HUNTER and ROE: THE SPAWNING ENERGETICS OF NORTHERN ANCHOVY 



purchased from bait dealers from September to 

 October in 1977 and 1978 and held in circular 

 tanks 4.6 m in diameter x 1 m deep (volume 

 16.6 m'*) v^ith a fresh seawater inflow of 20 1/min. 

 The fish were exposed to the natural photoperiod 

 but were shielded from direct sunlight. They were 

 fed a ration of Oregon Moist Trout Pellets^ 6 d/wk. 

 The pellets were dispensed with an automatic 

 feeder over a 4-5 h feeding period beginning at 

 0800 h(Leong 1971). 



To estimate the rate of egg maturation ( group 1), 

 8-12 females were sampled twice weekly for 6 wk. 

 The ovaries of nearly all females were immature 

 (no yolked oocytes) when sampling began; the 

 mean standard length (SL) of females was 112.4 

 mm increasing to 116.4 mm in 6 wk. The fish were 

 held at ambient temperatures which ranged from 

 17.9° to 22.0° C and averaged 19.7° C; daily 

 temperatures closely followed those taken at the 

 Scripps Institution of Oceanography pier. We 

 measured standard length, wet weight, and de- 

 termined the frequency distribution of egg sizes 

 within the ovary for each female sampled. We 

 used as a measure of the state of sexual maturity, 

 the mean size of eggs (major axis) within the most 

 advanced spawning batch. The number of eggs 

 within a batch was calculated from the wet weight 

 of the female using the batch fecundity equation of 

 Hunter and Macewdcz (1980) 



loge T = 4.248 + 1.620 \oge W. 



(4) 



(Equation corrected for bias in taking the antilog; 

 Beauchamp and Olson 1973), where T = total 

 number of eggs in a spawning batch and W = 

 female wet weight (without ovary) in grams. 



To measure growth efficiency, two groups 

 (groups 2 and 3) were held under similar tank 

 conditions, but were sampled at 2-wk intervals 

 beginning at the end of November and ending in 

 mid-February. Group 2 was in captivity for about 



1 mo and group 3 for 2 wk prior to sampling. Group 



2 was held at 15.6° C while group 3 was held at 

 ambient temperatures which ranged from 15.2° to 

 17.0° C and averaged 16.0° C. Mean standard 

 length of fish in groups 2 and 3 was 107.2 mm at 

 the beginning and 121.4 mm at the end of the 

 experiment. 



The stomach contents of each fish sampled from 

 groups 2 and 3 were weighed and used to deter- 



mine the mean ration for the experiment. The 

 ration was calculated from the equation 



R = r  s  t + S. 



(5) 



where R = ration, expressed as wet weight food 

 consumed/wet weight fish (in grams); r = rate of 

 gastric evacuation (dashed line. Figure 1); s = 

 average weight of food in stomach/fish weight 

 during the period of gut filling (solid line. Figure 

 1); t = duration of feeding (4 h, group 2; 5 h, group 

 3); and Se - weight of food in stomach/fish weight 



GROUP 2 



.030 



X 

 LlI 



>- 



Q 



o 



OD 



X 



I- .010 - 



UJ 



5 



Q 

 O 

 O 



0.3024 X 



.025 - 



.020 - 



.015 - 



.005 - 



I 



C5 



>- 

 Q 

 O 

 CD 



X 

 UJ 



UJ 



Q 

 O 

 O 



0,4442 X 



12 3 4 



FILLING 



12 3 



EVACUATION 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



ELAPSED TIME (h) 



FIGURE 1. — Rate of stomach filling and gastric evacuation in 

 two groups of northern anchovy fed Oregon Moist Trout Pellets. 

 Weight of stomach contents expressed as a proportion of fish 

 weight; each point is mean for 8-12 fish; feeding began at h 

 (filling) and ended at Oh (evacuation) (arrow); time of day when 

 feeding ended is above arrow. Daily ration calculated from these 

 data was 4.4'7f body weight/d, group 2; and 4.69c body weight/d, 

 group 3. 



217 



