The effect of largemouth bassMicropterus salmoideson aquatic macro-invertebrate communities in the Wit River, Eastern Cape, South Africa

Abstract

Fish predation is one of the driving forces of freshwater invertebrate community structures, with alien predators having a pronounced effect. A quantitative assessment of aquatic invertebrates in the Wit River, Sundays River catchment, Eastern Cape, South Africa, was undertaken to assess the impact of the alien fish Micropterus salmoides on their relative abundance and community structure. Communities in the stones-in-current and marginal vegetation biotopes were sampled in the presence and absence of M. salmoides in late summer (February-April) 2008. Results suggest that the presence of M. salmoides does have an impact on indigenous macroinvertebrate fauna and communities. Community structure in the stones-in-current biotopes did not differ significantly between sections of the river with or without fish. However, there was a significant difference in community structure in marginal vegetation between sections of river. In sections with M. salmoides several large or conspicuous taxa (Odonata, Hemiptera and Coleoptera) were significantly reduced (p < 0.05) or even absent, while cryptic/inconspicuous taxa (Trichoptera, Leptoceridae and Mollusca, Physidae) were significantly more abundant (p < 0.05).

Existing and emerging high impact invasive species are characterized by higher functional responses than natives

“…Here, the FR of the largemouth bass, an invasive fish with well-established field impacts [12], was significantly higher in comparison with the native equivalent, the Cape kurper. This finding corroborates reported field impacts, whereby in areas where bass are present, native prey species populations are often decimated and other native fish species are absent [13,18]. Similarly, a heightened FR was observed in the emergent invader, the sharptooth catfish, in relation to the comparator native species, the river goby.…”

“…Largemouth bass (Micropterus salmoides) and sharptooth catfish (Clarias gariepinus) are known invaders in southern Africa. Whereas the ecological impacts of largemouth bass are well established, with negative effects on native invertebrate and fish communities [12,13], impacts of the sharptooth catfish, although evident, are not yet well quantified [14,15]. Since trophically analogous native fish species exist in South Africa, the Cape kurper (Sandelia capensis) and the river goby (Glossogobius callidus), we experimentally derived the predatory FRs of the two invaders and the two natives.…”

Non-native rainbow trout change the structure of benthic communities in headwater streams of the Cape Floristic Region, South Africa

“…In particular, invasive bass (Micropterus spp.) have eradicated native fish populations from the downstream reaches of rivers (de Moor & Bruton, 1988;Woodford et al, 2005;Weyl et al, 2010;Ellender et al, 2011), whereas rainbow trout Oncorhynchus mykiss (Walbaum, 1792) have severely depleted (or eliminated) native fish populations upstream in the headwater reaches of many streams (Shelton et al, 2014). Our understanding of whether these perturbations at the level of the fish assemblage have cascaded down the food web to lower trophic levels is inadequate (de Moor & Bruton, 1988;Cambray, 2003b;Lowe et al, 2008), but such information is needed if we are to appreciate the full extent of the non-native fish impacts in CFR streams.…”

Detecting impacts of invasive non-native sharptooth catfish, Clarias gariepinus, within invaded and non-invaded rivers

“…The most common response of macroinvertebrates to predation by nonnative fish is a decline in the densities of vulnerable taxa (Kadye and Magadza 2008;Johnson et al 2009;Duxbury et al 2010). Large-bodied prey, such as odonates, are usually the most vulnerable group in recently invaded habitats (Englund and Polhemus 2001;Maezono and Miyashita 2003;Maezono et al 2005) because invasive predators are opportunistic feeders that tend to target the most conspicuous and accessible prey (Miller and Crowl 2006;Johnson et al 2009;Weyl et al 2010). Odonates are usually dominant macroinvertebrate predators that play a crucial role as keystone predators, especially in fishless and uninvaded habitats (Donald and Anderson 2003), and their elimination by invasive predators has been observed to correspond to an increase in the abundance of their potential prey, which reflects trophic cascades (Maezono and Miyashita 2003;Phillips et al 2009).…”

“…Their high abundance during this study suggests that they were probably detritovorous. Similarly earthworms and midges are detritivores that are known to be abundant within impacted habitats because they tend to burrow into or live within soft substrata, and benefit from both the elimination of their competitors and increased exposure to resources when a detritus-based food web dominates within disturbed environments (Knapp et al 2001;Ruetz et al 2002;Miller and Crowl 2006;Weyl et al 2010).…”