Renato Bolson Dala-Corte

Biologia reprodutiva de Astyanax henseli (Teleostei, Characidae) do curso superior do Rio dos Sinos, RS, Brasil

No presente estudo e descrita a biologia reprodutiva de uma populacao de Astyanax henseli Melo & Buckup, 2006 do curso superior do rio dos Sinos, Caraa, Rio Grande do Sul, Brasil. Foram analisados 336 exemplares, sendo 169 machos, 154 femeas e 13 cujo sexo nao foi possivel ser determinado. O periodo reprodutivo teve aproximadamente cinco meses de duracao, ocorrendo entre agosto e dezembro, com pico do indice gonadossomatico (IGS) em outubro, correspondendo ao final do inverno e a primavera no hemisferio sul. Nao houve correlacao estatisticamente significativa do IGS com os fatores abioticos (temperatura, precipitacao e fotoperiodo). No entanto, sugere-se que estes fatores estejam atuando como desencadeadores da maturacao gonadal. Fatores bioticos como o indice de replecao estomacal (IR) e indice hepatossomatico (IHS), tambem nao mostraram correlacao estatisticamente significativa com o IGS. Apesar disso, os valores de IR indicam que A. henseli continua se alimentando ativamente durante o periodo reprodutivo, enquanto que os baixos valores de IHS durante do pico reprodutivo sugerem um maior gasto das reservas hepaticas neste periodo. A proporcao sexual de 1:1 foi encontrada ao longo dos meses do ano, nas classes de comprimento e na populacao como um todo. O comprimento de primeira maturacao gonadal foi estabelecido em 69 mm para os machos e 60 mm para as femeas. A media da fecundidade absoluta foi de 3.038 ovocitos e a da fecundidade relativa 0,13 ovocitos mg-1. O desenvolvimento ovocitario indicou uma desova total.

Photo-identification as a technique for recognition of individual fish: a test with the freshwater armored catfish Rineloricaria aequalicuspis Reis & Cardoso, 2001 (Siluriformes: Loricariidae)

Photo-identification allows individual recognition of animal species based on natural marks, being an alternative to other more stressful artificial tagging/marking techniques. An increasing number of studies with different animal groups has shown that photo-identification can successfully be used in several situations, but its feasibility to study freshwater fishes is yet to be explored. We demonstrate the potential use of photo-identification for intraspecific recognition of individuals in the stream-dwelling loricariid Rineloricaria aequalicuspis . We tested photo-identification in laboratory and field conditions based on the interindividual variability in abdominal bony plates. Our test yielded high correct matches in both laboratory (100%) and field conditions (> 97%), comparable to other reliable techniques and to studies that successfully used photo-identification in other animals. In field conditions, the number of correct matches did not differ statistically between computer-assisted and naked-eye identification. However, the average time expended to conclude computer-assisted photo evaluations was about half of the time expended to conclude naked-eye evaluations. This result may be exacerbated when using database with large number of images. Our results indicate that photo-identification can be a feasible alternative technique to study freshwater fish species, allowing for a wider use of mark-recapture in ecological and behavioral studies.

Reproductive tactics and development of sexually dimorphic structures in a stream-dwelling characid fish (Deuterodon stigmaturus) from Atlantic Forest

The reproductive tactics of Deuterodon stigmaturus were investigated in this study, testing whether the species presents a seasonal or opportunistic life-history strategy in a high latitude Atlantic Forest stream in Brazil. The relation between the development of anal-fin spinelets (sexually dimorphic structures in characids) and the reproductive period of D. stigmaturus was also investigated. The species displayed a seasonal life-history strategy, with the reproductive period occurring between austral spring and summer. The reproductive period was related to increase in temperature and photoperiod, corroborating several studies that suggest positive relation between seasonal reproduction and abiotic predictability. The data indicated total spawning occurring in January, coinciding with the month of greatest rainfall (historical and in the study year). However, the observation of postovulatory follicles in previous months suggests small spawning before January. The development of spinelets on the anal-fin was the only sexual dimorphic trait between males and females. Contrasting with several other studies, seasonal development of anal-fin spinelets was observed in adult males, following the reproductive period and regressing afterwards. Thus, some characid species probably retain this structure throughout the year and others do not, which may be related to life-history strategy differences.

