458 EIGHTH PACIFIC SCIENCE CONGRESS 



this, in the majority of cases: "On the catches of the fisherman." And 

 it is a well-known fact, that almost any kind of fishing method is more 

 or less selective. By introducing a new kind of gear or even an altera- 

 tion in size of a certain gear type or fishing in virgin water, we may 

 have surprising results. Fish rare or unknown thus far appears now in 

 great quantities on the fish-market. We have had at Djakarta a very 

 good example as such in the sudden appearance of boat loads of Paras- 

 iromateus niger, the Black Pomfret, whereas formerly this species was 

 very rare. Not more than two or three specimens a week perhaps were 

 seen before that time. 



As far as our knowledge goes, we can divide the South East Asian, 

 seas into the following regions: 



1. Coastal waters; 



2. Shallow seas on shelf; 



3. Oceanic waters; 



4. Coral-reef waters. 



Coastal waters can be divided into smaller units. We can divide 

 them of course in waters bordering a sandy, nmddy or rocky coast. 

 These coast-forms have its influence on the fishes specially adapted to 

 the shores, like Blennius, Salarias, Periophthahnus and others. But 

 these faunas are of less importance for a general review as they are so 

 strictly bound to their environment that several different communities 

 may be found along a stretch of a few hundred meters. 



More of importance are the midwater species. They are less bound 

 to the formation of the shore as such. Generally, they are bound in a 

 minor degree to the formation of the bottom. There are species how- 

 ever, being true midwater forms, which seem to prefer a muddy bottom 

 like Sardinella species. Others like Caranx cnimenopthahnus, for in- 

 stance, like to swim above a sandy bottom. This is not a hard-and-fast 

 rule of course, but in general it is what the fishermen reckon with when 

 they go out for these species. At least this is so in Indonesian waters. 



The composition of the seawater itself is of more importance to 

 the midwater-fauna. Wherever there is a mixing with river Avater there 

 is a special fishfauna which I shall call an aestuarine fishfauna. This 

 fauna is livinGT under aestuarine conditions in some cases tens of miles 

 from land. According to my definition, aestuarine waters are therefore 

 not especially found in an aestuary as such, but are also to be met much 

 farther away. Guide species are, for instance, Setipinna, Coilia, some 

 Polynemids, Kurtus indicus, Harpodon nehereus, Trypauchen, Gobio- 

 ides and others. These species may be found in an aestuary proper like 

 in some Sumatra aestuaries, but near rivers which have no aestuary and 

 where tidal influence is small, these species are found in the rivermouth 



