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The Cataract Snail - B. launcestonensis: status, management and critical habitats


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Davies, PE ORCID: 0000-0003-2651-4061 and Cook, LSJ 2002 , The Cataract Snail - B. launcestonensis: status, management and critical habitats.

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This document reports on the findings of a project funded by Hydro Tasmania to assess the status, distribution and habitat requirements of the freshwater snail B. launcestonensis. It accompanies a report by Davies and Cook (2002) on environmental flow regime for Cataract Gorge, and together these are part of the investigations underway for the Hydro South Esk Water Management Plan.

B. launcestonensis is one of 47 species of the uniquely Tasmanian snail genus Beddomeia described to date (Ponder et al. 1993, who indicate that over 80 species, many yet to be described, are likely in total). All of these species are endemic to the state, and many are highly localised in their distribution. Many, including B. launcestonensis, are formally listed as 'rare' under Tasmanian Threatened Species Protection Act (1995), although a number of these listings are in need of review.

The Beddomeia genus belongs to family Hydrobiidae, the most diverse of all freshwater families of freshwater molluscs (Ponder et al. 1993). B. launcestonensis, like all beddomeid snails is a small freshwater snail with a shell size ranging between 2 and 4.2 mm in maximum length. It has a characteristic, somewhat globular shell shape, with a width/length ratio of 0.8 - 0.9 (Figure 1). It is part of a morphologically related group of Beddomeids which includes five other species described to date.

It is believed that B. launcestonensis was restricted to Cataract Gorge on the South Esk River. However, no dedicated surveys have been conducted to assess either its true distribution or its status either within the Gorge or outside it. There is also no understanding of its habitat requirements other than it having been observed on:
* the underside if large rocks adjacent to the channel margins in the pool formed by the weir at Deadman's Hollow (Ponder pers. comm.),
* still water in communication with the South Esk and in caverns in the Cataract, Launceston (Johnston 1879);
* First Basin Launceston (Kershaw, unpub. data, 1988)
* under stones in running water, ca 1.2 k downstream of Trevallyn Dam (41 27 57S, 147 06 09 E), under stable rocks in 0.2 - 0.5 m, and not in flow (this is station TA667 in Ponder et al. 1993).
* under large stable slabs of rock in pools and side channels off the main bed of the river (Ponder et al. 1993).

Item Type: Report (Project Report)
Authors/Creators:Davies, PE and Cook, LSJ
Keywords: Hydro Tasmania, freshwater snail, Cataract Gorge, Beddomeia
Publisher: Freshwater Systems & Hydro Tasmania
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