Inland Fisheries Research Namibia for December 2015
Francois Jacobs (Senior Fisheries Biologist: KIFI)
Early development and growth of Coptodon rendalii
Fertilized eggs of Coptodon rendalii were obtained on 10 December 2015 from tank A in the aquarium at KIFI. Eggs were syphoned from the constructed nest with surgical tubing and carefully transferred into a holding container set up in the laboratory. Water temperature was continually monitored and kept stable in a controlled environment.
Eggs were removed from holding container and placed on glass slides for observation under a 10 x light microscope. Eggs were continuously monitored every 2 hours until larvae started hatching. Thereafter observation of early development were made every four hours.
The Unam 2nd year attachment students is in the process of describing each embryo, larvae, and juvenile stage as part of a research project. This data will be used to compare various aquaculture species to find the species that is best suited for our environmental characteristics. In addition to early development and growth parameters, the possibility of gene selection and modification of brood stock can be explored. This will create stronger, faster growing offspring that can contribute to the efficiency of aquaculture in Namibia.
Kunene biological survey
The Kunene River originates near Boas Aguas near Huambo (Nova Lisboa) in the highlands of Angola. Considered the second largest river in Angola, it winds southwards for 650 km, plunges over the Ruacana Falls and then heads westwards, forming the boundary between Namibia and Angola. It empties into the Atlantic Ocean 1 050 km from its headwaters.
The Kunene biological survey is conducted annually (low flow). Data collected during this 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.
Surveys by the MFMR in this area is now almost in its 20th year. The number of fish species in the Kunene has been continuously challenged, but, it is generally accepted that there are about 70 species of fish within this system.
The following stations were sampled during this survey:
1. Olushandja Dam that receive water directly from Kunene River via Calueque Outapi canal,
2. Hippo pool immediately downstream of Ruacana falls,
3. Swartbois’ Drift between Ruacana and Epupa falls,
4. Epupa just upstream of the falls,
5. and Otjinungua further downstream of Epupa falls
Data collected during this survey is currently in the process of being analyzed. A few photos from the survey. The survey team at Epupa Falls.
An interseting find during the survey: Serranochromis angusticeps “Thinface largemouth” (A) and Serranochromis altus “Humpback largemouth” (B) has recently been described as a single species in the Kavango River. There is much confusion between these two species and mormphological charatirisation is being carried out. According to Skelton (2001) A Complete Guide to the Freshwater Fishes of Southern Africa, Serranochromis altus has not been recorded in the Kunene system. This specimen (B) is however very similar to S. altus found in the Kavango river.
Tagging of wild populations of Serranochromis spp.
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. Gill nets are ideal for targeting mobile individuals, in deep habitats, whereas electro-fishing (electro-narcosis) and fishing is best suited to collect species that are relatively immobile or rarely caught by other methods.
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 (O’Brien et al. 2013a). Tagging equipment was cleaned in ethanol before use and hands will be sterilized.
Plastic tipped dart tags
These types of tags vary in shape and colour. They are individually coded and have the major advantage of being easily detected by anyone. These tags are inserted next to the dorsal fin into the musculature of an individual by means of a dart tag applicator. The tag should dangle freely at the end of the anchor attachment to avoid abrasion.
Passive integrated transponders (PIT) tags
PIT tags are small (10.3 mm x 2.1mm in diameter) coil and integrated circuit, programmed to transmit one of some billion codes. PIT tags are interrogated with the field induction coil which energizes the tag to transmit its code. This inevitably extends the life of a PIT tag as they have no constant energy source. They are used internally with minimum handling of fish required. This technique uses syringe injectors or a small surgical technique to implant the PIT into the peritoneal cavity or musculature of a fish.
1. There was no workshops attended this month
2. Training was in situ during Kunene biological survey on water quality, various sampling methods and fish identification procedures
3. UNAM students receive training on fisheries related work on a daily basis
4. Training was given on various tagging techniques, DNA collection, embryogenic development, morphological and meristic measurements, fingerling production and management