Aquatic Assessment of the Yaligimba concession Aquatic Ecology … · 2018. 2. 8. · Aquatic...

Aquatic Assessment of the Yaligimba concession

Aquatic Ecology Assessment

Project Number:

CDC2950

Prepared for:

Feronia PHC

August 2015

_______________________________________________________________________________________ Digby Wells and Associates (South Africa) (Pty) Ltd (Subsidiary of Digby Wells & Associates (Pty) Ltd). Co. Reg. No. 2010/008577/07. Fern Isle, Section 10, 359 Pretoria Ave Randburg Private Bag X10046, Randburg, 2125, South Africa Tel: +27 11 789 9495, Fax: +27 11 789 9498, [email protected], www.digbywells.com _______________________________________________________________________________________ Directors, DJ Otto, GB Beringer, LF Koeslag, AJ Reynolds (Chairman) (British)*, J Leaver*, GE Trusler (C.E.O) *Non-Executive _______________________________________________________________________________________

mailto:[email protected]

http://www.digbywells.com/

Digby Wells Environmental i

This document has been prepared by Digby Wells Environmental.

This report is provided solely for the purposes set out in it and may not, in whole or in part, be used for any other purpose without Digby Wells Environmental prior written consent.

Report Type: Aquatic Ecology Assessment

Project Name: Aquatic Assessment of the Yaligimba concession

Project Code: CDC2950

Name Responsibility Company Date

Russell Tate

Survey and report

Digby Wells Environmental

August 2015

Marion Thomas

Reviewer


May 2015

Brett Reimers

Reviewer


May 2015



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Digby Wells Environmental ii

EXECUTIVE SUMMARY

Digby Wells Environmental was commissioned by Feronia PHC to conduct aquatic ecological specialist studies on their Yaligimba oil palm concession in the central Congo basin. The aim of this study was to establish the conservation value of the aquatic ecosystems associated with the oil palm concession. As such, this study aimed establish the ecological status, degree of endemism, conservation status of species and overall conservation value of the associated river courses.

The assessment of aquatic ecological conditions in the rivers associated with the Yaligimba concession revealed their largely natural status. Central impacts associated with the considered river systems were deforestation and the associated riparian habitat loss. However, these were determined to have a limited measurable effect on the river systems considered. As such the river systems were determined at present, to be sufficiently conserved, although, future assessments are recommended.

The assessment of local aquatic biota confirmed that natural fish communities are largely common, but further studies are recommended. The assessment for rare, threatened and endangered ichthyofaunal taxa showed the general absence of endangered fish species in the Yaligimba concession. Further assessment by Digby Wells revealed that the endemic taxa expected to be present, have wide distributions and were largely labelled “least concern” in terms of conservation status. Therefore, the degree of endemism on the Yaligimba concession was identified as low, due to the large distribution of endemic taxa in the Democratic Republic of Congo.



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Digby Wells Environmental 3

TABLE OF CONTENTS

1 Introduction ........................................................................................................................ 1

2 Methodology ...................................................................................................................... 1

2.1 Expertise of the Aquatic Specialist ........................................................................... 1

2.2 Survey ..................................................................................................................... 1

2.3 Water Quality .......................................................................................................... 2

2.4 Aquatic Habitat ........................................................................................................ 2

2.4.1 Intermediate Habitat Integrity Assessment ........................................................ 2

2.5 Fish ......................................................................................................................... 5

2.5.1 Conservation Status and Expected Species ..................................................... 6

3 Limitations ......................................................................................................................... 6

4 Study Sites, General Aquatic Habitat and Expected Diversity ........................................... 6

4.1 General Aquatic Habitat and Expected Diversity ..................................................... 6

4.2 Aquatic Habitat of the Yaligimba Concession .......................................................... 8

5 Results ............................................................................................................................ 16

5.1 Water Quality ........................................................................................................ 16

5.2 Intermediate Habitat Assessment Index ................................................................ 16

5.3 Fish Assessment ................................................................................................... 19

5.3.1 Fish Community Assessment ......................................................................... 19

5.3.2 Endemic and conservation assessment .......................................................... 19

6 Discussion ....................................................................................................................... 21

6.1 Water quality ......................................................................................................... 21

6.2 Intermediate Habitat Integrity Assessment ............................................................ 22

6.2.1 The Loeka River ............................................................................................. 22

6.2.2 The Itimbiri Tributaries .................................................................................... 22

6.3 Fish assessment ................................................................................................... 23

7 Recommendations .......................................................................................................... 24

8 High Conservation Value Aspects ................................................................................... 24



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9 Conclusions ..................................................................................................................... 27

10 References ...................................................................................................................... 27

LIST OF FIGURES

Figure 3-1: Large Crowds at aquatic survey site, Yaligimba (January 2015) .......................... 6

Figure 4-1: Freshwater fish species richness of the Freshwater Ecoregions of the world (Abel et al. 2008) ............................................................................................................................ 7

Figure 4-2: Endemic freshwater fish species richness of the various Freshwater Ecoregions of the world (Abel et al. 2008). ............................................................................................. 8

Figure 4-3: Typical tributary at YAL5 ................................................................................... 10

