Traffic jams on the snarled up roads of Nigeria's megacity of Lagos are legendary, but a growing problem is also clogging up the waterways of Africa's biggest city — water hyacinths.

The spread of the invasive species of fast-growing plant is not only damaging transport links in Nigeria's economic capital, built on a lagoon dotted with islands.

With waterways covered and silting up, the aquatic weed is also threatening fishing jobs and a vital food source.

"This is all I can get since morning," said fisherman Solomon Omoyajowo, showing a handful of fish in a bowl in his wooden canoe.

"Many fishermen have abandoned their boats, while some of us who still want to continue, now try our luck here," he told AFP, using his palms to wipe a stream of sweat from his face. 

When he hauled it up, he had caught only four small fish.

An abandoned boat is seen on coastlines in Lagos. Pius Utomi Ekpei/AFP

"I don't think I can do any other job apart from fishing," Adisa said. "I will continue to manage until the government comes to our aid to clear the weeds."

Jobs at risk

Originally from South America, the plant has caused chaos across several countries in Africa. Earlier this year, a thick green carpet of the weed choked up Kenya's main entry to Lake Victoria, the largest body of water in Africa.

It was first noted in Nigeria in the early 1980s, in the Badagry creeks west of Lagos, reportedly spreading from neighbouring Benin.

Since then, mats of weeds have spread to rivers across the country, including Nigeria's oil-rich Niger delta.

It is having a damaging impact.

One study, from Nigeria's Obafemi Awolowo University, estimated it put at risk one-third of Nigeria's local fish supply, a cheap source of food millions rely on.

The Ogun River overtaken by water hyacinths, an invasive aquatic plant, in southwest Nigeria. Pius Utomi Ekpei/AFP

"It has become a menace to the marine ecosystems of Lagos," said Nkechi Ajayi, spokeswoman from Lagos State Waterways Authority, adding that it impacted "the socio-economic activities" of river communities.

Propeller problems

Water transportation is also at risk. Operators complain of damaged boats and risk of accidents.

"We often find it difficult to navigate whenever the weeds clog the river," said boat driver John Ibikunle, as he waited to pick passengers on Lagos Island.

He said many commuters, who once preferred water transport to beat the perennial Lagos traffic gridlock, are returning to the roads, tired of being stuck on water with weeds snagging the propeller.

Boatmen tries to navigate through water hyacinths, an invasive aquatic plant. Pius Utomi Ekpei/AFP

The plant doesn't grow well in salt water, and environmental experts say the plant expands during the rainy season when the level of fresh water rises in Lagos lagoon.

"It is a seasonal plant," said Noah Shemede, an environmental activist, from the vast area of wooden homes on stilts built into the water, a fishing settlement called Makoko. 

Underwater lawn mower 

But while fishermen and boat operators struggle with the weed, one local entrepreneur sees a business opportunity.

"The weeds are harvested from water channels and spread out in the sun to dry," Idachaba said. "They are processed into small ropes, required to weave the products together."

Some see a brighter future.

Scientists at the University of Lagos say the plant could also be converted into energy as biomass production, to help solve part of Nigeria's chronic electricity shortages.

Agence France-Presse