Squid (Loligo Forbesi) Performance And Metabolic Rates In Nature

Squid are the fastest swimming invertebrates, but the metabolic cost of speed, as assessed in swim-tunnels, is several-fold higher than in fish, making squid appear uncompetitive. Because oxygen consumption can be correlated with jet pressure, it is possible to monitor pressure and thus estimate performance and energy costs in nature. Tracking in course and depth gave a 3-D view of squid (Loligo forbesi) activities and costs for nearly three animal-weeks; five days of this included telemetry of jet pressures. These 2-5 kg loliginids hovered off-bottom most of the time, perhaps to avoid predation or damage to delicate skins. Hovering consumes about 50 ml O2 kg-1h-1, twice as much as resting on bottom and half of overall average costs. Jet pressures were not well correlated with horizontal movements or tidal cycles, suggesting squid may “soar” to reduce the cost of remaining in active current areas, acting as sit-and-wait predators. Maximal aerobic jetting was rare and usually associated with vertical climbing. Thus, these squid appear to have adopted a suite of natural behaviours which compensate for those aspects of their physiology which are least competitive with fishes and accentuate those which are most competitive.