Potential for a Multi-Species Refuge: Investigating Competition Between Historically Co-Occurring Cyprinids

Authors: Christi Kruse, Jon Shurin, Jeff Holmquist, Natalie Jones, Steve Parmenter, Nick Buckmaster

Year: 2018

Abstract

In the Owens Valley, native fish conservation is limited by suitable habitat; open waters are invaded by non-native species and refuge habitats are scarce. We investigated the potential for success of a multi-species native fish refuge using a mesocosm experiment to assess interactions between Owens Speckled Dace, Rhinichthys osculus ssp., and two size classes of hybridized Owens Tui Chub, Siphateles bicolor snyderi X S. obesa, (a surrogate for the listed subspecies). We tested the effects of interspecific interactions (e.g. competition and predation) on body condition, growth, and survivorship using five different combinations of species and sizes with a control treatment, each replicated 8 times. Mesocosms were inoculated with benthic substrate and invertebrates from the proposed refuge habitat. Two hypotheses were evaluated, (1) that the large size class of chub would prey upon dace, and (2) that interspecific competition between smaller size classes of fish would negatively affect body condition for both species. We did not find support for our first hypothesis, of predation by chub on dace, however, dace body condition was negatively affected by competition with small chub which partially supported our second hypothesis. Growth and body condition of large and small chubs were not affected by the presence of dace. Our results suggest that competition with small chub is more important than predation by large chub for dace growth and survival. Restoring sympatric populations of the two species may be possible if the habitat complexity allows for the rapid growth of chubs or if habitat complexity reduces the potential for interactions.