Bony Fish: What Osteichthyes Are, With Examples

Bony fish are fish whose skeleton is made mainly of bone rather than cartilage, the class Osteichthyes (Wikipedia). Almost every fish you will catch, eat or keep is one: trout, bass, carp, catfish, tuna, clownfish, bettas. The exceptions are the cartilaginous fish (sharks, rays and chimaeras) and the jawless lampreys and hagfish.

SeaWorld counts more than 28,000 species, about 96% of all fish and more living species than any other class of vertebrates. It lists the defining features as a skeleton of bone, scales, paired fins, one pair of gill openings, jaws and paired nostrils.

The quickest checks on a fish in your hand (Wikipedia; SeaWorld):

• Gill cover: bony fish have one pair of gill openings, each under a bony flap, the operculum, which lets them breathe without swimming; sharks and rays have no bony gill cover
• Skeleton: true bone rather than cartilage
• Swim bladder: most bony fish have one for buoyancy, or lungs in the lungfish
• Scales: overlapping scales with a bony base, of the cycloid, ctenoid, ganoid or cosmoid type
• Eggs: bony fish typically release many small eggs that are fertilised outside the body

Many aquarium 'sharks', such as the red fin shark, are bony fish too.

Osteichthyes, from the Greek for bone and fish, and sometimes 'bony fishes'. The two main groups have their own names (Wikipedia):

• Ray-finned fish (Actinopterygii): fins held up by thin bony rays called lepidotrichia; nearly 99% of fish species, from 8 mm gobies to the giant sunfish
• Lobe-finned fish (Sarcopterygii): fleshy fins attached by a single bone; the coelacanths and lungfish. Modern classifications place all land vertebrates, including people, inside this group, which is why scientists now often say Osteichthyes includes tetrapods.

SeaWorld uses an older three-way split: lungfishes (Dipnoi), coelacanths (Crossopterygii) and all other bony fishes (Actinopterygii).

Five that show the range, each with a page or note on this site:

• Common carp: a freshwater ray-finned fish with large scales and barbels; see common carp
• Largemouth bass: a North American freshwater game fish; see largemouth bass
• Clownfish: a reef fish; see clownfish
• Giant and ocean sunfish: the heaviest bony fish, with Mola alexandrini recorded at 2,744 kg (Wikipedia); see mola mola
• Coelacanth: a lobe-finned fish known from fossils and found alive in 1938 (SeaWorld)

At the small end, Paedocypris progenetica matures at 7.9 mm (Wikipedia, List of smallest fish).

Everywhere there is water. SeaWorld gives these figures:

• Depth and height: from about 11 km deep in the ocean to lakes about 5 km above sea level
• Salt and fresh: about 58% of species (13,000 plus) are marine and 42% (9,000 plus) live in fresh water, even though fresh water is only 0.01% of the Earth's water
• Temperature: desert pupfish survive hot springs above 45 C (113 F); Arctic cod live at -2 C (28 F)
• Oxygen: brown trout need up to 11 mg of oxygen per litre, while some loaches manage at 0.5 mg

That spread is why identifying a bony fish starts with where you found it; see freshwater versus saltwater fish.

If you mean the fish with the most small bones to deal with at the table, northern pike is the classic example. Wikipedia describes pike flesh as bony, especially because of the substantial Y-shaped epipleural bones, says removing them from fillets is a valued skill, and notes that smaller pike are often minced into forcemeat for quenelles and fish mousse to get rid of the many small bones. Scientifically, every fish in Osteichthyes counts as 'bony', so this question is about eating, not classification.