Why fish passage is vital for fish migration

Have you ever caught a fish and wondered what journey it’s been on, or the obstacles it’s had to encounter?

Many of Queensland’s native fish species, including popular recreational and commercial species, migrate at some point in their life. This could be to breed, recolonise areas, and to access new food and habitats.

Some fish species move between fresh and salt water. This movement is called diadromous and is undertaken by fish species such as barramundi, Australian bass, jungle perch and sea mullet.

Native fish species that complete their lifecycle in freshwater also have a requirement for movement within the river systems. This type of movement is termed potamodromous and is undertaken by fish species such as golden perch, silver perch and Murray cod. Golden perch have a recorded migration of up to 2,300 km during times of flow – that’s like swimming from Brisbane to Auckland!

Migration patterns of fish can be restricted through the construction of dams, flood levees, weirs and road crossings. Even small changes in water level, as much as 10 cm drop, can obstruct small bodied native fish, leading to reduced native fish populations.

Any delay or blockage to native fish movement significantly reduces their long-term viability. This is why Fisheries legislation in Queensland requires adequate fish passage at structures built within waterways.