FISHERY BULLETIN: VOL. 70. NO. 3 



sets of observations was made of larvae ranging 

 in age from to 36 days. 



Swimming and feeding behaviors were also 

 recorded on motion picture film for subsequent 



100 



19 41 32 46 38 31 30 19 14 15 14 



1 1 1 1 I 1 1 n 



INTERMITTENT SWIMMING 



,--8 



REST 



4 6 



AGE (day*) 

 N 



8 10 



10 



8- 



a 



o 



z 



5 



UJ 4 

 Ui 



19 41 32 46 38 31 30 19 14 15 14 



-| 1 I I 1 T 1 1 1 I 1~ 



i I L 



4 6 



AGE (day*) 



10 



Figure 1. — Proportion of time spent in rest and inter- 

 mittent swimming (top panel), and feeding (bottom 

 panel) by anchovy larvae during the first 10 days of 

 larval life. Points are mean percent ± 2 X SE, for 

 each day; the number of observations (N) is given at 

 top of graphs. 



analysis. For cine photography the larvae were 

 placed in round plastic containers 1 cm deep and 

 8 to 25 cm diameter which had black opaque walls 

 and a transparent bottom. The tank was illumi- 

 nated from above by a reflector flood lamp oper- 

 ated below rated voltage. A water bath was in- 

 serted between the lamp and the tank to prevent 

 heating the water. Light from the lamp was 

 focused with a fresnel lens on the lens of the 

 motion picture camera beneath the tank. The 

 camera arrangement and lighting system was 

 similar to the one used by Baylor (1959) for pho- 

 tographing transparent organisms with infrared 

 radiation. From the position of the camera the 

 subject was silhouetted against an intensely 

 bright background because the light was focused 

 directly on the camera lens. Thus, low sensi- 

 tivity, high resolution, and high contrast film 

 could be used. Swimming and feeding larval 

 anchovy were photographed with a high-speed 

 camera at 128 fps (frames per second) using 

 AHU microfile film manufactured by the East- 

 man Kodak Company.' Photographic analysis 

 of feeding was restricted to larvae that fed on 

 food particles 100 /x or larger in diameter be- 

 cause I was not able to resolve smaller food par- 

 ticles and still maintain the larvae in a reason- 

 ably large photographic environment. Much 

 slower camera speeds — 1 to 2 fps — were used to 

 estimate swimming activity. 



SWIMMING BEHAVIOR 



CHANGES IN THE TYPE OF SWIMMING 

 WITH DEVELOPMENT 



During the first 2 days of larval existence, 

 anchovy larvae exhibited little locomotor activi- 

 ty. Over 90 V^ of the time they floated motionless 

 in the water (Figure 1) . Usually the head was 

 directed downward and often the motionless 

 yolk-sac larvae were transported slowly by water 

 currents. Occasionally, they executed a brief 

 but intense burst of swimming. These bursts 

 of swimming, which I called continuous swim- 

 ming, occurred about once a minute and lasted 



' Use of trade names does not imply endorsement by 

 the National Marine Fisheries Service. 



822 



