Fisheries Infosite

Environmental Issue

Dredging (scallops) - Nelson fishery

Damage to the sea bed habitat from scallop dredging.
Dredge fishing is a significant risk to the integrity and productivity of marine ecosystems, particularly where this occurrs on sensitive habitats like bryozoans, mussels, sponges and corals; which are important nursary areas for some commercial species. So destruction of these habitats can reduce productivity of these fisheries. Marine life and productivity of commercial fisheries can also be significantly affected by sediment plumes created by dredging through muds and silts.
Extent of the issue
Repetative dredging of scallops in the Nelson region over the past 30+ years will have had a major impact on all fished grounds. It is likely that in their virgin state, some of these grounds were important both ecologically and to local fisheries. The 'footprint' of Nelson ring-bag dredges is likely similar to box dredges.
The Challenger scallop fishery is currently in poor shape. It is thought the effects of bottom dredging on the seabed may be a part of the problem. Research is currently underway to discover the problem with this scallop fishery and show how we can recover it.
Current management
The Challenger Scallop fishery is managed on a rotational basis, with some areas being left undisturbed for one or more years. Particularly sensitive seabed habitats at Separation Point (Tasman Bay) have been closed to trawling and dredging. Other closures include Marine Reserves in the Marlborough Sounds and Tasman Bay.
Future management
A Fisheries Plan has been proposed for the Challenger Scallop fishery. Effects of dredging on the seabed here will be considered as part of this plan. 
Documents / links
Challenger Scallop fisheries plan; Marine Protected Areas Policy and Implementation Plan, Jake Rice, global analysis - Kaiser 2006