FISHERY BULLETIN: VOL. 79, NO. 2 



50 

 gi 40 



T3 



»•- 

 O 



30 - 



9> 20 



10 - 



JAN FMAMJ JASON DEC 

 MONTHS 



Figure 8. — Annual fat cycle of northern anchovy. Fat content 

 expressed as a percentage of dry weight for various months in 

 1965, 1966, and 1967. Data from Lasker and Smith (1977). 



from the previous spring and summer may be used 

 the following year to support reproduction. Fat 

 stores may not be used directly to promote egg 

 production, which are largely protein, but rather 

 to provide energy needed for metabolism, per- 

 mitting energy from food to be used for egg 

 maturation. 



We calculated the number of spawnings that 

 could be financed by the annual decline in fat 

 stores, assuming that this energy or its equivalent 

 is used for reproduction. We used the average 

 minimum and maximum fat level for the 3 50- 

 (Table 5) to estimate the grams of fat annually 

 available for reproduction. Using the dry weight, 

 fat, and wet weight relation (Equation (1)), we 

 calculate that a 16.4 g female would store annu- 

 ally 13,831 cal of fat (Table 4) which is equivalent 

 to 13 spawning batches. Thus, about two-thirds of 

 the annual cost of egg production can be accounted 

 for by the annual decline in fat stores. 



The rate of increase in fat in the spring was 

 similar in the 3 yr (1965-67) although the timing of 

 the onset varied by 2-3 mo. The maximum rate 

 occurred in the late spring or summer over a 

 period of about 63 d (Table 5). Nearly all fat stores 

 were accumulated over this period; on the average 

 fat increased from 16.5 to 40.5% of the dry weight 



Table 5. — Maximum and minimum fat content of female 

 northern anchovy from Southern California Bight in 1965-67.' 



over the 63 d. Thus, calories would accumulate in 

 a 16.4 g fish at a rate of about 200 cal/d or the 

 caloric equivalent of one spav^ming batch would be 

 stored about every 5 d. 



This analysis indicates that the annual spring 

 bloom might regulate the reproductive potential 

 of the northern anchovy population. This effect 

 may have a 1-yr lag because fat accumulated in 

 the late spring and summer would presumably 

 be used to support reproduction the following 

 year because most spawning occurs in February 

 through April. On the other hand, if 20 spawnings 

 occur, about one-third of them would have to be 

 supported from energy gained during the current 

 year. Thus, production of plankton might have an 

 effect on egg production late in the spawning 

 season, but the major effect of the spring bloom on 

 reproduction may occur the following year. 



ENERGY BUDGET FOR FEMALE 

 GROWTH AND REPRODUCTION 



In this section we calculate an annual energy 

 budget for reproduction and grovid;h in female 

 northern anchovy based on relationships estab- 

 lished in past sections and in the laboratory ration 

 study outlined below. Food ration (R) may be 

 partitioned into energy losses of metabolism (Q), 

 excretion (X), digestive losses (/), reproductive 

 costs (S), gains in growth {N) and fat stores (F) 

 where 



i? = Q+X + / + S + iV + F. 



(7) 



We do not estimate Q, X,or I, but rather calcu- 

 late for laboratory females the gross conversion 

 efficiency (C) where 



C = 



S + N + F 

 R 



(8) 



Variables A^^ and F were calculated by subtracting 

 weight and fat content of females determined at 

 the beginning of the experiment from that deter- 

 mined at the end (Table 6); reproductive cost S 

 was simply the increase in weight of the ovary 

 since the fish did not spawn during the experi- 

 ment; and R was calculated using Equation (5). 



The coefficient C was used to estimate ration for 

 natural populations using 



R 



S + N 



'Data illustrated in Figure 8; from Lasker and Smitti (1977). 



(9) 



224 



