ABSTRACT Invasive species are among the most important problems for biodiversity conservation worldwide, particularly in megadiverse countries such as Brazil. However, there is no biological information to develop policies for managing invasive species populations in many cases. The life history parameters and otolith variations are essential to understanding the adaptations of the species introduced in marine environments. This study aimed to identify the age structure and ontogenetic variation in the sagitta otolith of Opsanus beta. Fish samples were obtained monthly in the Paranaguá Estuarine Complex (PEC), south of Brazil. The shape indices verified ontogenetic variations in the otoliths (PERMANOVA; F = 110; P < 0.0001), but no sexual variations were observed in the shape of the otoliths (PERMANOVA; F = 3.65; P > 0.05). Specimen aged between 1 to 9 years were observed in the PEC, with the highest occurrence of individuals between 3 and 6 years (78%). No sexual differences were observed between the ages by the Kimura test. Our results confirm that the O. beta population is well established with age groups similar to that observed in the region where the species is native.

ABSTRACT. Oceanographic fluctuations and changes in ocean productivity directly affect the abundance and distribution of prey species, which in turn, affect the population status of their predators. In order to have a better understanding of this predator-prey relationship, the aim of the present study was to analyze the diet of the South American Sea Lion Otaria flavescens (Shaw, 1800) in two rookeries of the San Matias Gulf, in northern Patagonia (Argentina). A total of 52 scat samples of O. flavescens were collected in the Promontorio Belén colony and 35 in Caleta de los Loros during the late spring of 2011. The analysis of the samples indicated that at both localities fish occurred in 100% of scats with prey remains, followed by cephalopods (32.3%) and crustaceans (21.4%). The fish Raneya brasiliensis (Kaup, 1856) constituted the main prey taxon, both in terms of occurrence and numerical abundance. The octopod Octopus tehuelchus (d’ Orbigny, 1834) and squids of the genus Doryteuthis constituted the dominant cephalopod prey. It is concluded that sea lions focused their foraging activity on those species of demersal and benthic habits, associated with coastal and shelf waters. Furthermore, this study reports for the first time the feeding habits of the South American Sea Lion colony of Promontorio Belén, second in population size of Río Negro province.

RESUMEN. Lobos marinos de un pelo sudamericanos Otaria flavescens ¿buenos indicadores de cambios espaciales y temporales relativos en la distribución y abundancia de los recursos marinos? Las fluctuaciones oceanográficas y los cambios en la productividad del océano afectan directamente a la abundancia y distribución de las especies presa, que a su vez afectan al estado de la población de sus predadores. Con el fin de tener una mejor comprensión de esta relación predador-presa, el objetivo del presente trabajo fue analizar la dieta del lobo marino de un pelo sudamericano Otaria flavescens (Shaw, 1800) en dos apostaderos del Golfo San Matias, en Patagonia norte (Argentina). Se colectaron un total de 52 muestras de fecas de O. flavescens en el apostadero de Promontorio Belén y 35 en Caleta de los Loros durante la primavera tardía de 2011. El análisis de las muestras indicó que en ambas localidades los peces ocurrieron en el 100% de las muestras con remanentes alimentarios, seguidos por cefalópodos (32.3%) y crustáceos (21.4%). El pez Raneya brasiliensis (Kaup, 1856) constituyó el principal taxón presa, tanto en términos de ocurrencia como de abundancia numérica. El octópodo Octopus tehuelchus (d’ Orbigny, 1834) y los calamares del género Doryteuthis constituyeron los cefalópodos presa dominantes. Se concluye que los lobos marinos centraron su actividad forrajera en aquellas especies de hábitos demersales y bentónicos, asociado a aguas costeras y de plataforma. Además, este estudio analiza por primera vez los hábitos alimenticios de la colonia de lobos marinos de un pelo sudamericanos en el apostadero de Promontorio Belén, segunda en tamaño poblacional de la provincia de Río Negro.

