England and Wales, UK: A sign of the modern times when pollution and other human-made pressures on nature generally and wildlife are at a peak and worsening despite an increased awareness of the problems. The succinct infographic provides the essential, disturbing information for those concerned about the natural world and its continued destruction by human activity in it wide range of forms.
There are 49 rivers in England and 31 in Wales that support salmon. The England Environment Agency found that 84 percent of those rivers in England were now ranked at risk for salmon. This is the highest proportion since records began according to The Times report.
The salmon is at risk of becoming extinct on many rivers where they were once abundant.
River pollution impact on salmon
River pollution can have a devastating impact on salmon habitat, making it unsuitable for their survival. Here are the key ways pollution harms salmon:
1. Water Quality Deterioration
- Toxic Chemicals: Industrial runoff, agricultural pesticides, and heavy metals can poison the water. These toxins harm salmon directly by damaging their organs, reducing their immune function, and leading to death.
- Oxygen Depletion: Excessive nutrients from fertilizers (nitrogen and phosphorus) cause eutrophication, where algal blooms thrive. As these algae die and decompose, they consume oxygen, leading to hypoxia (low oxygen levels). Salmon, like most fish, rely on high oxygen levels and cannot survive in hypoxic waters.
2. Temperature Increase
- Pollutants such as warm wastewater from industrial plants raise the water temperature. Salmon are cold-water species, thriving in temperatures between 50-60°F (10-15°C). Warmer water increases their metabolic rate, which in turn increases their oxygen demand. Since warmer water holds less oxygen, this creates a double burden, stressing or killing the fish.
3. Habitat Alteration
- Sedimentation: Construction and logging activities can increase sediment in rivers. Sediment clouds the water, making it hard for salmon to find food and obscuring gravel beds where they spawn. It also smothers salmon eggs laid in gravel nests, preventing them from receiving oxygen and leading to death before hatching.
- Habitat Fragmentation: Polluted or altered rivers may become fragmented due to the construction of barriers like dams. These prevent salmon from accessing their natural spawning grounds.
4. Contaminated Food Supply
- Pollution can affect aquatic insects and other small organisms that form the food base for salmon. If these organisms absorb toxins, salmon that eat them accumulate harmful substances, leading to bioaccumulation and poisoning. Contaminated food sources can lead to developmental issues or impaired reproduction in salmon.
5. Impaired Reproduction
- Certain pollutants like endocrine-disrupting chemicals (from pharmaceuticals, plastics, or pesticides) interfere with hormone function. In salmon, this can disrupt their growth, development, and reproduction. For example, it can cause abnormal sexual development or reduce their ability to spawn effectively.
6. Impaired Migration
- Salmon rely on clean, cool waters to navigate their way to and from the ocean during their life cycle. Pollution in rivers can affect the salmon’s sense of smell, which they use to identify their natal streams for spawning. If they cannot find these streams due to pollutants, they may fail to reproduce.
In essence, river pollution disrupts every aspect of salmon life—from egg survival and growth to migration and reproduction—making polluted rivers highly unsuitable for their survival.
