Author Archive Mahomed Desai

A survey in the Pungwe

During February and July 2017, Mahomed Desai, senior researcher and PhD candidate was part of a team that undertook an ecological survey within a selected area of the Pungwe Catchment in Mozambique.

Figure 1 3D Layout of the Pungwe Basin (Tinley, 1977)

The Pungwe River is shared between Mozambique (95% of the basin, generating 65-70% of the runoff) and Zimbabwe (5% of the basin, generating 30-35% of the runoff). The Pungwe River and its associated tributaries are highly dynamic and possess a relatively high diversity of habitat and biotope types, possibly due to the geomorphological nature of the system. The Pungwe mainstem can be described as torrential and is possibly due to the predominance of bedrock in the system as well as the topographical nature of the catchment. However, the river widens and flattens as it traverses the southern tip of the African Rift Valley – See Figures 2 and 3.

Figure 2 The southern tip of the East African Rift Valley system (WildCam Lab, 2017)

Figure 3 Photographs illustrating the Pungwe River (clockwise from top left) – Upstream view from the boundary of the Rift Valley during the low flow season; downstream view from the boundary of the Rift Valley during the low flow season; the Pungwe Gorge wherein the entire river is constrained into a relatively narrow gorge (to get an idea of the scale the depth off the edge was greater than 7 m) and deploying a fyke net in the Pungwe River (the bridge in the background is the boundary of the Rift Valley)
One of the major tributaries of the Pungwe River within the survey area is the Muazi River. The river is also bedrock-dominated (Figure 4). During the low flow season the turbidity of the system reduces and supports a population of Hydrostachys polymorpha, a rheophilic aquatic macrophyte (Figure 4). The species is currently listed as ‘Vulnerable’ and plays an important role in supporting an array of aquatic biota. In addition, within the survey area there are numerous creeks with a gravel and sand thalweg that drain into the system (Figure 4). These creeks provide a refuge area for various aquatic biota but these are however seasonal. Nevertheless, during low or zero flow periods there are isolated pools connected by sub-surface flow that provide habitat.

Figure 4 Photographs illustrating the Muazi River, a major tributary of the Pungwe River (clockwise from top left) – Downstream view exhibiting rapid-pool complex typical of the reach; angling in a large active channel pool; underwater photograph illustrating Hydrostachys polymorpha, an aquatic macrophyte listed as ‘Vulnerable and one of the numerous creeks that drain into the Muazi River (only isolated pools connected by sub-surface flow present during the low flow season)
As a consequence of the relatively high diversity of habitat types and biotopes within the system, including the survey area, the region supports a relatively high level of biodiversity, both terrestrial and aquatic. Of special interest within a regional context are the ichthyofauna, Odonata and terrestrial insects. These organisms although not as visible as other ‘charismatic’ species such as birds or larger mammals nevertheless are important in maintaining ecosystem processes and thereby overall wellbeing. A total of 38 species of ichthyofauna were recorded during both seasonal surveys and were typical of the Zambezian fauna. The dominant families were Cyprinidae, Mochokidae and Mormyridae. The ichthyofauna and formed unique communities within the system based on availability of cover features and substrate preferences, per redundancy analyses. Figure 5 illustrates some of the species recorded within the survey area.

Figure 5 Examples of the ichthyofauna of the survey area (clockwise from top left) Cyphomyrus discorynchus; Syndodontis zambezensis; Zaireichthys rotundiceps; Opsaridium zambezense; Marcusenius macrolepidotus and Hydrocynus vittatus

In addition, a new species or species complex of Chiloglanis (Mochokidae W. K. H. Peters, 1868) was recorded for the survey area (Figure 6). The species was typically associated with rapids and runs and utilised aquatic macrophytes, rocky crevices and cobble/boulder substrates as cover. Although data does not exist on dietary requirements, based on closely related species, it is assumed to feed on “aufwuchs” or the periphyton and invertebrate community that inhabit sold surfaces of lotic systems.

Figure 6 Top row – Photographs illustrating the lateral (left) and ventral view (right) of Chiloglanis sp. nov. Bottom row – Boxplot indicating catch per unit effort of Chiloglanis sp. nov. across hydraulic biotopes sampled. Dark horizontal line represents the median value, whisker represents 95th percentile and dots represent outliers
Due to the characteristics and size of the system as well as its inherent biodiversity, the system provides an array of ecosystem services to local communities and to society within a larger regional context. These services are varied and include subsistence fisheries, sediment deposition for agriculture, raw materials and pest control amongst others (Figure 7). However, no formal quantitative or qualitative studies have been undertaken and these are postulated based on previous knowledge from other systems and observations during the survey periods. Therefore, future research of this subject within the region should be considered if funding is available.

