Age-Length Analysis of Northern Pike (Esox lucius) and Largemouth Bass (Micropterus salmoides) for Saint John’s University Campus Lakes Compared to Higher Exploitation Lakes

Abstract

A length-at-age analysis was conducted for Northern Pike (Esox lucius) and Largemouth Bass (Micropterus salmoides) on Saint John’s University campus lakes in Collegeville, MN to determine if growth differences exist when compared to higher exploitation Minnesota lakes. Anal fin rays were collected from Northern Pike on Stumpf Lake while otoliths were collected from Largemouth Bass on Lake Sagatagan.  Both samples were prepared and analyzed by locating the focus and enumerating annuli. The length-at-age data collected was compared to other Minnesota lake length-at-age data for the respective species and showed quicker maturation for the species on higher exploitation lakes. It is likely that low exploitation on campus lakes leads to density-dependent declines in growth due to increased intraspecific competition. Additionally, fish on high exploitation lakes show quicker maturation to fill available niches. Von-Bertalanffy fitted growth curves were applied to the averaged data and R-Squared values for both Largemouth Bass and Northern Pike were high (>0.9). Provided length, our growth models are useful for predicting the age of both Northern Pike and Largemouth Bass on their respective campus lakes. The relatively pristine (few aquatic invasive spp. and runoff) St. John’s campus lakes show an interesting dynamic where fish experience slower growth, but on average are older than comparable lakes with higher exploitation rates.