Image by Natasha Phillips ©
Species description and status: The ocean sunfish (Mola mola) is one of the world’s largest bony fishes reaching over 3 m in length and weighing up to 2.3 tonnes (Roach, 2003; Rowan, 2006). Listed as Vulnerable to extinction globally by the IUCN since 2011, but Data Deficient across Europe (Jing et al., 2015), this species requires significant further research to fill ongoing knowledge gaps that are currently hindering sustainable management and conservation. The ocean sunfish is believed to be pan-globally distributed (Phillips et al., 2017), however recent genetics work has shown there to be cryptic speciation within the Molidae family (Nyegaard et al., 2017; Sawai et al., 2017) and so further research is required to assess species-specific distribution patterns. Although long-thought to be a passive drifter of little ecological importance, recent research suggests these fish can travel long distances against prevailing currents (Pope et al., 2010; Nakamura & Sato, 2014), regularly dive into the deep ocean (Sims et al., 2008; Dewar et al., 2010; Phillips et al., 2015) and their varied diet (Syväranta et al., 2012; Nakamura et al., 2015; Phillips et al., 2020) means they may play an important role in local ecosystem functioning. Studies to date into ocean sunfish movements have revealed long distance movements and links with frontal systems (e.g. Sims et al., 2008; Sims & Southall, 2002; Cartamil & Lowe, 2004; Dewar et al., 2010; Sousa et al., 2016), however further studies are required to extend our understanding of sunfish distribution across broader scales for international conservation management.
Knowledge gaps: To date the ocean sunfish is not included in any management plans or protective measures owing to large knowledge gaps in the species life history. The sunfish is targeted for human consumption across Asia, and they are frequently reported as bycatch across the world, with estimates suggesting this removes hundreds of thousands of individuals each year. Preventing the bycatch of these fish is extremely challenging as ocean sunfish distribution and movement patterns are not well understood, particularly in European waters. Collection of sunfish distribution data needs urgent prioritising to help to reduce bycatch, aid protective measures and boost their potential as a keystone species for eco-tourism ventures, as large, harmless, charismatic fishes that are highly tolerant of divers and boats. As such, increased efforts to understand sunfish movement patterns are highly recommended as this information is vital for the creation of sustainable management measures, including assessment of population connectivity and potential use of migratory corridors. This information can then be used to assess connectivity across international jurisdictions, define critical areas for the species and help fishermen avoid bycatch.
Regions of interest: The North Atlantic Ocean, Mediterranean Sea, the Irish Sea
Telemetry tools: Pop-up satellite archival tags (PSAT) are highly valuable tools to assess fish spatial movements and alongside long-term use of acoustic transmitters and receivers, a telemetry based approach would significantly boost the current understanding of sunfish distribution and movement patterns. PIT-tags would also be valuable for recording survival rates from catch and release fishing (where practised) and data storage tags can offer valuable insights for conservation management plans.
Benefits within ETN: The ETN network offers a valuable means to characterise ocean sunfish movement patterns and behaviour which could provide vital data to reduce fisheries bycatch and help design protective measures for this vulnerable species. Through this extensive network, an opportunity has arisen to understand a broad ranging marine species that currently has no protective legislation, and whose current unpredictability of movement causes huge bycatch issues for fisheries. Since this species offers high value to coastal communities through eco-tourism industries, by understanding their movement patterns it may be possible to assist decision makers and conservation managers to adopt specific measures to protect this vulnerable species, reduce fishing bycatch and boost profitability for local tourism groups.
Contacts: Natasha Phillips
Cartamil, D.P. & Lowe, C.G. (2004) Diel movement patterns of ocean sunfish Mola mola off southern California. Marine Ecology Progress Series, 266, 245–253.
Dewar, H., Thys, T., Teo, S.L.H., Farwell, C., O’Sullivan, J., Tobayama, T., Soichi, M., Nakatsubo, T., Kondo, Y., Okada, Y., Lindsay, D.J., Hays, G.C., Walli, A., Weng, K., Streelman, J.T., & Karl, S.A. (2010) Satellite tracking the world’s largest jelly predator, the ocean sunfish, Mola mola, in the Western Pacific. Journal of Experimental Marine Biology and Ecology, 393, 32–42.
