Sampling event

Pasua (Tridacna maxima) size and abundance in Tongareva Lagoon, Cook Islands

Latest version published by Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node on 02 May 2024 Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node

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Pasua (Tridacna maxima), also known as pa’ua, are one of two species of giant clams native to the Cook Islands. Pasua are a culturally significant food item throughout the Cook Islands, and in the Northern Cooks remain a staple food source. Pasua are rare in the southern Cook Islands as a consequence of previous overharvesting but increasing numbers of pasua from the northern Cook Islands, especially Tongareva, are available for sale in Rarotonga. In response to declining numbers in the southern Cook Islands, a giant clam hatchery was established on Aitutaki in 1990 by the Cook Islands Ministry of Marine Resources (MMR) to help reintroduce clams to the lagoon.

The specific aims of the survey were to assess the size distribution, abundance and density of pasua in Tongareva Lagoon.

In addition, this survey aimed to provide baseline information for the Island Council regarding the establishment of specific size limits, the possible need for a rahui (harvest closure), and the ideal location of such a rahui if required.

Data Records

The data in this sampling event resource has been published as a Darwin Core Archive (DwC-A), which is a standardized format for sharing biodiversity data as a set of one or more data tables. The core data table contains 27 records.

2 extension data tables also exist. An extension record supplies extra information about a core record. The number of records in each extension data table is illustrated below.

Event (core)

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The table below shows only published versions of the resource that are publicly accessible.

How to cite

Researchers should cite this work as follows:

Chambers C N (2024). Pasua (Tridacna maxima) size and abundance in Tongareva Lagoon, Cook Islands. Version 1.0. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. Samplingevent dataset.


Researchers should respect the following rights statement:

The publisher and rights holder of this work is Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.

GBIF Registration

This resource has been registered with GBIF, and assigned the following GBIF UUID: 27b24738-02ef-4c81-b470-bfe639cd0c37.  Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node publishes this resource, and is itself registered in GBIF as a data publisher endorsed by Ocean Biodiversity Information System.




Charlotte N.L. Chambers
  • Metadata Provider
  • Originator
  • Point Of Contact
Institute of Geography, The University of Edinburgh
Drummond Street
EH8 9XP Edinburgh

Geographic Coverage

Tongareva Lagoon, Cook Islands

Bounding Coordinates South West [-9.04, -158.01], North East [-8.98, -157.92]

Taxonomic Coverage

Pasua giant clams

Species Tridacna maxima (Pasua)

Temporal Coverage

Start Date / End Date 2006-05-03 / 2006-05-24

Sampling Methods

The survey took place over 14 days from 3–17 May 2006 with a follow-up survey at sites Te Vo, Tepetepe and between Ahuamiria and Atutahi on 24 July 2006. Fieldwork was conducted by the author, Mataora Marsters and Taimana Manata from the Tongareva Marine Research Centre (TMRC) with additional assistance from Tomas Samuela Jr., Tuku Marsters, Martin Chambers and Baar Tapu. Site selection was designed in an attempt to survey a wide cross section of the lagoon environment, for example toka (distinct coral heads), tuarai (small scattered coral heads close to shore) and kauniho (reef edges). Sites were stratified according to the section of the lagoon (e.g. far southern section) and were selected by travelling in a boat within these sections in a relatively straight line (e.g. parallel to the shore) for a set period of time (e.g. 10 minutes) until suitable habitat was encountered. From preliminary observations and based on existing biological information concerning pasua (Lewis 1987), suitable habitat was defined as toka and tuarai down to a depth of 10 metres, and kauniho, which weren’t predominately sandy.

Study Extent Tongareva Lagoon, Cook Islands

Method step description:

  1. The survey area was delineated by four 50-m ropes, which were knotted to form a square. This was then placed randomly over the survey site although in the case of kauniho, the lines were placed at the edge of the kauniho extending towards the shoreline. Five transect lines were then placed within the square at 10-m intervals. All pasua found within 5 m on each side of the transect line were counted and a proportion of the total population measured. In cases where low numbers of pasua were present, every second pasua was measured but in situations where large numbers were found, measurements varied from every tenth to every one-hundreth pasua.
  2. The size distribution of pasua was evaluated by recording the length, measured in centimetres, along the shell opening (lip) using callipers. The census of pasua abundance in the lagoon was calculated by counting the number of pasua within each survey area; density was calculated as the total.

Bibliographic Citations

  1. Chambers, C. 2007. Pasua (Tridacna maxima) size and abundance in Tongareva Lagoon, Cook Islands. SPC Trochus Information Bulletin #13 – July 2007, pg. 7-12.

Additional Metadata

marine, harvested by iOBIS