We are pleased to report that the ocean sunfishes that came into our care over the holiday season, after becoming trapped in the nearby marina and rehabilitated at the Two Oceans Aquarium, have been successfully released! These beautiful ocean giants now have a second chance at an ocean life in the deep waters beyond Robben Island.
After a wonderful holiday season, the larger sunfish was released back into the wild on the far side of Robben Island on 16 January. After spending almost two months in the Predator Exhibit, the sunfish had completed its medical treatments and had grown in size significantly since arriving here. We could see from its behaviour that it was growing restless - it was time for its ocean journey to continue.
With the help of our friends at Animal Ocean, our team took this Mola mola out beyond Robben Island to 60m deep water. We spotted several more small sunfish in the area, as well as many crystal jellies (which adult sunfish eat) - so we decided that this release spot would be suitable. Good luck little giant!
The smaller of the two sunfish rescued from the V&A Waterfront harbour by the Two Oceans Aquarium on 20 November was safely released back into the ocean just a few days later, on 23 November 2018.
The sunfish's behaviour was closely monitored for three days, and the Two Oceans Aquarium's curatorial team was satisfied that the time was right for this sunfish to be released. The larger of the two sunfish was found to have some injuries, including a missing pectoral fin, obtained while in the wild, so we decided to keep it a while longer to monitor its mobility.
With the approach of the summer heat, Cape Town regularly sees visits from ocean sunfish (Mola mola) in our shallow waters. The morning of 20 November 2018 was no exception - with several trapped sunfish observed in the marina basin near to the Two Oceans Aquarium. Three sunfish had been spotted in the basin the previous day, and once it became clear that they were unable to swim out of the harbour themselves, possibly due to disorientation caused by big ships in the harbour, we decided to head out and collect these animals.
We are pleased to say that we were able to safely collect two of the ocean sunfish and bring them swiftly to the Aquarium for veterinary assessment.
Both sunfish were completely covered in a large variety of parasites, and these were all removed, by hand, for study - the Aquarium is deeply involved with international studies of Mola mola parasitology.
Where are the sunfish now?
The first ocean sunfish which was collected was very small, although "small" is a relative term when talking about a fish that can grow to over a ton. In this case though, we can safely say that this sunfish is tiny - in fact, it is the smallest sunfish we've ever encountered at the Aquarium.
The second sunfish was quite a bit larger, although still small by sunfish standards, and was only slightly smaller than Holy Moly who was with us during the festive season last year. This sunfish was in a somewhat worse condition than the smaller one. It had clear signs of past injuries, a much larger variety of parasites, and it appeared that the parasites had caused quite a bad infection in the sunfish's tail.
The small sunfish was moved into the Predator Exhibit, where it could be seen swimming in a temporary enclosure at the exhibit's back window. It was being kept in this enclosure to allow it to have a chance to rehydrate and recover after its most recent stressful situation, and to make it easier for us to monitor its health, and to allow the other Predator Exhibit inhabitants to get comfortable with this newcomer. Interestingly - this is the same enclosure that was used to house Holy Moly, the sunfish that was rescued in December 2017.
The larger sunfish, which appeared to have more severe ailments, was kept in a large quarantine pool so that its health could be more easily observed.
At the time of writing, our team were still out in the water looking for the third sunfish that had reportedly been sighted in the harbour, but fortunately, this one was able to make its own way back into open water.
Moving into an isolation enclosure
Some news that excited Aquarium visitors: After the small sunfish was released on 23 November, members of the public thought they had missed the chance to see this ocean oddity. Fortunately for them, the large sunfish that was still recovering at the Aquarium was given the chance to freely roam the Predator Exhibit in early December.
As mentioned before, the injuries that it had when rescued included a missing pectoral fin and an infection. It appeared to be handling these injuries well - but we wanted to be sure that it's mobility and health were not compromised before releasing it.
The largest bony fish in the world
Ocean sunfish are the heaviest known bony fish in the world - easily growing over a ton. They are also known for being covered in skin parasites. To counter this, sunfish employ a number of tactics: cleaner wrasse and other reef fish often help out, and by basking on its side at the surface, sunfish allow seabirds to feed on parasites.
Our work with sunfish
The Two Oceans Aquarium assists international researchers of sunfish with the collection of DNA samples when Aquarium staff members come across a sunfish in Cape Town waters.
We also regularly help remove trapped sunfish from dry docks in the V&A Waterfront precinct - like the one we sent “flying”.
More interesting facts about these gentle giants
- Sunfish are so called because of their habit of drifting at the surface as if basking in the sun.
- Sunfish do not have tails as other fishes do – the caudal (tail) fin has been replaced by a rudder-like structure.
- The ocean sunfish has a rounded, wavy rudder.
- All sunfish have small mouths and the teeth are fused together in each jaw, forming a beak like that of a parrot. The beak is internal and hidden from view.
- Sunfish feed on jellies. It is remarkable that an animal that grows to such a large size subsists on a diet with very little nutritional value.
- Sunfish are not considered edible as they consist mainly of cartilage and gristle and their flesh is soft and insipid.
- They are the most fertile of all fishes, producing up to 300 million tiny eggs.
- The name “mola” is derived from the Latin word for millstone because of their similar shape.
One of a sunfish's most striking features is its big, wide eyes. Scientists believe that larger eyes could help sunfish identify prey over greater distances, and help them take advantage of lower light conditions at greater depths, so enabling sunfish to dive deeper to search for prey such as siphonophores (class of marine animals belonging to the phylum Cnidaria, which also includes jellies), according to Sunfish Research.