New Zealand Freshwater Fish

11004-10108 Perch (Perca fluviatilis) were introduced to New Zealand in the late 1860s and early 1870s from Europe and are now widespread. Perch are easy to catch, making them popular with coarse fishermen. Since the 1970s, new populations have been established illegally in many lakes and ponds to create coarse fishing opportunities. However these voracious predators reduce the abundance of our native bullies, smelt and galaxiids in lakes and streams. They also reduce crayfish numbers and are assocated with the development of cyanobacterial blooms in lakes. Lake Waihola *

DSC_3986 Koi carp (Cyprinus carpio) offered for sale in a city fish market. Koi are an ornamental strain of the common carp native to Asia and Europe. One of the most invasive fish species worldwide, koi make water turbid and change the habitat for native fish. For a period of time each year, coinciding with Polynesian and Chinese festivals, they are now offered for sale as a food fish in Auckland, where demand is slowly increasing. Auckland *

DSC_2195 Hybrid tiger trout ((Salmo trutta X Salvelinus fontinalis) detail of the pattern on a mature hatchery bred fish. Tigers are an infertile cross between a male brown trout and a female brook char. They are bred at the Ngongotaha hatchery, Rotorua, and released into Lake Rotoma. They are produced purely for sports fishing as they grow quickly and fight aggressively when caught *

DSC_0612 Torrentfish (Cheimarrichthys fosteri) showing disruptive patterning from above. Waianakarua River *

DSC_9691 Pouched lamprey (Geotria australis) migratory adult freshly returned from the sea. This animal may spend up to 16 months in freshwater before spawning. As a sexually mature adult it will turn brown in colour, and if it is a male, it will develop a pouch. Niagra River, Catlins *

11004-11501 Bluegill bully (Gobiomorphus hubbsi) *

DSC_4550 Golden tench (Tinca tinca) are present in New Zealand in only very low numbers and were imported illegally recently. They occur in a few small ponds north of Auckland. They prefer slow-moving or still waters and are classified as ‘sports fish’, until recently they have been largely ignored by coarse fishermen, because they are timid and nocturnal. A licence is required to legally fish for them *

11004-04521 Canterbury galaxias (Galaxias vulgaris) developing egg mass. Canterbury galaxias spawn in spring (October to November) laying tiny 2 mm eggs in saucer-shaped depressions beneath large cobbles or boulders in fast-flowing riffles. Maerewhenua River *

DSC_4991 Black flounder (Rhombosolea retiaria) are most common in estuaries, harbours and lower levels of rivers, and may venture many kilometres upstream. Orokonui Lagoon *

DSC_1734 Spotted eel (Anguilla reinhardtii) a tropical eel native to eastern Australia, New Guinea, New Caledonia, Norfolk Island, and Lord Howe Island. This eel has been found in the Waikato River over the past 25 years. It has also been reported on the west coast from Northland to Taranaki , and on the east coast of the Coromandel Peninsula, so it may now be moderately widespread in northern NZ. Lake Karapiro, Waikato *

DSC_4732 Feral swordtail (Xiphophorus helleri) adult male. A feral population of this tropical aquarium fish established in the Waipahihi, a geothermal stream which flows into Lake Taupo. However a recent survey has failed to find any, and so that feral population may now be extinct. 'Green' swordtails (above) apparently from the wild, are still occasionally reported from Taupo area. The particular strain depicted, was first collected in 1951 from the Rio Lancetilla, Honduras in South America *

DSC_7356 Pouched lamprey (Geotria australis) this is 'tiny Tim' a developing ammocoete larva that was being closely monitored from the point of hatching, by researchers at NIWA. At one month old, when this photograph was taken in early February 2014, 'Tim' measured just 15mm, and is shown here displayed against a finger. Riccarton, Christchurch *

DSC_7302 Pouched lamprey (Geotria australis) this is 'tiny Tim' a developing ammocoete larva that was being closely monitored from the point of hatching, by researchers at NIWA. At one month old, when this photograph was taken in early February 2014, 'Tim' measured just 15mm. Ammocoete are filter feeders and live buried in the mud for the first four years or so of their life. Riccarton, Christchurch *

