broken tips of marlin bills in them were found in the 

 Mozambique Channel and believes that marlin must 

 deliberately charge floating or submerged objects 

 possibly to secure food or from plain aggressive- 

 ness. 



A blue marlin with a bent bill was reported by 

 Ovchinnikov (1970) from off West Africa. 



3.4 Nutrition and Growth 

 3.41 Feeding 



According to data from the northern Gulf of Mexico 

 presented by Nakamura and Rivas (1972) blue marlin 

 rise to a surface trolled bait more often in the morning 

 between the hours of 1000 and 1100 and least often 

 between 1200 and 1300 (central standard time). There 

 is agreement in this for both South Pass, La., and the 

 northwest Florida areas. The South Pass data also 

 show that, in the afternoon, there is another well- 

 marked peak between 1500 and 1600 but the 

 northwest Florida data show a steady decrease from 

 1400 on. 



Many sport fishermen have told me that they have 

 tried without success to raise marlin during the night 

 by surface trolling. I have tried, also without success. 



From the information discussed above, it may be 

 tentatively concluded that blue marlin do not feed at 

 the surface at night and that there is a marked feeding 

 period in the morning between 1000 and 1100. 



De Sylva (1963) stated that during the 1963 

 Jamaica International Fishing Tournament more 

 marlin were raised in the afternoon between 1400 and 

 1600 than at any other time of day. His results, 

 however, were given in terms of the number of fish 

 raised during 2-h intervals as a percentage of the total 

 number of fish raised. No data on the effort expended 

 was given. 



I have heard many discussions among sport fishing 

 guides and anglers about whether or not the blue and 

 other marlins use their bill in capturing prey. These 

 discussions, however, refer mostly to prey in the form 

 of artificial or natural dead baits trolled at the surface 

 at a uniform speed, usually 4 to 8 knots. In my opin- 

 ion, based on many years of observation, marlins do 

 not use their bill when taking a trolled bait. The 

 lateral thrusts of the bill, which appear to be aimed at 

 hitting the bait, are apparently the result of rapid 

 changes in direction of movement of the fish and/or 

 the effect of its swimming motions when the bill and 

 head are partly out of the water. 



As to the use of the bill when the fish is pursuing 

 free-swimming prey, there is, again, difference of 

 opinion but the general concensus is that the bill is 

 not generally used to stun the prey. 



Ovchinnikov (1970) discussed the use of the bill by 

 marlins and concluded that it is not of importance in 

 the capture of food. As pointed out by Ovchinnikov 

 and as discussed above under 3.35 Injuries and 



abnormalities, marlins without bills or with bro- 

 ken or malformed bills are as healthy as the normal 

 fish. 



The various incidents of fish, boats, and various 

 other floating objects impaled by marlin bills cited in 

 the literature are, in my opinion, accidents resulting 

 from feeding. It is well known that small fish con- 

 gregate under such floating objects and that a marlin, 

 in attempting to catch a fish too close to the floating 

 object, may accidently impale it with its bill. 



Tinsley (1964) gives a detailed discussion on the use 

 of the bill in the sailfish which could well apply to the 

 blue and other marlins. 



3.42 Food 



The literature shows that the types of food eaten by 

 the blue marlin vary somewhat with the region where 

 they occur. It is also indicated that the blue marlin 

 feeds at or near the surface and in deep water, and 

 near shore as well as out in the open sea. 



Stomachs of blue marlin contained mostly squid in 

 the Philippine Sea (Nakamura, 1942), tunalike fishes 

 in New Zealand (Baker, 1966) and the central Pacific 

 (Royce, 1957), and dolphin (Coryphaena) and 

 tunalike fishes, especially frigate mackerel (Auxis), in 

 the Bahamas (Krumholz and de Sylva, 1958). On a 

 volumetric basis, tunalike fishes constitute more than 

 85% of the diet in Hawaii (Strasburg, 1970). In Puerto 

 Rico tunalike fishes, in both number and volume, 

 were the chief food of the blue marlin examined by 

 Erdman (1962). Frigate mackerel was the most fre- 

 quent individual item, and whenever it occurred in 

 abundance blue marlin fishing was better than 

 average. De Sylva (1963) indicates that only a 

 relatively few types of organisms are eaten by blue 

 marlin in Jamaica, the tunalike fishes being the most 

 important. In the northern Gulf of Mexico fishes, es- 

 pecially dolphin and scombrids, were the most impor- 

 tant food items found in the stomachs of blue marlin 

 (Nakamura and Rivas, 1972). In the tropical western 

 Atlantic, Ovchinnikov (1970) indicates that the blue 

 marlin feeds mostly on fishes and cephalopods. 



The size range of the organisms eaten by the blue 

 marlin is relatively large. Krumholz and de Sylva 

 (1958) indicated that the overall range in length for 

 fishes was from about 20 to 102 cm (about 8 to about 

 40 inches). One of the octopods was about 15 cm 

 (about 6 inches) whereas the largest one was about 61 

 cm (about 24 inches) long. Erdman (1962) recorded 

 from Puerto Rico a 135-kg (279-lb) blue marlin which 

 had eaten a postlarval surgeonfish 38 mm long. He 

 also mentioned a squid weighing up to 11 kg (23 lb) 

 taken from the stomach of a blue marlin. Strasburg 

 (1969) mentioned that a blue marlin was caught in 

 Hawaii with a 29-kg (63-lb) bigeye tuna, Thunnus 

 obesus, in its stomach. The marlin including the tuna 

 weighed 340 kg (748 lb). Ovchinnikov (1970) reported 

 from the Gulf of Guinea a 290-kg (638-lb) blue marlin 



