Coastal seascapes are composed of diverse habitat types that significantly influence the composition and functional traits of several organisms, particularly fish, affecting their abundance and distribution. This study analyzes the taxonomic and functional diversity of fish assemblages in two coastal habitats of a wave-exposed sandy beach with differences in turbulence conditions: the surf zone (SZ) and the shallow subtidal zone (SSZ). Seasonal sampling was conducted over 1 year to assess these differences. Species richness, diversity, and mean abundance were higher in the SSZ (27 species; 466 ind/trawl) compared to the SZ (7 species; 52.5 ind/trawl). Assemblage dissimilarity reached 64

Dules auriga is a small, endemic and demersal species that occurs in the Southwest Atlantic Ocean (SWA). Knowledge of the trophic ecology of this species will be essential to understanding its role as predator in this marine region. The aim of this study was to determine the diet composition, feeding strategy, and trophic level of D. auriga in the coastal waters off Uruguay and northern Argentina (34 degrees degrees - 41 degrees S). degrees S). A total of 309 individuals ranging from 81 to 174 mm total length (TL) were analyzed. Dules auriga fed mainly on polychaetes (50.04 % prey-specific index of relative importance, %PSIRI), followed by amphipods (16.32 % PSIRI), brachyuran crabs (10.76 % PSIRI), and echinoderms (10.36 % PSIRI). Relationships between the number of prey and maturity stage, TL, region, and season were evaluated using a multiple hypothesis modeling approach. Echinoderms consumption was higher in the south region, whereas amphipods and polychaetes were higher in the north region. Brachyuran crabs were more consumed in the cold season. The consumption of echinoderms increased with increasing body size of D. auriga. . On the other hand, the consumption of amphipods decreased with body size. Polychaetes were more preyed by mature individuals than immature individuals. The size of the brachyuran crabs consumed not increased with increasing body size of D. auriga, , but it was registered a continued inclusion of narrow range size of this prey in the diet. The analysis of the feeding strategy indicates a specialization on polychaetes. The specific trophic level was 3.24, indicating that D. auriga is a secondary consumer. This comprehensive investigation enhances understanding of trophic dynamics of D. auriga, , providing a foundation for future ecological investigations in the SWA.

Benthic invertebrates in the surf zone of exposed sandy beaches represent important links for energy circulation between benthic and pelagic food webs. This work assesses the trophic ecology of co-occurring epi- and hyper-benthic invertebrates inhabiting the surf zone of sandy beaches located close to an estuarine mouth. It illustrates that different sources of organic matter induce changes in resource utilization. The trophic positions, and the niche width and overlap of species were described using δ13C and δ15N stable isotope analysis. The contribution of different sources to the particulate organic matter was quantified through stable isotopes analysis and fatty acids profiles. Shifts in the trophic niches of dominant species reflected a decrease in the contribution of estuarine carbon to the diets along the coast. This change in contribution of estuarine carbon also influenced trophic niche properties: more diverse resources availability resulted in narrower niches without overlap while less diverse resources resulted in broad isotopic niches and a highest overlap. Results show that spatial variations in the availability of resources can modify carbon pathways and trophic interactions in coastal food webs. Whenever resources are abundant, species display a more specialized diet while food scarcity leads to broader diets, a pattern consistent with the optimal foraging theory. This resource maximization behavior commonly observed in nature is also occurring in surf zone ecosystems.

Salt marshes do not present favourable conditions for cryptic fish species to inhabit these areas, mainly due to dryness and high temperatures at low tides, and scarce places to hide. Despite the harsh environmental conditions, we report, for the first time, the occurrence of two specimens of the half-naked goby Gobiosoma hemigymnum at high marsh, between oysters and Spartina alteniflora stems. In this paper we report evidence of a possible positive effect of autogenic ecosystem engineer and invasive species, the Pacific oyster (Magallana gigas), over the gobid, Gobiosoma hemigymnum, found 600 km away from its southernmost normal range.

