Seasonality, demographics, and feeding ecology of mudpuppies (Necturus maculosus) in an urban lake

Author

Alicia M. Beattie, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2016

Degree Name

Master of Science

Department

Zoology

First Advisor

Whiles, Matt

Abstract

Mudpuppy (Necturus maculosus) populations are apparently declining throughout the Great Lakes region, yet little is known about their natural history. Using minnow traps, I captured 120 individual mudpuppies in Wolf Lake, Chicago, Illinois, and recaptured 34 of those individuals. Trapping periods of ≥ 3 consecutive nights occurred at intervals during January to May 2015, and October 2015 to March 2016. I also caught 25 mudpuppies using hand nets, including 1 recapture, during ice-free periods. Overall trapping success differed among trapping periods (p = 0.01). Relatively high trapping success during trapping periods from early November through early April suggests that there is a fairly large window in which mudpuppies may be successfully captured. The number of captures was negatively correlated with water temperature and was marginally significant (r = - 0.23, p = 0.09). However, daily capture success declined precipitously above 14.1° C, as indicated by a nonparametric two-dimensional Kolomogorov-Smirnov (2DKS) test (p < 0.001). Analyses of size classes indicated potential gear biases, with mudpuppies in traps (mean 26.9 ± 0.5 cm) larger than those caught using hand nets (mean 14.7 ± 0.8 cm, p < 0.0001). These results suggest multiple capture methods may be necessary to accurately assess demographic profiles and levels of recruitment. Stomach contents obtained through gastric lavage, a non-lethal stomach flushing method, included mollusks, leeches, insects, isopods, amphipods, crayfish, fish, a frog, and a juvenile mudpuppy. Invasive species were present in guts, including rusty crayfish (Orconectes rusticus), round gobies (Neogobius melanostomus), and zebra/quagga mussels (Dreissena spp.), suggesting that mudpuppies may forage on invasives in changing aquatic communities. Small juvenile mudpuppies (< 20 cm) consumed fewer fish and no crayfish, but more leeches and amphipods, than adult size classes (p < 0.0167). Nonmetric multidimensional scaling ordinations showed overall different communities of prey among size classes. ANOSIM results confirmed observed differences in composition among size classes (Global R = 0.253 for abundance, 0.258 for volume, and 0.267 for % volume of gut contents, p = 0.001 for all). These results suggest that mudpuppies in lake ecosystems occupy a broad niche that changes over their development.