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

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Descripción

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

Los datos en este recurso de evento de muestreo han sido publicados como Archivo Darwin Core(DwC-A), el cual es un formato estándar para compartir datos de biodiversidad como un conjunto de una o más tablas de datos. La tabla de datos del core contiene 10 registros.

también existen 2 tablas de datos de extensiones. Un registro en una extensión provee información adicional sobre un registro en el core. El número de registros en cada tabla de datos de la extensión se ilustra a continuación.

110

Este IPT archiva los datos y, por lo tanto, sirve como repositorio de datos. Los datos y los metadatos del recurso están disponibles para su descarga en la sección descargas. La tabla versiones enumera otras versiones del recurso que se han puesto a disposición del público y permite seguir los cambios realizados en el recurso a lo largo del tiempo.

Versiones

La siguiente tabla muestra sólo las versiones publicadas del recurso que son de acceso público.

¿Cómo referenciar?

Los usuarios deben citar este trabajo de la siguiente manera:

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

Derechos

Los usuarios deben respetar los siguientes derechos de uso:

El publicador y propietario de los derechos de este trabajo es Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. Esta obra está bajo una licencia Creative Commons de Atribución/Reconocimiento (CC-BY 4.0).

Registro GBIF

Este recurso ha sido registrado en GBIF con el siguiente UUID: 44c33d16-84bd-41d3-8e39-bed4786eca9c. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node publica este recurso y está registrado en GBIF como un publicador de datos avalado por Ocean Biodiversity Information System.

Palabras clave

Samplingevent

Contactos

Charlotte N.L. Chambers

Proveedor De Los Metadatos ●
Originador ●
Punto De Contacto

Researcher

Institute of Geography, The University of Edinburgh

Drummond Street

EH8 9XP Edinburgh

Scotland

Cobertura geográfica

Tongareva Lagoon, Cook Islands

Coordenadas límite	Latitud Mínima Longitud Mínima [-9,04, -158,01], Latitud Máxima Longitud Máxima [-8,98, -157,92]

Cobertura taxonómica

Giant clams

Especie	Trochus niloticus

Cobertura temporal

Fecha Inicial / Fecha Final	2006-05-03 / 2006-05-31

Métodos de muestreo

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 Estudio	Tongareva Lagoon, Cook Islands

Descripción de la metodología paso a paso:

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.

Referencias 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.

Metadatos adicionales

marine, harvested by iOBIS

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