How do you keep tabs on trout numbers?

How do you keep tabs on trout numbers?

One way of course, to plunge underwater and count ‘em – although in winter it’s a chilly business. Eastern Region Fish & Game officers have just braved the cold at the Tarawera outlet to count the trout in the river.

A ‘drift dive’ involves officers who don wetsuits, snorkel mask and fins, and float down stream in formation with the current for one kilometre - counting fish as they go. Fish and Game Officer Matt Osborne says the drift dives, normally carried out in June, July and August, are “another tool in their tool box - along with fish trap counts and angler surveys - for gauging fish numbers and the number of trout spawning.”

The latest dive turned up 814 large fish, the spawning ones, while there was no sign of “little guys” - younger one year-old fish which, as normal, swim off into the lake at this time. Happily, the counts taken of spawning fish at the Tarawera outlet have been rising for the past five years, at a rate of about 10 per cent a year.

Sadly for anglers, this doesn’t necessarily translate into big fish hooked, because of various factors at play, including weather conditions.

Matt Osborne says the dives are a fairly accurate way of keeping tabs on fish population trends, because although some fish dodge the count in “hidey-holes,” on every dive they’ll sight the same percentage of total fish present. He says that trout are always present in far greater numbers than visible from the bank. “Two that you spot from the shore, can often turn into 22 underwater.”

ENDS

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