The Russian fishing trailer SESKAR cruised the ported beyond the boundaries of the shoals. 

 South China Sea from January through March 1964. 



A. I. Ch ig irinsk iy and Yu. M. Maksimov observed The tropical Australian and Asian Seas are most 

 about 70 snakes and collecteH 75 specimens belong- favorable for sea snakes. In addition to many shoals 

 ing to 7 species. V. G. Csipov, when cruising the an d gulfs, there is an abundance of fish and invert- 

 South China Sea and East Indian Ocean in November ebrates in the seas, on which the sea snakes depend 

 and December I963 and January through March 1964 on for food. Because of these facts, this region has 

 the fishing trawler ORL IK, observed about 100 sea become a center of abundance of qualitative and quan- 

 snakes. These specimens were processed by the Pac- titative of sea snakes (as to the latter cause, one 

 if ic Research Institute of Marine Fishery Manage- must also take into consideration historical rea- 

 ment and Oceanography in Vladivostok. sons;. 



Data of all the counts of sea snakes have been At our disposal were only 75 snakes obtained 



reduced to one denom i nator--the number of individ- f rom several stations in the Gulf of Siam. There- 



/ 1883 / fore, it is impossible to plot distribution schemes 



uals observed per hour when the speed of the ves- for '"dividual species because the absolute number 



sel is 10 knots (Figs. 1, 2, 3). °f species cannot be estimated by visual observa- 

 tions. The only exception is Pelam i s pla turus . 



It is known that sea snakes gravitate in their which is a unique color and can be readily identi- 



distribution toward shallow coastal areas. The f ' ed at a greater distance. In the Gulf of Siam area 



distribution of sea snakes presented in Fig. 1 con- tn ' s species was m0 st numerous (Fig. 3), making up 



firms the above statement. Indeed, most of the 55* of the snakes, 

 samples taken from the open water of the East China 



sea, in the central part of the South China sea and 0ur observations conducted in I96I in the Gulf 

 northeast of the Philippine Islands did not contain of Tonkin (Shuntov, I962) demonstrate that in the 

 any sea snakes at all; whereas the sample taken °P en sectors of the Gulf, P. platurus was also most 

 from the southern belt of the South China Sea, not- numerous of the snakes. Of several tens of samples 

 ably in the Gulf ofSiam, as well as between Sumatra examined by V. G. Osipov in the Indian Ocean (main- 

 and Kalimantan Islands, contained many sea snakes. l y ° ver great bottom depths at distances exceeding 

 Out of 45 samples, 38 contained snakes. In 15 5°-7° miles from the coast) only 10 samples con- 

 samples the number of snakes varied from 1 to 5; tained snakes, 8 of which consisted of only P. 

 in 10 samples from 5 to 10, and in 11 samples from ' 1885 / 



10 to 25 snakes per hour of trawling with the speed platurus. The absence of this species from samples 



of the vessel being 10 knots (Fig. 2). Because the taken in the extreme south of the South China Sea 



snakes are expert divers and spend considerable betweei Sumatra and Kalimantan Islands was unexpec- 



time under water, the listed figures indicate only ^ e ° v * ' 9 - 3J- 

 their relative quantity in these areas. Also in 



the Gulf of Tonkin, north of the Gulf of Siam, the ln the Guli of Tonkin, P. platurus inhabits 



number of sea snakes was considerable (according to waters where the salinity exceeds 32$. Therefore, 



our observations conducted in 1961). the quantity of these snakes sharply decreases in 



the NW part of the gulf where the water is diluted 



The number of samples taken from the Indian b y rivers. Off Hainan Island, however, where the 



Ocean is, of course, too small for the elucidation water is quite saline, P. platurus is found in the 



of regularities in the distribution of snakes in littoral water (Shuntov, I962). In the Gulf of Siam 



this vast area. However, the data listed in Fig. 1 the species is more widely distributed than in the 



show quite clearly that in the open ocean the ' Gulf of Tonkin. The possible reason for such a 



snakes are seldom seen. Here they usually are ob- distribution is the river discharges at the tip of 



served not farther than 6O-7O miles from the coast- the 9 ulf ' Ho " ever > ]i has not Y et been established 



line. Only on December 7 1963 were four individu- how the dilution affects the distribution of P. 



als of Pelamis platurus observed in the central Pl at urus because no observations have been conducted 



sector of the ocean about 8OO-85O miles from Ceylon north of 12 ° N - 

 land Sumatra. 



Other species of snakes were less often obser- 



j H84 / ve d 'n the given areas; out of 75 snakes caught in 



As a rule, the snakes are encountered in places the Gulf °] Siam » £• £ latur us made up 53, Astrotia 



with bottom depths less than 90-100 m. The main stokessl ' ( G ray) 8, Lapemis hardwicki 1 Gray 4, 



mass, however, is limited to depths less than 75 m. Hydrophis spiralis Shaw 3, Praescutata viperma 



This is conspicuously confirmed by the character of (Schmidt) 3, Hydro phis fasciata Guenther 2, Micro- 



distribution of sea snakes in areas with shoals of cephalophi s cantoris Schm. 2 individuals, 

 varying sizes. Where the shelf is narrow, the 



snakes are seldom observed at a distance of several ' n the southern South China Sea and in the Gulf 



tens of miles from the coast. However, in the Gulf of Siam » several observations were conducted in 



of Tonkin and in the southern South China Sea, where various seasons. This enables us to conclude roughlv 



the shelf is very wide, sea snakes occur in large about the migrations of snakes. Yu. M. Maksimov ob- 



numbers at distances of 70-100 miles off the coast served concentrations of snakes in the eastern part 



(Fiqs. 1 and 2). °f * ne Gulf of Siam and in the southern part of the 



sea between Sumatra and Kalimantan Islands at the 



Especially large numbers of snakes are observed beginning of Feburary 1964. V. G. Osipov had obser- 



in shallow gulfs. The reason for this is that in ved such concentrations by the end of 1963 in the 



places with very indented coastal line, the currents same areas. Snake concentra t. ons in these areas 



create eddy circulations which help keep mature w ere considerable at the end of March 1964 (see 



snakes (which are not good swimmers) in a definite Figures 2 and 3). In the Gulf of Siam area one 



location and prevent the young from being trans- could observe migration toward the gulf. In a num- 



