Marlucy Coelho Claudino

Feeding ecology and prey preferences of a piscivorous fish in the Lagoa do Peixe National Park, a Biosphere Reserve in Southern Brazil

We investigated the diet, feeding strategy, size-related dietary shifts and prey preferences of South American Hoplias aff. malabaricus in an internationally recognized but poorly investigated Biosphere Reserve in southern Brazil. Fish were caught between April 2008 and March 2009 using a variety of fishing gear. The analysis of 113 individuals revealed a diet essentially composed of fish (16 species), particularly characid species (9). The diet became more diverse and contained larger fish prey with increasing predator size. Feeding strategy analysis revealed a clear specialization towards the consumption of fish. However, individuals did not prey upon particular prey species, instead opportunistically consuming many different fish species, which could be a strategy to avoid intraspecific competition. Characid species were the most important prey, followed by poecillids. A multi-gear sampling of the ichthyofauna revealed that these prey species were the most abundant (Characidae: 61.3%, Poeciliidae 18.8%) of the 14 fish families occurring at the study site, suggesting that the predator exploits the most abundant fish resources available rather than the rarer fish prey. These findings suggest that potential top-down controls exerted by H. aff. malabaricus in this system follow specific food web pathways that seem to be mediated by the abundance of prey resources.

The activity patterns and microhabitat use of Pseudis minuta Günther, 1858 (Anura, Hylidae) in the Lagoa do Peixe National Park, a biosphere reserve of the brazilian subtropics

Pseudis minuta is abundant in a variety of aquatic environments of the Pampa domain. Therefore, it can be considered a good model for testing hypotheses on environmental heterogeneity and the influence of climate on the activity of anurans. In this study, we examined the spatial distribution pattern of P. minuta in terms of microhabitats and the influence of abiotic factors on seasonal fluctuations in the abundance of this species. Samples were collected monthly from April 2008 to May 2009 in wetlands and coastal dunes in the Lagoa do Peixe National Park. A total of 112 specimens of P. minuta were collected, of which 45 were found in the wetland area and 67 in the dune area. The species showed seasonal fluctuation in abundance, and it was most abundant in months with higher temperatures (spring-summer). Pseudis minuta was mainly associated with aquatic vegetation, an expected pattern in terms of their morphological adaptations to this environment. Among the abiotic parameters analyzed, only the monthly mean temperature showed a significant correlation (p < 0.05; r = 0.67) with the abundance of P. minuta. We concluded that P. minuta is a generalist species with respect to microhabitat use and also that fluctuation in its population abundance is mainly associated with seasonal variation in temperature.

Temporal variability in assimilation of basal food sources by an omnivorous fish at Patos Lagoon Estuary revealed by stable isotopes (2010–2014)

ABSTRACT Estuarine systems are characterized by complex physicochemical and hydrological changes occurring across multiple scales, which determine spatiotemporal variation in distribution and abundance of consumers and their resources. However, little is known about the effects of these biophysical interactions on the interannual dynamics of estuarine food webs. In this work, a five-year stable isotope data set was used to investigate interannual variability in trophic links between basal production sources (seagrass, macroalgae, saltmarsh, particulate organic matter in suspension and in the sediment) and an omnivorous fish (Jenynsia multidentata) in a subtropical estuary emptying in the Southwestern Atlantic. The isotopic variability (δ13C, δ15N) of basal sources and the consumer was analysed seasonally on a mudflat from 2010 to 2014. Jenynsia multidentata showed significant interannual variation in their trophic links with primary producers. In most seasons and years, the consumer relied heavily on benthic-associated food resources, but shifted to pelagic food resources during certain seasons. A ‘green tide’ caused by a massive bloom of vicariant macroalgae occurred on the mudflat, but our findings suggested that the carbon-derived portion of this basal production source was not assimilated by J. multidentata. Instead, seagrass was the most assimilated benthic basal food source in most seasons and years. These results suggest that the intensity of benthic and pelagic trophic pathways sustaining estuarine consumers are not static, but change in response to intra- and interannual variation in the availability of basal production sources. Our findings reinforce the need to account for interannual trends in availability of resources when modelling estuarine food web dynamics.

Pisces, Cyprinodontiformes, Rivulidae, Austrolebias minuano (Costa and Cheffe, 2001): new species record at Lagoa do Peixe National Park, state of Rio Grande do Sul, Brazil

Austrolebias minuano (Costa and Cheffe 2001) (Figure 1) is a annual fish belonging to the Rivulidae family that is comprised of approximately 235 species, from which 16 are endemic to Patos Lagoon drainage basin (Costa 2003). They inhabit temporary pools or swamps formed at the rainy season usually during winter months in southern Brazil (Costa 2006, Porciuncula et al. 2006). Adults die when ponds dry out during warmer months, but they leave their eggs buried into the sediment, where they remain in diapause until a new rainy season restores water levels in their habitats (Costa 2006). Austrolebias minuano is one of the species of the A. adloffi species group, which is characterized by a pair of black spots arranged vertically in close proximity, which can coalesce to form an 8-shaped blotch, on posterior portion of caudal peduncle in juveniles and adult females, and sometimes in adult males (Costa 2006). It can be distinguished by a combination of several characters, being among them, a black bar on parietal series of neuromasts, dorsal and anal-fin bases with elongated white spots, anterior flank bars about as wide as interspace and posterior bars wider (Costa op cit.). This species is considered endangered, especially due to expansion of increasingly urbanization and agriculture activities, which drastically alters and/or permanently disrupt their habitats (Fontana et al. 2003; Rosa and Lima 2008).

Pisces, Gymnotiformes, Hypopomidae, Brachyhypopomus draco (Giora, Malabarba and Crampton, 2008): new species record at Lagoa do Peixe National Park, state of Rio Grande do Sul, Brazil

The present paper describes a new occurrence of the species Brachyhypopomus draco in a wetland area of the Lagoa do Peixe National Park, state of Rio Grande do Sul, Brazil.