Invasive species always have varying impacts on the ecosystem to which they are introduced. The introduction of the blue catfish (Ictalurus furcatus) has been treated with opposition from some due to its potential to wipe out native species, thus affecting the balance of the ecosystem in question. However, many believe that the value of the blue catfish as a sport and commercial target fish outweighs the harm done to the native populations or ecosystems.
As the blue catfish is a predatory fish with no known natural predators in US waters, fisherman report that blue catfish have been replacing native sport fish is some areas and outcompeting other species for food resources as well. While this does negatively affect the commercial and sport fisheries that depend on the fish that are being replaced by blue catfish, the blue catfish fishery is so lucrative that it accounts for the loss of revenue due to loss of native species.
Introduction Whenever an invasive species begins to spread throughout a certain ecosystem, the natural balance of the ecosystem is usually altered in several different ways by the characteristics of the invasive species in question. More specifically, aquatic invasive species have the capability to change factors such as water quality, species diversity, and aquatic vegetation which in turn affects industries that depend on that ecosystem.
The United States has had 138 invasive aquatic species (Pimentel, Zuniga & Morrison 2005) introduced to its waterways, mostly in regions that typically have a warm climate. Due to the introduction and subsequent establishment of these species, forty-four different species of fish native to the United States are currently threatened or endangered. A study recently conducted put the economic and ecological costs to the United States from the negative effects of invasive species to be around 137 billion ollars annually (Pimentel et al. 2000). The Chesapeake Bay Watershed, one of Virginia’s and the East Coast’s biggest and most important waterways has been in recent years affected in this way by several invasive species, the most serious species being the blue catfish (Ictalurus furcatus). The blue catfish is marked in both Virginia and Maryland as one of the top five “species of concern” (Higgins 2006) regarding damage potential to the ecosystem and the industries that are supported by it.
While blue catfish are native to the Ohio, Mississippi, and Missouri river basins in the south and central area of the United States (Schloesser et al. 2011), they are not indigenous to any waterways of Virginia. Blue catfish were originally introduced to the Chesapeake Bay Watershed in the 1980’s as part of an attempt by the US Fish and Wildlife Service and Virginia Department of Game and Inland Fisheries to improve the sport fishing industry of Virginia and the surrounding areas.
These fish were only ever intentionally stocked in the James, Mattaponi, and Rappahannock rivers but by the early 1990’s they could be found in the upper Potomac, Pamunkey, and Piankatank rivers. The main cause for concern regarding the rapid spread and establishment of this fish into the Chesapeake Bay Watershed is due to its characteristics as a large, predatory fish that has no natural predators to keep the population in check. Blue catfish are also the largest established species of catfish in the United States, reaching lengths over five feet and weighing upwards of one hundred pounds.
This characteristic, combined with the typical feeding habits puts them in competition with several other large predatory fish such as the striped bass (Morone saxatilis), fish that play a vital role in the sport fishing industry of the Chesapeake Bay and all of its tributaries. While catfish are generally thought to be bottom feeders and scavengers, blue catfish have similar diets to that of striped bass which has raised concerns about competition between the two species for resources (Graham et al. 1999).
As the blue catfish doesn’t have any natural predators in the waterways it currently is known to occupy, this is a legitimate concern for the sport and commercial fishing industries that depend of the Bay and its indigenous fish populations for revenue. U. S. Invasive species Around 50,000 different species classified as invasive have been introduced to the United States total since the country’s beginning. Of these invasive species, 138 have been fish introduced into regions with warm climates such as Florida (Courtenay et al. 1991; Courtenay, 1993, 1997). Many of these species cause damage to the native ecosystems into which they are introduced – some native fish go completely extinct due to resource depletion by the invasive species, some hybridize with the native species, or some species are just reduced in numbers. However, some of the invasive species such as cows, corn, and other food production organisms now provide for 98% of the United States’ food supply (USBC, 2001).
Ecology of the Blue Catfish The blue catfish (Ictalurus furcatus) is currently the largest catfish in US waters, the common name coming from their distinct coloration pattern – blue catfish are have blueish-silver backs, grey sides, and completely white undersides. Ictalurus furcatus is currently found in 29 states in the US, and while blue catfish are native to many southeastern and central southern states they have been introduced to many other states such as Maryland, Virginia, California, and Oregon.
Virginia began to stock the blue catfish in 1974, and it rapidly began spreading across the waterways in the state. Around a decade later, many sport and commercial fisherman began to report that the blue catfish was replacing the native channel catfish in many different types of ecosystems ranging from shallow estuaries to large river watersheds. However, the blue catfish has been providing very productive and profitable sport fisheries in the areas where it has become established. Several fee fishing lakes have also hybridized blue catfish with native channel catfish ith good sport fishing results. Blue catfish generally prefer large, open expanses of water such as bays and deep channels of rivers, however this species can also be found in backwaters and shallow estuaries. More specifically, they are found in areas where the water in murky or cloudy, as they do not hunt primarily by sight. Like several other species of catfish, the blue catfish can tolerate moderate levels of salinity, which is another explanation for their rapid spread across Virginia waterways.
Blue catfish migrate the most out of the catfish family, as th travel upstream in the spring and downstream in the fall due to changes in water temperature – always moving where the water is the warmest. Economic costs and benefits Out of the estimated 200 invasive species in the Chesapeake Bay Watershed, 18 are aquatic. The blue catfish is the one of the 18 that poses the biggest threat to the industries that depend on the ecosystem of the Bay for revenue, while still actually supporting an important commercial industry.
The blue catfish fishery is one of the most productive sport and commercial fisheries in Virginia, especially in places such as the James, Chickahominy, and Pamunkey Rivers which all feed into the Chesapeake Bay. ***Insert facts here about that* However, an industry that is as equally important economically and ecologically is currently being threatened in the Bay by the spread of blue catfish. The striped bass fishing industry in Virginia and Maryland is one of the most productive on the East Coast, as Virginia and Maryland account for two-thirds of the total catch on the Atlantic Coast (Koo 1970).
Striped bass and catfish share many of the same food sources, feeding on aquatic life such as fish, insects, crayfish, and fingernail claims. Unlike striped bass however, blue catfish have no natural predators to check population levels in balance, so striped bass are increasingly becoming more at risk of being outcompeted for food sources. In addition to this, blue catfish also have the potential to outcompete several other native species, such as the channel catfish – and possibly drive other species that depend on common food sources to extinction which would upset the balance of the ecosystem in the Bay.
