NORTHERN SQUAWFISH, PTYCHOCHEILUS-OREGONENSIS, O-2 CONSUMPTION RATE AND RESPIRATION MODEL - EFFECTS OF TEMPERATURE AND BODY-SIZE

Northern squawfish, Ptychocheilus oregonensis (live weight range 0.361 -1.973 kg), O2 consumption was measured with temperature-controlled, f low-through respirometers for >24 h. Mean standard O2 consumption rate of northern squawfish increased with acclimation temperature: 24.3, 4 9.1, 75.0, and 89.4 mg.kg-0.67.h-1 at 9, 15, 18, and 21-degrees-C, res pectively. Q10 analysis showed that O2 consumption rate temperature se nsitivity was greatest at the intermediate acclimation temperatures (1 5-18-degrees-C, Q10 = 4.10), moderate at the lower acclimation tempera tures (9-15-degrees-C, Q10 = 3.23), and lowest at the higher acclimati on temperatures (18-21-degrees-C, Q10 = 1.80). Overall Q10 was 2.96 (9 -21-degrees-C). Body size (W, grams) and temperature (T, degrees Celci us) were related to O2 consumption (M'O2, grams per gram per day) by M 'O2, = 0.00165 W-0.285.e0.105T . Northern squawfish red to white muscl e ratios significantly exceeded those of rainbow trout, Oncorhynchus m ykiss, in cross sections at 50 and 75% of standard length. High metabo lic rates and red to white muscle ratios argue for comparability of no rthern squawfish with active predators such as sympatric rainbow trout .