科研之友
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摘要
Limnoperna fortunei (Dunker, 1857), is an asiatic mussel that arrived in South America in 1991. Since 2004, we have noticed that the advance of this species in the lower Parana赤ba River, a tributary of the Upper Paran芍 River, is slow when compared to the average speed of 240 km/year in the Paran芍 River (middle and lower course). AIM: The goal of this work is to understand what factors are limiting the spread of L. fortunei in this stretch of the Parana赤ba River. METHODS: Its occurrence and dispersion were sampled twelve times between March 2006 and November 2007 in the Parana赤ba River, including the S o Sim o hydroelectric reservoir. Physicochemical characteristics of the water were analysed, and a Stream Length-Gradient Index calculated for the study area. RESULTS: Adult mussels were easily found attached to the hulls of barges that travel on this stretch of the Paran芍-Tiet那 waterway and on vessels that were docked in the harbours of grain exporters located in S o Sim o (GO). However, no larvae or adults were found near the harbours or upstream from them at the S o Sim o hydroelectric reservoir. The pH and concentration of calcium and dissolved oxygen values among lotic habitats and the reservoir were similar: DO values were close to 7 mg.L-1, the average pH was near 7, average values of total Ca ranged between 4 and 6 mg.L-1 and the chlorophyll-a levels were not restrictive to the mussel. CONCLUSION: Physical and chemical water parameters show that habitats were suitable for establishment of the mussel. In addition to a low pressure of propagules, this paper proposes some hydrological variables, such as the energy of the fluvial stretches, expressed by the Stream Length-Gradient Index and changes in flow downstream of the dam as barriers to the establishment of the species, discouraging larval settlement, and decreasing survival and recruitment. Limnoperna fortunei (Dunker, 1857), 谷 um molusco asi芍tico que chegou na Am谷rica do Sul em 1991. Desde 2004 verificamos que o avan o da esp谷cie no Baixo Rio Parana赤ba, afluente do Alto Rio Paran芍, 谷 lento quando comparado com a velocidade m谷dia de 240 km/ano nos cursos m谷dio e baixo do rio Paran芍. OBJETIVO: O objetivo deste trabalho 谷 entender quais s o os fatores limitantes da dispers o de L. fortunei neste trecho do rio Parana赤ba. M谷TODOS: Sua ocorr那ncia e dispers o foram amostradas doze vezes entre mar o de 2006 e novembro de 2007 no rio Parana赤ba, incluindo o reservat車rio da usina hidrel谷trica de S o Sim o. RESULTADOS: Mexilh es adultos foram encontrados aderidos aos cascos dos barcos que circulam neste trec
