.9 



larly those frequenting the tidal rivers. Unfortunatel}' no con- 

 tinuous and reliable statistics are available, but theie can be 

 little doubt that this has occurred in the case of the Snoek, and 

 the balance of evidence at least indicates that it has happened 

 also in the case of other and more stationary fish. 



The procuring of reliable statistics or other evidence of 

 fluctuation is a primary requisite, but of not less importance, 

 though less easily procured, is a knowledge of the true cause 

 of such fluctuation. Very great damage may be, and, in some 

 cases, probably has been done to the development of the fishing 

 industry by dealing with the wrong source of the trouble. In 

 countries such as South Africa, where primitive methods of 

 fishing are giving place to more modern methods, the latter 

 are, naturally enough, first condemned by the native fishers as 

 the cause of the decreased supply. Whether, therefore, the 

 cause is one which can be removed by legislation, or whether 

 it lies in some uncontrollable physical or biological phenomena, 

 it is of the utmost importance to ascertain its true nature as 

 far as possible. 



The object of this enquiry is : (i) to review the various 

 causes alleged to be responsible for a diminished fish supply 

 in South Africa, and to endeavour to estimate to what extent 

 they are valid ; (2) to direct attention to a possible cause of 

 general and extensive diminution of the fish supply, peculiar 

 to certain conditions in South African seas. 



These alleged causes have been many and varied. They 

 are as follows : — 



1. Running of trains. 



2. Firing of guns. 



3. Use of dynamite. 



4. Increase of shipping. 



5. Netting in tidal rivers and lagoons. 



6. Sea birds, particularly " Duikers." 



7. Seals, Porpoises and Sharks. 



8. Escape of injurious matter from wrecks, 

 g. Fresh water in tidal rivers. 



10. Use of American purse-net. 



11. Trawling. 



12. Capture of immature fish. 



13. Red water. 



14. Obscure causes, such as earthquakes, cold currents, etc. 



I. The fishing stations in False Bay (Gordon's Bay, Somerset 

 Strand, Muizenberg, Kalk Bay, Fish Hoek and Simon's Town) 

 are among the oldest and most important centres of the Fishing 

 Industry in the Cape Province. Some thirty years ago the 



[C.P. 6-'i4.] 



