Northern squawfish Ptychochelius oregonensis, O2 consumption rate: Effects of temperature and body size
Northern squawfish, Ptychocheilus oregonensis (live weight range 0.361–1.973 kg), O 2 consumption was measured with temperature-controlled, flow-through respirometers for >24 h. Mean standard O 2 consumption rate of northern squawfish increased with acclimation temperature: 24.3, 49.1, 75.0, and 89.4 mg∙kg −0.67 ∙h −1 at 9, 15, 18, and 21 °C, respectively. Q 10 analysis showed that O 2 consumption rate temperature sensitivity was greatest at the intermediate acclimation temperatures (15–18 °C, Q 10 = 4.10), moderate at the lower acclimation temperatures (9–15 °C, Q 10 = 3.23), and lowest at the higher acclimation temperatures (18–21 °C, Q 10 = 1.80). Overall Q 10 was 2.96 (9–21 °C). Body size ( W , grams) and temperature ( T , degrees Celcius) were related to O 2 consumption ( , grams per gram per day) by W −0.285 ∙ e 0.105 T . Northern squawfish red to white muscle ratios significantly exceeded those of rainbow trout, Oncorhynchus mykiss , in cross sections at 50 and 75% of standard length. High metabolic rates and red to white muscle ratios argue for comparability of northern squawfish with active predators such as sympatric rainbow trout.