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The ocean sunfish Mola mola: insights into distribution, abundance and behaviour in the Irish and Celtic Seas

Published online by Cambridge University Press:  25 August 2006

Jonathan D.R. Houghton
Affiliation:
Department of Biological Sciences, Institute of Environmental Sustainability, University of Wales Swansea, Singleton Park, Swansea, UK, SA2 8PP.
Thomas K. Doyle
Affiliation:
Department of Zoology, Ecology and Plant Sciences, Lee Maltings, Prospect Row, Cork, Ireland
John Davenport
Affiliation:
Department of Zoology, Ecology and Plant Sciences, Lee Maltings, Prospect Row, Cork, Ireland
Graeme C. Hays
Affiliation:
Department of Biological Sciences, Institute of Environmental Sustainability, University of Wales Swansea, Singleton Park, Swansea, UK, SA2 8PP.
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Abstract

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Here we provide baseline data on the distribution and abundance of Mola mola within the Irish and Celtic Seas, made during aerial surveys from June to October during 2003–2005. These data were considered in conjunction with concurrent observations of three potential jellyfish prey species found throughout the region: Rhizostoma octopus, Chrysaora hysoscella and Cyanea capillata. A total area of 7850 km2 was surveyed over the three years with an observed abundance of 68 sunfish giving a density of 0.98 ind/100 km2. Although modest, these findings highlight that the species is more common than once thought around Britain and Ireland and an order of magnitude greater than the other apex jellyfish predator found in the region, the leatherback turtle (Dermochelys coriacea). Furthermore, the distribution of sunfish sightings was inconsistent with the extensive aggregations of Rhizostoma octopus found throughout the study area. The modelled distributions of predator–prey co-occurrence (using data for all three jellyfish species) was less than the observed co-occurrence with the implication that neither jellyfish nor sunfish were randomly distributed but co-occurred more in the same areas than expected by chance. Finally, observed sunfish were typically small (∼1 m or less) and seen to either bask or actively swim at the surface.

Type
Research Article
Copyright
2006 Marine Biological Association of the United Kingdom