ABSTRACT Menticirrhus americanus were sampled (n = 393) from two beaches (P1 is an estuarine beach near the mouth of the Paranaguá Estuarine Complex, and P2 is a beach adjacent to the Paranaguá Estuarine Complex) in the subtropical region of the western South Atlantic waters between August 2015 and June 2016. This study aimed to identify the spawning season and the age structure for M. americanus using two sampling methods. For sampling at the P1 beach, seine, line, and pole were used, while samples from the P2 beach were obtained from the artisanal fishers. Females were numerically dominant in all sampling months at both sites except for February when the males became dominant. The species exhibited a protected reproductive season with multiple spawning peaks between August and December. Males and females were captured at all gonadal development stages and ages between 1 and 6 from both sites. At first maturity, the length of the females was 16.3 cm, and the mean age at first maturity was 1.3 years. Individuals aged between 1 and 3 years were dominant (68%). The results suggested that young and adults of the M. americanus use the same habitats throughout their ontogeny.

ABSTRACT Length-weight (LWR) and length-length (LLR) relationships were described for three marine fish species Odontesthes argentinensis (Valenciennes, 1835), Urophycis brasiliensis (Kaup, 1858) and Brevoortia aurea (Spix & Agassiz, 1829) from the southwestern Atlantic Ocean coast, among sampling sites between 36 and 38°S. These species have commercial importance in fisheries. Latitudinal change in LWR could suggest the existence of different subpopulations throughout their distribution ranges. A total of 2,167 specimens were collected between August 2015 and October 2018 using lift nets (mostly 10 mm mesh size) and fishing rods 100-200 m offshore. Both relationships were highly significant (P < 0.0001) for all species and produced robust coefficients of determination (R2 > 0.94). The latitudinal trend of a and b parameters of LWR showed different patterns for each species. This study provides a new maximum length for B. aurea and describes the variation of the regression parameters. New length-length relationships of these species were reported.

Abstract This study aimed to verify variations in the form of the sagitta otolith of Menticirrhus americanus as to their ontogeny, sex and stage of such structure. Ontogenetically were found significant differences (p < 0.05) for all shape indices (aspect ratios, shape factor, rectangularity, ellipticity, relative surface of sulcus acusticus) and also in the wavelet of the otolith. The CVA presented a 98.6% correct reclassification of the otolith between interval class. Sexual variations were found in the wavelet and in the relative surface of sulcus acusticus index. Between adult females and young females, differences were not detected in the wavelet and rectangularity, but significant differences were found in all other shape indices. The CVA presented a 79.6% correct reclassification of the otolith of the sexes and stages of life sampled. Young females and adults females showed highest correct percentage of classification. The results of this study demonstrate for the first time the influence of the ontogenetic variation and sexual in the form of the otoliths.

ABSTRACT Water bodies in the Chaco-Pampean plain contain arsenic (As) and fluoride (F-) occurring naturally. Chasicó Lake, located in the southwest of Buenos Aires Province, has high concentrations of both elements (As, 0.05-0.41 mg/L; F-, 6.74-8.54 mg/L). Fish can be considered as indicators of environmental pollution. The aim of this study was to analyze whether the presence of high concentrations of As and F- found in the liver and gills of Odonthestes bonariensis could be associated to histological changes found in these tissues. Fish were sampled from different locations of the lake. Tissue samples (liver and gills) were subdivided and subjected to an acid digestion to determine As and to an alkaline digestion to determine F-. Morphological changes were assessed using routine histological techniques. As concentrations in the liver were higher than in the gills, while the gills showed higher F- concentrations. The histological examination of the liver and gills showed alterations that could correspond to the effects of the high As and F- concentrations found in these tissues. The toxicity of these elements is due to oxidative stress. Silverside is one commercially relevant fish in Buenos Aires and a key species in the food chain in the region. Therefore, further histopathological studies are relevant to guarantee this fish’s health and safety for human consumption.