Figure 4-4: Aquatic substrates in the upper tributaries. (A) YAL2, (B) YAL5 ........................ 10

Figure 4-5: Aquatic vegetation at sites on the Yaligimba concession, January 2015. (A): Eichhornia crassipes and (B): Nymphaea nouchali at the site YAL4 ................................... 10

Figure 4-6: Aquatic sampling points for the Yaligimba aquatic survey (January 2015) ......... 11

Figure 4-7: Typical river channel in the Loeka River at YAL1 .............................................. 12

Figure 4-8: Well-defined floodplain of the Loeka River at YAL1 ........................................... 12

Figure 4-9: Typical habitat in the tributaries of the Itimbiri River (YAL6)............................... 13

Figure 4-10: Photographs illustrating typical aquatic habitats in the larger tributaries at YAL1 (A) and YAL6 (B) ................................................................................................................ 13

Figure 6-1: Channa obscura observed at YAL1 ................................................................... 23

LIST OF TABLES

Table 2-1: Criteria in the assessment of habitat integrity (Kleynhans, 1996) .......................... 2

Table 2-2: Table giving descriptive classes for the assessment of modifications to habitat integrity (Kleynhans, 1996). ................................................................................................... 4

Table 2-3: Criteria and weights used for the assessment of habitat integrity (Kleynhans, 1996) ................................................................................................................................... 4

Table 2-4: Intermediate habitat integrity categories (Kleynhans, 1996) ................................. 5

Table 4-1: Global Positioning System (GPS) co-ordinates for the aquatic sampling points of the Yaligimba oil palm concession (January 2015 survey) ................................................... 8



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Table 4-2: General habitat photographs at each site during the January 2015 survey ......... 14

Table 5-1: In situ water quality results survey at the Yaligimba concession (January 2015).16

Table 5-2: The instream Intermediate Habitat Integrity Assessment for the Loeka River. ... 17

Table 5-3: The riparian assessment for the Loeka River. .................................................... 17

Table 5-4: The instream assessment for the Itimbiri tributaries ............................................ 18

Table 5-5: The riparian assessment for the Itimbiri tributaries ............................................. 18

Table 5-6: Fish species observed on the Yaligimba concession .......................................... 19

Table 5-7: Endemic taxa, their conservation status and distribution expected on the Yaligimba concession ........................................................................................................ 20

Table 8-1: High Conservation Values (Brown et al., 2013) .................................................. 24



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1 Introduction The Feronia PHC (Feronia) business includes the rehabilitation and operation of three oil palm concessions on the Congo River: in Lokutu (Orientale province), and Yaligimba and Boteka in Equateur Province. Feronia targets a RSPO (Roundtable on Sustainable Palm Oil) certification for its three concessions. Digby Wells Environmental (hereafter Digby Wells) was commissioned by Feronia PHC to conduct aquatic ecological specialist studies on their Yaligimba oil palm concession in the central Congo basin, as part of a High Conservation Value (HCV) environmental assessment.

The Congo River has the second greatest discharge of any river in the world (the Amazon River has the largest), with the central Congo basin containing swamps and wetlands estimated to cover at least 120,000 km2. There is a generally poor scientific understanding of the aquatic ecology due to poor infrastructure, and socio-economic factors such as political instability and social unrest (Campbell, 2005). Based on observations made by Digby Wells during the site survey, it is clear that the health of the aquatic ecosystems is currently threatened by activities which are causing loss of habitat and, therefore, aquatic biodiversity.

The aim of the study was to establish the conservation value of the aquatic ecosystems associated with the Yaligimba oil palm concession. In order to define the conservation value it is essential to establish the baseline condition of the rivers and subsequently, the current conservation status of the aquatic ecosystems. The study established an estimate of present ecological status, degree of endemism, conservation status of species and overall conservation value of the associated river courses.

This study forms a component of the overall biodiversity assessment for the HCV assessment of the Yaligimba concession.

2 Methodology

2.1 Expertise of the Aquatic Specialist Russell Tate is an aquatic ecologist in the Biophysical Department of Digby Wells, he is a Professional Natural Scientist, registered with the South African Counsel for natural scientific professions, who holds a Master’s degree in aquatic health from the University of Johannesburg in South Africa. Russell has published scientific papers and has completed aquatic assessments in several African countries including Botswana, Democratic Republic of Congo (DRC), Mali, Senegal, Ivory Coast, South Africa, and Mozambique. He has carried out focused tropical assessments in Cameroon, Liberia and Ghana.

2.2 Survey

A single survey was completed at Yaligimba from the 24th to the 27th of January 2015. This coincides with the lower flow period in DRC. The rationale for surveying at this time is that the river systems on the Yaligimba were flowing adequately (but not flooding) to allow for the effective biological assessment.



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2.3 Water Quality

Water quality was measured using a calibrated Extech DO 700 multimeter. Constituents considered in this study included; temperature (ºC), pH, dissolved oxygen (mg/l) and conductivity (µS/cm).

