Biol Invasions (2018) 20:757–776 https://doi.org/10.1007/s10530-017-1573-3 ORIGINAL PAPER Low-head dams facilitate Round Goby Neogobius melanostomus invasion Dustin Raab . Nicholas E. Mandrak . Anthony Ricciardi Received: 9 July 2017 / Accepted: 23 September 2017 / Published online: 3 October 2017 Ó Springer International Publishing AG 2017 Abstract Round Goby Neogobius melanostomus inclusion of both reservoir-associated abiotic variables invasion of the Grand River (Ontario, Canada) and Round Goby abundance as model terms. To presents an opportunity to assess the role of abiotic determine establishment potential of the uninvaded gradients in mediating the establishment and impact of reach immediately upstream, four environmental nonnative benthic fishes in rivers. In this system, habitat characteristics were used in discriminant sequential low-head dams delineate uninvaded and function analysis (DFA) to predict three potential invaded river reaches and create upstream gradients of outcomes of introduction: non-invaded and either increasing water velocity. We hypothesized that flow lower or higher Round Goby abundance (low and high refugia created by impounded reservoirs above low- invasion status, respectively) than the median number head dams enhance local Round Goby abundance. of Round Goby at invaded sites. Our DFA function Round Goby influence on the native fish community correctly classified non-invaded and high-abundance was determined by variance partitioning, and we used invasion status sites [ 85% of the time, with lower generalized additive models to identify small-bodied (73%) success in classifying low-abundance invasion benthic fish species most likely to be impacted by status sites, and the spatial pattern of our results Round Goby invasion. Round Goby abundance suggest that likelihood of establishment is greatest in declined as the degree of reservoir effect decreased impounded habitat. upstream. The distributions of four species (including the endangered Eastern Sand Darter Ammocrypta Keywords Establishment Á Impact Á Laurentian pellucida) in invaded reaches were best explained by Great Lakes Á Tributary impoundment D. Raab (&) Á A. Ricciardi Redpath Museum, McGill University, 859 Sherbrooke St. Introduction West, Montreal, QC H3A 0C4, Canada e-mail: [email protected] More than 180 aquatic nonindigenous species are D. Raab established in the Laurentian Great Lakes basin Biology Department, McGill University, 1205 Docteur (GLB), and some of these species have caused Penfield, Montreal, QC H3A 1B1, Canada substantial ecological and economic impacts (Mills et al. 1993; Ricciardi 2006). The GLB is a model N. E. Mandrak University of Toronto Scarborough, 1265 Military Trail, system for studying how introduced species invade Toronto, ON M1C 1A4, Canada new environments, yet most attention has focused on 123 758 D. Raab et al. the establishment of invaders in the lakes themselves, can facilitate invasions within a watershed by acting as rather than their tributaries. Physical attributes of ‘stepping-stones’ for spread and by supporting tributaries (e.g., water velocity, temperature) may increased propagule pressure, altering hydrologic initially inhibit establishment by aquatic invasive conditions, and altering native assemblages (Havel species, such as dreissenid (zebra and quagga) mussels et al. 2005; Johnson et al. 2008). For example, low- and Eurasian Ruffe Gymnocephalus cernua, which head dams are believed to enhance downstream have been slow to colonize flowing waters (Bauer recruitment of dreissenid mussels in an inland river- et al. 2007). Round Goby Neogobius melanostomus,a reservoir system, by supporting high mussel abun- small non-indigenous benthic fish of Eurasian origin, dance in the lentic sections above dams (Smith et al. has recently expanded its range into tributaries after 2015). On some GLB tributaries, low-head dams may colonizing all five Great Lakes (Bronnenhuber et al. impede Round Goby range expansion (Poos et al. 2011; Poos et al. 2010) and was the fastest spreading 2010). Yet, on the Grand River in southern Ontario, vertebrate in the GLB in the years immediately Round Goby has been detected above dams that are following its introduction (Dopazo et al. 2008). Round naturally impassable to them, suggesting human- Goby has become the most abundant benthic fish in facilitated transport in sufficient numbers to overcome some nearshore Great Lakes habitats (Kornis et al. demographic barriers to establishment (Bronnenhuber 2012) and has been linked to local declines or et al. 2011). The slower water velocity of the extirpations of native fishes, including Logperch impounded reservoir immediately upstream of the Percina caprodes and Mottled Sculpin Cottus bairdii dam may provide a flow refuge for Round Goby, (Balshine et al. 2005; Janssen and Jude 2001; Leino which cannot hold a fixed position in water velocities and Mensinger 2016). Documented impacts of Round above 0.35 m s-1 and cannot sustain swimming Goby on native fish communities in tributaries appear speeds over 1.25 m s-1 (Tierney et al. 2011). There- not to have