Thursday, December 31, 2015

Inland Fisheries Research Namibia, November 2015



Report by

Francois Jacobs
Senior Fisheries Biologist: KIFI

In conclusion of the 1st phase of the study titled: Evaluating the tag retention potential and effects of PIT tags on the health of Coptodon rendalii a social economic important freshwater fish species.

Tagging of fish species in the display aquarium was initiated on the 30th of September and intensively monitored until the 30th of November 2015. This trial run forms the first phase of the study titled: Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of social economic important freshwater fish species. In brief:
The first phase used PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, which were inserted into the peritoneal cavity or musculature of fishes using a syringe injector. A total of 30 C. rendalli were tagged in the display aquarium. These fish ranged in size (80 min – 185 max) with an average total length of 126.1 mm. An additional 10 C. rendalli was included in this experiment as a control. Apart from minor injuries obtained during the tagging procedure the fish in general show full recovery. After two months of observation, their feeding continues normal with no unnatural/erratic behavioural alterations caused by insertion of tags. This species has thus far maintained a 100% tag retention rate and a 97% survival rate. This experiment was a trial run, to standardize the general and mechanical functioning of KIFI aquarium facilities which according to the results is sufficient to house a large scale experiment.

Zambezi biological survey
The Zambezi biological survey is conducted bi-annually (high and low flow) and intensive data collection is now almost in its 20th year. Data collected during these surveys is paramount in facilitating improved policies and regulations that aim for the sustainable management of our fisheries resources. In addition to biological data these surveys incorporate an active surveillance for fish diseases such as EUS that is in compliance with standards set forth by the FAO.

What follows is a photographic essay of the Zambezi Biological survey carried out during October and November (Table 1). Data collected from this survey is currently being processed. 

Table 1: The program schedule for the Zambezi survey including: system, station and substations. Each of these stations were extensively sampled to obtain the current status of our inland fisheries stocks. (Click on image for better view)



The first survey site was situated next to the ruins of the old Nakatwa site office on the edge of the Kwando River within Mudumo National Park


The Kwando River origins in the eastern parts of Angola with a catchment area of 57 000 km². The floodwaters during the rainy season only reaches this river in June-July due to a winding mainstream and reed marshes. This river is a diverse system consisting of the mainstream (A), small side streams, floodplains, pools and lakes or backwaters (B) which sometimes can become isolated. During this survey a variety of different velocity depth classes and associated habitats were sampled with a series of gill nets (C).


Some species collected in the Kwando River included: (A) Parauchenoglanis ngamensis (Zambezi grunter), (B) Marcusenius macrolepidotus (Bulldog), (C) Pharyngochromis acuticeps (Zambezi bream), (D) Schilbe intermedius (Silver or Butter Catfish)

The survey then proceeded to the Zambezi River and its associated systems including Lake Lisikili, Lake Liambezi and the Chobe River.  Some fish species that were sampled during the survey included:


Photographs: (A) Hemichromis elongatus (Banded jewel cichlid), (B) Petrocephalus catostoma (Churchill), (C) Hydrocynus vittatus (Tiger fish), (D) Barbus poechi (Dash-tail barb)

In general the disease monitoring concluded that the general health of fishes collected during this survey was in a good to very good state. Only 3 individuals were infected with unknown diseases. Diseased fish were collected and preserved for laboratory analysis.


In addition to disease monitoring, stomach content analysis was also carried out throughout the survey and recorded. Hydrocynus vittatus is considered mostly a piscivorous predator yet during a sudden rainstorm this species changed its feeding behaviour to opportunistic food sources like these flying ants.


Filming and documenting fish behaviour in the aquarium at KIFI with a professional filming crew
This activity was conducted from the 15-19th of November and aimed at documenting unique behavioural patterns of selected fish species. Photographing and filming of various fish species was exercised in a controlled environment and video editing techniques was explained and taught to KIFI staff.


Workshops/Training attended
1.      There was no workshops attended this month
2.      Training was in situ during biological survey on water quality, various sampling methods and fish identification procedures
3.      Filming and documenting fish behaviour in the aquarium at KIFI with a professional filming crew was conducted during November and captured behaviour is being analysed. The film crew gave dedicated tutorials on filming and photographing techniques which should enhance the quality of our documenting capabilities. 

