29. How many species of fishes are there? 



Although fishes are the most numerous of the recent vertebrates, 

 there is little agreement among scientists on the number of species. 

 Estimates range from 15,000 to 40,000 species; however, 25,000 ap- 

 pears to be the most often quoted figure. This discrepancy exists be- 

 cause fish species are sometimes named more than once due to inade- 

 quate descriptions and variation due to environment or geographical 

 distribution. In some fish species, the male has been described as be- 

 longing to one species and the female to another because of a difference 

 in body form or color pattern. This phenomenon is called sexual dimor- 

 phism. Other fishes have been named more than once because the 

 young look different than the adults. In addition, most scientists agree 

 that not all fishes have yet been named; the estimate of 25,000 allows 

 for this unknown. The species of fishes with bony skeletons are more 

 numerous than those with skeletons of cartilage (sharks and rays). Bony 

 fish number around 20,000 while the cartilaginous fish number only 

 about 600. 



Herald, Earl S. 



Living Fishes of thie World, Doubleday and Company, 1962. 

 Lagler, Karl F., John E. Bardach, and Robert R. Miller 



Ichtfiyoiogy, John Wiley and Sons, 1962. 

 Norman, J. R. 



A History of Fisties, Hill and Wang, 1963. 



30 



