Although the decisive role of O2 for controlling fish
gill ventilation is unquestionable, there is increasing evidence for the direct role of CO2for stimulating ventilation
in fish [Gilmour, 2001]. CO2
and/or pH sensitive chemoreceptors that enhance gill ventilation during hypercapnia
have been proposed to occur in the gills, and there are some
indications of the occurrence of such chemoreceptors also in
the central nervous system of some fish [Milsom, 2002;
Remmers et al., 2001].