Sensitivity of northern redbelly dace, Phoxinus eos, to chemical alarm cues

Abstract

The northern redbelly dace, Phoxinus eos (Cope, 1862), is subject to predation by brook trout, Salvelinus fontinalis (Mitchill, 1814), in Canadian Shield lakes, particularly when individuals migrate to the pelagic zone at sunset to feed on zooplankton and fish shoals break up into single individuals. The objectives of the present study were to (i) determine whether northern redbelly dace react to skin extracts from conspecifics and thus potentially use chemical alarms to detect predators in nature, (ii) characterize the fright reaction in northern redbelly dace under different concentrations of alarm substance, and (iii) estimate the active space of the alarm substance in this species. Northern redbelly dace responded to skin extracts of conspecifics with a series of antipredator behaviours. The dace moved closer to the substrate and away from the area where the alarm substance was injected, increased both the cohesion and polarization of their schools, and performed more dashing and freezing behaviours. The observed responses were closely correlated with the concentration of the skin extract solution, suggesting that individuals could use this sensitivity to different concentrations of alarm substance to estimate the risk of predation in nature. The dilution experiment allowed us to estimate that 1 cm2 of northern redbelly dace skin contains enough alarm substance to generate a response of individuals in 110 558 L of water, which corresponds to a cube with sides of approximately 4.8 m. Indirect evidence suggests that the northern redbelly dace could use chemical alarm cues to assess the risk of predation by brook trout in nature.

Can the ratio of aromatic skeletons explain cross-species responses within evolutionarily conserved Ostariophysan alarm cues?: testing the purine-ratio hypothesis

“…The relative concentration of alarm cue detected should be directly related to proximity to a predation event, and as such, prey fishes should be able to assess local predation risk based on the concentration of alarm cue detected (Lawrence & Smith 1989, Dupuch et al 2004. Prey capable of adjusting the intensity of their antipredator response should be at a selective advantage, as they would be able to optimize the threat-sensitive trade-off between predator avoidance and foraging benefits (Helfman 1989).…”

Learning about Danger: Chemical Alarm Cues and Threat‐Sensitive Assessment of Predation Risk by Fishes

“…When released, following mechanical damage to the skin, these cues can elicit dramatic short-term increases in species typical antipredator behaviours (Chivers & Smith 1998;Wisenden & Chivers 2006). Recent studies suggest that there is often a strong relationship between the relative concentration of alarm cues prey detect and the intensity of the antipredator responses displayed by the prey (Jachner & Rydz 2002;Dupuch et al 2004;Brown et al 2006aBrown et al , 2009). Moreover, prey may attend to alarm cues at very low concentrations by increasing vigilance towards secondary risk assessment cues (Brown et al 2004) or may show subtle adjustments in their foraging tactics (Foam et al 2005a).…”

The paradox of risk assessment: comparing responses of fathead minnows to capture-released and diet-released alarm cues from two different predators

“…They often elicit a dramatic increase in antipredator behaviour when detected by conspecifics and some heterospecifics (reviewed by Chivers & Smith 1998). Experimental manipulations of alarm cue concentrations have shown that increased alarm cue concentrations elicit increases in the intensity of antipredator behaviour displayed by some fish (Dupuch et al 2004, Zhao & Chivers 2006, including fathead minnows (Ferrari et al 2005. While these chemicals likely did not primarily evolve as true alarm signals (Wisenden & Chivers 2005, Chivers et al unpublished data), prey responding to these chemicals have a selective advantage.…”