Oxygen consumption and gill water flow in the dogfish Scyliorhinus canicula L.

When sharks and dogfish are at rest on the sea bottom, gill ventilation is produced by the action of the branchial musculature and elastic recoil of the visceral skeleton (Hughes & Ballintijn, 1965). Water flows across the gills as a result of an increase in pressure in front of the gills and of suction behind them. During the swimming of some related forms such as the leopard shark, Triakis semifasciata (Hughes, i960) and the sand shark, Carcharias taurus (von Wahlert, 1964), it has been observed that the normal respiratory movements cease when the fish swims above a given speed. Under these conditions ventilation of the gills is achieved by the activity of the red muscles which are known to be mainly concerned during the slow swimming movements of these fish (Bone, 1966; Roberts, 1968). However, ventilation solely by this 'ramjet' method has not been observed in the common British dogfish, Scyliorhinus canicula, so far as we have been able to discover. The present experiments attempted to measure the standard oxygen consumption of this species and to determine the effect of increasing the rate of water flow past the fish. The volume of water pumped through the gills and the properties of the gill resistance were studied by measuring changes in flow with alterations in hydrostatic pressure across the gills. Both of these features are involved as the fish changes from the situation when it is pumping at rest on the sea bottom and begins to swim.