Risk-sensitive foraging does not explain condition-dependent choices in settling reef fish larvae.

Area of Science:

• Marine Biology
• Behavioral Ecology
• Ichthyology

Background:

• Reef fish larvae face perilous transitions to adulthood, making critical habitat and group decisions.
• Bluehead wrasse (Thalassoma bifasciatum) larvae choose between solitary or grouped settlement, impacting survival and growth.
• Smaller fish tend to settle solitarily, a behavior potentially linked to foraging strategies.

Purpose of the Study:

• To test the hypothesis that smaller bluehead wrasse settle solitarily due to risk-sensitive foraging.
• To investigate if solitary fish experience higher foraging variance, offering potential high payoffs.
• To examine alternative explanations for solitary settlement in smaller reef fish.

Main Methods:

• Comparing stomach contents (prey items) and otolith-measured growth rates of solitary vs. grouped fish.
• Analyzing mean, standard deviation, and maximum prey intake and growth.
• Conducting the study during two settlement pulses in St. Croix, US Virgin Islands.

Main Results:

• No evidence was found to support the risk-sensitive foraging hypothesis for solitary settlement.
• No support for the claim that grouped fish exhibit lower average growth rates.
• The study did not find differences in prey items or growth rates between solitary and grouped fish.

Conclusions:

• The risk-sensitive foraging hypothesis does not explain why smaller bluehead wrasse settle solitarily.
• Alternative factors, such as the costs of group searching and joining, may drive settlement decisions.
• Larval and juvenile fish provide valuable insights into behavioral decision-making, with otoliths recording growth history.