an introduction to freshwater fish
Ref: B09d

Fish are aquatic creatures, they live underwater. They breathe by using gills which do the same job as our lungs. They swim and move about using their strong body muscles and fins. The bodies of most fish are covered with scales and these vary in their shape, size and colour.

Click on the icon below, to start a movie of trout swimming

Different species of fish eat different foods but the fish of British streams are mostly predators - they hunt and eat other fish or living creatures such as insects (B09a). Their mouths are hard and they have teeth so that they can eat sharp crunchy objects like crayfish, which have hard shells. A few will graze on vegetable matter and some are cannibalistic and eat their own kind.

At breeding time, when they spawn the female will lay a cluster of eggs in her chosen nest site, either in gravel, sand, on rocks or in weeds and leaves in the water. The male will then fertilise the eggs. When germinated the eggs will hatch out and develop into fry (baby fish) which can swim and find their own food. (see Salmonid Life Cycle F02).

Piscavors (Perch)

A wide variety of native freshwater fish can be found in the rivers of the Westcountry. See the section Types of Fish (F03). Because he rivers of Devon and Cornwall are fast flowing, the most well known and widespread are the salmon, trout, sea trout and grayling (the Salmonid family) (G1). They are known as Game fish. Other wild fish are called Coarse fish and some of the most common ones are the Pike, Roach, Perch, Minnow and Chub.

Fish in river

For a river to have a healthy population of fish and for the eggs to survive and hatch it is vital that the water in the river, stream or pond is clean and that the gravel and sand is not clogged up with soil or sediment (G1). Clean water will also ensure that there is a wide variety of wildlife and plenty of food for the fish to eat.

See if you can identify the different parts of a fish in the Fish Exercise (F09)