Greetings all, on behalf of our co-authors, we are pleased to share our new 
open access publication:

Habitat modeling of Irrawaddy dolphins (Orcaella brevirostris) in
the Eastern Gulf of Thailand

DOI: 10.1002/ece3.6023

Justine Jackson-Ricketts1, Chalatip Junchompoo2,  Ellen M. Hines3,  Elliot L. 
Hazen4,
Louisa S. Ponnampalam5,  Anoukchika Ilangakoon6,  Somchai Monanunsap7

1Department of Ecology and Evolutionary
Biology, University of California Santa Cruz,
Santa Cruz, California
2Department of Marine and Coastal
Resources, Marine and Coastal Resources
Research and Development Center, The
Eastern Gulf of Thailand, Rayong, Thailand
3Estuary & Ocean Science Center, San
Francisco State University, Tiburon,
California
4NOAA Southwest Fisheries Science
Center, Environmental Research Division/
Department of Ecology and Evolutionary
Biology, University of California Santa Cruz,
Monterey, California
5The MareCet Research Organization, Shah
Alam, Malaysia
6Maharagama, Sri Lanka
7Department of Marine and Coastal
Resources, Southern Marine and Coastal
Resources Research Center, Songkhla, Thailand

Abstract
Aim: The Irrawaddy dolphin (Orcaella brevirostris) is an endangered cetacean 
found
throughout Southeast Asia. The main threat to this species is human 
encroachment,
led by entanglement in fishing gear. Information on this data-poor species’ 
ecology
and habitat use is needed to effectively inform spatial management.
Location: We investigated the habitat of a previously unstudied group of 
Irrawaddy
dolphins in the eastern Gulf of Thailand, between the villages of Laem Klat and
Khlong Yai, in Trat Province. This location is important as government groups 
plan to
establish a marine protected area.
Methods: We carried out boat-based visual line transect surveys with concurrent
oceanographic measurements and used hurdle models to evaluate this species’
patterns of habitat use in this area.
Results: Depth most strongly predicted dolphin presence, while temperature was a
strong predictor of group size. The highest probability of dolphin presence 
occurred
at around 10.0 m with an optimal depth range of 7.50 to 13.05 m. The greatest 
number
of dolphins was predicted at 24.93°C with an optimal range between 24.93 and 
25.31°C.
Dolphins are most likely to occur in two primary locations, one large region in 
the center
of the study area (11o54′18′′N to 11o59′23′′N) and a smaller region in the south
(11o47′28′′N to 11o49′59′′N). Protections for this population will likely have 
the greatest
chance of success in these two areas.
Main Conclusions: The results of this work can inform management strategies 
within
the immediate study area by highlighting areas of high habitat use that should 
be
considered for marine spatial planning measures, such as the creation of marine
protected areas. Species distribution models for this species in Thailand can 
also assist
conservation planning in other parts of the species’ range by expanding our 
understanding
of habitat preferences.

Ellen Hines, PhD
Associate Director and Professor of Geography & Environment
Estuary and Ocean Science Center
San Francisco State University
3150 Paradise Dr. Tiburon, CA 94920
415 338 3512, [email protected]<mailto:[email protected]>
http://eoscenter.sfsu.edu/content/ellen-hines

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