Date of Award
8-1-2024
Degree Name
Master of Science
Department
Zoology
First Advisor
Whitledge, Gregory
Abstract
Large rivers in the United States support popular recreational and commercial fisheries despite being among the most heavily anthropogenically modified habitats due to the construction of dams and levees, agricultural and industrial pollution, and channel modification, all of which can disrupt aquatic ecosystem function and affect fish community composition and abundance. However, despite their relative importance, riverine fisheries research tends to lag behind that of lakes and reservoirs due to the complexity of habitats and difficulties in reliably sampling dynamic waterbodies. Many fisheries biologists, researchers, and managers have implemented long-term resource monitoring programs on large rivers to collect and aggregate data on fish assemblage, population demographics, and vital rates. Nonetheless, much is still unknown about many riverine sport and non-game fish populations and how the design and implementation of these monitoring programs affects the data collected. This study aimed to fill the knowledge gap around Smithland Pool, Ohio River Black Crappie (Pomoxis nigromaculatus) and White Crappie (Pomoxis annularis) populations, as well as use fish community data from the random site selection long-term electrofishing program (LTEF) in the Smithland Pool Ohio River and fixed site IDNR annual community sampling programs in the mainstem Smithland Pool (OHR) and Illinois tributaries (OHT) from 2012-2021 to compare measures of fish assemblage structure and relative abundance and size for select sportfish populations between concurrent fixed and random site selection sampling programs in Smithland Pool, with broader implications of the relative strengths of different site selection methods in the implementation of long-term large river fish monitoring programs. Crappie are infrequently encountered in the mainstem Smithland Pool and so were sampled in the lower reaches of seven tributaries in the fall and spring of 2020 and 2021. IDNR provided additional specimens through their annual fall tributary fish community monitoring efforts. Crappies were aged using whole sagittal otoliths and population demographics and vital rates were calculated for each species. Year-class strength was represented by catch curve residuals and correlational relationships with a variety of environmental factors were established. LASSO regression models were also used to eliminate unimportant variables. Smithland Pool tributary Black Crappie and White Crappie size structure, condition, growth rates, and mortality rates were consistent with other regional fisheries. White Crappie exhibited relatively lower mortality rates, faster growth rates, and a higher proportion of larger fish in the population, though 1.7x more Black Crappie were captured than White Crappie. Strong Black Crappie year-classes were positively associated with post-spawn (June-September) Ohio River discharge while strong White Crappie year-classes were positively associated with fall (October-December) air temperature, a proxy for water temperature. The findings of this study suggest that Smithland Pool Ohio River tributary crappie population structure and vital rates are such that they can support current levels of angler harvest and highlight the differential effects of environmental variables on either crappie species’ reproductive success. Rates of Smithland Pool tributary crappie fishing mortality are currently unknown and verification of vital rates, size structure, and environmental variable-recruitment relationships is needed to ensure proper management of these species into the future. ANOSIM and NMDS analysis indicated clear significant differences between fish assemblages observed through different programs, largely driven by centrarchid species, among others, who associated more with relatively structure rich tributary and fixed site mainstem habitats. Differences in CPUE and size structure of Bluegill (Lepomis macrochirus), Largemouth Bass (Micropterus salmoides), Longear Sunfish (Lepomis megalotis), Redear Sunfish (Lepomis microlophus), and Spotted Bass (Micropterus punctulatus) between programs were inconsistent among species but generally, fixed site tributary sampling caught experienced the highest CPUE, followed by fixed site river sampling and finally random site mainstem sampling. Observed size structure was most similar between fixed and random site river sampling programs, while fixed site tributary sampling generally yielded the smallest size structure, suggesting differential habitat use by fishes of different sizes/ages. These results help to inform the effects of site selection protocols and sampling location on data collected through long-term large river monitoring programs, provide guidelines regarding proper application of data from such programs, as well identify complementary relationships between concurrently implemented sampling designs.
Access
This thesis is Open Access and may be downloaded by anyone.