BARREN OYSTER BOTTOMS 65 



SESSIONAL PAPER No. 38a 



Large starfish were obtained in the dredge from the beds in the deep water and 

 great numbers of young starfish were found in certain parts of the eel-grass-covjred 

 sand areas. Many of the fishermen are not yet convinced of the fact that a starfish 

 torn in two and thrown back into the water grows into two starfish. 



A boring sponge (Cliona celata Grant), for the identification of which the writer 

 is indebted to Lawrence M. Lambe, F.G.S., occurs on some of the beds, more par- 

 ticularly in the mud areas. Fortunately one finds only a small percentage of shells 

 attacked. This sponge, however, does considerable damage to the oysters which it 

 attacks. Although it may not kill the oyster it weakens it by forcing it to expend 

 its energy in repairing the shell, which is almost honeycombed by the sponge. The 

 weakened shell leaves the oyster a much easier prey to its other enemies. 



The drill (Urosalpinx cinera Say) is not known to occur in Richmond bay, 

 although there is a small borer (Tritia trivittata Adams) which does penetrate the 

 soft shells of Pandora trilineata Say, and which may possibly do damage to small 

 oysters. It is very abundant in some parts of the bay. 



The slipper limpet (Crepidula fomicata Lamarck) is very abundant and must 

 come into competition with the oyster for points of attachment and for food. Crepi- 

 dula plana Say, also occurs. 



Eel-grass (Zostera marina L.) renders areas unfit for planting oysters until it is 

 cleared off, smothers oysters when it is dead by lodging on them, and interferes with 

 the setting of oyster spat, as will be pointed out in the account of the experiments on 

 spatting. Certain seaweeds also grow on the rocks and interfere with the setting of 

 spat here. 



Ice, it is stated, destroys many young oysters on such points as those to the north 

 of Grover and Bunbury islands. Many of these would doubtless be saved were these 

 points leased. If leased to fishermen they could carry on operations here without the 

 outlay of much capital. Clean cultch could be distributed over these points in 

 retainers such as those used in our spat-collecting experiments, and these could be 

 lifted and sold to the oyster companies before the ice formed in the autumn. 



No doubt some oysters are destroyed by sifting sand, but it does not yet appear 

 that the loss from this source is very great. 



Sudden falls of temperatures such as that on the night of August 24 no doubt 

 destroy great numbers of the oyster fry. That even such great drops as this do not 

 destroy all is shown by the fact that spat set in several places after that date. 



The most destructive enemy the oyster has, however, is man. Oyster poaching 

 goes on widely, but were the oyster poacher and the man who buys from him severely 

 dealt with, and efficient protective legislation effectively and impartially enforced, 

 there would be a great advance in the oyster industry in Richmond bay. 



OCCURRENCE OF SMALL 9YSTERS AS EVIDENCE OF SPATTING. 



The small number of young oysters shows either that spatting has not been good 

 in recent years or that there has been a high death-rate among the small oysters. 

 There is almost always, however, a good or at least a fair " set " in a few places such 

 as the north point of Grover island, on the Curtain Island shoals, and in the narrows 

 between Curtain island and the mainland. There is also generally a fair set in the 

 Grand river and often near the mouths of the Indian and Barbara Weit rivers at the 

 south end of the Big bay. There was a very light set in 1913. A few 1-year-old oysters 

 occur at Grover i^and, in the narrows, and near the mouth of the Barbara, Weit 

 river. Two-year-old oysters were more abundant and more widely distributed. Small 

 oysters up to 3 or 4 years old were found in the narrows, on the rocky shoals near 

 George island, the roclcy points north of Grover and Bunbury islands, the Grand river 

 and at various points in the Big bay. Spatting does take place, and there is no doubt 

 in the writer's mind that it would take place more abundantly if precautions were 



38a— 5 



