REPORT ON OCEANOGRAPHY 25 



(v) Sea mullet (Mugil cephalus). Attention is still being given to 

 the possibility that the eastern and western Australian stocks are being 

 overfished, but the most recent work is somewhat reassuring. 



(vi) Scallops (Nutovola meridiojialis). The stock of the D'Entre- 

 casteaux Channel, Tasmania, is declining, apparently by natural fluc- 

 tuation. Biological observations were made by diving. 



(vii) School Shark (Galeorhinus australis). Tagging experiments 

 revealed the existence of a single large stock in southeastern waters. It 

 is declining under fishing and conservation measures have been recom- 

 mended. Growth and reproduction rates are slow. 



(viii) Tiger flathead {Neoplaty cephalus macrodon). The study of 

 this species was continued, with special attention to growth and recruit- 

 ment. Availability has greatly declined over the last thirty years of 

 intense trawl fishing on the east coast, depleting is presumed, and con- 

 servation measures have been recommended. 



(ix) Whitebait (Louettia seali). Two stocks of this small anadro- 

 mous salmonoid were identified in Tasmanian waters. One now ap- 

 pears to be depleted after heavy fishing and the other is under-ex- 

 ploited. 



(x) Other fishes which are being studied include Nemadactylus ma- 

 cropterus. Trachichthodes ajfinis, Mylo australis^ Cybium commersoni, 

 Chrysophyrs auratus, Arripis georgianus and the elasmobranch Emissola 

 antarctica. 



C. Acclimatization and culture of stocks:— 



(i) Japanese oyster (Ostrea gigas). This species was successfully 

 acclimatized, to the point of good growth and reproduction, in Tasma- 

 nian waters. Further importations are being made. 



(ii) East Coast rock oyster (Crassostrea commercialis). Work to 

 improve the already efficient oyster culture of New South Wales wa- 

 ters has been continued and efforts have been made to introduce oys- 

 ter culture into other areas. 



(iii) Pearl oysters (Pinctada spp.). The possibilities of culture are 

 being investigated in Torres Strait. Growth and reproduction of oys- 

 ters of natural beds are being studied as a prerequisite. 



(iv) Introduced freshwater trout (Salmofario and 5. iridens). The 

 possibility of maintaining certain populations without further planting 

 of hatchery stock is being investigated. 



(v) Enrichment of inland waters. A substantial flora and fauna 

 was developed in a barren mountain lake as a result of addition of nu- 

 trients. It is now intended to study the effect of the introduction of 

 fish. 



