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First published online November 19, 2007
Journal of Experimental Biology 210, 4254-4261 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.005835

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Temperature effects on metabolic rate of juvenile Pacific bluefin tuna Thunnus orientalis

Jason M. Blank^1,*, Jeffery M. Morrissette¹, Charles J. Farwell², Matthew Price², Robert J. Schallert² and Barbara A. Block¹

¹ Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA
² Monterey Bay Aquarium, Monterey, CA 93940, USA

View larger version (13K): [in this window] [in a new window]   Fig. 1. Time course of respirometry in a bluefin tuna. Oxygen consumption (O2, filled circles) was calculated from the slope of ambient [O2] measured during 10 min periods with the swim tunnel sealed. An overnight acclimation period preceded tests of swim speed (blue line, in BL s–1) and temperature (black line) effects on O2. The arrow during the acclimation period indicates elevated O2 measurements following a power surge, which startled the fish. Speed changes are described elsewhere (Blank et al., 2007) and were not a part of the present study.

View larger version (7K): [in this window] [in a new window]   Fig. 2. Temperature effects on swimming bluefin tuna. (A) O2 (mean ± s.d.) of six bluefin tuna swimming at a constant speed of 1.0 BL s–1 in the swim tunnel was significantly affected by temperature (ANOVA, P<0.001). O2 of each fish at each temperature was calculated as the mean of six or more O2 measurements taken after an equilibration period of at least 1 h at the stated temperature (±0.1°C). * Significant difference from O2 at 15°C (P<0.05, Tukey's HSD). (B) Mean tailbeat frequency (± s.d.) of six bluefin tuna swimming at 1.0 BL s–1 in the swim tunnel was significantly affected by temperature (ANOVA, P<0.01). Significant difference from TBF at 8°C.

View larger version (10K): [in this window] [in a new window]   Fig. 3. Effects of ambient temperature and speed on bluefin tuna O2 and tailbeat frequency (TBF). (A) O2 measurements at swim speeds of 0.75–1.75 BL s–1 were repeated at three steady-state temperatures on three consecutive days. A significant interaction of temperature and speed effects on O2 was observed (ANOVA, P<0.05). O2 increased with swimming speed at 20 and 25°C (P<0.001), but was unaffected by speed at 8°C (P=0.89). Data shown are means ± s.d. of O2 measurements from three individual bluefin tuna (mass=8.1±0.6 kg). (B) Tailbeats were counted as bluefin swam at speeds of 0.75–1.75 BL s–1 at temperatures of 8, 20 and 25°C. Both temperature and speed had significant effects on TBF (P<0.001). Data shown are means ± s.d. of TBF counts from three individual bluefin tuna (mass=8.1±0.6 kg).

View larger version (6K): [in this window] [in a new window]   Fig. 4. Effects of ambient temperature and swimming speed on gross cost of transport (GCOT) of bluefin tuna. GCOT was calculated from measured O2 and swimming speed using an oxycalorific coefficient of 14.1 J mg O –12. A significant interaction of speed and temperature was observed (P=0.023). Values are means ± s.d. of O2 measurements from three individual bluefin tuna (mass=8.1±0.6 kg).

View larger version (9K): [in this window] [in a new window]   Fig. 5. Visceral temperatures of bluefin tuna in the respirometer. (A) Visceral (black) and ambient water temperature (gray) data were logged at 4 s or 8 s intervals by archival tags implanted in the peritoneal cavity of the fish prior to the experiment and recovered post-mortem. Swim speed was held constant at 1.0 BL s–1 throughout the experiment. Thermal inertia is evident as a time lag between changes in ambient and visceral temperatures. (B) Visceral thermal excess (Tx) of bluefin tuna swimming in the respirometer. Steady-state Tx was calculated as the difference between visceral and ambient temperatures of fish swimming at constant speeds of 1.0 BL s–1 following equilibration to the designated ambient temperature for at least 2.5 h. Temperature data were logged at 4 s or 8 s resolution by archival tags implanted in the peritoneal cavity prior to experiments. Values shown are mean ± s.d. for N=3 bluefin tuna (N=2 at 25°C).

View larger version (9K): [in this window] [in a new window]   Fig. 6. Ambient water (A) and visceral temperatures (B) recorded from bluefin tuna in the wild (CFL=75.2±2.8 cm; mass=8.6±0.9 kg at time of tagging; interval between tagging and recapture=241±131 days). Histograms indicate % occupancy of 1°C temperature bins. Values are mean ± s.e.m. (N=10).

View larger version (46K): [in this window] [in a new window]   Fig. 7. Archival tag record demonstrating fasting and feeding in a wild Pacific bluefin tuna (16 kg). Depth (black), peritoneal cavity temperature (Tb, red), and ambient temperature (Ta, blue) are shown. Day and night are represented as light and dark bars, respectively. In (A) regular feeding events are indicated by a rise in peritoneal cavity temperature resulting from digestion. In (B) a stable Tb elevated only slightly relative to Ta indicates the absence of feeding events for four days, followed by the resumption of feeding.