What does it look like?
In Europe, wild orfe are usually greyish brown with silver bellies. However, the variety of orfe present in New Zealand (the golden orfe) is derived from ornamental pond stocks and thus closely resembles rudd. Although it is not known if the two species co-exist, on orfe the scales are smaller and the fins more orange than red coloured. Rudd also have a small projection at the base of their pelvic and pectoral fins. Eventually, the orfe’s golden colouration may revert to the wild type.
Little is known about the biology of orfe in New Zealand. In Europe they primarily inhabit slow-flowing waters. Their food consists of aquatic invertebrates such as worms and snails, but large orfe may consume other fish and aquatic vegetation. Like the other Cyprinidae, orfe are prolific breeders and large females may contain tens of thousands of eggs. Whether they become a nuisance species in New Zealand or will be successfully eradicated remains to be seen.
Why is it a problem?
Orfe are omnivorous, opportunistic feeders that are able to feed within all levels of the water column. However, as they grow older, adults will switch to a mainly vegetative diet.
Spawning occurs in spring at depths of 0.5-1.5m and eggs are laid over gravel beds, weeds and muddy substrate, where they will adhere to most surfaces. Optimum water temperature is around 8-10°. egg development is temperature dependent and take up to 23 days at lower temperatures.