Round goby effects on growth and survivorship of young-of-the-year smallmouth bass.
Winslow, Christopher*,1, Miner, Jeffrey1, Wiegmann, Daniel1, 1 Bowling Green State University, Bowling Green, OH
ABSTRACT- In fishes, body size can vary by five orders of magnitude with concomitant ontogentic niche and habitat shifts that can complicate predictions of invading species effects on indigenous organisms. One of the highly successfully invading species to the Great Lakes is the Ponto-Caspian round goby (Neogobious melanstomus, RG), now occupying most of the cobble littoral in the southern Great Lakes. Although benthic molluscivore specialist, this species has been shown to have both negative (egg-predator) and positive (as prey) effects of various life stages of smallmouth bass (Micropterus dolomieui, SMB), an species that uses this same habitat throughout its ontogeny. Given the life stage requirements of young-of-the-year smallmouth bass, we predicted that this could be a bottleneck life stage in which round gobies could have a strong negative effect via direct competition for space and prey resources and a indirect effect on predation risk via behavioral exclusion from refuges. To quantify effects on growth of young SMB we conducted a mesocosm experiment with varying densities of young SMB and RG. Additonally, alaboratory behavior experiment was designed to determine if RG exclude young SMB from potential refuge through aggressive interactions. This second experiment specifically examined habitat use and possible alterations to SMB behavior - can eviction from refugia increase exposure to predators? Both experiments included measures of intraspecific competition among SMB and interspecific competition between SMB and RG. Results suggest that intraspecific and interspecific competition for growth are significant (ANOVA; P<0.0001 - Bonferroni; P<0.05 versus with no competitors) and similar in magnitude; however, because RG are found at much higher density (up to 15 RG.m-2) than SMB conspecifics, negative RG effects on this lifestage of SMB appear substantial . Additionally, behavioral modifications and analysis of diet suggest that competitive interference rather than exploitative mechanisms is the primary operating mechanism for this interaction.
Key words: invasives, competition, Lake Erie
All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.