Impacts of seabed disturbance in the Waikato region

Report: TR 2023/04

Authors: Carina Sim-Smith, Shaun Lee and Simon Daniel (Coast and Catchment Ltd)

Globally, human activities have disturbed the seabed for thousands of years. Over time, the size and scale of seabed impact has increased with increasing technological developments and dwindling marine resources. The scale and nature of these impacts are not obvious to most people because they lie hidden beneath the waves.

This report discusses the main human activities that occur within Waikato’s coastal marine area (CMA) that physically impact the subtidal seabed. 

The report covers five main activities:

1. Bottom-contact mobile fishing (e.g., trawling, seining and dredging).
2. Sediment dredging and disposal.
3. Coastal developments (such as wharves, marinas, and other engineered structures).
4. Shellfish aquaculture.
5. Boat anchoring and swing moorings.

For each activity, the report discusses:

1.  The direct and indirect effects on the seabed arising from the activity.
2. The marine species and habitats that are most affected.
3. The spatial scale and intensity of the impact in the Waikato CMA, and the areas that are most affected.
4. The potential for recovery and probable recovery timeframes.

The report focuses on the immediate effects that arise when the activity is conducted.