Battle of the Carps: Common Carp VS Grass Carp

Grass carp and common carp are two species of fish that are often confused with each other. They are both large, bottom-feeding fish that are native to Europe and Asia. However, there are some key differences between the two species.

Origin and Distribution

• Grass carp (Ctenopharyngodon idella) are native to rivers and lakes in eastern Asia, from northern Vietnam to the Siberian-China border. They were introduced to the United States in the 1960s as a biological control agent for aquatic weeds, but some of them escaped or were released into the wild and established populations in many waterways. Grass carp are now considered an invasive species in most states and are regulated or prohibited by law.
• Common carp (Cyprinus carpio) are native to Europe and Asia, especially eastern Europe and Germany. They were brought to the United States in the 1800s as a food and sport fish, but they also escaped or were released into the wild and spread throughout the country. Common carp are not considered invasive in most states, but they may compete with native fish or degrade water quality in some areas.

Common Carp

Grass Carp

Appearance and Anatomy

• Grass carp have a dark olive color with pigmentation outlining their scales. They have an oblong body shape with a flattened head and a slightly downturned mouth. Their eyes are centered on their head and they have no barbels (whisker-like appendages) at the corners of their mouth. Their dorsal fin is short and has 8 to 10 soft rays. Grass carp can grow up to 6 feet 6 inches long and weigh up to 90 pounds.
• Common carp have a yellow, golden, brown or gray color with less pronounced scales. They have a deep-bodied shape with a long dorsal spine and a pair of barbels on each side of their mouth. Their mouth is angled downward and their eyes are positioned higher than their mouth on their head. Their dorsal fin is long and has 17 to 21 soft rays. Common carp can grow up to 47 inches long and weigh up to 88 pounds.

Habitat and Behavior

• Grass carp and common carp prefer similar habitats, such as large rivers and lakes with slow-moving water and abundant vegetation. However, they may differ in their tolerance to temperature, salinity and oxygen levels.
• Grass carp can tolerate a wide range of temperatures, from 32°F to 104°F, but they prefer warmer waters above 68°F. They can also tolerate low salinity levels up to 10 parts per thousand (ppt), but they prefer freshwater below 1 ppt. Grass carp need high dissolved oxygen levels above 5 milligrams per liter (mg/L), but they can survive short periods of low oxygen levels down to 0.5 mg/L.
• Common carp can also tolerate a wide range of temperatures, from 35°F to 95°F, but they prefer cooler waters below 77°F. They can also tolerate high salinity levels up to 35 ppt, but they prefer freshwater below 5 ppt. Common carp can survive low dissolved oxygen levels down to 1 mg/L, but they prefer higher levels above 4 mg/L.

Diet and Feeding

• Grass carp and common carp are both omnivorous, meaning they eat both plant and animal matter. However, they have different preferences and impacts on their food sources.
• Grass carp are primarily herbivorous, meaning they eat mostly plants. They feed on aquatic vegetation such as algae, submerged plants, emergent plants and floating plants. They can consume up to 40% of their body weight per day in plant matter. Grass carp have a pharyngeal apparatus (a set of teeth in their throat) that helps them grind up plant material.
• Common carp are also herbivorous, but they also eat more animal matter than grass carp. They feed on aquatic vegetation as well as insects, worms, crustaceans, mollusks, fish eggs and small fish. They can consume up to 20% of their body weight per day in food. Common carp have a pharyngeal apparatus as well as molar-like teeth in their mouth that help them crush food.

Ecological Impact

• Grass carp and common carp have different ecological impacts on their habitats and native species. Grass carp are generally considered more harmful than common carp, as they can cause significant changes in the aquatic ecosystem.
• Grass carp can reduce or eliminate aquatic vegetation by consuming large quantities of plant matter. This can affect the water quality, nutrient cycling, sedimentation, erosion, oxygen levels, light penetration, temperature and pH of the water. It can also alter the habitat and food resources for other aquatic organisms, such as fish, amphibians, reptiles, birds and mammals. Grass carp can interfere with the reproduction of other fish species by eating their eggs or larvae, or by destroying their spawning grounds. Grass carp can also compete with or prey on native fish when plant food is scarce. Grass carp are considered an invasive species in most states and pose a high risk of ecological damage.
• Common carp can also affect aquatic vegetation by uprooting plants or stirring up sediments while feeding. This can increase turbidity, reduce light penetration and oxygen levels, and release nutrients and pollutants into the water. However, common carp do not consume as much plant matter as grass carp and may not cause as much reduction in vegetation cover. Common carp may also compete with native fish for food or space, or degrade their habitat by increasing sedimentation or nutrient loading. However, common carp are not considered invasive in most states and their ecological impact is unclear or variable.

Positive impacts

• Grass carp can be used to control the growth of aquatic weeds, which can improve water quality and create more habitat for native fish and other aquatic organisms.
• Common carp are a popular food fish and can be used to improve the sustainability of aquaculture. They are also a popular sport fish and can provide recreation and economic benefits to communities.
• Negative impacts
• Grass carp can be invasive and can cause significant changes to aquatic ecosystems.
• Common carp can compete with native fish for food and space, and can degrade water quality by uprooting plants and stirring up sediments.

It is important to manage both grass carp and common carp populations so that they do not have a negative impact on the environment. This can be done through a variety of methods, such as stocking, harvest, and habitat management.

Conclusion

Grass carp and common carp are two important fish species that can be found in a variety of habitats around the world. They have both positive and negative impacts on the environment. It is important to understand the differences between these two species so that we can manage them effectively.