The impact of invasive fish and invasive riparian plants on the invertebrate fauna of the Rondegat River, Cape Floristic Region, South Africa

Lowe, Steven; Woodford, Darragh J.; Impson, Dean; Day, Jenny A.

doi:10.2989/ajas.2007.33.1.6.390

Cited by 48 publications

(59 citation statements)

References 20 publications

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“…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. The results from two recent studies conducted in the CFR (Lowe et al, 2008;Weyl et al, 2010) suggest that the impact of invasive bass may indeed extend beyond the elimination of native fish populations, in that the composition of aquatic invertebrate assemblages was found to differ between sections of streams with and without bass.…”

Section: Introductionmentioning

confidence: 99%

“…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. The results from two recent studies conducted in the CFR (Lowe et al, 2008;Weyl et al, 2010) suggest that the impact of invasive bass may indeed extend beyond the elimination of native fish populations, in that the composition of aquatic invertebrate assemblages was found to differ between sections of streams with and without bass. On the other hand, the question of whether rainbow trout introductions have influenced lower trophic levels in CFR streams has not yet been addressed, and forms the focus of this study.…”

Section: Introductionmentioning

confidence: 99%

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

2014

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Introduced rainbow trout Oncorhynchus mykiss have invaded many headwater streams in the Cape Floristic Region (CFR) and depleted, or eliminated, native fish populations. However, the question of whether trout invasions also have consequences for lower trophic levels in these systems has not been addressed. We used a broad-scale comparative study in the upper Breede River catchment (CFR) to evaluate differences in benthic community structure between sites on headwater streams with and without trout, and thereby infer community-level impacts of trout. There were differences in invertebrate abundance and assemblage composition, and algal biomass, between sites with and without trout. Specifically, the abundance of certain herbivorous invertebrate taxa was higher, and the biomass of benthic algae lower, at sites invaded by trout. This pattern implies that trout have induced a trophic cascade by releasing herbivorous invertebrates from predation, leading to an increase in grazing pressure and a consequent indirect decrease in the biomass of benthic algae; a pattern that contrasts with the majority of studies investigating community-level impacts of introduced trout elsewhere. These findings, together with comparisons of environmental conditions between invaded and uninvaded sites, indicate that trout invasions have changed the structure and function of benthic communities in these streams.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2014

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“…Apart from the preliminary work of Lowe et al (2008), no previous research has determined the effects of alien tree invasion and removal on the highly endemic aquatic macroinvertebrate communities of the CFR. Therefore, we aim here to assess the effects on riparian habitats and benthic macroinvertebrate communities of as a result of alien tree invasion, and extent of recovery where the alien trees have been removed, in comparison with natural, untransformed sites in the same catchments.…”

Section: Introductionmentioning

confidence: 99%

Effect of alien riparian vegetation and its removal on a highly endemic river macroinvertebrate community

2010

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Invasive alien trees along river banks can reduce indigenous biodiversity, while their removal can restore it. We assessed here family-and specieslevel responses of river benthic macroinvertebrate assemblages to three riparian vegetation types (natural, alien trees, cleared of alien trees) in the Cape Floristic Region biodiversity hotspot. High species beta diversity of this highly endemic fauna meant that between-river, as well as seasonal effects, dominated assemblage patterns. SASS5, a qualitative, rapid bioassessment technique, based on the sensitivity of the families present, was used as a measure of river health and, indirectly, of water quality. SASS indicated a decline in water quality conditions after alien clearing, a likely response to the greater insolation and apparent erosion of cleared banks, resulting in elevated temperatures and suspended solids and lowered oxygen levels. Overall, cleared and natural sites were more similar to each other than to alien sites, suggesting some post-clearing recovery. However, many sensitive, endemic taxa survived in alieninvaded sites, and more than in the natural sites. These endemic species made use of shady, cool, highoxygen levels under the alien tree canopy. However, endemics declined in overall abundance in sites cleared of aliens, being replaced by more tolerant, widespread taxa. Clearance of the alien trees opened up the rivers to sunny conditions, which had a major impact on community composition. Vegetation types, oxygen levels and river width were important environmental variables affecting these macroinvertebrate responses. Re-establishment of invertebrate biodiversity matched that of indigenous vegetation, with the most sensitive endemic taxa only recovering after establishment of bushy indigenous and shadeproducing fynbos. Therefore, for biodiversity conservation objectives to be achieved, it is essential that indigenous plants are maintained and encouraged during and after clearing to ensure the recovery of endemic and sensitive taxa.

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“…A field experiment in Northern Japan (Baxter et al 2004) demonstrated that predation by invasive rainbow trout Oncorhynchus mykiss had a cascading effect that extended across the aquatic-terrestrial boundary via a reduction in emerging insects (Baxter et al 2004). Lowe et al (2008) studied the impacts of smallmouth bass Micropterus dolomieu in the Rondegat River, South Africa, and demonstrated ecosystem level effects that included changes in invertebrate community structure, alterations in grazing patterns and pressure and concomitant differences in algal biomass between invaded and non-invaded sections of the river.…”

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confidence: 99%

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

Weyl

Moor

Hill

et al. 2010

African Journal of Aquatic Science

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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).

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The impact of invasive fish and invasive riparian plants on the invertebrate fauna of the Rondegat River, Cape Floristic Region, South Africa

Cited by 48 publications

References 20 publications

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

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

Effect of alien riparian vegetation and its removal on a highly endemic river macroinvertebrate community

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

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