Ciguatera Report First Half of 2020: And a Warning

A new ciguatera report was produced by the Coastal Section on 21st July. The report summarizes the results of monitoring of toxic dinoflagellates, that was carried out at twenty three sites in Funafuti Lagoon during the first half of 2020.

Ciguatera Fish Poisoning (CFP) is caused by the consumption, by humans, of fish that have accumulated toxins originating from bottom-dwelling toxic dinoflagellates, such as Gambierdiscus toxicus and other related species. Dinoflagellates are single-celled marine micro-algae, mostly between 50 and 100 microns across. The toxins they produce, namely gambiertoxins, are transformed into more potent forms (ciguatoxins) as they move through the marine food web.

Distribution and abundance during 2nd Qtr, 2020

The main findings of the study were that significantly higher counts of toxic dinoflagellates were found during the first part of 2020 (and particularly in the 2nd quarter), compared with the past 3 years, suggesting that a new outbreak might be building. It was recommended that Tuvalu Fisheries now urgently carries out a public awareness programme to remind people of the nature and causes of ciguatera and to inform them of the areas most likely to be toxic and the species of fishes most likely to be dangerous.

Table of average density of potentially toxic dinoflagellates per 100g of host algae for second quarter (June 23-25th, 2020). The colour scale shows high, moderate and low densities for Gambierdiscus toxicus. The other species are Prorocentrum lima, P. concavum and Ostreopsis sp.

The study is part of on-going monitoring of the distribution and abundance of toxic dinoflagellates to provide early warning to the population of Funafuti. The goal is that fishermen can avoid toxic areas of reef and therefore try to prevent further cases of poisoning of humans and livestock. It is thought that it takes several (up to 9) months for the toxins to accumulate or decrease in response to changes in the abundance of the micro-algae that produce them. This means that monitoring numbers can provide lead time before fish become toxic, and allows for the identification of areas of reef currently producing the toxins. Radio shows, posters and public meetings are being organised to inform the communities of the risk.