Summary of the potential effects of fisheries on estuaries, mudflats and sandflats not covered by seawater at low tide

Fishery

Method

Potential effects

Cockle

Tractor towed dredge

Hydraulic dredge

Intertidal dredge tracks visible for varying amounts of time ie. Months in stable sediments, a tide in mobile sediments.

Sediment layers may be altered causing erosion to cockle bed.

Significant reduction in biomass of target and non target species immediately after fishing operation. Likely to be more pronounced with extended recovery times, ie many months, in areas with diverse communities and stable conditions.

Oysters and mussels

Dredge

Subtidal and intertidal dredge tracks visible for varying amounts of time, ie. months in stable sediments, hours in mobile sediments.

Top 10-15 cm of substrate disturbed and sediment plumes created

Change in benthic flora and fauna as a consequence of repeated dredging.

Clams

Hand gathering

Holes and tailings left on the intertidal visible for varying amounts of time, ie. months in stable sediments, a tide in mobile sediments.

Under size target species damaged or exposed to predation, desiccation or freezing.

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