Intramantle pressure transducers allowed the monitoring of respiration and swimming performance of cannulated and freeswimming squid (IIlex illecebrosus). Jet pressure and oxygen consumption of individual squid were measured simultaneously in a tunnel respirometer at various swimming speeds. The rate of oxygen consumption increased logarithmically with swimming speed up to critical speeds of 70-90 cm/sec (about two body lengths per second). Oxygen consumption values for a400 g squid at 15° C were the highest that have been recorded for marine poikilotherms at this size and temperature: 313 ml/kg/hr for standard metabolism and 1,047 ml/kg/hr for active metabolism at maximum speed. A 40-cm squid (total length) uses about six times more energy per unit distance than a sockeye salmon of similar length at 15° C. The rate of oxygen consumption increased linearly with average jet pressure generated in the mantle cavity and the relationship was highly correlated for speeds of 0.15 0.80cm/sec. The results from telemetric monitoring of jet pressure generated by a free-swimming squid in a 15-m pool and the oxygen-pressure relationship show great promise for studying the activity and bioenergetics of squid in nature