Jing, L., Zapfe, G., Shao, K.-T., Leis, J.L., Matsuura, K., Hardy, G., Liu, M., Robertson, R. & Tyler, J. (2015) Available at: www.iucnredlist.org.
Nakamura, I., Goto, Y., & Sato, K. (2015) Ocean sunfish rewarm at the surface after deep excursions to forage for siphonophores. Journal of Animal Ecology, 84, 590–603.
Nakamura, I. & Sato, K. (2014) Ontogenetic shift in foraging habit of ocean sunfish Mola mola from dietary and behavioral studies. Marine Biology, 161, 1263–1273.
Nyegaard, M., Sawai, E., Gemmell, N., Gillum, J., Loneragan, N.R., Yamanoue, Y., & Stewart, A.L. (2017) Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition. Zoological Journal of the Linnean Society, 182, 1–28.
Phillips, N.D., Harrod, C., Gates, A.R., Thys, T.M., & Houghton, J.D.R. (2015) Seeking the sun in deep, dark places: Mesopelagic sightings of ocean sunfishes (Molidae). Journal of Fish Biology, 87, 1118–1126.
Phillips, N.D., Reid, N., Thys, T., Harrod, C., Payne, N., Morgan, C., White, H.J., Porter, S., & Houghton, J.D.R. (2017) Applying species distribution modelling to a data poor, pelagic fish complex: the ocean sunfishes. Journal of Biogeography, 44, 2176–2187.
Phillips, N.D., Smith, E.A.E., Newsome, S.D., Houghton, J.D.R., Carson, C.D., Mangel, J.C., Eagling, L.E., Kubicek, L., & Harrod, C. (2020) Bulk tissue and amino acid stable isotope analyses reveal global ontogenetic patterns in ocean sunfish trophic ecology and habitat use. Marine Ecology Progress Series, 633, 127–140.
Pope, E.C., Hays, G.C., Thys, T.M., Doyle, T.K., Sims, D.W., Queiroz, N., Hobson, V.J., Kubicek, L., & Houghton, J.D.R. (2010) The biology and ecology of the ocean sunfish Mola mola: A review of current knowledge and future research perspectives. Reviews in Fish Biology and Fisheries, 20, 471–487.
Roach, J. (2003) World’s Heaviest Bony Fish Discovered? National Geographic News.
Rowan, J. (2006) Tropical sunfish visitor as big as a car. The New Zealand Herald APN News & Media.
Sawai, E., Yamanoue, Y., Nyegaard, M., & Sakai, Y. (2017) Redescription of the bump-head sunfish Mola alexandrini (Ranzani 1839), senior synonym of Mola ramsayi (Giglioli 1883), with designation of a neotype for Mola mola (Linnaeus 1758) (Tetraodontiformes: Molidae). Ichthyological Research, 65, 142–160.
Sims, D.W., Queiroz, N., Doyle, T.K., Houghton, J.D.R., & Hays, G.C. (2008) Satellite tracking of the World’s largest bony fish, the ocean sunfish (Mola mola L.) in the North East Atlantic. Journal of Experimental Marine Biology and Ecology, 370, 127–133.
Sims, D.W., Queiroz, N., Humphries, N.E., Lima, F.P., & Hays, G.C. Long-term GPS tracking of ocean sunfish Mola mola offers a new direction in fish monitoring. PLoS ONE, 4, 1–6.
Sims, D.W. & Southall, E.J. (2002) Occurrence of ocean sunfish, Mola mola, near fronts in the western English Channel. J. Mar. Biol. Ass. U.K, 82, 927–928.
Sousa, L.L., Queiroz, N., Mucientes, G., Humphries, N.E., & Sims, D.W. (2016) Environmental influence on the seasonal movements of satellite-tracked ocean sunfish Mola mola in the north-east Atlantic. Animal Biotelemetry, 4, 7.
Syväranta, J., Harrod, C., Kubicek, L., Cappanera, V., & Houghton, J.D.R. (2012) Stable isotopes challenge the perception of ocean sunfish Mola mola as obligate jellyfish predators. Journal of Fish Biology, 80, 225–31.