New Staff Appointments: Katima Inland Aquaculture Center

Cynthia Monde Kompeli has beem appointed as an Administrative Officer at the sub-Division, Katima/Zambezi Inland Aquaculture Center  in Katima Mulilo as from the 1st of November 2015
Aldrin Maswabi Mwilima was promoted to the post of Senior Fisheries Biologist at Katima as from 1st of October 2015

Aldrin Maswabi Mwilima  joined the ministry as a Junior Biologist in 2012 at NatMIRC, Swakopmund.


He completed grade 12 in 2007 and graduated in 2012. He  carried out his research on fish parasites in Kavango River and Hardap dam for an Honours degree in Fisheries and Aquatic Sciences at UNAM. In May 2012 he was appointed at NATMIRC, Swakopmund as a scientist for Large Pelagics and Line Fishery where he was responsible for sharks, tunas, recreational fishery (e.g. kob, galjoen, steenbrass etc) and line fishery. In October 2015 he was promoted to the post of Senior Fisheries Biologist (SFB) at Katima Inland Aquaculture Center.

He is currently furthering his studies in the field of  Integrated Land Management towards a Master's at the Namibia University of Science and Technology (NUST).

WELCOME TO OUR WORLD...!!!

Skippers (under 25 ton vessel) Training: NAMFI, Walvis Bay, 16-20 November 2015




9 of the 11 participants attending the Skippers training 
Mr. Renier Burger (KIFI) and Gabriel (Luderitz) attended the 5 day Skippers Training course towards a Skippers Licence for under 25 ton vessels hosted by the Namibian Maritime & Fisheries Institute in Walvis Bay from 16 to 20 November 2015. The exam was written on Saturday, 21 November 2015. The course included radio, cartography, emergency procedures, knot making and general seamanship theory. 

Gabriel demonstrating CPR procedures on one of the participants
Some of the knots the would-be skippers had to learn

Friday, November 6, 2015

Mpungu Fish Farm Fish harvest Friday, 30 October 2015

Mpungu Fish Farm Cooperative members and  NYS members supported by Rundu Inland Aquaculture staff  busy with the fish harvest
Fish being weighed after the harvest


Report by: John Hamukwaya: Chief Fishery Biologist & Head: Kavango Regions



The preparation of harvest started on 27 October 2015 when 7 staff members from Rundu travelled to Nkurenkuru and camped on the farm to join two Cuban Experts and three NYS members.  Rundu team consisted of Petrus Hausiku, Sandrina Kudumo, Tedius Nyeliso, Amos Mulundu, Hendrik Afrikaner, Imelda Ngola and Johannes Hamukwaya. Emilia Nambinga, a fishery inspector joined the team on the harvesting day. This is referred to as the MFMR team.

Main activities before the harvesting day were:

1. Moving market size fish from three earth ponds to PP1 to be ready for harvest.
2.Cleaning the fish shop, processing plant and sorrounding areas. This important for food safety and food hygiene. Closing the open space between processing plant and fish shop with fish net to controll the public.
3. Mending nets and fixing floats and sinkers onto new fishing nets.
4. An openning meeting attended by MFMR team and cooperative embers was held to emphasize on the rules, deligation of tasks and expected conduct from everyone during harvest.

Harvesting day:

The fishing activities started at 06h00 in PP4 where we harvested about 359.05 kg of fish. About 292 kg of fish was harvested from PP1. Many clients arrived around 08h00. By around 12:00 pm number of clients dropped and fish were going bad. By 13h00 one businessman came and sold all fish to him. By 15h00 number of clients pick up again but fish finished. We pulled the net again in PP1 and PP4 and harvested 90 kg of fish. This was not enough and many people went back without fish.


An amount of N$13 323.00 was generated. N$12500.00 was divided among the 19 cooperative members. The money divided based on the number of days a member worked on the farm. A day a member was absent due illness or death of closer family and such member provided proof of eith medical certificate or death certificate, that day was counted as worked. In the past cooperatives share the money in equal share. This was changed at the beginning of the year. However, some few members wanted  to withdraw at harvest without success. An amount of about N$800.00 was left to buy seeds for the vegetable gardens.



