Publications: Research reports and publications

Water quality guidelines to protect trout fishery values

1 September, 2006
Cawthron Report 1205. Prepared for Horizons Regional Council.


Horizons Regional Council (Horizons) have sought water quality guidelines for the protection of trout fisheries values in streams identified as significant trout fisheries in their area of jurisdiction.

This report provides three tables of water quality guidelines, the first containing guideline values for fisheries identified as "Outstanding" or "Regionally significant", the second containing guideline values for fisheries classified as "other significant fisheries", and the third containing guideline values for protection of spawning and incubation in recognised spawning streams. Some background information is also provided for each of the water quality guidelines contained in the tables.

It is our opinion that the four key parameters for the protection of adult trout are water temperature, dissolved oxygen, water clarity/ turbidity, and food (represented in this case by the Macroinvertebrate Community Index (MCI)). Temperature and dissolved oxygen have obvious direct effects on metabolism, while water clarity can influence foraging efficiency for drift feeding trout (the most common feeding behaviour of trout in New Zealand streams).

For spawning and incubation the main issues are also temperature and dissolved oxygen, as well as maintaining a relatively low fine sediment fraction in the substrate. Suitable guidelines for water clarity and the MCI could act as surrogate controls on fine sediment load in this instance, since the fine sediment fraction is laborious to measure.