WEBB: EFFECT OF BOTTOM ON FAST START OF A FLATFISH 



160 120 



10 cm 



B 



Figure l. — Ti-acings of the body center-line 1 seen from the side) at 20 ms intervals to show the acceleration 

 movementsduringfaststartsofC;7/iaWc/!^/!.vss^/^maeus: A) Acceleration from contact with thegrid. B) 

 Acceleration in the water column. Dots show the location of the center of mass of the stretched-straight 

 body. The extended and variable stage 3 following the major acceleration strokes has been omitted for 

 clarity. 



The center of mass was propelled vertically away 

 from the ground. 



Fast start stage 3, occurring after the major 

 acceleration period, was variable, ranging from an 

 unpowered glide to continued swimming with 

 caudal propagation of propulsive waves sustained 

 from the starting curvature in stage 2. 



A typical fast start of a sanddab in the water 

 column away from the bottom is illustrated in 

 Figure IB. Fast starts in the water column showed 

 the same stages as fast starts from the grid. The 

 amplitude of body movements was usually smaller 

 than those of fish accelerating from the grid. 

 Center of mass recoil, reduced during acceleration 

 from the grid, was observed for fish accelerating in 

 the water column, as seen in other teleosts. 



The timing of various fast-start events was simi- 

 lar among groups offish (Table 1). The duration of 

 stage 1 showed a slight but nonsignificant tend- 

 ency to decrease as the distance between the grid 

 and the solid bottom increased. The fish accelerat- 

 ing from the grid lost contact after 112 ms, before 

 the completion of stage 2 in 124 ms (Table 1). 



Fast-Start Performance 



The distance between the solid bottom and the 

 grid had no significant effect on vertical and hori- 

 zontal distances traveled by the center of mass of 

 speckled sanddabs during fast starts (Figure 2) 

 including distances traveled after losing contact 

 with the grid. This showed that no measurable 



Table l. — Results for the duration of fast-start events for Citharichthys stigmaeus accelerating from a grid at various 

 distances above a solid bottom and accelerating in the water column. Mean ±2 SE are shown, n = 10. 



273 



