Sai Kung Sharks Story a Bit Fishy

As reported by Coconuts Hong Kong (November 12, 2014) in blurb headlined “Pair of meter-long sharks spotted in Sai Kung” , HK resident Adri Blumberg spotted what seemed to be a shark in Sheung Sze Wan, Sai Kung on the morning of the 12th November:
“two sharks (or shark-like creatures) have been seen in shallow waters near a beach over the last few days. The sharks, thought to be of the same species, are reported to be about a meter long with blue dorsal fins and black and white stripes.”

Enthusiastic as all tabloids are for a attention-grabbing headline, but also trying to appear as socially responsible, Coconuts goes on to say: “It’s actually a great sign that sharks are back in Hong Kong waters. If there are sharks, there are fish. And if there are fish, it means our seas are doing okay!
Scientists estimate that 100 million sharks are killed by humans every year, and Hong Kong is the world’s biggest trade hub for shark’s fin. If anyone should be scared – it’s the sharks!”

Here is the thing: it’s not sharks, it’s most likely mackerel…
How can this be?
Have a close (zoom in) look at Adri Blumberg’s pictures.

IMG_7852.JPG
Image: Adri Blumberg (Facebook)

Notice the shiny bluish color on the caudal (tail fin). Sharks have sandpaper like skin made up of tiny denticles (horns) that don’t normally shine, let alone iridescent blue. Bony fish with scales however have shiny skin often as in the case of coral reef fish in bright colors.

IMG_7853.JPG
Image: Adri Blumberg (Facebook)

The other thing is the strongly curved dorsal fin that shows hints of Rays and the sickle-shaped upper lobe of the caudal fin. Both are not seen in sharks or only rarely at least.

IMG_7854.JPG
Image: Adri Blumberg (Facebook)

And lastly there a close look shows dark stripes faintly recognisable on the back in front of the dorsal fin. Faint dark stripes point towards a tiger shark, but tigers are very bulky fish and have chunky straight dorsal and caudal fins.

The pictures look a lot like a fish from the Scombridae family that includes mackerel, though. One species recorded from HK is Narrowed-barred Spanish mackerel (Scomberomorus commerson), which commonly grows to 1.2m. I will not claim authority as an ichthyologist (fish biologist) but i am quite sure this is not a shark and very likely a mackerel or close relative.

What’s that? You don’t believe mackerel can be big enough to confuse with sharks? Check out this angling sites photos of the Chinese seerfish (Scomberomorus sinensis), a species of mackerel known from China, Japan and Korea.

Here are a few bad (but rights-free) Spanish Mackerel pics cropped to comparable proportions. What do you think?

 

1024px-Narrow-barred_Spanish_Mackerel-ed King_Mackerel-ed Spanish_Mackerel-ed

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hkmarinelife

I am a ex-marine biologist now working for a regular job, but I am still passionate about marine biology and oceanography. I studied Marine Science and completed a PhD in deep-sea ecology and biodiversity. I fell in love with HK's rich marine environment when I was a child. This blog is my collection of interesting facts, news and articles that celebrate and educate on HK's diverse marine environment.

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