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 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.

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.