8 Big Game Fishes 



medium ; hence the fishes are said to be cold- 

 blooded. But in the tuna, bonito, and others the 

 movements are so energetic that the temperature 

 is higher than that of the water. When a fish 

 is taken out of the water, it gasps and opens its 

 gills, and doubtless is killed in part by too much 

 oxygen, the reverse of the drowning process. 



The digestive organs of fishes are simple. The 

 prey is not chewed, the teeth being intended to 

 hold the victim, which is swallowed entire at one 

 or two gulps, though the tuna often crushes its 

 prey. Food is quickly digested, and the capacity 

 of some fishes, as the tuna, bluefish, and others, is 

 remarkable. The mouth and teeth are modified 

 or adapted to the requirements of the fishes. 

 Those which live on oysters, as the sheepshead, 

 have crushing organs. The shark, not a true fish, 

 cuts its food or tears it. The fish is enabled to 

 hold its position at various levels without effort 

 by the aid of its air or swimming bladder (vn\ 

 possessed by most individuals. This is a silvery 

 air sac or balloon lying directly beneath the verte- 

 bra, longer or shorter according to species, absent 

 in some. It contains gas, principally nitrogen, 

 and by it the fish is enabled to retain a certain 

 specific gravity. 



