Pipi at Whitianga

Purpose to determine the effect of the proposed rock groyne associated with the proposed marina at Whitianga on local pipi beds. To determine if the modified current regime will affect the pipi bed, and what the chances are of successful relocation of the pipi bed.The study involves a quantitative survey of the pipi bed at Whitianga including extent, density and size of pipi. Laboratory experiments designed to test the response of pipi to being manipulated in various ways was also undertaken.

Topographical map of site, height profiles of transects, density of pipi, size-frequency distribution of pipi comparative information on pipi populations in northern NZ, results of reburial experiments Experimental studies looked at: - burrowing time, - effect on growth and survival of various treatments (pipi placed on their sides on the bottom of the aquaria with no sand; pipi placed in the aquaria and covered with 5-6 cm of sand; pipi placed on their sides on top of 5-6 cm layer of sand; pipi placed upright and pushed into 5-6 cm of sand), - effects of burial under different quantities of sand, - ability to move up through the sediment, and effects of continual burial.

Intertidal and subtidal area to the west of Whitianga wharf.

Whitianga wharf – E2752078 N6481712, NZMG, 1:20000, AREA

Intertidal surveys 8-11 Sept 1987, 8-9 Oct 1987. Subtidal survey 9 Dec 1987.

0.1 m2 quadrats were pushed into the sediment as far as possible, and then sediment dug out to a depth of 10 cm. This sediment was sieved (5 mm) and pipi and other bivalves sorted. Pipi were measured into 5 mm size categories and returned to the sampling site. 81 samples were taken during the first intertidal survey visit and 20 during the second intertidal visit. The subtidal extent of the pipi bed was determined from qualitative examinations of the bottom approximately 150 m northward from the channel marker and up to 320 m offshore as well as 2 quadrat surveys along transect 14. Laboratory experiments involved transplanting 500 pipi into aquaria and conducting various treatments. Looked at burrowing time, effect on growth and survival of various treatments (pipi placed on their sides on the bottom of the aquaria with no sand; pipi placed in the aquaria and covered with 5-6 cm of sand; pipi placed on their sides on top of 5-6 cm layer of sand; pipi placed upright and pushed into 5-6 cm of sand), effects of burial under different quantities of sand; ability to move up through the sediment; effects of continual burial One off survey

Not reported Gaps in collection: Subtidal quantitative sampling was limited by strong currents. Data quality: Not reported Attribute accuracy: Not reported Completeness: Not reported

report, graphs, photographs

Finished

Report is available in Waikato Regional Council Library