After the harvest and before money was distributed a closing meeting was done. Here a new concept to improve production was introduced and welcomed by cooperative members. The concept is that each member will have his or her own plot. The garden will be divided into 19 equal plots. The seeds and manure will be provided from the farm account. The ministry will ensure each cooperative member has access to water from evaporation pond.


Mr. Hamukwaya, Chief Fishery Biologist appreciated the collective effort from cooperatives, NYS, Cuban Experts and MFMR staff and urged the team to double their effort for an improved result during the next season.

Mr. Hamukwaya surprised good performers with monetary rewards as follow:

First prize      : N$100.00
Second prize: N$  75.00
Third prize     : N$   50.00
Total                : N$225.00

The last day, 31 November 2015 was a clean up, logistic and travelling back to Rundu.

Challenges and recommendation:

The harvest target was at least 1 MT. This was not achieved may be due to:

1. Lack of fish feed because there are many small fish in PP4 which we thought reached harvest-able size. Unfortunately they did not. Sufficient fish feed must be available on the farm at all times.

2. Fingerlings were not available on time. This means lack of fingerling supply may contribute too. Broodstock should be at Mpungu Fish Farm to complement KIFI and Ongwediva hatcheries.

3. Cooperative members to re-asses their commitment and dedication in an equal individual manner to the improved future success of the fish farm. 

Tuesday, November 3, 2015

New Staff Appointment at KIFI: Naumi Stellah Libala: Fisheries Research Technician


Naumi Stellah Libala


Naumi Stellah Libala is a 26 years old lady from the Zambezi region. She completed her high school education at Saint Kizito College in Katima Mulilo in the year 2007. She then obtained her Bsc honours degree in Molecular biology and Biochemistry from the university of Namibia in 2014. Her research project was microbial survey of fruit spoilage microbes in Windhoek supermarkets. She did her practical attachments at the Central Veterinary Laboratory (CVL) in the Ministry of Agriculture, Water and Forestry in 2014. In 2015 she worked in the Ministry of Education, Arts and Culture  as a Biology and Life Science teacher at Sanjo Senior Secondary School in Zambezi region for 6 months from May to end of October.  She officially assumed duty as a Fisheries Research Technician with the Inland Fisheries Research Section at Kamutjonga Inland Fisheries Institute in the Ministry of Fisheries and Marine Resources  as from the beginning of November 2015.

Welcome to the KIFI family...!!! We wish you a pleasant stay.

Monday, November 2, 2015

Inland Fisheries Research, October 2015 monthly progress


Compiled by: Mr. Francois Jacobs              
Senior Fisheries Biologist (KIFI)


Progress for study titled: Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of social economic important freshwater fish species.

Tagging of fish species in the display aquarium was initiated on the 30th of September and forms part of the study titled: Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of social economic important freshwater fish species. In brief:
Fishes were conditioned in aquarium facilities and general environmental conditions were kept constant. Individual fishes were collected using a hand held scoop net. Suitable fishes were submerged in an aerated tagging container, after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was cleaned in ethanol before use and hands were sterilised with Betadine (Adcock Ingram Ltd, Bryanston, South Africa). Thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity or musculature of fishes using a syringe injector. Thereafter fish were allowed to recover and released back into aquarium.
A total of 30 C. rendalli were tagged in the display aquarium. These fish ranged in size (80 min – 185 max) with an average total length of 126.1 mm (Table 1). An additional 10 C. rendalli was included in this experiment as a control. Apart from minor injuries obtained during the tagging procedure the fish in general show full recovery. After two weeks of observation, their feeding continues normal with no unnatural/erratic behavioural alterations caused by insertion of tags. This species has thus far maintained a 100% tag retention rate and a 97% survival rate. Continues monitoring is being carried out.