2.4 Aquatic Habitat The availability and diversity of habitat is important to consider in aquatic assessments due to the reliance and adaptations of aquatic biota to specific habitats (Barbour et al., 1996). Habitat quality and availability assessments are usually conducted alongside biological assessments that utilise fish and macroinvertebrates. Aquatic habitat (habitat) was assessed through observations on each river system in the study area. The methods used for the assessment are set out by Bain and Stevenson (1990), Vannote et al., (1980), and Gerber and Gabriel (2002).

The assessment and description of habitat in this study has been used to ascertain the potential presence of taxa that are of HCV or Rare, Threatened and Endangered (RTE). An assessment for the potential of “natural conditions” was completed to determine the conservation value of the river systems (Brown et al., 2013).

2.4.1 Intermediate Habitat Integrity Assessment

In order to define a general habitat, for baseline purposes, the instream and riparian habitat was assessed and characterised according to “Procedure for Rapid Determination of Resource Directed Measures for River Ecosystems (Section D), 1999”.

The Intermediate Habitat Integrity Assessment (IHIA) model was used to assess the integrity of the habitats from a riparian and instream perspective. The habitat integrity of a river refers to the maintenance of a balanced composition of physico-chemical and habitat characteristics on a temporal and spatial scale that are comparable to the characteristics of natural habitats of the region (Kleynhans, 1996). The criteria utilised in the assessment of habitat integrity in the current study are presented in Table 2-1.

Table 2-1: Criteria in the assessment of habitat integrity (Kleynhans, 1996).

Criterion Relevance

Water

abstraction

Direct impact on habitat type, abundance and size. Also implicated in flow, bed, channel and water quality characteristics. Riparian vegetation may be influenced by a decrease in the supply of water.

Flow modification

Consequence of abstraction or regulation by impoundments. Changes in temporal and spatial characteristics of flow can have an impact on habitat attributes such as an increase in duration of low flow season, resulting in low availability of certain habitat types or water at the start of the breeding, flowering or growing season.

Bed Regarded as the result of increased input of sediment from the catchment or a



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Criterion Relevance

modification decrease in the ability of the river to transport sediment (Gordon et al., 1993). Indirect indications of sedimentation are stream bank and catchment erosion. Purposeful alteration of the stream bed, e.g. the removal of rapids for navigation (Hilden & Rapport, 1993) is also included.

Channel

modification

May be the result of a change in flow, which may alter channel characteristics causing a change in marginal instream and riparian habitat. Purposeful channel modification to improve drainage is also included.

Water quality modification

Originates from point and diffuse point sources. Measured directly or alternatively agricultural activities, human settlements and industrial activities may indicate the likelihood of modification. Aggravated by a decrease in the volume of water during low or no flow conditions.

Inundation Destruction of riffle, rapid and riparian zone habitat. Obstruction to the movement of aquatic fauna and influences water quality and the movement of sediments (Gordon et al., 1992).

Exotic macrophytes

Alteration of habitat by obstruction of flow and may influence water quality. Dependent upon the species involved and scale of infestation.

Exotic aquatic

fauna

The disturbance of the stream bottom during feeding may influence the water quality and increase turbidity. Dependent upon the species involved and their abundance.

Solid waste disposal

A direct anthropogenic impact which may alter habitat structurally. Also a general indication of the misuse and mismanagement of the river.

Indigenous vegetation removal

Impairment of the buffer the vegetation forms to the movement of sediment and other catchment runoff products into the river (Gordon et al., 1992). Refers to physical removal for farming, firewood and overgrazing.

Exotic vegetation

encroachment

Excludes natural vegetation due to vigorous growth, causing bank instability and decreasing the buffering function of the riparian zone. Allochtonous organic matter input will also be changed. Riparian zone habitat diversity is also reduced.

Bank erosion

Decrease in bank stability will cause sedimentation and possible collapse of the river bank resulting in a loss or modification of both instream and riparian habitats. Increased erosion can be the result of natural vegetation removal, overgrazing or exotic vegetation encroachment.

The relevant criteria are then weighted and scored according to Kleynhans (1996), as seen in the tables below (Table 2-2 and Table 2-3).



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Table 2-2: Table giving descriptive classes for the assessment of modifications to habitat integrity (Kleynhans, 1996).

Impact Category

Description

Score

None

No discernible impact or the modification is located in such a way that it has no impact on habitat quality, diversity, size and variability.

0

Small

The modification is limited to very few localities and the impact on habitat quality, diversity, size and variability are also very small.

1-5

Moderate

The modifications are present at a small number of localities and the impact on habitat quality, diversity, size and variability are also limited.

6-10

Large The modification is generally present with a clearly detrimental impact on habitat quality, diversity, size and variability. Large areas are, however, not influenced.

11-15

Serious The modification is frequently present and the habitat quality, diversity, size and variability in almost the whole of the defined area are affected. Only small areas are not influenced.

16-20

Critical The modification is present overall with a high intensity. The habitat quality, diversity, size and variability in almost the whole of the defined section are influenced detrimentally.

21-25

Table 2-3: Criteria and weights used for the assessment of habitat integrity (Kleynhans, 1996).

