Australian lungfish, Mary River turtle & Long-finned eel: Freshwater finds in Queensland’s Mary River

Just back from a chilly dive in the Mary River, a short drive from our place. This rural inland region is so beautiful and peaceful. We jumped in at a swimming hole, then swam upstream from there. The 14C (57F) water was absolutely freezing—well, compared to the balmy ocean I’m used to. For the first couple of minutes I couldn’t even think, or breathe, properly because the water was so biting. Must wear my drysuit next time.

I was able to give my new Sigma 17-70mm a test drive, and snapped a few shots of the freshwater fish life. Among the underwater sights, we were fortunate to have spotted a Queensland lungfish and a Mary River turtle. Both species are threatened. We also saw a Long-finned eel.

Unique among fish, the lungfish has a modified swim bladder that it uses to breathe air at the water’s surface. The lungfish will breathe this way to supplement the oxygen it takes in through its gills—which is especially important when water quality is low and oxygen levels are reduced. The species can even survive out of water for several days if the skin is kept moist.

Lungfish mature slowly, and won’t reach reproductive maturity for 17-22 years. They are particular about their spawning grounds: there must be suitable aquatic plants to protect the eggs and subsequent juveniles, and the water can’t be stagnant. If conditions aren’t right, a lungfish will re-absorb its spawn and wait for the next year. It will repeat this each year until conditions improve, or until the fish is too old to reproduce.

Already researches are noticing that there are fewer juvenile and young lungfish in the Mary River, which would indicate that either the adults are not spawning enough, or the eggs and juveniles aren’t surviving in the current river conditions. The Queensland Lungfish is a protected species, and was put on the CITES list in 1977.

The Mary River Turtle was only officially described in 1994. It has an uniquely long tail measuring two-thirds the length of its shell. It also has very long mandibles.

In the 1960s it was heavily collected by the pet trade. In recent years, its egg laying grounds are disappearing: riverbanks are eroding because of grazing cattle, and the river quality is altered because of human influences. The egg laying grounds that remain are often pillaged by dogs and foxes.

The Mary River Turtle is now among the world’s top 25 most endangered turtle species, and is on the IUCN Red List. It is the second most endangered turtle species in Australia.

—Liz

You may also be interested in:

• Josh’s underwater video from the Mary River
• Our underwater stock footage filmed in the Mary River
• Global Story’s powerful short film about the proposed Traveston Dam in the Mary River Valley