FRESH-WATER FISHES OF SIAM, OR THAILAND 



57 



interesting habits. In Thailand it abounds in the rivers, canals, and 

 swamps of the central plain and is one of the best-known fishes, always 

 rendering itself conspicuous by its habit of coming to the surface, mak- 

 ing a splash, rolling over, and exposing its broad silvery side. 



A length of more than a meter is attained in India, the greatest 

 length reported in the Indo-Australian Archipelago is 87.5 cm., and 

 fishes a meter long have very rarely been observed in Thailand in 

 recent years, the size usually being TO to 75 cm. 



Thai examples of N otoyterus chitala always exhibit a longitudinal 

 series of black spots on the side above the anal fin, each spot often hav- 

 ing a well-defined white ring around it. The spots number from 5 to 

 10 on each side, and there may be a difference of 1 or 2 spots on the two 

 sides of a given fish. This color phase in Siamese fishes is in strong 

 contrast with that observed in fishes in the Indo-Australian Archi- 

 pelago, which are usually immaculate, although Weber and de Beaufort 

 state that rarely there is a series of 4 or 5 black spots in the caudal 

 i-egion. 



Figure 1. — Notopterus chitala (Hamilton). Drawn by Nai Chote Suvatti; courtesy of the 



Thailand Government. 



By the time the young have reached a length of 3 to 3.5 cm., 10 to 15 

 blackish or dark gray cross bands appear; at a length of 7 to 8 cm., 

 when the fishes are about 70 days old, a dark brown rounded or elliptical 

 spot appears at the lower ]3art of each of the posterior cross bands; with 

 further growth the cross bands begin to grow faint and finally dis- 

 appear, while the spots become more intense and persist throughout 

 adult life. 



Noto'ptei'us chitala subsists on insects, shrimps, and especially small 

 surface-swimming fishes, including the halfbeak Zenarchoptenis 

 ectuntio (Hamilton), the archerfish Toxotes jaculatiix (Pallas), and 

 various cyprinoids. 



This fish has unique spawning habits, which have been made known 

 chiefly by assistants of the Siamese Bureau of Fisheries. Writing of 

 the notopterid fishes in the Cambridge Natural History, Fishes (1904, 

 p. 555), Dr. Boulenger recorded that "nothing is known of their breed- 

 ing habits and developments," and Dean's Bibliography of Fishes 



