Community structure of fish larvae in different biotopes of a neotropical river

Spatial heterogeneity is one of the major sources of compositional dissimilarity among fish in different biotopes. The availability and distribution of refuge, food, and habitats for breeding are determinants of the presence of fish species with different life histories, and understanding how this composition is organized along an environmental gradient is important for the protection of fish spawning sites and preservation of conditions that favor the dispersion and growth of their larvae. Thus, this study aimed to evaluate how the ichthyoplankton community is structured in different biotopes (river, lake, and transitional) of a fluvial system and to determine the factors involved in the structuring process. We conducted sampling in the lower Ivinhema River, upper Paraná River floodplain, Brazil, during two consecutive reproductive periods between 2010 and 2012. Larvae of long-distance migratory species were more related to the river biotope, while the non-migratory or short-distance migrators were more associated with transitional and lake biotopes. Therefore, our results indicate that the hydrodynamic conditions of the river, especially the flow velocity, as well as the parental reproductive guild, influence the distribution patterns of the ichthyoplankton community

Diet and trophic guilds of fish assemblages in two streams with different anthropic impacts in the northwest of Paran\ue1, Brazil

In the present study, we describe the diets of the fish assemblages in two streams in the Maringá region of Paraná that are under the influence of different anthropic impacts. We also evaluate how the origin and use of food resources varies temporally and spatially and how the trophic organization of the fish assemblages differs between the two streams. Fish were collected every two months from October 2006 to October 2007 using sieves, seining and closing nets along two 50 m stretches of each stream. We used the volumetric method to analyze the stomach contents of 599 fish belonging to 15 species. We then employed ANOSIM, SIMPER, NMDS and cluster analyses (using the Bray-Curtis index) to examine how different factors (species, stream, sampling site and season) influenced the diets of the assemblages. The dietary analysis revealed a total of 21 types of items consumed, with the most common being detritus and immature Diptera. Spatial factors resulted in differences in diets between the two streams, with detritus representing the material consumed most often in the Morangueiro stream and immature Diptera being the most consumed item in the Queçaba stream. SIMPER analysis indicated a 76.33% dissimilarity between species' diets during the dry and rainy seasons, with detritus, immature Diptera and testate amoebae making the greatest contributions to this differentiation. In the Morangueiro stream, three trophic guilds were found: detritivorous, detritivorous/aquatic insectivorous, and aquatic insectivorous. In Queçaba stream, six trophic guilds were present: detritivorous, benthophagous, aquatic insectivorous, terrestrial insectivorous, herbivorous and carnivorous. Autochthonous items were generally the items most consumed by species, in particularly in the Queçaba stream. In the Morangueiro stream, food items of indeterminate origin were more relevant. The differences in the diets of fish species between the two streams support the conclusion that urbanization causes the disruption of aquatic environments and trophic organization

Food-resource partitioning among fish species from a first-order stream in northwestern Paraná, Brazil

This study addressed the feeding ecology of fish fauna from a first-order stream located in a rural area. The purposes were to evaluate the influence of interspecific, seasonal and spatial factors on the diet, examine the dietary overlap, and determine the predominant food sources. Sampling was conducted in December 2007, September 2008, and March 2009, in three 50-m stretches of Itiz stream (upstream, intermediate, and downstream), through electrofishing. A total of 1,102 stomach contents were analyzed from 14 species, by the volumetric method. In general, allochthonous resources were predominant in the diets. Astyanax aff. fasciatus, Astyanax aff. paranae, Astyanax bockmanni, and Bryconamericus aff. iheringi consumed a higher proportion of plant remains, and Bryconamericus stramineus consumed predominantly Hymenoptera. The diets of Cetopsorhamdia iheringi, Characidium aff. zebra, Imparfinis schubarti, and Trichomycterus sp. consisted of aquatic insects, especially immature forms of Trichoptera, Ephemeroptera, Plecoptera, and Diptera. Hypostomus ancistroides, Hisonotus sp., Poecilia reticulata, and Rineloricaria aff. pentamaculata exploited mainly detritus, while Rhamdia quelen used a variety of items, predominantly terrestrial insects. Detrended Correspondence Analysis (DCA) showed a clear distinction among the species, with different morphology and feeding tactics. The Multi-Response Permutation Procedure (MRPP) supported this differentiation, and also indicated significant spatial and temporal variations in the dietary composition; the Indicator Value Method (IndVal) indicated the main items that contributed to these differences. The diet overlap among species was low (< 0.4) to around 78% of pairs, and the mean value did not vary significantly among the sites or between hydrological periods within each site. According to the null model of Pianka&#8217;s index, the values for dietary overlap were significantly higher than expected at random, showing evidence of resource sharing. This was related to the availability of allochthonous resources, highlighting the importance of riparian vegetation as a source of these resources for maintaining the fish fauna of the stream