This study explores the changes of biological descriptors -richness, diversity and abundance-of faunal surf-zone assemblage along a temperate coastal fringe. Three mesotidal sandy beaches with different morphodynamic states, adjacent to an estuarine zone, were seasonally sampled during a year. Zooplankton, zoobenthos and fish samples were taken in the surf-zone and a set of potential explanatory environmental variables were measured and/or quantified. Generalized linear models (GLM) were employed to compare environmental and biological variables between beaches and seasons. Beaches varied from tide-dominated flat to tide-modified reflective to intermediate. The assemblage included 108 taxa, of which few were numerically dominant. Richness of each biological group was similar along the shore and higher values of α-diversity were associated with minimum values of total abundance. β-diversity was mainly a consequence of species turnover, mostly due to changes in zoobenthic and zooplanktonic taxa. Results of GLM test showed that seasons and beaches have an interdependent effect on the abundance of the surf-zone assemblage. All biological groups showed marked seasonal variability in its occurrence, possibly associated with environmental variables, such as temperature and photosynthetic pigment concentrations. Zooplankton and fish groups reached maximum abundance, during autumn and spring respectively, in tide-modified beaches where the surf-zone was well developed and waves reached higher heights. Zoobenthic abundance peaked in beaches with narrower surf-zone and lower wave energy, during autumn, winter and spring, which could be advantageous for those taxa that escape from predators by burying or for species that actively swim near the seafloor. The copepod Acartia tonsa, the clupeidae fish Ramnogaster arcuata and the mysids Arthromysis magellanica and Neomysis americana all typical species of the neighboring estuary, were the main responsibles for these distribution patterns. The connection of the surf-zone with the adjacent estuarine area is also evident by its role in enriching the dissolved organic matter of surf-waters.

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of global concern in coastal environments. They have a wide range of biological toxicity and due to their inherent properties, can easily bioaccumulate in organisms and concentrate in the environment. This work evaluated, in an integrated way, the seasonal PAH distribution patterns in sediments and four bioindicators fish species in a highly impacted estuary of Argentina; besides, their bioaccumulation patterns were assessed for the first time as indicator of ecological risk. The highest PAH levels in fish were found for Ramnogaster arcuata with an average of 64 ng g-1 w.w., followed by Micropogonias furnieri (45 ng g-1 w.w.), Cynoscion guatucupa (28 ng g-1 w.w.), and Mustelus schmitti (16 ng g-1 w.w.). Fish presented the highest PAH levels in fall with a predominance of petrogenic PAHs in colder seasons and pyrolytic PAHs in warmer seasons. Sediments presented an average of 233 ng g-1 d.w. with the same seasonal composition pattern of the fish tissues. Additionally, the data suggested that the main source of PAHs are wastewater discharges. The bioaccumulation factor (BAF) of PAHs in the tested fishes were found to range from 0.3 to 8. The highest values were observed during fall and winter, while bioaccumulation did not occur in moist spring and summer samples, which would suggest a high biotransformation process during these seasons. Results suggested that class III of juvenile C. guatucupa and M. furnieri, and adults R. arcuata are more sensitive bioindicators of chronic PAH contamination and that their bioaccumulation is independent of the compound hydrophobicity; this could have a positively influence on the criteria used for biological monitoring programs along the Atlantic coast. In addition, the presented BAF data on the target species will serve as a useful pollution indicator for South Atlantic coastal fish.

The objective of the present work was to determine the age that reaches Cheirodon interruptus (Jenyns, 1842) in the Sauce Grande river basin, and to estimate its growth parameters. Sampling was performed seasonally by electrofishing, in three sites along the main river. A total of 164 individuals were caught, and total length (TL, mm) and weight (W, g) were recorded. The age was determined over a sub-sample of 154 fish, by means of scale reading. The growth parameters of von Bertalanffy’s equation were estimated using Least Squares method. Fish size ranged between 29 - 62 mm, with a mean of 44.73 mm (± 7.46). Mean TL by season was 38.17 mm (± 5.47) in summer, 43.25 mm (± 9.00) in autumn, 45.00 mm (± 5.10) in winter and 47.73 mm (± 6.45) in spring. Length-weight relationship for the total population was W = 6 x 10 -5 TL 2.61 (R 2 = 0.88). One annulus formation occurred yearly, at the end of autumn, assigning one year to each mark. Three age classes were determined (0 – 2), being age 0 the most abundant (84 %). The growth parameters for the total population were : L∞ = 57.63 mm; k = 0.69 y t 0 = -1.72.

