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Sauger Sander canadensis are a popular sport fish native to large turbid midwestern rivers and are in decline across much of their range due to habitat loss and exploitation. Specifically, within the lower Kaskaskia and Ohio rivers, Sauger are managed under different harvest regulations and a knowledge gap exists regarding the current status of both populations as well as the effects of the harvest regulations on the size and age structures of both populations. We collected Sauger by nighttime boat electrofishing during early winter 2014–2016 and used otoliths to age all fish. Sauger stocks in both rivers exhibited fast growth rates and high annual mortality rates. Yield-per-recruit modeling indicated that the current 356-mm minimum size limit for Sauger in the Kaskaskia River is sufficient to prevent growth overfishing and likely explains the consistently larger size structure (greater proportion of fish ≥356-mm total length) of Sauger sampled from the Kaskaskia River compared with the Ohio River. Modeling suggested that growth and recruitment overfishing of Sauger are likely occurring in the Ohio River with no minimum length limit based on available exploitation estimates for Sauger in the lower Ohio River. Implementing a 356-mm minimum length limit for Sauger in the lower Ohio River is predicted to prevent growth and recruitment overfishing based on available exploitation rate estimates and would be consistent with the statewide minimum length limit for Sauger in Illinois and minimum length limits on two major tributaries (Tennessee and Cumberland rivers downstream of Kentucky and Barkley lakes, respectively).

Summary The Chicago Area Waterways System (CAWS), an artificial connection between Lake Michigan (LMI) and the Illinois River watershed, has served as a conduit for invasive species and is a potential pathway for viral hemorrhagic septicemia (VHS) to spread from the Great Lakes into the Illinois River drainage. Although some fishes are known to have moved from LMI into the Illinois River via the CAWS, the rate of fish passage from the lake into the CAWS is unclear. Stable carbon isotopic signatures (δ13C) in otoliths differ between lake- and CAWS-resident fish and were used as a natural tag to identify individuals that may have moved into the CAWS from LMI. The objectives of this study were to (i) estimate relative frequency of individuals with otolith δ13C indicative of prior residency in LMI among small-bodied (

We investigated the environmental life history of widely distributed threatened and endangered sturgeons in large rivers of the central United States that experience different regulatory regimes and management priorities. Using microchemistry techniques, our goal was to assess how to improve species conservation by dampening the incongruity that often occurs between management and species’ ecological requirements, particularly at large spatial scales. Pallid sturgeon (Scaphirhynchus albus), shovelnose sturgeon (Scaphirhynchus platorynchus), and their hybrids were analyzed for88Sr and44Ca and related to a geographically relevant range of Sr:Ca values for the Missouri and Mississippi rivers to quantify large-scale environmental history. We found natal origin of 81% of all wild sturgeon collected was the lower Missouri River. Pallid and hybrid sturgeon used the middle and upper Mississippi rivers more frequently as they aged, whereas shovelnose sturgeon occupied the lower Missouri River more often throughout life. Our results highlight a mismatch between conservation boundaries and sturgeon river use. Managers should consider expanding current protections for pallid sturgeon to include the unprotected sections of the Mississippi River and that research and conservation actions consider the importance of Mississippi River habitats to Scaphirhynchus sturgeon throughout their life history. Our findings have implications for conserving wide-ranging riverine species at large spatial scales using the framework described here.

