FISHERY BULLETIN: VOL. 79, NO. 2 



solid substrate will always convert more muscle 

 energy into body motion than working against a 

 fluid. It therefore appears that speckled sanddab 

 utilizes fast-start behavior that makes the 

 greatest use of the available ground interaction 

 options. 



However, the interaction with the ground can- 

 not be assumed to be adaptive before considering 

 the question of advantages and disadvantages. For 

 example, the small initial displacement of the 

 center of mass offish accelerating from the ground 

 might be disadvantageous in some circumstances, 

 such as escaping from predators. However, sig- 

 nificant protection is achieved by camouflage and 

 cryptic behavior in pleuronectiform fishes, render- 

 ing this contingency unlikely. 



The influence of the bottom is clearly advan- 

 tageous in the capture of elusive prey, a second 

 behavior in which fast starts play a key role 

 (Eaton and Bombardieri 1978; Webb and Skadsen 

 1980). Elusive prey, e.g., fish and Crustacea, are 

 common dietary items for pleuronectiform fishes 

 in the families Psettodidae, Bothidae, and 

 Pleuronectidae (Liem and Scott 1966; Norman 

 1966). The bottom eliminates recoil so that the fish 

 can rapidly accelerate the head vertically (Figure 

 1). Continued rapid vertical acceleration is facili- 

 tated by prolonged bottom contact through the 

 major acceleration period of a fast start. Bottom 

 contact also results in the acquisition of a superior 

 final speed that would be advantageous in a con- 

 tinued attack. The time taken to accelerate from 

 the bottom and reach maximum speed could also 

 be reduced by resting in sand in a curved U-shaped 

 posture. This may occur since flatfish often dig into 

 sand with the eyes and tail at the surface, but the 

 body buried, implying a curved posture (Hobson 

 1979). Thus, the morphology and behavior of the 

 benthic sanddab appear to be adaptive in improv- 

 ing fast-start performance, as well as for camou- 

 flage. Such advantages undoubtedly apply equally 

 to other members of the pleuronectiformes and 

 therefore provide an additional functional expla- 

 nation of the unique flatfish body form and habits. 



ACKNOWLEDGMENTS 



This work was completed during the tenure of 

 an NRC/NOAA Research Associateship. Fish 



were provided by the Naval Ocean Systems 

 Center, San Diego. I thank J. R. Hunter and R. 

 Lasker for their excellent comments on the man- 

 uscript. 



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