Salmon are an already endangered species

Fish numbers are already low in rivers in the north-east of England, due to soaring summer temperatures, which lowered water levels and starved rivers of oxygen.

The agency in the region says it has received almost 100 reports of poaching so far this year, especially on the river Tyne.

Agency officers recently carried out an all-night operation on the river, in which several poachers were arrested and fish worth thousands of pounds confiscated.

An agency spokesman said: "Despite the misconception that poachers are lovable rogues who just take the odd fish, often they are organised gangs with serious criminal records looking to make big money.

"They often work in organised groups and have an outlet for the fish, selling it directly to hotels and restaurants or down South at fish markets.

Poached salmon often end up sold on a black market

"We have had people in the past, who have earned in a very short time, in excess of �7,000 from poaching salmon here."

Wild salmon are currently heading up-stream laden with eggs to spawn and reproduce in the autumn.

But the agency says when a female fish is poached, up to 9,000 others are lost that would otherwise hatch.

Wild salmon and brown trout can command a higher price than cheaper farmed fish.

The penalty for poaching can vary from a �5,000 to a two year jail sentence.

The Environment Agency spokesman added: "It is a shocking state of affairs, we will continue to carry out surveillance exercise and catch those responsible."