CHARACTERISTICS OF MARINE FISHES 163 



plate. Perhaps the oddest place for teeth, exclusive of the denticles in the skin 

 of sharks (discussed in the section dealing with body coverings, page 152) is in 

 the anterior part of the oesophagus. Well-developed hooked and sometimes 

 barbed teeth occur in this position in butterfish, Stromateidae, represented on the 

 Atlantic Coast of the United States by 2 common food fishes, the butterfish, 

 Poronotus triacanthus, and harvest fish, Peprihts alepidotus. 



Teeth in fishes have 3 major functions: namely, grasping and holding the prey; 

 cutting and rasping; and crushing. A good example of teeth adapted for grasping 

 and holding occurs in the salt-water gars (Belonidae) which feed chiefly on small 

 fish. Their rather long sharp teeth, already described, are suited for grasping 

 and holding the prey while manipulating it into position for swallowing. The 

 barracuda, Sphyraena barracuda, bluefish, Pomatomus saltatrix, and cutlassfish, 

 Trichiurus lepturus, have teeth suitable for both holding and cutting. Teeth 

 adapted primarily for cutting are possessed by parrot fish and many sharks, and 

 those for rasping are found in the spadefish. Finally, the pavement-like teeth of 

 the black drum, as well as those of many skates, are used for crushing. 



It is evident from the descriptions of the size, position, and shape of the mouth, 

 together with the discussion concerning the different types of teeth, that these 

 characteristics constitute a clue as to where the fish seek their food, what kind 

 they require, and how they acquire it. Although fish with vertical mouths, like the 

 stargazers, obviously would not feed on the bottom, those with inferior mouths, 

 like the sturgeons and skates and rays, would do so. Those with terminal mouths, 

 including the vast majority of fishes, probably feed at any depth. It is impossible, 

 however, to lay down any hard and fast rules in these respects, because some 

 species with inferior mouths, as, for example, the vast majority of sharks, feed at 

 the surface as well as at almost any depth. Furthermore, contrary to the more 

 or less general public opinion they do not have to turn on their backs to grasp 

 their prey. 



Teeth of the cutting type, possessed by many sharks, barracudas, bluefish, etc., 

 break the prey into a size suitable for swallowing. Cardiform teeth, such as those 

 of the spadefish and its relatives, rasp small plants, principally algae, from their 

 anchorage. Broad flat teeth, with which many skates and rays, drumfish, and 

 other species are equipped, crush mollusks and other hard-shelled animals. In 

 many species the teeth seem to serve no other purpose than that of grasping the 

 prey and holding it while it is worked into the proper position for swallowing, 

 as stated in a preceding paragraph. Finally, it may be assumed that those fishes 

 with minute teeth, or none at all, feed on small organisms which are usually 

 screened from the water with numerous close-set gill rakers. 



The Eye. The size and position of the eyes are quite as variable as some of the 

 characteristics already discussed. It is possible to state definitely, however, that 

 the eyes are never inferior in position (i.e., directed away from the light); they 

 are either lateral or superior. In herrings, as in the vast majority of fishes, they are 

 lateral; but in some species, as in the stargazers (Fig. 10-20), they are definitely 

 superior (i.e., set in the top of the head). The remarkable change in the position 

 of the eyes of flounders has already been related (p. 152). These fishes, which 

 lie either on their left or right side, have the eyes on the upper side of 

 the head. In other words their eyes, like those of the stargazers, look straight up. 



In size the eyes vary from a mere dot, as in stargazers, to an inch or more in 



