Sunday, March 22, 2015

RESEARCH REPORT: KUNENE RIVER BIOLOGICAL SURVEY, OCTOBER 2014


   Mikael N. Ekandjo (CFRT)
  Gosbert Hamutenya (SFRB)

 October 2014  
           

 The full report is available on request

1. BACKGROUND

The Kunene River originates in the Bie plateau, close to Huambo at about 1750 meters above sea level. The upper 400 km are relatively steep, whereas the middle section has a lower gradient forming a marshy floodplain. When meeting the Namibian border at Ruacana, the river forms a 120 m waterfall and the remaining distance to the sea is steep with a gradient of 1:447. From Ruacana the fast flowing river forms the border between Angola and Namibia. (Tvedten et al 1994) Due to the low population density and the fact that the Himba and Zemba that inhabit the area along the lower Kunene do not utilise the fish as food, the fish stocks are presently not exploited to any significant degree (Tvedten et al 1994, Hay et al, 2008). According to Tvedten et al, (1994), the proposed second hydropower scheme on the lower Kunene River may have an impact on the current situation of freshwater fisheries exploitation as the construction work may brings in fish eater populations from other regions that may influence the local Himba/Zemba communities to start eating fish. In Total 46 fresh water fish species were found in the Namibian part of the Kunene River in the past years. Of those 46, five are endemic to the Kunene River (Hay et al, 2008).
The biological assessment of fish species have been carried out over years. To date, there are data available since 1994, however due to budgetary constraint; this survey was not conducted during 2013. It is therefore a tradition that a similar survey is carried out each and every year during the same season and at designated stations. This is done so that data recorded are comparable to those collected other years. These surveys are carried out, focussing on the biological assessment of the fishery of each river system. This includes species composition, sizes in terms of length and weight as well as reproductive stages. This specific report will mainly focus on species composition at various stations, catch per unit effort (CPUE) and lastly will compare this survey’s fish catches to that of December 2012.

                 1.1.     Study area

The area sampled is part of Kunene River along the Namibia Angola border. Four stations were sampled along the Kunene River, plus Olushandja Dam (Etaka) that directly receive water from the Kunene River via the Kallueque- Oshakati Canal. The four stations along the river are: Hippo Pools, just downstream of Ruacana Hydropower Station, Swartboisdrifft, further downstream of Ruacana, Epupa, immediately upstream of the falls and Otjinugua, further downstream of Epupa Falls (Figure 1). These are among some other stations that have been sampled along the Kunene River for many passed years.
Fig.1. A map showing a study area with various stations sampled (adopted from Hay et al, 2008) 
 Table 1. A table showing sampling stations and their GPS coordinates

2. MATERIALS AND METHODS

                 2.1.     Materials used

        Two panels of gill nets consisting eleven different mesh sizes were used in this survey. 
        The eleven different mesh sizes (12, 16, 22, 28, 35, 45, 57, 73, 93 118 and 150 mm) of 10 m length, multifilament brown gill nets. 
        A 10 m drag net was used to sample smaller fishes that are not caught in gillnets A GRAMI GPS with 5 m accuracy was used to record the positions of sampled sites. 
        A boat mounted with a 25hp engine was used in the river to set nets.
        Two 4x4 cars were used to felly equipments and personnel’s
        A total of six personnel were involved in this survey
        Pasgear habitat and record forms were used to record the data
        Plastic bags and mesh tags were used to carry and indentify catches from each net separate respectively.

                 2.2.     Participants


1. Mikael N Ekandjo (CFRT, Rundu)
2. Gosbert Hamutenya (SFB: Rundu)
3. Erasmus P. Haimene (FRT: Epalela)
4. David Kandunge (FRT: Onavivi)
5. Ismael Kapuka (FRT: Epalela)



Fig. 2. Specimens of a Barbus poechii like species that is referred to as Barbus cf trimaculatus in this report 

3. RESULTS  


3.1. Species Diversity and the Index of Relative Importance

A total of 30 fish species were recorded during the 2014 Kunene Annual Biological survey. The recorded species were ranked based on the Index or Relative Importance (IRI). Of the 30 species caught, the most important species in terms of number was Brycinus lateralis a small characin, amounting to 28.8 % in terms of numbers with an IRI of 36.2 % (Table 1.). This is followed by another characin, Micralestes acutidens with 20.8 % in terms of number, with an IRI 15.3 %. Schilbe intermedius and Labeo ansorgii were the third and fourth most important species caught in terms of both number and weight accounting for 6.5% and 4.4 % in terms of number respectively. However Labeo ansorgii accounted for 12.9 % of weight as compared to Schilbe intermedius 10.1%. With a combination of both weight and numbers, Schilbe intermedius has a high IRI (10.9% as compared to Labeo ansorgii 7.4%.


Although the Kunene River is not exploited commercially, the possible important commercial species such as tilapia and Clarias were among the lowest important species in terms of IRI. This shows that although they are recorded, they may be in a limited numbers as compared to other species.

Measuring and weighing the catch at Swartbois’drif Kunene River, this also involve teaching other participants on features to check when identifying fish species 

4. CONCLUSIONS  


1. The results from this survey indicated that Kunene River is dominated by two smaller characins, Brycinus lateralis and Micralestes acutidens. Tilapias and Clarias are present in a limited numbers.


2. The survey shows no significant differences in CPUE per station, however inter-station differences were observed with Epupa showing a high CPUE in terms of weight while Etaka showing a High


3. CPUE in terms of numbers. Overall, Swarbois’drif recorded the most number of species where as Epupa recorded the least number of species.


4. The two surveys, December 2012 and October 2014 did not show any significant differences in terms of CPUE.

5. RECOMMENDATIONS



1. There is a need for these monitoring and data collection to continue so that data collected over time can be compared to observe the trends.


2. There is a need for a genetic study to study if there are any hybrids between B. poechii and B. trimaculatus.


3. From the results shown by the analysis, this particular survey can be conducted any time between October and December.



4. It is recommended that an inflatable boat be procured to be used in the Kunene Biological Survey replacing the aluminium boats that are always damaged by rough terrain along the Kunene River.


5. The Kunene River mouth should be included as a sampling station 

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