Barriers that lead to fragmented systems can prevent the spread of nonnative species, exotic diseases, and hybridization ( Rahel, 2013). Barriers to passage can create potential implications for long-term population dynamics or in extreme cases, lead to the extirpation of a species or threaten biodiversity ( Larinier, 2000 Pess et al., 2008 Liermann et al., 2012).Īlthough habitat fragmentation may be detrimental to native migratory fish species, impassable barriers can provide an effective, economical tool for controlling harmful and invasive species ( Rahel & McLaughlin, 2018 Altenritter et al., 2019). Additionally, downstream migration through turbines or spillways may result in significant mortality of fish ( Larinier, 2002 Čada et al., 2006). Hydraulic challenges ( e.g., velocity, turbulence) and structural impermeability can heavily impact upstream fish passage through dams and reduce connectivity between important feeding and spawning areas ( Northcote, 1998 Larinier, 2000 Zielinski, Voller & Sorensen, 2018). Dams are known to impede fish passage in lotic systems ( Porto, McLaughlin & Noakes, 1999 Larinier, 2001 Knights et al., 2002 Zigler et al., 2004). The movement and dispersal of migratory fish species are important life-history characteristics that can be restricted by natural and artificial structures ( Kruk & Penczak, 2003 Zielinski, Voller & Sorensen, 2018). Understanding fish behavior at UMR dams is a critical information need for river managers as they evaluate potential tools or technologies to control upstream expansion of bigheaded carp in the UMR. Continued study to understand the effects of deterrents on native fish could be beneficial for implementing an integrated bigheaded carp control strategy. In years with infrequent open-river condition, a deterrent placed in the downstream lock approach may assist in meeting the management goal of reducing upstream passage of bigheaded carps but could also potentially affect paddlefish residency and passage. When hydraulic head was approximately 1-m or greater, we observed these taxa opt for upstream passage through the lock chamber more often than the dam gates. The majority of the upstream passages through the spillway gates for both species occurred during open river conditions. We identified four bigheaded carp and 19 paddlefish that made upstream passages through the spillway gates at LD 15 during this study. We documented upstream passages completed by two individual paddlefish through the lock chamber at LD 15, and a single bighead carp completed upstream passage through the lock chamber during two separate years of this study. Paddlefish residency events in the downstream lock approach of LD 15 occurred more frequently and for longer durations than residency events of bigheaded carp. We observed successful paddlefish passage at all dams, with the highest number of passages occurring at LDs 17 and 16. We used acoustic telemetry to evaluate paddlefish passage at UMR dams and to evaluate seasonal and diel movement of paddlefish and bigheaded carp relative to environmental conditions and lock operations at LD 15. Lock and Dam (LD) 15 is infrequently at open-river condition (spillway gates completely open hydraulic head across the dam <0.4 m) and has been identified as a potential location for fish deterrent implementation. Various technologies have been proposed as potential fish deterrents at locks and dams to reduce bigheaded carp (i.e., silver carp and bighead carp ( Hypophthalmichthys spp.)) range expansion in the Upper Mississippi River (UMR). Although habitat fragmentation may be detrimental to native fish species, it might act as an effective and economical barrier for controlling the spread of invasive species in riverine systems. Movement and dispersal of migratory fish species is an important life-history characteristics that can be impeded by navigation dams.
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