The role of trophic cascades in structuring freshwater communities has been extensively studied. Most of this work, however, has been conducted in oligotrophic northern lakes that contain highly vulnerable cyprinid prey: aquatic communities where trophic interactions are likely to be stronger than in many other systems. Fewer studies have been conducted in eutrophic systems or have examined the bottom-up effects of benthivorous fishes, and none have directly compared these effects to those of piscivores on ecosystem structure and function. We conducted enclosure experiments in eutrophic ponds to examine trophic effects of invasive benthivores (common carp-Cyprinus carpio L.), native piscivores (largemouth bass-Micropterus salmoides [Lacepède]), and their interactions with common centrarchid prey with well-developed anti-predatory behaviors (age-1 bluegill-Lepomis macrochirus Rafinesque and young-ofyear largemouth bass). At the end of the 60-day experiment, common carp had strong bottom-up effects that increased total phosphorus and turbidity while decreasing chlorophyll a biomass and macrophyte cover that resulted in decreased macroinvertebrate biomass and also decreased growth in both juvenile largemouth bass and bluegill. Piscivorous largemouth bass, however, did not affect the survival of either planktivorous juvenile largemouth bass or bluegill. Growth of juvenile largemouth bass was also not affected, but juvenile bluegill growth was significantly diminished, possibly due to nonconsumptive effects of predation. Our results suggest that, in a centrarchid-dominated eutrophic system, top-down effects of predators are overwhelmed by common carp-mediated bottom-up effects. These bottom-up effects strongly affected multiple trophic levels, thus altering aquatic community structure and function.

The common carp Cyprinus carpio was introduced to North America more than a century ago, but little research has focused on interactions between this invasive species and native fishes. We used large mesocosms (600 m2) within drainable 0.4‐ha ponds to examine the effects of adult common carp on (1) reproduction of largemouth bass Micropterus salmoides and bluegills Lepomis macrochirus and (2) growth and survival of the larvae and juveniles of these centrarchid species. In separate enclosures, adult bluegills or largemouth bass were stocked with or without common carp. In enclosures with common carp, turbidity was substantially higher, but both centrarchid species spawned and the densities and sizes of larval largemouth bass and bluegills were similar to those of larvae in enclosures without common carp. As juveniles grew, largemouth bass survived at a higher rate but were smaller in enclosures containing common carp compared with largemouth bass in enclosures without common carp. In a second experiment, we stocked known numbers of older juvenile centrarchids into enclosures and found decreased growth for both largemouth bass and bluegills. However, survival of largemouth bass was again higher in enclosures with common carp. Although centrarchid spawning was successful and larval growth and survival did not decrease in the presence of common carp, centrarchid growth slowed at the juvenile stage, probably due to food resource limitation resulting from direct competition with common carp for invertebrate forage, high turbidity caused by common carp, or both of these factors.

Angler surveys are reliant on the ability of anglers to accurately report various aspects of their fishing trips. Misidentification of sport fishes has been postulated as a source of error among angler surveys but has received little attention. We evaluated the overall ability of anglers to identify sport fishes common to Ohio and the potential impacts on catch estimates derived from angler surveys. During angler surveys conducted on lakes and reservoirs (2007, n = 34) and Ohio River tailwaters (2010, n = 3), anglers were presented with artist‐rendered images of 18 different sport fishes common to these waters. Anglers (lake and reservoir, n = 2,442; Ohio River, n = 458) were asked to identify sport fish by their common name. On average, anglers correctly identified sport fishes 42% of the time, but accuracy varied widely among species (lake and reservoir, range = 4.4–85.1%; Ohio River, range = 9.4–71.8%), with greater accuracy exhibited for the most common species (e.g., largemouth bass Micropterus salmoides). However, by grouping angler responses into species groups (e.g., black bass Micropterus spp., sunfish Lepomis spp.) angler identification of sport fishes was more reliable (lake and reservoir, mean = 83.4%; Ohio River, mean = 83.8%). Using these estimates of angler accuracy, we simulated the potential error in sport fish catch estimates using data from an angler survey conducted at one Ohio reservoir. These results suggested that misidentification error may result in a substantial error in catch estimates. A survey of North American fisheries management agencies regarding angler surveys and angler sport fish identification revealed that the majority of agencies group similar species for analysis and cited species misidentification by anglers as the primary reason for doing so. Received April 19, 2012; accepted August 17, 2012