The Influence of Fish Presence on Amphibian Breeding Efforts

in a Central Illinois Field Experiment

J. Brian Towey

Department of Biological Sciences, Eastern Illinois University, Charleston, IL

Introduction

Introduced species often have negative impacts on populations of native taxa. The presence of introduced predatory fish may reduce breeding success of native amphibians. A management strategy of eliminating predatory fish from breeding ponds may promote native amphibian populations. This study examines amphibian communities at four neighboring woodland ponds in central Illinois before and after extermination of introduced fish populations from two of those ponds.

Figure 1. Ambystoma texanum (Smallmouth salamander) Vermilion County, IL. Photo by C.A. Phillips

Methods

Warbler Woods Nature Preserve is a recently established forest reserve managed by the Illinois Department of Natural Resources (IDNR). There are four neighboring ponds on the reserve which are all used by amphibian species as breeding sites. The ponds have been monitored since May 2000 using screen wire drift fences and pit trap arrays. Traps are located on both sides of the fence, spaced 7.5 m apart. I monitored traps every 2 to 3 days throughout the activity season of local amphibians. I toe-clipped all new animals to indicate the year of initial capture and released them on the opposite side of the fence.

Figure 2.  Screen wire drift fences.

Fish Removal

In December 2001, IDNR officials applied Rotenone^TM to ponds B and C to eliminate the fish species from those two ponds (Ameiurus melas from pond B and Lepomis machrochirus and L. cyanellus from pond C). The application appears to have been successful for the eradication of centrarchids in pond C. However, several live Ameiurus melas have been noted in pond B since application, though markedly fewer individuals than noted prior to Rotenone^TM application.

Figures 3 and 4.  RotenoneTM treated ponds.

Ponds

A - No history of inhabitation by fish. 

B - Contained introduced Black Bullhead Catfish (Ameiurus melas) until Rotenone^TM application in December 2001.

C - Contained introduced Bluegill and Green Sunfish (Lepomis machrochirus and L. cyanellus) until Rotenone^TM application in December 2001.

D - No history of inhabitation by fish. Ephemeral.

Results

Fisher’s exact tests by life history stage (Breeding adult / Neonate) and year of capture revealed differences in Ambystoma texanum numbers between treatment years at ponds A (P = 0.005), and C (P < 0.001) and in Bufo americanus numbers between treatment years at ponds A (P = 0.002), B (P < 0.001), and C (P < 0.001). Differences between treatment years in most other cases were not apparent due to low sample sizes.

	Figure 5.  Number of breeding season adults and emerging neonates.
	Figure 6.  Reproductive success as a proportion of emerging neonates to breeding adults.
	Figure 7.  Number of breeding season adults and emerging neonates.

Conclusions

Prior to removal, Ameiurus melas had a negative impact on Bufo reproduction.  Prior to removal, presence of centrarchid predators (Lepomis spp.) had a negative impact on Ambystoma reproduction.

Bufo americanus, Ambystoma texanum, and Rana sylvatica are capable of successfully hatching and completing metamorphosis in ponds treated with Rotenone^TM.  Amphibian species may benefit from eradication of fish from breeding ponds by pesticide application.

Acknowledgements

I would like to thank the following individuals and institutions for their technical, financial, and /or moral support and guidance during the course of this study:

Eastern Illinois University Biological Sciences Department: Dr. Stephen J. Mullin, Dr. Robert U. Fisher, Dr. Kipp Kruse, and Dr. Scott Meiners

Illinois Department of Natural Resources: Robert Szafoni and Michael Mountz

Aubrey Leffel, James Wachtel, Daphne Kampinga, Danial Cox

Erin Casey, C. Drew Foster, Jennifer M. Fish and Rev. Paul Hampton.