THE OYSTER EISHERIES. 63 



a large scale, have been at work too on lines inimical to 

 ostreal development ; that development is, to a great extent, 

 dependent on the proportion of salt held in the water in 

 which the oyster occnrs ; if that proportion be materially- 

 exceeded or decreased the food producing conditions will be 

 disturbed, development will be retarded, and the oyster will 

 cease to grow, or perhaps die right out. 



Now, during several years past, New South "Wales has been 

 experiencing a succession of droughts more or less severe, 

 and during the same period her oyster-beds have been 

 suifering depletion to such an extent that while in 1883 they 

 yielded the comparatively large supply of 46,377 bushels, in 

 the present year, 1891, they have produced only 14,181 

 bushels. Now, a connection is to be easily traced between 

 these periods of drought and oyster depletion. Oysters on 

 our seaboard occur under two distinct features of location, 

 viz., on beds in depths of water ranging to six or more fathoms 

 (popularly known as deep-water beds), and on the shore 

 between low and high water mark (distinguished as foreshore 

 deposits) . 



The deep-water beds have always held a special value by 

 reason of the superiority of their produce over that of the 

 foreshores. Now, fresh water being a condition essential to 

 the growtli of the oyster, the question arises, how can it with 

 its lesser specific gravity reach these deep beds. It is obvious 

 that it must reach them by some other means than from 

 the surface, and the readiest solution is that it is conveyed 

 from the surrounding country by subterranean courses along 

 and under the floors of rivers and inlets, and wherever it meets 

 with porous soil it wells up, and mingling with the salt water 

 creates one of the conditions necessary to oyster growth; 

 and in such places the spat, which, as has been stated, is 

 distributed in lavish profusion, falls, and a deep-water bed is 

 formed. With the progress of the droughts this supply of 

 fresh water would begin to fail, and with it the food supply, 

 and eventually ceasing to flow at all, the oyster, as a con- 

 sequence, would have to succumb and give place to forms 

 of marine life and vegetation, which could not pre\dously 

 exist. This theory was in part practically illustrated at the 

 Clarence Hiver, in one of the estuaries, in which sponge and 

 other submarine growth had completely overcome an oyster- 

 bed. A flood subsequently occurring and the estuary being 

 shallow, the water coming down in large volume affected the 