Table 1: Coptodon rendalli that was PIT tagged in the Aquarium of KIFI to assess: tag retention potential and general fish health of this species. 
(click on image for a better view)


          
Progress for study titled: The life history strategies of two social economic important freshwater fish species Serranochromis angusticeps and Serranochromis altus in the Kavango River.
This study aims to identify the life history strategies of two sympatric large predatory fish species (Serranochromis altus and Serranochromis angusticeps) which has commercial, subsistence and recreational importance in the Kavango River. This aims to provide biological and ecological research outputs that can help facilitate communities in the management of the resources upon which they largely depend for food security and income generation.
There are numerous methods that can be used to capture fishes during surveys. Each method needs careful consideration to prevent unrepresentative sampling and biased statistics (Rogers and White, 2007). This study identified two types of angling disciplines best suited for these species including:
ü  Fly-fishing techniques where anglers use artificial flies made from synthetic material to represent natural food.
ü  Artificial lure fishing involves using lures made from balsa wood, iron or hard plastic (Rapalas®, Blue Fox spinners®, Action Lures®) to represent live swimming baitfish.  
After capture suitable fishes were submerged in an aerated tagging container, after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was cleaned in ethanol. Thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity or musculature of fishes using a syringe injector (Figure 1). Thereafter fish were allowed to recover and released back into natural environment.

This study has PIT tagged 49 individual S. altus ranging in sizes from 300 mm to 490 mm total length. These fish were all captured with angling and stress to fish was minimized by limiting holding time to a few seconds (average +-20 sec). Habitats where individuals were captured included (SD <0.3m s 1>0.5m) deep pools and backwaters, (FD >0.3m s-1>0.3m) deep, runs, rapids and riffles.  The dominant substrate within these habitats were sand (60%), clay/mud (10%) and boulders (30%) with cover features column (40%) and overhanging vegetation (60%) being the most important (Figure 2). These habitats are typical for this species which ambushes mostly mormyrids and silver catfish from these vantage points.
(click on image for a better view)
Figure 1: Tagging station was set up in advance (A), after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was      cleaned in ethanol before use, thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity of fishes using a syringe injector (B-D) and unique code was read and recorded (E), measurements taken and a quick profile picture taken before release (F). (Note an unexpected Nembwe was captured during collection and also received a PIT tag photo D and E) 

(click on image for a better view)


Figure 2: Typical habitat of Serranochromis altus in the Kavango River


Table 2: Serranochromis altus, PIT tagged in the Kavango River for the long term behavioural monitoring programme, including number, date, time, tag number and measurements 
(click on image for a better view)

Aquarium and staff initiative

The tanks in the aquarium was upgraded for display purposes. The staff test which is an initiative to get people involved and interested in various fish species was written on the 16 October 2015 at 2 o’clock in the KIFI boardroom (Figure 3). Mr Christian Muyambo received an 80% test score and was the winner of the staff award for his performance.

Figure 3: Staff test being written in the KIFI boardroom
Upgrading the aquarium also resulted in creating the right breeding conditions for a male and female C. rendalli which produced a hatch of fry. These fish were captured during brood stock collection on the 18th September 2015 and could be witnessed constructing a nest two weeks before breeding took place. As the nest developed a distinct colour change took place in both sexes. Three days before the fry could be seen the male and female displayed erratic movements and their colours were noticbly bright. The eggs hatched on the morning of the 08th October 2015 at 26 °C after which continues hatching took place until the evening (Figure 4).  The fry is being measured weekly for growth estimates.
(click on image for a better view)
Figure 4: Coptodon rendalli eggs gently positioned between substrate (A-B), the first hatchlings (C) and both male and female guarding their new born fry in a display tank at KIFI. Fry were born on the morning of the 8 October 2015. 
Figure 5: KIFI staff members receiving training on maintaining and calibrating water quality meters in KIFI boardroom.

Friday, October 9, 2015

Inland Fisheries Research at KIFI: September 2015 monthly progress report.


KIFI Research: September 2015
by
Francois Jacobs

The following documents and research proposals was submitted during September 2015:
  • 1.  Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of Oreochromis andersonii a social economic important freshwater fish species   (9 September)
  • 2.  Standard operating procedure for inland fisheries research Draft 1:10 September
  • 3.   Collecting morphometric and meristic data for Serranochromis altus and Serranochromis angusticeps : 14 September
  • 4.   Inland Fisheries Research schedule for the remainder of 2015 and for 2016: 21 September
  • 5.   The life history strategies of two social economic important freshwater fish species Serranochromis angusticeps and Serranochromis altus in the Okavango River : 23 September
  • 6.   Standard operating procedure for inland fisheries research :Draft 2 , 25 September



Tagging of fish species in the display aquarium was initiated on the 30th of September and forms part of the study titled: Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of Oreochromis andersonii a social economic important freshwater fish species. In brief:

Fishes were conditioned in aquarium facilities and general environmental conditions were kept constant. Individual fishes were collected using a hand held scoop net. Suitable fishes were submerged in an aerated tagging container, after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was cleaned in ethanol before use and hands were sterilised with Betadine (Adcock Ingram Ltd, Bryanston, South Africa). Thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity or musculature of fishes using a syringe injector (Figure 1). Thereafter fish were allowed to recover and released back into aquarium. These fish will be monitored intensively for the next couple of months to assess the affect that PIT tags have on these species. Preliminary results of this experiment will be included with the next progress report.

