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Title:Spatiotemporal trends and relationships in the abundance, growth, and condition of common nearshore fishes of southwest Lake Michigan
Author(s):Stacy, William L
Advisor(s):Czesny, Sergiusz J.; Wahl, David H.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Lake Michigan
Yellow Perch
Round Goby
Abstract:The Laurentian Great Lakes are large, diverse, and dynamic ecosystems whose biotic communities have undergone significant alteration over the last two centuries due to various effects of human habitation in the basin. Currently, the most noticeable effects are those wrought by numerous invasive species that have been brought to the region and established themselves in the food web. In southwestern Lake Michigan, the nearshore zone (<10m depth) is a diverse habitat with an array of benthic substrate types and thermal regimes. Common fish species in this region include a native omnivore, the yellow perch, which represents a valuable sport fishery; the round goby, an invasive omnivore; and the alewife, an invasive planktivore. The objective of this research was to explore spatiotemporal patterns in the abundance of fishes in the nearshore area of the Illinois waters of Lake Michigan as well as to assess the growth and condition of two of the most common species, the yellow perch and round goby. Finally, laboratory evaluations were done to improve upon otolith length back-calculation methods for future studies of round goby growth. Data were collected at three locations with contrasting habitat complexity. Age data were collected using otoliths of yellow perch and round goby, and Fulton’s condition factor was calculated for different age classes. Yellow perch relative abundance was most variable annually whereas round goby and alewife abundances were variable spatially. Age-0 yellow perch abundance also showed a negative relationship with round goby abundance, possibly indicating that the smaller yellow perch are avoiding high densities of the more aggressive round goby. Round goby abundance was the highest at the location with the prevalence of rocky substrate, likely due to their preference for spawning habitat. Alewife abundance increased significantly from south to north sites. For all yellow perch age classes studied, length-at-age varied annually while condition factor varied spatially. Yellow perch condition was the highest at the north location, where benthic substrate was dominated by sand and benthic invertebrate abundance was lowest. This unexpectedly high condition could be the result of reduced interaction with round goby enabling yellow perch more access to feeding on benthic prey. Round goby length-at-age was the greatest at the southern location, likely due to its warmer thermal regime. A laboratory experiment was undertaken to measure the accuracy of back-calculation models for round goby otoliths. Live round gobies were measured then marked with oxytetracycline to create a fluorescent ring on their otoliths and given an individual tag for later identification. After spending three months in the lab, fish were culled and otoliths were removed, viewed under an epifluorescent microscope and back-calculated using the inserted mark as an annulus. Back-calculated lengths were most accurate when using the Fraser-Lee method on measurements made to the post-rostrum radius. Accuracy was significantly related to growth rate and based on previous research it was concluded that unusually fast or slow growth can both cause a decoupling of otolith and somatic growth, increasing back-calculation error.
Issue Date:2016-12-06
Rights Information:Copyright 2016 William Stacy
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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