CO2 and H+ Excretion By Swimming Coho Salmon, Oncorhynchus Kisutch

Abstract

ABSTRACT Coho salmon, Oncorhynchus kisutch (Walbaum), were swum at constant speed in a ‘Brett-type’ tunnel respirometer. Blood , and pH as well as total CO2 content and red blood cell pH were unchanged during swim ming. The RE (respiratory exchange ratio) was slightly less than 0·7 when the fish was swimming in normal sea water, indicating that some CO2 is retained by the fish. Lowering seawater bicarbonate concentration increased HCO3− transfer, presumably because of passive bicarbonate loss. A reduc tion in seawater pH from 7 ·95 to 7 ·1 sharply reduced both CO2 and hydrogen ion transfer, resulting in very low RE values of about 0 ·2. Hydrogen ion excretion was elevated during prolonged swimming following high speed swimming activity. It would appear that CO2 and hydrogen ion transfer by fish need not be matched and changing internal and external conditions can have a marked and separate effect on hydrogen ion and CO2 excretion and therefore on the RE value.