Figure 1: Tagging station was set up in advance (A), with injectors preloaded with PIT tags (A1-A2), thereafter individual fishes were collected using a hand held scoop net (B) and transported to an aerated tagging container (C), after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident (D). Tagging equipment was cleaned in ethanol before use and hands were sterilised with Betadine, thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity or musculature of fishes using a syringe injector (E) and unique code was read and recorded (F).
Aquarium and staff initiative
The tanks in the aquarium is in the process of being upgraded for display purposes. This facility will host a staff test which is an initiative to get people involved and interested in various fish species (
Figure 2). Brood stock collection has started and data collection is continuously being documented during these surveys as part of a long term monitoring program. 

Figure 2: Aquarium facilities being prepared for a staff test on various fish species as part of training and educating staff. This includes putting substrate into crocodile pond (A-B) and glass aquaria (C-E) as well as treating fish for possible diseases (F-G). Aquarium fish species is collected in addition to brood-stock collection (I-J).

Workshops attended
1.      A stakeholder meeting at Shamvura was held on the 8th of September. A full report (FISHERIES KAVANGO REGION FOCUS GROUP MEETING) on this meeting was submitted and is available on request.  

2.      In addition KIFI hosted an EUS training and planning workshop from 23-24 September 2015. This workshop will result in a EUS surveillance programme that will be carried out during biological surveys and other rearch activities on inland water bodies. It will include an Emmergency Preparedness Plan  to deal with sudden outbreaks of fish diseases. 

EUS training and planning workshop at KIFI






Research Report: Nutrient and productivity field trips report

Nutrient and productivity field trips report
High water 5th – 16th May 2015, low water 16th – 26th August 2015

Participating researchers:
May trip: Geraldine Taylor1,2, Richard Peel1,2,3 (PhD students), Prof. Olaf Weyl1 (Principal Scientist), Dr Jackie Hill4 (Research Officer), Dr Michelle Jackson5 (Post Doctoral Fellow)
August trip: Geraldine Taylor1,2, Richard Peel1,2,3 (PhD students), Ann Wu1 (Intern)
1South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, South Africa
2Department of Ichthyology and Fisheries Science, Rhodes University, South Africa
3NNF/EU Community Conservation Fisheries in KAZA Project, Katima Mulilo, Namibia
4Department of Zoology & Entomology, Rhodes University, South Africa

5Centre for Invasion Biology, Department of Zoology and Entomology, University of Pretoria




Aim
To measure the nutrients and productivity of the Zambezi, Kavango and Kwando rivers and Lake Liambezi during high water and low water periods.

Nutrients
Aim: To characterise the nutrient concentrations of the Zambezi, Kavango and Kwando Rivers and Lake Liambezi.
Objectives: Compare the nutrient concentrations at two sites in each system, at high water and low water periods.
        Characterise the nutrient concentrations spatially, encompassing both main channel and backwater sites in the rivers, and the main lake and river inlets in Lake Liambezi.

Methods
Using an Ion Selective Electrode, ammonium and nitrate ion concentrations were measured in replicates of five, at a number of sights in each system. Water quality parameters such as temperature, conductivity, total dissolved solids, pH and turbidity, GPS coordinates, and water depth were measured at all sites. 

Geraldine and Richard calibrating the Ion Specific Electrode before measuring ammonium and nitrate concentrations at Lake Liambezi.
Preliminary results
Temporal changes
On the Zambezi River in the main channel and a backwater, nitrates were higher in the flood compared to low water, while ammonium was higher in low water.
On the Kavango River, nitrates did not change with season, while in the Kwetche side channel ammonium was higher in the low water.
In the Kwando River and on Lake Liambezi both nitrates and ammonium were higher in August compared to in May.