El presente trabajo tiene como objetivo determinar la edad que alcanza Jenynsia lineata (Jenyns, 1842) en el rio Sauce Grande y estimar los parametros biologicos que describen el crecimiento. El material se obtuvo de capturas estacionales realizadas durante el ano 2000, en tres lugares de muestreo y mediante el empleo de pesca electrica. El numero de ejemplares analizados fue 169. La determinacion de la edad se efectuo mediante la lectura de escamas, y los parametros de crecimiento de la ecuacion de von Bertalanffy se estimaron mediante el metodo de Minimos Cuadrados. La poblacion muestreada presento un rango de tallas de 21 a 68 mm de Lt, con un promedio de 39,30 mm (± 9,28 ). La relacion largo peso estimada para el total de la poblacion fue y=9x10-6 x 3,14 (R2=0,93). Se determinaron cuatro clases de edad (0 a 3). Los parametros de la ecuacion de crecimiento estimados para la poblacion fueron : L∞ = 105,30 mm; k= 0,24 y t0 = -1,75.

El objetivo de este estudio fue determinar el hábito alimenticio de la ictiofauna del río Sauce Grande y analizar la superposición dietaria entre las especies. El estudio se llevó a cabo de enero a diciembre del 2000. Las pescas fueron efectuadas con frecuencia estacional, en tres estaciones de muestreo. Los métodos de captura empleados fueron pesca eléctrica y red de enmalle. En total se capturaron 656 individuos correspondientes a las siguientes especies: Bryconamericus iheringi, Cnesterodon decemmaculatus, Jenynsia multidentata, Cheirodon interruptus, Rhamdia quelen, Corydoras paleatus, Percichthys colhuapiensis, Oligosarcus jenynsii y Odontesthes bonariensis. De estas, P. colhuapiensis y O. bonariensis no pudieron ser incluidas en el estudio debido al bajo número de individuos registrados. La importancia de cada ítem alimentario para cada una de las especies fue estimada mediante la aplicación del índice alimentario (I.A.). Se analizaron 604 estómagos. El índice de vacuidad fue del 3%. Bryconamericus iheringi y J. multidentata fueron las únicas especies que presentaron una dieta omnívora, siendo las restantes calificadas como carnívoras. Bryconamericus iheringi, C. decemmaculatus, J. multidentata presentaron una superposición dietaria mayor al 66%. El ítem dominante fue la efemera Baetis inops. Una superposición dietaria moderada, entre 33 y 66% fue observada entre C. paleatus y B. iheringi, Ch. interruptus, C. decemmaculatus y J. multidentata. Las dos especies restantes con las demás especies presentaron solapamiento bajo con valores inferiores al 32%.

La laguna Cochicó es parte del sistema Encadenadas del Oeste (provincia de Buenos Aires, Argentina). Desde el año 2000, el estado municipal ha estado realizando tareas intensivas para complementar el stock pesquero del pejerrey (Odontesthes bonariensis) mediante la siembra y el control de la pesca furtiva, como parte de la estrategia para mejorar y proteger el recurso, a fin de lograr un aumento progresivo del stock de pejerrey y su calidad. El objetivo de este estudio fue evaluar la población de pejerrey de la laguna Cochicó y, en consecuencia, las políticas de manejo que se están implementando en este recurso. El muestreo se realizó durante tres meses, de abril de 2007 a marzo de 2008, utilizando redes de enmalle y una red de arrastre. La abundancia relativa en número se estimó con la captura de redes de enmalle. La captura por unidad de esfuerzo (CPUE) en peso se calculó considerando la noche de pesca como la unidad de esfuerzo. Se describió la estructura de tamaño de la especie dominante y se calculó el índice de densidad de población proporcional (PSD). Odontesthes bonariensis fue la especie dominante, con una abundancia relativa de más del 92%. La CPUE media fue de 201.6 kg / noche. Este valor fue mayor que el encontrado en años anteriores (19 a 120 kg / noche) utilizando la misma metodología. Los rangos de tamaño dominantes fueron 25-27 y 29-31 cm de longitud total (Lt). Los PSD fueron 71% y 40% para tallas con potencial de pesca recreativa y comercial, respectivamente. La calidad y abundancia actual de este recurso de pesca es esencial para la laguna Cochicó y es la razón por la que se ha convertido en uno de los lugares de pesca recreativa más prestigiosos de la Argentina.

