In collaboration with Dr. Gregory Ruiz at SERC, we are studying the patterns, sources and consequences of exotic species introduced into marine and estuarine ecosystems. Our program is continental in scale, and our main study sites focus on Chesapeake Bay (Maryland and Virginia), Prince William Sound (Alaska), San Francisco Bay (California) and Tampa Bay (Florida), and many other coastal sites along all three coasts of North America and around the world (see SERC's Invasions Biology section of this website, as well as the Ballast Water Information Clearinghouse on the SERC website).
Blue Catfish Watch
Show us your blue catfish catch! Collaborate with scientists at the Smithsonian Environmental Research Center to help us track the expanding range of the non-native blue catfish into the upper Chesapeake Bay and into Delaware Bay and the Delaware River. Join the effort using Project Noah, a free app for citizen science monitoring and ecological data collection. Report blue catfish sightings from the Chesapeake Bay using MD Blue Catfish, and from Delaware Bay and the Delaware River using DE Blue Catfish.
Native to the Mississippi, Ohio and Missouri Rivers, blue catfish were introduced to Virginia for sport fishing beginning in 1974. Since introduction, these non-native top predators have expanded their range into many of Maryland’s tributaries, including the Nanticoke, Patuxent, Choptank, Susquehanna and Sassafras Rivers. Due to their large size and adult predatory feeding behavior, blue catfish are consuming many native fish species, such as white perch, largemouth bass, American shad, river herring and menhaden. Knowing where and when these catfish are being caught is an important part of understanding their rising impact on the Chesapeake Bay ecosystem. Remember that it is illegal in Maryland, Virginia, and Delaware to transport and release live blue catfish.
Help us collect data by uploading photos of blue catfish that you or others catch, along with the date, the location where you caught the fish (be as specific as possible including GPS coordinates if you have them), and the length of the fish. Please only report fish from Chesapeake Bay, Delaware Bay, and the Delaware River and their tributaries. If you catch a blue catfish in the Patuxent River with a pink tag near the dorsal fin (see photo below), please release it back into the water - it is one of the tagged catfish that we are tracking.
Identifying Blue Catfish
Blue catfish (Ictalurus furcatus) have a bluish-gray body and a deeply forked tail. Unlike channel catfish, they do not have spots on their body. One feature that distinguishes blue catfish from other catfishes is the prominent straight edge on their anal fin; other catfishes, including the similarly colored white catfish, have a rounded anal fin (see photo above).
Blue Catfish in the Chesapeake Bay
We are working to understand the dispersal patterns, habitat use, diet and ecosystem-level effects of non-native blue catfish (Ictalurus furcatus) in Maryland tributaries of Chesapeake Bay. Due to their large size, relatively high salinity tolerance and adult predatory feeding behavior, blue catfish have the potential to alter food webs and ecosystem processes in the places they become established.
Blue catfish are omnivores that feed on a range of prey items including fish, aquatic insects, crustaceans and bivalves. Blue catfish undergo a shift in diet from mostly invertebrates to mostly fish with increasing size. The introduction of this new top predator could have detrimental effects in the Chesapeake Bay, including reducing the abundance of native fishes, compromising the recovery efforts of important anadromous fishes (shad, alewife, and blueback herring), and accumulating toxins that could be consumed by birds of prey and humans. We are using a number of unique approaches to determine the feeding patterns of blue catfish in Maryland tributaries, including stomach content analysis, stable isotopes to determine trophic level, and genetic barcoding to determine the species of visually unidentifiable gut contents. These data will allow us to determine the competitive interactions that blue catfish have with native fishes and the impact that they have on prey species and ecosystems in Chesapeake Bay.
Blue catfish are the largest and most migratory species of catfish in North America, yet little is known about their movement within the Chesapeake Bay watershed. In their native waters, blue catfish have been known to migrate great distances, sometimes greater than 200 km, between different habitats used for spawning, feeding and overwintering. We are tagging individual catfish with acoustic transmitters to track movement, migration, habitat use and possible dispersal among the tributaries of the Chesapeake Bay. As of December 2014, we have tagged 14 blue catfish in the Nanticoke River and 23 in the Patuxent River.
Along for the Ride: Invasive Species in Ballast Water
Historically, a wide variety of species have been introduced by fouling organisms on ships and in association with oyster culture, as well as other intentional and unintended modes. In recent decades, the most important mechanism of introductions is from planktonic larvae transported world-wide among shipping ports by huge volumes of ballast water taken up and released by commercial cargo ships. Chesapeake Bay receives the greatest quantities of ballast water released into ports of the eastern U.S. and second largest volume of any U.S. port. With funding from the U.S. Coast Guard and Maryland Sea Grant, we have characterized the composition and viability of the planktonic community in ballast water released into Baltimore and Norfolk harbors; and we have developed an extensive historical database for the invasive species of Chesapeake Bay.
Prince William Sound, Alaska, receives the third largest volume of ballast water delivered to U.S. ports. With funding from US Fish & Wildlife Service, Regional Citizens' Advisory Council of Prince William Sound, National Sea Grant, and the oil shipping industry, we have measured the biological characteristics of plankton in ballast water of oil tankers arriving to Port Valdez at the terminus of the trans-Alaska pipeline. We also surveyed native and invasive species at sites in the Aleutian Islands, Cook Inlet, Prince William Sound, and Southeast Alaska. The work in Alaska provides the first assessment of invasive species in this high latitude ecosystem.
We are also evaluating the ecological roles of exotic species in coastal ecosystems of the world, and we are assessing broad patterns of invasion along North American shores with varying latitude to Central America.
For more information and details see the SERC Invasions Biology web page.