animal and perhaps longer (as indicated by the 

 loss of nuclei in the affected muscle cells). Also, 

 additional time would have been required for the 

 isopod to penetrate the body wall of the shark and 

 into the heart, and for the heart tissue to become 

 necrotic. The disparity between the number of 

 hours the shark could have been on the line and 

 the length of isopod residence time in the heart 

 muscle as shown by the well-developed necrosis 

 would, therefore, indicate that the shark was 

 attacked by C. borealis before it was hooked. Field 

 tests in 1979 and 1980 could not, unfortunately, 

 resolve this possibility (because C. borealis was 

 not found in nearshore waters by that time) and it 

 must remain speculative. 



There is no evidence that C. borealis contributed 

 to the sudden decline in shark catch in 1978, 

 although it certainly affected utilization of catch 

 adversely. A coincident decline in commercial 

 catches of snapper and grouper that occurred in 

 the area also appears unrelated to the isopods per 

 se, particularly as no association was noted be- 

 tween C. borealis and teleosts in regard to catch 

 depredation or predation. Probabilities are strong, 

 however, that populations of sharks, teleosts, and 

 isopods were all influenced by common water 

 parameters. Upwellings have historically been 

 associated with declines in fish catch (Jones et 

 a\}°) and were shown by George and Staiger^^ to 

 be dominant in inducing shifts in benthic inver- 

 tebrate and demersal fish populations in the 

 South Atlantic Bight. 



The Cape Canaveral shark fishery might not 

 have closed in 1978 had the nature of the isopod 

 problem been known at that time. The operator 

 thought the shark flesh was contaminated by the 

 isopods and was afraid to sell it, thus needlessly 

 lost his profitable market for the meat. This, 

 combined with reduced profits from the pitted 

 hides and the decline in shark catch, caused undue 

 financial hardship. The encounter with a totally 

 new problem, of an unknown future duration, 

 doubtlessly contributed to the disillusionment of 

 the operator. Occasional occurrences of C borealis 

 in shallow waters should not be considered a 



'"Jones, R., R. Gilmore, Jr., G. Kulczycki, and W, Magley. 

 1975. Studies of the fishes of the Indian River region. In 

 Indian River Study, Harbor Branch Con.sorlium, Annual Rep., 

 1973-74, Vol. 1, p. 110-18.3. Harbor Branch Consortium, North 

 Old Dixie Highway, RFD 1, Box 196, Fort Pierce, FL 33450. 



"George, R.,and J. Staigen 1979. Kpifauna: benthic inver- 

 tebrate and demersal fish population of the South Atlantic/ 

 Georgia Bight. In South Atlantic OCS Benchmark Program, 

 1977 Report, Vol. 3, p. 237-279 (see footnote 5). 



deterrent to the establishment of commercial 

 shark fishing operations in Florida, however. The 

 phenomenon, if it recurs, should be of compara- 

 tively short duration; knowledge of this should 

 aid fisheries to budget realistically during the 

 interim. Isopods in sharks do not constitute a 

 hazard to human health and their presence does 

 not render shark flesh unmarketable. More fre- 

 quent collection of setlines and experimental sets 

 to define areas of less isopod prevalence would 

 help alleviate problems of shark fisheries during 

 possible future occurrences of C. borealis in near- 

 shore waters. 



Acknowledgments 



This research was funded by the Florida Sea 

 Grant College with support from the National 

 Oceanic and Atmospheric Administration, Office 

 of Sea Grant, U.S. Department of Commerce, 

 #04-8-M01-76. I greatly appreciate the enthu- 

 siastic help in the field given by my student 

 research assistants and the support from Sea 

 Grant Agent Joe Halusky. Special thanks are 

 extended to William Luer for his efforts in his- 

 tological examinations and to Thiele Wetzel 

 for his great contribution of time, effort, and 

 boat facilities. The aid from William Tiffany 

 in evaluating histopathological results is deeply 

 appreciated. 



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