West Coast Shellfish and Habitat Mapping

This project aimed to map the distribution and abundance of Cockles and Wedge Shells in Kawhia and Aotea Harbours, and to record the presence and abundance of other macrofauna and habitat types. Seagrass was present in large areas of the intertidal area of both harbours. Muddy sand was the predominant habitat type towards the middle of both harbours. Areas exposed to greater wave action consisted of sandy sediment, while less-exposed areas tended to be muddier. The upper reaches of both harbours consisted of sandy-mud to mud habitats. In both harbours, cockes were the most abundant shellfish species recorded, followed by wedge shells. Seagrass was the most abundant plant. Shellfish density was highest in sand, muddy sand and sandy mud rather than mud. In Kawhia Harbour, shellfish abundance was affected by an interaction between the presence of seagrass and sediment type. This was also the case for cockles in Aotea Harbour, but not for wedge shells. This information is a good baseline with which future observations can be compared. Sediment characteristics have also been described, allowing future assessments to gauge the extent of increase (or decrease) in muddy sediments entering the harbour.

Data includes cockle and wedge shell counts for 2133 sites in Kawhia Harbour and 392 in Aotea. Observations of vegetation and substrate characterisics. Full detail in attached report.

Kawhia and Aotea Harbours, West Coast Waikato Region.

The bulk of the sampling was undertaken between 11 December 2007 and 1 February 2008, with an additional sampling day on 18 February 2008, and a second sampling period between 25 April 2008 and 5 May 2008.

Full methodology in attached report. Samples were collected at 100 m spacing, based on a grid created on GIS. A 25 cm × 25 cm quadrat, excavated to 10 cm Surface vegetation was observed, percentage cover (visual assessment) Sediment type was recorded (judged by rubbing the sediment between the fingers and by noting obvious visual characteristics) Presence and number of surface-dwelling mollusc species inside the quadrat were recorded. Species, number and size class (cockles, wedge shells and pipi only) of these molluscs were recorded. For cockles and wedge shells, size classes based on shell length were recorded as: Small (<?15 mm) (minimum detectable size = 5 mm) • Medium (15–25 mm) • Large (>?25 mm) Sediment samples collected at 23 sites. Analysed with galai.

Not all grid points were sampled. Some areas were not accessible. Some sites were very muddy and slow to access, though early observations indicated that the target species were not present at muddy sites.

Data has been transformed into a range of formats, see attached report.

See attached report

Contact Department of Conservation

Data collection complete.