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Namibia launches freshwater fish tagging program: the Ministry of Fisheries and Marine Resources (MFMR) of Namibia, in collaboration with the Norwegian Institute for Nature Research (NINA), has launched one of the largest freshwater fish tagging programs in southern Africa.

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Namibia is generally considered a country characterised by endless deserts and cold seas with very limited freshwater fish resources. Despite this reputation, the northern perennial rivers, including the Zambezi and Kavango Rivers, are arguably the premier freshwater fishing destinations in Africa. With more than 4 000 anglers visiting lodges on the Zambezi River in Namibia during 2010, an estimated 38 000 tigerfish and 14 000 cichlids were captured. Although most of these fish are caught by sport fishermen that practice catch and release, their economic significance plays a major role in the uplifting of communities in these rural areas (e.g. jobs at lodges). For centuries, these river systems have been used for subsistence fishing with minimal fish being sold/bartered at informal markets. Today, these areas are facing unprecedented population growth, with inland fisheries becoming a major trade industry.

In fact, the inland fishery industry in Namibia had grown from a total worth of N$ 9 million per annum in 1996 to N$ 75100 million today. As a result, freshwater fish have become a highly valuable commodity and commercial and illegal fishing practices have replaced subsistence and recreational activities. As more people become involved in this lucrative business, the total annual yield has increased rapidly (estimated 5 000 metric tons of fish per year), but catch per unit effort of commercial, subsistence and recreational anglers has decreased significantly.

The responsibility to ensure conservation, restoration, protection and sustainable utilisation of all inland fisheries resources within Namibia falls within the strategic objectives of the Ministry of Fisheries and Marine Resources. To achieve these objectives, an understanding of the biology and ecology of various fish populations is of paramount importance. The MFMR is committed to a number of freshwater fish research projects. One of these projects includes a tagging program in the Kavango River around the Popa Falls/Mahangu area (Divundu).

The Tagging Program

One of the focus species is the African tigerfish (Hydrocynus vittatus), which is a charismatic species that is endemic to African rivers. They are also considered one of the most important subsistence, commercial and recreational fish species in Africa. Furthermore, their functional role as top predators in the transfer of energy between eutrophic floodplains and the main river is crucial in maintaining ecosystem functionality. Despite their importance and popularity among anglers, very limited information exists on their behaviour, migration routes and habitat use within the Kavango River.

One of the most efficient ways to monitor freshwater fish in their natural environments is by tagging or marking them.

Long Term Mark and Recapture Study

The capture-recapture methods that uses external physical tagging is one of the most common models for fishery scientists to determine the movement, growth, mortality, survival and recapture probability of fish species. Although this method rarely yields large catch returns, it can provide valuable long distance migration data. In total, an estimated 6 500 fish will receive plastic-tipped dart tags. This article aims to make the public aware of the process that should be followed when a tagged individual is captured. The MFMR would like to make a general request to the public to release all tagged fish back into the river, after information is recorded. All the information that is required and the number where it should be submitted (via SMS), is printed on the easily identifiable plastic dart tag.

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Step 1

If a dart tag is visible on the fish, please record the following information:

The four digit tag number, e.g. 0001 The date

The place of capture, if possible GPS coordinates If possible, fork length Step 2

Please SMS this data to (+264) 812868168.

If a fish is not returned to the river, please remove the plastic tag, record the necessary data and return to: Kamutjonga Inland Fisheries Institute (KIFI), P.O. Box 5147, Divundu, Namibia

Radio Telemetry Study

This is one of the most expensive, but most effective, methods for fisheries scientists to retrieve high-resolution information of freshwater fish species. It is a method that has been used in freshwater ecosystems as early as the 1950s, and is currently the preferred method for behavioural ecology studies. Although a topic of large controversy, it is accepted that the intensive tagging procedure has negligible effects on the normal physiology or behaviour of experimental fish. In total, 60 fish will receive externally attached radio transmitters (+/- 20g) that will be monitored for the duration of the tag's battery life (365 days).

Only after two weeks from the date of capture and tagging, fish are monitored to avoid any effects that may be associated with handling of the fish. Radio tags on fish are then monitored manually by boat, on foot and from the air using light aircraft. In the event that a fish is located, a range of environmental and behavioural parameters are recorded.

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Radio telemetry is an expensive method and the MFMR requests that all tagged fish are returned to the river. In the event that a fish dies, please return the radio tag to the address provided above.

Despite the known value of tagging/marking techniques, to date only a few dedicated freshwater fish behavioural ecology studies have been carried out in southern Africa. Currently, this is one of the largest tagging efforts in southern Africa and will provide valuable ecological information. This research will also greatly facilitate decisions on fishing regulation policies and the establishment of fish protected areas (FPAs) in Namibia.

The MFMR would like to acknowledge the support of the Norwegian Institute for Nature Research (NINA), University of KwaZulu-Natal, South African Institute for Aquatic Biodiversity (SAIAB) and the National Commission on Research Science and Technology (NCRST) of Namibia.
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Title Annotation:Fish Science
Author:Jacobs, Francois
Publication:African Fisherman
Geographic Code:60AFR
Date:Aug 1, 2016
Words:944
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