What are the main causes of the wider declines in sea trout stocks?

It is wrong to believe that sea trout stocks should remain stable. Clearly, this is not the case in natural ecosystems. Also, there are some doubts about how accurately we can assess the level of stocks. The main indicator of sea trout stock abundance remains reported catches and, while these provide a broad picture of stock abundance, they are affected by levels of reporting accuracy, weather conditions, fishing effort and new regulations etc. More importantly, the stocks upon which the catches are based are vulnerable to a wide range of habitat impacts, notably from droughts and spates, water abstraction and pollution, hydro power schemes, land drainage, nutrient enrichment and siltation and other effects of intensive farming and forestry, urbanisation, road improvements and even aggressive flood defence schemes, together with other creeping anthropogenic development of large parts of river catchments.  Increases in predation pressure on sea trout stocks by growing numbers of fish-eating birds and seals, both at sea and in our rivers, also may be an important factor.  Superimposed on all of these concerns are potentially serious effects of climate change, of increases in ambient air and water temperatures, frequency and severity of drought events and localised flash-flooding, rising sea temperature, levels and current patterns and inter-related effects on marine ecology, including changes in fish species composition and abundance.