Environmental flows stimulate the upstream movement of juvenile diadromous fishes

Published source details Amtstaetter F., Tonkin Z., O'Connor J., Stuart I. & Koster W.M. (2021) Environmental flows stimulate the upstream movement of juvenile diadromous fishes. Marine and Freshwater Research.
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This study is summarised as evidence for the following.

	Action	Category
	Modify flow regimes along regulated rivers (e.g. release water to encourage upstream movements) Action Link

Modify flow regimes along regulated rivers (e.g. release water to encourage upstream movements)

A controlled, before-and-after study in 2018 in two rivers in Victoria, Australia (Amtstaetter et al. 2021) found that releasing water from a reservoir in summer resulted in greater numbers of juvenile short-finned eels Anguilla australis moving upstream compared to before the water release or in a regulated control river. During a summer water release, catches of juvenile short-finned eels moving upstream were two-fold higher than 1–2 weeks before the release, and 26-fold higher than in a regulated control river without a summer release (data reported as statistical model results). In summer (February) 2018, water was released over 14 days from a reservoir into a river (peak discharge 81 megalitres/day). Outside of this period, river discharge was regulated at base-flow conditions (<10 megalitres/day). A second regulated river (discharge 2–54 megalitres/day) had no summer water release. Juvenile short-finned eels (<250 mm long) were caught in a fyke net at each of six sites in the treatment river, and three sites in the control river, during the summer water release period (for 96 h) and 1–2 weeks prior (for 72 h). Sampling sites were spaced 250 m apart. Captured eels were counted and released.

(Summarised by: Anna Berthinussen)