This lineage is known from three locations; the Hex River at the confluence with the Amandel River (De Doorns area), Breede River mainstem (adjacent to Brandvlei Dam) and Jan du Toits River, all within a single sub-quaternary catchment. These subpopulations are severely fragmented and their long term viability is highly uncertain. The Hex River subpopulation is impacted by habitat degradation and by the presence of alien and invasive fish species such as the African Catfish (Clarias gariepinus) and Rainbow Trout (Oncorhynchus mykiss). Less than 20 individuals were counted during snorkel surveys of the Amandel and Hex Rivers in 2009. The Hex River subpopulation occurs in less than 50 m stream reach. Only three individuals were captured in the Breede mainstem in 2009. This could potentially represent remnants of a once widely distributed species that has now been fragmented by the presence of alien species such as African Catfish and Bass species(Micropterus spp.) in the mainstem Breede River. The long-term persistence of the mainstem subpopulation is thus uncertain. Only two individuals were collected in a weir on the Jan du Toits River during the 2009 survey. Surveys of the Jan du Toits River are required to establish the extent of this lineage in the river. Trout has been introduced into the Jan du Toits River, thus, the long term viability of this subpopulation is uncertain. Galaxias sp. nov. 'Breede' qualifies for Endangered under criterion B because the known subpopulations are small and isolated therefore it is classified as severely fragmented and area of occupancy (AOO) is 12 km2 based on IUCN method of using 2x2 km2 grid overlay, used in this assessment (actual AOO based on riverlength is less than 5 km2). The extent of occurrence (EOO) is 147 km2 using the minimum convex polygon. Ongoing decline is occurring due to habitat degradation (bull dozing in the Hex) and from predation from alien species which are impacting the all subpopulations.
Distribution
This lineage is only known from three localities in the Breede River System; the Hex River at the confluence with the Amandel River (De Doorns area), Breede River mainstem (adjacent to Brandvlei Dam) and Jan du Toits River. There is need for surveying a small tributary of the Hex River at Karnetvlei which could potentially be the remaining stronghold of this lineage and should be prioritized for protection. More surveys are also needed to determine the status of this lineage in the mainstem Breede River, particularly targeting river sections with dense stands of marginal vegetation which could potentially provide refuge from invasive piscivorous fishes. The Jan du Toits also needs to be surveyed to establish the extent of occurrence of this lineage in the river. The presence of these three isolated subpopulations indicate that Galaxias sp. nov. 'Breede' had a much broader historical distribution range which encompassed the mainstem Breede, Hex and Jan du Toits River. The three remnant subpopulations now represent only a small proportion of this lineage’s former range.
Galaxias sp. nov. 'Breede' is represented by three subpopulations with very small known population sizes. There is urgent need for extensive surveys to determine the status of these remaining subpopulations and evaluate the need for intervention measures such as captive breeding to prevent loss. As less than 30 individuals of this lineage were recorded during surveys in 2008 and 2009, their exact numbers are currently unknown and surveys are required.
Threats
The three subpopulations are under severe threat from invasive alien piscivorous fishes such as African Catfish (Clarias gariepinus), Bass species (Micropterus spp.) and Rainbow Trout (Oncorhynchus mykiss). Trout has been introduced into the Jan du Toits River which is one of the prime trout fly fishing streams. The impacts of invasive alien species on the Hex River subpopulation are compounded by ongoing habitat degradation through repeated bulldozing and channelization of this river and an increased turbidity and siltation.
Uses and trade
All indigenous fish species of the Western Cape Province are listed as Endangered Wild Animals under Schedule 1 of the Provincial Nature Conservation Ordinance for the Western Cape, thereby preventing the collection and trade of the species without a permit. Translocations of indigenous freshwater fish species are controlled by Cape Nature’s Indigenous Fish Utilisation policy (Jordaan et al. 2016).
Conservation
There are currently no conservation plans in place to protect this lineage. Immediate measures should focus on surveying the Hex River and its tributaries, the mainstem Breede and the Jan du Toits rivers to determine the status of this lineage, estimate population sizes and identify effective conservation and management strategies to prevent further loss of remaining subpopulations and promote recovery.
[@article{18475,
author = {Skelton, P.H.},
title = {A Complete Guide to the Freshwater Fishes of Southern Africa},
year = {2001}
}
,@article{126219629,
author = {Barnard KH },
journal = {Annals of the South African Museum},
pages = {101--263},
title = {Revision of the indigenous freshwater fishes of the S.W. Cape Region},
volume = {36.0},
year = {1943}
}
,@electronic{2426,
address = {www.iucnredlist.org},
author = {IUCN},
title = {The IUCN Red List of Threatened Species. Version 2017-3},
year = {2017}
}
,@article{19890,
author = {Chakona A, Swartz ER, Gouws G },
journal = {PLoS ONE },
number = {8},
title = {Evolutionary drivers of diversification and distribution of a southern temperate stream fish assemblage: testing the role of historical isolation and spatial range expansion},
volume = {8},
year = {2013}
}
,@book{63356,
address = {Cape Town},
author = {Skelton, P.H.},
publisher = {Struik Publishers},
title = {A complete guide to the freshwater fishes of southern Africa.},
year = {2001}
}
,@article{107625428,
author = {Waters JM, Cambray JA },
journal = {Journal of Fish Biology},
pages = {1329--1338},
title = {Intraspecific phylogeography of the Cape galaxias from South Africa: evidence from mitochondrial DNA sequences},
volume = {50},
year = {1997}
}
,@article{107625428,
author = {Wishart M, Hughes J, Stewart B, Impson D},
journal = {African Journal of Aquatic Science},
pages = {99--106},
title = {Extreme levels of intraspecific divergence among Cape Peninsula populations of the Cape galaxias, Galaxias zebratus Castelnau 1861, reveals a possible species complex},
volume = {31},
year = {2006}
}
,]
