Efficacy of a nature-like bypass channel in a Portuguese lowland river

Abstract

Summary Throughout Europe in the last decade there has been a steady shift away from more technical fish pass designs to more nature‐like passes, such as nature‐like bypass channels. Upstream fish passage in a nature‐like bypass channel was investigated in a lowland river, the Lima River, for 117 days from March 2000 to May 2002. Fish passage was recorded using an automatic video recording system. Electrofishing samples within the bypass and below the weir were compared with species abundance found on the tape recordings. More than 7500 individuals of eight species passed through the bypass channel. Species composition was dominated by striped mullet (65.3%) and potamodromous species (34.3%), which used the bypass mainly at night. Of the environmental variables considered, bypass discharge explained most of the variation in the number of cyprinids, whereas water temperature was more important for diadromous species. Comparing species composition below the weir using passage recordings provided a useful tool to assess species efficacy of the bypass, although biological requirements should also be taken into account. This study proved the efficacy of the bypass for passage of almost all occurring species and life stages and also for providing suitable habitat for fish fauna, highlighting the use of these facilities for river restoration schemes.

Seasonal and daily upstream movements of brown troutSalmo truttain an Iberian regulated river

“…The greatest number of fish movements were recorded during autumn and winter, which is in agreement with others studies carried out in the Iberian Peninsula (Santos et al, 2002(Santos et al, , 2005Ordeix et al, 2011). Solar radiation, water temperature and flow were the major environmental variables associated with these movements.…”

“…However, the dates and environmental triggers of the spawning movements in the Iberian Peninsula for potamodromous populations have not been sufficiently studied. Only fishway evaluations in Iberian rivers have registered upstream movements in movements in autumn and winter (Santos et al, 2002(Santos et al, , 2005Ordeix et al, 2011), later than in northern latitudes (from August to October) (Jensen and Aass, 1995;Jonsson and Jonsson, 2002;Rustadbakken et al, 2004) or in mid-latitudes (from October to November) (Ovidio, 1999;Benitez et al, 2015).…”

Meetprogramma Overijsselse Vecht : nulsituatie 2017 en effecten maatregelen

“…Voor sommige soorten speelt ook 5.) de watertemperatuur een belangrijke rol (Santos et al 2004(Santos et al , 2005Welsch 1991). Daarnaast dient de nevengeul de kenmerken van in de omgeving aanwezige, meestal iets kleiner gedimensioneerde, stromende wateren te hebben (Gustafsson et al 2013).…”

Investigative modelling of the flood bypass channel in Kuching, Sarawak, by assessing its impact on the inundations of Kuching-Batu Kawa-Bau Expressway

“…Recent guidelines have advocated a shift away from more technical bypass designs to more nature-like passes. Santos et al (2005) highlighted the use of these facilities for river restoration schemes. Sommer et al (2001) gave the example of the famous Yolo flood bypass (California, US) that was successful from a flood control standpoint, and also compatible with fisheries, wetlands, wildlife and agriculture.…”