Ocean sunfish enjoying a bask!
Often seen basking at the surface, there has been a long held view that ocean sunfish are rare, inactive drifters feeding solely on gelatinous plankton, however recent studies have shown these notions to be far from accurate. We now have have evidence of ocean sunfish travelling distances of nearly 27 km a day, diving to great depths up to 844m and consuming a mixed diet. All of these little pieces of information then combine to create a detailed picture of an oceanic migrant that may have a much more important role in ecosystem functioning than previously known.
Of course, sunfish diving behaviour is really difficult to observe in the wild and we are often dependent on tagging studies for this information. However, as fish tags are really expensive and there is always under the risk that your tag will be lost in the open ocean, so we have to make assumptions on what the population is likely to do based on a relatively small number of tagged fish. But how else can we find out what sunfish are doing deep down in the dark ocean depths?
Photo collage of incidental sunfish sightings from our paper.
Well luckily for us, marine scientists are not the only people interested in the deep sea! Engineers from the oil and gas industry are also very keen to put cameras in the deep ocean to check up on their oil rigs and pipelines, and they often film marine creatures who come to investigate the lights on their cameras.
Sightings of all these creatures are then uploaded by the oil and gas companies to an open access website for scientists (and anyone else!) to study and enjoy. This data sharing is called the SERPENT project (http://www.serpentproject.com) and has provided some amazing sunfish sightings
for me in the deep sea! I have also collected a few other accidental sightings recorded by oceanographer’s submarines and survey cameras and along with my collaborators, we have had a paper on the subject accepted into scientific journal The Journal of Fish Biology! (http://onlinelibrary.wiley.com/doi/10.1111/jfb.2015.87.issue-4/issuetoc)
We have 13 additional sightings of ocean sunfish at depths up to 550m, with a new depth record for species Mola ramsayi, previously only seen at 85m, now recorded at 483m! We are able to use these new sightings as further evidence of ocean sunfish depth use, potentially hunting prey using their large sensitive eyes and in once case we see a sunfish actually scratching itself on the oil rig! It is clear that these fish are not just passive surface drifters but actually distributed throughout the water column and this serves to highlight the increasing realisation that the sunfishes are far more complex in their ecology than previously thought!
P.S. If you would like a copy of the recent paper please let me know 🙂 and as always if you see a dead sunfish please contact me! Email: firstname.lastname@example.org or tweet @SunfishResearch