PORTOBELLO MARINE FISH HATCHERY.

Otago Witness, Issue 3430, 9 December 1919, Page 25

PORTOBELLO MARINE FISH HATCHERY.

AN INTERESTING EXPERIMENT.

Two epecies of oysters are marketed in New Zealand —the so-called mud oyster (Ostrea angasi), which is found right round the shores of both islands, but is especially common in the South; and a (0. glomerata), which only occurs in the northern part of the North Island. Th 4 first-named species forms extensive beds in Foveaux Strait and near Stewart Island, at an average depth of about 15 fathoms, and these are regularly -worked by dredging from February to September of each year. This species is now widely known as the Stewart Island oyster, though, of oouree, it is not confined to that locality. Ostrea glomerata is the Auckland rock-oyeter, which is gathered from May to September, and the farming of which is a Government monopoly. In addition to these two, there are three other species of oysters in New Zealand waters, and one of these. Ostrea tatci, is a common rock-oyster in Otago Harbour and along the east coast of this island. ' In edible properties it is quite as good as either of the marketed species, and it is only because it is not found in great quantity that it is not brought into public favour. An experiment is now being started at the Portobello Fish Hatchery with the object of attempting and encouraging the cultivation of this oyster. The spawning season is now on, when the young larvae or "spat" as they are popularly called are liberated, and attach themselves to suitable supports. Numbers of these oysters have appeared in the hatchery oonds of late years, and have attached themselves along the walls just at and below low-water mark. For some months past Messrs Adams and Broadley have been preparing concrete plat« 3 on wire frames, 20in by 13in, and about an inch thick, and 56 of these have been placed in position in one of the ponds. They are suspended just below low ; water mark, and are firmly attached to rails, which form a sort of framework. Rocks and stones covered with mature oysters are being placed temporarily in the ponds, so that the "spat" on liberation will be in immediate proximity to the plates, and it is hoped the larva will attach themselves to them in numbers. It will then be possible to shift them about to any desired location. experiment is an interesting one, and it is hoped will prove of commercial value. A continuous'record is being kept at tho hatchery of the rate of growth of some of the native fishes, of which at present nearly 20 species are in confinement in the tanks. It is noted that the introduced turbot. thouerh evidently in very good health and condition, do not increase in size to any extent. Several of them are nearly two feet in length, but they have, not added to their inches for many months. This .'«. common to all kinds of fish when confined. In the open sea turbot grow to as much as three fe"pt in length, and it is hoped that those which have been liberated during the past three years have grown and liberated come millions of ova.