Diving guide · Invasive species

Invasive species: lionfish and pufferfish on Turkish dives

Along Turkey’s Mediterranean and Aegean coasts you now meet species that arrived from the Red Sea through the Suez Canal. Most are harmless, but three matter directly to divers: the lionfish with its venomous spines, the silver-cheeked toadfish, whose flesh is poisonous and which can bite, and the stinging nomad jellyfish. The first rule is the same for all of them: don’t touch, don’t feed, don’t try to catch them by hand.

Species Where the danger comes from What to do on a dive
Lionfish Venomous spines on the dorsal, pelvic and anal fins Keep your distance, don’t try to catch it
Silver-cheeked toadfish Tetrodotoxin when eaten; a strong bite Don’t feed or chase it; don’t eat it even if someone has caught one
Nomad jellyfish Stinging cells on the tentacles Stay clear; a thin wetsuit or Lycra protects you

Lionfish

Pterois miles

Its first scientific record in Turkish waters is from İskenderun Bay on 13 April 2014.1 A year later, in August 2015, came the first Aegean record: divers saw one off Dalyan at 11 metres on a sandy bottom.2 It has since reached as far north as Edremit Bay, where it was first detected in 2022; a specimen was taken off Güneş Island in June 2023.3

The venom is only in the spines: 12–13 on the dorsal fin, 2 on the pelvic fins and 3 on the anal fin, with the venom glands in grooves along the spines.4 So a lionfish is venomous when it stings, but its flesh is not poisonous: once the spines are removed it can be eaten.5,6

Most stings happen to people handling the fish. Of 33 cases DAN reviewed, 21 occurred while holding a speared fish and 7 while trying to catch one; only 5 were accidental.7 A sting causes intense pain lasting hours, rapid swelling and bruising; the swelling usually goes down in 2–3 days, the discolouration can last up to 5 days. It is not fatal for a healthy person; DAN knows of no published death.4 It can be more serious in young children, people with heart disease and those with weakened immunity.7

If a lionfish stings you

First stay calm and finish the dive at a normal ascent rate, with your safety stop. In DAN’s records a diver who surfaced quickly after being stung developed decompression sickness.4

  1. Wash the wound thoroughly with soap and fresh water, remove any foreign material such as spine fragments, and control bleeding.
  2. Immerse the area in the hottest water you can tolerate without scalding: no more than 45 °C, for 30–90 minutes; repeat if needed. Intense pain dulls your sense of heat, so have someone else test the water on the same part of their own body. Heat breaks down the venom.4,7
  3. Afterwards, apply a cold pack or ice for swelling and pain.
  4. Always see a doctor; you may need a tetanus shot and antibiotics. If symptoms are severe, call emergency services: 112.4

The risk of scalding is real: in DAN’s records one diver’s hand was burned this way and the wound became infected.4

Silver-cheeked toadfish

Lagocephalus sceleratus

Its first confirmed record in the Mediterranean is from Turkey’s Aegean coast in 2005.8 According to Turkey’s Ministry of Agriculture and Forestry, pufferfish that came from the Red Sea and settled in the Mediterranean have spread into the Aegean and the Sea of Marmara; the Ministry singles out the silver-cheeked toadfish as the most common and most dangerous species.9

Its flesh is poisonous, and cooking doesn’t help

The fish carries tetrodotoxin. Cooking does not destroy it, it has been found in all tissues including the muscle, and there is no known antidote; treatment is supportive only.10 A year of monthly measurements in Antalya Bay found it dangerous to eat in every month, with the highest levels in November–December.11 Of 198 incidents compiled in the eastern Mediterranean between 2004 and 2023, 27 were deaths from eating it.10 If you see this fish on a dive boat or at a fishmonger, don’t eat it; if you have eaten it, there is no first aid at home: go to a health facility immediately.10

Under water

The silver-cheeked toadfish usually avoids people; researchers do not yet consider its biting an imminent health threat. Still, its strong, beak-like teeth can cause serious wounds: on the northern Levant coast a child lost a fingertip this way.12 Preliminary findings suggest aggression may increase in the spawning season and at dawn and dusk feeding times, and that bright colours and objects may trigger it.10 Don’t feed it or follow it; if you are bitten, have the wound seen by a doctor.