RESUMEN Los cuerpos de agua de la llanura Chaco-Pampeana contienen arsénico (As) y fluoruro (F-) cuyo origen es natural. El Lago Chasicó, ubicado en el sudoeste bonaerense, presenta elevadas concentraciones de ambos elementos (As: 0.05-0.41 mg/L; F-: 6.74-8.54 mg/L). Los peces pueden considerarse como indicadores de contaminación ambiental. El objetivo de este estudio fue analizar si la presencia de altas concentraciones de As y F- halladas en hígado y branquias de Odonthestes bonariensis pudiera estar asociada con los cambios histológicos encontrados en estos tejidos. Los peces fueron colectados en diferentes localidades del lago. Se subdividieron muestras de tejidos (hígado y branquias) y se sometieron a una digestión ácida para determinar As y a una digestión alcalina para determinar F-. Los cambios morfológicos se determinaron mediante técnicas histológicas de rutina. En hígado se hallaron concentraciones de As más altas que en branquias, mientras que las branquias mostraron concentraciones de F- más elevadas. El examen histológico del hígado y las branquias mostró alteraciones que podrían corresponder a los efectos de las altas concentraciones de As y F- halladas en esos tejidos. La toxicidad de estos elementos se debe al estrés oxidativo. El pejerrey es uno de los peces comerciales más importantes de Buenos Aires y una de las especies clave de la cadena alimenticia en la región, por lo que resultan relevantes estudios histopatológicos adicionales para asegurar la salud de los peces y su inocuidad para el consumo humano.

The objective of the present study was to evaluate the use of sagitta otolith microchemistry (Sr:Ca, Ba:Ca ratios) as habitat indicator of Anchoa tricolor between the estuary and the adjacent continental shelf. We analyzed 162 specimens of A. tricolor in the Paranaguá Estuarine Complex (Brazil), and salinity and rainfall data. The biological and environmental data were grouped into sectors (internal, intermediate, and external) and periods (early and late wet, and dry periods). The concentrations of Ca, Ba and Sr were determined using an ICP-OES. The Sr:Ca ratio indicated the existence of two groups, probably from different origins, that use the estuary at the same time, but occupying different sectors of the estuary. The Ba:Ca ratio did not differentiate the groups as to the use of estuary, but rather revealed low values, suggesting that this species does not use freshwater environments. However, this ratio showed a high variation in the wet period, indicating a greater availability of barium in the estuarine regions affected by the river discharge. Considering our results, it is possible to classify A. tricolor as an estuarine migrant species. Also, the Sr:Ca and Ba:Ca ratios can be indicative of the habitat use in a subtropical estuary.

ABSTRACT The streaked prochilod, Prochilodus lineatus, represents the most important fishery in the La Plata Basin (South America). Our objective was to analyze brackish environment use by the streaked prochilod captured from Paraná and Uruguay rivers. To accomplish this, lapillus otolith sections were analyzed for Sr:Ca with laser ablation-inductively coupled plasma-mass spectrometry (LA ICP-MS) to infer habitat use of fish. To the interpretation of transects, a threshold that represents the transition between freshwater and brackish environments was calculated using the Sr:Ca ratio of the otolith edge of specimens captured in the first section of the La Plata Estuary (salinity ≥ 0.5 PSU). The percentage of fish using the estuary was higher in the Paraná (37%) than the Uruguay River (5%). Change-point analysis showed that fish entered the estuary between 1 and 3 times throughout life at a wide range of ages (0-15 years). These incursions had no obvious periodicity. This information should be integrated into future management actions, which should also be specific to each area since migration patterns differ between the major rivers of the basin.

RESUMEN El sábalo, Prochilodus lineatus, representa la pesquería más importante en la Cuenca del Río de la Plata (Sudamérica). Nuestro objetivo fue analizar el uso del hábitat estuarino del sábalo proveniente de los ríos Uruguay y Paraná. Para esto, se analizó la relación Sr:Ca en secciones de otolitos lapilli por ablación láser acoplada a espectrometría de masas con fuente de plasma de acoplamiento inductivo (LA ICP-MS) para inferir el uso de hábitat. Para interpretar las transectas, un umbral que representa la transición entre los ambientes de agua dulce y estuarino, fue calculado usando la relación Sr:Ca del borde del otolito de especímenes capturados en la primera sección del estuario del Plata (salinidad ≥0.5 UPS). El porcentaje de peces que usaron el estuario fue más elevado para el Paraná (37%) en relación al Uruguay (5%). El análisis de cambio puntual mostro que los individuos ingresan al estuario entre 1 a 3 veces a lo largo de la vida en un amplio rango de edades (0-15 años). Las incursiones no mostraron una periodicidad notoria. Esta información debería integrarse a futuras acciones de manejo que deberían ser específicas para cada área considerando los patrones de migración que difieren entre los grandes ríos de la Cuenca.

