What other problems affect salmon stocks?
There are a number of factors which have had an adverse effect on salmon stocks, as shown in detail on the following pages. Some, such as predation by other species, have already been mentioned. Others include:
- Pollution of rivers and silting up of spawning gravels
- Obstacles to migration, such as dams
- The effect of fisheries which inadvertently take salmon (“by-catch”) or which remove the salmon’s natural food in the sea.
- Climatic changes which are affecting the salmon’s ability to grow and survive during its time in the sea.
- High seas and coastal “interceptory” mixed stock fisheries which take fish from more than one river population, thus denying the ability to manage the exploitation of individual river stocks on a local basis to maintain stock levels.