The effect of a large-scale irrigation scheme on the fish community structure and integrity of a subtropical river system in South Africa

Malherbe, Wynand; Wepener, Victor; Vuren, J.H.J. van

doi:10.1016/j.ecolind.2016.05.005

Cited by 7 publications

(5 citation statements)

References 20 publications

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“…Yet, ABC curves of these subgroups showed similar level of disturbance (Figure 4e,f), which most likely stems from major stressors such as irrigation, sand mining, overfishing and conversion of floodplains to agriculture and aquaculture. Irrigation infrastructure in the Tonle Sap floodplain and VMD has existed for many decades [98], and such infrastructure can modify flow, degrade habitats, create barriers and cause pollution [72,99]. Furthermore, irrigation canals have displaced the wetlands, which are home to not only fish but also to other aquatic animals and plants [8,100]; irrigation dams also block fish migration within the floodplains, and between tributaries and floodplains [72].…”

Section: Fish Community Structure and Its Ecological Statusmentioning

confidence: 99%

Fish Community Responses to Human-Induced Stresses in the Lower Mekong Basin

Nuon¹,

Lek

Ngor

et al. 2020

Water

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The Mekong River is one of the world’s largest rivers and has an annual captured fish production of about 2.3 million tonnes, equivalent to around 11 billion USD. Although the Mekong provides important ecological and socioeconomic benefits to millions of people, it is facing intensive change due to anthropogenic stressors. Therefore, it is necessary to understand the changes to the spatiotemporal fish communities to inform sustainable fisheries management. Here, we aimed to characterize patterns of the fish communities and identify the ecological status of each fish community using daily catch data from 2007 to 2018 at 25 monitoring sites in the Lower Mekong Basin (LMB). The collected data were classified by a self-organizing map into four main groups. Group 4 represented the lower Vietnam Mekong Delta (VMD), while groups 1, 2, and 3 were subdivided into subgroups 1a (upper LMB), 1b (upper and middle LMB), 2a (Mekong River below the Khone Falls and Sesan River), 2b (Mekong River below the Khone Falls and Sekong, Sesan and Srepok (3S) Rivers), 3a (Floodplain-Tonle Sap and Songkhram) and 3b (upper VMD). Among the 571 species recorded, 119 were identified as indicator species. Based on the abundance and biomass comparison curves, the fish community of 2b was in a healthier condition with a positive W-statistic value while the rest had a negative W-statistic value. The highest species richness and diversity were observed in 3a and 2b, so these subgroups deserve high management and conservation priority. Likewise, 1a should also be considered as a high priority area since it harbors several endangered and long-distant migratory fishes. It was also noticed that the fish communities of groups 3 and 4, located far from the hydropower dams, remained mostly unchanged compared to those of groups 1 and 2, close to the mainstream and tributary dams in the upper LMB and 3S Rivers.

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Section: Fish Community Structure and Its Ecological Statusmentioning

confidence: 99%

Fish Community Responses to Human-Induced Stresses in the Lower Mekong Basin

Nuon¹,

Lek

Ngor

et al. 2020

Water

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“…Secondly, is the system sensitive enough to detect pesticide specific signals rather than general stress within the macroinvertebrate community within the ecosystem? The potential stressors that are dominant at the selected sites in this study include salinity, nutrients, and habitat alteration [ 28 ]. The correlation with SASS5 results and the pesticide intensity measure indicated that the SPEAR pesticide indicator could be useful to indicate the effects of pesticides on the aquatic community even though the relationships in this study was not significant.…”

Section: Resultsmentioning

confidence: 99%

The Application of a Macroinvertebrate Indicator in Afrotropical Regions for Pesticide Pollution

Malherbe

Vuren

Wepener

2018

Journal of Toxicology

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Many biotic integrity indices are not able to isolate community effects due to pesticide exposure as the communities also respond to other anthropogenic and natural stressors. A macroinvertebrate trait bioindicator system that is pesticide specific was therefore developed to overcome these challenges. This system, called SPEAR (SPEcies At Risk), was applied in South Africa as an indicator to link known pesticide catchment usage to changes in the macroinvertebrate community, especially when analytical methods are inconclusive. In addition, the SPEARsalinity index within the SPEAR suite of tools was also evaluated for its effectiveness in South Africa. The results indicated that all of the sites have either been exposed to the same pesticide pressure or not been exposed to pesticides as the SPEAR results were similar when compared to the pesticide intensity. The interaction with other factors like nutrients or salinity was likely a factor that confounded the SPEARpesticides indicator.

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“…Presently, there are expansion plans for the development of hydropower impoundments/dams within eastern and southern Africa (McDonald et al 2009;Conway et al 2017). However, the construction of dams has caused river ecosystems to be radically transformed via alterations to water quality, hydrology and habitat characteristics (Kondolf 1997;Lessard and Hayes 2003;Malherbe et al 2016;Ngor et al 2018;Zhang et al 2018). The dependence of the various biological aspects of ichthyofauna communities on the aforementioned ecosystem characteristics denote that they are particularly vulnerable to anthropogenic alterations (Skelton et al 1995;Peacock et al 2016;Akbaripasand and Closs 2018;Baggio et al 2018;Ngor et al 2018;Ramesh et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Spatial shifts and habitat partitioning of ichthyofauna within the middle–lower region of the Pungwe Basin, Mozambique

Desai

Husted

Fry

et al. 2019

Journal of Freshwater Ecology

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Freshwater resources are under stress because of anthropogenic activities and the demand for water increasing on a global scale, including hydropower. There are presently plans to expand the use of hydropower within eastern and southern Africa. A key river system identified as a potential source of energy is the Pungwe River, with the proposed Pavua Dam located within the middle reaches of the system in Mozambique. However, impoundments have been recorded to negatively influence ichthyofauna communities via alterations to water quality and discharge. Furthermore, information on the structure of the ichthyofauna community, community spatial shifts and fine-scale habitat preferences for the region are lacking. Accordingly, the research sought to address this issue, to provide baseline data as well as inform on management of the system. Ichthyofauna were collected utilising an array of passive and active techniques and species data modelled to fit spatial factors to ascertain spatial shifts. To ascertain fine-scale habitat preferences, fourth-corner modelling was undertaken to link mouth position and body shape traits to substrate composition and cover features. Spatial heterogeneity in environmental characteristics caused by the intrusion of the African Rift Valley had driven significant spatial shifts in the ichthyofauna community, with distinct groups of species occurring within the sample sites. The findings of the study indicated that the ichthyofauna community within the Muazi River were significantly different to the Pungwe River and the community will be lost from the region because of the dam footprint. Furthermore, habitat preferences were influenced by mouth position and body shape. Consequently, alteration to environmental characteristics and habitat features is likely to negatively influence the ichthyofauna community.

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The effect of a large-scale irrigation scheme on the fish community structure and integrity of a subtropical river system in South Africa

Cited by 7 publications

References 20 publications

Fish Community Responses to Human-Induced Stresses in the Lower Mekong Basin

Fish Community Responses to Human-Induced Stresses in the Lower Mekong Basin

The Application of a Macroinvertebrate Indicator in Afrotropical Regions for Pesticide Pollution

Spatial shifts and habitat partitioning of ichthyofauna within the middle–lower region of the Pungwe Basin, Mozambique

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