Spatial and temporal variation of the ichthyoplankton in a subtropical river in Brazil |
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Authors: | David Augusto Reynalte-Tataje Angelo Ant?nio Agostinho Andrea Bialetzki Samara Hermes-Silva Rodrigo Fernandes Evoy Zaniboni-Filho |
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Institution: | 1. Laborat??rio de Biologia e Cultivo de Peixes de ??gua Doce (LAPAD), Universidade Federal de Santa Catarina, Rodovia SC 406, 3532, Arma??o, Florian??polis, Santa Catarina, Brazil, CEP 88066-000 2. N??cleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (Nupelia), Universidade Estadual de Maringa, Av. Colombo 5760, Bloco G-90, CEP 87020-900, Maringa, PR, Brazil 3. Laborat??rio de Ecologia Quantitativa, Universidade Federal Rural do Semi-Arido, Av. Francisco Mota 572, CEP 59625-900, Mossoro, RN, Brazil
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Abstract: | Studies that assess reproduction dynamics and ichthyoplankton distributions are scarce for the upper Uruguay River, especially
in environments such as tributary mouths. Therefore, this study aimed to evaluate: (i) ichthyoplankton composition; (ii) spatial
and temporal variation in ichthyoplankton abundance; and (iii) relationships between environmental variables and the abundance
of ichthyoplankton during one annual cycle in this region. Monthly samples were collected from September 2001 to August 2002
in 48 h cycles at 6 h intervals between each sampling. Samples of eggs and larvae were collected from three of the main tributaries
of the region (Ligeiro, Palomas and Chapecó rivers) and from three stretches of the Uruguay River near the confluence of these
tributaries. Surface samples were collected with a 0.5 mm mesh cylindro-conical net. In general, reproductive seasonality
was well-defined between October and February. It was most intense from November to January, when the photoperiod reached
its highest values, flow was decreased, and the water temperature was increased. Based on egg and larval distributions, we
found that spawning occurred mainly in the Ligeiro and Chapecó tributaries and in the Uruguay/Chapecó section. In contrast,
fish spawning in the sites downstream of dams was more restricted. Finally, a difference was observed between the egg and
larval distributions of the main river and its tributaries: the greatest reproductive activity in the tributaries occurred
during periods of high flow and increased water temperature, while in the main river, more eggs and larvae were observed when
the flow decreased and the water temperature increased. |
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