Mauricio Cetra

Environmental influences on the distribution of arapaima in Amazon floodplains

This study investigated the environmental factors influencing the distribution of the endangered arapaima (Arapaima spp.) in floodplains of the Amazon. The abundance of arapaima was found to be positively related to the area and depth of the water column, and hence volume of lakes. Greater depth of water column also was related positively with the abundance and presence of arapaima in connecting channels. The abundance of arapaima was positively related to the connectivity of the lake with other water bodies. The principal reason for arapaima to prefer habitats that are deep, large, and connected to other water bodies appears to be increased survival through lower susceptibility to extreme drought events and increased mobility and availability of food resources. Deeper, larger, and more connected lakes and connecting channels sustain greater arapaima populations; they can now be used to prioritize conservation efforts.

Compartilhamento de recursos por duas espécies de peixes nectobentônicas de riachos na bacia do rio Cachoeira (BA)

O presente estudo teve como objetivo buscar particularidades e aspectos em comum relacionados com as condicoes ambientais de ocorrencia e recursos alimentares utilizados por Trichomycterus bahianus e Characidiumxa0 aff. zebra, duas especies tipicas de riachos coletadas durante o periodo chuvoso na bacia do rio Cachoeira, sudeste da Bahia, uma regiao da Mata Atlântica, utilizando-se um equipamento de pesca eletrica em oito trechos de riachos de cabeceira. Foi verificada a correlacao entre os dados ambientais e a abundância das especies, atraves de uma analise de componentes principais. Para os itens alimentares verificou-se a amplitude da dieta, a sobreposicao de nicho e a existencia de diferencas na exploracao dos recursos alimentares. Alem disso, testou-se a existencia de diferencas na composicao e no grau de preferencia alimentar em diferentes estagios de desenvolvimento. Foram coletados 55 exemplares de C. zebra e 124 de T. bahianus. Verificou-se que a abundância das duas especies esta relacionada com o gradiente graminea-rocha na margem e areia-matacao no fundo. Pode-se afirmar que independente da especie, as femeas foram maiores e mais pesadas que os machos (pxa0< 0,001). A proporcao sexual de C. zebra diferiu do esperado (Χ2 = 4,091; gl = 1; p = 0,043). As duas especies foram classificadas como invertivoras, consumindo principalmente formas imaturas de insetos aquaticos. Nao houve diferenca significativa no numero de itens consumidos pelas especies. A sobreposicao alimentar foi elevada (Oj,kxa0 = 0,895), porem, as especies apresentaram diferenca significativa na exploracao dos recursos alimentares (pxa0<xa00,001). Observou-se tambem que, apesar da alta sobreposicao alimentar, as especies exploraram praticamente os mesmos recursos, porem, com estrategias distintas. Isto foi evidenciado quando se levou em consideracao os diferentes estagios de desenvolvimento, mostrando que a dieta de C. zebra e mais generalista que a de T. bahianus. Provavelmente o compartilhamento de recursos abundantes e as diferencas na ocupacao de micro-habitats e nas estrategias de vida de C. zebra e T. bahianus, permita a coexistencia das duas especies nos riachos da bacia do rio Cachoeira durante o periodo chuvoso.

Local ecological and taxonomic knowledge of snapper fish (Teleostei: Actinopterygii) held by fishermen in Ilhéus, Bahia, Brazil

