Linking silver carp habitat selection to flow and phytoplankton in the Mississippi River

Abstract

Invasive silver carp (Hypothalmichthys molitrix) occurs throughout much of the Mississippi River and threatens the Laurentian Great Lakes. To quantify habitat selection relative to river flow and potential phytoplankton food, 77 adult silver carp were implanted with ultrasonic transmitters during spring 2008 through spring 2009 in adjacent upstream dammed and downstream undammed reaches (48 km total) of the Mississippi River. Sixty-seven percent of the fish were located. Selection of major river habitat features (dammed vs. undammed, backwaters, channel border, wing dikes, island side channels, and the main channel) was quantified. Flow rates and chlorophyll a concentration were compared between silver carp locations and random sites. Foregut chlorophyll a concentrations plus presence of macrozooplankton and detritus of 240 non-tagged silver carp were quantified. About 30% of silver carp moved upstream into the dammed reach, where average flow was slower and chlorophyll a concentration was higher. Silver carp selected wing dike areas of moderate flow (about 0.3 m/s) and elevated chlorophyll a (about 7 lg/L) relative to random sites. No silver carp occurred in areas where flow was absent. Wing dikes were preferred while the main channel was avoided. Chlorophyll a concentrations in guts were positively related to temperature and were unrelated to flow or river chlorophyll a concentration. Macrozooplankton and detritus were rare in guts. Silver carp seek areas of low flow and successfully forage across a range of temperatures, flows, and chlorophyll a concentrations that occur in rivers and large lakes.

Trophic ecology and persistence of invasive silver carpHypophthalmichthys molitrixin an oligotrophic South African impoundment

“…The mean C:N mass of the lipid extracted fish was 3.4 ± 0.16. feeder. This supports the notion that they are indiscriminate filter feeders (Spataru and Gophen 1985, Kolar et al 2007, Sampson et al 2009, Calkins et al 2011. Nevertheless, defining their diet in FBD proved challenging, the ingested (stomach contents) and timeaveraged assimilated portion of their diet (stable isotopes) did not concur.…”

“…Hypophthalmichthys molitrix are well suited for biological control of phytoplankton but have been implicated as drivers of adverse ecological impacts in recipient ecosystems (Spatura and Gophen 1985, Irons et al 2007, Sampson et al 2009). Although initially described as a specialist phytoplankton filter feeder in their native range (Kolar et al 2007), studies conducted in invaded ranges described H. molitrix as an opportunistic, generalist filter feeder with a diet consisting of phytoplankton, zooplankton, bacteria, and detritus (Bitterlich 1985, Spataru and Gophen 1985, Lu et al 2002, Kolar et al 2007, Sampson et al 2009, Calkins et al 2011. High-density H. molitrix populations reportedly mediate changes in the zooplankton, phytoplankton, and fish community structure, initiating a decrease in the abundance of indigenous fish species despite having limited dietary overlap (e.g., Spatura andGophlen 1985, Irons et al 2007).…”

Detecting the movement and spawning activity of bigheaded carps with environmental DNA

“…The eggs likely came from the large number of fish that spawned above Americus, and the eggs drifted downstream during development. Changes in water levels and velocities have been previously linked with movements of bigheaded carps (Calkins et al ., ; DeGrandchamp et al . ) and other species (Lucas and Batley, ; Manion, ; Reynolds, ; Taylor and Cooke, ).…”

Disturbed fish fauna zonation as an indicator of large-scale human impact: A case study (2011-2012) of the large, lowland Warta River, Poland

“…With high probability, richer fauna in S4 was favoured by the existence of groynes (constructed usually along one of the banks), which significantly increased the diversity of available microhabitats (Barko, Herzog, Hrabik, & Scheibe, ) in the human‐impacted lower Warta. On the one hand, they created zones of stagnant water, enabling the occurrence of limnophilic species (Figure ; Calkins, Tripp, & Garvey, ). On the other hand, the stones that a groyne is built of favour rheophilic fauna, especially at groyne‐head where they are washed by faster flowing water (Bischoff & Wolter, ,b).…”