Session A1: Effects of Sluices on Migrating Elvers and Other Fish in a Dutch Salt Water / Fresh Water Gradient

• Main Authors: Boogaard, Bas van den, Bergsma, Joost, Schaub, Bart, Vuister, Lucienne
• Format: Text
• Language: unknown
• Published: ScholarWorks@UMass Amherst 2015
• Subjects: Aquaculture and Fisheries; Hydraulic Engineering; Anguilla anguilla
• Online Access: https://scholarworks.umass.edu/fishpassage_conference/2015/June22/13; https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1972&context=fishpassage_conference

Abstract Many of the formerly gradual transitions between marine and freshwater habitats have been severely altered by man-made constructions. In the Netherlands, water managers are implementing numerous measures to decrease the negative effects of these barriers on fish migration (e.g. constructing fish passages). Adjusting sluice management to restore a salt water / fresh water gradient, however, is a novel way of accommodating fish migration. To effectively apply this measure, more knowledge is required on how fish migration is influenced by sluices. At Spaarndam (the Netherlands), a complex of pumping stations and sluices separates salt water and fresh water. Within this complex, fish can either migrate into discharge channels towards pumping stations, or migrate into sluices and continue upstream. In spring 2014, we evaluated fish migration at the Spaarndam complex to determine where fish enter (i.e. into the sluices or discharge channels), and whether fish were able to pass the complex. A total of seventeen species were observed. The vast majority of individuals were juvenile Anguilla anguilla (elver). A marked difference within the complex was observed: when fresh water was discharged, the vast majority of elvers migrated towards the impassable pumping stations. Migrating elvers were almost absent in sluices. This was most likely due to the lack of an attraction flow at the sluices. In contrast, other species (e.g. pike-perch, bream and perch) used the sluices for migration utilizing openings in the sluice doors. We conclude that the attraction flow at sluices in Spaarndam is too low to attract elvers, therefore effectively creating a barrier to migration. Although effective for other fish species (e.g. pike-perch, bream and perch), adjusting sluice management is not effective for elvers. The creation of a continuous small attraction flow, in combination with the construction of a fish passage will be more effective for elvers.