FISH

Each time a bridge crosses a backwater, crowds of fish can be seen, large fat carp cruising slowly in and out of the reeds and smaller red-finned perch or rudd. Tench, a carp-like species, is another typical inhabitant of the backwaters.

Some basic biology – short and simple!

Fish are vertebrates (with a skeleton similar to our own based on a vertebral column/spine, skull at one end, tail at the other, many ribs but no limbs. Extra bony extensions support the fins (fin rays). Some fish have a skeleton of bone (carp, perch, pike) and others of cartilage (sharks, catfish etc). they are cold blooded, that is, their body temperature varies with that of the environment.

The skin of fish is covered with scales which can be of various types and composition. The whole body is protected with a slippery layer of mucus (slime).

Fertisization of eggs is internal in some species ( sperm placed by the male within the body of the female using a special organ/appendage). The eggs are then released into the water, although in a few species they are retained in the female body until hatching when the larval forms are released. In other types of fish, fertilization takes place in the water after laying (external fertisization). Eggs are often sticky, adhering to weeds or even the feet of wading birds who may unwittingly carry the eggs to other waters.

In the majority of cases the hatchlings are small larval stages that have to develop and change (metamorphosis) into the final adult form. The juveniles have to fend for themselves and the survival rate is low, hence the need to produce very large numbers of offspring.