15 



diminution in the fish supply, as these animals, even more than 

 the fishermen are dependent for their livelihood on an adequate 

 supply of fish. 



Porpoises on the east coast cause considerable damage to 

 the fish supply, and sharks everywhere do the same. Por- 

 poises are troublesome, particularly at Durban, and it has been 

 found that if a few are shot and wounded they make for the 

 open sea, taking all the others with them and there is no more 

 trouble for some days. 



8. The escape of injurious matter from wrecks is known to 

 have caused more or less extensive destruction of fish. The 

 best example of this is an occurrence which took place at 

 Knysna. The Knysna harbour, or lagoon, is a large sheet of 

 water, much smaller than Saldanha Bay, but, like it, shut off 

 from the sea except for a comparatively narrow opening. On 

 one occasion a ship, containing creosote for the sleeper factory 

 there, was wrecked, and the oily substance escaped, spreading 

 out on the surface of the lagoon. The effect was very marked, 

 nearly all the living animals in the water being killed off. 



9. An undoubted cause of the destruction of fish is the 

 presence of fresh water in tidal rivers and lagoons. For in- 

 stance, in October, 1904, a sudden and great fall of rain oc- 

 curred after a period of drought in the Eastern Province and 

 the whole of the sea water in the Zwartkops River, from the 

 ebb and flow to the mouth (a distance of about six miles) was 

 driven out to sea. After the subsidence of the water, many 

 dead sea fish were found, and a large number of Cuttlefish, 

 which live in the grassy salt-water pools of the river. Such an 

 occurrence is said to be not uncommon in this region, and has 

 been even more marked in the case of great floods in the other 

 rivers of the east coast. At Knysna the fishermen expect an 

 influx of sea fish after such an occurrence as Kabeljauw and 

 other fish come in to devour the dead Cuttlefish. Cases of 

 destruction of sea fish by fresh water are not unknown in other 

 parts of the world. 



A curious method of stating the same fact is the apparently 

 anomalous allegation that the decrease of fish in Soutli Africa 

 is due to the increase of jackals, and that in the following way. 

 Increase in the number of jackals necessitates the protection 

 of sheep in a kraal during the night. The constant passing of 

 the sheep to and from the kraal causes the gradual formation 

 of more or less well-trodden paths ; by these paths the surface 

 water flows off more quickly, deepening them, so that deep 

 sluits are ultimately formed ; by these, the water, instead of 

 soaking down into the surface of the ground, flows away 

 quickly into the rivers, which are thus, in heavy rains, flooded 



[C.P. 6-'i4.] 



