Frederick Sinjela, a fisherman in Mpulungu district in Northern Province, Zambia, cannot imagine how his actions could affect something as big as Lake Tanganyika, but his harmful practices, multiplied by thousands like him, are a real and growing threat.
"At least we know that fish will never finish - [there are] thousands and thousands - it is just that now [they] have gone deeper." Nevertheless, the extended boat trip was still worth it: "I make about 20,000 kwacha [US$6] per day," giving him a better-than-average income.
"We mount many lamps on our boats at night so that the fish think it is day-time and come out, and we catch [them]." This is the main fishing method on the lake. "But finishing? It will never finish," he said confidently.
There was really no reason to think fish would run out: Lake Tanganyika is huge and has always provided food and an income to the millions of people living along its shores; up to 40 percent of the protein in their diet comes from fish.
It is the world's longest (670km) and second-deepest (over 1,400m) freshwater lake; at over nine million years old it is also home to some of the oldest fishing settlements on the planet.
Its importance to the region cannot be overestimated: a rapidly growing population of some 10 million people in four different countries - Tanzania, Democratic Republic of Congo, Burundi and Zambia - share the lake's watershed and depend upon it for fresh water, food, transportation and income.
|Now we have to go very far away to catch fish. In the past, we would catch a lot just 10 metres from the shore|
Yet some of Sinjela's colleagues, like Justin Mambwe, were worried: "Now we have to go very far away to catch fish. In the past, we would catch a lot just 10 metres from the shore. There is a difference between now and the way fish used to be." The catches were also smaller.
Wilfred Sikanyika, a local environmental campaigner who used to work for Zambia's Ministry of Agriculture, told IRIN: "We are deeply concerned at these indiscriminate fishing activities on the Zambian side of Lake Tanganyika."
Fish stocks have been declining over the years and there are very few fish on the Zambian side. "Our people are now going as far as Tanzania and DRC [Democratic Republic of Congo]," he said.
"People are using mosquito nets and everything they can [to catch fish] - these mosquito nets take in everything," he told IRIN.
Using mosquito nets, which have an extremely fine mesh, means the fish are caught before they can reach maturity and spawn, a major reason for declining fish stocks. Moreover, the nets, which are mainly distributed in government malaria eradication campaigns, are not being used for their intended purpose.
The concerns go far beyond long-term food security, health and livelihoods: this destructive practice is putting the lake's renowned biological diversity at risk.
According to the International Union for Conservation of Nature, a global environmental network, no place on earth holds such a variety of life. Lake Tanganyika harbours over 2,000 different species, of which more than half are found nowhere else. The fishermen target only six species, but the mosquito nets are indiscriminate.
The lake is under threat: overfishing caused by population growth along the shore is depleting its stocks and shrinking their diversity; industrial and agricultural pollution, like fertilizers and pesticides, are degrading water quality; deforestation is contributing excessive amounts of sedimentation, changing the aquatic environment.
"We are currently working on forming an association that will look at protecting the biodiversity of Lake Tanganyika and promoting sustainable fishing methods," Sikanyika said.
The future of fishing
Justina Zimba, a research officer at the fisheries department in Mpulungu, said exact figures on fish stocks were hard to come by, making it difficult to assess the extent of the decline.
"Data collected since 1980 shows that the catch and catch-per-unit effort of certain species like kapenta [also known as the Tanganyika sardine] has drastically declined, especially in the heavily exploited [Zambian] southeastern arm of the lake," she noted.
Photo: Nebert Mulenga/IRIN
|Protein rich Kapenta fish for sale on the shores of Lake Tanganyika|
"There are no resources at the moment for us to do the monitoring, or even carry out the latest fish-census exercise. We are currently depending on data from the fishing companies and going by their figures."
The problem transcends national boundaries. "Addressing these threats effectively requires the cooperation of the four countries [sharing the lake] and appropriate regulations for the lake, because at the moment the lake is regarded as a 'no man's land' and people fish everywhere."
However, the Lake Tanganyika Sustainable Management Project, a cooperative effort by Tanzania, Burundi, DRC and Zambia, has been set up under a common Lake Tanganyika Authority.
"We realised that the dwindling of fish stocks ... was a matter of serious concern among all the ... [lakeshore] countries. We do not even know whether all the 350 endemic fish species can be easily found in the lake today," said Kenneth Nkowani, Director of Zambia's Department of Environment and Natural Resources.
The Zambian component of the project will stem overfishing and control sediment flows from the steep mountainous terrain. According to Nkowani, "We want to see change in the way people manage the lake within a year or two."