been as severe as in the Great Lakes proper fore, high water velocities could form an effective (Kornis et al. 2013; Poos et al. 2010), but a broader barrier to the upstream movement of Round Goby in suite of species may be affected. Fish communities in hydrologically unmodified tributaries and in areas southwestern Ontario tributaries are the most speciose beyond the reservoir on modified tributaries. Reser- in Canada, with a number of nationally listed at-risk voir sections affect more than just water velocity, with fishes confined to small ranges within this region consequences for substrate size and embeddedness, (Staton and Mandrak 2005). For example, Northern channel width, and depth (Alexandre and Almeida Madtom Noturus stigmosus and Eastern Sand Darter 2010; Gillette et al. 2005; Santucci et al. 2005). We Ammocrypta pellucida are two at-risk native benthic describe this suite of highly collinear variables acting fishes found in tributaries colonized by Round Goby in concert as the ‘reservoir effect’. (Poos et al. 2010), and the conservation implications Compared to unmodified rivers, fish communities of these invasions is uncertain. in dammed rivers may be more vulnerable to the Tributaries in the GLB have frequently been effects of fish invasions, and there is considerable hydrologically altered for navigation, flow manage- evidence that the reservoir effect tends to favour ment, hydroelectricity, and preventing the spawning invaders (Alexandre and Almeida 2010; Falke and migration of invasive Sea Lamprey Petromyzon Gido 2006; Moyle and Marchetti 2006). The majority marinus (Harford and McLaughlin 2007; Noakes of research examining Round Goby invasion of GLB et al. 2000; Porto et al. 1999). The majority of these tributaries has not extended upstream of the first dams are low-head barriers (\ 4 m in height), which barrier (e.g., Abbett et al. 2013; Campbell and Tiegs have less pronounced fragmentation, hydrologic, and 2012; Kornis et al. 2013; Krakowiak and Pennuto water chemistry effects than large dams (Cumming 2008) and has typically focused on relatively slow- 2004; Nilsson et al. 2005). Nonetheless, low-head moving stream reaches near lake inlets (Pennuto et al. dams restrict fish movement (Noakes et al. 2000; Porto 2010). Round Goby behaviour in slow-moving and et al. 1999) and share similarities with large dams by reservoir habitat likely plays a role in the decline of affecting river processes and biota at local and native benthic fishes; aggression and competitive landscape scales (Dodd et al. 2003; Harford and superiority has been observed experimentally where McLaughlin 2007; Santucci et al. 2005). Reservoirs food and shelter are limiting (Balshine et al. 2005; 123 Low-head dams facilitate Round Goby invasion 759 Dubs and Corkum 1996; Janssen and Jude 2001; affect abundance of native benthic fishes where these Kornis et al. 2012). Presence of Round Goby at low species co-occur. Finally, we used invaded reaches to densities was experimentally shown to negatively predict establishment risk to an uninvaded reach if affect the growth of a native darter in a slow-moving Round Goby are introduced, a plausible scenario given GLB tributary (average water velocity \ 10 m s-1), strong angling activity in the region (Drake and which was attributed to interspecific competition Mandrak 2014). (Kornis et al. 2014); however, the trend was not evident at high invader abundance, potentially a result of complex inter- and intraspecific interactions that Methods were responsible for increased mortality. Where access to free-flowing riverine habitat is limited by Study area impoundment and the creation of a reservoir effect, Round Goby are the likely winners of competition; The Grand River (43°080N, 80°170W) is a species-rich when the reservoir effect is minimal, lotic-adapted tributary of Lake Erie and a species-at-risk hotspot species are likely to persist. (Poos et al. 2010). It is highly fragmented, with over We surveyed the Grand River as a model system to 130 dams throughout the * 6500 km2 watershed examine the role of abiotic gradients in mediating the (Reid et al. 2008). Three reaches of the middle and colonization and impact of Round Goby. We hypoth- lower Grand River, bounded at their downstream and esized that impoundments above low-head dams upstream limits by dams, were sampled between 2010 create a reservoir effect that promote establishment and 2014 (Fig. 1). Moving downstream in the water- of Round Goby, while negatively affecting the abun- shed, the three reaches measure 15 km (reach 1; R01), dance of native small-bodied benthic fishes. Further, 43 km (reach 2; R02), and 53 km (reach 3; R03), we predicted that Round Goby itself would negatively respectively. Stream gradient is highest in R01 Fig. 1 Location of the study area within the lower Grand River by numbered arrows: 1. Dunnville Dam, Dunnville, Ontario; 2. watershed, sampled from 2010 to 2014. Detail view: Study sites Caledonia Dam, Caledonia, Ontario; 3. Wilkes Dam, Paris, (circles) on three river reaches (R01–R03). Dams are indicated Ontario; 4. Paris Dam, Paris, Ontario 123 760 D.