Class Osteichthyes

Introduction to the Bony Fishes

The bony fishes are the ones people usually think of as fish.  They are typically the ones kept in home and public aquaria, and are certainly the most commonly seen fish when tidepooling and diving. Their common features include:

Source:  Van Ramshorst, 1978

External Anatomy

Identification Help

Identifying fish is made far easier by noting a few important features.  First, look at mouth structure.  The shape and position of a fish’s mouth indicates its feeding preferences and, to a degree, trophic level.

-     Downturned mouth indicates a bottom feeder

-     Forward-facing mouth indicates a mid-level feeder

-     Upturned mouth indicates a surface feeder

Next, look at fins. 

-     Look for single or double dorsal

-     Look for adipose fin

-     Look for modified fins, such as the modified pelvic fins of the   snailfish

-     Count the hard dorsal rays in difficult species

Also note whether the fish is scaleless or has bony plating rather than typical scales.

This webpage is part of the UWT Marine Ecology 2007 Class Project

-     True bony skeleton

-     Fixed teeth that are fused with the jaw⁶

-     Swim bladder regulates bouyancy⁶

-     A few can breathe atmospheric air

Some fish have split dorsal fins, as in the rockfish above. 

In this case, the first dorsal is generally composed of hard rays and the second is composed of soft dorsal rays.  Be wary of the hard dorsal: often, the spines are quite sharp, and are actually mildly venomous in a few species.