Use of food resources by small fish species in Neotropical rivers: responses to spatial and temporal variations

Spatial and temporal variations in food supply play a crucial role in the determination of the patterns of food use by fish species. This study evaluated spatial and temporal variations in food utilization by small fish species of the Verde River, Upper Paraná River Basin, state of Mato Grosso do Sul, Brazil. Samplings were conducted in the rainy and dry periods, from November 2010 to August 2012, using trawls, cast nets and gillnets, in nine sampling sites grouped into three biotopes: upstream and downstream of the Branca Waterfall, and tributary. The stomach contents of 3,263 individuals of 12 small species were examined according to the volumetric method. Altogether, 31 food items were identified. Overall seed consumption was greater in the rainy period, and the consumption of terrestrial plants was greater in the dry period. Hymenoptera was an important item in the diet, but the proportions in the consumption of this item was different between biotopes and periods. The consumption of Coleoptera and Isoptera was expressive only downstream of the Branca Waterfall in the rainy period, and aquatic plant was mostly consumed in the tributary in the dry period. Significant differences were detected in the diet composition between biotopes, hydrological periods and also the interaction between these two factors. Allochthonous resources were clearly the most consumed by the species in all biotopes, especially during the rainy period. The dietary overlap between species, although showing significant spatial and temporal differences, was low (0.4) for about 60% of species pairs. Thus, it is concluded that spatial and temporal changes in the utilization of food resources by small fish were related to physiographic differences of the channel and the surroundings, which contributed to the significance of seasonal changes in the diet, also reflecting the low dietary overlap between species

Food-resource partitioning among fish species from a first-order stream in northwestern Paraná, Brazil

This study addressed the feeding ecology of fish fauna from a first-order stream located in a rural area. The purposes were to evaluate the influence of interspecific, seasonal and spatial factors on the diet, examine the dietary overlap, and determine the predominant food sources. Sampling was conducted in December 2007, September 2008, and March 2009, in three 50-m stretches of Itiz stream (upstream, intermediate, and downstream), through electrofishing. A total of 1,102 stomach contents were analyzed from 14 species, by the volumetric method. In general, allochthonous resources were predominant in the diets. Astyanax aff. fasciatus, Astyanax aff. paranae, Astyanax bockmanni, and Bryconamericus aff. iheringi consumed a higher proportion of plant remains, and Bryconamericus stramineus consumed predominantly Hymenoptera. The diets of Cetopsorhamdia iheringi, Characidium aff. zebra, Imparfinis schubarti, and Trichomycterus sp. consisted of aquatic insects, especially immature forms of Trichoptera, Ephemeroptera, Plecoptera, and Diptera. Hypostomus ancistroides, Hisonotus sp., Poecilia reticulata, and Rineloricaria aff. pentamaculata exploited mainly detritus, while Rhamdia quelen used a variety of items, predominantly terrestrial insects. Detrended Correspondence Analysis (DCA) showed a clear distinction among the species, with different morphology and feeding tactics. The Multi-Response Permutation Procedure (MRPP) supported this differentiation, and also indicated significant spatial and temporal variations in the dietary composition; the Indicator Value Method (IndVal) indicated the main items that contributed to these differences. The diet overlap among species was low (< 0.4) to around 78% of pairs, and the mean value did not vary significantly among the sites or between hydrological periods within each site. According to the null model of Pianka’s index, the values for dietary overlap were significantly higher than expected at random, showing evidence of resource sharing. This was related to the availability of allochthonous resources, highlighting the importance of riparian vegetation as a source of these resources for maintaining the fish fauna of the stream