Tuna (Eel) Lifecycle Wooden Puzzle with Image Tray
Tuna are endemic to New Zealand. They are found in freshwater like lakes, rivers and streams. They grow up to around 1.2 metres to 2 metres. Tuna feed on a range of prey like small fish, fish eggs, mice, ducklings and also carrion. They have a very dark colouration. Their skin is silky and soft but also easily damaged. Tuna can absorb oxygen through the skin allowing them to travel on moist land. The Tuna is a very long-lived fish, with records of females reaching 106 years old and weighing up to 24 kg. They have the slowest growth rate of any eel species studied, just 1–2 centimetres a year.
The Tuna has an unusual life cycle: they grow and mature into fertile adults in fresh water, then migrate to the sea to breed. Tuna breed only once at the end of their lives, making a journey of thousands of kilometres from New Zealand to their spawning grounds near Tonga. The Tuna lays her eggs and then dies. The eggs float to the surface to hatch into very flat leaf-like larvae that then drift along large oceanic currents back to New Zealand. This drifting is thought to take up to 15 months. Upon arriving in New Zealand, the larvae undergo a transformation into glass eels, like small transparent adult eels. These occupy estuaries for their first year, during which they develop colouration and become elvers, which resemble small adult eels. The elvers migrate upstream, where they develop into adults.