A team of volunteers and staff from South Africa's Two Oceans Aquarium pulled off a mammoth rescue mission last week when a huge ocean sunfish became trapped in a dry dock at the V&A Waterfront in Cape Town. 

"The dock was draining quickly and the group had to devise a plan to get the fish, estimated to weigh at least 150kg, out of the dock before it was too late," writes the team in an update. In addition to that impressive bulk, the fish measured in at a huge 1.94 metres (over 6 feet).

The ocean sunfish (Mola mola) is one of two sunfish species that cruise Cape Town waters, but its cousin, the sharptail sunfish (Masturus lanceolatus), is only rarely seen. In the summer months, it's not uncommon for these ocean giants to stray into local harbours, and they sometimes run into trouble. "They start appearing in October/November and are often sighted right through to May/June the following year. Unfortunately they are often injured or disorientated," explains the aquarium.

Last week's rescue was a race against the clock – and it required a good dose of ingenuity and people power to hoist the supersized cargo over the dry dock's steep sides. "We also had to work fast as we couldn't risk removing the sunfish from the water for too long," says the team. 

Luckily, the Mola mola was carried safely to open water, and the team was able to collect DNA samples before releasing it back into the ocean. Such samples provide valuable information to international researchers, so Two Oceans staff make an effort to collect DNA whenever they come across sunfish in local waters.

This isn't the first time a sunfish has found itself in trouble at a local dry dock. Last year, aquarium staff came to the rescue when dockworkers spotted two fish stuck at Table Bay harbour. Another specimen stranded at a beach in nearby Camps Bay in 2014, and was pushed back out to sea. 

While last week's lucky rescuee was certainly big, the largest Mola mola specimens can reach a whopping 14 feet (4.2 metres) fin to fin, and weigh over 5,000 pounds (2.26 tonnes), making the ocean sunfish the heaviest known bony fish in the world. 

Scientists suspect size helps these animals thermoregulate in the deep sea. Molas have been clocked at depths of 2,600 feet in search of siphonophores and other prey, and their bulk means they lose heat slowly, allowing them to stay down for longer intervals. 


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