Consistently High Trophic Overlap between Invasive White Perch and Native Black Crappies in Southeastern Reservoirs

Abstract The detrimental impacts of invasive species often occur through deleterious trophic interactions (e.g., competition) with native species. However, the potential for competitive interactions between species may vary among systems, among seasons, or throughout the species’ ontogeny, requiring a thorough examination of trophic niches to determine whether overlap exists and to elucidate the likelihood of competition. The Black Crappie Pomoxis nigromaculatus is a popular game fish species across the United States, but recent invasions of White Perch Morone americana , which exploit a similar trophic niche, into southern reservoirs represent a major concern for the continued sustainability of Black Crappie fisheries. We examined the trophic niches of these species throughout their ontogeny in two North Carolina reservoirs during 2009 and 2010 using a combination of diet content and stable isotope analyses. Extensive and significant similarities in diet composition and isotopic niche overlap existed between Black Crappies and White Perch throughout their ontogeny and across seasons in both systems. Overlap was particularly high between smaller (<200‐mm), invertivorous Black Crappies and all sizes of White Perch. This overlap suggests that if invertebrate resources become limited, competition during the juvenile stage could reduce growth rates and survival of young Black Crappies. By evaluating variation in the trophic niches of each species among seasons, body sizes, and reservoirs, we conclude that the potential for competitive interactions between White Perch and Black Crappie is high in southern reservoirs. Management options to either reduce White Perch abundance or prevent their spread to novel habitats may be necessary to sustain native and supplemented Black Crappie populations that are potentially vulnerable to White Perch invasions.