STUDIES OF TROPICAL TUNA SWIMMING PERFORMANCE IN A LARGE WATER TUNNEL - KINEMATICS

Area of Science:

• Ichthyology
• Biomechanics
• Hydrodynamics

Background:

• Tunas are highly migratory fish known for their speed and endurance.
• Understanding fish swimming kinematics is crucial for biomechanics and hydrodynamics.
• Previous studies have characterized swimming in various teleosts, but tuna-specific adaptations require further investigation.

Purpose of the Study:

• To quantify the swimming kinematics of yellowfin tuna (Thunnus albacares).
• To compare tuna swimming parameters with those of other teleost fish.
• To elucidate the relationship between kinematic variables, morphology, and swimming performance in tunas.

Main Methods:

• Swimming kinematics were measured in a large water tunnel at controlled velocities.
• Key variables quantified included tail-beat frequency, stride length, caudal amplitude, yaw, propulsive wavelength, wave speed (C), and pectoral fin sweepback angle.
• Measurements were correlated with tuna morphology, including fork length (L).

Main Results:

• Most kinematic variables were comparable to other teleosts, except for propulsive wavelength and wave speed (C).
• Yellowfin tuna displayed a propulsive wavelength 30-60% longer than cruise-adapted teleosts like salmonids (1.23-1.29 L).
• This longer wavelength, coupled with a fusiform body shape and rigid vertebral column, minimizes drag and maximizes thrust.

Conclusions:

• The thunniform swimming mode of yellowfin tuna, characterized by a long propulsive wavelength, is a key adaptation for efficient high-speed swimming.
• Morphological adaptations optimize anterior resistance reduction and caudal thrust generation.
• The extended propulsive wavelength contributes to increased stride length and, with elevated muscle temperatures, enhances maximum swimming velocity.