Gollum galaxias facts for kids
Quick facts for kids Gollum galaxias |
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| Conservation status | |
| Scientific classification | |
| Genus: |
Galaxias
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| Species: |
gollumoides
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The Gollum galaxias (Galaxias gollumoides) is a special type of fish. It belongs to a group called galaxiids. This fish is only found in certain rivers and streams in the southern parts of New Zealand. You can find it in places like the Southland Plains, the Von River, and the Nevis River. It also lives on Stewart Island/Rakiura and throughout the Catlins.
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What Does the Gollum Galaxias Look Like?
The Gollum galaxias has a strong, slightly flat body. Its body gets narrower towards its tail, forming a long, deep "tail stem" (called a caudal peduncle). Its back is a bit arched, and its belly is flat.
Its top (dorsal) and bottom (anal) fins are short but tall and rounded. The anal fin starts just behind the dorsal fin. It has rounded pelvic fins, a rounded tail fin, and rounded side (pectoral) fins. This fish also has a short, blunt snout. Its mouth reaches back to just below the middle of its eyes. Both its upper and lower jaws are about the same length. It has large, pointed teeth (canines) on both jaws. Small sensory pores are also found on its head.
Like all fish in the Galaxiidae family, the Gollum galaxias has no scales. Its body color can be transparent beige or brown. It often has a silver or white belly. Sometimes, it has faint darker spots on its back near the tail. Other fish can be black to olive green, getting darker towards the belly. You might also see small black speckles and slight blotchy patterns on its body.
You can tell the Gollum galaxias apart from its relatives in a few ways. It only has six rays on its pelvic fins. It also has large eyes placed high on its head. This is a key feature. Its eye size is more than 23% of its head length. This is a trait it shares with only one other species, Galaxias anomalus. The first Gollum galaxias ever studied was about 75 millimeters (3 inches) long.
Where Does the Gollum Galaxias Live?
The Gollum galaxias lives only in fresh water. It prefers slow-moving or still streams in lowland areas. You can find these fish in both wetlands and stream habitats.
In streams, they often live where there is a lot of cover. This includes places with moss, woody debris (like fallen branches), and plants along the banks. The bottom of their habitat can be sand with algae, deep mud, or even bedrock and coarse granite sand. More Gollum galaxias are found in higher altitude areas.
Family Tree: Who Are Its Relatives?
The Gollum galaxias belongs to a group called the Galaxias vulgaris complex. This group includes 10 species. People once thought they were all the same fish, G. vulgaris. But now we know they are different species. These species are all very closely related to each other.
Life Cycle and Reproduction
During the winter months in New Zealand (June/July), scientists have seen Gollum galaxias fish with developing eggs. Fish that had recently laid eggs were found in November. Small young fish, about 25–30 millimeters long, were found in January/February. This tells us that the Gollum galaxias lays its eggs in spring. Many other galaxiid species that do not migrate also lay their eggs in spring.
The Gollum galaxias lives and reproduces only in freshwater. It does not travel to the ocean. This fish lays its eggs in fast-flowing streams with rocky bottoms. It also spawns in wetland habitats with muddy bottoms and plants along the edges.
The eggs are round and clear. They have pale golden yolks and small oil drops. The eggs are tiny and stick by themselves or in small groups (less than 20 eggs) to things like rocks and moss. Most spawning happens from late August to early September. Females lay the eggs, and males fertilize them outside their bodies.
Female Gollum galaxias from wetlands tend to lay more eggs than those from streams. This shows they have adapted to their local environment. Things like the type of bottom, water temperature, and how much daylight there is can affect when and where some Galaxias species lay their eggs. The Gollum galaxias might be able to delay spawning if the environment changes, like during cold temperatures or high water flows.
How Does the Gollum Galaxias Behave?
Many Galaxias species in New Zealand travel between the ocean and fresh water. But the Gollum galaxias does not migrate. It stays in freshwater.
Scientists have seen this fish jump out of the water. We don't know much about why they do this. They have also been seen digging. They aggressively rub their bodies against the bottom. The fish also rest on top of stones and spawning areas, often in groups. But they quickly hide when something disturbs them.
The Gollum galaxias avoids fast-moving water if it has a choice. It prefers slow water. It also seems to like covered areas more than open ones. This is probably to protect itself from predators. However, they have also been seen swimming in small groups in open water.
What Does the Gollum Galaxias Eat?
Like many other fish in its group, the Gollum galaxias eats insects that live on land. It especially likes insects from the order Trichoptera. These insects have young (larvae) that live in water and adults that live on land. The Gollum galaxias also eats insects from the orders Diptera, Ephemeroptera, and Plecoptera.
Who Are Its Predators?
The main predators of the Gollum galaxias are two types of trout: the brown trout (Salmo trutta) and the rainbow trout (Oncorhynchus mykiss). These trout are not native to New Zealand. They were brought there for sport fishing.
Why Is It Endangered?
The Gollum galaxias is listed as a threatened species in the New Zealand Threat Classification System. It is considered "Nationally Vulnerable." There is also not much data available about this species.
Being eaten by the introduced trout greatly affects their numbers. This is a big reason for their threatened status and small population. Other problems also cause the decline of freshwater galaxiids in New Zealand. These include losing their habitats due to building. Also, water quality is getting worse from pollution like fertilizer runoff. Changes to rivers also contribute to their decline.
