Hydrobiologia (2012) 693:169–181 DOI 10.1007/s10750-012-1106-0 PRIMARY RESEARCH PAPER Feeding patterns and population structure of an invasive cyprinid, the rudd Scardinius erythrophthalmus (Cypriniformes, Cyprinidae), in Buffalo Harbor (Lake Erie) and the upper Niagara River Kevin L. Kapuscinski • John M. Farrell • Michael A. Wilkinson Received: 16 July 2011 / Revised: 26 March 2012 / Accepted: 31 March 2012 / Published online: 19 April 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Feeding patterns and population structure and supplemented their diet with algae and fish in of the non-native rudd Scardinius erythrophthalmus spring and fall. Feeding intensity was positively (Linnaeus) were examined to understand their ecology correlated with water temperature, but significantly in Buffalo Harbor and the Niagara River. We hypoth- reduced during spawning. Rudd condition and growth esized that (1) the diet of rudds would be omnivorous, were greater than estimates from other populations, but contain greater proportions of macrophytes in suggesting increases in abundance and range expan- summer months, (2) feeding intensity would increase sion are possible. Furthermore, reproduction was with water temperature, and (3) condition and growth successful at lotic sites but very poor at sites without would be similar to other populations. We collected measureable flow, contrary to the paradigm of optimal rudds with a variety of gears in 2009 to test these rudd habitat. Research is needed to understand how hypotheses, and used data from 2007 to 2010 seining herbivory by abundant rudd populations affects native surveys to determine if the relative abundance of aquatic communities. young-of-the-year rudd differed among sites with different flow conditions. Rudds were mostly herbiv- Keywords Rudd Á Feeding ecology Á Herbivory Á orous; they consumed aquatic macrophytes in summer Invasive species Á Growth Handling editor: John Havel Introduction K. L. Kapuscinski (&) The rudd Scardinius erythrophthalmus (Linnaeus) is a College of Environmental Science and Forestry, State Eurasian cyprinid that was introduced to North University of New York, 104 Illick Hall, 1 Forestry Drive, Syracuse, NY 13210, USA America during the late nineteenth or early twentieth e-mail: [email protected] century (Burkhead & Williams, 1991; Mills et al., 1993). The popularity of rudd as a bait minnow J. M. Farrell facilitated its spread to at least 21 states (Nico et al., College of Environmental Science and Forestry, State University of New York, 250 Illick Hall, 1 Forestry Drive, 2010), and although reproducing populations became Syracuse, NY 13210, USA established, they did not reach nuisance levels and therefore received little attention from fisheries biol- M. A. Wilkinson ogists (Burkhead & Williams, 1991). In New Zealand, New York State Department of Environmental Conservation, 270 Michigan Avenue, Buffalo, NY 14203, however, rudd populations became abundant enough USA in several bodies of water to receive attention by 123 170 Hydrobiologia (2012) 693:169–181 researchers (Hicks, 2003). The rudd is typically populations. However, abundant populations of rudd classified as omnivorous but undergoes ontogenetic have recently been documented in Buffalo Harbor shifts in diet. Young-of-the-year (YOY) rudds in New (eastern Lake Erie) and the upper Niagara River Zealand fed on planktonic cladocerans and chirono- (Kapuscinski et al., 2012). The rudd comprised 38% mid pupae, switched to benthic invertebrates and some of the total trap-net catch in 2007 (n = 2,066 or 9 per submerged aquatic macrophyte (hereafter macro- net night; Kapuscinski & Wilkinson, 2008) and 56% in phyte) material as juveniles, and fed mostly on 2008 (n = 4,821 or 29 per net night; Kapuscinski et al., macrophytes when [150 mm in length (Lake et al., 2009). The rudd was the most abundant species 2002; Hicks, 2003). Using a bioenergetics model, sampled during 2007–2008, and catches during 2008 Nurminen et al. (2003) estimated that an omnivorous were about four times greater than catches for the next population of rudd in a shallow eutrophic lake most abundant species, the brown bullhead Ameiurus consumed approximately its weight in macrophytes nebulosus (Lesueur) (n = 1,260). These large catches (wet weight) each year. The captive rudds studied by of rudd in Buffalo Harbor and the upper Niagara River Lake et al. (2002) consumed up to 20% of their weight were unexpected, and potential effects on native species in Egeria densa Planchon daily in spring and 22% of are unknown. However, it is unlikely that the popula- their weight in macroalgae (Nitella spp.) daily in tion dynamics of native species can be understood and summer. Rudd populations are thought to alter mac- properly managed without an understanding of the rophyte assemblages in New Zealand and aid the dynamics and ecology of the invasive rudd. For spread of exotic macrophytes by selectively feeding example, if rudds are consuming