374 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



Whatever may be the dental equipment and the food and feeding 

 habits of the young and half -grown fish, it is fully established that 

 the adult fish is entirely devoid of teeth and is a strict vegetarian. 

 Visual and tactile examination of fish over 2 meters long in Cambodia 

 and Laos prior to and during their upstream migration disclosed to 

 the writer the absence of even a vestige of teeth in the jaws and on 

 the vomer and palatine bones; and all the information available, 

 drawn chiefly from Cambodian, Laos, and Siamese fishermen and 

 from French and Thai officials along the Mekong, supplemented by 

 limited personal observation, indicates that the food of the fish con- 

 sists largely, perhaps exclusively, of algae cropped from stones on 

 the bottom and sides of the river. The frequent presence of stones, up 

 to the size of a man's fist, in the stomach and intestine of the fish is 

 easily accounted for by the supposition that they have been inad- 

 vertently swallowed in efforts to detach the algae. 



It is stated by Pavie and others that when the fish is in Cambodian 

 waters, prior to the upstream migration, its flesh is very fat and for 

 that reason is not highly regarded for human food. By the time the 

 fish reaches Luang Prabang it has lost much of its fatness and is in 

 good repute as a food, bringing a high price in the markets. Coin- 

 cident with the decrease of fat in the tissues there is enlargement of the 

 sex glands, and the writer has seen salted ovaries over 60 cm. long 

 that had been taken from fish caught at Luang Prabang and pre- 

 served for a select Thai trade. 



For a fish of such extraordinary size, striking habits, economic im- 

 portance, and ethnological and historical interest, it is surprising that 

 so little is definitely known regarding it. There has never been a real 

 study of its habits, migration, spawning, growth, etc. That the study 

 is much needed is shown by the lack of basic information regarding 

 the fish and by some of the statements that have appeared in print 

 illustrative of the views of fishermen and other persons. Thus, the 

 Laos people in the French Province of Laos believe that only the 

 females wander freely over the river and imagine that the males, with 

 golden scales, await their arrival in Lake Tali, which they never leave.^ 

 A communication to the Journal of the Natural History Society of 

 Siam (Duke, 1921) implies that the creature nourishes its young with 

 milk, a view that has been expressed orally to me by Thai officials 

 who visited the upper Mekong and saw the fish there more than half 

 a century ago. The scanty literature and the writer's interviews with 

 fishermen and local officials concerned with activities along the Mekong 

 have afforded no references to fish less than a meter long. 



The celebrated giant catfish of the basin of the Mekong remained 

 without a scientific name until 1930. Various conjectures as to its 



« Pavie (1904) quoted by Chevey (1930). 



