Rudd (Scardinius erythrophthalmus)
Species: S. erythrophthalmus
Binomial name: Scardinius erythrophthalmus
Common names: Rudd, Common rudd, often referred to as 'possums of the waterways'
Scardinius erythrophthalmus is a benthopelagic freshwater fish native to Europe, Russia and central Asia. It is a very invasive species and was illegally introduced into New Zealand in the 1967s via a private consignment of juvenile rudd which was then reared to adulthood and encouraged to breed. Since then they have been illegally spread deliberately and strategically into a number of lakes, ponds and rivers throughout the North Island as well as Canterbury and Nelson. They are widespread in Auckland and Waikato with isolated populations in Northland, Whanganui, Wellington, Nelson and Christchurch.
They are a voracious fish that compete with New Zealand's native fish and cause irreversibly damage indigenous ecosystems. Adult rudds are predominantly herbivorous and feed preferentially on native macrophytes (aquatic plants), while juvenile rudd feeds voraciously on zooplankton (tiny aquatic animals). These feeding habits endanger native plant species, destroy indigenous habitat, remove food sources for native fish and invertebrate species, and potentially impact negatively on water quality by stirring up bottom sediments and muddying the water.
They are a stocky, deep-bodied fish with distinctive red fins and large, shiny scales that range from silver (juveniles) to pale orange (adults) in colour. Rudd normally grows to about 25 cm, and about 500 g. They are highly productive, with females able to produce up to 50,000 eggs per kilogram of body weight.
Legally they are classed as a noxious species (except in Auckland/Waikato Fish and Game region where it is a sports fish).
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