Report considers effects on anchors and moorings on Sounds seabed

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Report considers effects on anchors and moorings on Sounds seabed

The Marlborough District Council has joined forces with the Cawthron Institute in an effort to better understand the environmental effects of moorings on different types of marine habitat in the Marlborough Sounds.

Marlborough District Council Coastal Scientist Dr Steve Urlich says there are over 3,000 swing moorings for boats in the Marlborough Sounds and in some instances, these could be causing significant damage to fragile types of living seabed habitat when they are dragged along the sea floor.

The typical mooring used in the sounds normally consists of an anchor, or concrete block, attached to a chain.

The report shows that the dragging of the ground chain can damage or destroy sensitive habitats such as rhodolith beds or tubeworm mounds, and kill organisms living on the sediment such as horse mussels, resulting in the loss of fish spawning and nursery areas within a 360 degree arc around the mooring anchor block.

Acting Chair of Council’s Environment Committee Gerard Hope welcomes the report. “We need this sort of information to help us build a broader picture of what goes on under the water and to better understand the effects of different types of disturbances to our seabed ecosystems.”

“On the up-side, we now know that the new mooring technologies and refinements of existing designs have reduced effects on the seabed, and may be more suitable in certain types of marine habitats,” Hope said. “But we need to do more work to identify where these sensitive habitats are.”

The Council will use the information in the Cawthron report in conjunction with information collected from the Queen Charlotte Sound/Tōtaranui multibeam seabed survey that will be completed in mid 2018. This survey will provide, for the first time, a picture of the effects of scour sweep marks in every bay in the Queen Charlotte/Tōtaranui.

This information will identify at risk areas and will help inform the Council’s regulatory functions in future.

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The information in this media statement was correct at time of publication. Changes in circumstances after the time of publication may impact on the accuracy of the information.