How does hypoxia impact fish populations?

Hypoxia, which refers to low levels of dissolved oxygen in the water, significantly impacts fish populations primarily by decreasing their growth rates and potentially increasing mortality rates. Fish require a certain level of oxygen to survive and thrive; when oxygen levels are insufficient, their metabolic processes are hindered.

Under hypoxic conditions, fish may have to exert more energy to swim and find cleaner, more oxygenated water, which can lead to increased stress and decreased feeding efficiency. This generally results in stunted growth because the energy required for growth is redirected towards basic survival.

Furthermore, prolonged exposure to hypoxic conditions can lead to higher mortality rates as fish become more susceptible to diseases and other stressors. When populations are stressed from low oxygen levels, their overall health diminishes, making it harder for them to reproduce successfully or to cope with environmental challenges. Hence, the correct understanding of how hypoxia impacts fish populations aligns with the option that highlights decreased growth and increased mortality.