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. 

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