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Scleropages jardinii (Family Osteoglossidae)

Northern Saratoga

Distribution:

The Northern Saratoga is found in all rivers and floodplain lagoons that flow in to the Gulf of Carpentaria, westward to the Adelaide River in the Northern Territory. They are present in streams and lagoons on the east coast of Cape York Peninsula as far south as Temple Bay. Their distribution does not extend very far south in the lower Gulf Rivers due to low winter temperatures (QLD, NT).

Features:

The Northern Saratoga is a large, elongate fish that grows to 1 m, but is more commonly 50–70 cm long. They have a pair of barbels hanging down from the bottom lip, and the mouth faces upwards towards the surface. They are usually a greenish colour along the back, fading to silvery on the belly. Each scale on the sides has pinkish spots along the edge, which often join together. There are also reddish spots on the tail, dorsal and anal fins. The pectoral fin is very low on the body and tapers to a sharp point. The scales are large, over 20 mm across in large fish. The large size, barbels on the lower lip, very large scales and rounded tail make the Northern Saratoga a very distinctive fish.

Ecology/Way of Life:

Northern Saratoga live in the rivers and lagoons in the tropical area of northern Australia. They are unable to survive if temperatures get below 15°C. They are surface swimming fish, which can be observed cruising along the vegetation beds at the edges of lagoons during the day. They are also active during the night. They will eat almost anything alive that is at the surface of the water, particularly insects and frogs. They have even been seen to jump out of the water to grab an insect or frog on the shore! They also feed on crustaceans (yabbies and prawns), but have to turn on their sides to catch them, because their mouth faces upwards. Small fish are also taken if available. They prefer the slow flowing water of waterholes and lagoons, and generally stay well clear of flow. They also prefer clean water, and are no longer present in rivers that have been very turbid for a long time, such as the Palmer River. Northern Saratoga breed just before the wet season, from October through to December, when water temperatures are over 25°C. The female lays eggs the size of a large pea, which she incubates in her mouth for about 1–2 weeks. She cares for the fry for a few days after they hatch. She calls them back if she feels there is danger and they all return into her mouth. The male usually stays nearby while she incubates the eggs. When the fry leave the mother they are about 15–20 mm long, but grow very quickly and can be 100 mm long in a few months. The Northern Saratoga belongs to a very ancient family of fishes and is a primary freshwater fish. This means that they cannot tolerate salt in the water at all.

Interaction with Humans/Threats:

Northern Saratoga are a popular aquarium fish. In south-east Asia, a similar species called Dragon Fish (Scleropages formosus), is reputed to bring good luck to the owner, and people pay thousands of dollars for a good coloured fish. Northern Saratoga can grow very quickly and need a very large tank to live in. They are also prone to jumping out, so a good cover is needed for a tank. Northern Saratoga are a good sport fish, because they are near the surface and jump and twist when hooked. They can be hard to hook well because of the bony mouth. They can be eaten, but often have a muddy flavour, are very bony, and have soft flesh. Because they may take up to five years to mature, and lay very few eggs, they are vulnerable to overfishing. Because they cannot tolerate salt, the threat of rising salinity in northern Australian rivers is an issue of concern. It is also important not to use salt water as medicine to treat sick Northern Saratoga, as it will kill them.

Other Comments:

Scleropages jardinii was named by Saville-Kent in 1892. The genus name is based on Greek, Sclero meaning hard, bony and phagus meaning mouth. The species is named jardinii after the Jardines, a pioneering family who lived near the tip of Cape York Peninsula.

Further Reading:

Allen, G. R., Midgley, S. H. & Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Western Australian Museum. Perth. 394pp.

Leggett, R. & Merrick, J. R. (1987). Australian Native Fishes for Aquariums. J. R. Merrick Publications. Sydney. 245pp.

Merrick, J. R. & Schmida, G. E. (1984). Australian Freshwater Fishes: Biology and Management. Griffith Press Ltd. 409pp.

Larson, H.K. & Martin, K.C. (1990). Freshwater Fishes of the Northern Territory. Northern Territory Museum Handbook Series No. 1. Northern Territory Museum of Arts and Sciences, Darwin. 102pp.

Herbert, B.W. & Peeters, J. (1995). Freshwater Fishes of Far North Queensland. Department of Primary Industries Queensland. 74pp.

Acknowledgments:

Text: Brett Herbert. Distribution map: Peter J. Unmack. Photographer: Gunther Schmida.

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