UC Are Cows Are Contributing To Decline in Whitebait?

UC Researcher Considers Whether Cows Are Contributing To A Decline In Whitebait

March 26, 2013

A University of Canterbury (UC) researcher is investigating whether increased nutrients in streams could be having an impact on New Zealand's whitebait fishery.

Nutrient run-off into streams, which is often associated with intensive farming practices, acts as a growth stimulant for aquatic algae and can eventually lead to decreased oxygen levels.

UC biology researcher Mauricio Urbina is investigating whether a decrease in oxygen could be having a direct impact on inanga, the most important fish species that makes up the whitebait catch.

``Young inanga swim upstream and those that are able to avoid the whitebaiters’ net inhabit small rural streams. Here they may encounter decreased oxygen in the water because of the nutrient run-off.

``Our studies discovered that inanga possess a number of unusual characteristics. Inanga are not very tolerant to low oxygen levels in the water. This results in the fish leaping out of the water onto the stream bank in order to avoid this potential stress. While out of the water, inanga can obtain oxygen from the air via its skin, a rare ability for a fish.

``My research showed that decreased water oxygen could act as an important barrier to inanga as they migrate upstream, or when they migrate back downstream to spawn, ’’ Urbina said.

"Furthermore, leaving the water may expose inanga to increased risks of predation and/or they could potentially dry out eventually leading to death. This would be of particular importance in streams where stream-side vegetation has been removed, another characteristic of waterways in areas of intense agriculture.’’

Urbina’s study has been supervised by Dr Chris Glover and has been funded by the Brian Mason Scientific and Technical Trust.

website: www.canterbury.ac.nz

ENDS

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