OLLA, SAMET, and STUDHOLME: SUMMER FLOUNDER 



winter flounder, Pseudopleuronectes american- 

 us, (McCracken, 1963) and starry flounder, 

 Platichthys stellaUis, (Orcutt, 1950), burying 

 could be induced as a direct response to a sudden 

 disturbance, such as a change in light intensity 

 or moving object. In the summer flounder, ap- 

 parently the primary response to a fright stim- 

 ulus is to assume a stationary and sometimes 

 rigid posture on the bottom. This is followed 

 by burying as essentially a secondary response. 



There are numerous descriptions of the sen- 

 sory mechanisms utilized by diff"erent groups of 

 flatfishes during feeding (see de Groot, 1971, for 

 review). Since summer flounder are primarily 

 day-active, it was not surprising that vision 

 played a primary role in prey selection and cap- 

 ture. According to de Groot (1971), this is ap- 

 parently characteristic of Bothidae including 

 brill (Scophthalmiis rhombiis) and turbot, which 

 he designated as visual day-feeders, largely de- 

 pendent on visual stimuli for locating prey. De- 

 spite the fact that the summer flounder would 

 also be categorized in this manner, we did ob- 

 serve feeding at night. Although the light level 

 of 2.5 X 10~^ mc (as measured at 1 m below the 

 surface) fell slightly below the lO^-lO"- mc level 

 cited by Blaxter (1970) as the range in which 

 most visual feeders cease active feeding, it was 

 possible that vision was still being utilized. 



The summer flounder, winter flounder, (011a, 

 Wicklund, and Wilk, 1969), and lemon sole, 

 Microstomus kitt, (Steven, 1930) may rest on 

 the bottom with head up while actively moving 

 their eyes. In the latter two species, the fish 

 may be searching for food and will lunge for- 

 ward from this position to strike at and capture 

 prey. While we considered summer flounder in 

 this position to be alert and responsive, it was 

 also apparent that this was not necessarily in- 

 dicative of a prefeeding strike. Although Gins- 

 berg (1952) stated that summer flounder lie in 

 wait for passing prey, we found that the fish, 

 even in this alert "head-up" posture, never 

 lunged from a resting position at a prey, even 

 though it was only a few centimeters away, but 

 always preceded prey capture by active search- 



ing. 



While we do not understand the role yawning 

 plays in the behavior of the summer flounder, we 



did find evidence that it was associated with 

 changes in activity. Rasa (1971) found that 

 yawning in the yellowtail demoiselle was asso-* 

 ciated with an increased excitement level. She 

 postulated that the strong muscle contraction 

 that occurs during yawning could serve to in- 

 crease the blood flow and oxygen to the body 

 musculature and thereby facilitate the onset of 

 the animal's activity. It may also be conceiv- 

 able that yawning movements may act to flush 

 sand or debris from the gill areas, one function 

 suggested for yawning in Pacific bonito, Sarda 

 chllieiisis, (Magnuson and Prescott, 1966). 



ACKNOWLEDGMENTS 



We wish to express our grateful appreciation 

 to A. J. Mansueti for her illustrations and A. D. 

 Martin for his help throughout all phases of the 

 study. 



LITERATURE CITED 



BiGELOW, H. B., AND W. C. SCHROEDER. 



1953. Fishes of the Gulf of Maine. U.S. Fish Wildl. 

 Serv., Fish. Bull. 53:1-577. 

 Blaxter, J. H. S. 



1970. Light: Fishes, hi O. Kinne (editor), Ma- 

 rine ecology: A comprehensive, integrated trea- 

 tise on life in oceans and coastal waters. Vol. I, 

 Part 1, p. 213-285. Wiley-Interscience, Lond. 



Ginsberg, I. 



1952. Flounders of the genus Paralichthys and re- 

 lated genera in American waters. U.S. Fish 

 Wildl. Serv., Fish. Bull. 52:267-351. 

 Groot, S. J. de 



1964. Diurnal activity and feeding habits of plaice. 

 Cons. Perm. Int. Explor. Mer, Rapp. P.-V. Reun. 

 155:48-51. 

 1969. Digestive system and sensorial factors in 

 relation to the feeding behaviour of flatfish 

 (Pleuronectiformes). J. Cons. 32:385-394. 



1971. On the interrelationships between morphol- 

 ogy of the alimentary tract, food and feeding be- 

 haviour in flatfishes ( Pisces : Pleuronectiformes) . 

 Neth. J. Sea Res. 5:121-196. 



Kruuk, H. 



1963. Diurnal periodicity in the activity of the com- 

 mon sole, Solea vulgaris Quensel. Neth. J. Sea 

 Res. 2:1-28. 

 Magnuson, J. J., and J. H. Prescott. 



1966. Courtship, locomotion, feeding, and miscel- 

 laneous behaviour of Pacific bonito (Sarda ckil- 

 iejisis). Anim. Behav. 14:54-67. 



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