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• Blue Catfish are large freshwater catfish that range in color from silver-blue to slate gray with a light or white underside. The fish has a deeply forked tail and straight-edged anal fin with 30 – 35 rays. There is a single, serrated spine on each of the pectoral fins and dorsal fin.
  
• They eat a wide variety of prey items including blue crab, clams, American shad, American eel, and white perch. Blue catfish eat as much as 9.4% of their body weight daily. Although they are omnivores, the diet of large individuals is mostly other fish.
• Blue catfish are native to the Mississippi, Missouri and Ohio river basins of North America but were introduced into rivers of Virginia in the 1970s and 1980s to enhance recreational fishing.​
  
• Considered a freshwater fish, blue catfish can tolerate salinities up to 17 ppt for short periods and thrive in the eutrophic, brackish waters of Chesapeake Bay tributaries.
• They can live for more than 20 years and grow to over five feet long and weigh over 100 lbs. The state record in Maryland is 84 lbs.
• Notable specimens are 40 inches or longer and eligible for a FishMaryland Invasive Species Award.

• Blue crabs, American eels, American shad, white perch, and other economically and ecological important species are eaten by blue catfish.
• Introduced blue catfish have outcompeted and/or displaced native and non-native, beneficial catfishes (i.e., white catfish, channel catfish) in other regions.
• In the past 20 years blue catfish have spread into to all major tidal rivers of Maryland’s portion of Chesapeake Bay, and the upper bay.
• Blue catfish abundance has increased at an alarming rate in many areas. Blue catfish were first documented in the Patuxent River in the 2000s, but recent work estimated over 75,000 fish (8” or longer) in a 5 mile stretch of that river with densities of 1250 fish (8” or longer) per acre in some sections. Some researchers estimate the bay-wide population at more than 100 million fish.

• Blue catfish were initially introduced to Virginia tributaries of Chesapeake Bay in the 1970s and became abundant in the Potomac River in the 1990s. Now, commercial harvesters remove xx.x million pounds of blue catfish annually.
• The fish took advantage of high rainfall and low bay salinities in the late 2010s to disperse northward, into other major tributaries of Chesapeake Bay and the upper bay. Fish are now common north of the Bay Bridge and the Susquehanna River is a hotspot for anglers. 
  

• Resource managers, concerned about blue catfish and their spread throughout the Chesapeake Bay watershed, adopted an Invasive Catfish Policy in 2012 and in 2014, formed the Invasive Catfish Workgroup. The workgroup brings in multiple stake holder groups to coordinate research and evaluate impacts of invasive catfishes in Chesapeake Bay.
• Maryland adopted the Fishery Management Plan for Tidewater Catfish and Aquatic Nuisance Species Plan to mitigate the economical and ecological damage of blue catfish.
• The department is working with other agencies, federal and state partners, educational institutions, and commercial and recreational stakeholders to research and manage blue catfish.
  

Fishery Management Plan for Tidewater Catfish​​

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More Information:

• Fact Sheet
• Chesapeake Bay Blue Catfish: Invasive, but Delicious and Nutritious!​
• ​​El Pez Bagre azul​

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What can you do? 

• The department asks anglers to remove and kill any blue and flathead catfish they catch.
• Catch and release of these fish is discouraged, as pose a legitimate threat to the Chesapeake Bay watershed.​
• In Maryland, it is illegal to transport live blue and flathead catfish into another body of water, anyone in violation of this can be fined up to $2,500.
• To report illegal transport or unauthorized introductions of invasive species please contact the Natural Resources Police at 800-628-9944.
  

Report Catching a Blue Catfish or a Flathead Catfish
using Maryland's Invasive Species Tracker​ or the Angler's Log​

