summer 2011 (positive, b > 3). For M. furnieri, no significant differences among slopes were found between 2006 and 2007 whereas 2011 showed significant differences compared to 2006 and 2007. For C. guatucupa no significant differences among slopes were found between 2007 and 2011, whereas 2006 showed significant differences with other years. The highest values for the condition factor in M. furnieri were recorded in summer 2006, and during the summer and autumn 2007 and for C. guatucupa in winter 2006 and autumn 2007. Significant seasonal and annual differences for condition factors were found for both species. This work provides the first reference regarding condition factor for both sciaenid species in the study area. © 2016, Universidad de Valparaiso. All rights reserved.

The whitemouth croaker (Micropogonias furnieri) and striped weakfish (Cynoscion guatucupa) are the most important resource of coastal fisheries in the Southwest Atlantic Ocean and particularly in the Rio de la Plata estuary. The aim of this study is to analyze the spatial and temporal co-occurrence of both species in relation to density estimates, length structure and immature-mature individuals using research vessel data from the spring of 1991-1995 and 2007. A positive tendency for cooccurrence and species overlap occurred in more than 53% of fishing trawls, either significantly or with predominance of whitemouth croaker or striped weakfish. Differences between the spatial distributions of both species during the spring in the study area were found for all years with the exception of 1992, a supposed consequence of increased river discharge related to El Niño/Southern Oscillation (ENSO) effects. In fishing hauls where significant species overlap occurred, length composition showed that whitemouth croaker adults spatially co-occurred with juveniles of striped weakfish. The nonrandom spatial segregation of both species as consequence of habitat heterogeneity and differential feeding habits did not support the ecological interdependence hypothesis. Rather, according to the trawler fleet that operates and directs the fishing effort directed towards these two target species, there may be evidence of technological interdependence. Fishing trawls may affect different length classes with different environmental requirements at different stages of their life history. These aspects should be considered when weighing different fisheries management options, related to the spawning areas and genetic management units of both species.

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