Author(s): J. M. Santos; P. J. Pinheiro; M. T. Ferreira; J. Bochechas
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Abstract: By means of recent infrared technology, the Riverwatcher System (RW), upstream movements of coarse fish were monitored in a pool-and-weir fish pass on the River Zezere, central Portugal, for 141 days from June 2002 to May 2003. More than 3000 individual Iberian nase Pseudochondrostoma polylepis (Steindachner, 1864) ascended the fish pass and moved through the RW during the study period. However, only 18% of the records produced by the RW contained silhouettes similar to fish; no individual smaller than 15 cm TL was recorded by the counter. Most seasonal movements (73.9%) occurred in spring and were associated with reproduction. Displacements seemed to occur independently of time of day. Further development of hardware and software will be necessary to improve performance of the counter, particularly in Mediterranean rivers, where more turbid waters and a greater proportion of small-size species are present.
Year: 2009