Consumption of Non-Native Bigheaded Carps by Native Blue Catfish in an Impounded Bay of the Upper Mississippi River

Abstract

Adult bigheaded carps Hypophthalmichthys spp. have never been observed in the diets of native fishes in the Mississippi River Basin. In addition, blue catfish Ictalurus furcatus diet preference and foraging behavior have never been studied in the presence of non-native bigheaded carps in the Mississippi River system. We examined the gut contents of adult blue catfish (567–1020 mm, n = 65), captured from a Mississippi River backwater using trammel nets. All items in diets were separated and enumerated, and all fish-like diet items were genetically identified to confirm species-level ID. Bigheaded carp ages were determined by sectioning hard structures (pectoral spines, post-cleithra, and vertebrae). Adult silver carp Hypophthalmichthys molitrix (age 3–5, mean = 3.9 years, SE = 0.2; n = 21) had the highest frequency of occurrence (70%) and constituted the greatest percentage by number (58%) and weight (60%) in/of blue catfish diets. Gizzard shad Dorosoma cepedianum ranked second by all three measures (34%, 25%, and 26%). Finally, 50% to 100% of probable age-based sizes of silver carp exceeded gape measurements of blue catfish, suggesting scavenging was the dominant means of predation. More intensive sampling efforts are required to determine the system-wide importance of bigheaded carp in blue catfish diets.

Predation of invasive silver carp by native largemouth bass is size-selective in the Illinois River

“…Genetic analysis was performed to determine prey species of heavily digested diet items. We used the method previously described by Anderson et al 20 and Locher et al 19 because it was optimized for the suite of prey items in the Illinois and Mississippi Rivers, especially including the invasive silver carp. Briefly, we extracted DNA from unknown tissues collected during diet analysis and determined consensus prey species identification by using barcode primer sequences designed for use in fishes, modified from Ivanova et al 39 , Leray et al 40 , Sarri et al 41 and De Barba et al 42 .…”

“…Briefly, we extracted DNA from unknown tissues collected during diet analysis and determined consensus prey species identification by using barcode primer sequences designed for use in fishes, modified from Ivanova et al 39 , Leray et al 40 , Sarri et al 41 and De Barba et al 42 . Consensus identification for each diet content was reached based on repeatability across multiple domains and identity score 19 . Non-fish identifications and highly improbable assignments due to geography or taxa were discarded 19 .…”

“…Consensus identification for each diet content was reached based on repeatability across multiple domains and identity score 19 . Non-fish identifications and highly improbable assignments due to geography or taxa were discarded 19 . Because some fish were identified only to family level using hard structures found during diet analysis, fish identified to species by genetic analysis were then grouped into their respective families for the frequency of occurrence analysis.…”

“…Therefore, understanding which native predators consume silver carp and at what frequency, and determining the sizes of silver carp that native predators are capable of eating would be important considerations in the implementation of native predator enhancement in the management of invasive silver carp. Blue catfish ( Ictalurus furcatus ) are known to consume adult silver carp 19 . In addition, several predators native to Midwestern rivers, including shortnose gar ( Lepisosteus platostomus ), white bass ( Morone chrysops ), black crappie ( P o moxis nigromaculatus ), channel catfish, smallmouth bass ( Micropterus dolomieu ) , largemouth bass, white crappie ( Pomoxis annularis ) , yellow perch ( Perca flavescens ) , flathead catfish ( Pylodictis olivaris ), freshwater drum ( Aplodinotus grunniens ), and yellow bass ( Morone mississippiensis ) , are known to consume young of the year (YOY) silver carp 20 , 21 .…”