Instream Criteria Weight Riparian Zone Criteria Weight

Water abstraction 14 Indigenous vegetation removal 13

Flow modification 13 Exotic vegetation encroachment 12

Bed modification 13 Bank erosion 14

Channel modification 13 Channel modification 12

Water quality 14 Water abstraction 13

Inundation 10 Inundation 11

Exotic macrophytes 9 Flow modification 12

Exotic fauna 8 Water quality 13

Solid waste disposal 6

TOTAL 100 TOTAL 100



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Scores are then calculated based on ratings received from the assessment. The estimated impacts of the criteria are then summed and expressed as a percentage to arrive at a provisional habitat integrity assessment. The scores are then placed into the Intermediate habitat integrity categories (Kleynhans, 1996) as seen in Table 2-4.

It should be noted that the IHIA was based on regions assessed in the current studies and therefore may only constitute the assessment of conditions within a 30 km length of the considered water courses.

Table 2-4: Intermediate habitat integrity categories (Kleynhans, 1996).

Category Description Score

A Unmodified, natural. 90-100

B Largely natural with few modifications. A small change in natural habitats and biota may have taken place but the ecosystem functions are essentially unchanged.

80-90

C Moderately modified. A loss and change of natural habitat and biota have occurred but the basic ecosystem functions are still predominantly unchanged.

60-79

D

Largely modified. A large loss of natural habitat, biota and basic ecosystem functions has occurred.

40-59

E

The loss of natural habitat, biota and basic ecosystem functions is extensive.

20-39

F

Modifications have reached a critical level and the lotic system has been modified completely with an almost complete loss of natural habitat and biota. In the worst instances the basic ecosystem functions have been destroyed and the changes are irreversible.

0-19

2.5 Fish

A number of limitations restricted the amount of quantitative sampling on the Yaligimba concession (Section 3).

The fish assessment for the Yaligimba concession was completed using qualitative data based on observations by the Digby Wells team as well as the local knowledge of local fisherman.

The endemic and endangered species lists that may be found at Yaligimba were compiled based on information from Fishbase (www.fishbase.org). Taxa which were identified in rivers/tributaries from the habitat types observed on site were then isolated from taxa found



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outside the considered river systems. The distribution of fish was obtained from range maps of the International Union for Conserved Nature (IUCN) red list.

The identification of fish was confirmed using Paugy et al. (2003), Skelton (2001) and Verlag (2004). Furthermore, photos were uploaded to the Africhthy website (https://www.flickr.com/groups/africhthy.); specialists use this website to assist peers identify species, particularly in areas which are unknown from previous studies.

2.5.1 Conservation Status and Expected Species

The conservation status of all fish species captured and those expected were verified against the following institutions and organisations:

■ IUCN (IUCN) Red list of threatened species (IUCN); and

■ Fishbase (www.fishbase.org).

3 Limitations The large size of the Yaligimba concession, and poor accessibility to the river sites, made the conventional assessment of the river systems difficult (compounded by the time limits Digby Wells had at Yaligimba). Based on these limitations, Digby Wells adopted rapid habitat assessment methodologies to complete the fish studies.

An additional issue that affected sampling were the large numbers of people from nearby communities who were interested in the assessment; as electroshocking was being used this presented health and safety issues (Figure 3-1).

Figure 3-1: Large Crowds at aquatic survey site, Yaligimba (January 2015).

4 Study Sites, General Aquatic Habitat and Expected Diversity

4.1 General Aquatic Habitat and Expected Diversity

This study focused on the aquatic ecosystems around the town of Yaligimba, on the outskirts of the Yaligimba concession. The study area is on the northern bank of the Itimbiri River, a

http://www.flickr.com/groups/africhthy.)%3B



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tributary of the Congo River, approximately 40 km east of the town of Bumba, Equateur Province.

The study area is within Cuvette Centrale freshwater Ecoregion (Thieme et al. 2005). Based on desktop information, the major aquatic habitat type in this region is tropical/subtropical floodplain rivers with wetland complexes. The ecoregion has flat topography, approximately 300 m above sea level. It has an equatorial and wet climate with rainfall distributed evenly throughout the year. The average annual rainfall in the ecoregion is between 1,500 mm and 2,000 mm with mean annual temperatures at 24 ºC (Theime et al. 2005).

The Cuvette Centrale freshwater ecoregion has a variety of habitats including open waters, small streams, coves, meadows of aquatic vegetation, permanent swamps and extensive floodplains; there are also floating Eichhornia masses Riparian zones are flooded seasonally resulting in permanent swamp forests with few dominant species but rich floral diversity.

According to), The Cuvette Centrale freshwater ecoregion is host to a rich fish fauna with approximately 300 different fish species (Abel et al. (2008), Figure 4-1); 12 known taxa are specifically endemic to the Cuvette Centrale freshwater ecoregion (Figure 4-2).

Figure 4-1: Freshwater fish species richness of the Freshwater Ecoregions of the world (Abel et al. 2008).



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Figure 4-2: Endemic freshwater fish species richness of the various Freshwater Ecoregions of the world (Abel et al. 2008).

It should be noted that although 300 taxa are expected to occur, only 240 species have been documented (Abel et al. 2008). This lack of documentation can be attributed to the fact that very few biological studies have been conducted in this ecoregion. In general, the Cuvette Centrale freshwater ecoregion is considered to have few threatened taxa (Brooks et al. 2011). The central factor contributing to the low number of threatened taxa is based on the remote locations of tributaries surrounded by large undisturbed area.

