Let foodies deal with invasive species, this country has done it

= "Let foodies solve the problem of invasive species" is mostly just a joke. However, in Tunisia , a remote North African country, locals have actually turned invasive species into food and created a lot of income.

Tunisia is located in North Africa, close to the Mediterranean Sea in the northeast. Blue crabs native to the west coast of the Atlantic Ocean invaded the Mediterranean Sea with ships｜Pixabay

The unfortunate invasive species that was eaten was the blue crab .

Blue crabs invade, help the fishermen

"Half is sea, half is fire" is the most appropriate sentence to describe Tunisia's geographical environment.

Tunisia's southern part is an inverted triangle, like a wedge inserted into the Sahara Desert; the northeastern part faces the Mediterranean Sea, with beautiful scenery and dense population. The coastal areas here have a unique traditional fishing technique called Charfia.

Every year at the beginning of autumn, the whole family of the locals will go out to set up the Sharfia trap. Women and children collect a lot of palm leaves and remove the thorns on them. Then the men row boats to the mudflats and insert the palm leaves into the mud to form a "maze". At the end, they set up fishing nets and fish baskets. When the tide rises, the fish will swim into the trap along the sea water and cannot escape.

Charphia fish trap made of palm leaves | Farès Chtioui / Institut National du Patrimoine, Tunisie, 2019

The Sharfia fishing method is very environmentally friendly . It does not damage the mudflats like bottom trawling does, and traps are only set from the beginning of autumn to June of the following year, leaving a closed fishing season for fish to reproduce. This technique has been passed down from generation to generation in the local area, and many fishermen make a living from it.

However, in 2014, fishermen encountered a headache: the fishing nets were often torn into pieces, and the fish inside were also gnawed . The culprit was in the fishing nets, waving its claws and teeth, and looking aggressive - that is the blue crab.

Blue Crab｜The Children's Museum of Indianapolis

Blue crabs (Callinectes sapidus) are native to the Atlantic Ocean from the United States to Argentina. They spread to various seas along ships throughout the 20th century. In the coastal areas of Tunisia, blue crabs have been infested since 2014.

In the worst-hit Gulf of Gabes, blue crabs make up more than 70 percent of the catch at peak times , sometimes mixed with blue swimming crabs (Portunus segnis), which fishermen hate and call “terrorists.”

It is edible and delicious, and is sold to foreigners.

Foodies must be getting anxious after reading this. As you can tell from its appearance, the carapace of the blue crab is in the shape of a shuttle with pointed ends. It belongs to the family of swimming crabs and is very good for steaming, stir-frying, and cooking porridge. In fact, the specific epithet "sapidus" in the scientific name of the blue crab comes from "savory", so it is also called the delicious swimming crab and the delicious blue crab.

There are many delicious species of swimming crabs | Pexels

However, in Tunisia, crabs are not on the traditional menu of locals , and people have no idea what to do with them. If you never knew that crabs can be eaten, would you want to try them when you see them? Most likely not. Crabs seem a bit intimidating, so we use the term "first person to eat crabs" to describe bold adventurers.

However, the FAO and the Tunisian government soon realized that blue crabs were popular in the international market.

With the support of FAO, the local government has trained fishermen to make fishing cages , in which they put fish heads and viscera discarded by seafood processing plants to lure blue crabs into the trap. At the same time, they have also built a processing plant to freeze or boil the freshly caught blue crabs, and then export them overseas after simple processing.

Processing blue crabs｜Aida Delpuech

With the improvement of infrastructure, Tunisia began to export blue crabs in large quantities , which are very popular in South Korea, Italy, Spain and other countries. In 2021, Tunisia exported 7,600 tons of blue crabs throughout the year, worth 75.6 million dinars (about 174 million yuan). Some local restaurants have also followed this trend and started to make delicious dishes with blue crabs.

Blue crab: from invasive species to high-value export commodity | Valerio Crespi / FAO

Blue crabs are proliferating as climate warms

The blue crab export industry can both control the number of blue crabs and generate income for local people, which is really killing two birds with one stone - but don't forget that this is a very special case. "Let foodies solve invasive species" is not feasible most of the time . Many invasive species are not delicious and are not even suitable for feed.

Water hyacinth was first introduced to China as animal feed, but people found that even pigs would not eat the plant, and did not treat it. Soon, water hyacinth spread in the waters of southern my country, encroaching on the growth space of native plants｜Ted Center

The spread of blue crabs to Tunisian waters is also closely related to climate change . Blue crabs are native to tropical and subtropical waters and are naturally adapted to warm environments. As global sea temperatures rise, previously cooler waters will become more suitable for blue crabs. Compared with the five oceans, the smaller Mediterranean Sea is warming faster.

Like blue crabs, lionfish and bluefin bream, which originally belonged to tropical waters, are also invading the Mediterranean. But their stories are not as beautiful as those of blue crabs - wherever they go, some native species become prey, some are deprived of their living space, and some die because they cannot withstand the high temperature .

Lionfish invade the Mediterranean | Richard Aspinall

The happy ending of blue crabs from invasive species to high-value export food is an extremely rare case . Most invasive species are not only unpalatable, but also cause damage to native species and the ecological environment.

For humans, even if we can eat more invasive species, it would be terrible if blue crabs were the only thing we could eat in the future .

References

[1] UNESCO, Charfia fishing in the Kerkennah Islands, accessed 2 Jun 2023,.

[2] Ennouri R, Zarrouk H, Fatnassi M, et al. Development of the fishing and commercialization of the blue crabs in Bizerta and Ghar EL Melh lagoons: A study case of promotion opportunities of blue growth in Tunisia. J Aquac Mar Biol . 2021;10(2):66-74. DOI: 10.15406/jamb.2021.10.00308

[3] FAO 2021, From invasive species to high-value export commodities, accessed 2 Jun 2023,.

[4] Aïda Delpuech, 2022, The crab invading the Mediterranean Sea, BBC Future, accessed 2 Jun 2023,.

[5] Gloria Dickie & Jihed Abidellaoui, Mediterranean marine heatwaves threaten coastal livelihoods, Reuters, accessed 2 Jun 2023,.

Author: Maya Blue

Editor: Mai Mai

Title image source: Valerio Crespi / FAO

This article comes from GuokrNature (ID: GuokrNature)

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