Swimming Speed and Metabolic Rate during Routine Swimming and Simulated Diel Vertical Migration of Sergestes similis in the Laboratory

摘要

Sergestes similis (Hansen, 1903) is a common mesopelagic verticallymigrating shrimp common in the temperate and subarctic North Pacific Ocean.The species is a diel vertical migrator, although it remains primarily above theoxygen minimum layer in regions such as off California where the layer is welldeveloped. This shipboard study with a computer-controlled swim tunnel providedthe first continuous examination of this species' swimming behavior andmetabolism over a 24-hr cycle. Sergestes similis swam at a routine speed ofaround 4.4 to 4.95 cm sec-I. Burst speeds ranged from 14 to >20 cm sec-1.Swimming speeds during the day, at low temperatures simulating those at daytimedepths, were similar to those at night at the higher temperatures characteristicof the surface. Night metabolic rates were higher than in the day,especially during the early night when most feeding activity may take place.Swimming speeds during times of simulated vertical migration averaged slightlyfaster than those of routine day or night swimming, averaging 6.2 cm sec- lduring the time of upward migration and 5.4 cm sec-1 during simulated downwardmigration, but the difference was not significant. Downward migration isnot accomplished by passive sinking. Calculations based on observed swimmingactivities and metabolic rates indicate that vertical migration confers a clearmetabolic energy savings to S. similis over remaining resident in surface waters,though this result may not be applicable to other vertical migrators and is likelymoderated by decreased feeding opportunities at depth.