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Studies and Reports

1. Iwanowicz, D. D., Schill, W. B., Sanders, L. R., Groves, T., & Groves, M. C. (2019). Establishing molecular methods to quantitatively profile gastric diet items of fish-application to the invasive blue catfish (Ictalurus furcatus). Open-File Report-US Geological Survey, (2019-1021).
   1. Understanding the diet of invasive species helps researchers to more accurately assess the health, survivorship, growth, and stability of an invasive fish species, as well as their effects on native populations. Techniques capable of identifying multiple prey species from fish stomach contents have been developed. In this study, a multi-locus metabarcoding approach was used to identify fish and invertebrate prey in stomach samples of Ictalurus furcatus (blue catfish), which were collected from two sites on the Mattawomen Creek and Nanjemoy Creek in Maryland. The mitochondrial 12S (mt12S) and mitochondrial 16S (mt16S) gene regions were sequenced and compared. First, a mock sample for each gene region was created with the pooled polymerase chain reaction product of known fish species, and quantities of the sample were used to determine efficacy of the amplicon. Results varied between gene regions analyzed. Then, when using the mt12S primers, next-generation sequencing determined that nine fish species were found at levels greater than 1 percent of the diet of blue catfish. The most common species were Perca flavescens (yellow perch) and Cyprinus carpio (common carp). The mt16S gene region analyses found 10 fish species at greater than 1 percent of the diet, which primarily included Orconectes limosus (spinycheek crayfish), Alosa pseudoharengus (alewife), and yellow perch. Partially digested eggs were identified using next-generation sequencing of yellow perch in two of the stomach samples, and a TaqMan® quantitative polymerase chain reaction (qPCR) assay was developed to more economically identify egg species in the future. The yellow-perch-specific TaqMan® qPCR assay was tested using primers that were developed to detect a 154-base-pair amplicon in the mitochondrial control region. Consumption of yellow perch eggs indicates that blue catfish could potentially negatively affect young-of-year recruitment of this native sportfish. Analyses of two gene regions helped confirm the major prey of the fish sampled and allowed identification of fish species as prey that were not included in a database for the two gene regions. We concluded that the mitochondrial ribosomal-marker-based next-generation sequencing method is useful in determining the prey of fish species.
   2. https://pubs.usgs.gov/of/2019/1021/ofr20191021.pdf
2. Aguilar, R., Ogburn, M. B., Driskell, A. C., Weigt, L. A., Groves, M. C., & Hines, A. H. (2017). Gutsy genetics: identification of digested piscine prey items in the stomach contents of sympatric native and introduced warmwater catfishes via DNA barcoding. Environmental Biology of Fishes, 100, 325-336.
1. A major focus of ecology is understanding trophic relationships and energy flows in natural systems, associated food web dynamics and changes in food webs due to introduced species. Predator-prey interactions are often assessed by examining stomach contents. However, partially digested remains may be difficult to accurately identify by traditional visual analysis. Here we evaluate the effectiveness of DNA barcoding to identify digested piscine prey remains in invasive Blue Catfish Ictalurus furcatus, non-native, but established Channel Catfish Ictalurus punctatus and native White Catfish Ameiurus catus from Chesapeake Bay, USA. Stomach contents were examined and piscine prey items were scored as lightly digested, moderately digested or severely digested. A 652 base pair region of the cytochrome c oxidase subunit I (COI-5P) mitochondrial DNA gene was sequenced for each prey item. Edited barcode sequences were compared to locally-caught and validated reference sequences in BOLD (Barcode of Life Database). A large majority of prey items were sufficiently digested to limit morphological identification (9.4 % to species and an additional 12.1 % to family). However, overall barcoding success was high (90.3 %) with little difference among the digestion classifications. Combining morphological and genetic identifications, we classified 91.6 % of fish prey items to species. Twenty-three fish species were identified, including species undergoing active restoration efforts (e.g., Alosa spp.) and commercially important species, e.g., Striped Bass Morone saxatilis, White Perch Morone americana, American Eel Anguilla rostrata and Menhaden Brevoortia tyrannus. We found DNA barcoding highly successful at identifying all but the most heavily degraded prey items and to be an efficient and effective method for obtaining diet information to strengthen the resolution of trophic analyses including diet comparisons among sympatric native and non-native predators.
3. Fabrizio, M. C., Tuckey, T. D., Latour, R. J., White, G. C., Norris, A. J., & Groves, M. (2016). Population Size and Survival Rates of Blue Catfish in Chesapeake Bay Tributaries.
1. This report comprises two studies conducted from 2012 to 2015 to estimate population size, survival rates, and movements of invasive blue catfish in Chesapeake Bay tributaries. The first study of population-size and survival was conducted in the James River, VA (Population Size and Survival Rates of Invasive Blue Catfish in Tidal Waters of the James River Subestuary). The second study on movement and survival of blue catfish was conducted in the Potomac River, the natural boundary between Maryland and Virginia (Movement Patterns and Survival Rate of Blue Catfish in a Non-Native Habitat Estimated with a Tagging Study). The Executive Summary of this report provides a synopsis of both studies.
2. https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=1066&context=reports
4. Schloesser, R. W., Fabrizio, M. C., Latour, R. J., Garman, G. C., Greenlee, B., Groves, M., & Gartland, J. (2011). Ecological role of blue catfish in Chesapeake Bay communities and implications for management.
1. Rapid increase in abundance and expanded distribution of introduced blue catfish Ictalurus furcatus populations in the Chesapeake Bay watershed have raised regional management concerns. This study uses information from multiple surveys to examine expansion of blue catfish populations and document their role in tidal river communities. Originally stocked in the James, York, and Rappahannock River systems for development of commercial and recreational fisheries, blue catfish have now been documented in adjacent rivers and have expanded their within-river distribution to oligo- and mesohaline environments. Range expansions coincided with periods of peak abundance in 1996 and 2003 and with the concurrent decline in abundance of native white catfish I. catus. Blue catfish in these systems use a diverse prey base; various amphipod species typically dominate the diet of smaller individuals ([FL]), and fishes are common prey for larger blue catfish (>300 mm FL). Recent studies based on stable isotope analyses suggest that adult blue catfish in these systems are apex predators that feed extensively on important fishery resources, including anadromous shads and herrings Alosa spp. and juvenile Atlantic menhaden Brevoortia tyrannus. Minimizing effects on Chesapeake Bay communities by controlling high densities of blue catfish populations is a primary goal of management, but conflicting demands of the commercial and recreational sectors must be resolved. Further, low market demand and human consumption concerns associated with purported accumulation of contaminants in blue catfish pose additional complications for regulating these fisheries.
1. https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=1009&context=vimsbooks

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