Population structure of fishes from an urban stream / Estrutura populacional de peixes em riacho urbano

The aim of this study was to identify the population structure of the ichthyofauna in an urban stream within an environmental protection area in southern Brazil. Quarterly samplings were conducted between October 2009 and August 2010. Poecilia reticulata was the most abundant species, followed by Hypostomus ancistroides and Rhamdia quelen. It was found a higher proportion of adults instead of juveniles from P. reticulata and R. quelen populations, while the opposite was recorded for H. ancistroides. Sex ratio of 1:1 was found for H. ancistroides, but differed significantly for P. reticulata and R. quelen. Females of P. reticulata and R. quelen reached higher length than males in the smaller and higher length-classes, while H. ancistroides females were only longer in initial length-classes. It was recorded higher occurrence of mature and maturing individuals. Mature individuals of H. ancistroides were sampled in October, and P. reticulata and R. quelen throughout the sampling period. Despite adverse environmental conditions, the occurrence of juveniles indicates reproductive activity for these species. Population structure studies in degraded systems are urgent, since life-history features of species may suffer changes due to anthropic impacts. Providing such information contributes to decision making and management of degraded systems.(AU)

O presente estudo teve por objetivo identificar a estrutura populacional de espécies de peixes em um riacho urbano inserido em uma área de proteção ambiental no sul do Brasil. As amostragens trimestrais ocorreram entre outubro de 2009 e agosto de 2010. Poecilia reticulata foi a espécie mais abundante, seguida de Hypostomus ancistroides e Rhamdia quelen. Poecilia reticulata e R. quelen tiveram maior proporção de adultos em relação aos juvenis e o oposto foi observado para H. ancistroides. A proporção sexual de 1:1 foi encontrada para H. ancistroides, enquanto diferiu significativamente para P. reticulata e R. quelen. As fêmeas de P. reticulata e R. quelen alcançaram comprimentos superiores aos machos nas classes de comprimento iniciais e finais, enquanto para H. ancistroides somente nas classes finais. Os estágios reprodutivos registrados com maior frequência foram de maduros e em maturação. Os exemplares maduros de H. ancistroides foram amostrados em outubro, e de P. reticulata e R. quelen em todo o período de coleta. As características populacionais das espécies estudadas indicam que, a despeito das condições ambientais adversas presentes neste ambiente, a ocorrência de juvenis reflete atividade reprodutiva para estas espécies. Estudos de estrutura populacional em ambientes degradados são cada vez mais urgentes, uma vez que características da história de vida das espécies podem sofrer modificações frente aos impactos antrópicos. A disponibilização dessas informações contribui para tomada de decisões e manejo de ambientes impactados.(AU)

Reproductive strategies of fish populations from three Neotropical streams / Estratégias reprodutivas de populações de peixes de três riachos Neotropicais

This study aimed to characterize the reproductive strategies of fish from first order streams. Samplings were performed every three months from June 2008 to March 2009, using electric fishing at three streams: Conceiçمo, Scherer and Jurema, located in the municipalities of Diamante do Norte and Amaporم, Paranل State, Brazil. We obtained the total weight (g), standard or total length (cm), sex and maturation stage for each specimen. Limnological data were obtained with portable equipments. The minimum length at first maturation was established for each population, and reproduction period was determined by analyzing the distribution of maturation stages. The sex ratio was obtained and tested (X2) for significant differences. Eight species were analyzed and they responded differently to environmental pressures, reflected in the ratio between males and females, and in different reproductive strategies adopted. The streams were used as spawning ground in September and rest and recruitment areas in December and March, due to changes in the limnological parameters that signalize favorable periods for reproduction. We conclude that the protection provided by preserved riparian vegetation encourage the uptake of food by fishes and maintain their general physical characteristics, promoting the diversification in tactics found.(AU)

O presente estudo teve como objetivo caracterizar as estratégias reprodutivas de peixes de riachos de primeira ordem. Para tanto, foram realizadas amostragens trimestrais, de junho/2008 a março/2009, com uso de pesca elétrica em três riachos: Conceiçمo, Scherer e Jurema, situados nos municيpios de Diamante do Norte e Amaporم, Estado do Paranل, Brasil. Foram obtidos o peso total (g), comprimento-padrمo (cm) ou total (cm), sexo e estلdio de maturaçمo gonadal de cada exemplar. Variلveis limnolَgicas foram obtidas com o auxيlio de potenciômetros portلteis. Foi estabelecido o comprimento mيnimo de primeira maturaçمo para cada populaçمo, e o perيodo de reproduçمo foi determinado por meio da anلlise da distribuiçمo dos estلdios de maturaçمo gonadal. A proporçمo sexual foi obtida e testada (X2) quanto a diferenças significativas. Foram analisadas oito espécies e constatou-se que as espécies respondem de forma diferenciada às pressُes ambientais, refletidas na proporçمo entre machos e fêmeas e nas diferentes estratégias reprodutivas adotadas. Verificou-se que os riachos foram utilizados como لrea de desova em setembro e repouso e recrutamento em dezembro e março. Atribuiu-se, portanto, às variaçُes dos parâmetros limnolَgicos a sinalizaçمo dos perيodos favorلveis à reproduçمo. Concluiu-se que a proteçمo fornecida pela vegetaçمo ripلria preservada favoreça o aporte de alimento e a manutenção de suascaracterísticas físicas gerais, favorecendo a diversificação nas táticas encontradas.(AU)

