Mary River cod facts for kids
Quick facts for kids Mary River Cod |
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The Mary River cod (Maccullochella mariensis) is a special type of temperate perch fish. It lives only in the Mary River system along the coast of southern Queensland, Australia. These fish are among Australia's most endangered freshwater fish. They are also the northernmost of the four types of Maccullochella cods found in eastern Australia's coastal rivers.
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What They Look Like
The Mary River cod is a large fish. Long ago, some were found to be almost 40 kilograms (about 88 pounds) and 120 centimeters (about 4 feet) long! Today, most are smaller, usually less than 5 kilograms (11 pounds) and 70 centimeters (2.3 feet) long.
These fish look a lot like their relatives, the Murray cod and eastern freshwater cod. They have beautiful colors, from golden-yellow to dark green or brown, with dark green or black spots. A unique thing about Mary River cod is that their "tail wrist" (the part connecting their body to their tail fin) is a bit shorter and thicker than other cod species.
Why They Need Our Help
The Mary River cod is listed as an endangered species. This means it's at high risk of disappearing forever. Experts believe they now live in less than 30% of the places they used to call home.
Sadly, the Mary River cod has faced many problems. When Europeans first settled in Australia, there were huge numbers of these fish. But they were caught too much, using nets, lines, and even explosives. People even used them to feed pigs!
This overfishing was a big problem. Other issues also hurt the fish:
- Habitat loss: Rivers became muddy from land clearing.
- Riverbank damage: Plants along the river were destroyed, and cattle walking on the banks caused damage.
- Dams and weirs: These structures blocked the fish from moving freely up and down the rivers to find food or places to lay eggs.
All these things have made it very hard for the Mary River cod to survive. They are large, grow slowly, and live a long time, which makes them more sensitive to these changes.
Protecting Mary River Cod
To help protect these fish, strict rules are in place. In most places, if you catch a Mary River cod, you must carefully release it back into the water. It's a "no take" species.
However, in a few special dams and lakes in Queensland, like Cressbrook, Hinze, Maroon, Moogerah, North Pine, Somerset, and Wivenhoe Dam, you can fish for them. But even there, there's a strict rule: you can only keep one fish, and it must be at least 50 centimeters (about 20 inches) long. This helps make sure enough fish are left to reproduce.
How Scientists Classify Them
Scientists first thought the Mary River cod was a type of Murray cod. They called it a "subspecies" based on studies of its body proteins.
But in 2010, after looking closely at their DNA, scientists decided the Mary River cod is a completely separate species. They found that its closest relative is actually the eastern freshwater cod (Maccullochella ikei), which lives in the Clarence River system.
