Assessment of Key Dugong and Turtle Seagrass Resources in North-west Torres Strait

Carter, A.B, and Rasheed, M.A. (2016) Assessment of Key Dugong and Turtle Seagrass Resources in North-west Torres Strait. Report. Reef and Rainforest Research Centre, Cairns, QLD, Australia.

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Abstract

Seagrasses are one of the most productive marine habitats on earth that provide food for herbivores like dugongs (Dugong dugon) and green sea turtles (Chelonia mydas). Torres Strait contains extensive seagrass meadows, the largest dugong population in the world, and a globally significant population of green turtles. Assessing and managing seagrass resources in Torres Strait requires adequate baseline information. North-west Torres Strait was identified in a 2014 review as an important hunting and fishing ground for Torres Strait Islanders with large dugong and turtle populations, but where seagrass data was lacking.

The project aim was to provide information on intertidal and subtidal seagrass in north-west Torres Strait detailing seagrass distribution, biomass, species composition, and other benthic characteristics (algae, macro-invertebrates).

Boat and helicopter surveys were conducted November 2015 to January 2016. Seagrass information recorded included presence/absence, percent cover, above ground biomass, species composition and diversity. Other benthic information included percent cover of algae (by functional group) and macro-invertebrates. Boat-based surveys were conducted in collaboration with TSRA LSMU Rangers from Boigu Island and Saibai Island.

North-west Torres Strait contains extensive seagrass habitat. Seagrass was present at 43% of the 853 sites surveyed. Seagrass area mapped was 60 263 ha across 34 meadows. Ten seagrass species from three families were identified. The most dominant species in terms of contribution to mean biomass was T. hemprichii (35%); H. uninervis was the most commonly occurring species. Extensive dugong feeding trails (DFTs) were present in intertidal meadows along the Papua New Guinea shoreline and around Boigu Island. Coral communities were the dominant form of benthic macro-invertebrates. Extensive algae habitat was throughout the region.

Subtidal seagrass meadows were extensive in the area bounded by Deliverance, Turnagain and Boigu Islands, but sparse elsewhere, likely due to strong currents south of Deliverance Island and poor underwater visibility from suspended sediments close to Papua New Guinea. The presence of dugong feeding trails in intertidal meadows and frequent turtle and dugong sightings during the surveys identifies the region as ideal foraging habitat. Subtidal meadow distribution mapped in this study overlaps spatially with very high dugong and turtle density distributions recorded during aerial surveys.

Effective management and planning requires current, spatially relevant seagrass information at the scale of individual communities’ sea country to inform community-based Turtle and Dugong Management Plans and will require cooperation with adjacent Papua New Guinea coastal communities. Recommendations include: (1) Establish baseline seagrass information in high-very high dugong density areas between Turnagain and Gabba Islands, Orman Reefs and the eastern boundary of the Dugong Sanctuary; (2) Establish a seagrass long-term monitoring program in regions of high-very high dugong density; (3) Continue collaboration with TSRA LSMU Rangers for seagrass surveys and monitoring.

Item ID: 70850
Item Type: Report (Report)
ISBN: 978-1-925088-88-5
Keywords: seagrass, Torres Strait, habitat survey, benthic
Copyright Information: © TropWATER, James Cook University, 2016. Creative Commons Attribution. Assessment of Key Dugong and Turtle Seagrass Resources in North-west Torres Strait is licensed by the James Cook University for use under a Creative Commons Attribution 4.0 Australia licence. For licence conditions see: https://creativecommons.org/licenses/by/4.0/
Funders: National Environmental Science Program (NESP) Tropical Water Quality (TWQ) Hub, Torres Strait Regional Authority (TSRA)
Projects and Grants: NESP 3.5
Research Data: https://eatlas.org.au/data/uuid/034ce816-0777-4bbd-aefc-8b73bd540245
Date Deposited: 23 Nov 2021 01:00
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 100%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180501 Assessment and management of benthic marine ecosystems @ 100%
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