Methods of Determining Toxicity 



The natives of the West Indies have numerous methods for de- 

 termining whether or not a fish is poisonous, but none seems to be reliable,. 

 The people of tropical and subtropical areas, where fish poisoning is 

 prevalent, often have to depend on fish as a source of food supply, Because 

 poisonous fish cannot be recognized by observation or by any infallible test, 

 it is apparent that a determination of the source of poisoning and methods 

 of prevention would solve a vital problem. Therefore, an investigation of 

 Ciguatera was conducted by the U. S. Fish and Wildlife Service in the areas 

 near Puerto Rico and the Virgin Islands in 19it5» 



PART II— FISH AND WILDLIFE SERVICE INVESTIGATION OF THE PROBLEM 



Since no source of poisonous fish could be found in Puerto Rico 

 during the early phase of the investigations, a field laboratory was 

 established at the U, So Naval Hospital at Bourne Field, in Charlotte Amalie, 

 St, Thomas, V. I. Preliminary work was conducted in this temporary labo- 

 ratory until arrangements were made to insure an adequate supply of fish| 

 later the work was continued at the Fishery Research Laboratory at Mayaguez, 

 P. R = 



Source of Fish 



The fish used were from those species considered poisonous by 

 the French fishermen off St., Thomas and by the native fishermen of Jost Van 

 Dyke Island, The fish obtained from the French fishermen were caught west- 

 southwest of St. Thomas in the general vicinity of Sail Rock which is located 

 in a supposedly poisonous area, The fish obtained from the fishermen of Jost 

 Van Dyke Island were caught in the waters between St Thomas and St, John, 

 Occasional specimens of fish were obtained from sports fishermen, most of 

 which were caught near St, Thomas, Most of these fish were out of water on 

 the average of eight hours without refrigeration before they were landed. 

 During the course of work in St, Thomas, the fish were examined, whenever 

 possible, immediately on their arrival at the laboratory. Otherwise, they 

 were refrigerated or frozen and held until they could be examined. When the 

 study was conducted in Mayaguez, the source of supply of fish was from the 

 St. Thomas area. The fish were frozen there, then shipped in the frozen 

 state to Mayaguez, and held frozen until they could be examined. The effect 

 of freezing on the toxicity of fish is not known, however, this was the only 

 way of insuring an adequate supply of fish for the tests. 



Laboratory Procedures 



General 



On arrival at the laboratory, the fish were identified as to genus 

 and species. Their length, width, and weight were recorded. The size, 

 condition, and weight of the gonads and the general condition of the viscera 

 were noted. The contents of the stomach were then examined, and a maoroscopic 

 examination for the presence of endoparasites and ectoparasites was made<> 



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