Historic drift bottle experiments show reversing surface water masses in western Bass Strait waters: Implications for lobster larval dispersal

From 1958-1962, 166 batches of 50 weighted drift bottles were released at four stations in western Bass Strait waters to estimate current strength and transport distance of on-shelf waters; 2120 bottles were recovered from 122 batches. Bottles were transported up to 1570 kin from release sites at mean speeds of up to 28 cm s(-1). The direction of transport showed the presence of seasonally reversing surface waters, which flowed to the west/northwest during summer and to the east/southeast during winter, with some interannual variation in timing of the reversals. Present knowledge of coastal circulation is consistent with drift bottle results. We suggest that larvae of the western population of the rock lobster, Jasus edwardsii, hatching in October in western Bass Strait waters can be transported westerly as far as the eastern Great Australian Bight, and returned to their natal region 9 months later. However, larvae hatching on the west Tasmanian coast may be variously transported offshore, northwards or southeast, before settling in coastal waters.