A large, elongate, cylindrical eel. Maximum size 1,650 mm and 22 kg, but typically about 1,000 mm and 1–2 kg. The mouth is large, extending back well past the eye. The back and sides of the body are distinctly blotched or mottled with dark brownish spots or patches. Like the Short-finned eel, the dorsal, anal and caudal fins are joined. It is readily differentiated from the Short-finned eel by the spotted body pattern and length of the dorsal fin which commences well in front of the anal fin.
Similar to the Short-finned eel but more commonly recorded in rivers than lakes. Preferred habitats include undercut banks and areas with snags. Both Long-finned and Short-finned eels are thought to breed in the vicinity of the Coral Sea to the northeast of Australia. Spawning is less confined seasonally than for Short-finned eel, with year round spawning suggested. Long-finned eel juveniles leave marine waters to enter freshwater environments at a younger age than Short-finned eel, suggesting that the spawning grounds may be slightly closer to Australia (around Fiji) than for Short-finned eels. The larvae and glass eels take about 6 months to migrate the ~2,000 km from the spawning grounds to the Australian east coast. As the leaf-like larvae (leptocephali) approach the continental shelf they metamorphose into the traditional eel shape (glass eels) and the glass eels (~58 mm length) enter estuaries and migrate upstream to freshwater habitats in summer and autumn. As with Short-finned eels, entry to freshwaters is usually facilitated by flood tides, usually at night. Long-finned eels may remain in freshwaters for up to 52 years before returning to the ocean to spawn and die. Long-finned eels in freshwater habitats generally have a restricted home range of 300 m or less, although larger movements are recorded when the eels return to the sea to spawn. Size and age range in coastal Australian rivers varies between the sexes with females generally larger and older (up to 52 years of age) than males. Annual growth can be 30 to 167 mm per year but is highly variable between years and populations. Growth is significantly faster in younger (5–15 years) eels with fish >15 years old substantially slower growing, and with females growing slightly faster than males. Long-finned eels in freshwater habitats grow slower than those in estuarine/tidal habitats. Size at sexual differentiation and migration also varies between the sexes: males differentiate at 42–60 cm and migrate at 44–62 cm and females at 50–76 cm and 74–142 cm, respectively. The majority of males are found in the tidal zones whilst females dominate abundance (up to 97% of individuals) in freshwater habitats.
Like the Short-finned eel, the Long-finned eel is a nocturnal predator of fish, crustaceans, molluscs and insects, and the occasional juvenile waterfowl. Both Short-finned and Long-finned eels > 30 cm in length are principally piscivorous. Long-finned eels < 30 cm are more omnivorous and eat a wide range of crustaceans as well as fish.
Eels are generally only recorded from coastal streams outside the Basin. This species is more commonly found in lowland sections of coastal streams although it is occasionally recorded from upland sections as well. However, it is far less abundant in upland habitats than the Short-finned eel. There are very few records of this species from the Murray–Darling Basin, with records from the Condamine-Balonne drainage in southern Qld, the Narran, Macquarie and Darling rivers in northern NSW and the Molonglo River in the ACT. The Molonglo River record is likely to be a result of translocation by anglers, as this practice is known to occur in the ACT for Short-finned eels. There are anecdotal reports of the species moving across flooded pasture in the northern Condamine catchment, near the Bunya mountains, and it is speculated that individuals in this catchment may have crossed the divide from the adjacent coastal Burnett catchment. Historic records of large individuals (> 1m length) of this species from the Macquarie River in 1912 near Trangie and Darling River at Wilcannia in 1907 were considered ‘isolated specimens’ or ‘strays’ by NSW Government Naturalist David Stead. He considered that they had possibly crossed into the headwaters of the Macquarie from the adjacent headwaters of the Hunter River. No Long-finned eels were recorded in the Sustainable Rivers Audit monitoring in the Basin from 2004–2013, or in the MDB Fish Survey from 2014/15–2021/22.
None known in MDB, but in coastal systems barriers to downstream migration of adults, particularly hydroelectricity schemes and associated turbines are cause for concern. Coastal wetland drainage and conversion may also be threats. Changes to oceanic currents associated with climate change will also affect larval dispersal.
Béguer-Pon et al. 2017; Beumer 1979a, 1996; Jellyman 2016; Koehn & O’Connor 1990; McKinnon 2002; McKinnon et al. 2002; Moffat & Voller 2002; Pease 2004; Pease et al. 2003; Shiao et al. 2002; Silberschneider et al. 2004; Sloane 1984a,b; Stead 1908; Walsh et al. 2003, 2004, 2006. G Ringwood pers. comm.
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