23 



found being a much curved shell having a total " length " (depth) of 15 inches 

 whereof the hinge region alone measured 6| inches. These shells were accom- 

 panied by a fauna notably poorer than that of the Kadero beds. The same species 

 were however represented still but in small individual number. 



95. With this visit to the Kuranji and Kadero beds my inspection 

 terminated ; the same evening I left for Bombay by the mail steamer " Linga" 



V. GENERAL CONCLUSIONS. 



96. The results of the investigation show very clearly that the Sind oyster 

 beds fall into several categories differing greatly in economic importance ; the 

 general exhaustion of the beds was verified ; the causes of depletion were 

 ascertained and sufficient information was obtained with regard to the physical 

 and biological conditions prevailing to enable us to say where and why the 

 regulations in force for years past have failed to arrest the ruin of the beds. 

 With such knowledge we are also in a position to suggest a number of simple 

 cultural operations which, if put in hand concurrently with the enforcement of 

 revised regulations, should be sufficient to restore some portion .at least of 

 Karachi's reputation as an oyster producing and distributing centre. 



97. The three categories or classes of beds met with on the Sind coast 

 may be termed respectively (a) creek beds, (6) estuarine beds and (d) backwater 

 beds. These are distinguished by separate characters and differ in several 

 important respects. The creek beds which comprise all those found in the 

 Indus creeks with the exception of the two most northern (Kurauji and 

 Kadero) are the least valuable. They are almost invariably beds of small 

 extent occurring as isolated patches surrounded and their existence continually 

 threatened by the enormous stretches of extremely soft mud forming the 

 bottom of the creeks. No cultch exists anywhere in the creeks apart from the 

 shells of the oysters themselves. As a consequence these beds labour under 

 severe disabilities ; while any increase in area is a matter of the utmost 

 difficulty, they are constantly exposed to the danger of partial or complete 

 destruction whenever any change occurs in the configuration and water 

 circulation of the creek system either from deposit of unusual quantities of 

 sediment or from 'the harmful effects caused by fresh- water floods. These 

 latter dangers affect some creeks much more than others, and we may take 

 it that while the beds in the Piti, Khudi, Khai, and Pitiani group are com- 

 paratively stable, those of Hajamro and Sisa are unreliable, frequently being 

 destroyed entirely. Even where the beds are of comparative stability, the 

 slow rate of increase, the smallness of the individual patches, their greatly 

 scattered distribution and the difficulties of access and of supervision make 

 these deposits much less valuable both actually and potentially than either of 

 the two remaining classes of beds. 



98. The estuarine beds are distinctly more valuable than those of the 

 creeks. They are at present limited to those in tiie estuary of the Bab river, 

 but till various causes eventuated in their destruction about 1890, the beds 

 which are now represented by extensive stretches of dead shells at the meeting of 

 the Kuranji and Kadero creeks would also have been included here. Such 

 beds share with those of the creeks the dangers attendant upon river floo;is 

 death from excess of fresh water and burial under deposits of silt but they are 

 much more capable of making a rapid recovery from any temporary set back 

 than are creek beds on account of the much greater area of foothold present. 

 This foothold in the case of the Hab estuary consists of rocky outcrops from the 

 river bed while at Kuranji and Kadero the bottom is thickly spread with cultch 

 composed of dead oyster shells and shelly gravel. Both localities are subject 

 to strong scour whenever heavy rain falls over the surrounding catchment area, 

 the result being that the cultch present is freed from sediment and made fit to 

 present clean surfaces for oyster spat attachment. Whenever there is a fair 

 sized bed of breeding oysters in the vicinity, heavy spatfalls occur on such 

 grounds and with a fair abundance of cultch present the resulting bed grows 

 rapidly and gives a prolific yield. 



