HUNTER: CULTURE AND GROWTH OF ENGRAULIS MORDAX 



copepods ingested by larvae also increased with 

 larval length as expected (Arthur 1956). 



Tisbe occurred throughout the rearing tank but 

 the greatest concentrations occurred on or near 

 the walls and on the bottom. Free swimming 

 copepods were plentiful near the walls of the tank 

 because Tisbe frequently leave the wall for short 

 periods. Anchovy larvae captured Tisbe that were 

 on the walls as well as free-swimming individu- 

 als. A pelagic copepod would be preferable to one 

 that prefers surfaces such as Tisbe furcata but I 

 have not been able to culture pelagic species in 

 sufficient quantities for rearing work.^ 



GROWTH 



The length data from each of the five experi- 

 ments were fitted to the Laird-Gompertz growth 

 equation (Laird et al. 1965) using Marquardt's 

 Algorithm for fitting nonlinear models (Conway 

 et al. 1970). The equation for length was: 



Loe 



e-«<) 



where L - standard length in millimeters 

 Lq = initial length at time 



Aq = rate growth at time 

 a = rate of decay of growth. 



A fit of the weight data from experiment 5 was 

 also made to the Laird-Gompertz equation: 



The length-weight relationship for larvae in 

 experiment 5 was derived from the above two 

 equations by James Zweifel (Southwest Fisheries 

 Center) and had the form 



In W = In Wo + K^^r 



1 - 



Kl - In (L/Lq ) 



Kr 



/3/a 



The Laird-Gompertz equation gave an excellent 

 fit to the growth in length and in weight and to 

 the length-weight relationship (Figures 2-4, 

 Table 3). The curvilinear nature of the length- 

 weight data evident in the log-log plot (Figure 4) 

 clearly indicates that a linear fit to log of length 

 and weight would lead to inaccurate estimates. 



The growth of anchovy larvae in experiment 5 

 was about the same as that recorded by Kramer 

 and Zweifel (1970) for anchovy fed wild plankton 

 at 17°C. At age 34 days, the last day of their 

 experiment, the mean length of larvae was 17.4 ± 

 1.8 mm and that in experiment 5 at age 34 days 

 was 19.7 ±1.0 mm. Thus, over at least the first 34 

 days, growth on the cultured food diets was about 

 the same as that on wild plankton. 



SURVIVAL AT METAMORPHOSIS 



The object of this experiment was to determine 

 how long newly metamorphosed anchovy larvae 

 can survive without food. Most adult fishes and 

 presumably the anchovy can withstand prolonged 

 periods of starvation of weeks or months. On the 



W = Woe 



Kwn 



.-^') 



where W = dry weight in milligrams 

 Wo = initial weight at time 



Bq = rate growth at time 

 fi = rate of decay of growth. 



^At present our copepod culture system is composed of 10, 

 90-liter, glass, rectangular tanks maintained at 17° to 19°C. 

 The Tisbe are given green algae, either Tetraselmis or Nan- 

 nochloris, which is grown using commercial plant fertilizer (fish 

 emulsion). An inoculation of 50,000 to 100,000 copepodid- 

 adult stages yields on the average 500,000 copepods in these 

 stages in 2 weeks. A tank is drained, harvested, and reestab- 

 lished 5 days a week producing about 2.5 x 10® copepodid-adult 

 stages per week, which is sufficient to rear one group of anchovy 

 in the manner described. Occasional htirvests of over a million 

 in 2 weeks have been obtained suggesting that major improve- 

 ments in the technique are possible. Contamination by 

 Brachionus has been a problem because it increases the amount 

 of algae that must be added to the culture. A more detailed 

 description of this culture system would be premature but a 

 description of a similar method of mass culture exists (De- 

 Vauchelle and Girin 1974). 



40 



35 



30 



- 25 



E 

 E 



f 20 



z 



UJ 



_) 



15 



i±L 



i±l 



ill 



ill 



1.^' ■!■ 



I , 



15 20 25 30 35 40 45 50 55 60 65 70 75 

 AGE (days) 



Figure 2. — Laird-Gompertz growth curve for length of anchovy 

 larvae in experiment 5 and mean length ± 2 SE. Parameters 

 for equation given in Table 2. 



85 



