In working auriferous river-beds, dredges have been used with considerable success in certain parts of New Zealand and on the Pacific slope in America.
Some dredges have a capacity under favourable conditions of over 2000 cub.
In South Island the river-beds of Otago province have been successfully worked by means of dredges, and good returns secured.
Limestone is abundant, and the city has various manufactures, including lime, foundry and machine-shop products, agricultural implements, planing-mill products, engines, steam shovels, dredges, pianos and silks.
The oyster fisheries give employment to over 56,000 fishermen, who man 4000 vessels, valued at $4,000,000, and 23,000 boats, valued at $1,470,000; the value of the 1 i,000 dredges and 37,000 tongs, rakes and other appliances used is $365,000.