Rudd: What the Fisherman Should Know
The rudd (Scardinius erythrophthalmus) is also called red eye, azurine, blue roach (and, in Ireland, roach).
The back is green-brown, grey-brown, green-blue, or intermediate. The flanks are pale yellow in the young fish, becoming brassy as it gets older, and finally a golden metallic colour tinged with red. The belly is cream, yellow, or off-white and the dorsal and anal fins are blood-red or pink, or in some fish yellow, or yellow streaked with red. The tail is orange or pink, and streaked with brown or grey. In some waters younger fish are silvery like ROACH and their colour in maturity is less golden, and some fish, when seen in the water and when first removed from it, have a bluish appearance in the back and flank, which has no doubt given rise to the notion that they were ‘blue roach’. All so-called ‘blue roach’ have upon examination proved to be rudd.
The body in mature fish is strongly compressed laterally, the back being humped, and the abdomen full and rounded. The abdomen is also keeled between the pelvic and anal fins. The mouth is strongly oblique and the lower jaw projects boldly beyond the upper, indicating that the rudd is a surface feeder. The fore-edge of the dorsal fin is set well to the rear of the pelvic fin, and in mature fish its top edge points rearwards.
Rudd are subject to some variation, particularly in colour; an albinotic form, the golden rudd, is a favourite with aquarists.
The yellow-finned forms are found alongside the red-finned in the same waters, which suggests that differences in fin colour are due to genetic rather than to environmental causes.
The growth of rudd is probably more variable than that of any other fish species except possibly PERCH, chiefly because of their tendency to overpopulate the water. In suitable conditions, however, they grow more quickly than ROACH, reaching 5 cm (2 ins) during the first year, and 10 cm (4 ins) in the second. During their third year they are capable of breeding and may attain a length of 17 cm (7 ins) and by the time they are five they may reach the 225 g (4 lb) mark. In poor conditions a ten-year-old fish might still be undersized.
Rudd interbreed occasionally with ROACH or, and the resulting hybrids are fairly common in waters where the species are mixed.
The rudd-roach hybrid is difficult to recognize, falling as it does intermediately between two species which are already closely allied and similar in appearance. If the position of the dorsal fin suggests roach, while the strongly upturned mouth suggests rudd, the angler should suspect hybridism. Only a dissection by a specialist would satisfactorily prove the case. Since these hybrids do not often reach specimen proportions this is neither necessary nor desirable.
The rudd-hybrid is different in that it does frequently reach proportions which would be sought in a specimen rudd. It is, fortunately, easy to identify by counting the number of branched rays in the anal fin. The true rudd bears between ten and thirteen such rays, the BREAM between nineteen and twenty-three. The hybrid bears between fifteen and eighteen branched rays and can thus be positively identified as such by any angler who makes the count.
Any fish which is big enough to warrant claim as a record or specimen fish should first be subjected to this check. Immediate identification in this way will avoid much disappointment later if the fish does happen to be a hybrid. Most enlightened specimen groups, newspaper columnists, or club officials will be certain to apply this test if the fish is presented to them for prize or record claim purposes.
Rudd are generally thought of as lake and pond fish, but they also occur, though less often, in rivers, where they inhabit the slower reaches and sluggish pools. The river fish are usually as large as lake fish although the best specimens are invariably recorded from lakes and still waters. The fish do especially well in lakes, provided that food supplies are good and the water is suitably alkaline, with good weed growth. Unfortunately the species breeds profusely and in many waters there is a tendency to over-population. The fish then become stunted over a period of many years, and growth rates are extremely poor. When waters of this kind are ruthlessly netted, the fish transferred elsewhere often show a sudden improvement in growth and those which remain also improve temporarily until population gets out of hand again. Such waters can be improved with lime and fertilizer and other agents to increase food supplies for the fish. Where rudd are of good quality there are often good PIKE also, and the suggestion that pike stocking might assist in overpopulated waters deserves consideration. Possibly the introduction of PIKE-PERCH would considerably help in balancing the population, since these fish are just as predatory as pike, and rather more active.
Rudd are confirmed surface feeders and live in mid-water most of the time, although older specimens become less attached to the surface, tending to feed nearer the bottom to obtain a more varied and satisfying diet. The shoals consist of fish of all sizes, the older and larger fish often lying in the centre of the shoal, or deeper in the water. They are fond of the shallows, especially among thick bottom weed which extends upwards to the surface, and often shoal among reeds, their thin-sectioned bodies being well suited to swimming between the stems.
Rudd patrol the lake during the day, working from the margins to the deeps or vice versa, according to the prevailing winds and the water temperatures. They seem to prefer the sheltered part of the lake or pond where wind neither ruffles the surface nor lowers the temperature. They spawn in the weeds between May and June, and are often found still unspawned in mid-June, when the slightest touch of the hands on the flanks is sufficient to cause spawn to be shed. Towards autumn they feed less often, particularly in exposed waters. By December they become quite comatose and cease to feed except on exceptionally warm, sunny days, when they may feed for a brief spell at about midday. This semi-hibernation lasts until February or March according to the severity of the season.
Rudd are widely scattered in all parts of England, being chiefly confined to still waters, but are found notably in the Great Ouse, Nene, Fenland waters, and the waters of eastern England, becoming less common towards the west and rare in the extreme north and in Scotland. The species is common in Ireland, where it is known as ‘roach’.