282 



Abstract.— Respiration rates of non- 

 feeding adult menhaden induced to 

 swim against currents of various speeds 

 in a large circular flume at 10', 15 . and 

 20 C were measured in order to quan- 

 tify the cost of swimming separately 

 from total metabolic expenditure dur- 

 ing filter feeding. Standard metabolic 

 rates of 0.040, 0.073, and 0.087 mg O,^ / 

 (g wet wt  h) at 10°C, 15°C, and 20X 

 were estimated by extrapolation of the 

 relationship of swimming speed and 

 metabolic rate to zero swimming speed. 

 We determined that when menhaden 

 filter-feed at 200. at the preferred 

 swimming speed of 41.3 cm/s, filtering 

 and specific dynamic action (SDA) ac- 

 count for 59'7c of total energetic expen- 

 ditures. The cost of locomotion was only 

 about 23*7^ of the total expenditure. Our 

 results are compared with routine oxy- 

 gen consumption rates of larval and 

 juvenile menhaden as a function of tem- 

 perature and with extensive metabolic 

 data for sockeye salmon. 



Metabolic rate in relation to temperature and 

 swimming speed, and the cost of filter feeding 

 in Atlantic menhaden, Brevoortia tyrannus 



William K. Macy ill 

 Ann G. Durbin 



Edward G. Durbin 



Graduate School of Oceanography 



University of Rhode Island 



Soutfi Ferry Road 



Narragansett, Rhode Island 02882 



E-mail address (for W K Macy) wkmacyagsosunl gsouri edu 



Manuscript accepted 23 June 1998. 

 Fish. Bull. 97(2):282-293 (1999). 



The Atlantic menhaden, Brevoortia 

 tyrannus, is a pelagic filter-feeding 

 clupeoid inhabiting coastal waters 

 of North America from Maine to 

 Florida. Menhaden adopt filter feed- 

 ing in early juvenile life ( Peck, 1893; 

 June and Carlson, 1971; Friedland 

 et al., 1984 ). Adults are obligate fil- 

 ter feeders and consume phyto- 

 plankton, zooplankton, and detritus 

 larger than about 13 ).im (Durbin 

 and Durbin, 1975). Menhaden are 

 size selective in their feeding, but 

 the basis of selection is passive, re- 

 flecting the size distribution of par- 

 ticulate material in the water rela- 

 tive to the "pore size" of the gill rak- 

 ers; they do not actively pursue in- 

 dividual prey. Energy expenditures 

 during "ram" filter feeding (analo- 

 gous to towing a plankton net) are 

 high (Durbin et al., 1981; Sanderson 

 and Cech, 1992), probably due to the 

 hydrodynaniic drag of the filtering 

 apparatus. However, menhaden 

 compensate for the high cost of fil- 

 ter feeding by regulating their 

 swimming speed to maximize the 

 ratio of net energy gain to expendi- 

 ture (Durbin and Durbin, 1983), as 

 predicted by Ware ( 1975). Our study 

 was undertaken to partition the 

 previously determined energetic 

 cost of filter feeding (Durbin and 

 Durbin, 1983) into two components: 

 the cost of locomotion alone and the 

 cost of filter feeding. This division 



was accomplished by measuring 

 respiration rates of nonfeeding fish 

 forced to swim against currents of 

 known speed and by comparing 

 these respiration rates with those 

 of feeding fish. 



Materials and methods 



Live Atlantic menhaden, Brevoortia 

 tyrannis, were collected from a com- 

 mercial fish trap located in the 

 lower West Passage of Narragansett 

 Bay on 22 and 25 September 1989. 

 The fish were removed from the trap 

 with dip nets and placed in 114-L 

 seawater-fiUed polyethylene gar- 

 bage cans for transport to the 

 Narragansett Bay Campus. Menha- 

 den were randomly divided and 

 placed with three open-flow circu- 

 lar fiberglass tanks, 1.7 m in dia- 

 meter and 0.5 m deep, supplied with 

 sand-filtered seawater. Acclimation 

 to the three test temperatures ( 10°, 

 15", and 20 C) began 5 October 

 1989, starting from the ambient 

 temperature, 18°C, with a rate of 

 change of about l°C/d. Ambient sa- 

 linities varied between 28 and 30 

 ppt. The fish were considered accli- 

 mated after maintenance for 30 

 days at the target temperature. 

 Menhaden were fed salmon starter 

 mash (Ziegler Bros., Inc.) at a rate 

 of about 4.5'7f of dry food:live 



