Relative impacts of native and non‐native crayfish on shelter use by an indigenous benthic fish

Abstract

ABSTRACT1. The North American signal crayfish Pacifastacus leniusculus has been widely introduced throughout Europe where it is expanding its range and in many areas replacing the native white-clawed crayfish Austropotamobius pallipes. There is concern with regards to the impact of this species replacement on benthic fish. Interspecific behavioural interactions and competition for shelter between the benthic fish, bullhead Cottus gobio and A. pallipes and P. leniusculus were measured to assess the comparative impact of native and non-native crayfish.2. Both white-clawed crayfish and signal crayfish were dominant over bullhead. Bullheads moved away from approaches of crayfish, left shelters on entry of crayfish and rarely entered an occupied shelter. Signal crayfish made significantly more aggressive approaches towards bullheads than white-clawed crayfish.3. Alone, bullheads spent most of their time by day under shelter (median 96%), reflecting a highly entrained behavioural response, which was relaxed by night (median 60%). Both crayfish species reduced shelter use by bullheads although the extent of shelter sharing by bullheads was higher in trials with white-clawed crayfish than with signal crayfish.4. Sampling in the River Wharfe, northern England, where signal and white-clawed crayfish and bullhead currently exist, demonstrated a negative relationship between the densities of signal crayfish and bullhead, with high bullhead abundance where crayfish were absent or where white-clawed crayfish were present at low density.5. Assuming that shelter is sometimes limited under natural conditions, crayfish are likely to displace bullheads from shelters, which may increase predation risk for bullheads. Although the effects of signal crayfish on bullhead shelter use were more intense, the pattern was highly evident for the native white-clawed crayfish. The higher fecundity and densities attained by signal crayfish may be more significant than differences in the behaviour of the two crayfish species in determining the impact of crayfish on bullheads.

Comparing the ecological impacts of native and invasive crayfish: could native species’ translocation do more harm than good?

“…These results show that introduced across Europe, where impacts upon aquatic flora and fauna have been extensively documented (e.g. Unestam and Weiss 1970;Nyström et al 2001;Stenroth and Nyström 2003;Bubb et al 2006;Olden et al 2006;Bubb et al 2009;Axelsson et al 1997).…”

“…Charlebois and Lamberti 1996;Axelsson et al 1997;Parkyn et al 1997;Nyström et al 2001;Dorn and Mittelbach 2004;Usio and Townsend 2004;McCarthy et al 2006;Jackson et al 2014;Moorhouse et al 2014), demonstrated by their consistently strong negative effects on plant biomass, other macroinvertebrates, fish and amphibian eggs and larvae. Additionally, crayfish are likely to directly compete with other organisms for resources (Bubb et al 2009). Indeed the current study provides some evidence of resource competition in finding that the refuge use of fish was significantly lower in the presence of invasive, but not native, crayfish.…”

A review of ecological interactions between crayfish and fish, indigenous and introduced

“…Further, since signals chiefly hide under stones, they displace not only native crayfish but small fish sharing this habitat, such as salmon parr Salmo salar, bullhead Cottus gobio and stone loach Barbatula barbatula. By depriving the displaced fish of shelter they increase their susceptibility to predation, with potentially deleterious effects (Rahel and Stein, 1988;Guan and Wiles, 1997;Griffiths et al, 2004;Bubb et al, 2009). Competition for winter shelter has been experimentally demonstrated among exotic signal crayfish and native juvenile Atlantic salmon (Griffiths et al, 2004).…”

The impact of signal crayfish (Pacifastacus leniusculus) on the recruitment of salmonid fish in a headwater stream in Yorkshire, England

“…Where more than one fish species is present the interactions may vary, for example, small fish species can be displaced from shelter by crayfish, increasing their vulnerability to predation by piscivorous species (Rahel and Stein, 1988;Light, 2005); or the fish may show reduced growth in the presence of crayfish (Carpenter, 2005). Benthic fish appear to be particularly vulnerable to the effects of predation or competition by crayfish, with reductions in sculpin species in the USA (Light, 2005), and in bullhead Cottus gobio in England Wiles, 1997, 1998;Bubb et al, 2009). Whilst Bubb et al (2009) found some disturbance of bullhead by the indigenous white-clawed crayfish Austropotamobius pallipes, non-indigenous signal crayfish were much more aggressive towards the fish in laboratory trials, causing damage to fins and in some cases, mortality.…”

“…Benthic fish appear to be particularly vulnerable to the effects of predation or competition by crayfish, with reductions in sculpin species in the USA (Light, 2005), and in bullhead Cottus gobio in England Wiles, 1997, 1998;Bubb et al, 2009). Whilst Bubb et al (2009) found some disturbance of bullhead by the indigenous white-clawed crayfish Austropotamobius pallipes, non-indigenous signal crayfish were much more aggressive towards the fish in laboratory trials, causing damage to fins and in some cases, mortality. The same authors found reductions in abundance of bullhead in rivers too when signal crayfish were present.…”