New resident or new invader? | WWF Hong Kong

New resident or new invader?

Posted 28 May 2014
If you frequently snorkel or dive in Hong Kong, you may have noticed that there is a new resident in our marine environment – one that we’re beginning to see more and more often.

This new resident is called the Sabah giant grouper. Those we often see in Hong Kong waters are relatively large fish, weighing between one and five kg, sometimes even larger! This may seem like a good thing that, after the ban on trawling in Hong Kong, fish populations are recovering in local waters. However, the appearance of the Sabah giant grouper, on the contrary, may not be a good sign at all. Why?

The Sabah giant grouper is not a native species in Hong Kong. In fact it is not a native of any places except the laboratory. Despite its name, the Sabah giant grouper is actually a hybrid of two grouper species and it is carnivorous. Some of the most common “combinations” are the giant grouper and the tiger grouper, the tiger grouper and the camouflage grouper, and the giant grouper and the coral grouper. More “combinations” can be found in the market or in the pipeline now!

So why have Sabah giant groupers suddenly appeared in our waters? One reason is the increasingly popular fish release activities in Hong Kong, either for religious or other purposes. Its relatively low price and large size make the Sabah giant grouper one of the common types of fish to be released. No wonder in these few years, we’re seeing more and more reports of Sabah giant grouper at popular dive sites. Also, recreational anglers are catching Sabah giant groupers at local fishing spots.

There are very few studies, either at the local or global level, on the impact of Sabah giant grouper on the natural marine environment. However, there has been a similar case of an exotic species impacting a local marine environment.

In 2004, a lionfish was sighted on a reef in the Bahamas, since then, there was a population explosion. The lionfish is not native to the Bahamas, it is in fact an Indo-Pacific species and it also naturally occurs in Hong Kong. But in the Bahamas, these lionfish became unwelcome residents and brought a disaster. Lionfish are like lion and are ferocious predators. A scientific study revealed that lionfish can kill three-quarters of the new recruitment of reef’s fish in just five weeks. They are now posing great threats to the native fish population in the Bahamas! Scientisits are now helping the Bahamas to try different methods to limit the impact of the lionfish, ranging from awareness raising, education, training to individuals to identify and remove lionfish from the reef, and even organizing a lionfish hunting derby!

It is too early to say if a similar disaster could happen in the Hong Kong context and become a “Sabah giant grouper disaster”. But putting further unnecessary burden to our fragile marine environment at this stage is extremely risky.

--Dr Allen To, Senior Conservation Officer, Footprint