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The pattern of distribution of the long-spined sea urchin Centrostephanus rodgersii over ca. 40 y in the Kent group, Bass St., suggests initial establishment in the mid 1960s with subsequent expansion of populations to its current status as the dominant invertebrate on shallow subtidal rocky reef. On the east coast of Tasmania, C. rodgersii is most abundant in the vicinity of its location of initial discovery in 1978, but it occurs throughout the east coast between Eddystone Pt in the north and Recherche Bay in the south. Barrens habitat, supporting high densities of sea urchins but largely devoid of macroalgae, occurs extensively in the Kent group and at several sites on the northern half of the Tasmanian east coast, but declines with increasing latitude and does not occur south of the Tasman Peninsula. At the southern extent of barrens habitat on the open coast, barrens are incipient and occur as small patches in macroalgal beds. Evidence suggests that the barrens habitat in the Kent group and on the open rocky coast of Tasmania is formed by grazing of C. rodgersii and not by Heliociaris erythrogramma, another sea urchin that occurs on these barrens. This is largely because there is a significant positive relationship between C. rodgersii density and extent of barrens but not between H. erythrogramma density and extent of barrens, and because H. erythrogramma is not know to form barrens on exposed coast. These collective patterns suggest that the incursion of C. rodgersii into Tasmanian waters was from the north, and that spread on the east coast of Tasmania propagated from an ‘epicentre’ in the vicinity of St Helens in the northeast. We suggest that the initial incursion was via larvae transported from NSW in the East Australian Current, which has increasingly influenced the east coast of Tasmania over at least the past 4-5 decades. The lack of any genetic differentiation among C. rodgersii populations in NSW, the Kent group and the east coast of Tasmania is consistent with this view.

Item Type:	Contract Report
Keywords:	Long-spined sea urchin, Centrostephanus rodgersii, urchin barrens, lobster, abalone
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:	Environmental Policy, Climate Change and Natural Hazards
Objective Group:	Understanding climate change
Objective Field:	Effects of climate change on Australia (excl. social impacts)
UTAS Author:	Johnson, CR (Professor Craig Johnson)
UTAS Author:	Ling, SD (Dr Scott Ling)
UTAS Author:	Ross, DJ (Associate Professor Jeff Ross)
UTAS Author:	Miller, KJ (Dr Karen Miller)
ID Code:	80089
Year Published:	2005
Deposited By:	IMAS Research and Education Centre
Deposited On:	2012-10-22
Last Modified:	2012-10-23
Downloads:	3 View Download Statistics