FISHERY BULLETIN: VOL. 79, NO. 1 



Table l. — Summary of spawning batches and dates of anchovy 

 larvae of various total lengths used in experiments on burst 

 swimming performance. Data for total length are X±2 SE. 



Total length 

 (cm) 



Batch 

 of eggs' 



Date spawned 

 (1979) 



Number of 

 larvae sampled 



Batch D was infected by bacteria and therefore rejected. 



the refractive index (e.g., larvae in water) de- 

 flected the light from the focus spot on the glass 

 plate and were seen as bright spots against a dark 

 background. 



The stimulus initiating a maximum fast start 

 and swimming burst was a 10 ms, 3 V/cm square 

 wave electric shock delivered via two grids in the 

 water bath. Responses were recorded on Kodak^ 

 Plus-X 16 mm movie film at a framing rate of 250 

 Hz. Experiments were performed at 17° C. 



Movie film was analyzed frame by frame. The 

 progression of the head was traced from frame to 

 frame and the mean distance travelled was calcu- 

 lated as described by Hunter (1972) avoiding ar- 

 tifacts due to lateral oscillations of the head as- 

 sociated with propulsive movements. Speeds were 

 calculated from the distances travelled and the 

 elapsed time between measurements. Elapsed 

 time was calculated from the product of number of 

 frames between measurements divided by the 

 framing rate. 



RESULTS 



The percentage of larvae responding to the 

 nonspecific electric shock stimulus increased with 

 age to a maximum of 88-100% (mean 95±4%; n = 

 7) after 125 h measured from the time of spawning 

 (Figure 1). This corresponds to the age at which 

 larvae raised under the same conditions begin in- 

 termittent swimming, i.e., periods of low speed 

 swimming alternating with periods of rest 

 (Hunter 1972). 



The response to the stimulus was a fast start 

 followed by a period of continuous high speed 

 (sprint) swimming. Fast starts and sprint speeds 



Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



144 



100 



80 



60 



40 



20 



% STARTLE RESPONSE 



E INTERMITTENT 

 MMING 



% TIME FEEDING 



_L 



50 100 150 200 250 300 



AGE FROM TIME EGGS SPAWNED (h) 



350 



Figure l.— Percentage responses (n = 20-50) to a 3 V/cm d.c. 

 electric shock by northern anchovy larvae as a function of age, 

 calculated from the time the eggs were spawned. The curve was 

 fitted by eye. The curves for the time spent in intermittent 

 swimming and in feeding are from Hunter (1972). 



are defined as burst activities (see Webb 1975; 

 Hoar and Randall 1978 for definitions). Therefore 

 the response can be described as a burst of swim- 

 ming activity. 



Kinematics of larval fast starts and sprint 

 swimming have been described in detail for zebra 

 danio, Brachydanio rerio, (Eaton et al. 1977) and 

 for northern anchovy (Hunter 1972). No differ- 

 ences were seen in the present experiments and 

 therefore details are not repeated. 



The most direct, and hence most accurate, mea- 

 sure of performance during a burst of swimming is 

 the distance traveled in a knovm elapsed time for 

 larvae accelerating from rest. The form of this 

 relationship for the distance traveled by larvae of 

 various total lengths is shovm in Figure 2 for three 

 representative time periods. Data were described 

 by best fit linear regression equations without 

 data transformation (Table 2). Similar linear rela- 

 tionships have been shown for larval cruising per- 

 formance of plaice, Pleuronectes platessa, (Ryland 

 1963); herring, Clupea harengus, (Rosenthal 

 1968); walleye, Stizostedion vitreum uitreum, and 

 yellow perch, Perca flauescens (Houde 1969). The 

 total distance traveled per burst of swimming (S) 

 also increased linearly with total length (L) ac- 

 cording to 



S = 0.08 + 3.79±0.76L {r"" = 0.57; n = 85). 



