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The Impacts of Recently Established Fish Populations on Zooplankton Communities in a Desert Spring, and Potential Conflicts in Setting Conservation Goals
Diversity (2015)
  • Sujan Henkanaththegedara, Longwood University
  • Justin D. L. Fisher, North Dakota State University
  • Daniel C. McEwen, Minnesota State University Moorhead
  • Craig A. Stockwell, North Dakota State University
Desert springs, which harbor diverse and endemic invertebrate assemblages, are
often used as refuge habitats for protected fish species. Additionally, many of these springs
have been colonized by invasive fish species. However, the potential impacts of recently
established fish populations on invertebrate communities in desert springs have been
relatively unexplored. We conducted a mesocosm experiment to assess the impact of both
protected and invasive fish on community structure of spring-dwelling invertebrates
focusing on zooplankton. Experimental populations of spring zooplankton communities
were established and randomly assigned to one of three treatments, (1) invasive western
mosquitofish (Gambusia affinis); (2) endangered Mohave tui chub (Siphateles bicolor
mohavensis); and (3) fishless control. Final populations of zooplankton and fish were
sampled, sorted, identified and counted. The treatment differences of zooplankton communities
were analyzed by comparing the densities of six major zooplankton taxa. Further, we
performed nonmetric multidimensional scaling (NMDS) to visualize the patterns of zooplankton community assemblages. Four zooplankton taxa, crustacean nauplii, cladocera,
calanoid and cyclopoid copepods had significantly lower densities in fish treatments
compared to fishless control. Overall, invasive mosquitofish caused a 78.8% reduction in
zooplankton density, while Mohave tui chub caused a 65.1% reduction. Both protected and
invasive fish had similar effects on zooplankton except for cladocerans where tui chub
caused a 60% reduction in density, whereas mosquitofish virtually eliminated cladocerans.
The presence of fish also had a significant effect on zooplankton community structure due
to population declines and local extirpations presumably due to fish predation. This work
shows that conservation-translocations undertaken to conserve protected fish species may
impact spring-dwelling invertebrate communities, and such impacts are similar to impacts
due to colonization by invasive fish species.
  • desert springs; spring invertebrates; spring zooplankton; protected species; endangered species; invasive species; alien species
Publication Date
January 9, 2015
Citation Information
Sujan Henkanaththegedara, Justin D. L. Fisher, Daniel C. McEwen and Craig A. Stockwell. "The Impacts of Recently Established Fish Populations on Zooplankton Communities in a Desert Spring, and Potential Conflicts in Setting Conservation Goals" Diversity Vol. 7 (2015) p. 3 - 15 ISSN: 1424-2818
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