HUNTER: CULTURE AND GROWTH OF ENGRAULIS MORDAX 



level to the end and no Artemia was used. Al- 

 though high mortalities on the order of 30 to 300 

 larvae/day occurred in all three experiments be- 

 tween ages 20 to 30 days, the larvae in experi- 

 ment 3, those fed only Brachionus , grew faster 

 (Figure 1) and had a higher survival than in the 

 two groups fed Artemia . From these three exper- 

 iments I concluded that Artemia was an in- 

 adequate food for 20-day-old anchovy larvae and 

 that growth and survival could be increased by 

 continuing to add large quantities of Brachionus 

 after 20 days. Clearly, an adequate food larger 

 than Brachionus was needed for 20-day-old 

 larvae. 



The food selected was the harpacticoid copepod 

 Tisbe furcata. Tisbe is a common contaminant in 

 the seawater system of the Southwest Fisheries 

 Center and can be easily reared on dried foods 

 (Johnson and Olson 1948) or algae (DeVauchelle 

 and Girin 1974). Copepods collected from cultures 

 ranged from SO-yum nauplii to 1,000-/Lim adult 

 females but the typical size was about 650 yum 

 and comparable in size to Artemia nauplii. The 

 first attempt to rear anchovy using Tisbe (exper- 

 iment 4) began as the other experiments except 

 that I began adding Tisbe at age 12 days at the 

 average rate of 180,000/day. At age 20 days the 

 rate was increased to 240,000/day and the 

 Brachionus was allowed to decline. The larvae fed 

 on Tisbe but growth was slow and survival low. 

 The low survival was attributed to an insufficient 

 number of Tisbe in the tank, failure to maintain 

 Brachionus at a high level after 20 days, as I had 



14 



t 12 



I 



H 



o 10 



UJ 



_J 



8 



6- 



0'  ' ' i i ^ I I ' i ' I ' I ' I ' ^ I I ' i  ^ ' I ' I I I I I I 



4 8 12 16 20 24 28 32 36 40 44 48 



AGE (days) 



Figure l. — Laird-Gompertz growth curves for lengths of 

 anchovy larvae in five rearing experiments. Growth equation 

 given in text; parameters for equation in Table 2. (Foods used 

 in experiments 1-5 in Table 1.) 



in experiment 3, and too high an egg stocking 

 density (6,000 eggs). 



The first four experiments established the 

 guidelines needed for experiment 5, the final and 

 successful rearing experiment. Over the first 20 

 days Brachionus, Nannochloris, and Gym- 

 nodinium additions were managed in the same 

 way as in experiment 3. After 20 days, additions 

 of Brachionus were increased above that used in 

 experiment 3 and maintained at a high level 

 until the end of the experiment on day 74. Tisbe 

 additions were begun at age 6 days at an average 

 rate of 260,000/day and increased to 306,000/day 

 after 20 days. These additions were begun before 

 most larvae were capable of feeding upon them in 

 order to bring the copepod density in the tank to a 

 high level at the time feeding on Tisbe became 

 common (about age 12 days, anchovy length, 7-8 

 mm). This procedure is practical because survival 

 of Tisbe in the tank is high and consequently, 

 uneaten animals accumulate. Tisbe additions 

 ended at age 48 days (26 mm) because the quan- 

 tities needed exceeded the capacity of my cul- 

 tures. Although younger larvae did not survive 

 on a diet of Artemia nauplii it seemed possible 

 that larvae 26 mm long might survive because 

 they have a differentiated digestive tract, not 

 simply a straight tube as do younger larvae, and 

 they have a larger gut capacity (C. O'Connell, 

 Southwest Fisheries Center La Jolla Labora- 

 tory, pers. commun.) Rosenthal (1969) showed 

 that Artemia nauplii in the guts of herring larvae 

 were only partially digested whereas digestion of 

 copepods was nearly complete. From this he con- 

 cluded that poor survival of herring fed Artemia 

 could be attributed to digestive inefficiency. Past 

 experience in maintaining adult anchovy at the 

 Southwest Fisheries Center showed that they 

 survived on Artemia; thus, it seemed reasonable 

 that this might first occur when the digestive 

 tract became differentiated. For these reasons I 

 decided to change from a diet of Tisbe and 

 Brachionus to one of Artemia nauplii and Brachi- 

 onus at age 48 days. The change from copepods to 

 Artemia nauplii did not cause a noticeable mor- 

 tality nor a change in growth rate. Adult Artemia 

 were added at age 69 days as some of the fish 

 had metamorphosed and readily ingested adult 

 Artemia. 



In this description of culture I have stressed 

 additions rather than density of food in the tank 

 because I felt they provided a more reliable out- 

 line of culture procedures. Density in the tank 



83 



