TRUEBLOOD, Lloyd A.*; SEIBEL, Brad A.; GILLY, William F.; University of Rhode Island; University of Rhode Island; Stanford University: Breath holding squid: Physiological constraints on vertical migrations of Dosidicus gigas

Squids found in shallow waters have been shown to have high oxygen demands and limited oxygen transport capacity. As a result, such species are thought to be intolerant of waters with low oxygen content. However, our submersible observations and telemetry data demonstrate that one active shallow squid, Dosidicus gigas, migrates diurnally between the well-aerated shallow waters and mid-depths (300-600 m) where oxygen content is less than 1% of air saturation. Metabolic and enzymatic measurements show that D. gigas� routine metabolic rate is substantially higher than species of squid living permanently in oxygen depleted water. D. gigas is presumably unable to support its metabolism aerobically in this environment. Possible alternatives include sustained anaerobisis, metabolic suppression, or some combination of these strategies for survival in this �oxygen minimum layer� until its nightly return to shallower waters.