The country’s oldest ecosanctuary is looking a little drier than usual as staff try to eradicate around 22,000 fish, throwing the ecosystem off-balance.
The lower reservoir at Wellington’s Zealandia has been lowered six metres in an attempt to get rid of the European perch, which are eating the sanctuary’s native fish.
“They also take out a lot of our invertebrate community,” says Zealandia’s Director Danielle Shanahan. “Now that invertebrate community is incredibly important because they normally eat the algae, so without the invertebrates we end up with algal blooms.”
Algal blooms can produce toxins, putting the sanctuary’s other fish in danger.
The water’s being pumped out across a spillway into the Kaiwharawhara Stream, which should make eradicating the perch an easier job.
“We’ve done some netting of the fish, we’ve also used something called electric fishing which is where you basically put a zap of electricity through the water and stun the fish,” she says.
“But now this last stage is about using a substance called rotenone, which we apply to the water and that kills the fish very quickly.”
Staff have removed as many other species of fish as possible from the lower reservoir to move them out of harm’s way.
It’s expected the reservoir can start to fill up next month, with the help of some Wellington rain.
“We can start afresh,” Shanahan says, “and start breathing life back into this incredible water body.”