One of the earliest non-native fish species to be widely released into North American waterways was the Common Carp. Stocks brought to the United States were likely sourced from populations already naturalized throughout much of western Europe after introductions originating from the fish’s native range in Eurasia, probably including the Danube and other watersheds east through the Volga. In western Europe, the species promised to be an abundant and easily cultivated food source. Under the same premise, carp were transported to the United States during the early 1800s and widely introduced into streams, lakes, and rivers throughout the country.
Common Carp thrive in nutrient-rich waters, particularly those subjected to sewage discharge and agricultural runoff, conditions which were already prevalent during the Common Carp’s initial introduction and have remained widespread ever since. Within these polluted streams, lakes, and ponds, introduced carp feed aggressively on benthic organisms and plants, stirring up decaying organic matter (mulm) from the substrate. This process raises turbidity in the water column and releases excessive amounts of the nutrient phosphorus resulting in unusually large algal blooms. Algal blooms can block sunlight from the longer-lived oxygen-producing vascular plants that grow in submerged environs. Growing beneath a dense cloud or blanket of algae can compromise the vigor of oxygen-producing vascular plants and disable their biochemical functions within the aquatic ecosystem. As the short-lived algae die, the bacteria that decay them begin to place increased oxygen demands on the water. With less oxygen being produced by both the vascular plants and the algae, and with oxygen consumption increased by the activity of decomposers, conditions can become fatal for fish and other organisms. This process is known as eutrophication. Because Common Carp are among the species most tolerant of eutrophic conditions, they tend to thrive in the conditions they create while the native fishes perish.
Common Carp spawn in the spring, usually from late April through June, when the water temperature is as low as 58 degrees and as high as 83 degrees Fahrenheit. This activity is often triggered by a rapid increase in water temperature. In a small lake, this may be brought on by a string of sunny days in late April or May. On larger streams and rivers, the temperature spike that initiates the spawn may not occur until warm rains and runoff enter the stream during June.
Common Carp are one of the most widely farmed and eaten fish in all the world. Here in the United States, they were introduced beginning two hundred years ago because they were favorable to the palate, grew to large size quickly, and were a source of much needed food. Today, the Common Carp is seldom found on the American dinner plate. Yet, pound for pound, it is one of the most abundant fish in many of our waters, particularly in man-made lakes. Like some of our other most invasive species—including Blue Catfish, Flathead Catfish, and Northern Snakehead—Common Carp are perhaps the most edible of our freshwater fishes. For many cultures, they are an important staple. For others, they are a delicacy or holiday treat. In America, they do horrendous damage to aquatic ecosystems following establishment as a food crop that almost never gets harvested. Did you realize that on the internet, there are literally hundreds of recipes and culinary videos available to show you how to prepare delicious dishes made with Common Carp? It’s true. And for the cost of a fishing license, you can catch all you want, usually several pounds at a time. So why not give the marine fisheries a break? Take the big leap and learn to eat invasive freshwater species instead.
