Abstract
Predation threat is high at early life-history transitions stages, such as when settling to the benthic environment at the end of the pelagic larval stage. Therefore, understanding how young fish use chemical alarm cues (CAC’s) to assess predation risk is crucial. To date, there has been little attention towards the response of triplefin fish to CAC’s. For this reason, this thesis aimed to investigate how the common triplefin (Forsterygion lapillum) responds to CAC’s (chapter two) and whether they use these cues for learned predator recognition and display enhanced escape performance (chapter three).
In chapter two, the changes in routine swimming behavior of F. lapillum recruits, before and after exposure to a conspecific CAC, heterospecific CAC, or a saltwater control, were examined. Results showed that F. lapillum recruits decreased swimming speed and distance travelled in response to a heterospecific CAC. This response was likely a result of neophobia or learned recognition prior to capture. Furthermore, recruits showed a small increase in behavior in response to conspecific CAC’s. They may be displaying threat-sensitive behaviour by increasing vigilance towards secondary cues until faced with a higher risk threat, or the need for higher concentrations of CAC to trigger a stronger reaction. There was an unexpected increase in swimming speed and distance travelled in response to the saltwater control. Some fish increase movement in response to environmental changes, as water movement can indicate foraging opportunities. The saltwater cue was used to control for fluid disturbance, and it is possible that the response to the fluid disturbance was dampened by the presence of alarm cues. Chapter three involved subjecting F. lapillum recruits to conditioning and testing phases using conspecific and heterospecific CAC’s to determine whether, after a single exposure to a paired presentation of a CAC and a novel predator scent, the recruits could associate the novel scent with danger. Results suggest that F. lapillum likely acquire predator recognition through conditioning with conspecific alarm cues, but their response to predator cues may depend on the available information, e.g., type and number of cues presented. The decreased response to predator odour alone indicates that additional cues may be needed to maximise escape behaviors. Latent inhibition and F. lapillum’s tendency to freeze rather than flee may have also influenced these results. Despite variations in escape responses, including kinematics and performance, reactions such as freezing still indicate risk recognition. The findings of this study highlight the complex, context-dependent responses of F. lapillum to predator-prey cues and lays the foundation for future research into triplefin predator-prey interactions.