THE INFLUENCE OF TEMPERATURE ON THE SURVIVAL OF SEVERAL SPECIES OF FISH IN LOW TENSIONS OF DISSOLVED OXYGEN

The resistance to low tensions of dissolved oxygen over periods ranging from less than a day to a week was determined for rainbow trout (Salmo gairdnerii Richardson), perch (Perca fluviatilis L.), roach (Rutilus rutilus (L.)), and mirror carp, a domestic form of the common carp (Cyprinus carpio L.) at 10 degrees, 16 degrees and 20 degrees C., tench (Tinca tinca (L.)) at 10 degrees and 16 degrees C., dace (Leuciscus Zeuciscus ( L.)) at 16 degrees and 20 degrees C., chub (Squalius cephalus (L.)) at 20 degrees C., and bleak (Alburnus alburnus ( L.)) at 16 degrees C. At each temperature period of survival decreased with fall in oxygen tension. Rise in temperature between 10 degrees and 20 degrees C. reduced resistance to lack of oxygen of all species except rainbow trout, in which there was no significant difference between resistance at 16 degrees and 20 degrees C. Rise in temperature between 10 degrees and 16 degrees C. did, however, lower resistance considerably. Tench were the most resistant to lack of oxygen and, in general, trout were the most susceptible. At 20 degrees C. mirror carp required a higher tension of oxygen to enable them to survive for a week than did rainbow trout, but for shorter periods could withstand much lower tensions than rainbow trout; at 10 degrees and 16 degrees C. their resistance was intermediate between that of tench and rainbow trout.