lished reports. This implies mechanical injury is the 

 most likely cause, with the ulcers being further ag- 

 gravated in those stomachs containing parasitic 

 nematodes. 



Digestive action by gastric secretions after death 

 is another possibility, but it seems highly unlikely the 

 large size of some ulcers could develop even during 

 the lengthy interval between capture and preserva- 

 tion of the stomach. For example, the 83.9 kg black 

 marlin captured in 1968 had one ulcer that was 40 mm 

 long, 27 mm wide, and 10 mm deep (measurements 

 after preservation in Formalin). In addition, 30 

 nematodes and necrotic tissue were present in the pit 

 of this ulcer. 



High concentrations of free circulating histamine 

 might possibly cause ulcers by increasing gastric 

 acid secretions. It is known that histamine has an 

 ulcerogenic effect on warm-blooded animals (Hay et 

 al., 1942). Geraci and Gerstmann (1966) have sug- 

 gested that histamine from a diet of inadequately 

 preserved fish caused gastric ulcers in a captive 

 bottle-nosed dolphin, Tursiops tniiuatiis. Fresh fish 

 contain negligible amounts of histamine, but under 

 conditions of inadequate preservation, decarboxyla- 

 tion results in the formation of histamine from his- 

 tidine (Geraci and Gerstmann, 1966). Since marlin 

 feed on fresh fish, it seems unlikely much of the 

 prey's histidine may find its way into the marlin's 

 blood stream as histamine. Further, the effect of 

 histamine on gastric secretions in teleosts is un- 

 known. In the spiny dogfish shark, Squaliis acan- 

 thias, perfusion of isolated gastric mucosa with his- 

 tamine resulted in an increased secretion of acid 1 to 

 1.5 times the amount secreted by isolated dogfish 

 gastric mucosa not perfused with histamine, but high 

 concentrations of histamine were required (Hogben, 

 1967). 



Increased gastric secretion from behaviorally in- 

 duced stress conceivably might have an ulcerogenic 

 effect on marlin. The average sex ratio of blue marlin 

 landed during Hawaiian International Billfish Tour- 

 naments from 1962 to 1972 has been 3.3 males:! 

 female, while blue marlin caught by commercial fish- 

 ing in subsurface waters in Hawaii have an almost 

 1:1 sex ratio (Strasburg, 1970). It has been suggested 

 the unequal sex ratio of blue marlin caught during the 

 tournaments may indicate a spawning aggregation. 

 Such an aggregation conceivably might be stress- 



inducing but this is highly speculative and probably 

 unrelated to ulcer occurrence. Adequate data on the 

 sex ratio of black marlin are not available. 



ACKNOWLEDGMENTS 



We gratefully acknowledge the cooperation of 

 anglers and officials of the annual Hawaiian Interna- 

 tional Billfish Tournament in making these speci- 

 mens available for examination. 



We thank Ross F. Nigrelli, Donald W. Strasburg, 

 and Heeny S. H. Yuen for reading the manuscript 

 and for offering advice. 



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