The class Pisces incorporates a number of species which could be hazardous to man. The presented hazard could result either by virtue of their size causing severe bite injuries e.g. sharks; or by virtue of their being inedible; or by virtue of their defense mechanisms which incorporate poison glands.

Order Batoidei - Family Rajidae: Rays and skates

These fish live chiefly on or near the bottom. The body is very flat, with a long thin tail which is clearly demarcated from it. The tail may carry a poisonous sting. The spines of the stingray are situated on the rear half of the tail. There are toxic glands, from which a slimy secretion is passed through longitudinal grooves along the spines. These spines often cause deep wounds, which are painful in themselves. Since the spines will often break off in the wound, they are difficult to heal. The species generally encountered in Maltese waters is the Common Stingray Dasybatus pastinachus.

• Belonging to the Family Torpedinidae, the Common Torpedo Torpedo torpedo has electric organs on both sides of the body, which enable the fish to defend itself with a relatively strong discharge [about 70-80 volts]. The attack is in itself harmless to man, but unpleasant enough for divers and fishermen to avoid it.

 Family Trachinidae: Weaver fish
Family Uranoscopidae: Stargazer

These fish live on the bottom usually buried in the sand and mud. They are notorious for their poison spines. The weavers spawn in the hot summer months, when they bury themselves in the sand or mudsurf, leaving erected the black first dorsal ray equipped with the venomous spines well visibly exposed. When the fish is disturbed, such as when accidentally treaded upon they become aggressive and defend themselves by stinging the unwary intruder with their needle sharp spines. On rare occasions as well, they are known to have actually attacked swimmers, harpoonists, and snorklers. The araneus species can be found in water even 100 meters in depth. The smaller weavers tend to come inshore and can be found in water only a few inches deep. They can be caught by rod-fishermen, but more commonly by the various netting methods and trawlings. Harpooning a weaver constitutes a real hazard, as the injured fish becomes very aggressive and its removal from the spear is rather tricky and difficult as regards avoiding self injury. The Trachinidae remain alive out of sea for quite a long time and one has to remember that their spines remain poisonous even after the fish dies. It is therefore quite a usual practice for the spines to be cut and removed by fishermen or fishmongers as a precaution both to themselves and to their customers. The culinary food value of weaver and commensibility is quite good. Several species are known in Maltese waters: Tachinus vipera; Trachino draco; Tachinus lineatus; and Tachinus araneus. Closely related to the Trachinididae is the Stargazer Uranoscopus scaber.

Family Scorpaenidae: Scorpion Fish

<>The spiny rays in the dorsal fin and gill flap spines of the Scorpion Fish species are poisonous. The species are often found on rocky ground among the algae or over sand from 10 m depth. Several species are known from Maltese waters including Scorpoena porcus; Scorpoena scrofa; Scorpoena ustulata; and Helicolenus dactylopterus.

 

Clinical Features:

With injection of the toxin, the sting of the poisonous fish causes an immediate severe stinging or throbbing pain which may stay at the site of the wound or spread throughout the body and last for several hours or days. Reaction varies from person to person.  Most Stingray wounds are found on the ankle or foot and may be more of a laceration than a wound; while the plantar aspect is the most frequent site for Weaver or Scorpion fish stings. There may be redness and swelling at the site of the sting, and the area may become numb, followed by dizziness, weakness, cramps, sweating and falling blood pressure.

Treatment:
The treatment of fish sting poisoning is largely empirical, there is no known antidote.

• Denaturing the toxin
• Alleviation of pain.
• Counteracting allergic manifestations
• Prevention of secondary infections.

For the less toxic species:-

• As first aid, it is essential to clean the wound thoroughly with fresh or salt water and sucked out.

• The affected area should be soaked in hot water or covered with a hot compress. The water should be very hot (circa 122 F), so that the heat will deactivate the poison.

• Strong analgesics may need to be given, but the injection of 2 ml of 2% lignocaine immediately on and around the puncture wound may suffice.

• It is essential to avoid infection of the wound, and antibiotics should be used. Lacerations should, if necessary, be closed surgically and cleaned with antiseptics. Tetanus shots should also be administered for those who are not previously immunized.

For the more toxic species:-

• Continue applying hot water for 30 minutes to an hour.

• The patient should lie still with the stung part immobile and lower than the heart. Tie a venous tourniquet around a stung limb two or four inches above the sting. If the swelling reaches the band, tie another venous tourniquet two or four inches higher up and remove the first one.

• Allergic manifestations are dealt with the usual antihistaminic drugs such as Piriton, Phenerghan and Tavegyl, but local injection of epinephrine and subsequent use of neostigmine has been suggested for the management of severe toxic species poisoning. 

• Mechanical ventilation and measures to combat shock may be needed in hypersensitive cases.

Generally, victims recover within 48 hours, although hospitalization may be required for those with persistent symptoms of chest pain, irregular pulse or hypotension.