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Charybdis hellerii is an invasive swimming crab widely disseminated in the western Atlantic. This species became a threat to colonized ecosystems, competing with local species for resources. The extension of distribution and increasing population size of C. hellerii has been associated with the scarcity of indigenous predators and cases of predation report octopuses as the main native predators. In this study, we present the first evidence that native fish can consume C. hellerii. 53 individuals of the goldspotted snake eel, Myrichthys ocellatus, were collected at seagrass and macroalgal beds in Pernambuco State, Brazil, and had their stomach contents analyzed. Three juvenile C. hellerii were found along with native prey. Myrichthys ocellatus feeds mainly on small crabs, thus C. hellerii individuals were consumed before reaching sexual maturity. Oppositely to octopuses and other crab predators, M. ocellatus is of little fishing interest and is commonly found in macroalgae beds, seagrass meadows and sandy areas near reefs. Our results suggest that a higher number of carcinophagous taxa may prey on this invasive crab and we emphasize that the conservation of these species is paramount for controlling C. hellerii populations in invaded areas. [ABSTRACT FROM AUTHOR]

Data on the biology of Torpedo torpedo from the Ionian Sea are absent, and in the Mediterranean Sea, most of the published works focus on the reproductive biology of the species and are not recent. Several biological and ecological aspects of Torpedo torpedo were investigated between March and May 2019 on the coast of Sicily (Ionian Sea) between Avola and Marzamemi. Morphological (disc width–weight relationships, total length-disc width relationships), population (size-frequency distribution, sex ratio, fecundity), and ecological (habitat, diet) characteristics were studied. Stomach content analysis revealed that T. torpedo is a generalist piscivore, feeding on a wide variety of benthic and benthopelagic fish: Levin's index value (Bi) was 0.82. The analysis of the sex ratio showed a higher proportion of males vs. females. Females were, on average, larger than males. Fecundity showed a positive correlation with body size, with the smallest mature female being 14.9 cm in disc width and 24.8 cm in total length. The ovarian fecundity ranged from 3 to 20 eggs. In the study area, both adults and juveniles of the species were caught in considerable numbers with trammel nets. We also provide data from some specimens of Torpedo marmorata caught during the study period. [ABSTRACT FROM AUTHOR]

Paralichthys species have high commercial value and constitute a resource for demersal fisheries in the Southwestern Atlantic Ocean. Although six species have been described based on morphological characters for the Uruguayan and Argentinean waters, only the presence of three species is accepted, being their distribution still uncertain. Genetic tools are useful for species identification as a complement of morphological characters. This paper determines the genetic and morphometric variation between three species of Paralichthys that inhabiting Uruguayan waters. The interorbital width (IN) and the length from the mouth to the dorsal fin base (SD) of P. patagonicus differed significantly from the other two species (P. orbignyanus and P. brasiliensis). From a morphological perspective, individuals identified as P. orbignyanus formed two different groups. Clade Po_A included those belonging to oceanic coastal waters of Uruguay and deeper waters of the Rio de la Plata together with individuals of P. brasiliensis from ItajaÃ-, Santa Catarina (Brazil). Individuals collected in the Rio de la Plata coastal and beach zone formed the clade Po_B group. Genetic analysis confirmed for the first time the presence of P. brasiliensis in Uruguayan and Rio de la Plata shelf waters and extends its known distribution area further south. Discriminant scores for P. orbygnianus separate individuals in two groups corresponding to the presence of two species. Molecular and morphological analysis showed individuals in the clade Po_A includes those collected in Uruguayan waters together with those collected in northern Brazilian waters belonging to the species P. brasiliensis. [ABSTRACT FROM AUTHOR]

The introduction of exotic species is a key global threat to biodiversity. Beyond an increased risk of native species extinction, there exists a loss of biodiversity distinctiveness. Nevertheless, quantitative information on biotic homogenization at the taxonomic level in relation to basin features is rare. We used freshwater fish distribution data in Spain at three different time periods (1952, 1995, and 2007) to assess the species introduction process and the temporal dynamics of taxonomic homogenization among river basins in relation to basin size, native species richness and dam construction variables. The degree of alteration of original faunas by species introduction has increased through time, especially in native richer species, which suggest that the number of non-native and native species covariate with environmental heterogeneity. On the other hand, neither basin size nor habitat modification by dam construction seems to explain the number of introduced species. Our results indicate that the taxonomic homogenization of Spanish fish fauna is a temporally and spatially dynamic process; initial local increases in β-diversity through species introduction could be blurred because of scaling to regional and national levels or by the continuous expansion of a reduced number of exotic species. [ABSTRACT FROM AUTHOR]

Studies with annual fish diet have shown that the generalist habit is a dominant strategy within this group.Cynopoecilus fulgens(Cyprinodontiformes: Rivulidae) is a restricted range species, endemic to a small area in Southern Brazil, and aspects of its biology and ecology are poorly known. The main goal of the study was to determine the diet ofC. fulgensthroughout its life cycle and compare it with the prey availability in Southern Brazil wetlands. Specifically, we analyzed samples collected in different stages of ontogenetic development (immature and adult fishes) in various year seasons. A total of 52 food items were found in the diet ofC. fulgens, and invertebrates comprised 96.4% of the counts observed. The richness of consumed and available prey changed along with the seasons. The seasonal variation of the consumed prey richness was mainly related to increase in fish size along the annual cycle. Microcrustaceans represented 75.6%, 80.9%, and 68.4% of the consumed prey in autumn, winter and spring, respectively. Prey composition varied with the seasons and it was not correlated to prey availability. Diet selectivity was different among male, female and immature fish. Our study reported the feeding habits ofCynopoecilus fulgensto improve knowledge of the biological and ecological traits of annual killifishes in Southern Brazil wetlands, where more than 90% of the original wetlands have been lost due to agricultural expansion. [ABSTRACT FROM PUBLISHER]