MAV: EFFECTS OF DELAYED INITIAL FEEDING 



hatching and a starved control Yolk was com- 

 pletely used up in unfed larvae by day 4, and 

 on this day only a minute amount was left in 

 fed larvae. The survival curve for unfed larvae 

 passed the 50<^f line between days 11 and 12. 

 roughly the same as the starvation time given 

 by Hubbs (1965) for larval grunion at 18° C. 

 The starved control larvae were all dead by day 

 21. There is a direct relationship between per- 

 cent survival of original larvae to day 20 and 

 the day of first feeding (Table 1). The number 



Table 1. — Sur\-ival to day 2U of larvae with different 

 times of initial feeding. 



Day of 



first 

 feeding 



Original 

 number 

 of larvae 



Number of 

 larvae alive 

 when food 

 first offered 



Number of 



larvae 



alive on 



day 20 



Percent survival 

 to day 20 



Original 



larvae 



Larvae 



aliva when 



food first 



offered 



of larvae which survived to day 20, expressed 

 as a percentage of those which were alive when 

 food was first offered, is also listed in Table 1. 

 This figure never dropped below 40'^r, and all 

 of the previously unfed larvae alive in container 

 #6 on day 16 (i.e., four larvae) began feeding 

 when food was supplied and survived to day 20, 

 and their general appearance and behavior in- 

 dicated that they would easily have survived 

 longer, had the experiment been prolonged. 



In the group of larvae which was fed for the 

 first time on day 7, 11 larvae were found dead 

 on the morning following the day of first feed- 



ing; 9 dead larvae had food in their guts and 

 5 of these had guts which were bright orange 

 and so stuffed with Artemia nauplii that the 

 abdomen was noticeably distended. In the 

 group fed initially on day 10, all eight larvae 

 found dead the next morning had food in their 

 guts, and four of these had bright orange, packed 

 guts. On day 14, only one out of four dead lar- 

 vae, found in the container which had been fed 

 for the first time on the previous day, had food 

 in its gut and showed the orange and bulging 

 abdomen noted in dead larvae from the previous 

 two groups. 



GROWTH 



The increase in length and dry weight of 

 larvae sampled from the "fed" supply containers 

 is presented in Table 2. The rate of growth 

 was higher from day 16 on; variability like- 

 wise increased after this time, an example of 

 the "growth depensation" which is commonly 

 found in growing fish (Ricker, 19.58). On day 

 7, the hypural elements were beginning to form 

 along the posterior ventral margin of the noto- 

 chord, and on day 10 the tip of the notochord 

 was beginning its upward flexion. The greatest 

 increase in length occurred between days 1 and 

 4, and owing to the upturning notochord the 

 mean length actually decreased between days 

 13 and 16 (Table 2) . On day 4, only the cleith- 

 rum and a very few cranial and branchial ele- 

 ments were ossified, but by day 10 about half 

 of the vertebrae (the anterior ones) and some 

 of the caudal rays were beginning to take up 

 alizarin, and by day 16 all vertebrae and hy- 

 pural elements were ossified. 



Table 2. — Length and weight of fed and unfed larvae, x = mean, SD 

 deviation, n = number of larvae measured. 



standard 



417 



