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Mapping Toxic Caribbean Habitats

Photograph of a blood sample being obtained from a great barracuda (S. barracuda) via caudal venipuncture using a 3 ml lithium heparin vacutainer and 3.8 cm (1.5?) 21 gauge needle. source: and Carleton University (CU) scientists joined forces to map potentially toxic fishing grounds in the Caribbean by tracking the movement of ciguatoxic fish over an extended period of time. Analysis of the blood of 38 great barracuda live-captured by the CU team off the coast of Cape Eleuthera, Bahamas revealed that about 60% of the fish contained ciguatoxin, indicative of a recent exposure to the toxin. Twenty of the sampled fish were fitted with acoustic transmitters, released, and tracked using an array of 50 signal receiving stations covering over 44 square kilometers for 321 days. Results showed that fish testing positive for ciguatoxin had a smaller home range and were more commonly found along the edge of the continental shelf, particularly in deep reef areas. These areas are accessible to local fisherman and would be considered high risk for ciguatera fish poisoning.

Spatial distribution and ecology of S. barracuda for ciguatoxin analysis near Cape Eleuthera, The Bahamas. A) Receiver stations at which telemetered barracuda were detected during the study period. Black circles represent stations that were visited by fish that tested positive for blood ciguatoxin and grey circles represent stations that had fish which did not exhibit ciguatoxin like activity. Open circles represent receiver stations included in the telemetry array during the study period that were not visited by tagged barracuda. B) Individual barracuda capture locations with associated muscle, liver, and blood CTX concentrations (pg/ml). Black filled triangles represent capture locations for barracuda that did not test positive for CTX. source: fish poisoning is a human illness caused by the consumption of reef fish contaminated with ciguatoxins and occurs in tropical and subtropical regions of the Caribbean Sea, Pacific Ocean, and Indian Ocean. Ciguatoxin is produced by dinoflagellates in the genus Gambierdiscus. Gambierdiscus lives in warm, shallow waters in association with various macroalgal species or in recently disturbed or altered marine habitats. The toxin biomagnifies through marine food webs, reaching peak concentrations in predators such as great barracuda, snappers, moray eel, and jacks.

It is estimated that more than 25,000 cases of ciguatera fish poisoning are reported worldwide every year. There is little information about the spatial ecology and foraging habits of fish commonly implicated in ciguatera poisoning. This information is needed to help reduce the occurrence of ciguatera poisoning, especially within island and coastal communities that are highly affected due to their reliance on reef fish as a major protein source.

In this project, NCCOS partnered with Carleton University, Ottawa, Canada to conduct the barracuda blood analyses. This collaborative study provides an example of the utility of combining non-lethal biopsies (in this case to determine ciguatoxin concentrations in blood) with biotelemetry or biologging tools to effectively evaluate spatial ecology of fishes. Results of the study will be published in Science of the Total Environment.

Carleton University Project Webpage

Related NCCOS publications
Use of two detection methods to discriminate ciguatoxins from brevetoxins: Application to great barracuda from Florida Keys
Optimization of ciguatoxin extraction method from blood for Pacific ciguatoxin (P-CTX-1)
Biomonitoring of ciguatoxin exposure in mice using blood collection cards
Identification of Ciguatoxins in Hawaiian Monk Seals Monachus schauinslandi from the Northwestern and Main Hawaiian Island
NOAA News Release 2003:  NOAA scientist develop blood collection cards that provide new on site technology for harmful algal bloom rapid response
NOAA News Release 2011:  Dangerous toxin discovered in critically endangered Hawaiian monk seal

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