4.2 Aquatic Habitat of the Yaligimba Concession

This study focussed on the aquatic ecosystems directly associated with the Yaligimba concession (and therefore not the main-stem of the Itimbiri River). Seven sites were assessed (Figure 4-6); coordinates in Table 4-1 may be used as reference sites for future assessments.

Table 4-1: Global Positioning System (GPS) co-ordinates for the aquatic sampling points of the Yaligimba oil palm concession (January 2015 survey).

Site GPS co-ordinate

River and tributaries Loeka and associated tributaries

YAL1 2.207942° 22.804136°



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Site GPS co-ordinate

River and tributaries Loeka and associated tributaries

YAL2 2.294873° 22.895023°

YAL3 2.306810°° 22.891895°°

YAL4 2.389292° 22.953682°

YAL5 2.446588° 22.940285°

River and tributaries Associated tributaries of the Itimbiri

YAL6 2.245499° 22.980677°

YAL7 2.351088° 23.053573°

Two distinct tributaries were the focus of this study (i.e., the Loeka River and Itimbiri tributaries). Both of the tributaries contained different habitat types with reference to local topography, land use patterns and rainforest cover. The dominant longitudinal zonation of the sampling sites was found to be in the “lower foothills” (Rowntree and Ziervogel, 1999).

Most of the sampling sites were on smaller tributaries of the Itimbiri and Loeka River and as such had very different habitats to the main stem river systems. The tributaries of the Loeka River are characterised by dense riparian forest, with shallow water and sandy substrate (Figure 4-3). In the remote areas, dense woody and leafy substrates were observed (Figure 4-4). The water of the rivers was dark and moderately flowing with variable aquatic vegetation including Eichhornia crassipes and Nymphaea nouchali.



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Figure 4-3: Typical tributary at YAL5.

Figure 4-4: Aquatic substrates in the upper tributaries. (A) YAL2, (B) YAL5.

Figure 4-5: Aquatic vegetation at sites on the Yaligimba concession, January 2015. (A): Eichhornia crassipes and (B): Nymphaea nouchali at the site YAL4.



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Figure 4-6: Aquatic sampling points for the Yaligimba aquatic survey (January 2015).



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The main stem of the Loeka River is a wide, fast flowing (in January), large (±10m), deep, dark and bordered by a floodplain (Figure 4-7) with an extensive floating reed mass of mixed vegetation dominated by papyrus (Cyperus papyrus) (Figure 4-8).

Figure 4-7: Typical river channel in the Loeka River at YAL1.

Figure 4-8: Well-defined floodplain of the Loeka River at YAL1.

The sites on the Itimbiri River tributaries are very similar to those on the Loeka, except not wide (±5m) (Figure 4-9). Typical aquatic habitats at the sites in the larger rivers are dominated by marginal and instream submerged vegetation including root wads of Papyrus and floating vegetation (Figure 4-10). The general aquatic habitat at each site is presented in Table 4-2.



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Figure 4-9: Typical habitat in the tributaries of the Itimbiri River (YAL6).

Figure 4-10: Photographs illustrating typical aquatic habitats in the larger tributaries at YAL1 (A) and YAL6 (B).



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Table 4-2: General habitat photographs at each site during the January 2015 survey.

Site Photograph

YAL1

YAL2

YAL3



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Site Photograph

YAL4

YAL5

YAL6



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Site Photograph

YAL7

5 Results

5.1 Water Quality

In situ water quality results obtained during the January 2015 Yaligimba survey are presented in Table 5-1.

Table 5-1: In situ water quality results survey at the Yaligimba concession (January 2015).

Constituent YAL1 YAL2 YAL3 YAL4 YAL5 YAL6 YAL7

Temperature (ºC) 23 20 21 20 20 21 19

pH 5.3 5.5 5.1 6 4 5.9 6.3

Conductivity (µS/cm)

9

34

24

14

16

10

17

Dissolved oxygen (mg/l)

3.5

4.2

4

5.1

6

5.4

6.6

The results of the in situ analysis showed temperatures at the sites were relatively constant ranging between 20 ºC at YAL2, YAL4 and YAL5 to 23 ºC at YAL1. The power of hydrogen (pH) varied between 4 at YAL5 to 6.3 at YAL7. Dissolved solids, measured as electrical conductivity (µS/cm) ranged from a low of 9 µS/cm at YAL1 to 34 µS/cm at YAL2. Dissolved oxygen concentrations ranged from 4 mg/l at YAL2 to 6.6 mg/l YAL7.

5.2 Intermediate Habitat Integrity Assessment The intermediate habitat integrity assessment was carried out in each sub-catchment. The results of these assessments are therefore presented per each river (Loleka and Itimbiri



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River tributary). The Loeka River IHIA took into consideration the survey of sites YAL1, YAL2, YAL3, YAL4 and YAL5 which is presented in Table 5-2 and Table 5-3.

Table 5-2: The instream Intermediate Habitat Integrity Assessment for the Loeka River.

