true

ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

Ngardmau Passage ISRA

46/179

Ngardmau Passage ISRA

Ngardmau Passage

Summary

Ngardmau Passage is located in Ngardmau State in Palau. The area is situated on the western barrier reef and is known locally as ‘Devilfish City’ or Iwekakou Channel. The habitat is characterised by large rocks and sandy substrates. It is influenced by the rise and fall of the tides driving water through the channels and passages. Within this area there are: threatened species and feeding areas (Reef Manta Ray Mobula alfredi).

Ngardmau Passage

Ngardmau Passage

DESCRIPTION OF HABITAT

Ngardmau Passage is located in Ngardmau State in Palau. The area is situated on the western barrier reef of Palau and is known locally as ‘Devilfish City’ or Iwekakou Channel. The habitat is characterised by large rocks and sandy substrates (Harel-Bornovski & Bornovski 2015). Reef channels and passages on the outer reefs of Palau are conduits between the ocean and lagoon, exchanging water, oxygen, plankton, and sediments (Colin 2009). The area is influenced by the rise and fall of the tides driving water through the channels and passages. Ocean water flows into the lagoon on flood tides; lagoon waters flow seaward on ebb tides (Colin 2009).

This Important Shark and Ray Area is benthic and pelagic and is delineated from surface waters (0 m) to 40 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

One Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occurs in the area. This is the Vulnerable Reef Manta Ray (Marshall et al. 2022).

CRITERION C

SUB-CRITERION C2 – FEEDING AREAS

Ngardmau Passage is an important feeding area for one ray species.

Between 2013–2024, during the months of January–May, feeding aggregations of >10 Reef Manta Rays were regularly and predictably observed by recreational divers within the area. Aggregations peaked at between 40–50 individuals in April–May (J Alpert pers. obs. 2013–2024). The largest aggregations were observed when the incoming current is strong before the new and full moons. The largest Reef Manta Ray aggregation in Palau of >70 individuals was observed within this area (Etpison & Colin 2013). The exact location of Reef Manta Rays feeding within the area changes daily depending on the currents, tides, and wind, and covers a large area making it difficult to locate and stay with the feeding Reef Manta Rays. Reef Manta Rays are seen somersaulting in dense patches of zooplankton. Within the area, they are mostly seen feeding in ‘trains’, one Reef Manta Ray closely following another (Etpison & Colin 2013). Feeding is generally in shallow waters (0-10 m), but sometimes deeper within the area (J Alpert pers. obs. 2013–2024).

Ngardmau Passage

SUBMIT A REQUEST

ISRA SPATIAL LAYER REQUEST

To make a request to download the ISRA Layer in either a GIS compatible Shapefile (.shp) or Google Earth compatible Keyhole Markup Language Zipped file (.kmz) please complete the following form. We will review your request and send the download details to you. We will endeavor to send you the requested files as soon as we can. However, please note that this is not an automated process, and before requests are responded to, they undergo internal review and authorization. As such, requests normally take 5–10 working days to process.

Should you have questions about the data or process, please do not hesitate to contact us.

    * indicates required

    Industry or sector (*)

    Under the terms and conditions of our User License Agreement , full and appropriate acknowledgement is required in any materials and publications derived from the data (and copies should be sent to the IUCN SSC Shark Specialist Group through the contact form). For any publications making substantial use of the data, the ISRA welcomes the opportunity for co-authorship, collaboration, and to comment prior to publication.


    Furthermore, we need to know whether you are a commercial or non-commercial user. Non-commercial includes scientific research, education or conservation. Commercial is defined as follows: any use by, on behalf of, or to inform or assist the activities of a commercial entity (that operates ‘for profit’) or use by a non-profit for the purposes of revenue generation

    Type of use(*):

    Please specify which layer (ex. all layers, layers within a specific Region, layers within a Jurisdiction or a single ISRA): Purpose (*):

    Please provide a description of how you intend to use the ISRA GIS Dataset. The more details you provide, the faster we can respond to your request. We may require further clarification prior to providing access. (min. 100 characters – max 1,000 characters)



    File format request (*)

    By providing your personal data, you consent to its processing as described below. The IUCN SSC Shark Specialist Group will use the information you provide on this form to send the documents you requested. You can change your mind at any time by writing to the ISRA Data Coordinator www.sharkrayareas.org/contact. All personal details provided will be treated with respect. For any information you can visit our Privacy Policy.
    Please read the User License Agreement and ISRA Layer Metadata Description

    This form uses Google reCaptcha to reduce spam. Privacy - Terms