The purpose of this study was to describe as well as to characterize the fish populations living in Del Monte lagoon, which belongs to the Encadenadas del Oeste system in the province of Buenos Aires, Argentina. This research was carried out using trammel nets with meshes of six different sizes at three sampling stations during October 2003. The species captured in the area of study were firstly identified. The specific diversity of each fishing site was subsequently estimated. In addition, sex ratio, size structure, and the relative abundance both in number and weight were also determined for each species. Total capture included 647 individuals, which corresponded to the following six species: mojarra Astyanax eigenmanniorum, dientudo Oligosarcus jenynsii, pejerrey Odontesthes bonariensis, carp Cyprinus carpio, sabalito Cyphocharax voga, and catfish Rhamdia quelen. The specific diversity was very similar at the three sampling stations. The mojarra Astyanax eigenmanniorum evidenced the highest relative abundance in number, it was followed by the dientudo Oligosarcus jenynsii and the pejerrey Odontesthes bonariensis. The highest ichthyomass corresponded to the carp Cyprinus carpio. The entrance of the latter to the Del Monte lagoon was corroborated, the highest number of samples was recorded near the outlet of Guaminí and Malleo-Leufú brooks. A marked decrease in the abundance of the pejerrey Odontesthes bonariensis as well as an increase in the number of the dientudo Oligosarcus jenynsii and the mojarra Astyanax eigenmanniorum were also observed.

The narrownose smoothhound (Mustelus schmitti) is the most exploited elasmobranch of Argentina, Brazil, and Uruguay and is considered endangered (IUCN Red List of Threatened Species). Providing information on age and growth can improve efforts for conservation of this species. Therefore, our objective was to provide accurate estimates of the age structure and growth parameters for narrownose smooth-hound from Anegada Bay, an important shark nursery area in Argentina. In vertebrae of narrownose smooth-hound, we observed a pattern of alternating opaque and translucent bands and a yearly periodicity in the deposition of this pattern. Ages determined from vertebral band counts ranged from 0 to 11 years. Calculated longevity and total natural mortality rates were 20.87 years and 0.19/year for females and 12.24 years and 0.26/year for males, respectively. This species reached a size of approximately 400 mm in total length in the initial year of growth, and the age at first maturity was 7.61 years for females and 6.79 years for males. The slow growth and late age at maturity of the narrownose smoothhound indicate a need for additional conservation measures to rebuild the population and achieve a sustainable fishery in the 3 countries in which it is distributed.

The diet and feeding strategy of Lepidonotothen nudifrons off the South Shetland Islands and the Antarctic Peninsula, as well as their variation in relation to ontogenetic stage (juvenile– adult) and sampling area, were determined by stomach contents analysis. Additionally, the trophic level of this species was estimated to determine its position within the Antarctic food web. Out of 247 specimens with prey in their stomachs, 144 were caught near the South Shetland Islands and 103 off the Antarctic Peninsula. Ontogenetic changes in the trophic ecology of L. nudifrons were observed in both areas and were mainly related to a decrease of copepods and an increase of euphausiids in the diet. The diet of juveniles from the South Shetland Islands was characterized by the dominance of calanoid copepods, followed by isopods and amphipods, whereas diet off the Antarctic Peninsula was dominated by amphipods and cyclopoid copepods. The diet in adults was dominated by amphipods and euphausiids in both areas. The specialization of individual predators on different prey types was observed when considering the whole population of L. nudifrons, but when ontogenetic stages were considered separately it showed a more mixed feeding strategy, with different dominant prey for each class. Although the trophic level increased with fish size, L. nudifrons can be classified as secondary consumer throughout its lifespan.

