Confirmation of fishers’ local ecological knowledge of ciguatoxic fish species and ciguatera-prone hotspot areas in Puerto Rico using harmful benthic algae surveys and fish toxicity testing

Ciguatoxin fish poisoning (CFP) is caused by the consumption of tropical and subtropical fishes and other marine species with high levels of ciguatoxin (CTX) in their tissues. CTX is a polycyclic neurotoxin produced by single-celled, photosynthetic dinoflagellates in the Gambierdiscus and Fukuyoa genera which are found in close association with benthic autotrophs. CTX enters the food web when these dinoflagellates are inadvertently consumed by herbivores grazing on their preferred substrates. The toxin biomagnifies up the food chain to the top predators and if humans consume seafood with high levels of CTX it can cause a variety of flu-like symptoms. The best way to avoid CFP is to avoid toxic fishes. However, CTX is undetectable by physical inspection. This study investigated local fishers’ knowledge of ciguatera hotspots and coldspots along Puerto Rican coral reefs using toxic-dinoflagellate cell counts and by estimating fish toxicity in those sites using a cell-based Neuro-2a cytotoxicity assay. The fishers identified regions of high and low risk for CFP based on their local ecological knowledge (LEK) which were deemed hotspots and coldspots, respectively. There is a 35-fold difference in dinoflagellate cell counts of low-toxicity G ambierdiscus species in samples in the identified hotspot compared to the coldspot. Also, higher trophic level fishes (>3.4 ETL) had higher median estimates of CTX in their tissues at the hotspot than the same species in the coldspot. This study shows the effectiveness of LEK in identifying potential problem areas for ciguatera.