How sailfish use their bills to capture schooling prey

Area of Science:

• Marine Biology
• Ichthyology
• Biomechanics

Background:

• Istiophorid billfishes possess a characteristic elongated rostrum or 'bill'.
• Previous research proposed functions for the bill, including foraging and hydrodynamic advantages.
• The precise feeding mechanisms employed by billfishes using their rostrum remained uninvestigated.

Purpose of the Study:

• To provide the first direct evidence of how Atlantic sailfish (Istiophorus albicans) utilize their bills for feeding.
• To analyze the specific actions of the sailfish rostrum when attacking schooling prey in the open ocean.

Main Methods:

• High-speed video analysis was employed to capture and scrutinize sailfish feeding behaviors.
• Observation focused on the interaction between sailfish and schools of sardines.

Main Results:

• Sailfish successfully infiltrated sardine schools without triggering prey evasion.
• The rostrum was used for precise tapping on individual sardines or rapid slashing motions through schools.
• These slashing motions exhibited extremely high accelerations, among the fastest recorded in aquatic vertebrates.

Conclusions:

• The sailfish bill is a highly effective feeding adaptation for capturing schooling prey.
• A combination of stealthy approach and rapid, forceful bill movements characterizes sailfish predation.
• The study elucidates the biomechanical mechanisms behind the sailfish's unique hunting strategy.