Standard oxygen consumption of seasonally acclimatized cownose rays, Rhinoptera bonasus (Mitchill 1815), in the northern Gulf of Mexico.

Standard oxygen consumption rate (MO(2)) was determined for 19 cownose rays (Rhinoptera bonasus) using flow-through respirometry. Rays ranged in size from 0.4 to 8.25 kg (350-790 mm DW). Respirometry experiments were conducted on seasonally acclimatized rays at temperatures from 19.0 to 28.8 degrees C. Estimates of mass-dependent MO(2) ranged from 55.88 mg O(2) kg(-1) h(-1) for an 8.25 kg ray to 332.75 mg O(2) kg(-1) h(-1) for a 2.2 kg animal at 22-25 degrees C. Multiple regression analysis examining the effect of temperature, salinity, and mass on standard mass-independent MO(2) found temperature (P < 0.01), and mass (P < 0.0001) to have a significant effect on oxygen consumption, whereas salinity did not (P > 0.05). Q (10) was calculated as 2.33 (19-28 degrees C), falling between the estimates determined for two other batoid species, the bull ray (Myliobatos aquila; Q (10) = 1.87) and the bat ray (Myliobatis californica; Q (10) = 3.00). The difference in the Q (10) estimates may be attributed to the use of seasonally acclimatized as opposed to laboratory-acclimated animals.