There is something very satisfying about the appearance of the deep-bodied tench. It is a member of the carp family and can vary in colour from almost black through green to pale yellow. The most usual colouring is a deep olive green back and flanks, with a paler belly. There is also an ornamental golden variety which sometimes has black patches on its back and sides.
Follow the feeding
Tench feed almost exclusively on the bottom – finding their food by rooting around in the mud. As they do this they often release strings of fine bubbles. These come from pockets of marsh gas (mainly methane) disturbed by the fish as they feed in the mud. The gas filters through the tench’s mouth and gills, and the fine gill rakers produce characteristic pinhead bubbles.
Tench eat all the small prey animals found on the bottom but are especially fond of bloodworms, jokers and other insect lar- vae. They also eat larger items such as worms, snails, mussels and even some small fish. They feed mainly at dawn and dusk, but sometimes continue through the night. In winter they hardly feed at all, lying inactive on the mud for long periods.
Increasing numbers of large tench are being caught in Britain and this may in part be due to the quantity of high protein baits (boilies) thrown into waters every year. Tench, like carp, eat them readily and may put on weight as a result.
Lazy stillwater fish
Though some tench are found in quite fast-flowing rivers such as the Trent, they thrive best in rich still waters, sluggish rivers and canals. You won’t find them in very fast water or poor upland lakes, but they are highly tolerant of low levels of dissolved oxygen, and so do well in shallow ponds which have low water levels, or even become stagnant, in summer.
Tench won’t spawn unless the water has remained at 18°C (64°F) or above for at least two weeks. They therefore spawn later than most other British coarse fish -between May and August. Each pair takes several weeks to spawn, leaving many clusters of pale green eggs stuck to the stems of water plants. Large females carry as many as 750,000 eggs.
The eggs hatch out in four or five days but the larvae remain stuck to the plants by their heads until the yolk sac attached to their bellies is used up. Then the fry must forage for food. The young fish live in the weeds and are very rarely seen or caught, though obviously large numbers of them die in the first year, probably during the winter.
Growth is very slow at first – they only reach 20-30cm (8-12in) after three years, and spawn for the first time after at least four. In ideal conditions, they reach about 5-6 lb (2.3-2.7kg) after ten years and can live up to twice that age.