Instream Average score Score

Water abstraction 0.00 0.00

Flow modification 4.00 2.08

Bed modification 1.67 0.87

Channel modification 1.00 0.52

Water quality 3.33 1.87

Inundation 1.00 0.40

Exotic macrophytes 6.00 2.16

Exotic fauna 0.00 0.00

Solid waste disposal 6.67 1.60

Total Instream 90 Category class A

Table 5-3: The riparian assessment for the Loeka River.

Riparian Average score Score Indigenous vegetation

removal 6.00 3.12

Exotic vegetation encroachment

3.00 1.44

Bank erosion 1.33 0.75






Total Riparian 90



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Riparian Average score Score Category class A

The results of the IHIA show that instream and riparian habitats of the Loeka River was found to be in a natural state (class A). Sites included in the Itimbiri tributaries IHIA were YAL6 and YAL7. The results of the IHIA assessments are presented in Table 5-4 and Table 5-5.

Table 5-4: The instream assessment for the Itimbiri tributaries.

Instream Average score Score



Bed modification 8.00 4.16




Exotic macrophytes 5.00 1.80

Exotic fauna 0.00 0.00

Solid waste disposal 10.00 2.40

Total Instream 79 Category class C

Table 5-5: The riparian assessment for the Itimbiri tributaries.

Riparian Average score Score Indigenous vegetation

removal 11.50 5.98

Exotic vegetation encroachment

10.00 4.80

Bank erosion 2.50 1.40






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Riparian Average score Score



Total Riparian 80 Category class B

The results of the IHIA show that instream habitat of the Itimbiri tributaries is currently in a moderately modified status (class C) with the riparian habitat currently in a class B or largely natural status.

5.3 Fish Assessment

5.3.1 Fish Community Assessment

Several fish species were observed on the Yaligimba concession during the qualitative assessment. A species list of the observed species is presented in Table 5-6.

Table 5-6: Fish species observed on the Yaligimba concession.

Species Conservation status Sites observed

Channa obscura NE YAL1

Clarias theodorae LC YAL1, YAL6, YAL7

Ctenopoma kingsleyae LC YAL1

Hemichromis fasciatus LC YAL1, YAL3

Hepsetus odoe LC YAL1

Marcusenius macrolepidotus LC YAL1

Papyrocranus congoensis LC YAL1

Protopterus dolloi LC YAL1, YAL4

Seven species of fish considered to be “least concern” and one “not evaluated” were observed during the January 2015 survey.

5.3.2 Endemic and conservation assessment

The results of the assessment for potential endemic species which are thought to (potentially) occur within the aquatic ecosystems of the Yaligimba concession are presented in Table 5-7.



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Table 5-7: Endemic taxa, their conservation status and distribution expected on the Yaligimba concession.

Species

Conservation status

Distribution

Acanthocleithron chapini LC Regional

Alestopetersius compressus LC Regional

Barbus candens LC National

Barbus fasolt LC Regional

Barbus humeralis LC National

Barbus lukusiensis LC National

Barbus matthesi LC Regional

Barbus stanleyi LC Regional

Belonophago hutsebouti LC National

Brachypetersius pseudonummifer LC Regional

Campylomormyrus mirus LC Regional

Campylomormyrus numenius LC National

Chromidotilapia schoutedeni LC Regional

Clariallabes laticeps LC National

Clariallabes uelensis LC Regional

Clypeobarbus congicus LC Regional

Congocharax olbrechtsi LC Regional

Hemistichodus mesmaekersi LC Regional

Micralestes lualabae LC Regional

Mormyrops sirenoides LC Regional



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Species

Conservation status

Distribution

Paradoxoglanis parvus LC Regional

Pollimyrus pulverulentus LC Regional

Pseudocrenilabrus nicholsi LC Regional

Stomatorhinus fuliginosus LC Regional

Stomatorhinus patrizii LC Regional

Synodontis centralis LC Regional

Based on the results of the endemic assessment, a total of 26 endemic taxa are expected to be present in or associated with the Yaligimba concession. According to the IUCN Red list, all of the expected taxa are considered to be of “least concern”. When considering the total list of endangered taxa in the DRC, no RTE taxa were expected to be present on the Yaligimba concession.

6 Discussion

6.1 Water Quality

Results of the water quality tests are as follows:

■ The water temperature of the rivers in the Yaligimba concession was warm and averaged around 20ºC. These are natural temperatures when considering the habitat types (full cover) tropical streams.

■ The pH was found to be slightly acidic within the rivers of the Yaligimba concession. The majority of the sites had slightly acidic pH levels (4-6.3).

The acidic sites are likely due to the decomposition of allochthonous material and seepage of occalic acids/tannins from decaying leafy material, these pH levels are therefore seen as natural (Deano and Robinson, 1985).

■ Dissolved solids, measured as conductivity, were in low concentrations on the Yaligimba concession with the highest levels recorded at YAL2. These low concentrations show that anthropogenic activities on the concession do not contribute large amounts of solutes to the local river systems. Furthermore, these low dissolved solid concentrations indicate the large degree of dilution capacity available in these local river systems and illustrate typical and natural tropical conditions (Balek, 1983).



