SANBI

Rationale

The species occurs in several tributaries of the Kouga, Baviaanskloof and Groot subcatchments of the Gamtoos River System (Swartz et al. 2007, 2009, Chakona and Skelton 2017). These subpopulations are fragmented due to invasion of the main river sections by alien predators, mainly by Black Bass species (Micropterus spp.) and the African Sharptooth Catfish (Clarias gariepinus). Genetic data indicate that this species, referred to as the St Francis lineage by Swartz et al. (2007, 2009), historically occurred in the Kabeljou and the Swart river systems but surveys in 2007 did not find any redfins in these systems. This suggests that these subpopulations have either severely declined or have possibly been extirpated and further surveys are required. Six subpopulations of this species occur in protected areas, but the protection offered by these areas may not be effective if there are no instream physical barriers to prevent the spread of alien invasive predators which are now dominant in the main stem sections of the rivers. Recent surveys in 2015 and 2016 showed that most of the remaining subpopulations of P. swartzi are likely to be represented by large population sizes, but more surveys are required to map the distribution of instream physical barriers in relation to the distributions of alien invasive species and P. swartzi. Pseudobarbus swartz is listed as Vulnerable under criterion B1ab(iii,v)+2ab(iii,v) as it has a extent of occurrence (EOO) of 2,254 km², an area of occupancy (AOO) of 36 km², and is known from 10 locations that are all under continuous threat from invasion by non-native species which are abundant in the mainstem sections of the Kouga and Groot rivers. The other main threats to this species are excessive water and habitat degradation due to agricultural activities.

Distribution

Widely distributed in the Kougaberg, Baviaanskloofberg and Elandsberg tributaries of the Kouga, Baviaanskloof and Groot subcatchments of the Gamtoos River System (Chakona and Skelton 2017). The species was historically recorded in the Kabeljous and Swart river systems, but recent surveys have failed to collect redfins in these systems. The status and distribution of Pseudobarbus swartzi populations in the Kabeljous and Swart river systems needs to be assessed through fine scale geographic surveys. There is also need for investigations to determine the taxonomic status of redfins in the Seekoei and Maitland, two river systems which also discharge into St Francis Bay (Swartz et al. 2007, Chakona and Skelton 2017). Remnant subpopulations in the Kouga and Groot subcatchments are highly fragmented due to invasion of the main stem sections of the rivers by alien predators (see Threats section).

Habitat View more ecological information

Population trend

Trend

There are at least 10 known subpopulations of this species that survive in tributaries of the Kouga, Baviaanskloof and Groot rivers that drain the Kougaberg, Baviaanskloofberg and Elandsberg Mountains (Chakona and Skelton 2017). Recent surveys in 2015 and 2016 suggest that these subpopulations are still represented by large population sizes, but this needs to be verified through more fine scale geographic surveys to map the lower and upper distribution limits of each subpopulation more accurately. Surveys are also required to determine the population status of the Kabeljous and Swart rivers and to determine whether the redfins in the Seekoei and Maitland rivers belong to this species.

Threats

Remnant subpopulations of this species are mainly threatened by invasive alien predators; particularly Bass species (Micropterus spp.) and African Sharptooth Catfish (Clarias gariepinus) that could potentially invade the mountain tributaries from the mainstem sections of the rivers. Water abstraction and habitat degradation are the second most important threats to this species. Fragmentation of the previously connected subpopulations that are now confined to mountain tributaries may limit or prevent genetic exchange between these isolated subpopulations, leading to increased risk of inbreeding. This can reduce the adaptive responses of P. swartzi to the projected environmental changes in the region (Dallas and Rivers-Moore 2014).

Conservation

The presence of alien invasive species is the major threat to this species. There is need for more comprehensive surveys to establish the status of the remnant subpopulations of P. swartzi and identify tributaries that need to be prioritised for protection for example; through eradication of invasive alien fish and building of barriers to prevent invasion of upstream river sections as sanctuaries for this species. There is also need for close engagement between the scientific community, conservation authorities and local stakeholders in the Gamtoos Valley to collectively identify effective measures to prevent further decline or loss of the remaining subpopulations.

References

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,]

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