Fish and Game Update After Heatwave

February 2, 2018

The Pareora River at the huts and the Te Ngawai River at Cave were the standouts reaching peak temperatures of 27°C and 26°C, respectively, at about 4pm.

Although those high water temperatures only held for a short while they are getting into the zone where we might expect some fish to perish, especially if temperatures hold at over 25°C for long periods.

Keep in mind trout are survivors and within a river there will likely be cooler places they will actively seek out and hole-up until conditions improve.

I asked an ECan hydrologist how accurate the displayed temperatures were.

He said that they are generally reliable but suggested if the temperature sensor is in shallow water and direct sunlight that may have an effect of elevating recorded temperatures.

He also said that data are raw so may need to be reviewed for any technical errors.

Over the summer we have received several reports from anglers of sightings of dead trout and bullies, most notably from the Waitaki lakes.

We have sought expert advice from an aquaculture veterinarian and are confident that fish deaths this summer are most likely the result of natural environmental circumstances like fungal or bacterial infections common in wild fish populations and likely exaggerated by high summer water temperatures.

The recent outcome from the North Canterbury lakes investigation had a similar conclusion, and with the advice to carry on fishing and that the fish are fine to eat.

If you do find unusual numbers of dead fish, or sick and diseased looking fish please get in touch with us.

We can't always get there in time to investigate so photographing and freezing the fish could prove helpful to identify the issue.

It is not unusual to find dead fish during the hot summer months.

This is also the case during trout spawning, a small proportion of the population will perish each year.

With an outlook to the weekend, which for many will be a long one with Tuesday being a public holiday, it would pay to keep an eye on the weather/wind forecast and river flows.

The rain we received region wide on Thursday and this morning was sporadic and for some rivers it was substantial and for others it hardly made a difference.

At minimum it provided better water temperatures for fish and at best a good dung out of algae.

The Kakanui received its first decent flow since mid-November and the Maerewhenua got a short sharp 138 cumec pulse on Thursday.

Other rivers like the Te Ngawai, Ashburton and Ahuriri were still rising at the time of writing this newsletter on Friday morning.



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