Invasive species have the potential to completely flip an ecosystem upside down. In our mind the water bodies in Ontario are our crown jewel and we want to do our part to ensure they remain a prized resource.
Todays invasive species is Silver Carp!
We will cover why they are a threat to the Canadian waters of the Great Lakes, why anglers play an important role in monitoring for them, and what they can do to help stop the spread!
When you think about the invasive Asian Carp the image that likely comes to mind is fish jumping out of the water hitting boaters as they drive by, or the video of those water skiing behind the boat trying to catch them as they jump. While not all asian carp species behave this way the particular one that does is the Silver Carp. Despite the entertainment value of these videos this species has detrimental impacts to any water body system it enters. As of now Silver Carp have been limited to areas south of Wisconsin along the mississippi river system and its tributaries but it doesn't take much to connect into the great lakes from here. Once in the great lakes the area is so large they will be near impossible to contain; look how difficult it has been in the mississippi river alone!
History & Biology
Silver Carp, or Hypophthalmichthys molitrix are one of the four species of invasive Asian carps. They are native to large rivers, canals and lakes in eastern Asia. They are closely related to Bighead Carp, another species of Asian carps, and have been known to hybridize with that species producing viable, reproductive offspring. Along with the other species of Asian carps, Silver Carp were introduced to the Southern U.S. in the 1960's for use as biological control in aquaculture facilities. Flooding events allowed this species to escape these facilities and eventually make their way into the Mississippi River Basin.
They can efficiently strain suspended material from the water with specialized gill rakers that resemble sponge-like plates making them extremely resilient in any water conditions. Like the Bighead Carp, they lack a true stomach which requires them to feed almost continuously. They can eat from 5-20% of their body weight in plankton per day!
What is most unique to Silver Carp, and often what people think of when they hear the term Asian Carp, is their ability to jump 9 feet or more out of the water. Researchers believe that they do this due to them being startled by vibrations in the water, such as boat engines. This poses a hazard for anglers, boaters and other recreational users. This high flying, jumping invader are a schooling species and can be found in large numbers.
Identification
Silver Carp are deep-bodied, or wide, with a moderately large and broad head encompassing just under one third of their body size. They have a toothless upturned lower jaw and eyes are located below the axis of the body. Their body is silver with a slate gray head and dorsal surface and white belly with a keep extending from the anal fin to the throat.
Habitat
Silver Carp prefer habitats in the standing waters of rivers, canals and lakes, tolerating water
temperatures from 43 to 82 degrees Fahrenheit. In other words they can live just about everywhere! Silver Carp feed primarily on phytoplankton and can out-compete many native fish juveniles. Silver Carp can mature in 2-4 years and commonly weigh 20 lbs. When older, they can reach a maximum size of more than 80 lbs! They can eat from 5-20% of their body weight in plankton per day! Currently, Silver Carp are found throughout the Mississippi River. There is an electric dispersal barrier in the Chicago Sanitary and Ship Canal within the Chicago Area Waterway, which is the largest known continuous connection between the Great Lakes and Mississippi River basins. These barriers are designed to prevent fish migration between the Mississippi River and Great Lakes basin. Equipment generates a direct current pulse through the electrodes, creating an electric field in the water that discourages the fishes from crossing. The design does not prevent waterway vessel traffic. Silver Carp are currently up the river basin and stopped at the electric barrier.
Impact To Great Lakes
While the term Asian carps refers to four separate species, each is different and therefore, would have their own unique impacts to the Great Lakes if they were to establish. Silver carps are planktivorous, meaning they eat plankton. Unlike Bighead Carp which consume zooplankton, Silver Carp consume phytoplankton. This means the two species do not compete for food with one another but will decimate the population from all sides. Plankton are a very important food source for many native species in the great lakes. Since plankton is at the bottom of the aquatic food web, one way or another, most species depend on plankton for survival. Since Silver carps lack a true stomach and continuously filter large volumes of water that contain this vital food source which WILL lead to a large decrease in the population sizes of native planktivorous species, such as:
Alewife
Bloater
Cisco
Rainbow Smelt
The decline could negatively impact predatory fishes that consume these forage such as:
Yellow Perch
Lake Trout
Walleye
Along with ecological impacts, these fish would cause negative economic impacts to the Great Lakes basin. They could impact the Canadian commercial fishing industry by causing a reduction in commercial catches. Commercial catches would be reduced due to decreases in native fish population sizes and overall quality as a result of direct competition with these fish for food. There would also be an increase in operational costs of commercial fishing due to the need to travel farther to catch fish, resulting in decreased profits.
Silver Carp would threaten the recreational boating industry. They can jump three meters out of the water and pose a huge threat to boaters by causing injury to passengers, and damage to boats and equipment. These impacts could cause an increase in operating and maintenance costs, and a reduction in interest and participation in the industry.
Silver carps would also impact recreational fishing by causing a reduction in populations of angling species, such as the ones listed above. Anglers contribute large amounts of money to the economy via fishing licenses, purchasing of fishing equipment and gear, and through tourism. Reduced recreational fishing opportunities would also have an impact on other businesses and livelihoods that depend on the development of this sector, such as bait and tackle shops.
As Silver carps continue their persistent movement north through the Mississippi River basin, deterring their entry to the Great Lakes is crucial in order to maintain its ecological balance and associated financial value.
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