Invasion of the Hybrid Grouper

By Marla Lise

Marla is an ocean lover with a passion for marine conservation

Hybrid groupers are becoming a common sight in Singapore - outside of our restaurants, anglers catch them along our coastlines and offshore.

Where did they come from?

Groupers are good eating. Unfortunately, because of their popularity, suppliers had to do something drastic in order to meet the demand. So, they chose two grouper species, the male Giant Grouper (Epinephelus lanceolatus) - also known as the Queensland grouper and the female Tiger or Brown Marbled Grouper (Epinephelus fuscoguttatus) and with them, produced the fast-growing and robust hybrid Groupers, or Dragon Tiger Groupers, that are slowly invading the oceans.

What’s the problem?

Although breeding hybrid Groupers may solve the problem of high demand from fish connoisseurs, they cause a much larger problem that we might not even notice until it is too late.

Above: Catch report by Davy Ong - fishing trip in Singapore in 2018.

Their long term effects on the ecosystem are still unknown. With their voracious appetites, they compete with native fish for food. There are also risks of them breeding with other species outside of captivity which may cause more strains of hybrid fish.

Above: Juvenile hybrid grouper, approx 10cm long, caught in Singapore. Is this an escapee or are they breeding in our local waters?

Groupers are already a vulnerable species due to their solitary nature and because they are easy to catch. Disturbances to their habitats by invasive species therefore could prove quite detrimental to native species.

Above: Catch report from Pioneer tackle's SAF Yacht Club fishing competition in 2019. Of the 14 fish caught, 10 of them (71%) are hybrid groupers

While many of the fish farms producing hybrid groupers are located in the Johor Straits North of Singapore, the invasive species have also been hooked up in the Southern waters.

Above: Hybrid grouper caught at Sentosa in 2018. Photo submitted by My Fishing Frenzy Academy

More research is needed to understand the impact for the future of the native ecosystems in Singapore based on escaped fish affecting local populations. Prevention systems must also be put in place to stop fish from escaping in the first place.

Identification

Groupers are of the Serranidae Family and there are about 449 recorded species of them, found in tropical and temperate waters. Grown male individuals can reach lengths of up to 3m long.

Hybrid Grouper, or Dragon Tiger Grouper

Invasive, non-native

Dark and mottled with a lighter shade of brown and white spots and a rounder tail

Photo: David Koh

These are not to be confused with other species of groupers that are native to Singapore:

Orange-spotted Grouper

Native

Most commonly caught grouper in Singapore

Numerous small brownish orange or reddish brown spots on head, body, and median fins; body with 5 faint, irregular, oblique, dark bars

Photo: David Koh

Giant Grouper or the Queensland grouper

Native

They are dark grey to dark brown with white spots and blotches. They have characteristic small black dots which are predominantly on the pectoral, dorsal and tail fins.

Photo: Capt Jimmy

Brown Marbled Grouper

Native

Pale yellowish brown, with 5 vertical series of dark brown blotches that are very irregular in outline; head, body, and fins covered with close-set small brown spots

Photo: Capt Jimmy

What now?

Marine Stewards is collecting data to understand the extent of the hybrid grouper situation. Where they are, how many are being caught etc - so that we can take action with the community and with the relevant agencies.

As a first step we are compiling catch report data, and we need input from the community - you!

1. Send us your catch reports

Any Hybrid Groupers caught, email to hello@marinestewards.org with the below info:

1. Photo

2. Date (1 Jan 2018 onwards, 2 years data)

3. Location / marina

4. Captain & boat name if applicable (so we know who we can work with if needed)

5. Number of anglers if more than one

2. Keep all hybrid groupers

If you hook up a hybrid grouper, do not release it back. Take it home to cook, or give it to your kaki or neighbour. It is a good-eating fish!

In the mean time, join our Facebook group to follow discussions.

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