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■ Dissolved oxygen concentrations were low at all of the sites which had low gradients

or swampy characteristics. These low concentrations are caused through the removal of oxygen by decaying organic matter and are, therefore, viewed as natural.

In conclusion, water quality results illustrate conditions are typical of a tropical river system.

6.2 Intermediate Habitat Integrity Assessment The integrity of the aquatic habitats considered in this study would have a direct impact on the presence of the various aquatic biota (certain species are more sensitive than others).

6.2.1 The Loeka River

When considering the results obtained for the IHIA completed for the Loeka River system, the conclusions are that modification was frequently absent from the sites considered in the river, indicating that the river is in a natural state. Minor impacts were observed as a result of road crossings which altered natural flow regimes.

Alien invasive vegetation was observed at four of the sampling sites, however the abundance and cover of the alien vegetation was limited in extent. Thus, the criteria was scored a moderate score (Figure 4-5).

Impacts on water quality were visible near communities; there is no formal waste management system and large quantities of solid waste were common. Streams are used for bathing, watering animals, fishing and laundry. Considering that the impacts were limited to areas around villages, the instream impacts and the overall status of the instream habitat for the Loeka River was found to be largely natural.

The riparian habitat in the Loeka River is typical of those expected in the Cuvette Centrale, with extensive floodplains in the main stem of the river and a dense network of submerged vegetation.

Within the 50km linear section of the Loeka River that was studied, the impacts were concentrated in the southern portion of the concession. The northern area is largely natural with sporadic modification. Digby Wells concluded the submerged floodplain and main stem of the Loeka River are near pristine and this is due to the inaccessibility of the system.

Based on the overall results of the IHIA, the Loeka River system was found to be in largely natural state.

6.2.2 The Itimbiri Tributaries

The two tributaries of the Itimbiri River, with their sources on the south eastern boundary of the Yaligimba concession, were the subject of this study. Small villages, with the tributaries flowing on either side, are adjacent to the tributaries considered.

There are several low water crossings over these tributaries, including the N6 road to Bumba. These crossings cause flow modification, bed modification and result in inundation. The close proximity of communities and the active use of the rivers systems have resulted in



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large amounts of solid waste accumulating at some sites. The impact of the (accumulated) modification of rivers was assessed as resulting in a moderately modified instream habitat within the Itimbiri tributaries.

The riparian habitat of the Itimbiri tributaries had large sections of land where indigenous vegetation had been removed, including large trees, for subsistence agriculture by local communities. Exotic vegetation such as Eichhornia crassipes was also found at the study areas. However, during the survey no active vegetation removal was observed.

Based on the extent of the current impacts on the riparian habitat of the Itimbiri tributaries, the riparian conditions are considered largely natural.

6.3 Fish assessment The results of the endemic assessment indicate that a total of 26 endemic taxa are expected in or associated with the Yaligimba concession. Of these endemic taxa, 20 are considered to be regionally endemic (Upper and Middle Congo River) with six nationally endemic to the whole Congo River Basin (Fishbase, IUCN).

The fish in the rivers and associated with the Yaligimba concession are probably not unique. The results of the qualitative assessment indicated wide use of several fish species by local communities (subsistence) which are considered to be sensitive to water quality modification (Mormyridae) and tertiary predators such as Hepsetus odoe. The presence of these species provides confirmation of the natural status, as the IHIA results obtained in this study.

Figure 6-1: Channa obscura observed at YAL1.

Common species recorded at the study sites included Clarias theodorae and Hemichromis fasciatus. The air-breathing Protopterus dolloi and common Channa obscura were often seen as, which was expected with extensive floodplains and swamp habitats (Figure 6-1).

The conservation status of the observed taxa, as well as the majority of the expected endemic species was assessed to be of “least concern”.



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In conclusion, when considering the available data and qualitative assessment of the fish fauna on the Yaligimba concession, the fish fauna is considered as being common.

7 Recommendations Based on the results of this study the following recommendations are made:

■ The current buffer zones between the plantations and the river systems are sufficient and should be maintained (i.e no planting should occur within 50 m of these river systems).

8 High Conservation Value Aspects Table 8-1 is based on the guidelines in Brown et al. (2013) It should be noted that the table has been populated based on the preliminary findings of this report; detailed information is presented in the HCV report (Digby Wells, 20151).

Table 8-1: High Conservation Values (Brown et al., 2013).

HCV1 Present/absent Rationality

Presence of RTE species

Absent

Not found to be present in studies

Presence of protected areas for RTE taxa

Absent

Not within study focus area

Presence of endemic, highly range limited species

Absent

Wide range of endemic species

Critical dispersal routes for fish

Absent

No major river systems


Rivers with natural flow regimes

Present

Natural system

Rivers without downstream and upstream barriers

Present

Natural system

Unmodified river channels Present Natural system

Unmodified thermal, sediment and nutrient regimes

Present

Natural system



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Land cover conversion below threshold of concern

Not considered

Not considered

Rivers without invasive taxa Absent Invasive taxa observed


Rare, threatened or endangered freshwater ecosystems

Absent

Not unique or rare


Floodplains and wetlands Present Floodplains present

Riparian forests Present Observed on site

Unleveed floodplains Present Observed on site

Areas with a critical recharging effect on aquafers used for potable water

Absent

Not observed

High surface water yield areas

Present

Not unique/uncommon

Vegetated areas upstream of critical water supplies

Present

Not unique/uncommon


Water sources necessary for access to basic drinking water and sanitation

Present

Observed on site

Freshwater animal populations relied upon by local communities

Present

Observed on site


Water bodies of high religious or cultural significance

Digby Wells, 20152

Digby Wells, 20152

Freshwater products with Digby Wells, 20152 Digby Wells, 20152



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cultural values



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9 Conclusions The conclusions of the study are:

■ The assessment of aquatic ecological conditions in the rivers associated with the Yaligimba concession revealed the systems are largely natural.

