A comparison of passage efficiency for native and exotic fish species over an artificial baffled ramp

Abstract

This study used an experimental approach to compare the passage success of native and exotic fish species from the temperate Southern Hemisphere over an artificial baffled fish ramp designed for overcoming low‐head (≤1.0 m) fish migration barriers. Passage efficiency was, on average, lower for the exotic species [koi carp (Cyprinus carpio), rudd (Scardinius erythrophthalmus) and rainbow trout (Oncorhynchus mykiss)] compared to the native species [inanga (Galaxias maculatus), redfin bully (Gobiomorphus huttoni) and common bully (Gobiomorphus cotidianus)]. Nonetheless, there was considerable variation between individual species, with rainbow trout outperforming common bully and juvenile inanga, but koi carp and rudd failing to pass any of the ramps. The differences in predicted probability of passage success between the native and exotic fish species in this study were sufficient in some cases to indicate the potential for the baffled fish ramps to operate as a selective migration barrier. Nonetheless, further testing is required to validate these results across a broader range of conditions before deployment.

Rubber ramp and spat rope did not facilitate upstream passage of a galaxiid through a perched culvert

“…In comparison, Franklin and Bartels (2012) recorded a mean of 27% passage efficiency for G. maculatus over a 9-h trial period at a 15-m-long rock ramp, whereas Doehring et al (2011) measured passage efficiencies for G. maculatus of 21-66% over 3-m artificial ramps (artificial grass substrate) at a range of gradients (4-h trial period). Likewise, Baker (2014), Baker and Boubée (2006) and Franklin et al (2021) all recorded 3-h passage efficiencies for G. maculatus ranging from 20 to >90% over experimental fish ramps up to 3 m long with gradients of 15-30°.…”

“…salmonids) are competent jumpers and can sometimes make their way past (albeit at lower success rates; Frankiewicz et al 2021), for some small-bodied fishes (<60 mm) it has been demonstrated that vertical drops as little as 0.1 m can effectively prevent upstream passage (Baker 2003). Efforts to overcome these drops, where structure replacement is not an option, have focused on reducing the head drop by raising the downstream water level using rock ramp fishways (Franklin and Bartels 2012;Muraoka et al 2017) or creating artificial ramps that connect to the culvert outlet (Baker 2014;Jellyman et al 2017;Watz et al 2019;Franklin et al 2021).…”

Movement behaviour and fishway performance for endemic and exotic species in a large anthropized river

“…The very good passage success of exotic species in the fishway of the Meuse constitutes a collateral adverse effect of the reopening of the migration route that will increase expansion areas, with potential negative impacts for indigenous species (Leuven et al, 2009;McLaughlin et al, 2013). In an experimental approach in a baffle fish-ramp, Franklin et al (2021) observed that passage efficiency was, on average, lower for the exotic species, suggesting that the use of such a selective structure may, in some instances, slow down the progression of invasive species.…”

“…Nonetheless, enhanced connectivity with multispecies fishway can be a disadvantage in some situations, allowing the invasion, dispersal and increased recruitment of unwanted and/or exotic species; facilitating the spread of diseases; and providing access to degraded habitats that act as ecological sinks (Franklin et al, 2021). There is an increased interest in focussing some research on both endemic and exotic/non indigenous species.…”