The aim of this study is to assess-for the first time-the concentration of the 16 polycyclic aromatic hydrocarbons (PAHs) in the muscle tissues of four fish species (Micropogonias furnieri, Cynoscion guatucupa, Ramnogaster arcuata, and Mustelus schmitti) from Bahía Blanca estuary, Argentina and to evaluate their sources, distribution, and the human health risks implicated. Considering the four species under study, mean total PAH concentrations showed the following decreasing accumulation trend: M. schmitti, R. arcuata, C. guatucupa, and M. furnieri. Low molecular weight PAHs, such as naphthalene and phenanthrene, were generally predominant, displaying properties of PAH mixtures generated from petrogenic pollution. Of the four fish species analyzed, M. furnieri was the only one that did not raise any human consumption warning. In the case of the other species, exceeding values were found above the safety human consumption guidelines. Nevertheless, the screening criteria for carcinogenic PAHs proposed by the USEPA indicated a good quality status for these fish species.

This study explores the relationship between ecomorphology and trophic segregation in four closely related sympatric fish species (Teleostei, Sciaenidae) that are known to differ in their trophic habits. Only adult specimens were analyzed: 103 Cynoscion guatucupa, 77 Pogonias cromis, 61 Micropogonias furnieri, and 48 Menticirrhus americanus. The four species presented divergent ecomorphological traits related to swimming agility, prey spotting and capture, and the potential size of prey they were able to swallow. Results suggest that these sciaenid species can partition the food resources, even though they completely overlap in space. Differences in their ecomorphological traits appear to correlate closely with the diet and consequently could explain the trophic differentiation observed. Arguably, these ecomorphological differences play a significant role in the coexistence of the adults of these sympatric fish species.

Chondrichthyans play an important role in structuring marine communities. Myliobatis goodie is an eagle ray reported from South Carolina in the USA (35°N) to Santa Cuz, Argentina (44°S), however little is known about this species, which is considered data deficient by the IUCN. In order to create adequate management strategies for this species, biological information is sorely needed. The objective of this study was to describe the biology of the population of M. goodei and its relationships with season, sex and the geographic features of Anegada Bay, Argentina (from 39.96°S to 40.60°S and from 62.10°W to 62.46°W) in 2008. Specifically, the population structure of M. goodie was studied by sex, seasons and sites, its food habits by seasons and sites, and the reproductive biology by seasons and sex. The results show that M. goodei exhibits seasonal migrations. Young-of-the-year remain in the bay all year long, while adults enter during spring and summer. Juveniles in spring are likely to become first-time mating individuals that migrate into open sea at the end of summer. These individuals would return to give birth for the first time and mate for the second time during the next year at summer. Anegada Bay would then be a mating and nursery area for the species. M. goodei behave as a generalist feeder with a uniform diet composed mainly of bivalves. Seasonal differences in the diet found arise from differences in prey diversity between summer and spring. Spatial differences, however, arise from the different abundances of caprellids and bivalves. Trophic level was 3.2 and it constitutes the first reference for this species, characterizing it as a secondary consumer.

Cynoscion guatucupa is one of the most important coastal fishery resources of Argentina and Uruguay, with both juveniles and adults being recorded in Mar Chiquita coastal lagoon, a shallow-water estuarine lagoon in Argentina. Cynoscion guatucupa enters and exits the lagoon following tidal cycles, with residence time within the lagoon lasting only for the duration of a tidal cycle. The main objectives of this study were to determine the diet composition of Cynoscion guatucupa captured in the lagoon, and to determine if different size-classes of this species differentially utilize available food resources during their residency within the coastal lagoon. The diet of 511 specimens of C. guatucupa was analysed. The most important prey item in %IRI was Peisos petrunkevitchi, followed by juvenile teleosts including those of Micropogonias furnieri, Odontesthes argentinensis and Mugil platanus. Cynoscion guatucupa enters the lagoon to feed on a variety of invertebrates as well as juvenile teleost fishes. Diet composition showed ontogenetic changes: smaller individuals predominantly consume crustaceans, and as size increases they begin to prey more on teleosts, with the largest fishes specializing on fish. The present study reinforces the role of estuaries for marine fishes as both feeding grounds for juveniles and adults and as refuge areas for juveniles. Furthermore, this study also highlights the importance of food habit studies for understanding the trophic ecology of fishes and estuarine food web dynamics.