Predator effects on reef fish settlement depend on predator origin and recruit density.

Area of Science:

• Marine Ecology
• Behavioral Ecology
• Conservation Biology

Background:

• Predator avoidance is crucial during life-history transitions, especially for coral-reef fishes.
• The influence of predator presence on fish settlement is mixed, with few studies exploring mediating factors like predator origin or conspecific density.
• Non-consumptive effects of predators can significantly impact prey populations.

Purpose of the Study:

• To investigate how predator presence, origin (native vs. nonnative), and conspecific density affect coral-reef fish settlement.
• To determine if mahogany snapper (Lutjanus mahogoni) and bicolor damselfish (Stegastes partitus) differentiate between native and invasive predators.
• To assess the role of competition in mediating predator avoidance responses.

Main Methods:

• A field experiment was conducted in the Caribbean using controlled predator treatments (native, invasive, predator-free).
• Recruitment of mahogany snapper and bicolor damselfish was monitored on experimental reefs.
• Conspecific recruit density was manipulated or measured to assess its interaction with predator effects.

Main Results:

• Mahogany snapper recruitment was reduced by 52% in the presence of a native predator (graysby grouper) but not by an invasive predator (red lionfish).
• Predator effects on snapper were density-dependent, with competition potentially masking predator avoidance at high conspecific densities.
• Bicolor damselfish recruitment was unaffected by predator presence or conspecific density.

Conclusions:

• Coral-reef fish recruits may not recognize novel, invasive predators, impacting their survival and population dynamics.
• Conspecific density and competition can modify predator avoidance behaviors, highlighting context-dependent responses.
• Understanding these interactions is vital for predicting fish community structure and effective conservation strategies.