Reduced condition factor of two native fish species coincident with invasion of non‐native Asian carps in the Illinois River, U.S.A. Is this evidence for competition and reduced fitness?

Abstract

Non‐native, Asian carps bighead Hypophthalmichthys nobilis and silver Hypophthalmichthys molitrix have been present in the Illinois River since the early 1990s. The Long‐Term Resource Monitoring Program (LTRMP) has been collecting bighead and silver carps in routine monitoring of the La Grange Reach, Illinois River, since 1995 and 1998, respectively. Despite variable recruitment, Asian carps abundance and biomass have increased since 2000, as evidenced by commercial landings, and Asian carps now dominate the fish community on La Grange Reach. Previous research suggests dietary overlap among bighead and silver carps and two native Illinois River fishes, gizzard shad Dorosoma cepedianum and bigmouth buffalo Ictiobus cyprinellus. Total length and mass data from c. 5000 fishes were used to test for changes in gizzard shad and bigmouth buffalo body condition after Asian carps establishment and investigate potential competitive interactions and changes in fitness. Analyses revealed significant declines in body condition of gizzard shad (−7%) and bigmouth buffalo (−5%) following the Asian carps invasion from 2000 to 2006. Segmented regression analyses showed no significant change in the rate of decline in gizzard shad condition after 2000, whereas the rate of decline in bigmouth buffalo condition increased significantly after 2000. Statistically significant differences in gizzard shad condition after Asian carps establishment (2000–2006) was observed, whereas condition of bigmouth buffalo was significantly lower in all years following Asian carps establishment as compared to 2000. Declines in gizzard shad and bigmouth buffalo condition were significantly correlated with increased commercial harvest of Asian carps and poorly correlated with other abiotic and biotic factors (e.g. temperature, chlorophyll a and discharge) that may influence fish body condition. These results may suggest that Asian carps are influencing native planktivore body condition, and future research should focus on determining whether food is limited in the Illinois River for native planktivores and other fish species.

Recruitment sources of invasive Bighead carp (Hypopthalmichthys nobilis) and Silver carp (H. molitrix) inhabiting the Illinois River

“…Low-velocity nearshore and backwater habitats that do not differ in water δ 18 O from the main river channel may represent the primary habitats used by age-0 Bighead and Silver carps; these habitats are more extensive than River. This finding is somewhat surprising considering that Bighead Carp were detected and became established in the Illinois River prior to Silver Carp (Peters et al 2006;Irons et al 2007). …”

“…Both species subsequently escaped confinement and established naturally reproducing populations in the Mississippi, Ohio, Missouri, and Illinois rivers (Chick and Pegg 2001). Abundance and biomass of Bighead and Silver carps have increased exponentially in the Illinois River (Sass et al 2010;Irons et al 2011); available evidence indicates that competition resulting from similar diet composition among bigheaded carps and native filter-feeding fishes (Sampson et al 2009) may negatively affect growth and condition of the native species (Schrank et al 2003;Irons et al 2007). The high densities of Bighead and Silver carps in the Illinois River and their capacity for rapid, long-distance movement (Peters et al 2006;DeGrandchamp et al 2008) have led to concerns regarding these species invading the Great Lakes via the artificial Chicago-area waterways that link the Illinois River drainage with Lake Michigan, with potentially serious consequences for Great Lakes food webs and the economically important recreational and commercial fisheries they support (Kolar and Lodge 2002;Cudmore and Mandrak 2011).…”

Length-Weight Relationships for Three Asian Carp Species in the Missouri River

“…Asian carp may have moved upstream into the Gavins Point reach during spawning, which may explain the high relative condition for large fish in Schrank and Guy (2002) reported the relationship between weight and length was highly similar between male and female bighead carp in the Missouri River; however, their sampling was not conducted during the peak spawning period, which precluded comparisons of condition between sexes of ripe fish. Bighead and silver carp will likely have adverse affects on all life stages of native species because they feed on plankton, the primary food source of several adult fish (Irons et al 2007, Sampson et al 2009), larval fish (Schrank et al 2003), and mussels (Kolar et al 2007). Grass carp adversely modify preferred fish habitats, disrupt food webs, and modify trophic structure (Conover et al 2007).…”

“…Schrank et al (2003) reported dietary overlap between age-0 bighead carp and paddlefish (Polyodon spathula) in laboratory studies. Sampson et al (2009) reported bighead carp dietary overlap with gizzard shad (Dorosoma cepedianum) and bigmouth buffalo (Ictiobus cyprinellus) in the Illinois River and Mississippi River, and condition of these two native species has declined since establishment of Asian carp (Irons et al 2007). …”

“…Although sufficient numbers of Asian carp were captured for condition analyses, weight measurements were not routinely collected which hrther limited our sample size. In areas where Asian carp are expanding their range, we recommend routine measurements of length and weight be done for Asian carp as well as native fish species with similar feeding habits to facilitate analyses of condition to assess competitive interactions (Irons et al 2007, Sampson et al 2009.…”