ABSTRACT The streaked prochilod Prochilodus lineatus (Valenciennes) is a commercially freshwater species from South America, distributed in the Plata basin. In the present work the morphometry (circularity, rectangularity, form factor, OL/OW and ellipticity indices) and chemistry (Sr:Ca, Ba:Ca, Zn:Ca) of lapilli otolith, and geometric morphometry of scales of streaked prochilod juveniles, in two sites in the Plata basin (Uruguay River and Estrella Wetland), were compared to determine if they are area-specific and to identify possible breeding areas. Otolith Ba:Ca ratios was 0.017±0.003 mmol/mol for Uruguay River while for Estrella Wetland individuals was bellow the detection limits. Zn:Ca ratios tended to be higher for the latter (0.03±0.002 mmol/mol). Significantly high circularity and low rectangularity values were obtained for Estrella Wetland otoliths (p < 0.05), while no significant differences for form factor, OL/OW and ellipticity were observed between sampling sites. Considering all scale geometric morphometry variables, discriminant analysis showed a good percentage of classification of individuals (90.5% for Estrella Wetland and 85.7 % for Uruguay River). These results indicate that the otolith microchemisty and morphometry (circularity and rectangularity indices) and scale morphometry are good markers of habitat and represent a potential tool for identification of streaked prochilod nursery areas.

RESUMEN El sábalo Prochilodus lineatus (Valenciennes) es una especie de importancia comercial de agua dulce de Sudamérica, distribuida en la cuenca del Plata. En este trabajo se comparó la morfometría (índices de circularidad, rectangularidad, factor de forma, OL/OW y elipticidad) y microquímica (Sr:Ca, Ba:Ca y Zn:Ca) del otolito lapilli, y la morfometría geométrica de las escamas de sábalos juveniles capturados en dos sitios de la cuenca del Plata (Río Uruguay y bañado la Estrella), para determinar si existen diferencias área-especificas e identificar posibles sitios de cría. La relación Ba:Ca del otolito fue 0.017±0.003 mmol/mol para el río Uruguay mientras que estuvo por debajo del límite de detección para los individuos del bañado la Estrella. La relación Zn:Ca tendió a ser más alta en el bañado la Estrella (0.03±0.002 mmol/mol). Se obtuvieron valores significativamente altos de circularidad y bajos de rectangularidad para el bañado la Estrella (p < 0.05), mientras que no se hallaron diferencias para el factor de forma, OL/OW y elipticidad. Considerando la morfometría geométrica de las escamas, el análisis discriminante mostró buenos porcentajes de clasificación (90.5% para el bañado la Estrella y 85.7 % para el Río Uruguay). Estos resultados indican que la microquímica y morfometría del otolito (índices de rectangularidad y circularidad) y la morfometría de las escamas son buenos marcadores de hábitat y representan una herramienta potencial para la identificación de sitios de cría del sábalo.

The identification of fish stocks in basic requirement for fishing management. The objective of this research was to describe for the first time otoliths river crocker (Plagioscion ternetzi) and to evaluate the existence of different fish stocks in the Paraguay River lower basin and the middle Paraná River (northeast Argentinean region and southeast Paraguayan region). For this purpose, five morphometric indexes applied on sagitta otolith (rectangularity, circularity AO/SO, SS/SO and PS/PO) were compared between the study sites. The sagittae otoliths are semicircular and with smooth edges. Sulcus acusticusis is heterosulcoid and curved, with an ostium open widely in the anterior margin of the otolith. Significant differences were observed for circularity, rectangularity, SS/SO and PS/PO (t-test, P < 0.05). The T² Hotteling multiparametric analysis showed significant differences between the study sites (P < 0.006), while the canonical discriminant showed a high classification percentage of the individuals (>69%). The results indicates that the stocks populations would be partially separated, with a considerable flow of individuals between these rivers.

