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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

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. Source

Mendez S.M.,Direccion Nacional de Recursos Acuaticos DINARA | Ferrario M.,National University of La Plata | Ferrario M.,CONICET | Cefarelli A.O.,National University of La Plata
Harmful Algae

Pseudo-nitzschia is a genus of marine diatoms, widely distributed from tropical to polar regions. Over 35 species have been described, some of which produce domoic acid (DA). This neurotoxin is responsible for the intoxication syndrome in humans and marine animals called Amnesic Shellfish Poisoning (ASP). Most of these toxigenic species are an important component of phytoplankton and have been recorded in the Southern Cone of South America (Argentina, Brasil, Chile and Uruguay).The Dirección Nacional de Recursos Acuáticos (DINARA) conducted a long-term monitoring program along the Uruguayan coast, beginning with the first toxic algal event reported in 1980. Six species of Pseudo-nitzschia: P. australis, P. delicatissima, P. fraudulenta, P. multiseries, P. multistriata and P. pungens were reported in Uruguayan waters. Until recently, the only event with detected levels of DA (9.9μgDA/g), as determined by the HPLC standard method, was caused by P. multiseries in December 2001 with values reaching 1200cellsl -1. This record represents the first DA report associated with this species in Western Atlantic waters. In February 2009 P. multistriata was detected for the first time in Uruguayan waters, with a density of 2×10 6cellsl -1. This report suggests that Uruguay is the southern limit of its biogeographic distribution in the Southwest Atlantic. During this study, analysis by optical and scanning electron microscopy confirmed the presence of four species of Pseudo-nitzschia in Uruguayan waters: P. fraudulenta, P. multiseries, P. multistriata and P. pungens which are potentially producers of DA. We also include information on the trends in Pseudo-nitzschia abundance with water temperature and salinity. © 2012 Elsevier B.V. Source

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

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. Source

Orlando L.,Direccion Nacional de Recursos Acuaticos DINARA | Pereyra I.,Direccion Nacional de Recursos Acuaticos DINARA | Paesch L.,Direccion Nacional de Recursos Acuaticos DINARA | Norbis W.,Direccion Nacional de Recursos Acuaticos DINARA | Norbis W.,Laboratorio Of Fisiologia Of La Reproduccion Y Ecologia Of Peces
Brazilian Journal of Oceanography

In this work we analyzed the spatial and seasonal variation of length distribution, sexual proportion and mature dominance for Atlantoraja cyclophora and A. castelnaui, at the Uruguayan continental shelf. There were significant differences in total length (TL) composition between sexes, being females bigger than males for both species. Atlantoraja cyclophora showed a relatively uniform length distribution between inner and outer shelf. There were no major variations in the sex compositions and in the mature dominance between seasons, suggesting no temporal variation. Atlantoraja castelnaui showed a significant variation in its spatial and seasonal distribution. Individuals were smaller in inner shelf, pointing out the existence of juvenile zone in areas up to 50 m depth. A tendency to capture smaller individuals towards the end of the year was observed. In all seasons over 50% of females were caught below the estimated size at maturity, suggesting that this species is highly susceptible to exploitation. Source

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

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. Source

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