Boggs: Bioenergetics and growth of Engraulis mordax 



563 



0.5 



10 



15 



20 



25 



Swimming speed (cm/s) 



Figure 5 



Comparison of other engraulid metabolic rate estimates with 

 model predictions for 4, 10, and 25g northern anchovy at 

 17°C. The anchoveta curve is from Villavicencio (1981, temp. 

 17 C C). Respiration rates of (A) actively swimming lOg north- 

 ern anchovy at 15°C and, based on energy losses during zero- 

 ration treatments, (B) exercised 16.9-17.8g fish at 21°C, 

 (C) non-exercised 13.5-16.9g fish at 18°C, and (D) non- 

 exercised 12.3 g fish at 15.2°C as measured by Kaupp et al. 

 (unpubl. data). 



clupeoids (7-13.5%, Takahashi and Hatanaka 1960, De 

 Silva and Balbontin 1974, Hunter and Leong 1981, 

 Blaxter and Hunter 1982). However, gross conversion 

 efficiencies this high are found in many juvenile fishes 

 (60% Hatanaka and Takahashi 1956, 34% Elliott 

 1976a, 10-25% Brett and Groves 1979). The impor- 

 tance of different results in such studies is difficult to 

 judge, because of differences in the assumptions, ex- 

 pressions (percentages of mass or energy), experimen- 

 tal conditions (size, maturity, temperature, activity), 

 and the rarity of error estimates. 



A model for adult anchovy metabolism 



A model for anchovy metabolism was derived by using 

 the estimates from the present study, data on closely 

 related species, and general principles relating swim- 

 ming speed and metabolism to fish size. The model re- 

 quired estimates of (1) standard metabolism, (2) swim- 

 ming metabolism, (3) the effect of fish size on standard 

 and swimming metabolism, and (4) the effect of tem- 

 perature. These estimates are provided in the follow- 

 ing sections. 



Standard metabolism Standard metabolism was 

 estimated by extrapolating to zero swimming speed 

 from the rates estimated at two speeds. An exponen- 

 tial relationship (Brett 1964) was assumed, 



Q M = ae bv cal • g" l  day 



(8) 



K values in treatment combinations with low ration or 

 high speed compared with the high-ration, slow-speed 

 treatment. Contrarily, K values in the high-ration, 

 slow-speed treatment were much higher than the 

 12.8% reported by Hunter and Leong (1981) for north- 

 ern anchovy even though the fish in the present study 

 were exercised and fed smaller rations. Hunter and 

 Leong (1981) fed fish 124 cal • g - * • day - 1 of semi-dry, 

 pelleted trout food (the caloric equivalent of a ration 

 of 16% of wet body mass/day in copepods). At very high 

 rations, the proportion of food energy lost to X, I, and 

 SDA may increase (Paloheimo and Dickie 1966, Brett 

 1979, Brett and Groves 1979), causing K to decline. 



The euphausiids used for food and the rations (Table 

 1) in the present study were similar to the zooplankton 

 rations of 1.4-4.9% observed in nature (Blaxter and 

 Hunter 1982). So, although X, I, and SDA vary with 

 food composition (Elliott 1976b, Brett and Groves 1979, 

 Tandler and Beamish 1979 and 1980) and may increase 

 at ration levels higher than those in nature, the energy 

 budget generalizations in Equations (6) and (7) should 

 be applicable to adult anchovy in the wild. 



The observed range of gross conversion efficiencies 

 (1-39%) extended higher than the range reported for 



where the metabolic rate exclusive of SDA (Q M ) con- 

 sists of standard metabolism (Q = a) increased by 

 a factor (e bV ) for the cost of swimming, where V is 

 swimming speed. The energy losses measured in the 

 present study resulted from fish exercising half the 

 time and resting half the time, so 



Q M = [0.5 (ae bV )] + [0.5 (a)] cal -g^ 1 -day 



-l 



(9) 



The metabolic rate estimates (Q M = 0.9x 17.6 = 15.8, 

 and 0.9 x 28.2 = 25.4 cal • g- l  day- * ) from the two ex- 

 ercise levels (V = 8.7 and 21.1 cm/s, respectively) were 

 substituted for Q M and V in Equation (9). The result- 

 ing simultaneous equations were solved, and Q was 

 calculated to be 12.1 cal • g _1 • day -1 at V = 0. Assum- 

 ing an oxycalorific equivalent of 3.24 cal/mg 2 (Elli- 

 ott and Davison 1975), the standard metabolic rate was 

 0.156mg 2 -g- 1 h _1 . Assuming the same metabo- 

 lizable fraction (0.9) and oxycalorific equivalent, energy 

 losses of 9.7 cal -g -1 - day _1 at the lowest activity 

 levels measured by S. Kaupp et al. (unpubl. data,) 

 amounted to 0.112mg 2 -g _1 -h _1 . The standard 

 metabolism of 12. 6g anchoveta at 17°C (Villavicencio 

 1981) was 0.135 mg 2  g" 1 • h" 1 . These values (Fig. 5) 