La identificación de stocks pesqueros es un requisito básico para el manejo y la gestión de la pesca. El objetivo de este trabajo fue describir por primera vez los otolitos de la corvina de Río P. ternetzi y evaluar la existencia de diferentes stocks pesqueros entre dos áreas de la Cuenca del Plata, cuenca baja del Río Paraguay y el Río Paraná medio. Con este fin, cinco índices morfométricos aplicados sobre los otolitos sagittae (rectangularidad, circularidad AO/LO, SS/SO y PS/PO) fueron comparados entre los sitios de estudio. Los otolitos sagittae son semicirculares y presentan bordes lisos. El sulcus acusticus es de tipo heterosulcoide y curvo, con abertura pseudoostio-caudal. Se observaron diferencias significativas para circularidad, rectangularidad, SS/SO y PS/PO (t- test, P < 0,05). El análisis multiparamétrico T² de Hotteling mostró diferencias significativas entre los sitios de estudio (P < 0,006) mientras que el análisis canónico discriminante mostró un alto porcentaje de clasificación de los individuos (>69%). Los resultados obtenidos sugieren que las poblaciones de esta especie de los ríos Paraguay y Paraná estarían parcialmente separadas, aunque mantendrían flujo de individuos entre las mismas.

ResumoPara conhecer o habitat e os hábitos alimentares de Mugil liza na costa sul de Buenos Aires, 65 exemplares obtidos durante a primavera (novembro de 2012) e o verão (fevereiro de 2013) foram analisados em duas áreas de amostragem: na Baía San Blas (SBB) e na foz do rio Quequén-Salado (QSR). Os exemplares foram medidos, pesados, o sexo foi identificado, os estômagos foram removidos e os conteúdos estomacais pesados e analisados sob estereomicroscópio. Os espécimes de M. liza eram adultos com comprimentos entre 28-49 cm e pesos entre 380-1100 g. O crescimento populacional foi maior na SBB (TW: 0,003*TLx3,36), do que na QSR (TW: 0.045*TL2.61). Em 98% dos estômagos, havia conteúdo estomacal e o índice de repleção variou entre 0,4 e 1,2%. Um total de 75% dos conteúdos estomacais foi composto de areia muito fina, com pouca presença de organismos bentônicos (algas, copépodas, foraminíferos), enquanto que em 25% dos estômagos havia areia grossa, com um aumento da presença de organismos da fauna bentônica (anfípodas, bivalves, gastrópodes e corais). As relações lineares entre o peso do conteúdo estomacal e o peso total e comprimento do peixe mostraram que as taxas de crescimento (inclinação) foram as mesmas em ambas as áreas de amostragem, mas os valores do intercepto foram significativamente maiores na Baía San Blas (teste t; p < 0,001).

AbstractIn order to get to know the habitat and feeding habits of Mugil liza on the southern coast of Buenos Aires province, 65 specimens obtained at two sampling sites - the San Blas bay (SBB) and the mouth of the Quequén-Salado river (QSR) - during spring (November 2012) and summer (February 2013) were analyzed. Specimens were measured, sexed and weighed, their stomachs were removed and their stomach contents weighed and analyzed under the stereoscopic microscope. The specimens were adults, 28-49 cm in length and weighing 380-1100 g. Population growth was higher in the SBB (TW: 0.003*TL3.36), than in RQS (TW: 0.045*TL2.61). About 98% of the stomachs had some content, their repletion rate being of between 0.4 and 1.2%. About 75% of the stomachs contained very fine sand with few benthic organisms (algae, copepods, foraminifera), whereas the remaining 25% of stomachs contained coarse sand and a greater presence of benthic fauna (amphipods, bivalves, gastropods and coral organisms). The linear relationship between the weight of stomach contents and the total weight and length of the fish showed that the rates of growth (slope) were the same at both sites, but intercept values were significantly higher for San Blas bay (test parallelism; p < 0.001).

We evaluate the simultaneous use of Sr: Ca and Zn: Ca ratios of the sagitta otolith as a potential indicator of the habitat of Percophis brasiliensis along a latitudinal gradient in the southwestern Atlantic Ocean (34-42ºS and 51-67ºW), in order to reliably identify fish stocks. Fish were collected in three sampling sites: Argentine-Uruguayan Common Fishing Zone (AUCFZ), El Rincón (ER) and San Matías Gulf (SMG). The otolith Sr:Ca and Zn:Ca ratios were determined by ICP-OES and EDTA volumetric method. The otolith Sr:Ca ratio was similar in the three sampling sites, while the Zn:Ca ratio was significantly higher in AUCFZ than in ER and SMG for all age groups. The discriminant analysis showed an association between the otolith Sr:Ca and Zn:Ca ratios from ER and SMG. Present results suggest the potential occurrence of two fish stocks of P. brasiliensis in the study area.