Figure 7 Examples of the range of ecosystem services provided by the Pungwe system (clockwise from top left) Fish trap made from reeds used during the high flow season; fish trap used during low flow periods; subsistence fishing is an important activity for local communities; maize fields in floodplain; Odonata are important pest-control agents and raw materials harvested for construction

Although the region possesses a substantial level of biodiversity the only formally protected area is Gorongosa National Park (GNP), located within the Lower Pungwe River. The Pungwe River delineates the southern boundary of GNP (Figure 8). Seasonal flooding from the Pungwe inundates shallow pans and oxbow channels on the Rift Valley plain at the southern end of the park. This flooding is vital for the newly constructed 6200 ha wildlife sanctuary near Chitengo and the DingeDinge Marshes at the confluence of the Pungwe and Urema rivers. During the high flow season, the Pungwe River branches and forms the Nhanvu River that flows into the Urema River upstream of Lake Urema and subsequently the Muaredze River before joining back into the Pungwe River. During the dry season, the Nhanvu River transforms into a series of pans (Figure 8). Nevertheless, these pans perform a vital function by providing refuge and/or nursery habitats evidenced by the relative abundance of Enteromius species, including E. haasianus, and juvenile life-stages of species recorded within the respective pans during the survey (Figure 8). During the high flow season when connectivity to the Pungwe River is restored, species are able to disperse and colonise new available habitat. Therefore, the connectivity between the pans and the Pungwe River is regarded as critical to maintain the wellbeing of the local ichthyofauna population.

Figure 8 Photos to illustrate the Pungwe River at Gorongosa National Park (clockwise from top left) Pungwe River during sunset; one of the pans fed by the Pungwe River via the Nhanvu River during high flows; pans linked to the Pungwe via the Nhanvu River are important refuge and nursery areas once isolated during the low flow season and Crocodylus niloticus at Lake Urema

At present, there are no significant water resources development projects in the Pungwe River basin in Mozambique. However, demand to harness Pungwe waters for inter-basin water transfer, municipal water supply, salinity control, hydropower, flood mitigation, large irrigated agriculture (sugar) schemes, and other uses is increasing. Furthermore, unsustainable use of the system and its catchment is leading to a decline in biodiversity and ecosystem wellbeing. Given the substantial socio-ecological importance of the system, it must be sustainably managed in a holistic manner involving all stakeholders as well as formally conserved in key areas.

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The Hunt for Rare Fish

During the week of the 10th – 14th October several members of our research group, Dr. Gordon O’Brien, Mahomed Desai, Céline Hanzen and Lungelo Madiya, who were accompanied by Ezemvelo KZN Wildlife Aquatic Ecologist, Skhumbuzo Khubheka, went on a survey to locate some of our rarer fish species in Northern KZN. The area falls within the uSuthu-Mhlathuze Water Management Area and includes South Africa’s first World Heritage Site, the iSimangaliso Wetland Park as well as the Maputaland Centre of Endemism. Apart from its ecological importance, the area is also utilised for an array of socio-economic activities.

This was a preliminary survey and was meant to confirm the presence of our target species in certain systems and to collect DNA samples. Further surveys will be more undertaken that will be more protracted to allow for effective and relatively comprehensive sampling at sites.

From left - Skhumbuzo Khubekha, Dr. Gordon O'Brien, Mahomed Desai, Lungelo Madiya and Céline Hanzen

From left – Skhumbuzo Khubekha, Dr. Gordon O’Brien, Mahomed Desai, Lungelo Madiya and Céline Hanzen

The first day was just set aside for travelling and brain-storming to identify possible sites where the species could be located. Our base was Hluhluwe-iMfolozi National Park.

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While the landscape is scenic and the large mammals attract many visitors , it is important to highlight and make the public aware that it is the smaller organisms that create a functioning ecosystem (such as the dung beetles pictured above). Whilst driving up from Durban we noticed that the area had received some rainfall which provided some respite from the drought that we are currently facing.

The first site was located on the southern end of Muzi Pan on the floodplain of the Mkuze River. Prior to sampling for fish we collected in situ water chemistry. With regards to this survey, fish were sampled using an electrofisher and seine nets. Thereafter, biotope details were recorded including depth, velocity, substrate and cover features.

Mahomed calibrating the water meters

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Lungelo and Skumbuzo ready for sampling !

 

 

 

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Brycinus lateralis

While the site yielded a relatively high diversity and abundance of species, none of our target species was recorded while going through the samples, until success; a single individual of a Brycinus lateralis was found! It is concerning that only a single individual was collected as unlike the other widespread Brycinus species in South Africa, B. lateralis is restricted to the Lake St. Lucia catchment.

