Warmwater Fisheries Issues
The EPA conducts standard aquatic surveys by site and state periodically and reports findings to Congress under provisions of the Clean Water Act. The 2017 National Water Quality Inventory reports that 46% of river and stream miles are in poor biological condition, 21% of lakes are hypereutrophic and water quality of 32% of the Nation’s wetlands is degraded. Contributing factors include nitrogen and phosphorus from fertilizer runoff; salinity; acidification; riparian disturbance; excess levels of streambed sediments; and effluents containing enterococci (bacteria).
Warmwater habitats are also experiencing adverse changes caused by invasion of non-native species. Eurasian watermilfoil and elodea are unsuitable as shelter, food or habitat for native fish and aquatic insects and form dense vegetative mats that outcompete native plants. Several species of invasive carp reduce vegetation abundance and diversity, stir up sediment, complete with native fish and invertebrates for food sources and increase phosphorus levels in water. Invasive, non-native fishes compete directly with native fish for food and consume their young. Invasive invertebrates (e.g.: New Zealand mud snails, zebra mussels, rusty crayfish) compete with native macroinvertebrates for habitat and food sources.