Insight into environments that contribute recruits to adult fish stocks in riverine systems is vital for effective population management and conservation. Catfishes are an important recreational species in the Mississippi River and are commercially harvested. However, contributions of main channel and tributary habitats to catfish recruitment in large rivers are unknown. Stable isotope and trace elemental signatures in otoliths are useful for determining environmental history of fishes in a variety of aquatic systems, including the Mississippi River. The objectives of this study were to identify the principal natal environments of channel catfish Ictalurus punctatus and blue catfish Ictalurus furcatus in the Middle Mississippi River (MMR) using otolith stable oxygen isotopic composition (δ18O) and strontium : calcium ratios (Sr : Ca). Catfishes were sampled during July–October 2013–2014, and lapilli otoliths were analysed for δ18O and Sr : Ca. Water samples from the MMR and tributaries were collected seasonally from 2006 to 2014 to characterize site-specific signatures. Persistent differences in water δ18O and Sr : Ca among the MMR and tributaries (including the upper Mississippi, Illinois, and Missouri rivers as well as smaller tributaries) were evident, enabling identification of natal environment for individual fish. Blue and channel catfish stocks in the MMR were primarily recruited from the large rivers (Missouri and Mississippi) in our study area, with minimal contributions from smaller tributaries. Recruitment and year class strength investigations and efforts to enhance spawning and nursery habitats should be focused on in large rivers with less emphasis on smaller tributaries. Copyright © 2016 John Wiley & Sons, Ltd.

Fatty acid (FA) analyses of fish tissues offer the potential to gain new knowledge of habitat- or forage-specific energy inputs to fishes in river-floodplain ecosystems, although limited information exists regarding among-habitat differences in FA biomarkers. The goal of this study was to determine if differences in fish FA profiles among main channel and connected and disconnected floodplain lakes exist in large river-floodplain systems. Bluegill Lepomis macrochirus FA profiles were generated to assess differences among two reaches of the Illinois River, USA, and its connected and disconnected floodplain lakes and determine whether FA signatures could be used to reclassify fish to their source habitat. Bluegill FA profiles differed among habitats and river reaches, including differences in levels of individual FAs (e.g., 18:2n−6, an indicator of allochthonous inputs, was higher among main channel fish) and FA groupings (e.g., n−3:n−6 FA ratio, an indicator of aquatic primary productivity, was higher among floodplain lake fish), which enabled >87.5% reclassification accuracy of fish to their source environment. We demonstrated that bluegill FA profiles differed among reaches and laterally among river channel and floodplain habitats, suggesting that FA profiles can be used to infer recent habitat use and habitat-specific foraging of fishes in large river-floodplain ecosystems.

An evaluation of Zequanox ® (a naturally derived biopesticide that is non-toxic to humans and other aquatic life and selectively kills dreissenid mussels) for controlling zebra mussel infestations in shallow-water habitats in lakes was conducted at Deep Quarry Lake in DuPage County, Illinois during summer 2012 and 2013. During the 2012 trial, three sets of paired 24-m² treatment and control sites were established within the lake, while a single 324-m² treatment site was established for the 2013 trial. Zequanox was applied to treatment plots, contained using PVC barrier curtains, and barriers were removed during the morning following application. Zebra mussel mortality and size distributions on natural substrates were assessed one day and one week post-treatment for 2012 trials and one day and two weeks posttreatment for 2013 trials; percent mortality of zebra mussels in mesh containers in treatment and control sites was also monitored up to 14 days and 48 days post-treatment in 2012 and 2013, respectively. Several water quality parameters were measured in control and treatment plots before and during application and up to 14 d post-treatment. Mean percent mortality for adult zebra mussels on natural and artificial substrates in treatment locations 7–48 d following Zequanox application ranged from 92–98% during both years, while mortality was consistently ≤10% in control locations. Mean percent mortality ranged from 15–76% in locations > 5 m from and in water shallower than Zequanox application points (