Relation between species richness and stream slope in riffle fish assemblages is dependent on spatial scale

Channel slope is an important variable in lotic systems because it mediates flow. However, stream slope can be measured at various spatial scales and the relation with fish assemblage characteristics may be scale dependent. In this study we investigated the influence of stream slope measured at different spatial scales on fish species richness. We tested three hypotheses: 1) the relation between slope and species richness will be dependent on the spatial scale at which slope is measured; 2) species richness will be inversely related to mean stream slope; 3) species richness will be positively related to stream slope variability. We sampled riffle fish assemblages in 21 streams in southern Brazil. For each stream we measured slope at five different scales and calculated mean slope and slope variation. The influence of slope on local species richness was tested by simple regression analysis using rarefied richness as response variable. We found that the relation between slope and species richness was scale-dependent, because only slope at the whole stream channel was significantly related to species richness. We also observed that steeper streams tended to have less slope variability and lower species richness. These results suggest that processes occurring at the whole stream scale are determinant for local fish species richness. More importantly, they reinforce the need to measure slope at different scales when investigating fish-habitat relations in streams, because the influence of slope may not be detected if assessed at only one scale. We suggest that assessing mean slope and slope variability at different scales should be considered in sampling design of research and conservation aimed at stream fishes.

Diet-morphology relationship in the stream-dwelling characid Deuterodon stigmaturus (Gomes, 1947) (Characiformes: Characidae) is partially conditioned by ontogenetic development

Nos testamos se variacoes na composicao da dieta de uma populacao de Deuterodon stigmaturus podem ser explicadas por diferencas morfologicas entre individuos, e se as relacoes entre morfologia e dieta sao dependentes do desenvolvimento ontogenetico. A dieta de 75 individuos amostrados em um riacho costeiro do sul do Brasil foi analisada. Uma Analise de Coordenadas Principais (PCoA) foi utilizada para sumarizar variacoes individuais no conteudo estomacal. Os eixos retidos da PCoA foram testados como resposta ao comprimento padrao (CP) e ao comprimentos do intestino (CI) e da boca (CB), independentes do tamanho corporal, usando modelos lineares mistos (LMMs). Os itens macroscopicos mais consumidos por D. stigmaturus foram algas filamentosas (41%), plantas terrestres (20,3%), detritos (12%), e invertebrados terrestres (8,8%). Os LMMs mostraram que o CP foi positivamente relacionado ao consumo de plantas terrestres, enquanto que valores de CI independentes de CP foram negativamente relacionados ao consumo de invertebrados aquaticos e positivamente relacionados ao consumo de algas filamentosas. Quando o CP foi mantido constante, CB nao foi relacionado a composicao da dieta. As diferencas na dieta condicionadas ao tamanho corporal sugerem que os individuos mudam seu nicho trofico e funcao no ecossistema ao longo do desenvolvimento ontogenetico. As relacoes entre o tamanho do intestino e composicao da dieta sugerem diferencas individuais na habilidade de forragear e digerir itens alimentares distintos.

Riparian integrity affects diet and intestinal length of a generalist fish species

Human activities in the riparian zone can affect the feeding of stream fish because they alter autochthonous production (periphyton, macrophytes and aquatic insects) and allochthonous inputs (terrestrial insects, leaves, seeds and fruits). In the present study we investigated how the diet and intestinal length of a persistent and generalist fish species (Bryconamericus iheringii, Characidae) responds to riparian modifications in 31 subtropical streams in southern Brazil. We hypothesised that intestinal length would be longer in populations inhabiting streams with converted riparian vegetation as a consequence of greater consumption of an indigestible and low-protein diet. Populations of B. iheringii from streams with a degraded riparian zone and reduced canopy cover had longer intestinal length (after accounting for body size), which was associated with decreased consumption of terrestrial plants and invertebrates and increased ingestion of filamentous algae, macrophytes and detritus. These results indicate that anthropic alteration of riparian zones and increased canopy openness trigger shifts in the diet and intestinal length of B. iheringii. The findings suggest that plasticity in intestinal length is an important characteristic to determine whether fish populations can persist in a variety of habitat conditions and cope with the digestion of a greater proportion of low-quality and low-protein food items in human-altered environments.

