Many of the shallow lakes in the lower Waikato River floodplain have significantly degraded water quality as a result of nutrient and sediment enrichment from non-point sources. Pest fish species such as koi carp, goldfish, and catfish have exacerbated lake decline by resuspending lake sediments and uprooting submerged macrophytes. This this resulted in a collapse of submerged macrophytes and progression from clear-water oligotrophic state to a eutrophic (algal-dominated) state.