Salmon facing difficulty reaching sea from River Itchen

Known as smolts, these juvenile salmon need to travel downstream each spring, but structures along the lower river in Southampton are impeding their journey and putting the population at risk.

The Environment Agency has launched a study to explore how to improve the river system and support the salmon’s migration.

Jackie Mellan, the Environment Agency’s project manager for the study, said: "The River Itchen has really changed in the past 10 years – the flow of the river is diverting, salmon are at significant risk of extinction, sea level has risen, and climate change makes floods and low flows more extreme and frequent.

Smolt are struggling to get past water control barriers on the River Itchen like Woodmill Sluice (Image: Supplied) "The first step is finding out what can be done to improve the river system and increase its ecological resilience.

"For salmon, that means improving migration to the sea and boosting their odds of returning to spawn."

Historic modifications to the river near the estuary, including water level controls and legacy infrastructure, have created sharp changes in water velocity.

These changes cause smolts to bunch up, making them more vulnerable to predators and poachers and delaying their journey to the sea.

Upstream, further complications have arisen in Riverside Park, where the manmade channel sits higher than the natural floodplain.

A breach has allowed water to divert away from the main river, which could eventually impact the ecology downstream.

The Environment Agency’s study focuses on the lower River Itchen from Woodmill to Mansbridge and will consider habitat restoration, fish passage improvements, and community involvement.

The River Itchen is a designated Site of Special Scientific Interest and a Special Area of Conservation.

It is one of only six chalk streams in England that supports Atlantic salmon, a species now at high risk of extinction.

In response to declining salmon numbers, the Itchen Salmon Delivery Plan has been launched to coordinate conservation efforts across organisations.

Councillor John Savage, cabinet member for green city and net zero at Southampton City Council, said: "We are delighted to work closely with community groups whose vital efforts help preserve, protect, and promote the River Itchen."