Spatial changes
In the Zambezi River, main river and side channel sites had higher nutrient concentrations (0.32 mg/l NO3, 0.13 mg/l NH4) than backwater sites (0.1 mg/l NO3, 0.11 mg/l NH4).
In the Kavango River, nutrient concentrations were very low (0.1 mg/l NO3 and NH4) in the upstream section near KIFI in the main channel and in the backwaters. Nutrient levels increased with animal inputs from backwaters draining the floodplain, resulting in higher ammonium levels in both backwater and main channel sites around Kwetche and downstream towards the Botswana border. The most nutrient rich site of the Kwetche backwater measured 0.42 mg/l NH4. Nitrate levels did not change between the KIFI and the Kwetche area.
In the Kwando River upstream of Malyo, nutrient concentrations in the main channel and backwaters were low (0.32 mg/l NO3 and NH4). Concentrations increased downstream of Malyo, and were the highest in Nakatwa channels (0.53 mg/l NO3, 0.3 mg/l NH4). Within Nakatwa, backwaters had lower nutrient concentrations (0.42 mg/l NO3, 0.35 mg/l NH4) than the slowly flowing channels.
On Lake Liambezi higher nitrate concentrations (2.05 – 3.33 mg/l) were measured in the sites closer to land (eg Chobe River mouth, Bukalo Channel and Muyako launch site), compared to those in the main lake (including Linyanti 1.4 – 1.9 mg/l). In addition nitrate concentrations were positively correlated with turbidity. Ammonium concentrations ranged from 0.46 to 0.74 mg/l throughout the lake, with no clear trends observed.

Productivity
Aim: Measure the primary productivity of phytoplankton in all systems during high water and low water periods.

Methods
Filtered water from the site was funnelled into ten clear and ten blackened 2.5 l glass bottles. This constituted five replicates, two clear and two dark bottles per replicate. All bottles were spiked with 2380 µl/l enriched carbon (NaHCO3), and enriched nitrogen (5 light and 5 dark bottles with 435 µl/l KNO3, and 5 light and 5 dark bottles with 230 µl/l NH4Cl) using a 1000 µl pipette. Each replicate (consisting of two pairs of light and dark bottles) was placed within 30 cm of the water surface, anchored on a buoy, and left to incubate for six hours. All five replicated were within 100 m of each other. At the location of each replicate GPS coordinates and water quality parameters were taken, and a HOBO temperature logger was secured to one bottle, which measured water temperature every five minutes. Two HOBO temperature and light loggers were placed at the same water depth, in the vicinity of all of the replicates, to record these variables every five minutes.
Five natural particulate organic matter (POM) samples were taken at each site (one per replicate).
After six hours of incubation, a measured amount of water from each bottle was filtered through glass fiber filters using a filtration manifold and hand held vacuum pump. These enriched POM samples were then dried in a drying oven at 50 °C, and sent to the Stable Isotope Laboratory, Mammal Research Institute (MRI), University of Pretoria for analysis.

Expected results
In total 400 samples have been sent to the laboratory for analysis (50 per system per field trip). Results will quantify the ratio of heavy to light carbon and nitrogen isotopes for the natural and enriched samples. From these values, the productivity of the phytoplankton present in each system can be calculated, in relation to the amount of enriched carbon and nitrogen added to each bottle, and the amount of each isotope taken up (measured by filtering) in the dark and light bottles.

Left: Incubating dark and light bottles (half of one replicate) spiked with enriched carbon and nitrogen (nitrate or ammonium), right: Richard filtering water from a bottle spiked with enriched carbon and nitrogen at Nakatwa on the Kwando River.
Conclusion
This information on nutrient contents and primary productivity is useful for characterising and comparing these systems. An understanding of these properties will also contribute towards explaining differences in fish diets, feeding and growth, and food web structure. Furthermore baseline data on these systems is lacking, and will be useful for future comparisons.

Acknowledgements
Thanks to the EU-NNF Fisheries Project for funding this research. Thanks to Malyo Wilderness Camp for allowing us to stay at your beautiful camp for free in May. Thanks to all of the scientists who participated. Thanks Denis Tweddle for letting us stay with you.