3.4 Nutrition and Growth 



3.41 Feeding 



Very little is known about the feeding behavior of 

 the black marlin. During fishing operations off Hana, 

 Maui, a large black marlin (referred to as silver 

 marlin in the publication; see footnote 2) was caught 

 on a longline at a depth of about 60 fathoms. The fish 

 had an abnormally distended abdomen and, upon 

 gutting, a bigeye tuna, Thunnus obesus Lowe, was 

 found in the stomach. This tuna, which weighed 

 about 160 pounds (72.7 kg), had been caught on the 

 longline first, for the hook was still set in the tuna's 

 mouth when the specimen was removed from the 

 stomach of the marlin. The marlin evidently had 

 found the hooked tuna an easy prey and swallowed it 

 head first (June 1951). Black marlin have often been 

 observed to swallow adult skipjack tuna, Euthynnus 

 pelamis (Linnaeus), or bigeye tuna, head first (Togo, 

 pers. commun. 4 ). 



3.42 Food 



Tanoue (1953) studied the food of the black marlin 

 near Mangole Island and Timor Island. The most im- 

 portant food items of the black marlin from Mangole 

 Island were various fishes such as Decapterus, Auxis, 

 Gempylus serpens Cuvier, Pseudoscopelus, 

 Tetraodontidae, Atherinidae, and Paralepididae and 

 decapod molluscs. Principal food items of black 

 marlin from Timor Island were fishes such as 

 Syngnathidae, Auxis and Oxyporhamphus, and 

 megalop larvae of Crustacea, Isopoda, and decapod 

 molluscs. 



In the East China Sea, most important food items 

 of black marlin are mackerels, Scomber spp. and 

 horse mackerels, Trachurus spp. (Morita, 1960). 



Watanabe (1960) studied the food of the black 

 marlin in the Pacific equatorial waters. Fishes of the 

 families Scombridae, Gempylidae, Coryphaenidae, 

 Xiphiidae, and Carangidae and decapod molluscs 

 were the most important food of the black marlin. 

 Fishes of the families Sternoptychidae, 

 Paralepididae, Alepisauridae, Chiasmodontidae, 

 Chaetodontidae, Balistidae, Ostraciontidae, and 

 Tetraodontidae, and octopods and macrura 

 crustaceans were of lesser importance. 



3.43 Growth Rate 



Koto and Kodama (1962) studied the black marlin 

 of the East China Sea, and the annual growth in 

 length was estimated as follows: 1) in the 150- to 200- 

 mm group (the minimum size class in the commercial 

 catches) the annual growth is 50 cm; 2) in the 200- to 



'Togo, S., 1972, personal communication on feeding habits of the 

 black marlin. Soroku Togo is an expert technician on the research 

 vessel of the Fisheries Agency of Japan. 



230-cm group, which is 1 yr older than the above 

 group, it is 30 cm; 3) in the 230- to 250-cm group, it is 

 20 cm; and 4) above the 250-cm group, it is difficult to 

 estimate the annual growth, as seasonal shifts of the 

 modes are not discernible. Black marlin in the East 

 China Sea grow most rapidly during the period from 

 early summer to late autumn. 



3.44 Metabolism 

 No studies. 



3.5 Behavior 



3.51 Migration and local movement 



In the East China Sea, the schools of the black 

 marlin migrate northward during spring and summer 

 and migrate southward during autumn and winter 

 (Koto et al., 1959). In the Japan Sea some black 

 marlin seem to migrate northward with the core of the 

 Tsushima Current during summer and migrate 

 southward against the Tsushima Current during late 

 summer and early autumn (Nakamura, unpubl. 

 data). 



In the tropical western Indian Ocean, the black 

 marlin is more abundant during the northeast mon- 

 soon period than the southeast monsoon (Merrett, 

 1971). 



3.52 Schooling 



There is little data on the schooling behavior of the 

 black marlin. When the monsoonal winds change 

 suddenly in direction and intensity around the waters 

 of Taiwan, schools of black marlin appear at the sur- 

 face. The harpoon fishery becomes active in this 

 period (Nakamura, 1938). 



3.53 Responses to stimuli 

 No data. 



4. POPULATION 



4.1 Structure 



4.2 Abundance and Density of Population 



4.3 Natality and Recruitment 



4.4 Mortality and Morbidity 



4.5 Dynamics of Population as a Whole 



4.6 The Population in the Community and the 

 Ecosystem 



There are a few fragmentary observations on these 

 topics under item 4, but there are no specific studies. 



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