Effects of body mass on physiological and anatomical parameters of mature salmon: evidence against a universal heart rate scaling exponent

摘要

The influence of body mass (M-b) on the physiology of large, adult fish is poorly understood, in part because of the logistical difficulties of studying large individuals. For the first time, this study quantified the influence of M-b on the resting heart rate (f(H)), blood properties and organ masses of adults of a large-growing fish species, the Chinook salmon (Oncorhynchus tshawytscha). Surgically implanted biologgers measured f(H) and acceleration activity in sexually mature, male fish ranging in M-b from 2.7 to 16.8. kg while they roamed freely in a controlled water body at similar to 8 degrees C. Blood parameters (at surgery and at death) and body organ masses (at death) were measured to investigate interrelationships with M-b. The scaling exponents for both f(H) and acceleration activity were not significantly different from zero. The lack of scaling of f(H) with M-b contrasts with the situation for birds and mammals. All blood parameters were independent of M-b, while the masses of the compact myocardium, ventricle and spleen each scaled near-isometrically with M-b. These data raise the possibility that blood oxygen carrying capacity, mass-specific cardiac output and cardiac power output are maintained across M-b in adult Chinook salmon. Biologging and biotelemetry should advance investigations into the effects of M-b on the physiology and behaviour of large fish, where current knowledge lags far behind that of birds and mammals.