The effectiveness of pelvic fin ray microchemistry of muskellunge, Esox masquinongy Mitchill, to identify stocked individuals along with the potential to identify naturally reproduced fish were evaluated. Fish and water samples were obtained from one hatchery and seven lakes with natural differences in water Sr:Ca to determine whether location-specific environmental signatures were recorded in sectioned muskellunge pelvic fin rays, including fish of known environmental history. Water and fin ray Sr:Ca were strongly correlated. Six lakes in Illinois possessed Sr:Ca signatures that were distinct from the hatchery where muskellunge were raised, resulting in pronounced shifts in Sr:Ca across sectioned fin rays of stocked fish. Hatchery and lake-specific Sr:Ca signatures were stable across years. Sixteen of 19 individual fish known to have been stocked based on PIT tags implanted at stocking were correctly identified as hatchery-origin fish using fin ray core Sr:Ca. Results also indicated that the hatchery Sr:Ca signal can be retained for at least 7 years in fin rays of stocked fish. Fin ray microchemistry is a non-lethal approach for determining environmental history of muskellunge that could be used to assess movement patterns in lake and river systems and the degree to which muskellunge populations are supported by natural reproduction and stocking.

We evaluated the potential utility of pectoral fin rays as non-lethal aging structures for smallmouth bass (Micropterus dolomieu). We compared age estimates among three reading pairs and against sectioned sagittal otolith age estimates for precision. Reading pair bias was not detected, although the highest rates of age estimate agreement occurred between reading pairs with high and moderate aging experience. Precision of otolith and fin ray age estimates were equivalent based on between-structure comparisons of average percent error and coefficient of variation. However, fin rays underestimated fish age compared to otoliths for older fish, especially when aged by less-experienced readers. Pectoral fin rays may provide a non-lethal alternative to otoliths for aging smallmouth bass, particularly for younger fish (≤age 4) or when experienced readers conduct aging. Additional evaluations of fin rays as smallmouth bass aging structures are needed, including validation using known-age fish and documentation of ...

Mark–recapture studies require knowledge of tag retention rates specific to the tag types, fish species and size, and study duration. We determined the probability of tag loss for passive integrated transponder (PIT) tags implanted into dorsal musculature, T-bar anchor tags attached to dorsal pterygiophores, and both tags in relation to years posttagging for double-marked adult muskellunge Esox masquinongy over a 10-year period. We also used PIT tags as a benchmark to assess the interactive effects of fish length at tagging, sex, and years posttagging on T-bar anchor tag loss rates. Only five instances of PIT tag loss were identified; the calculated probability of a fish's losing its PIT tag was consistently less than 1.0% for up to 10 years posttagging. The probability of T-bar anchor tag loss by muskellunge was related to both the number of years posttagging and the total length (TL) of the fish at tagging. The T-bar anchor tag loss rate 1 year after tagging was 6.5%. Individuals of less than 7...

Summary Two southern Illinois reservoirs were investigated with contrasting size structures of yellow bass (Morone mississippiensis) to compare growth, mortality and recruitment patterns. Yellow bass were collected from Crab Orchard and Little Grassy lakes during April–May 2009 using AC electrofishing. Total length and weight were recorded and sagittal otoliths sectioned and aged by two readers. Increments between otolith annuli were measured and the Weisberg linear growth model was used to assess age and environmental (growth year) effects on individual growth for fish from the two lakes. Von Bertalanffy growth models indicated faster growth and a greater maximum total length for yellow bass in Little Grassy Lake. However, growth of fish in Little Grassy Lake nearly ceased after age 4. The Weisberg model indicated differences in individual growth rate between the two lakes that were consistent across years (age effects were significant, but growth year effects and the age-growth year interaction were not). Inter-lake differences in fish growth were present up to age 3. Recruitment was relatively stable in Crab Orchard, with year classes up to age 7 observed. Recruitment was more erratic in Little Grassy, with age 5 being the dominant year class and fish up to age 11 present. Differences in growth and recruitment patterns for yellow bass in the two lakes may be attributed to substantial inter-lake differences in turbidity, morphoedaphic index, or yellow bass density. Maximum age of yellow bass (age 11) was higher than previously reported for this species, likely due to the use of otoliths to age fish rather than scales. This study provides baseline information on age and growth, mortality, recruitment, and size structure of yellow bass that can be compared to data in future studies to elucidate factors influencing population dynamics of this species.