This article was downloaded by: [Mr O LF Weyl] On: 30 December 2014, At: 07:56 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK African Journal of Aquatic Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/taas20 Species-specific impact of introduced largemouth bass Micropterus salmoides in the Groot Marico Freshwater Ecosystem Priority Area, South Africa PK Kimberga, DJ Woodfordbc, H Rouxd & OLF Weylbc a Hydrocynus Consulting, Kyalami, South Africa b South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, South Africa c Centre for Invasion Biology, SAIAB, Grahamstown, South Africa d Department of Rural, Environment and Agricultural Development, North West Provincial Government, Mahikeng, South Africa Published online: 02 Dec 2014. Click for updates To cite this article: PK Kimberg, DJ Woodford, H Roux & OLF Weyl (2014) Species-specific impact of introduced largemouth bass Micropterus salmoides in the Groot Marico Freshwater Ecosystem Priority Area, South Africa, African Journal of Aquatic Science, 39:4, 451-458, DOI: 10.2989/16085914.2014.976169 To link to this article: http://dx.doi.org/10.2989/16085914.2014.976169 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. 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Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions African Journal of Aquatic Science 2014, 39(4): 451–458 Copyright © NISC (Pty) Ltd Printed in South Africa — All rights reserved AFRICAN JOURNAL OF AQUATIC SCIENCE ISSN 1608-5914 EISSN 1727-9364 http://dx.doi.org/10.2989/16085914.2014.976169 Species-specific impact of introduced largemouth bass Micropterus salmoides in the Groot Marico Freshwater Ecosystem Priority Area, South Africa PK Kimberg1, DJ Woodford2,3*, H Roux4 and OLF Weyl2,3 1 Hydrocynus Consulting, Kyalami, South Africa 2 South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, South Africa 3 Centre for Invasion Biology, SAIAB, Grahamstown, South Africa 4 Department of Rural, Environment and Agricultural Development, North West Provincial Government, Mahikeng, South Africa * Corresponding author, e-mail: [email protected] Largemouth bass Micropterus salmoides are among the world’s 100 worst invaders and negatively affect aquatic biodiversity in many regions worldwide. In South Africa there is a paucity of empirical studies describing their impacts. The impact of M. salmoides on the fish community in the Groot Marico River catchment, an otherwise near-pristine river ecosystem and a freshwater ecosystem priority area, was assessed from surveys conducted in 2012. Fish presence and abundance were enumerated using multiple survey techniques, and their association with key habitat variables and the presence or absence of M. salmoides were assessed. A total of 14 native fish species were recorded, besides introduced M. salmoides, which occupied the majority of the mainstem and several tributaries downstream of barriers to upstream movement. Canonical correspondence analysis showed that only one native species, the Marico barb Barbus motebensis, had a negative spatial association with M. salmoides. Assessment of relative distributions showed this species to be excluded from M. salmoides-invaded river reaches, whereas the other native species were not visibly affected by the invader. This species-specificity of the impact of M. salmoides indicates that their impacts in South African streams may be dependent on predator-naiveté of prey. Keywords: Barbus motebensis, barriers, conservation, environmental guild, invasion, predation Introduction Invasive alien species present one of the greatest case studies. The species has been linked to the extirpation challenges to conservation in freshwater ecosystems, which of native fishes in the Swartkops River in the Eastern Cape are more threatened than terrestrial or marine ecosystems (Ellender et al. 2011) and to changes in their abundance (Dudgeon et al. 2006). Of the many invasive species that and behaviour in the Driehoeks River in the Western Cape cause harm, introduced sport fishes have had perhaps the (Shelton et al. 2008). Furthermore, M. salmoides was found Downloaded by [Mr O LF Weyl] at 07:56 30 December 2014 most profound negative impacts on freshwater fish conser- to alter invertebrate community composition by removing vation (Cambray 2003). The North American largemouth large, conspicuous insect taxa in the Wit River, Eastern bass Micropterus salmoides (Lacepède, 1802), listed as Cape (Weyl et al. 2010). one of the 100 worst invasive alien species in the world Micropterus salmoides has been present in the Groot (Lowe et al. 2000), was first introduced into South Africa Marico River, which forms the south-western headwaters for angling purposes in 1928, and has subsequently spread of the Limpopo River catchment, for at least two decades throughout the county (de Moor and Bruton 1988; van (Skelton et al. 1994). This river originates in the dolomitic Rensberg et al. 2011). While primarily a still-water species aquifer plateau region of the North West province and flows that thrives in impoundments (Warren 2009), M. salmoides through a variety of geomorphological features to its conflu- can also survive in rivers and low-salinity reaches of ence with the Crocodile River (King 1951). The perennial estuaries (Wasserman et al. 2011; Glover et al. 2013). tributaries of the Groot Marico River emanate from dolomitic Introduced M. salmoides have been found to affect native eyes, formed at contact zones between igneous rocks and aquatic fauna negatively through predation in Canada the dolomites of the Transvaal Supergroup (Eriksson et al. (Trumpickas et al. 2011), Portugal (Godinho and Ferreira 2006). Perennial flow from these springs is an important 2000), Japan (Takamura 2007) and Zimbabwe (Gratwicke ecological attribute of the upper reaches in this semi-arid and Marshall 2001). In South Africa, there is anecdotal catchment, forming aquatic refugia for endemic biota within evidence that the species has negatively affected local this system. The upper reaches flow in deeply incised biodiversity in the Cape Floristic Region catchments of the gorges that are relatively unimpacted and sheltered from Western and Eastern Cape provinces (de Moor and Bruton human disturbances such as intensive agricultural activities 1988; Tweddle et al. 2009), though there are few published (Grobler et al. 2007). African Journal of Aquatic Science is co-published by NISC (Pty) Ltd and Taylor & Francis 452 Kimberg, Woodford, Roux and Weyl Micropterus salmoides’ invasion of the catchment was were placed parallel to the flow in areas with submerged or probably the result of multiple independent introductions, overhead cover in the evening and retrieved the following particularly in the Marico Bosveld Dam, the first major morning. All fish captured were identified to species, impoundment on the river. The catchment upstream of measured to the nearest mm, and returned to the water. this dam is of significant conservation importance (Skelton Habitat parameters were recorded at each sampling reach et al. 1994; Smith-Adao et al. 2006; Nel et al. 2011), and after the capture and release of fish. For each sampling was identified as a freshwater ecosystem priority area reach, length and width were measured, with a minimum (FEPA) because of the free-flowing nature of the Groot of four transects being used to assess the latter. On each Marico River, its ecological category of A or B, and as a width transect, five points were randomly selected, where fish sanctuary for the Marico barb Barbus motebensis the depth and substrate type (bedrock, cobble, gravel, Steindachner, 1894, listed as Vulnerable in the International sand, vegetation) were noted. The locality of each site was Union for Conservation of Nature (IUCN) Red List (Nel et al. recorded using a Garmin GPS receiver, and the altitude of 2011). The catchment has historically supported up to 18 each site was later confirmed using a digital elevation model fish species (Kleynhans et al. 2007). (DEM) generated from 5 m contours obtained from the The invasion of M. salmoides in the Groot Marico River surveyor general department of South Africa. catchment is clearly a cause for concern, and represents a good