Thursday, August 8, 2013

Mahangu Game Reserve Fish Disease (EUS) Survey: 2-4 August 2013


Some of the boats and anglers from Crokango Angling Club that assisted the Ministry of Fisheries and Marine resources at KIFI with the EUS survey in Mahangu Game reserve

Recreational angling events and angling competitions are valuable platforms for fisheries research in Namibia. MFMR fisheries research uses gillnets which catch a very small number of the large fish that leads to under representation of large fish. Recreational (sport fishermen) anglers can catch large numbers of large fish (with sport fishing techniques) which iron out the under representation of large fish during surveys. Angling events and angling competitions also provide an opportunity to monitor fish diseases such as Epizootic Ulcerative Syndrome (EUS) among large fish.

Kamutjonga Inland Fisheries Institute (KIFI). Next to Mahango Game Park. Yellow line on the bottom is Botswana border
Fish with ulcers and lesions had been noticed in fish caught either by the public or during sampling activities conducted by MFMR staff. These fish are suspected to be infected with a fish disease called Epizootic Ulcerative Syndrome (EUS). The occurrence of the fish disease was first reported in Namibia in Caprivi region in November 2006. In September 2008, EUS spread further to the Kavango region and was confirmed on fish farms of Kavango region
 This report consists of data collected from 02 – 04 August 2013 in the Mahango Game Park. The Ministry of Fisheries and Marine Resources at KIFI (Kamutjonga Inland Fisheries Institute) invited 8 professional anglers from the Crokango Angling Club to assist in the collection of suspected fish with lessions that might be EUS.

Table 1: Suspected EUS fish by MFMR and Crokango anglers at Mahango game park

Total fish per species
Suspected EUS Fish in numbers
Clarias gariepinus

Hydrocynus vittatus
Oreochromis andersonni
Sargochromis giardi
Serranchromis altus
Serranchromis robustus
Serranochromis angusticeps
Serranochromis thumbergi
Serranochromis macrocephalus

 The table above illustrates the number of different fish species caught during the period 02 – 04 August 2013. The most abundant species being Serranchromis altus with 88 landed and 8 suspected fish sampled. Oreochromis andersonni was the least abundant with 1 being caught with suspected EUS lesions. 
Mr. Alex Muhero (KIFI) with  a Threespot tilapia (Oreochromis andersonni). One of the fish with lessions taken for sampling 
All suspected EUS fish had an average total length of about 350mm. The weights of most fish ranged from 1.5 to 3 kg.  Suspected EUS Samples will be taken for laboratory testing, therefore, results are still pending. 

Data Information found in this report reveals the possibility that fish of the Kavango River are still prone to have  EUS. Thus, more research is needed to monitor the situation on a continious bases to monitor the  spread on EUS.

Angling facts:

Water condition: 
17 degrees celuis, mercy to clear water. Most fish caught next to reed banks and in backwaters and lagoons (shallow at about 1-1.5m) behind sand banks.
One of the Backwaters of Okavango in Mahangu Game Park
Tackle used: 

Mostly small plastics with 1/4 ounce jig heads and smaller. Also small efzet spinners and small rapala, halco and other brand lures. Largemouths  were biting on the bottom. Most success was achieved when small plastics were pulled along the bottom next to reed banks or in backwaters and lagoons behind sand banks.

Largemouth (Serranchromis altus) with plastic (drop shot) still in his mouth

Largemouth (Serranchromis altus) with plastic (drop shot 1/4 ounce jig) still in his mouth
Dawid Burger with a Nembwe (Serranchromis robustus) caught in backwater with dropshot (1/4 ounce jig)
Dawid with a Tiger Fish (Hydrocynus vittatus) caught on 1/2 ounce jig (dropshot) and plastic minnow (paddle tail)
Jig head still in tigers mouth. Minnow gone...with such teeth
Alex Muhero with a Largemouth (Serranchromis altus) caught next to reed bank

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