Abstract. - Changes in total body 

 energy content of adult (total length 

 ~9cm, wet mass ~9g) northern an- 

 chovy Engraulis mordax were esti- 

 mated by sampling captive groups 

 swimming at 8.7 and 21.1 cm/s for 12 

 hours daily. Anchovy were fed eu- 

 phausiids at rations of 5 and 3.4% of 

 fish wet mass per day (~54 and 37 

 cal • g fish wet mass -1 • day -1 , re- 

 spectively). Gross energy conversion 

 efficiency increased with ration 

 levels and declined with swimming 

 speed, ranging from 39% to 1%. Dry 

 mass and lipid losses were estimated 

 in fasting fish swimming at the same 

 speeds. Energy losses were 17.6 and 

 28.2cal-g fish wet mass^-day -1 

 at the slow and fast speeds, respec- 

 tively. The proportion of food energy 

 used for growth and maintenance 

 metabolism was about 65%. A model 

 derived for adult anchovy metabo- 

 lism was consistent with observed 

 growth and reproduction rates, and 

 the few measurements of ration and 

 swimming speed in nature. 



Bioenergetics and Growth 

 of Northern Anchovy 

 Engraulis mordax 



Christofer H. Boggs 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service. NOAA 



2570 Dole Street. Honolulu, Hawaii 96822-2396 



Manuscript accepted 24 June 1991. 

 Fishery Bulletin, U.S. 89:555-566 (1991). 



The incorporation of energy from 

 food into growth and reproduction by 

 northern anchovy Engraulis mordax 

 has been roughly quantified. Prey 

 abundance influences the rate of an- 

 chovy reproduction during subse- 

 quent years, according to time-series 

 analysis (Smith and Eppley 1982). 

 Abundant food probably results in 

 more energy intake and storage. 

 Energy available for growth and re- 

 production by northern anchovy in 

 the wild has been estimated at 12.8% 

 of energy intake, based on laboratory 

 measurements of gross energy-con- 

 version efficiency (Hunter and Leong 

 1981). At 12.8% efficiency, the daily 

 ration needed for average growth 

 and reproduction was estimated to be 

 4-5% of fish wet mass (Hunter and 

 Leong 1981), which is towards the 

 high end of the range of field esti- 

 mates for engraulids (Blaxter and 

 Hunter 1982). However, food in- 

 take and energy demands vary. An 

 energy budget model could help ex- 

 plain and predict the effect of food 

 availability on anchovy growth and 

 reproduction. 



Gross energy -conversion efficiency 

 is the net energy remaining after 

 food assimilation and metabolic losses 

 divided by the total energy consumed 

 as food. Thus, gross energy-con- 

 version efficiency should tend to in- 

 crease with ration and decrease with 

 increased swimming activity. The im- 

 pact of swimming activity on clupeoid 

 metabolism has been described for 

 Pacific sardine Sardinops caerulea 

 (Lasker 1970), Atlantic menhaden 



Brevoortia tyr annus (Durbin et al. 

 1981), and Peruvian anchoveta E. 

 ringens (Villavicencio 1981). Esti- 

 mated metabolic rates of adult north- 

 ern anchovy (S. Kaupp, R. Lasker, 

 and R. Leong, a table of estimates 

 obtained from J.R. Hunter, South- 

 west Fish. Sci. Cent., NMFS, NOAA, 

 P.O. Box 271, La Jolla, CA 92037, 

 unpubl. data) are about twice as high 

 as those of its congener, E. ringens, 

 at swimming speeds of about 1 body 

 length/s. This difference is not small 

 in relation to the overall energy bud- 

 get of engraulids; therefore, better 

 estimates of swimming metabolism 

 are needed. The present study mea- 

 sures the energy expended for 

 metabolism by northern anchovy at 

 different swimming speeds, exam- 

 ines the effect of ration and metabolic 

 rate on gross energy-conversion ef- 

 ficiency, and derives a model for 

 adult anchovy metabolism. 



Methods 

 The flume 



Juvenile and adult northern anchovy 

 ranging from 2 to 7g wet mass were 

 purchased from live-bait dealers in 

 February 1984 and acclimated to 

 laboratory conditions for 2-4 months 

 prior to being transferred to an open 

 flume for exercising the fish. Pro- 

 cedures for keeping live anchovy are 

 described in Leong (1971) and 

 Hunter and Leong (1981). Fish were 

 fed 0.09g Biomet trout pellets per 

 fish per day until the study began. 



555 



