FISHERIES experts and marine scientists say stocks of fish and other aquatic life are dwindling at alarming rates in most of the country's water bodies.

Tanzania is blessed with many water bodies which include the Indian Ocean, Lake Victoria, Lake Rukwa and Lake Tanganyika, where many fish species are said to be already extinct or about to be so. Lake Victoria, with a surface area of 68,800 square kilometres, is Africa's largest lake by area, and the world's second largest freshwater lake (by surface area), after Lake Superior in North America.

Experts say pollution and environmental degradation has led to extinction of a large number of fish species in Lake Victoria over the last four decades. Fish in the lake continue to be plundered at an alarming rate calling for urgent steps to save marine. A recent study revealed that while there were over 400 fish species in Lake Victoria during 1920s, the number dropped to less than 30 at present. They include Nile Perch (sangara), Tilapia (sato) and sardines (dagaa).

The trend is alarming and calls for concerted efforts to safeguard the resources from over fishing and environmental pollution. Residents in the Lake Victoria Basin are in danger as a result of pollution of the lake and people are already consuming contaminated fish.

A few years ago local and international consumers raised concern over the use of dangerous fishing methods. There were reports that some unscrupulous fishermen use poison to catch fish. The poisoned fish were being sold in Mwanza, Dar es Salaam, Songea and Arusha while other fish are exported to the Democratic Republic of Congo (DRC), Rwanda, Burundi and Uganda.

A recent survey by Lake Victoria Environmental Management Programme (LVEMP) revealed, among other things, that the fish breeding grounds have extensively been destroyed by water pollution. Some people use illegal fishing gear, such as gillnets, monofilaments and beach seines.

In the Indian Ocean, experts say fish stocks are also seriously dwindling, especially at spots near the country's coastline, which has a length of 1,424 kilometres. This means that in the near future fishermen must have powerful boats to sail away into deep sea for fishing activities, instead of using simple canoes as is the case at present.

Experts with the Tanzania Fisheries Research Institute (TAFIRI) cite various reasons for dwindling fish stocks in the sea including over fishing, use of illegal fishing gear such as beach siene, gillnets and dynamites as well as climate change. Lake Rukwa is another sad story and some scientists are predicting that the lake would be completely gone within the next 50 years because it is losing its level at an alarming rate due to siltation caused by environmental degradation around it. People are recklessly felling trees and farming in the catchment area.

There are also reports of overgrazing around the Lake Rukwa basin. Environmental witnesses say the lake in the south-western part of the country is but a pale shadow of its former glory. In the 1970s, it was possible to catch up to five 2-feet-long fish using a simple hook within 15 minutes -- that is now a dream.

The government and other relevant authorities must act swiftly to address the situation before things get out of control. It is still possible to reverse the trend because there are many solutions including increasing patrols on the lakes and the Indian Ocean to curb illegal fishing and other malpractices. Government authorities can also declare temporary fishing bans in some parts of the lakes or the Indian Ocean to allow regeneration of threatened stocks.

Chunya District in Mbeya last week banned human activities in and around Lake Rukwa to save the area from further environmental degradation. The district authorities said there was overgrazing around the lake and livestock keepers move hundreds of cattle (into the lake) to drink water. There were also many cases of reckless felling of trees for firewood, charcoal and timber from forests around the lake.

This led to siltation and continued falling levels of the lake. Public education can also be an important tool in fighting illegal activities such as the use of dynamites which destroy breeding grounds and application of destructive nets that kill immature fish. People can also be motivated to venture into aquaculture as an alternative to conventional fishing business. Countries like China and the Philippines have reportedly benefitted heftily through aquaculture.

Aquaculture is the farming of fish and other aquatic life in enclosures, such as ponds, lakes and tanks, or cages in rivers and coastal waters. However, marine biology scientists at TAFIRI say there are also many challenges associated with aquaculture including lack of the right introductory species, capital, equipment, technology and ecological costs.

"In some parts of the world farming of shrimps led to extensive environmental pollution and destruction from wastes discharged from fish farms," said Ms Joyce John, a Dar es Salaam-based marine biology researcher. Some environmentalists warn about the negative impact of fish farms' waste on nutrients at the seabed.

They are also concerned about interbreeding of escaped fish species with wild fish and the use of large quantities of wild fish to feed farmed fish. The conservation organisation WWF generally supports aquaculture as an ever growing source of seafood but insists on setting standards to minimise harm to the environment. But experts say demand for seafood is set to rise as the world population grows and wild fish stocks decline.

The EU, which produces 1.2 million tonnes of seafood and consumes 25 kg per person per year on average, has to import 65 per cent of its needs. Fish farms produced 51.7 million tonnes of fish worldwide in 2006 with an estimated value of $78.8 billion, according to the UN Food and Agriculture Organisation (FAO).