Inanga
The common galaxias (Galaxias maculatus) or inanga (from the Māori īnanga) is a very widespread Southern Hemisphere fish in the family Galaxiidae. It is a slim, narrow fish with a forked tail and a mottled, spotty pattern, typically about 10 cm (4 in) long when fully grown. It lives in fresh water, but spawns at river mouths and spends the first six months of its life at sea, returning en masse in spring. Its vernacular names include cowfish, jollytail, common jollytail, eel gudgeon, inaka, native trout, pulangi, puye, slippery tarki, spotted minnow, Falklands minnow and whitebait.
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
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starts withCommon galaxias have iridescent silver eyes, undersides, and gill covers, and some have an iridescent green stripe along the top of their bodies which can be intermittently seen as they swim. Their specific name maculatus ("spotted") comes from the pattern of dark-mottled, leopard-like spots on an olive-brown background along their upper bodies. This pattern ranges from very subtle to quite bold. Common galaxias have slightly forked tails, unlike other most other galaxiids, which have square tails. Adults typically range from 8–11 cm (3.1–4.3 in) in length, with an average of 10 cm (4 in). The maximum reported length 19 cm (7.5 in).
They are commonly found in small schools or shoals in slow-moving water, but can be more solitary in swifter streams.
Common galaxias are one of the most widely distributed freshwater fish in the world. They inhabit Chile (35–55°S), Patagonia, Argentina, the Falkland Islands, some Pacific Islands such as New Caledonia, New Zealand, and coastal streams in south-eastern Australia, Tasmania, and southwest Western Australia.
Adults are mainly found in still or slow-moving water in the lower parts of coastal streams and rivers, or around the edges of lagoons; they can tolerate a wide range of natural conditions. If oxygen levels are low as a result of eutrophication, they can jump out of the water (emerse) and take up oxygen through their skin as a last resort. They need access to riparian vegetation for spawning, and usually live in river systems with access to the sea, as their larval stage is marine. They tend to be found in lower-elevation streams as unlike other species of Galaxias they cannot climb past waterfalls.
Common galaxias can become land-locked (such as in five lakes in Northland, New Zealand), feeding and breeding in large beds of reeds.
Adult fish typically reach sexual maturity at one year and spawning is triggered by changes in day length and temperature. Unless landlocked within a lake, the common galaxias spawns mainly in autumn during spring tides in the tidally influenced reaches of rivers and streams but spawning in winter and spring has occurred. The eggs are laid en masse amongst flooded riparian vegetation by females. Male fish then release sperm into the water and the eggs are fertilised externally.
This type of spawning is called polygynandry. Eggs remain attached to the vegetation as the tide recedes. Two types of reproductive strategy occur: the most common is a 'boom bust' strategy whereby spawning occurs in one event and is followed by death (semelparity), or much more rarely spawning occurs in multiple years before death iteroparity.
Galaxiid species are, in general, threatened by human activities such as intensive agriculture and land change use. These activities have removed vegetation from stream banks that are needed for spawning to protect eggs from the sun. The increased nutrient input into streams from farming can lead to eutrophication. In New Zealand, their conservation status is declining, mostly because of habitat loss and degradation.
As adults, common galaxias eat insects, crustaceans, and molluscs. This is the same diet as introduced trout, which not only compete for food, but also readily eat them. In areas where trout have become naturalised, common galaxias are scarce. Common galaxias, therefore, are mostly found in stretches of streams and rivers that are less suitable for introduced trout.