Local Ecological and Taxonomic Knowledge (LEK) of fish held by fishermen in the municipality of Ilheus, Bahia, Brazil, known as the snapper (“vermelho”) was examined from August 2005 to November 2006. Semi-structured interviews and tests were made with fishermen selected under the criteria of “specialists”. The data analysis followed the union model of the different individual competences. Grouping analysis was performed on data referring to the localities of the occurrence of these fish, depth, coloration, and morphological characteristics of the species using the Pearson correlation coefficient (UPGMA). A total of 19 species were named within the snapper group, although three of them could not be scientifically identified. The Lutjanidae family presented the greatest numbers of species (n = 9). Other families mentioned were: the Serranidae (n = 3), Holocentridae (n = 2), Priacanthidae (n = 1), Mullidae (n = 1). The 1:1 correspondence between fishermen’s local names and scientific species observed in this study indicates the richness of local fishermen knowledge. Analysis of the LEK related to the feeding habits of these fish and indicated that most were considered as being carnivorous, which agrees with the specialized literature consulted. In terms of their spatial distribution, two categories were detected: locality of occurrence (rivers/sea, coast, and offshore) and depth (surface, mid-depth, mid-depth/deep, deep). The fish were considered locally to be “winter fish”, based on harvested yields. Most of the interviewees knew little about the reproductive aspects of these fish. The main criteria used to identify, name, and classify the species were based on color and morphological aspects. Much of the information gathered in this study agreed with the published literature, which strengthens the importance of including LEK in planning and decisionmaking processes. Este estudo analisou o Conhecimento Ecologico Local (CEL) e taxonomico dos peixes conhecidos como vermelhos pelos pescadores no municipio de Ilheus, Bahia, no periodo de agosto de 2005 a novembro de 2006. Foram realizadas entrevistas semi-estruturadas e testes projetivos com os pescadores selecionados pelo criterio de “especialistas”. A analise dos dados seguiu o modelo de uniao das diversas competencias individuais. Foram realizadas analises de agrupamento para os dados referentes ao ambiente de ocorrencia, profundidade, coloracao e caracteristicas morfologicas das especies, utilizando o coeficiente de correlacao de Pearson (UPGMA). No total foram citadas 19 especies compondo o grupo dos vermelhos, sendo que tres nao foram identificados cientificamente. A familia Lutjanidae foi a que apresentou um maior numero de especies (n = 9). Outras familias encontradas foram a Serranidae (n = 3), Holocentridae (n = 2), Priacanthidae (n = 1) e Mullidae (n = 1). A correspondencia de 1:1 obtida entre as especies citadas pelos pescadores e a especie cientifica encontrada neste estudo indica um refinado detalhamento na identificacao e distincao. Analisando o CEL referente a alimentacao destes peixes, pode-se constatar que a maioria e carnivora, o que esta de acordo com a literatura especializada consultada. Para a distribuicao espacial foram detectadas duas categorizacoes: ambientes de ocorrencia (rio/mar, costeiro e alto mar) e profundidade (raso, meia-agua, meia-agua/fundo, fundo). Os peixes pesquisados foram considerados como peixes de inverno, afirmacao baseada na producao pesqueira. A maioria dos entrevistados desconhece os fatores relacionados com os aspectos reprodutivos. Os principais criterios utilizados para identificar, nomear e classificar as especies estao relacionados com a coloracao e aspectos morfologicos. Muitas das informacoes citadas neste estudo estao de acordo com a literatura especializada consultada, o que fortalece a importância e inclusao do CEL nos planos de manejo e na tomada de decisoes.

Fish fauna of headwater streams that cross the Atlantic forest of South São Paulo state

The fishes of the present study were collected in the headwater streams of the Sorocaba, Paranapanema and Ribeira de Iguape river basins during the dry period in 2010. A total of 2892 fishes, grouped in 53 species, were captured. The composition of the ichthyofauna captured in the streams of Sorocaba and Paranapanema river basin was greatly similar. On the other hand, the fish fauna of the streams of Ribeira de Iguape river basin were quite different from the ones captured in the others basins, with the occurrence of endangered species ( Isbrueckerichthys epakmos and I. duseni ) and exotic species ( Misgurnus anguillicaudatus ). The previous list of fish for the Sorocaba river basin increased with the addition of seven species of Characiformes, one Gymnotiformes and four Siluriformes.

Utilização de índices ecológicos em assembléias de peixes como instrumento de avaliação da degradação ambiental em programas de monitoramento

Este trabalho utiliza indices ecologicos em taxocenoses de peixes (constância de ocorrencia, diversidade de especies, riqueza, equitabilidade, indice de qualidade integrado (IQ)) como instrumento de avaliacao da degradacao ambiental. As amostragens foram padronizadas e realizadas sazonalmente durante dois anos, com rede de arrasto do tipo picare, em onze pontos da bacia hidrografica do lago Guaiba. Os pontos que apresentaram maior regularidade sazonal nos indices coincidem com locais de melhor qualidade ambiental indicados por outros fatores (frequencia de anomalias, DBO5, temperatura, coliformes totais, oxigenio dissolvido). O calculo do indice de qualidade integrado (IQ), entretanto, foi extremamente influenciado pela abundância e riqueza de especies, sendo que os locais considerados de melhor qualidade por este indice correspondem aos de pior qualidade ambiental indicados por outros fatores. A analise realizada demonstrou que a medida que a qualidade da agua melhora, o Indice de Margalef diminui. Isto demonstra que mesmo havendo uma melhora na qualidade da agua, nao houve uma melhora da estrutura da comunidade deste local.