Evaluamos el uso simultáneo de las relaciones Sr:Ca y Zn:Ca de los otolitos sagittae como un potencial indicador de hábitat de Percophis brasiliensis a lo largo de un gradiente longitudinal el Atlántico sudoccidental (34-42ºS - 51-67ºW) con el fin de contribuir a la identificación de los stocks pesqueros. Los peces fueron capturados en tres sitios de muestreo: Zona Común de Pesca Argentina-Uruguaya (ZCPAU), El Rincón (ER) y el Golfo San Matías (GSM). Las relaciones Sr:Ca y Zn:Ca se determinaron por ICP-OES y por titulación con EDTA. La relación Sr:Ca fue similar en los tres sitios de muestreo. La relación Zn:Ca fue mayor en la ZCPAU que en las demás areas (ER y GSM) para todos los rangos de edad. El análisis discriminante mostró una asociación entre las relaciones Sr:Ca y Zn:Ca de ER y GSM. Los resultados de este trabajo sugieren la presencia de al menos dos stocks de P. brasiliensis en el aérea de estudio.

Abstract: The silverside Odontesthes bonariensis is a euryhaline species native of South America and represents a very important fishing resource for the Plata Basin (Argentina and Uruguay). This study compares the Sr:Ca ratio of water as well as the Sr:Ca ratio and morphometry of the sagittal otolith of the silverside present in different environments (one salt lake, two freshwater dams, one lagoon, and one estuary) in order to evaluate the use of these variables as markers of habitat. The pattern of the Sr:Ca ratio in the water agrees with the one found in the otoliths, showing a positive relationship with the conductivity of the water. Univariate and multivariate analyses of variance indicated significant differences (P < 0.05) among the localities studied for the morphometric indices. The discriminant function analysis provided a high percentage of correctly classified individuals for the saltwater environment (100%) and the lentic water bodies and estuary (60-80%), circularity and form factor being the most relevant morphometric variables. These results indicate that the Sr:Ca ratio and otolith morphometry are good markers of habitat for this important resource.

Resumen: El pejerrey Odontesthes bonariensis es una especie eurihalina nativa de Sudamérica y representa un importante recurso pesquero para la cuenca del Plata (Argentina y Uruguay). En este estudio se comparó la relación Sr:Ca del agua y la relación Sr.:Ca y morfometría de los otolitos sagittae de pejerreyes presentes en diferentes ambientes (un lago de agua salada, dos embalses de agua dulce, una laguna y un estuario) con el objetivo de evaluar el uso de estas variables como marcadores de hábitat. El patrón de la relación Sr:Ca del agua concuerda con la hallada en los otolitos, mostrando una relación positiva con la conductividad del agua. Los análisis univariados y multivariados indicaron diferencias (P < 0.05) entre las localidades estudiadas para los índices morfométricos. El análisis discriminante mostró un elevado porcentaje de individuos correctamente clasificados para el ambiente de agua salada (100%), los cuerpos de agua lenticos y el estuario (60-80%), siendo la circularidad y el factor de forma los índices morfométricos de mayor relevancia para esta clasificación. Estos resultados indican que la relación Sr:Ca y la morfometría del otolito son buenos marcadores de hábitat para este importante recurso.

Arsenic (As) is a natural toxic present in groundwater and surface water. This study estimated the risk of ingestion of high As concentrations present in groundwater for a rural population in Buenos Aires Province. The presence of As in soft tissues of silverside (Odontesthes bonariensis) was also considered as an additional source of As exposure, which is the native species of major commercial importance. Arsenic concentration was determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In water samples As concentrations were found in the range of < 10-170 µg/l, in fish muscle the concentration range was between 0,29 to 8,41 µg/g, and in liver between 0,24 to 8,98 µg/g, of dry weight. The endemic regional chronic hydroarsenicism Argentino (ERCHA), a disease caused by consumption of varying As concentrations during a long time, generates different skin pathologies. The risk estimated for groundwater intake in this rural population at all sites studied exceeded the accepted value of maximum individual risk (10-5), according to United States Environmental Protection Agency (USEPA). As concentration in fish tissues, could be shown transference of this element to different organs, being harmful for human consumption.