Does a small forested area contribute to enhance species richness and diversity of fish assemblage at an urban stream? - doi: 10.4025/actascibiolsci.v35i4.16592

Conservation Units (CU) aim to contribute to the balance between human and environmental demand, by protecting natural resources and biological communities. In this study we examined the differences in the attributes of the fish community in four stretches of an urban stream, two inside and two outside the CU, without vegetation cover, and tested the hypothesis that the presence of riparian vegetation is positively reflected in the attributes of fish fauna. Five species were caught, distributed into four orders and five families. Attributes like richness, abundance, dominance, Shannon-Wiener diversity, and evenness were estimated and significant differences were detected for continuous stretches considering stream flow direction. The first stretches (URBI and UCI) presented a lower diversity that increased gradually until the last stretch, and an inverse result was found for dominance. These changes occurred regardless the location of the stretch, in- or outside the CU. The importance of Conservation Units within urban areas is severely affected by the lack of continuity of forested areas, especially riparian vegetation. Therefore, we suggest the effective recovery of permanent preservation areas and of riparian vegetation in order to mitigate the impacts of human activities.

Does a small forested area contribute to enhance species richness and diversity of fish assemblage at an urban stream? / Uma pequena área florestada contribui para aumentar a riqueza de espécies e diversidade da assembleia de peixes de um riacho urbano?

Conservation Units (CU) aim to contribute to the balance between human and environmental demand, by protecting natural resources and biological communities. In this study we examined the differences in the attributes of the fish community in four stretches of an urban stream, two inside and two outside the CU, without vegetation cover, and tested the hypothesis that the presence of riparian vegetation is positively reflected in the attributes of fish fauna. Five species were caught, distributed into four orders and five families. Attributes like richness, abundance, dominance, Shannon-Wiener diversity, and evenness were estimated and significant differences were detected for continuous stretches considering stream flow direction. The first stretches (URBI and UCI) presented a lower diversity that increased gradually until the last stretch, and an inverse result was found for dominance. These changes occurred regardless the location of the stretch, in- or outside the CU. The importance of Conservation Units within urban areas is severely affected by the lack of continuity of forested areas, especially riparian vegetation. Therefore, we suggest the effective recovery of permanent preservation areas and of riparian vegetation in order to mitigate the impacts of human activities.

Unidades de Conservação (UC) contribuem para o equilíbrio entre demanda humana e ambiental, protegendo recursos naturais e as comunidades biológicas. Neste contexto, o presente estudo investigou a existência de diferenças nos atributos da comunidade Ictiíca em quatro trechos de um riacho urbano, dois localizados no interior de uma UC e dois externos a ela, sem cobertura vegetal, testando a hipótese de que áreas vegetadas aumentam a diversidade e riqueza de espécies e diminuem a dominância em assembleias de peixes. Foram capturadas cinco espécies, distribuídas em quatro ordens e cinco famílias. Atributos como riqueza, abundância, dominância, diversidade de Shannon-Wiener e equitabilidade foram calculados e diferenças estatísticas encontradas para trechos contínuos considerando o fluxo do riacho. Os primeiros trechos (URBI e UCI) apresentaram menor diversidade, que foi gradualmente aumentando até o último trecho. Resultado inverso observado para a dominância. Estas mudanças ocorreram independentemente da localização do trecho, interno ou externo à UC. Concluiu-se que a efetividade de Unidades de Conservação em áreas urbanas é seriamente prejudicada quando da ausência de continuidade de áreas florestadas, em especial da vegetação ciliar. Sugere-se, portanto, a efetiva restauração das áreas de preservação permanente e da vegetação ciliar a fim de minimizar os impactos da ação antrópica.

Does a small forested area contribute to enhance species richness and diversity of fish assemblage at an urban stream? - doi: 10.4025/actascibiolsci.v35i4.16592

Conservation Units (CU) aim to contribute to the balance between human and environmental demand, by protecting natural resources and biological communities. In this study we examined the differences in the attributes of the fish community in four stretches of an urban stream, two inside and two outside the CU, without vegetation cover, and tested the hypothesis that the presence of riparian vegetation is positively reflected in the attributes of fish fauna. Five species were caught, distributed into four orders and five families. Attributes like richness, abundance, dominance, Shannon-Wiener diversity, and evenness were estimated and significant differences were detected for continuous stretches considering stream flow direction. The first stretches (URBI and UCI) presented a lower diversity that increased gradually until the last stretch, and an inverse result was found for dominance. These changes occurred regardless the location of the stretch, in- or outside the CU. The importance of Conservation Units within urban areas is severely affected by the lack of continuity of forested areas, especially riparian vegetation. Therefore, we suggest the effective recovery of permanent preservation areas and of riparian vegetation in order to mitigate the impacts of human activities.