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Land-based Effects on Fisheries and Ecosystems

Runoff from the land can have huge effects on our coastal ecosystems and the fisheries they support.

Streams and rivers carry sediments, nutrients and bacteria from our roads, farms and forests into the sea; while stormwater running down the drains from our streets and driveways pollutes estuaries and harbours with a cocktail of oil and other chemicals.

In many cases the effects of these are not instantly obvious and build up over many years. Occasionally, effects reach a point where we start to notice them – often when a fishery we care about is affected.

If no changes are made to the way we manage and use the land, sediment and other runoff could have ever-increasing impacts on both marine and freshwater ecosystems. This may cause many fish and shellfish populations to decline.

Everyone needs to be involved in addressing land-based effects, because we are all a part of the problem and all part of its solution.

The government’s goal is to see the health of affected ecosystems and fisheries restored. Some of the communities and groups working together to address land-based effects are already reporting positive results. For example, in Whaingaroa (Raglan) Harbour, water quality is now improved through a local initiative to fence and plant waterways leading into the harbour.

Similarly, in Golden Bay, farm runoff has been reduced through a local initiative involving local dairy and marine farmers, Fonterra, and Tasman District Council.

Many different groups have a stake in New Zealand's coastal and marine environment, and responsibilities for its management are shared among a range of central and local government agencies.

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Updated : 20 March 2009

Snapper nurseries at risk

Nearshore habitats that provide crucial nursery areas for juvenile snapper are particularly vulnerable to the effects of sedimentation.

These include subtidal seagrass meadows and horse mussel beds, which have now largely disappeared from most harbours in northwest New Zealand. They are thought to have been smothered over the years by silts and muds washed down off the land from roading and building sites, and from farming and forestry developments. The effects of plankton blooms caused by nutrients washed off the land may also have contributed.

All this leaves the Kaipara Harbour as perhaps the ‘last man standing’, in terms of nursery grounds supporting our entire North Island west coast snapper fishery.

Today, the Kaipara is under increasing pressure from the effects of a range of land-use activities – those that probably caused loss of sea grass beds in the other harbours. If we lose the Kaipara Harbour habitats, we could seriously endanger this snapper fishery.

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