|
|
|
Species
Broadly stated, a fish is a cold-blooded vertebrate (an animal
with a backbone) which lives in water, and usually possesses paired
fins, gills, and scales.
Most of the fishes in this taxon that are familiar to us belong
to the class Osteichthyes, Bony Fishes. They are characterized
from other fishes by having a skeleton that is reinforced by a
hard matrix of calcium phosphate.
How Does a Fish Breathe?
Most fish breathe by drawing water over four or five pairs of
gills that are located in chambers covered by a protective flap,
the operculum. This enables the fish to breath while stationary;
sharks lack operculi and must move to pass water over the gills.
Some fish breathe air while a few may even absorb air through
their skin if they lack scales.
Reproduction
Details in reproduction of bony fishes vary extensively. Most
species are oviparous, reproducing by external fertilization after
the female sheds large numbers of small eggs. However, internal
fertilization and live birth characterize other species. Some
bony fishes display complex mating rituals.
Skin
The skin of bony fishes is often covered by flattened bony scales
that differ in structure from the toothlike scales of sharks.
Glands in the skin of a bony fish secrete a mucus that gives the
animal its characteristic sliminess, an adaptation that reduces
drag during swimming and acts as a barrier to infections.
The Swim Bladder
Another adaptation of most bony fishes not found in sharks is
the swim bladder, an air sac that helps control the buoyancy of
the fish. Bony fishes are generally maneuverable swimmers, their
flexible fins better for steering and propulsion than the stiffer
fins of sharks.
Endangered Species
Several distinct classes of bony fish evolved by the end of the
Devonian period: the ray-finned fishes and the fleshy-finned
fishes. Nearly all the families of fishes familiar to us are ray-fins.
One species of particular concern in the Thompson-Okanagan region
belongs to the Minnows, Family CYPRINIDAE. This family is composed
of a great number of fishes, usually of small size. They have
no adipose fin or teeth in the mouth. Instead, they have well-developed
"pharyngeal" teeth in the throat.
The Umatilla Dace (Rhinichthys umatilla), of the family CYPRINIDAE, is one example of a species found in only a few rivers and lakes of the Thompson-Okanagan region of southern British Columbia.
this section sponsored by: |
|
Located at: 
|
All rights reserved
|
Industry
Canada
