Environmental Influences on the Growth of Inland Cisco Populations in Three Minnesota Sentinel Lakes

Author

Edward Carlson

Date of Award

12-2022

Document Type

Thesis

Department

Biology

First Advisor

Andrew Hafs

Abstract

Cisco Coregonus artedi are a pelagic cold-water fish that are widely distributed throughout many inland lakes across the northern Midwest and play an important role as forage for large piscivores. Inland Cisco populations have been observed to vary in their overall size and recruitment potential based on the system in which they are found. Cisco are sensitive to oxythermal stress and with climate change, land use, and invasive species effects becoming more prevalent in Minnesota, aspects of lake ecosystems are changing, ultimately making Cisco more susceptible to these stressors. To investigate how different factors were affecting the population dynamics of inland Cisco, three lakes with a range of size structure and densities were selected within Minnesota's northern lakes and forests and north central hardwoods ecoregions. Targeted, standardized, annual pelagic fish sampling was conducted from 2013-2019 using a combination of hydroacoustic sonar and vertical gillnets. Fish sampled in vertical gillnets were measured, weighed, and used to aid hydroacoustic estimates for Cisco abundance and biomass. In addition, metrics that describe the pelagic oxythermal habitat, food availability, and fish density were collected to understand how different environmental factors were influencing inland Cisco populations. A total of 16 linear regression and mixed effect models were developed for two selected response variables: upper 95th % total length (mm) and standardized age-0 density (no • ha-m®). Cyclopoid copeopod densities explained the most variability in the observed size differences found in Cisco (t = 4.05, var = 2796) while Cisco biomass best explained the variability amongst the age-O density response variable (p < 0.01. R?= 0.41). Additionally, the number of growing degree days at dissolved oxygen of 3.0 mg/L explained variability in both selected response variables (t = 2.36, var = 3632; p = 0.022, R2= 0.29). The results from this study document the importance of zooplankton prey and oxythermal habitat on Cisco and therefore provide fisheries managers with further knowledge to help closely monitor these populations.

Recommended Citation

Carlson, Edward, "Environmental Influences on the Growth of Inland Cisco Populations in Three Minnesota Sentinel Lakes" (2022). Biology Graduate Theses. 5.
https://pines.bemidjistate.edu/thesis-biol/5