Abstract

Hatchery-reared fishes, especially salmonids, are routinely stocked into natural waterways as a part of population enhancement and recovery programs, and conservation efforts. These initiatives, however, are often met with limited success due to poor post-stocking survival of hatchery fish. It has been suggested that a failure to recognize predators by hatchery-reared fish leads to disproportionately low post-stocking survival rates. A commonly advocated approach to enhancing post-stocking survival is to condition hatchery fish to recognize and avoid relevant threats through ‘life skills training’. However, such approaches have yielded decidedly mixed results. Here, I tested the prediction that phenotypically plastic neophobic predator avoidance (the avoidance of novel cues) can be induced in hatchery reared Atlantic salmon. This response may lead to the enhancement of post-stocking survival among hatchery reared juvenile Atlantic salmon; making it a new approach to life skills training. Initially, I tested the prediction that hatchery reared juvenile salmon subjected to alarm cue (a known, reliable cue indicating a predation event) for a prolonged period of time would elicit a neophobic response (defined as a significant decrease in time spent on the substrate and foraging attempts) to a novel cue during testing. During the treatment phases of three or six days, juvenile hatchery Atlantic salmon were given either alarm cue (high risk) or a water control (low risk). Following the treatment phases, fish from both treatment conditions were given a stimulus of either novel odour or a water control. The test fish’s time on substrate and foraging attempts were recorded pre- and post- stimulus, allowing me to investigate changes in behaviour caused by the presence of the novel stimuli. My results suggested that juvenile Atlantic salmon pre-exposed to alarm cue for three days did not demonstrate neophobic predator avoidance behaviour, however those pre-exposed for six days did exhibit an increase in time on substrate and a reduction in foraging attempts. Secondly, I tested the prediction that a neophobic response induced in hatchery reared fish over a six-day treatment phase would be retained throughout a transportation and stocking event. Conditioned salmon were transported to Catamaran Brook (Catamaran Research Centre), and tested for their response to a novel cue vs. water control. My results suggest that juvenile Atlantic salmon pre-exposed to alarm cue for six days and transported and released into a semi-natural environment did not demonstrate neophobic behaviour towards a novel cue. This suggests that the neophobic response was not retained throughout a transportation and stocking event. Finally, I tested the prediction that neophobic predator avoidance could be induced in hatchery reared and wild juvenile Atlantic salmon in a semi-natural environment. Wild and hatchery fish were subjected to alarm cue or water (control) for six days in a semi-natural environment after which their behaviour towards a novel cue was tested (in the same fashion as in experiment one) in the semi-natural environment. My results suggested that hatchery-reared fish given alarm cue for six days in a semi-natural environment demonstrated a neophobic predator avoidance response to a novel cue during behavioural testing in the semi-natural environment; however wild fish in the same conditions did not.