CHAPTER ^ 



MASTERS OF THE WATER— Bony Fishes 



CLASS OSTEIGHTHYES {"bony fish") 



We have previously mentioned that the primary aims of this book are to give 

 identification of groups (such as famihes) rather than of species and to see into 

 which niche each group falls in the economy of the sea. Perhaps nowhere is the 

 usefulness of this procedure better exemplified than in the case of bony fishes, 

 for the following reasons: 



1. Bony fishes are the dominant animals of the sea, receiving far more 

 attention than any other of the sea's inhabitants. They are tremendously 

 numerous and, in contrast to the sharks and rays, extremely diverse both 

 in form and habits. To understand this great diversity, it is best to think 

 not in terms of thousands of species, but in terms of families. 



2. By keeping groups in mind, the swimmer will not be completely lost when 

 confronted by strange, new fishes elsewhere in the world. For instance, 

 both the red tai of Japan and Europe's huge dentex become species of 

 porgies, Sparidae, rather than just a couple of unknown, isolated species. 



3. The bony fishes are much more difficult to identify than sharks and rays, 

 demanding the use of comparatively complex characters for proper 

 identification. For instance, demoiselles, Pomacentridae, are not too diffi- 

 cult to identify as a group, but species identification is complex and is still 

 a matter of dispute among ichthyologists. 



It is difficult, if not impossible, to give a list of characters that strictly define 

 bony fishes. All have skulls that are composed of a complex system of bones, 

 but this information is of little use to the underwater swimmer. However, there 

 are two field characters which vary little; the possession of an operculum which 

 covers the gills (if absent, as in some eels, there is never more than one gill 

 opening) and the presence of fins which are supported by bony rays. The fins 

 are very mobile, in contrast to those of the cartilaginous fishes. Usually, also, 

 there is a covering of bony scales which overlap like the shingles on a roof. 



The movement of fishes is a topic of great interest, to which the observations 

 of the underwater swimmer can add much. The ffight characteristics of birds 



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