CARP CAUSE THE TURBIDITY OF THE WATER TO BE HIGH (CARP MAKE THE WATER MUDDY).
The answer to this question is that it depends on what the physical characteristics of the water are. In smaller ponds with a silt substrate, Common Carp can cause a noticeable impact on turbidity if high enough concentrations of fish are reached (Barton and Kelton 2000). However, Fletcher et al. (1985) found “no association between high carp densities and high turbidity” in several larger water bodies and concluded that hydrologic changes were to blame and water level fluctuation reduced the amount of water plants, further exacerbating the issue. This would be applicable to many of the larger reservoirs and rivers in the USA.

Looking at everything as a whole, Common Carp can cause a increase in turbidity in some systems if that system has a substrate that is conducive to be suspended in the water column. The existence of Common Carp is not the only factor of making the water muddy, and wind and sediment type (Lougheed et al. 1998), as well as boat traffic (Anthony and Downing 2003) are all significant factors that often produce huge effects on water clarity regardless if Common Carp are in the water or not. The effects of boat wakes in particular are striking, with up to a 50% increase in turbidity over up to 56% of the lake (Anthony and Downing 2003). In general, hard substrates such as gravel produce significantly less turbidity than clay or silt (Crivelli, 1983).

Another consideration is eutrophication. Eutrophication is an excess in nutrients, especially Nitrogen (N) and Phosphorus (P), in a body of water that ultimately leads to a surge in algal growth. These algal blooms can cause incredibly destructive effects such as increased turbidity and asphyxiation through oxygen crashes. Eutrophication can occur through a variety of sources; human activity is the main source. Run-off water from agricultural land (or lawns) containing fertilizers that are rich in nutrients are a large cause, as well as large urban areas, sewage and industrial discharges (Ansari & Gill, 2013).

Carp are like any species of fish. There are positives and negatives to every species. With the popularity of carp fishing increasing, statements like the one above will continue to decline. There are plenty of examples in Texas where carp coexist without adversely affecting the other species of fish in the lake.

Point well made!