Population abundance estimates of the New Zealand geoduck clam, Panopea zelandica, using north american methodology: Is the technology transferable?

This study investigates the applicability of methods used to describe patterns of distribution, and estimates of density and biomass of the Pacific geoduck clam, Panopea abrupta, from western North America for populations of the New Zealand geoduck, Panopea zelandica in Kennedy Bay, on the Coromandel Peninsula, and in Wellington Harbour. Central to this is the use of line transect surveys and estimations of the detection rate of geoduck (show-factor) using counts of siphon holes. Studies were restricted to less than 17 m water depth. Geoduck in Kennedy Bay were found from 4-8 m water depth, whereas geoduck in Wellington Harbour occurred in several separate beds from 4-16 m. In Wellington Harbour, there was a pattern of increasing numbers with depth up to ~15 m. Numbers seemed to decrease thereafter. Analysis of sediment samples indicated that P. zelandica was more prevalent in fine sand to fine silty sand substrates. P. abrupta is found in similar habitats. There was no significant difference in the show-factor (the proportion of geoduck detectable by sight or touch vs. the actual number of geoduck present) of geoduck with respect to season (summer and winter), region (Wellington Harbour and Kennedy Bay), or tidal height (low, mid, and high tide)