Distribution

1. Cosmopolitan in all oceans except for Arctic and Antarctic zones. Several species also in fresh water.
2. Tropical to temperate oceans.

Poisoning occurs practically only in tropical island regions, possibly also isolated cases in the Mediterranean.

Biology

Economically significant edible fish. Most swim in enormous schools in open water. Feed off plankton or smaller animal organisms. Body generally elongated and slender, Clupeidae under 50 cm and Engraulidae under 20 cm. Grey-green colouring on the back and shiny silver on the belly and sides (typical colouring for fish of the open sea).

Poisonous populations occur sporadically and in geographically limited areas. The concentration of poison appears to be highest in the viscera. Nothing is known about the poison or its origin, but it is assumed that poison accumulates via the food chain. Since clupeid fish are primarily plankton feeders, it is likely that some of them ingest highly toxic dinoflagellates, such as Ostreopsis siamensis.

Risk

Clupeotoxic fish poisoning is rare and resembles ciguatera, but is very rapid in its action. It is suggested, that palytoxin is the cause of clupeotoxism (see Palytoxin poisoning). In a fatal case after consumption of small quantities of a sardine (Herklotsichthys quadrimaculatus) in Madagaskar palytoxin was found in the tissue of the fish (Onuma et al. 1999).

Clupeotoxism is said to have a high mortality rate and death may occur in less than 15 minutes (Halstead 2001a). Sporadic cases of poisoning due to clupeotoxic fish are known in island regions of the tropical Atlantic and Pacific as well as in the Caribbean. They are caused by fish caught close to the coast. Clupeotoxicity is most likely to occur during the warmest months. During this period in the above-named regions, the consumption of herrings, sardines and anchovies should be avoided. Individual toxicity can be very variable even within the same school of fish. 

Preparing the fish by boiling, salting or drying does not decontaminate them. It is not possible to identify poisonous fish from external characteristics, but they may leave a metallic or bitter taste in the mouth when eaten.

Clupeotoxicity is suspected to also be associated with Albulidae (Bonefishes), Alepocephalidae (Slickheads), Elopidae (Ladyfishes) or Pterothrissidae. Herrings, sardines and anchovies can also be ciguatoxic.

Signs and symptoms

Local effects: nausea, vomiting, abdominal pain, diarrhoea.

Neurological effects: sensory disturbance, paralyses.

Muscular effects: muscular pain.

Cardiac effects: arrhythmia, arterial hypotension.

Treatment

Symptomatic, see also ciguatera poisoning.

Literature (biological)

Halstead 1988, 2001a, Auerbach and Halstead 1989, Bagnis et al 1970