Date of Award

Summer 9-28-2017

Document Type

Thesis

Degree Name

Master of Science in Fisheries and Wildlife Science

Department

Biological Sciences

College

College of Natural & Health Sciences

Committee Chair

Dr. Charles J. Gagen

Second Committee Member

Dr. Joseph N. Stoeckel

Third Committee Member

Jeffrey W. Quinn

Dean of Graduate College

Dr. Mary B. Gunter

Abstract

The Neosho Smallmouth Bass Micropterus dolomieu velox is a top predator and popular sportfish in Arkansas’ Boston Mountain streams. In this ecoregion, Smallmouth Bass are common in headwater streams that are prone to drying during the summer months. My objectives were to characterize longitudinal movements of adult Smallmouth Bass and to determine the timing of spawning events along with associated environmental variables during the likely spawning months of June and July. Thirty Smallmouth Bass were captured and implanted with radio transmitters in March, and tracked weekly in the Middle Fork of Illinois Bayou until August 2016. Age-0 Smallmouth Bass were collected using electrofishing from May through August 2016, and otoliths were used to back-calculate spawn date. Stream discharge and water temperature were measured during the tracking period. The proportion of individuals that moved over 100 m per week was at its highest during April and May, when about 50% of individuals moved over 100 m per week, prior to the presumptive spawning peak and this proportion gradually declined to 13% through July and August. I attributed the reduced movement to reduced streamflow (e.g. < 400 L/s) which tended to restrict fish to remaining isolated pools. Net distances did not vary before, during, or after spawning (P>0.05). Cumulative movements were highest before spawning and decreased significantly once spawning began (F = 3.97, df = 2,271, P≤0.01). Minimum daily water temperature was inversely correlated to movement (P<0.01, R 2=0.61). Peak spawning in this system occurred during 17 days from May 25 th to June 10 th indicating that individuals that successfully recruited to a catchable size (25 mm) were spawned over a short time-period. Age-0 Spotted Bass M. punctulatus spawned during the range of Smallmouth Bass spawning dates, and were collected incidentally along with age-0 Smallmouth Bass indicating a potential for introgression. The majority of Smallmouth Bass spawning occurred on the falling limbs of hydrographs and at temperatures between 17℃ and 25℃. Median daily water temperature (R 2=0.51, P<0.01) was the best temperature variable and minimum log10 discharge (R 2=0.37, P<0.05) was the best discharge variable for predicting successful Smallmouth Bass spawning in the Illinois Bayou during the summer of 2016. The small movements observed in the pre-spawning period may have been fish searching for spawning sites and establishing dominance at optimal sites. Neosho Smallmouth Bass in this study had a short spawning duration compared to what is known about the northern sub-species. Global climate change, competition with Spotted Bass for spawning habitat, and introgression could lead to declines in Neosho Smallmouth Bass.

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