|Scientific Name:||Paragalaxias mesotes|
|Species Authority:||McDowall & Fulton, 1978|
|Red List Category & Criteria:||Vulnerable D2 ver 3.1|
|Assessor(s):||Jenkins, A., Kullander, F.F. & Tan, H.H.|
|Reviewer(s):||Collen, B., Darwall, W., Ram, M. & Smith, K. (SRLI Freshwater Fish Evaluation Workshop)|
Assessed as Vulnerable as this species is restricted to only one location. This may increase to two locations, depending on whether the transloction of this species to Woods Lake is successful. It is possible that the decline of P. mesotes may have halted due to the many conservation measures in place to protect this species, however, due to this species' restricted Extent of Occurrence and Area of Occupancy, any future decline in habitat quality or future habitat loss would result in this species being classified as Critically Endangered. This species and its habitat therefore requires close monitoring.
|Range Description:||This species is endemic to Tasmania, Australia. It was previously restricted to Arthurs Lake and Woods Lake on Tasmania's central plateau (Allen et al. 2002), but today only the Arthurs Lake population remains (DEH 2005). Despite extensive survey effort over the last decade, the species has not been recorded in Woods Lake since 1989.
When P. mesotes was found in both Woods and Arthurs Lakes, its area of occupancy was estimated to have been approximately 75 km². Based on the likelihood that the species no longer occurs in Woods Lake, its area of occupancy has declined to approximately 62 km². Additionally, the species' extent of occurrence was previously estimated to be approximately 180 km², but following its apparent disappearance from Woods Lake, the extent of occurrence for the Arthurs Paragalaxias is estimated to have declined to approximately 87 km² (DEH 2005).
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The species has a stable trend, although detailed numbers are not known.|
|Habitat and Ecology:||P. mesotes is a demersal species that inhabits lacustrine habitats near the shore, amongst rocks or vegetation, down to a depth of 4-5 meters. It is also found in pools of outlet streams. Little is known about the biology of this species (Allen et al. 2002).|
Habitat quality and availability for P. mesotes fluctuates in both Woods and Arthurs lakes as water levels change due to extraction for irrigation and hydroelectricity. Although the exact spawning habitat of this species is not known, other galaxiid species deposit eggs under rocks in shallow waters. These shallow areas are often subject to drying, and given that rocky areas occur around the shore in Woods Lake, it is possible that a slight drop in water level may expose a large width of shoreline, potentially displacing fish from important breeding habitat. Low water levels are also linked to high turbidity as a result of wind-driven sediment disturbance. Over the past decade, Woods Lake has experienced two events of extremely high turbidity, one in 1995 and one in mid 2000. High turbidity is considered to increase the risk of harmful algal blooms and fish gill erosion, which has the capacity to cause high mortality among fish populations (DEH 2005).
It is likely that Brown Trout (Salmo trutta) have been present in Woods Lake for over a century. Whilst they are likely to prey on P. mesotes, the degree of predation is not known. Given that the species remains common in Arthurs Lake, which also contains Brown Trout, it is unlikely that predation pressure alone is the cause of the species decline in Woods Lake (DEH 2005). Rainbow trout is also present in both Arthurs and Woods lake (McDowall 2006).
The two populations were fragmented by the construction of Arthurs Dam in 1965, which totally blocks flow from Arthurs Lake to Woods Lake under normal conditions. Movement of fish would probably have been in the downstream direction (Jackson 2004).
The species is currently listed as endangered under the Tasmanian Threatened Species Protection Act 1995. In response to this, the Tasmanian Inland Fisheries Service has produced a recovery plan for this, and other, Galaxiidae species (Jackson 2004).
The Tasmanian Inland Fisheries Act 1995 prohibits collecting of any freshwater species without permit. P mesotes is a ‘priority species requiring consideration’ under the Tasmanian Regional Forest Agreement 1997, identified as requiring further research to determine its management requirements. Arthurs and Woods lakes and their fish populations are included in technical studies being conducted by Hydro Tasmania for development of a Water Management Plan under the Water Management Act 1999 (Jackson 2004).
An informal minimum lake level agreement between Inland Fisheries Service (IFS) and Hydro Tasmania since 1995 is intended to keep the lake above a minimum water level of 735.40 meters above sea level to reduce the risk of high turbidity events. A minimum lake level agreement in place for Arthurs Lake to maintain angling amenity also reduces the potential for extensive habitat dewatering (Jackson 2004).
P. mesotes was reintroduced to Woods Lake in late 2002, with 174 individuals released at two adjacent rocky sites (Jackson 2004). What had changed to make it possible for the translocated fish to survive in Woods Lake any better than the previously resident stocks that had disappeared is unclear, as are the results of the transfer (McDowall 2006).
Future conservation strategies include habitat management, monitoring of populations, trout management, genetic research and communication. Research into the habitat requirements and life history of P. mesotes is needed to determine appropriate habitat management, particularly of water levels. Woods Lake requires monitoring designed to determine whether the reintroduced fish establish a breeding population there (Jackson 2004).
|Citation:||Jenkins, A., Kullander, F.F. & Tan, H.H. 2009. Paragalaxias mesotes. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 03 September 2015.|
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