Droughts a major potential threat to New Zealand fish

Droughts a major potential threat to New Zealand fish, UC research shows

July 7, 2013

The increasing intensity and frequency of extreme droughts is a major potential threat to New Zealand’s biodiversity and economic and cultural wellbeing.

In March this year, New Zealand experienced one of the worst droughts on record which severely impacted farmers economically.

The effects on native fish has been unknown until the University of Canterbury (UC) carried out a research project headed by biological sciences postgraduate Richard White.

``We measured the impact of the drought on mortality in 41 areas of the endangered brown mudfish in the ancient rimu forests of Westland Tai Poutini National Park near Hokitika.

``In these forests, the secretive, brown mudfish live in shallow pools created by falling rimu trees as they rip up large clumps of earth.

``Brown mudfish are extremely hardy and can cope with long periods without water, which they frequently experience in their forest pools, some of which are only five centimetres deep.

``However, this year’s drought may have been more intense than the fish may have previously experienced and their population response to the drought may be indicative of how less hardy fish species will cope with future climate change.

``Over 850 mudfish from 41 areas were monitored during the drought, which brought a maximum daily water deficit of 91mm to the south Westland region which normally experiences around 10 mm of rainfall daily, making it the one of the worst droughts on record for the region.

``The drought had a massive effect on brown mudfish mortality, with 25 percent of fish dying in most areas and up to 45 percent dying in the most shallow, drought-prone pools.

``In contrast, almost no fish died during the non-drought period leading up to March. These results alarmingly show that drought can be devastating to even the most drought-hardy fish in New Zealand.’’

White says less drought-hardy fish, such as whitebait and trout, may have fared far worse.

Given that future drought episodes are expected to increase in frequency and intensity the results are a cause for concern, White says.
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