A
fish is a water-dwelling vertebrate with gills. Most are cold-blooded. There are
over 29,000 species of fish on Earth, making them the most diverse group of vertebrates.
Taxonomically,
fish are a paraphyletic group whose exact relationships are much debated; a common
division is into the jawless fish (class Agnatha, 75 species including lampreys
and hagfish), the cartilaginous fish (class Chondrichthyes, 800 species including
sharks and rays), with the remainder classed as bony fish (class Osteichthyes). Fishes
from a number of different groups have evolved the capacity to live out of the
water for extended periods of time. The Butterfish
and the Common
Eel are examples from the British Isles. Fishes
are found in many habitats throughout our area. These include the seashore, seabed
and open Irish Sea; and canals, streams, rivers, ponds, lakes, reservoirs and
gravel pits. The fishes are equally diverse, ranging in size from the 10m long
marine Basking
Shark to the 0.06m long freshwater Minnow. Modified
from the article in Wikpedia http://en.wikipedia.org/wiki/Fishes
and the entry by Darren Bedworth in "Wildlife
of Lancashire". | 
