Behavioral ecophysiology of dungeness crabs during feeding and digestion in hypoxia

Cancer magister inhabits areas frequently subject to periods of hypoxia. In hypoxia, digestive processes pose an additional physiological burden to crabs already attempting to maintain adequate oxygen uptake. Crabs tended to cease feeding below 3.2 kPa, resuming feeding when dissolved oxygen levels were rapidly raised to 6 kPa. In a 10.5-21 kPa DO gradient starved and fed crabs showed no preference for any area of the apparatus. In a 2.5-10.5 kPa DO gradient, starved and fed crabs showed significant preference for the highest oxygen concentration. Starved crabs were less likely to enter hypoxic waters to feed; those that did moved food to higher oxygen concentrations prior to feeding. In the field, starved crabs traveled up to 1.3 km within 6 hours, while postprandial crabs, moved very little during the first 48 hours. The present study suggests Cancer magister may use behavior to minimize the use of physiological mechanisms, and maximize foraging and digestive processes.