Birds of two protected areas in the southern range of the Brazilian Araucaria forest

Over 70% of threatened birds in the state of Rio Grande do Sul, south Brazil, inhabit forest environments. The creation and maintenance of protected areas is one of the most important measures aiming to mitigate these problems. However, the knowledge of the local biodiversity is essential so that these areas can effectively preserve the natural resources. Between 2004 and 2009 we sampled the avifauna in two conservation units in Rio Grande do Sul: Floresta Nacional de Canela (FNC) and Parque Natural Municipal da Ronda (PMR), both representative of the Mixed Humid Forest (Araucaria Forest). A total of 224 species was recorded, 116 at FNC and 201 at PMR, ten of which threatened regionally: Pseudastur polionotus, Odontophorus capueira, Patagioenas cayennensis, Amazona pretrei, A. vinacea, Triclaria malachitacea, Campephilus robustus, Grallaria varia, Procnias nudicollis and Sporophila melanogaster. Richness and species composition seem to be related to different stages of forest conservation, to size and connectivity, as well as to the diversity of environments. The better conservation of PMR compared to FNC, allied to its geographic position, results in a richer avifauna, with a larger amount of rare and endangered species, as well as species sensitive to disturbance and endemic to the Atlantic Rainforest. We suggest management actions aiming the conservation and the long-term recovery of natural environments at these sites.

Life history traits of Characidium pterostictum (Characiformes, Crenuchidae) along the longitudinal gradient of a Neotropical river in southern Brazil

Life history traits of Characidium pterostictum Gomes, 1947 (Characiformes, Crenuchidae) from three diff erent reaches of the upper Sinos river, southern Brazil, were described and comparatively analyzed according to the longitudinal gradient. For all reaches, results indicated a seasonal reproductive strategy with a higher intensity during warmer months of higher photoperiod (November to February). Only females were found in the upstream reach and they were more numerous than males in all the sampled reaches. Mean absolute fecundity ranged from 5,189 (±2,131 SD) to 7,394 (±3,807 SD), whereas mean relative fecundity (oocytes per mg of female total weight) ranged from 1.08 (±0.40 SD) to 1.12 (±0.29 SD). Oocyte development was characterized as synchronic in two groups, typical of total spawning. Longitudinal gradient comparison suggests that body size (standard length) of C. pterostictum individuals and sex ratio were the only characteristics that diff ered between sampled reaches. Larger individuals and thus females tended to be more frequently found in upstream reaches of the Sinos river, with a decrease in body size and in the proportional number of females towards downstream.

OCORRÊNCIA DE PEIXES NÃO-NATIVOS NO SISTEMA ESTUARINO- LAGUNAR DE TRAMANDAÍ, RIO GRANDE DO SUL, BRASIL

O presente trabalho tem como objetivo relatar novos registros de peixes nao-nativos no sistema estuarino-lagunar do rio Tramandai (SELT) e apresentar uma revisao das especies de peixes invasoras na Bacia Hidrografica do Rio Tramandai (BHRT), no litoral norte do Rio Grande do Sul, sul do Brasil. A ocorrencia das especies foi documentada a partir de fotografias fornecidas por pescadores locais e reportagens de jornais obtidas entre 2007 e 2008, alem da compilacao de trabalhos cientificos existentes na literatura. As especies registradas para o SELT foram: carpa-capim (Ctenopharyngodon idella), carpa-hungara (Cyprinus carpio), carpa-cabeca-grande (Hypophthalmichthys nobilis), carpa-prateada (H. molitrix) e uma especie de Serrasalmidae (cf. Piaractus mesopotamicus). Para a BHRT sao ainda relatadas na literatura: peixe-cachorro (Acestrorhynchus pantaneiro), piava (Leporinus obtusidens), tilapia-do-Nilo (Oreochromis niloticus) e porrudo (Trachelyopterus lucenai). A ocorrencia dessas especies na BHRT provavelmente esta associada a escapes acidentais ocorridos de tanques de piscicultura nos municipios vizinhos e tambem aos alagamentos dos campos de cultivo de arroz durante a epoca de chuvas. A introducao dessas especies nao-nativas representa uma ameaca potencial aos ecossistemas aquaticos de agua doce da regiao, podendo causar serios danos a diversidade local e a pesca artesanal. Em vista disso, e fundamental que seja realizado um completo mapeamento dos empreendimentos de piscicultura existentes na BHRT e que estas atividades sejam regularizadas e fiscalizadas. Com intuito de incentivar o cultivo de especies nativas e reduzir a chances de introducao de especies invasoras e importante tambem ampliar as atividades de assistencia tecnica aos piscicultores da regiao.