Trochus (Trochus niloticus) size and abundance in Tongareva Lagoon, Cook Islands

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Descrição

Trochus (Trochus niloticus) were first introduced to the Cook Islands in 1957 from Fiji. Once the original population of 280 shells were well established in Aitutaki, trochus was introduced to the rest of the Cook Islands in the 1980s. The main purpose of the introduction was to develop commercially harvestable stocks to assist local economies. Four hundred and forty trochus were introduced to Tongareva (also known as Penrhyn) over 20 years ago in 1985 from the Aitutaki population (Sims 1988). Introduced populations usually reach commercially exploitable levels within 20 to 25 years, therefore, the trochus population on Tongareva should nearly be ready for harvest (Bertram 1998).A 1996 survey conducted in Tongareva by the Cook Islands Ministry of Marine Resources (MMR) found that trochus were present in the western section of Tongareva Lagoon with the highest densities found at two sites: Patukiri and Seniseni (Ponia et al. 1997). The survey detailed in this report was designed to re-assess the density of trochus in Tongareva Lagoon, 10 years after the last survey and 20 years after the original introduction.The specific aims of the survey were to: • assess the size distribution of trochus, • assess trochus abundance and density in the western section of the lagoon, and • estimate the number of trochus that could be sustainably harvested from the surveyed area of the lagoon.

Registros de Dados

Os dados deste recurso de evento de amostragem foram publicados como um Darwin Core Archive (DwC-A), que é o formato padronizado para compartilhamento de dados de biodiversidade como um conjunto de uma ou mais tabelas de dados. A tabela de dados do núcleo contém 10 registros.

Também existem 2 tabelas de dados de extensão. Um registro de extensão fornece informações adicionais sobre um registro do núcleo. O número de registros em cada tabela de dados de extensão é ilustrado abaixo.

110

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Versões

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Como citar

Pesquisadores deveriam citar esta obra da seguinte maneira:

Chambers C N (2024). Trochus (Trochus niloticus) size and abundance in Tongareva Lagoon, Cook Islands. Version 1.1. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. Samplingevent dataset. https://nzobisipt.niwa.co.nz/resource?r=tongareva_clams_trochus&v=1.1

Direitos

Pesquisadores devem respeitar a seguinte declaração de direitos:

O editor e o detentor dos direitos deste trabalho é Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.

GBIF Registration

Este recurso foi registrado no GBIF e atribuído ao seguinte GBIF UUID: 44c33d16-84bd-41d3-8e39-bed4786eca9c. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node publica este recurso, e está registrado no GBIF como um publicador de dados aprovado por Ocean Biodiversity Information System.

Palavras-chave

Samplingevent

Contatos

Charlotte N.L. Chambers

Provedor Dos Metadados ●
Originador ●
Ponto De Contato

Researcher

Institute of Geography, The University of Edinburgh

Drummond Street

EH8 9XP Edinburgh

Scotland

Cobertura Geográfica

Tongareva Lagoon, Cook Islands

Coordenadas delimitadoras	Sul Oeste [-9,04, -158,01], Norte Leste [-8,98, -157,92]

Cobertura Taxonômica

Giant clams

Espécie	Trochus niloticus

Cobertura Temporal

Data Inicial / Data final	2006-05-03 / 2006-05-31

Métodos de Amostragem

The survey took place from 3–11 May 2006 with a follow-up survey in Patukiri on 31 May 2006, in conjunction with a survey of pasua (Tridacna maxima) populations. 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 and Tuku Marsters. Surveying was concentrated in the western section of the lagoon as this was where the highest numbers of trochus were discovered in the previous survey. However, any trochus encountered in other sections of the lagoon during the course of the pasua survey were also to be recorded although none were found.

Área de Estudo	Tongareva Lagoon, Cook Islands

Descrição dos passos do método:

From preliminary observations and also based on previous surveys of trochus numbers, it was observed that trochus were distributed with increasing density towards the edge of the inner lagoon reef (kauniho). Transect lines were accordingly placed at the edge of the kauniho extending towards the shoreline. The survey was conducted using a 50-m transect line laid parallel to the edge of the kauniho with five transect lines running perpendicular at 10-m intervals. All trochus found within 5 m on both side of the transect line were counted and all were measured except those surveyed at TMRC, where approximately every second trochus was measured (i.e. 39% of the population) and Patukiri North where 85% of the population were measured.
The size distribution of trochus was evaluated by recording the basal diameter of trochus using callipers. The census of trochus abundance in the lagoon was calculated by counting the number of trochus at each site; density was calculated as the total number of individuals divided by the area sampled, which at each site was 2500 m2. The calculation for the amount of trochus available for sustainable harvest was based around 30% of the population in the 8–12 cm size range as per harvest regulations established in Aitutaki. Ten sites were surveyed.

Citações bibliográficas

Chambers, C. 2007. Trochus (Trochus niloticus) size and abundance in Tongareva Lagoon, Cook Islands. SPC Trochus Information Bulletin #13 – July 2007, pg. 2-6.

Metadados Adicionais

marine, harvested by iOBIS

Identificadores alternativos	https://nzobisipt.niwa.co.nz/resource?r=tongareva_clams_trochus