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

Standard oxygen consumption rate (MO₂) 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 °C. Estimates of mass-dependent MO₂ ranged from 55.88 mg O₂ kg⁻¹ h⁻¹ for an 8.25 kg ray to 332.75 mg O₂ kg⁻¹ h⁻¹ for a 2.2 kg animal at 22–25°C. Multiple regression analysis examining the effect of temperature, salinity, and mass on standard mass-independent MO₂ 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 °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.