Responses of the ichthyofauna to urbanization in two urban areas in Southeast Brazil

In this study, we evaluated the trophic structure and composition of the ichthyofauna in streams from non-urbanized and urbanized areas in two municipalities with approximately 30,000 inhabitants. We sampled fish fauna in nine pool-run stretches, four located in urban and five in non-urban areas. We adapted a physical habitat index (PHI) that summarized the physical attributes of the habitat, and a fish-based biotic integrity index (IBI) for the trophic structure of fish assemblage. Higher median scores of habitat parameters characterized non-urban stretches owing to better riparian vegetation and shading, bank stability and larger substrates. Diversity, richness and evenness indexes, as well as the abundance and biomass comparison (ABC), did not differ between urban and non-urban areas. The PHI was significantly correlated with the IBI and a non-metric multidimensional scaling (NMDS) analysis showed differences in the composition of the ichthyofauna. These results illustrated a common process in fish assemblages subjected to environmental impact, in which the generalist species replaced more specialist species, altering the species composition but maintaining a similar community structure. In general, the species responses were dependent on their trophic plasticity and foraging habitats. We showed that in a gradient of habitat alteration, species composition and thophic structure are better indicators of degradation than simple diversity indexes. We also discuss the implications of the urbanization in small towns toward changes in the species composition of freshwater fish, and the utilization of biotic and abiotic characteristics to document these changes.

Trophic organization and fish assemblage structure as disturbance indicators in headwater streams of lower Sorocaba River basin, São Paulo, Brazil

Studies that investigate the relationship patterns between environmental structure complexity and fish fauna provide crucial information to stream restoration efforts. In order to test the hypothesis that streams with more complex environmental structure sustain more diverse and functionally more complex fish communities we sampled fish fauna from Sorocaba River headwater stream reaches (SE - Brazil). Reaches represented two distinct treatments: (1) a simplified reach, characterized by unstable fine substrate, clay, deeper channel and higher water velocity and (2) structurally complex reaches, characterized by coarse substrate, with gravel, pebble, rock, stems and branches and leaves inside the channel, producing a diverse pattern of microhabitat, associated with sequences of pools, runs, and riffles. Both trophic structure and taxonomic composition varied significantly between treatments. Invertivorous trophic group exclusively occurred in structurally complex reaches, which also presented greater diversity and species richness. We suggest enhancing in-stream environmental structure that suffered simplification processes due to human impacts in order to reestablish fish communities and ecossistemic functioning.

First adult record of Misgurnus anguillicaudatus, Cantor 1842 from Ribeira de Iguape River Basin, Brazil

AIM: This work aimed to describe a first record of Misgurnus anguilicaudatus, Cantor 1842 in Sao Paulo state, as well as your potential impacts on native populations. METHODS: The specimen was caught by eletro-fishing device, in Itaguapeva river, Ribeira do Iguape river basin, Ibiuna (SP), Brazil. Later, it was fixed in 10% formalin and taken to laboratory for species identification, morphometric data evaluation, diet analysis and stage of gondal maturity. RESULTS: The individual was an adult female, without parasites and with gonads in maturity stage B, which indicates vascularized ovaries and presence of oocytes in vitellogenesis process. The dietary analysis showed that 95.3% of the stomach was occupied by insect larvae. CONCLUSIONS: The diet analysis may suggest food overlap and consequent competition for food with native species of the genera Trichomycterus e Characidium, which consume essentially the same items. Still, the great morphological similarity with native species, especially Siluriformes, could generate competition for shelters. Additionally, the stage of gonadal maturity and a recorded ability of the species on establish invasive populations in different environments raise concerns about the possibility of Misgurnus anguillicaudatus reproduction on the studied site.

Biology of Isopisthus parvipinnis: an abundant sciaenid species captured bycatch during sea-bob shrimp fishery in Brazil

Trawling is the most common method of shrimp harvesting. This technique causes a negative impact on the fauna due to thehigh bycatch rates and to the animals that are accidentally caught and generally returned to the sea dead. The consequencesof this technique and the biological aspects of the involved species are poorly studied, specially in the Brazilian northeast. Theobjective of this study was to show some aspects of the population biology of

Caracterização das assembléias de peixes de riachos de cabeceira no período chuvoso na bacia do rio Cachoeira (SE da Bahia, NE do Brasil)

Fish assemblage samples, environmental structure and water variables were collected from eight small streams in December of 2007 from Cachoeira river basin in the state of Bahia, Brazil. The objective was to obtain a set of information of the species richness and ecological aspects of the ichthyofauna. A thousand nine hundred and fifteen individuals of 19 species were captured. About half of the species contained individuals with a total length smaller than 50 mm. These findings suggest that some species are endemic. Two species with uncertain taxonomic status can be new. Confirmation of others two can represent expansion of the geographic distribution. These results indicate that new surveys in the area are necessary. Ordination analysis results with ambient data and abundance of the species showed significant correlation. Were identified three assemblages and it is suggested that were formed with extrinsic factors. Aiming to generate instruments for conservation programs and biodiversity monitoring species rare and dominant were defined.