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Another successful trout spawning season

Meridian Energy helps another successful trout spawning season

Meridian Energy and Fish and Game NZ are working together to ensure another successful trout-spawning season in the Upper Waiau River, the outlet of Lake Te Anau.

Hundreds of adult rainbow trout are presently creating their next generation on the river’s gravel beaches. In this annual occurrence, adult trout of this highly valued fishing river return to the areas where they themselves were spawned.

Spawning involves a hen excavating a shallow hole (called a redd), then laying eggs in the hole, which the male fertilises at the same time. In the Upper Waiau the trout favour the suitably sized gravel and cobbles found on the inside of the river’s sweeping bends.

The hen then excavates another hole immediately upstream and repeats the process, with the gravel from the second hole covering the first hole, and protecting the eggs from predators.

After a 65-day incubation period, the trout fry “swim up” and begin their life, with a small percentage surviving three years to continue the cycle.

Meridian Energy liaises with Fish and Game NZ over the management of flows in the river during the spawning period. Meridian attempts to hold a river level that maintains a flow over the redds until fry emergence is complete.

Colin Sinclair, a member of Meridian Energy’s natural resources team based in Southland, says a balance between the power generator’s operational requirements and environmental values is needed.

“This can be difficult with the incubation period of the last eggs extending to at least late October. At this time, the water storage in Lake Te Anau is typically low after a winter’s generation at the Manapouri Power Station,” says Colin Sinclair.

“We start by reducing the flow, encouraging the trout to spawn in parts of the river where Meridian can be confident of maintaining a flow high enough to cover the gravel where the eggs are laid,” explains Colin Sinclair.

Fish and Game NZ officer Bill Jarvie says that around 150 rainbow trout spawned on the principal beach, Yarex Reach, last year. “That was the highest number of trout which have spawned on the river in the past two decades,” says Bill Jarvie.

Alan Seay, spokesman for Meridian Energy, says the company works very closely with the environment in its generation activities.

“This is part of Meridian’s commitment to mitigate any adverse effects of its hydro operations. We undertake environmental initiatives such as this as part of our stakeholder agreements for our resource consents,” says Alan Seay. [ends]


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