3. The River-mouth Problem 



The estuaries of the tropics, or at any rate those of South-east Asia;, 

 show pecuHarities which are not found in colder chmates. 



In front of each river mouth a horse-shoe shaped bar exists not 

 consisting of sand, but of very soft mud. In this bar no channels are found 

 as would be the case, for instance, in European rivers. This soft, muddy 

 bar is maintaining itself, notwithstanding the fact that heavy tidal 

 streams, sometimes up to 5-6 nautical miles an hour, flow over it twice 

 a day. This bar ends abruptly and very steeply to the landward and has a 

 \'ery gentle slope to the seaward. The result is a peculiar distribution 

 of the salinities, water of high salinity, flowing over the bar at high tide 

 as a kind of submarine waterfall, is captured behind the bar at low tide, 

 and remains more or less stagnant on the bottom of the river proper. 

 These rivers, coming from a very flat and marshy country, have a very 

 slow fall, and the sea-water (more or less diluted) is often found tens of 

 kilometres inland. 



In these waters a peculiar and very special fish fauna is found, 

 consisting of species (and even genera) spending their life cycle in these 

 waters with varying sahnities. This fauna does not live elsewhere. 



The number of species is, for a tropical community, low, the number of 

 individuals very large, probably due to the high amount of plankton in 

 these fertile waters. The plankton growth is much more abundant than 

 in the open sea. 



I am sorry to say that all notes and collections are lost. 

 List of English Publications Since Jan. 1, 1939 



Dam, L. van : Estimation of Chlorides in 1 c.c. Sea Water Samples by Cleans of 

 Syringe Pipettes. Treubia, deel 17/5, 1940. 



Dklsman, H. C. : Preliminary Plankton Investigations in the Java Sea. Treiibia, 

 deel 17/2, 1939. 



Hardenberg, J. D. F. : Some New or Rare Fishes of the Indo-Australian Archi- 

 pelago : VII. Treubia, deel 17/2, 1939. 



— — — Fishes of New Guinea. Tretibia, Vol. 18/2, 1941. 



■ Development of Marine Fisheries. Roval Asiatic Society of Bengal. Science, 



Vol. XII/2, 1947. 



— Some New or Rare Fishes of the Indo-Australian Archipelago : VIII. Treubia 



Vol. 19/3, September, 1948. 



Jong, J. K. de : A Preliminary Investigation of the Spawning Habits of Some 

 Fishes of the Java Sea. Treubia, deel 17/4, 1940. 



AN OUTLINE OF THE WORK OF THE OCEANOGRAPHIC 

 INSTITUTE OF INDO-CHINA from 1939 to 1948 



By R. Serene, Oceanographic Institute of Indo-China 



At the Fifth Pacific Science Congress a resume was presented of the 

 work of the Oceanographic Institute of Indo-China during the period 

 1929-1933 ; at the Sixth Congress a resume of that carried out between 

 1934 and 1939. The period 1939-1948 is that of the war, the 

 unfortunate effects of which are still being felt. 



M. Chevey, the Director, died in 1942 ; from 1943 to 1946 the labora- 

 tory was closed, and even during the period from Juty, 1945, to April, 

 1946, entirely abandoned and given over to piUagers. In April, 1946, 

 M. Serene assumed responsibility for the place, but found neither staff 

 nor equipment ; the task of reconstruction and re-equipment absorbed 



192 



