Reciprocal predation promotes co-existence of native and non-native fishes: A Case study from the Mojave Desert.

Authors: Sujan M. Henkanaththegedara, Justin D. Fisher, Craig A. Stockwell

Year: 2009 (xli)

Abstract

Ecological interactions between non-native and native species have been of long-standing interest to evolutionary ecologists and conservation biologists. In many cases, non-native species prey upon native biota, however this observation is based on limited experimental data. We conducted controlled mesocosm experiments to assess the effects of invasive western mosquitofish Gambusia affinis on endangered Mohave tui chub Siphateles bicolor mohavensis reproduction and recruitment. We exposed 30 mesocosms to three treatments 1) Mohave tui chub only, 2) mosquitofish only and 3) Mohave tui chub and mosquitofish. The number of tui chub larvae produced in the mesocosms with mosquitofish (5.40 +/-3.44) was significantly lower than larval production in the control mesocosms (33.80 +/-7.58) (N=10; t=3.41; P>0.05). Conversely, Mohave tui chub had a significant negative impact on mosquitofish recruitment (N=10; t=2.95; P>0.05). Furthermore, adult mosquitofish had exceptionally low survival (24 +/- 5.3 %) in the presence of tui chubs compared to mosquitofish maintained in allopatry (98 +/- 0.82%) (N=10; t=13.90; P>0.001). Mosquitofish were experimentally shown to impact and suppress fish populations by consuming eggs and newly developed larvae. By contrast, predation by Mohave tui chub targets adult moquitofish, and thus may limit mosquitofish population growth which may in turn facilitate co-existence of these two species. Overall, these results suggest a reciprocal predation between two species which may explain the long term co-existence of both species in Lake Tuendae and China Lake habitats.