■ Impacts on river systems include deforestation and riparian habitat loss. However, these are limited in extent.

■ The assessment of local aquatic biota confirmed that fish communities are largely common species.

■ The assessment for RTE ichthyofaunal taxa revealed a general absence of endangered fish species in the Yaligimba region.

■ Further assessment by Digby Wells revealed that the endemic taxa expected to be present, have wide distributions and are of least concern in terms of conservation statuses.

The degree of endemism on the Yaligimba concession was concluded to be low due to the large distribution of endemic taxa in the DRC.

10 References Abel R, Thieme ML, Revenga C, Bryer M, Kottelat M, Bogutskaya N, Coad B, Mandrak N, Contreras Balderas S, Biussing W, Stiassny MLJ, Skelton P, Allen GR, Unmack P, Naseka A, Ng R, Sindorf N, Robertson J, Armijo E, Higgins JV, Heibel TJ, Wikramanayake E, Olson D, Lopez HL, Reis RE, Lundberg JG, Mark H, Perez S, Petry P. 2008. Freshwater Ecoregions of the World: A new map for biogeographic units for freshwater biodiversity conservation. Bioscience. 58:403-414.

Bain MB, Stevenson N. 1999. Aquatic habitat assessment: Common methods, American Fisheries Society, Bethesda, Maryland.

Balek J. 1983. Hydrology and water resources in tropical regions. Elsevier Science. Amsterdam, Netherlands.

Barbour MT, Gerritsen J, White JS. 1996. Development of a stream condition index (SCI) for Florida. Florida Department of Environmental Protection: Tallahassee, Florida.

Brooks EGE, Allen DJ, Darwall WRT. 2011. The status and distribution of freshwater biodiversity in central Africa. IUCN. Cambridge. United Kingdom.

Brown E, Dudley N, Lindhe A, Muhtanian DR, Stewart C, Synnott T. 2013. Common guidance for the identification of High Conservation Values. HCV Resource Network.

Campbell D. 2005. The World’s Largest Wetlands: Ecology and Conservation. Cambridge University Press.



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Deano PM, Robinson JW. 1985. The effect of decaying leaves on the pH and buffer capacity of water. Journal of Environmental Science and Health. 20: 903–911.

Digby Wells Environmental 1. 2015 High Conservation Value Assessment, Lokutu Oil Palm Concession, CDC2950.

Digby Wells Environmental2. 2015. Social Assessment for Feronia PHC’s Oil Palm Plantations in the Democratic Republic of Congo, Stakeholder Engagement Plan. CDC2950.

Fishbase. 2015. Available at: http://www.fishbase.org/. Accessed 2015/04/14.

Gerber A, Gabriel MJM. 2002. Aquatic Invertebrates of South African Rivers: Field Guide. Institute for Water Quality Services, Department of Water Affairs and Forestry, Pretoria.

Hellawell K. 1977. Biological surveillance and water quality monitoring. Biological monitoring of inland fisheries. 69–88.

IUCN. 2015. Available at http://www.iucnredlist.org/details/181572/0. Accessed 2015/04/14.

Kleynhans CJ. 1996. A qualitative procedure for the assessment of the habitat integrity status of the Luvuvhu River. Journal of Aquatic Ecosystem Health 5: 41–54.

Paugy D, Leveque C, Teugels GG, Bigorne R, Romand R. 1990. Freshwater fishes of Sierra

Leone and Liberia: Annotated checklist and distribution. Revision Hydrobiology tropical. 23:

329–350.

Rowntree KM, Ziervogel G. 1999. Development of an index of stream geomorphology for the assessment of river health. National Aquatic Ecosystem Biomonitoring Programme. Report Series No.7.

Skelton PH. 2001. A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa.

Thieme ML, Abell R, Stiassny MLJ, Skelton P. 2005. Freshwater Ecoregions of Africa and Madagascar: A Conservation Assessment. World Wildlife Fund.

Toham AK, Teugels GG. 1999. First data on an Index of Biotic Integrity (IBI) based on fish assemblages for the assessment of the impact of deforestation in a tropical West African river system. Hydrobiologia. 397: 29–38.

Vannote RL, Minshall GW, Cummins KW, Sedell JR Cushing CE. 1980. The River Continuum Concept. Canadian Journal of fisheries and Aquatic Science. 37: 130–137.

Verlag BS. 2004. The Cichlid Fishes of Western Africa. First edition. Germany.

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