Conservation officials are warning poachers to get their nets out of the Fraser River.

This year's disastrous sockeye salmon runs have prompted the closure of all commercial and recreational fisheries.

But enforcement officials say they've pulled up 50 nets and seized eight vessels in the last week alone.

Twenty-seven people are being investigated, most of them First Nations fishermen, said Herb Redekopp, chief of conservation and protection for the Department of Fisheries and Oceans.

"We're facing a fair number of nets that are fishing at night," he said.

"There's a real pent-up demand for these fish and the market price on the black market is very high."

Officials have stepped up enforcement on the river this week, including night patrols and aerial units.

"We're hitting the river hard," Redekopp said.

"We've doubled our enforcement strength on the Fraser River from Surrey up to Hell's Gate and our primary focus is to move all the sockeye that are in the system right now up to the spawning grounds."

Redekopp said most of the seizures have happened in the Chilliwack and Agassiz area of the Fraser.

The DFO says it's also looking into complaints of illegal fish sales.

Poachers can face a fine of up to $100,000 or up to two years in jail if found guilty.

The following is a sample of salmon prices found in local seafood shops complied by CBC News:

7 Seas Fish - Kitsilano

Fillet price per poundSource
Sockeye$19.95Alaska
Coho$19.95Prince Rupert, Washington State
Spring$24.95

Vancouver Island, Washington State

Crab Shop - North Vancouver

Fillet price per poundSource
Coho$16.95Haida Gwaii

Spring

$18.95Haida Gwaii

The Salmon Shop - Granville IslandFillet price per poundSource
Sockeye$20.99Local suppliers
Coho$19.99Local suppliers
With files from the CBC's Dan Burritt and Sadiya Ansari