 

The day we arrived, the Hluhluwe River in the reserve had reasonable flows compared to when we sampled there in September, when it was just a series of pools. Therefore, we decided to sample the river on the second day but outside of the park. However, when we arrived at our pre-selected site from Google Earth it was just a pool. Another success! We collected a few specimens of Micropanchax myaposae

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Pool on the Hluhluwe river

 

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Micropanchax myaposae (female)

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Micropanchax myaposae (male)

 

 

 

 

 

 

 

We were somewhat surprised at collecting a resaonable diversity of species at the site given that trucks were abstracting downstream as well as the presence of relatively large quantities of solid waste.

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Water abstraction on the Hluhluwe river

Furthermore, we wondered as to why the Hluhluwe river was flowing in the park but not where we had sampled. Then while looking at satellite imagery we identified a dam on the Hluhluwe River. The dam level was relatively low and consequently, there would need to be relatively high levels of precipation upstream in the catchment to fill the dam and to ensure adeqaute flows downstream.

 

 

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On day three the weather turned for the worse but we nevertheless sampled. The selected site was a swamp forest stream in suburbia in Richards Bay, a predominantly industry based town.

The site was dominated by Barringtonia racemosa, a protected tree, and possessed specimens of Voacanga thouarsii whilst the understorey was dominated by ferns. It was in this stream that we recorded 7 Clarias theodorae, another rare species that we were hoping to collect. Unfortunately, the stream is negatively impacted as surface runoff from nearby hardened surfaces drain into it and noticeable quantities of solid waste were present in certain sections. In addition, stormwater drains were present adjacent to the stream and if these are blocked with solid waste and spill, the water quality will deteriorate.
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Clarias theodorae

Clarias theodorae

Unfortunately we were not able to find some of the other species that we were searching for. Although we did collect the aforementioned species that we were targeting, they were never present in relatively high  abundances. There were several other sites that we had sampled but we did not collect any of our target species. Were they not present at these sites? or are they so cryptic that we could not collect them? Do they have particular habitat requirements? These are some of the questions that need answering.

We did notice that all of the sites that we sampled were negatively impacted by anthropegenic influences. If unsustanibaly utilised and/or mismanaged we could lose our natural heritage and their associated ecosystem goods and services, upon which society itself relies.

River Health Programme : Surveys in Northern KZN

While the fieldwork and draft report has been completed for the November 2014 to March 2016 increment of the River Health Programme, another round of sampling has been completed in September/October 2016. Specimens were collected, identified, DNA samples collected and biotope features where each species was collected was recorded.

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The W Primary Catchment – From the Umhlathuze to the uSuthu

The W Primary catchment is located in Northern KZN and spans from the Umhlathuze to the uSuthu River. A total of 17 sites are located in this area, with many being ecologically important due to presence of a relatively high level of freshwater biodiversity and species endemism for the province.

The area is not only important for freshwater biodiversity but terrestrial biodiversity as well.

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Many of the systems within the area were completely dry or not flowing due to the intense drought the country is presently experiencing.

However, some of the sites that retained pools were identified as important refuge areas for several species of fish as well as Odonates.

Key examples of this include a site on the Nwaku River that comprised of a series of pools where a total of 304 individuals from 6 species were recorded. Species recorded included Pseudocrenilabrus philander as well as the recently red-listed Enteromius gurneyi. 

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(c) christian Fry

 

Another important example was the site located on the Sikwebezi River. At this site the local landowner was fortunately supplying the system with surface water from his storage dam otherwise the site would have been completely dry.

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Thanks to his efforts in maintaining water in the system, a total of 167 individual fish were recorded, including juveniles of migratory species such as Labeo molybdinus and Labeobarbus natalensis.

Although some systems were possessed no flows, some of the larger systems were flowing and were identified as important areas for fish populations. Unfortunately, due to time constraints these sites were not sampled as comprehensively as warranted and the intention is to re-visit these sites to obtain a better understanding of the fish populations they possess. This included the sites on the Umhlathuze River as well as sites located within the Phongolo catchment. Below are some of the species that were recorded for these sites.

 

Unfortunately, many of the sites within the area were negatively impacted from anthropogenic activities and influences such as industry, illegal sand-mining, solid waste and over-grazing.

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Considering that society needs the ecosystem goods and services that freshwater ecosystems supply, it is critical that we effectively and sustainably manage the way we use our natural resources to ensure an optimum balance between protection and use. Education is also important if we are to ensure the protection of these vital ecosystems for the benefit of all.

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