Trends in sightings and environmental influences on a coastal aggregation of manta rays and whale sharks

Rohner, C. A., Pierce, S. J., Marshall, A. D., Weeks, S. J., Bennett, M. B. and Richardson, A. J. (2013) Trends in sightings and environmental influences on a coastal aggregation of manta rays and whale sharks. Marine Ecology Progress Series, 482 153-168. doi:10.3354/meps10290


Author Rohner, C. A.
Pierce, S. J.
Marshall, A. D.
Weeks, S. J.
Bennett, M. B.
Richardson, A. J.
Title Trends in sightings and environmental influences on a coastal aggregation of manta rays and whale sharks
Journal name Marine Ecology Progress Series   Check publisher's open access policy
ISSN 0171-8630
1616-1599
Publication date 2013-05-22
Year available 2013
Sub-type Article (original research)
DOI 10.3354/meps10290
Open Access Status DOI
Volume 482
Start page 153
End page 168
Total pages 16
Place of publication Oldendorf, Germany
Publisher Inter-Research
Language eng
Formatted abstract
Sightings of planktivorous elasmobranchs at their coastal aggregation sites are often linked to biological, environmental and temporal variables. Many large planktivorous elasmobranchs are also globally threatened species, so it is necessary to try and separate population trends from environmentally driven, short-term fluctuations. We investigated the influence of environmental variables on sightings of 3 species of planktivorous elasmobranchs off Praia do Tofo, Mozambique: the reef manta ray Manta alfredi, giant manta ray M. birostris and whale shark Rhincodon typus. We used 8- (2003 to 2011) and 6-yr (2005 to 2011) logbook data for manta rays and whale sharks, respectively, and constructed a generalised linear model with animal sightings as the response. Predictors included temporal (year, month, time of day), biological (plankton categories), oceanographic (water temperature, time from high tide, current direction and strength and wave height) and celestial (moon illumination) indices. These predictors best fitted reef manta ray sightings, a coastal species with high residency, but less so for the wider-ranging giant manta rays and whale sharks. We found a significant decline in the standardised sightings time series for the reef manta ray (88%) and whale shark (79%), but not for the giant manta ray.
Keyword GLM
Generalised linear model
Decline
Population trend
Seasonality
Environmental variability
Manta alfredi
Manta birostris
Rhincodon typus
North pacific-ocean
Remote-sensing data
Worlds largest fish
Rhincodon-typus
Ningaloo Reef
Western-australia
Satellite tracking
Mozambique Channel
Indian-ocean
Cetorhinus-maximus
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Online publication date: May 22, 2013

 
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