OYSTER-BED SURVEY

Press, Volume CI, Issue 29844, 9 June 1962, Page 18

OYSTER-BED SURVEY

Foveaux Strait Findings

Oysters in Foveaux Strait are found almost entirely on a certain type of bottom within a certain depth range, says Mr D. J. Cullen, of the New Zealand Oceanographic Institute, in the “New Zealand Journal of Geology and Geophysics." His study is based on bottom-sampling carried out in the strait two years ago by the New Zealand Oceanographic Institute, Department of Scientific and Industrial Research, from the motor vessel Viti.

The main oyster-beds, says Mr Cullen, occur almost entirely where the bottom is a mixture of smallish pebbles and medium to coarse shelly sand. Shell debris averages about 40 per cent, by weight of the total sediment in this type of bottom. The oysters are restricted, with few exceptions, to depths between 10 and 25 fathoms.

“The pebbles and larger shell fragments presumably provide surfaces for the attachment of spat (spawn) while the interstitial sand affords a firm, level base upon which the mature oyster can develop,” he says. The sandy gravel owes its “peculiar composition,” in part at least, to the strong tidal currents that scour the strait. Fine rock detritus and shell are continuously swept away, while the sediment is replenished by coarser fragmental shell from the oysters and other shellfish.