Another small, cute-looking Red Sea pufferfish photographed at Kaş (Torquigener hypselogeneion) can get used to divers and has been seen nipping their fingers lightly. Don’t touch it either.10

Nomad jellyfish

Rhopilema nomadica

Its first record on Turkey’s Mediterranean coast was published in 1995.13 On Turkey’s eastern Mediterranean coast it affects human health, tourism and fisheries, and its painful sting can be a hazard for holidaymakers.14 Of 481 reports collected in Israel, symptoms were mild in 69% and severe in 7%; no lasting effects were reported.15 Severe allergic reactions (anaphylaxis) have been seen, though rarely.16 A thin wetsuit or Lycra offers protection.15

If a jellyfish stings you

  1. Rinse off tentacle fragments with sea water.
  2. Don’t use vinegar or urine; on Mediterranean jellyfish vinegar makes the stinging cells fire.15,17
  3. If the sting covers a large area or there are symptoms affecting the whole body, go to emergency care: 112.15

How they spread

Year Species Record
1995 Nomad jellyfish First record for Turkey’s Mediterranean coast published13
2005 Silver-cheeked toadfish First confirmed Mediterranean record, Turkey’s Aegean coast8
2014 Lionfish First record in Turkish waters, İskenderun Bay (13 April)1
2015 Lionfish First Aegean record, Dalyan, 11 m (August)2
2022–23 Lionfish Edremit Bay; 12 m off Güneş Island (June 2023)3
2024 Pufferfish Ministry: spread into the Aegean and Marmara9

Who else is on the list

A toxicology review of venomous invasive species in the Mediterranean also lists rabbitfish (Siganus luridus, S. rivulatus), the striped eel catfish, the stonefish, the long-spined sea urchin and a hydroid; cases are expected to rise with the widening of the Suez Canal, warming and tourism.18 Not touching spiny or unfamiliar animals works for all of them.

Dive sites → Wreck table → Try dive → Turkey diving map →

Sources (18)
  1. Turan C. et al. (2014). First record of the Indo-Pacific lionfish Pterois miles for the Turkish marine waters. J. Black Sea/Medit. Environ. 20(2).
  2. Turan C., Öztürk B. (2015). First record of the lionfish Pterois miles from the Aegean Sea. J. Black Sea/Medit. Environ. 21(3).
  3. Öztekin A. et al. (2023). Aslan balığı Pterois miles’ın Edremit Körfezi’nden ilave kaydı. Doğanın Sesi 6(12).
  4. Gomez Castillo J.D. (2018). Lionfish Stings. Alert Diver, Divers Alert Network.
  5. NOAA National Ocean Service (2019). Invasive Lionfish (podcast transcript).
  6. UNDP Türkiye (2023). Aslan balığı sorununu mutfakta çözmek.
  7. Denoble P. (2013). Lionfish Stings in Divers. Divers Alert Network.
  8. Akyol O. et al. (2005). First confirmed record of Lagocephalus sceleratus in the Mediterranean Sea. J. Fish Biol. 66(4).
  9. T.C. Tarım ve Orman Bakanlığı, BSGM (12.03.2024). İstilacı balon balığı avcılığı destekleme tutarları.
  10. Ulman A. et al. (2024). Assessment of Human Health Impacts from Invasive Pufferfish across the Eastern Mediterranean. Biology 13(4):208.
  11. Kosker A.R. et al. (2023). Monthly Variation of Tetrodotoxin Levels in Pufferfish Caught from Antalya Bay. Marine Drugs 21(10):527.
  12. Sümen S.G., Bilecenoğlu M. (2019). Traumatic finger amputation caused by Lagocephalus sceleratus bite. J. Black Sea/Medit. Environ. 25(3).
  13. Kideys A.E., Gücü A.C. (1995). Rhopilema nomadica: A Lessepsian Scyphomedusan new to the Mediterranean coast of Turkey. Israel J. Zool. 41(4).
  14. Öztürk B., İşinibilir M. (2010). An alien jellyfish Rhopilema nomadica and its impacts to the Eastern Mediterranean part of Turkey. J. Black Sea/Medit. Environ. 16(2).
  15. Edelist D. et al. (2023). Jellyfish sting web survey: clinical characteristics and management of Rhopilema nomadica envenomation. Reg. Environ. Change 23:114.
  16. Friedel N. et al. (2016). Severe anaphylactic reaction to Mediterranean jellyfish (Rhopilema nomadica) envenomation. Toxicol. Rep. 3.
  17. Ballesteros A. et al. (2023). Effect of Rinse Solutions on Rhizostoma pulmo Stings and the Ineffective Role of Vinegar in Scyphozoan Jellyfish Species. IJERPH 20(3).
  18. Bédry R. et al. (2021). Toxicological risks on the human health of populations living around the Mediterranean Sea linked to the invasion of non-indigenous marine species from the Red Sea. Toxicon 191.

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