Despite having a very high mass-specific basal metabolic rate adult Humboldt squid are able to depress total metabolism by 35% during their daily migration to the mesopelagic oxygen minimum zone (Seibel 2014). 50% of the ATP consumed under hypoxia in this squid comes from anaerobic processes. This adaptation likely allows these top predators to keep themselves from starving to death as they wait for their prey to return to shallower waters at night. Btw these squid can grow up to 2M 50kg.