Native Members of the Family Percidae

The family Percidae is restricted to the Northern Hemisphere and has 12 of its 200+ members resident in Europe. Europeans species belong to the genera Perca, Gymnocephalus, Sander (Stizostedion) and the less well known Percarina, Romanichthys and Zingel (Aspro).
Britain has two native species: the Perch, Perca fluvatilis and the Ruffe or Pope, Gymnocephalus cernua. A third resident species the Pikeperch, Sander (Stizostedion) lucioperca was introduced as a sports fish into the Norfolk Broads, spreading with disastrous results oto the native species living there.
True perches are distinguishable by their two-part dorsal fins; these can either be separated on joined. The leading part of the dorsal fin has stiff, sometimes very spiky, rays and the rear part consists of softer rays which moves from side-to-side gracefully.
The Perch Perca fluvatilus
It is the European Perch, the most widespread and common, which gives this family its name. This fish seems to have found its way into every river, stream and lake in Europe. Larger Perch, they can reach 51cms and weight 4.75kg, are mainly ambush predators of smaller fish, but they will eat any live and dead food that passes their way. Perch come in two body forms: a high backed variety from still waters, and a more slender type from fast flowing streams. In ponds and slow rivers, the weeds grow high and straight which means high-backed fish blend in better to ambush their prey without a chase. On the other hand, weeds in fast flowing river tend to lie flat and provide less cover. The more slender fish have an advantage in these conditions for two reasons: firstly, their lower profile is easier to hide in the flattened weeds, and secondly, the more streamlined body shape is better suited to a longer chase. The dorsal fin has a well-defined, but joined, separation between the two parts. The first dorsal is highly arches and very stiff, whereas the second is soft, narrow and squared-off. The coloration of a Perch could rival many tropical species: its basic colour is light green with seven dark-green vertical bands, both pelvic and anal fins are a bright red, as is the lower portion of the dorsal. The rear of the first dorsal has a distinct black spot as an added bonus. Most of the perch encountered are in the region of 25-100mm long and a good size specimen can reach more than 300mm.
Perch make good aquarium specimens. They require cool, well-oxygenated, clean and clear water to show off their best colours, but they will survive in most conditions because of their adaptation to live in any environment in the wild. Larger tanks make the best home for these fish. Smaller fish do better in shoals, whereas fish over 100mm tend to be less active and prefer their own company. Decorating their tank provides few problems; their main requirement being vertical structures in which to hide. Using bamboo canes, plants and bogwood can provide this. A fine layer of sand is all that is needed for a substrate, and an internal power filter can provide movement, aeration and filtration. Young fish, up to 50-60mm, feed on any type of small live-food such as daphnia and bloodworm and are easily weaned onto dry and frozen foods. Larger fish will eat small fish, large earthworms, mealworms and freshwater shrimps but it is difficult to train larger fish onto other foods. Breeding the Perch requires a pond or an unheated fishhouse. As with most coldwater fishes, the Perch requires the stimulus of a cold winter and rising spring temperatures to induce spawning. Eggs are laid in ribbons similar to Toad spawn onto plants. These ribbons wrap around the stems of the plants and are anchored securely until the fry start hatching about 15 days later. It takes three years for the fish to reach maturity. It is the sticky, ribbon like structure of the eggs that is responsible for the spread of this fish to most bodies of permanent water; the eggs are transferred to other environments when they becomes entangles around the legs of wading birds.
The Ruffe or Pope, Gymnocephalus cernua.
The Ruffe or Pope is found throughout Europe and into the former Soviet Union. It is similar in shape to the Perch, but lacks its colour and size. They are coloured a unifoem muddy brown with a whitening of the belly. It is easy to distinguish them from the Perch because their two dorsals are joined. The maximum size expected in British waters is a around 170 mm, and the British rod-caught record is a tiddler of 113 g. Ruffes prefer to live in deeper waters where the light is subdued, only moving to shallower water to breed. Despite their size, they are fierce predators feeing mainly on small crustaceans and worms until they are big enough to add small fish to their diet.
In the wild they breed in the spring months, sometime a female will manage two spawnings of up to 100,00 eggs. Like the Perch, they reach maturity after 2-3 years but by this time only a handful will have survived.
They can make good aquarium residents because of their ability to withstand far higher temperatures that the Perch. When kept at higher temperatures they become even more prolific, not needing the same changes in temperature as the Perch to trigger spawning.