Exotic Fish

Exotic Fish

Eight species of introduced (or exotic) fish have been recorded in Wairarapa Moana or the wider Ruamahanga River catchment:

  • Brown trout (Salmo trutta)
  • Rainbow trout (Onchorhynchus mykiss)
  • Rudd (Scardinius erythrophthalmus)
  • Perch (Perca fluviatilis)
  • Goldfish (Carassius auratus)
  • Tench (Tinca tinca)
  • Gambuisa (Gambusia affinis)
  • Grass carp (Ctenopharyngodon idella)


A couple of these species have very restricted ranges (e.g., grass carp) or known populations have been eradicated (gambusia). However, others are now very abundant and are among the most commonly encountered fish in Wairarapa Moana (e.g. brown trout, perch, goldfish and rudd). 

Some of these species were introduced over one hundred years ago for their ‘sports fishing qualities’ (e.g. brown trout and perch), whereas others were introduced for ornamental reasons (e.g., goldfish) or perceived biological control (gambusia and grass carp).

Trout Perch with bullies Large goldfish

The issue with exotic fish

The effects of the more commonly encountered exotic fish on the native fish that occur in Wairarapa Moana have not been specifically investigated and documented. However, some, like perch and trout, grow considerably larger than most native fish species. They are aggressive and in some cases feed almost exclusively on native fish.

These species have also been implicated in the decline, or even local extinction, of some native species in other lakes and rivers in New Zealand. Even when not directly preying on native fish, they are competing for the same food and habitat resources that other native fish depend on.

So it is likely that these species are having a negative impact on the native fish fauna of Wairarapa Moana. Even largely herbivorous species, such as Rudd, can affect native ecosystems by interrupting food chains. 

Content on this page was last updated: 15/02/2017 11:47am