macrophytes, this on native species (Lake et al., 2002; Hicks, 2003). important habitat for native fishes might be impaired Rudds typically grow to about 350 mm in total and the potential benefits of ongoing habitat restoration length and 1,800 g in weight (Crossman et al., 1992); efforts may be nullified or reduced. Therefore, we the largest rudd on record was 617 mm and 3,623 g conducted a study of rudd that focused on (1) describing (Sˇprem et al., 2010). Although many neotropical fishes the diet, including an examination of differences among are herbivorous, such large, macrophyte-consuming seasons and between sexes, (2) quantifying several fish are uncommon in temperate North American population parameters, including condition and growth, freshwater ecosystems. Therefore, an abundant rudd and (3) documenting successful natural reproduction population could negatively affect aquatic communi- and comparing the relative abundance of YOY among ties by altering macrophyte assemblages and acceler- sites with different flow conditions. By comparing this ating internal nutrient loading (eutrophication) by information on condition, growth, and reproductive means of remobilizing nutrients stored in sediments success to that reported for other populations, we can and macrophytes (Hansson et al., 1987; van Donk & acquire a better understanding of the status of rudd in Gulati, 1995; Vanni, 2002; Hicks, 2003; Nurminen the Buffalo Harbor/upper Niagara River ecosystem and et al., 2003). In addition, the rudd may affect aquatic guide future research and management efforts. communities by (1) creating novel trophic links that serve as contaminant pathways (alaKwon et al., 2006), especially in an Area of Concern like the Niagara River Materials and methods (Environmental Protection Agency, 2009), (2) com- peting with native fishes for benthic invertebrate prey as We attempted to capture 50 rudds monthly from May juveniles (Crossman et al., 1992; Hicks, 2003), (3) to August and November of 2009. Two hoop-style spreading parasites, diseases, and viruses among native trap-nets (1.23 m diameter hoops, 30.48 m lead, fishes (Popovic´ et al., 2001; Schlueter, 2010), and (4) 6.10 m wings) were set once each month from May hybridizing with golden shiner Notemigonus crysoleu- to August (Fig. 1). A total of 50 rudds were captured in cas (Mitchill) (Burkhead & Williams, 1991), thereby May (nets were set at 16:02 and 16:31 on May 20, causing genomic extinction (i.e., the loss of local emptied at 10:10 and 10:30 on May 21, and emptied evolutionary lineages; Allendorf & Luikart, 2007). and pulled at 8:53 on May 22), 50 in June (nets were Concern regarding the potential negative effects of set at 10:30 and 10:55 on June 8 and emptied and invasion by rudd in North American waters has been pulled at 9:15 and 9:40 on June 9), 39 in July (nets minimal due to the relative scarcity of established were set at 16:14 and 16:45 on July 28 and emptied and 123 Hydrobiologia (2012) 693:169–181 171 pulled at 11:35 and 11:50 on July 29), and only 4 in where P is the number of rudds with food in their gut, August (nets were set at 13:30 and 13:51 on August 24, Q is the number of food types, and Wij is the weight of emptied at 8:35 and 8:40 on August 25, and emptied food type i in rudd j. Monthly differences in MWi were and pulled at 8:35 and 8:50 on August 26). Trap-nets determined via Analysis of Variance (ANOVA); were abandoned after August due to poor catches. A Tukey’s multiple comparisons test was used to large-mesh bag seine (18.3-m long and 6-mm mesh) determine which means differed. An index of fullness, was used to supplement the August collection (37 which measures food intake relative to fish size rudds were captured during daylight hours on August (Hyslop, 1980; Jude et al., 1987), was calculated for 25), and electrofishing (Smith-Root boom shocking each rudd as: (weight of gut contents/total fish boat, pulsed DC, 500–1,000 V, 6–12 amps) was used weight) * 100. Differences in mean values of the on November 3 (51 rudds were captured during index of fullness among sexes (males, females, and daylight hours). Water temperatures were recorded on rudds of unknown sex) and among months were each capture date. Most rudds (n = 194) were stored determined via a two-factor ANOVA; Tukey’s multi- on ice until they could be transferred to the lab, ple comparisons test was used to determine which measured for total length (mm) and weight (g), means differed. examined for body color (categorized as olive or We used the Chi square goodness of fit test to orange/gold), and frozen. The 37 rudds captured while determine if the observed female:male sex ratio seining in August were measured for length in the differed from a 1:1 expectation. Similarly, we com- field, and gut contents were flushed out via gastric pared the proportion of two observed body color lavage and identified as algae, macrophytes, fish, or patterns (olive or orange/gold) between sexes with a invertebrates.