Metabolic rate in relation to temperature and swimming speed, and the costof filter feeding in Atlantic menhaden, Brevoortia tyrannus

Respiration rates of nonfeeding adult menhaden induced to swim against curr ents of various speeds in a large circular flume at 10 degrees, 15 degrees, and 20 degrees C were measured in order to quantify the cost of swimming s eparately from total metabolic expenditure during filter feeding. Standard metabolic rates of 0.040, 0.073, and 0.087 mg O-2/(g wet wt . h) at 10 degr ees C, 15 degrees C, and 20 degrees C were estimated by extrapolation of th e relationship of swimming speed and metabolic rate to zero swimming speed. We determined that when menhaden filter-feed at 20 degrees C, at the prefe rred swimming speed of 41.3 cm/s, filtering and specific dynamic action (SD A) account for 59% of total energetic expenditures. The cost of locomotion was only about 23% of the total expenditure. Our results are compared with routine oxygen consumption rates of larval and juvenile menhaden as a funct ion of temperature and with extensive metabolic data for sockeye salmon.