Why are native fish more plentiful on the eastern side?

Native fish are often more plentiful on the eastern side of a region due to factors such as favorable water conditions, habitat availability, and less human disturbance. The eastern side may have more natural rivers, lakes, and wetlands that provide ideal breeding and feeding grounds. Additionally, conservation efforts and regulations may be more effective in these areas, allowing native populations to thrive. Environmental conditions like temperature and nutrient availability also tend to support a diverse range of native species.