Scope for activity in the crayfish Pacifastacus leniusculus.

The scope for activity of the crayfish Pacifastacus leniusculus was determined between 5 and 30 degrees C (incipient lethal of 33 degrees C). Standard oxygen consumption rate (VO2) ws low (e.g., 17 ml x kg-1 x h-1 at 20 degrees C); and it increased with temperature over the entire range (Q10 = 2.09 for 5-25 degrees C). Active VO2 increased with temperature (Q10 = 1.76) to a maximum at 20 degrees C (VO2 = 176 ml x kg-1 x h-1), and then decreased. Scope for activity likewise showed a maximum at 20 degrees C (VO2 - 158 ml x kg-1 x h-1) and decreased at higher temperatures. Comparison with fish studies indicates these values represent a relatively well-developed oxygen uptake ability in this decapod crustacean. At 20 degrees C crayfish active VO2 is a significant fraction of that shown by highly active VO2 is a significant fraction of that shown by highly active species such as sockeye (29%), and moderately active species such as goldfish (57%), bullhead (62%), and bass (78%); and it is much greater than active VO2 for sluggish species such as gobiids (> 300%). Also, crayfish scope for activity between 5 and 20 degrees C is virtually identical to scopes for bullhead and bass because crayfish have lower standard VO2 than either of these fish.