DSC_7261 Pouched lamprey (Geotria australis) ammocoete larva measuring 70mm. These filter feeders live buried in the mud for the first four years or so of their life, before transforming into macropthalmia and migrating downstream to the sea. Okuti River, Canterbury *

DSC_7262 Pouched lamprey (Geotria australis) head of an ammocoete larva measuring 70mm. These filter feeders live buried in the mud for the first four years or so of their life, before transforming into macropthalmia and migrating downstream to the sea. Okuti River, Canterbury *

DSC_7245 Pouched lamprey (Geotria australis) head of an ammocoete larva measuring 100mm, and in the process of transforming into a macropthalmia when this photo was taken in early February 2014. These filter feeding larvae live buried in the mud for the first four years or so of their life, before transforming over a period of two months into macropthalmia, and eventually migrating downstream to the sea. Okuti River, Canterbury *

DSC_7241 Pouched lamprey (Geotria australis) head of an ammocoete larva measuring 100mm, and in the process of transforming into a macropthalmia when this photo was taken in early February 2014. These filter feeding larvae live buried in the mud for the first four years or so of their life, before transforming over a period of two months into macropthalmia, and eventually migrating downstream to the sea. Okuti River, Canterbury *

11004-00204 Pouched lamprey (Geotria australis) macropthalmia, or juvenile lamprey photographed in autumn. After about 4 years living in the mud as an ammocoete, young lamprey change colour from blind, brown ammocoete larvae to this brilliant silver-blue over a period of about two months. During this time their eyes develop, and when they are about 120 mm long, and usually by winters end, they begin their journey downstream to the ocean. Okuti River, Canterbury *

DSC_9719 Pouched lamprey, or piharau (Geotria australis) migratory adult freshly returned from the sea. This animal may spend up to 16 months in freshwater before spawning. Two blue-green stripes are conspicuous on the upper surface of the body, but these will disappear as the upstream migration progresses. The blue-green coloration is caused by the deposition of biliverdin, a bile pigment produced as a breakdown product of haemoglobin. Niagra River, Catlins *

DSC_9634 Pouched lamprey, or piharau (Geotria australis) migratory adult freshly returned from the sea. This animal may spend up to 16 months in freshwater before spawning. Two blue-green stripes are conspicuous on the upper surface of the body, but these will disappear as the upstream migration progresses. The blue-green coloration is caused by the deposition of biliverdin, a bile pigment produced as a breakdown product of haemoglobin. Niagra River, Catlins *

DSC_9747 Pouched lamprey, or piharau (Geotria australis) migratory adult freshly returned from the sea. This animal may spend up to 16 months in freshwater before spawning. Two blue-green stripes are conspicuous on the upper surface of the body, but these will disappear as the upstream migration progresses. The blue-green coloration is caused by the deposition of biliverdin, a bile pigment produced as a breakdown product of haemoglobin. Niagra River, Catlins *

DSC_9690 Pouched lamprey, or piharau (Geotria australis) migratory adult freshly returned from the sea. This animal may spend up to 16 months in freshwater before spawning. As a sexually mature adult it will turn brown in colour, and if it is a male, it will develop a pouch. Niagra River, Catlins *

DSC_9691 Pouched lamprey, or piharau (Geotria australis) migratory adult freshly returned from the sea. This animal may spend up to 16 months in freshwater before spawning. As a sexually mature adult it will turn brown in colour, and if it is a male, it will develop a pouch. Niagra River, Catlins *

DSC_9684 Pouched lamprey, or piharau (Geotria australis) belong to an order of jawless fish and are characterized by a toothed, funnel-like sucking mouth. While some such as this species are well known for their ability to bore into the flesh of other fish to suck their blood, around 50% of lamprey species are not parasitic. This migratory adult may spend up to 16 months in freshwater before spawning. Niagra River, Catlins *

DSC_9640 Pouched lamprey, or piharau (Geotria australis) belong to an order of jawless fish and are characterized by a toothed, funnel-like sucking mouth. While some such as this species are well known for their ability to bore into the flesh of other fish to suck their blood, around 50% of lamprey species are not parasitic. This migratory adult may spend up to 16 months in freshwater before spawning. Niagra River, Catlins *