ONR SHARK RESEARCH 649 



Marine officers discussed how effective such a repellent would have to be, 

 the consensus was that a deterrent that repelled sharks at least two times out 

 of three, or 67% of the time, could be considered effective enough for 

 distribution to personnel. However, one of the officers disagreed and wrote 

 in a minority opinion that only repellents that worked nearly always should 

 be issued. Curiously, no one present seemed to hold out for complete 

 (100%) effectiveness, perhaps because of the realization that this would be 

 an ideal that would be difficult, if not impossible, to attain. 



To search for an effective chemical shark repellent, a research program 

 was set up at the Naval Research Laboratory (Tuve 1963). The first clue was 

 one that shark fishermen had long ago noticed; if a shark is caught on a 

 fishing line, dies, and for some reason is not retrieved before decomposition 

 sets in, then further fishing for sharks in that vicinity is useless. In other 

 words, rotting shark meat appeared to act as a shark repellent, or at least a 

 feeding inhibitor. Tests conducted in a chemical laboratory on samples of 

 rotting shark flesh indicated that the most abundant chemical byproduct was 

 ammonium acetate. 



From other preliminary screening tests on a variety of chemicals at the 

 Woods Hole Oceanographic Institution, maleic acid and copper sulfate 

 showed some promise in inhibiting feeding in dogfish sharks. Maleic acid was 

 subsequently eliminated, and, because of instability problems with 

 ammonium acetate, the acetate portion was combined with the copper 

 portion of the copper sulfate. Consequently, copper acetate was tested as the 

 active ingredient. However, copper acetate was virtually invisible when 

 dissolved, so a black pigment, nigrosine dye, was added in later tests to 

 permit humans to see the chemical cloud in the water. It was added mainly 

 for its psychological effect, since tests showed that the nigrosine dye diffuses 

 at a different rate than the copper acetate. In any case, the mixture of 80% 

 nigrosine dye and 20% copper acetate proved effective, sometimes nearly 100% 

 effective, in keeping sharks from feeding, even when they were already actively 

 feeding on trash fish shoveled off the deck of a shrimp boat. 



Tuve (1963) and Gilbert and Springer (1963), in their detailed reviews of 

 the repellent research program, discussed the results of the three sets of field 

 tests conducted off northern Peru, Biloxi, Mississippi, and Mayport, Florida, 

 noting that five kinds of sharks were listed in the Biloxi tests— blacktip, 

 sharpnose, hammerhead, lemon, and tiger sharks. Few addditional species 

 were involved in the Florida and Peru tests. Thus, many species of dangerous 

 sharks were not tested, nor were tests conducted in nonfeeding situations. 

 However, the tests that were conducted indicated an overall effectiveness of 

 more than 67% for the mixture of nigrosine dye and copper acetate. 

 Consequently, these chemicals, mixed in a cake of water-soluble wax that 

 dissolved over a 3-h period, became the standard issue "Shark Chaser." 

 Whether or not it effectively repelled sharks under combat conditions, it was 

 certainly effective psychologically and helped morale, which was probably 

 the most important problem at that time. In fact, the psychological 

 aspect— the fear of sharks— continues to be one of the most serious problems. 



Given this kind of background, it shouldn't have been surprising that after 



