At sea, they can travel thousands of miles, navigating vast and challenging waters, before returning to the river of their birth to spawn. This incredible journey, combining strength, endurance, and precise navigation, has long captured the imagination of anglers, naturalists, and river communities alike.
Once abundant across England’s rivers, Atlantic salmon populations have been in serious decline for decades. These fish rely on habitats such as chalk streams - clear, mineral-rich rivers with stable, cool water - for successful spawning. The South of England is home to around 85% of the world’s chalk streams, yet many of these rivers, including Hampshire’s River Itchen, face increasing environmental pressures.
Numbers tell a stark story: in 2022, just 133 salmon returned to the Itchen to spawn - the lowest count in over thirty years. By 2024, only 187 returned, representing just 37% of the Conservation Limit, the minimum number of eggs needed to sustain the population. These declines are mirrored across other chalk streams in southern England, reflecting a long-term trend that has pushed Atlantic salmon to the brink.
A winter journey
During the winter months, adult salmon make their dramatic return from the sea, navigating back to the rivers where they were born. This period, known as the spawning season, is one of the most critical in their life cycle. As the water cools, salmon move upstream, battling currents and obstacles, seeking the clean gravel beds where they will lay their eggs. Their journey is not only a test of endurance but also of precision: salmon must locate suitable spawning grounds where eggs can survive and develop.
Salmon enter rivers in stages, with some arriving earlier to establish prime spawning locations and others following in successive waves. They rely on fast-flowing, well-oxygenated water and crucially intact gravel beds, which allow eggs to be safely deposited and nourished. Female salmon dig depressions called redds in the gravel where eggs are fertilised and protected from predators. These spawning grounds are the lifeblood of the population: if disturbed or environmental conditions decline, the eggs and subsequent juvenile salmon are at serious risk.
Vulnerable at every turn
During this period, salmon are particularly vulnerable. They rely on clean, well-oxygenated water, stable flows, and intact gravel beds to successfully spawn. Any disruption to these conditions – whether from human activity, pollution, sedimentation, low water levels, or habitat degradation – can reduce survival rates. Many other species also share these habitat requirements, making the river ecosystem as a whole sensitive to environmental pressures.
Wild swimming, dogs entering the water, or other disturbances can damage the gravel where eggs are laid, while poor water quality, over-abstraction, or altered flows can impact egg development and the survival of young salmon. Even seemingly minor pressures can have significant consequences during this critical stage of their life cycle.
Restoring habitat
Hampshire & Isle of Wight Wildlife Trust is actively working to protect Atlantic salmon and the wider river ecosystem through a variety of habitat management measures. Practical restoration work focuses on improving the physical structure of rivers and their surrounding land to create conditions conducive to spawning and juvenile growth.
On reserves such as Winnall Moors, management balances the needs of both aquatic and terrestrial habitats. Here, the Trust carefully manages water channels, maintaining open, clean gravels while leaving woody debris and naturally fallen trees in strategic locations to create flow diversity and shelter for salmon. Light, low-impact interventions, such as selective vegetation management and marginal grazing, help maintain a varied habitat that supports not only salmon but other aquatic and riparian species.
Hockley Meadows Nature Reserve offers another example of targeted habitat improvement. On this small off-channel section of the Itchen, the Trust has introduced fallen and bleached trees, woody debris, and berms to enhance flow patterns and create high-quality spawning areas. Canopy management allows in-channel vegetation to flourish, further enriching the habitat for salmon and other river life. Early observations suggest that these interventions have been successful, with salmon observed using the area in recent seasons despite naturally low water levels.
Across the Itchen, the Trust also monitors and maintains key features, such as gravel beds, riffles, and woody debris, which are essential for spawning and juvenile development. Managing rivers in this way is delicate work: interventions must consider seasonal water levels, flow patterns, and the broader ecological balance, ensuring that actions benefit salmon without disrupting other wildlife or increasing erosion.
