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

Area of Science:

• Marine Biology
• Fish Physiology
• Bioenergetics

Background:

• Understanding the metabolic rates of highly migratory fish like tuna is crucial for assessing their ecological roles and energy budgets.
• Previous studies on tuna metabolism have often relied on less direct methods or focused on a limited range of conditions.

Purpose of the Study:

• To quantify the metabolic rates (V(dot)O2) of three tropical tuna species: yellowfin tuna (Thunnus albacares), kawakawa (Euthynnus affinis), and skipjack (Katsuwonus pelamis).
• To investigate the effects of swimming velocity (U) and temperature on tuna metabolic rates.
• To compare the metabolic characteristics and swimming efficiency of tunas with other fish, such as salmonids.

Main Methods:

• Utilized a large water-tunnel respirometer for precise measurements of oxygen consumption.
• Conducted experiments over extended periods (up to 31 hours) across a range of swimming velocities (17-150 cm s-1) and temperatures (18-30°C).
• Employed extrapolation to U=0 to estimate standard metabolic rate (SV(dot)O2) and partitioned metabolic costs into maintenance and locomotion for yellowfin and skipjack tuna.

Main Results:

• The swimming V(dot)O2 for yellowfin tuna was found to be temperature-dependent, with a Q10 of 1.67.
• The mass-specific scaling exponent for V(dot)O2 in yellowfin tuna was determined to be -0.40.
• Tuna exhibited a standard metabolic rate comparable to previous estimates but approximately three times higher than salmonids.
• Tunas demonstrated greater swimming efficiency than salmonids, indicated by a less steep U/V(dot)O2 function.

Conclusions:

• Tropical tunas possess distinct metabolic characteristics, including temperature dependence and higher standard metabolic rates compared to salmonids.
• Tunas display superior swimming efficiency, a key adaptation for their active, migratory lifestyle.
• The findings provide valuable insights into the bioenergetics and physiological adaptations of these important pelagic predators.