El arsénico (As) es un tóxico natural presente en aguas subterráneas y superficiales. En este trabajo se estimó el riesgo por ingesta de agua subterránea con elevadas concentraciones de As para pobladores rurales bonaerenses. Además se consideró una fuente adicional de exposición a la presencia de As en tejidos blandos del pejerrey (Odontesthes bonariensis), que es la especie nativa de mayor importancia comercial. La concentración de As se determinó por espectroscopía de emisión atómica por plasma de acoplamiento inductivo (ICP-OES). En las muestras de agua subterránea las concentraciones se hallaron en el rango de < 10-170 µg/l, mientras que en músculos de peces estuvo comprendida entre 0,29-8,41 µg/g y en hígado entre 0,24-8,98 µg/g (en peso seco). El hidroarsenicismo crónico regional endémico Argentino (HACREA), enfermedad que se origina por el consumo de cantidades variables de As en un largo período de tiempo, genera diferentes afecciones de piel. El riesgo estimado por ingesta de agua subterránea en todas las localidades estudiadas superó el valor aceptado de riesgo individual máximo (10-5), según la Agencia de Protección Ambiental de los Estados Unidos (USEPA). Los niveles de As hallados en tejidos de peces, sugieren que existiría transferencia de este elemento desde el agua a los distintos órganos, que podría resultar perjudicial para el consumo humano.

The South American sea lion, Otaria flavescens (Shaw, 1800) population is steadily expanding along the Patagonian coast of Argentina in the last decades. However, little is known about the feeding ecology of the species in the area. The aim of this study was to analyze the food habits of O. flavescens from 91 scats collected at Río Negro province, during the winter and spring of 2005. Fish occurred in 96% of scats containing prey remains, followed by cephalopods (26%). Raneya brasiliensis (Kaup, 1856) was the most frequent and abundant species occurring in 58.6% of samples and constituting almost 50% of fish predated. Second in importance were Porichthys porosissimus (Cuvier, 1829) and Cynoscion guatucupa (Cuvier, 1830) in terms of occurrence (%FO 20.7) and numbers (29.6%) respectively. The squid Loligo gahi (d'Orbigny, 1835) was the most frequent cephalopod prey (42.1%), whereas Octopus tehuelchus (d'Orbigny, 1834) was the most abundant (77%). The higher amount and diversity of prey found in the spring in comparison with the winter season might be related to a higher feeding activity of seals or to a seasonal increase in food availability in the area.

La población del lobo marino de un pelo sudamericano Otaria flavescens (Shaw, 1800) ha experimentado un crecimiento continuo en las ultimas décadas en las costas de la Patagonia Argentina. Sin embargo, poco se conoce sobre la ecología trófica de la especie en el área. El objetivo de este estudio fue analizar los hábitos alimentarios de O. flavescens a partir de 91 fecas colectadas en la provincia de Río Negro, durante el invierno y la primavera del 2005. Los peces estuvieron presentes en el 96% de las fecas que contenían remanentes presas, seguidos por los cefalópodos (26%). Raneya brasiliensis (Kaup, 1856) fue la especie mas frecuente y abundante ocurriendo en el 58.6% de las muestras y constituyendo casi el 50% de los peces predados. Le siguieron en importancia Porichthys porosissimus (Cuvier, 1829) y Cynoscion guatucupa (Cuvier, 1830) en términos de frecuencia de ocurrencia (%FO 20,7) y abundancia numérica (29,6%) respectivamente. El calamar Loligo gahi (d'Orbigny, 1835) fue el cefalópodo presa mas frecuente (42,1%), mientras que Octopus tehuelchus (d'Orbigny, 1834) fue el mas abundante (77%). La mayor cantidad y diversidad de presas observada en primavera en comparación con el periodo invernal podría estar relacionada a una mayor actividad de forrajeo de los lobos o a un incremento en la disponibilidad de presas en el área.