Lois Webster Fund Report – Plains Fish 2021

Lois Webster Fund Progress Report

Experimental test of condition-specific competition between native plains topminnow and non-native mosquitofish – July 2021 Progress Report

Yoichiro Kanno (Associate Professor) and Samuel Lewis (Graduate Research Assistant)
Department of Fish, Wildlife, and Conservation Biology
Colorado State University

The purpose of this report is to provide an update on a current project funded by the Audubon Society of Greater Denver. This summer we collected native Plains Topminnow from Pawnee National Grasslands (Fig 1a.) and invasive Mosquitofish from Running Deer Natural area (Fig 1b.) bringing them back to experimental stream units (Fig 1c.) constructed in the Anatomy Zoology building at Colorado State University.

Figure 1. (a) Collection of Plains Topminnow from Pawnee National Grasslands, (b) Mosquitofish collection from Running Deer Natural Area, (c) An experimental stream unit at Colorado State University

We have designed a 10-week experiment for data collection that is examining the effects of temperature and flow on mediating competition between non-native invasive Mosquitofish and native Plains Topminnow (Fig 2a.) The experiments involve three separate 3-week experiments where we count fish habitat preference to a high flow and low flow environment with each species separate (allopatric) and both species combined (sympatric). We have finished data collection for the Plains Topminnow in allopatry and the sympatric experiment with Mosquitofish and Plains Topminnow together. We have also collected data on fish behavioral interactions where we documented fin nipping and chasing among and between species housed at varying population densities (Fig 2b).

Figure 2 (a) Mosquitofish (left) and Plains Topminnow (right). Visual differences can be observed by looking for the light bar found along the dorsal side of the Plains Topminnow and the two light bars behind the head of the Mosquitofish. (b) Thomas Wallace (left) and Kelley Sinning (right), undergraduate research assistants performing counts of fish interactions.

We plan to finish the last two weeks of data collection for the allopatric Mosquitofish experiment and data collection will be completed on July 30. Analysis of the data will occur in late summer to early fall to identify how all factors measured including density, temperature, flow, total length, and species interactions play a role in meditating competition between invasive Mosquitofish and native plains species.