European Minnow

Appearance

The common minnow is a small fish which reaches a maximum total length of 14 cm, but is normally around 7 cm in length. It has 3 spines and 6-8 soft rays in its dorsal fin with 3 spines and 6-8 soft rays in its anal fin. Its spine is made up of 38-40 vertebrae. It is distinguished from similar species which occur in Europe by having the lateral line normally extending beyond the nase of the anal fin, by a line of vertically elongated blotches along the lateral line each with a depth equivalent to 1/3-1/2 of the body's depth at same position, these blotches often fuse to form a midlateral stripe, caudal peduncle has a depth of 2.6-3.1 times its length. The scales on the breast are patchy and the patches of scales are separated by unscaled areas although they are rarely connected by 1-2 rows of scales. Its snout length is 29-34% of the head length and is 1.1-1.4 times the diameter of the eye. The anal fin has its origin in front of the base of the last dorsal ray. The caudal fin consists of 19 soft rays. The back is normally brownish-green, and is separated from the whitish-gray underside by the lateral stripe or blotches described above,

Distribution

The common minnow is found in northern Eurasia from Ireland in the west east to the Amur drainage and Korea. In Great Britain occurs to 58°N and in Scandinavia and Russia occur up to the northernmost extremities. In western Europe the southern limit appears to be the Garonne and the upper Rhone. It has been recorded in the drainages of the Volga and the Ural, as well as in Lake Balkhash and the upper Syr-Darya drainage. Records else where require confirmation as this species is similar to a number of others. In Scotland it is regarded as an introduced non native species, and this is probably the case in Ireland. Introductions are likely to have occurred elsewhere, including Norway.

Reproduction

The Eurasian minnow breeds well in cold fresh water aquariums, but it is rarely sold as an aquarium fish. They need a good supply of oxygen, a reasonable current, and a gravel bottom. It is not clear what size works best although smallish works well. Clean water helps and so do plant life and general good quality aquarium conditions. Breeding begins around late May when the fish become noticeably more active, and the fish begin to change colour. The females don't change their colour so much, more the shape of their body; in fact the colours seem to fade if anything except for the fins which become slightly more red. Their body becomes more deep set toward the abdomen, which area also starts bulking out. Although the changes in the female are small, the changes in the male are huge. First of all, the difference in the shades of colour on the fish become stronger, and the fins, throat and some other areas redden. These colour changes strengthen as the fish gets closer to breeding. The body becomes much bulkier, and the gills become very pale with iridescent light blue patches towards the bottom and below. This contrasts with the now very dark body. Later the scales on the lower half of the body begin to stand out more and become slightly gold-lined. All these strengthen as time passes on. All the fins, especially the dorsal, start to stick out more; this happens in both sexes. The males begin to chase females around, rubbing their sides against them, and this becomes very frenzied and aggressive towards the mating. Mating happens when this behaviour reaches its climax where the female releases the eggs and the male fertilizes them.

Fertilised eggs promptly sink to the bottom and into the gravel. The other fish will start eating the eggs and picking at the gravel to find them. The male will then ferociously guard them for a period of time. A few days later the eggs will hatch and the fry will emerge. It is very important to have much plant cover for the fry to hide in as the adult fish will try to eat them especially if underfed and if not much other live food is given. The baby fry feed on small organisms called infusoria and algae. To grow infusoria for feeding just get a jam jar of pond water and run it through some cotton wool or muslin to get out any larger predatory organisms like daphnia which will eat the infusoria and add hay to the water. Leave it for a few days in a dimly lit room at about room temp. and when you next look you should see lots of tiny white dots in the water which, if looked at under a microscope reveal to be lots of types of infusoria in their millions. these can be fed to the fry by adding them to the tank. To get more just add some of the old water containing the infusoria to cooled, boiled tap water with hay and repeat the other procedures. As the fry grow their diet changes. When they reach about half an inch they can be fed small organisms like daphnia or cyclops. These can be obtained by dragging a net through water where they can be seen or they can be purchased from aquarium dealers. Soon the fish will eat the same food as the adults and will quickly grow.