Research in Australian Sea Fisheries

Abstract

PROF. W. J. DAKIN in his R. M. Johnston Memorial Lecture (Pap. and Proc. Roy. Soc. Tasmania for 1934 (1935)) gave a brief survey of various fisheries in all parts of the world and the methods of investigation. Then he proceeded to outline the needs of Australian fisheries. A beginning has been made hi different directions, notably with age determinations and biology of the important commercial fish of New South Wales, the tiger nathead. Investigations are also being made into the life-histories of certain fishes and their eggs and larvae, especially the Australian pilchard. Among the plankton studies one of special importance relates to the biology of the peneid prawns, the life-history of which is now being worked out by Prof. Dakin. The best-known prawns there are the king prawn, Peneus plebejus, and the school prawn, Penceopsis macleayi. During the winter, few or no prawns can be taken with nets and those captured are usually small; but in spring there comes a time when the king prawn can be caught in the lakes, and those first taken are small and come from the end farthest from the sea. Later, larger specimens are caught and then enormous outflows or ‘runs' of large prawns take place on dark nights. The prawns flock to the entrance connecting the lake with the sea and can be captured in huge quantities. These large prawns are all immature and not quite fully grown, and it is now known that they are migrating to the sea in order to breed there. The eggs are shed in the open ocean and hatch as nauplii, the young migrating into the lakes there to feed and grow. The large prawns migrating to the sea from the lake are less than a year old?a most interesting life-history,, and published here for the first time. Penceopsis monoceros appears to be exceptional in laying its eggs in the Swan River at Perth.