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RESEARCH PRODUCT

Reply to LoganDodge: 'stable isotopes challenge the perception of ocean sunfish Mola mola as obligate jellyfish predators'.

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Syvaranta et al. (2012) recently provided stable-isotope data from eight small-bodied ocean sunfish Mola mola (L. 1758) captured from the Italian fishing port of Camogli on the Ligurian coast. Representative data were also given for members of pelagic and neritic–coastal food webs. The level of 13C and 15N enrichment shown by M. mola relative to their putative obligate diet of gelatinous zooplankton (gelata) (based on the locally dominant Pelagia noctiluca and literature data) was used to question their obligate consumption of such prey. Furthermore, the M. mola were isotopically more similar to neritic rather than pelagic fishes captured locally, prompting the suggestion that juvenile M. mola may not be obligate predators of gelata, but functionally, they might be part of the neritic and coastal food web. In their comment, Logan & Dodge (2013) have produced a detailed critical analysis of Syvaranta et al.’s (2012) approach, results and conclusions. They are thanked for furthering a much needed debate regarding M. mola. Here, a response is made to their comments with the provision of additional quantitative analysis that strengthen the original conclusions. Logan & Dodge (2013) provide an excellent summary of isotopic variation in gelata across different marine areas worldwide. Although their summary of data from the north-east Pacific and north-west Atlantic Oceans are of great value to workers interested in gelatinous zooplankton, their relevance to Mediterranean M. mola is limited and they are not considered further here. As Logan & Dodge (2013) suggest, however, the M. mola sampled by Syvaranta et al. (2012) may have migrated to the Mediterranean Sea from the north-east Atlantic Ocean prior to capture; therefore, their summaries from the Mediterranean Sea (where the M. mola were captured) and