OYSTERS AND OYSTER FISHERIES OF QUEENSLAND. 255 



quality. Like those growing on the reefs, they are well adapted for separation and cultiva- 

 tion on the banks, though the tenacity with which they adhere to their rocky basis involves 

 considerably more care and labour in their detachment. 



What are known as "Mangrove" oysters, represent an important item in the Queensland growth- 

 conditions of Ostrca glomerata. These are the oysters with which there originated the supposed 

 travellers' tales, of earlier days, concerning oysters growing upon trees. The most typical and 

 commercially important phase of mangrove oyster-growth, is represented by those instances in 

 which the oysters affix themselves to the exposed roots and respirator}- shoots, or so-called 

 "cobblers'-pegs," of the white mangrove, Avicennia officinalis. By the process of accumulation they 

 may increase, under these conditions, to such an extent as to constitute, where most favourably 

 circumstanced, massive banks, scarcely less prolific than the typical reefs previously described. 

 Such a mangrove oyster-bank in its most perfected luxuriance is illustrated by Plate XXXIX., 

 representing a view taken in Keppel Bay. When growing in the prolific manner here represented, 

 these banks constitute, as in the case of the typical reefs previously described, valuable material for 

 segregation and artificial cultivation on the spot. 



A second, and somewhat less prolific, variety of mangrove oyster-growth, is that in which the 

 species is found attached to the luxuriantly ramifying aerial roots of the red or orange mangrove, 

 Rhizophora miicroiiafa, as illustrated in Plate XXXIX. Oysters on this description of mangrove 

 more commonly occur in the northern area of distribution of the species ; and in such localities 

 as the mouth of the Endeavour River, near Cooktown, and at Bowen, Port Denison, constitute 

 the almost exclusive representatives of the genus. This mangrove oyster occurs also in some 

 abundance in certain parts of Wide Bay, such as the vicinity of the South Head. In consequence 

 of its adaptation of contour to its supporting fulcra, this oyster is apt to develop a very 

 irregular form of growth ; if, however, it be moved at an early stage of its existence, and spread 

 out under favourable conditions for culture on the banks, it has been found by systematic 

 oyster-growers to well repay attention. This being the experience gained on the Wide 

 Bay oyster-grounds, it may be anticipated that successful results would also accompany a like 

 treatment of the variety, in its natural habitat, farther north. This anticipation is supported 

 by the circumstances that oysters of larger, edible, dimensions and quality are to be gathered 

 among the fallen debris lying around the mangrove trees, where, living more or less remote 

 from one another, they have room for their shells to expand. Giving due weight to this fact, the 

 author is of the opinion that remunerative banks, productive of oysters in at least sufficient 

 quantities for local consumption, might be initiated, with stock derived from the mangroves, in 

 these more northern districts. In the establishment of such experimental banks, attention should 

 be given to imitating as nearly as possible Nature's own pattern, the banks being formed, not on 

 open sun-exposed flats, but within that umbrageous shelter of the mangrove trees where the species 

 attains to its finest development in these higher latitudes. The conditions above indicated obtain, 



