Quantity
Surface water is the term used to describe all permanent freshwater streams, rivers, lakes and wetlands.
Surface water is important for the social, cultural and economic wellbeing of all Southlanders. Surface water is used for a variety of purposes, including domestic and municipal takes, agricultural, industrial, irrigation and forestry operations. The demand for these uses must be balanced against what is required to maintain the ecological wellbeing of waterways and protect in-stream values.
The consumptive use of surface water resources can place pressure on the ecological wellbeing of waterways in various ways. Rivers support a range of in-stream values that are largely sustained by a sufficient quantity of water and a particular flow regime. Lowered water levels can reduce the area of habitat available for fish species and stream bugs, especially in shallow, wide, streams. Species such as trout, eels and other native fish may be affected by higher water temperatures, lower dissolved oxygen levels, reduced feeding opportunities and poorer water quality in general. Surrounding vegetation, such as in wetlands, may be affected by lowered water tables.
If the flow regime and habitats are altered significantly, recreational values and pursuits can be affected, e.g. poorer quality fisheries or reduced bathing, boating or kayaking opportunities.
Fish monitoring
Fish are an important part of a freshwater ecosystem. Fish sit at the top of the food chain and any changes in their food source, which can occur as a result of changes in water quality, can impact on fish species and populations.
Other activities, such as grazing of stream margins, drainage of wetland areas, and straightening of streams can also affect fish. For example, grazing of stream margins reduces the amount of shaded habitat which fish utilise to shelter from high water temperatures.
A diverse range of fish species live within Southland’s freshwater bodies, from introduced sports fish such as rainbow and brown trout, to native eels, bullies and whitebait.
Since 2007/2008 Environment Southland has been undertaking fish surveys. They are captured via electric fishing in an enclosed part of a stream or river, then counted, measured, identified and released.
Through fish monitoring we aim to:
- Record an inventory of fish species/populations in selected streams on an annual basis
- Identify changes in fish numbers and species diversity due to impacts of variable habitat availability and quality
- Add to the water quality testing and bio-monitoring work carried out by Environment Southland to provide a greater indication of overall catchment health and longer term issues
- Collect important data for setting environmental (or minimum) flows, as we need to ensure adequate habitat is provided for fish and other aquatic life
Environment Southland is the brand name of Southland Regional Council.