Evaluation of a Stable Isotope Labeling Technique for Mass-Marking Fin Rays of Age-0 Lake Sturgeon

The effectiveness of marking age-0 lake sturgeon, Acipenser fulvescens Rafinesque, pectoral fin rays with a stable strontium isotope was evaluated. Age-0 lake sturgeon were reared in water spiked with 0 (control), 25, 50, or 100 μg L-1 86SrC03 for 10 and 24 d; fish from each treatment group were retained for up to 120 d post-labeling to assess mark retention. Enriched isotope marks imparted to fin rays were distinct from fin ray 88Sr/86Sr ratios of control fish immediately following marking, with the 100 μg L-1 86SrCO3 treatments consistently yielding the highest rate of marking success (83-92%). Lower marking success (25-69%) was observed with the 25 and 50 μg L-1 86SrCO3 treatments. Isotopic marks in fin rays were retained for 120 d post-labeling. Immersion marking of juvenile fish pectoral fin rays with distinct strontium isotope ratios is possible and does not require sacrificing fish to check for marks

Trace element and Stable Isotopic Signatures in Otoliths and Pectoral spines as Potential Indicators of Catfish Environmental History

Natural chemical markers in otoliths and fin rays have proven useful for retrospectively describing environmental history of fishes in a variety of environments. However, no studies have applied this technique to catfishes or evaluated catfish pectoral spine chemistry as a nonlethal alternative to otolith chemistry. We characterized relationships between water, otolith, and pectoral spine (articulating process) chemistry for channel catfish Ictalurus punctatus, flathead catfish Pylodictis olivaris, and blue catfish I. furcatus and determined the accuracy with which fish could be classified to their environment of capture using otolith and pectoral spine chemical signatures. Fish and water samples were collected from nine sites during 2009. Otolith, spine, and water samples were analyzed for Sr:Ca and Ba:Ca; otolith δ18O and δ13C and water δ18O were also measured. Water, otolith, and spine Sr:Ca were highly correlated, as were water and otolith δ18O. Relationships between water, otolith, and spine chemistry did not differ among species. Otolith Sr:Ca, δ18O, and δ13C and spine Sr:Ca differed among sites, reflecting geographic differences in water chemistry. Neither otolith nor spine Ba:Ca differed among sites despite inter-site differences in water Ba:Ca. Both otolith Sr:Ca, δ18O, and δ13C and fin spine Sr:Ca classified fish to their environment of capture with a high degree of accuracy, except in the middle and lower Mississippi River where many recent immigrants appeared to be present. Natural chemical signatures in otoliths or pectoral spines will likely be effective for reconstructing environmental history of catfishes when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for these species

Fin Ray Chemistry as a Potential Natural Tag for Smallmouth Bass in Northern Illinois Rivers

Natural chemical markers in otoliths and fin rays have proven useful for describing environmental history of fishes in a variety of environments. However, no studies have evaluated smallmouth bass (Micropterus dolomieu) pectoral fin ray chemistry as a non-lethal alternative to otolith chemistry. We evaluated the trace element composition of smallmouth bass fin rays collected from northern Illinois rivers and determined the accuracy with which fish could be classified to their environment of capture using pectoral fin ray strontium:calcium (Sr:Ca) and barium:calcium (Ba:Ca) ratios. Fish were collected from nine sites during summer 2008. Fin ray Sr:Ca differed among some sites, reflecting previously observed differences in water and otolith chemistry for other fish species. Fin ray Ba:Ca did not differ among sites. Classification accuracy for individual fish to location of capture based on fin ray Sr:Ca was relatively poor when data from all nine sites in different watersheds were included. However, individual fish captured from the upper Illinois River watershed were accurately assigned to the river in which they were collected when data were restricted to these sites. Natural chemical signatures in fin rays will likely be effective for reconstructing environmental history of smallmouth bass when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for this species

Reproductive Biology of Middle Mississippi River Shovelnose Sturgeon: Insights from Seasonal and Age Variation in Plasma Sex Steroid and Calcium Concentrations

Shovelnose sturgeon Scaphirhynchus platorynchus are endemic to the Mississippi River drainage and are commercially harvested for roe in several states. Status of shovelnose sturgeon populations throughout much of its range is unknown or declining; Mississippi River stocks are experiencing recruitment overfishing and may be at risk of collapse. Restoration of shovelnose sturgeon populations will require additional information on their reproductive biology, including age at maturity and reproductive status and cycles. The objectives of this study were to determine the effects of reproductive stage, fish age, and season on plasma 17-β estradiol (E2) and calcium (Ca2+) concentrations in female shovelnose sturgeon and plasma testosterone (T) concentrations in male shovelnose sturgeon from the middle Mississippi River (MMR). We also assessed the relationship between plasma vitellogenin (VTG) and Ca2+ concentrations for female shovelnose sturgeon. Plasma E2 and Ca2+ concentrations in females and T concentrations in males differed among reproductive stages, consistent with results of prior research on shovelnose sturgeon and other sturgeon species. VTG and Ca2+ concentrations were strongly correlated in female shovelnose sturgeon, indicating that Ca2+ can be used as a surrogate for VTG assays for identification of vitellogenic females, as has been shown for other sturgeon species. Age at maturity was estimated at 10 years for males and 9 years for females based on T and E2 profiles, consistent with other recent age at maturity estimates in the MMR and Wabash River determined by gonadal examination. Peaks in plasma sex steroid and Ca2+ concentrations during April and October possibly reflected the spring spawning season and provide additional evidence in support of recent documentation of fall spawning by shovelnose sturgeon in the MMR. Additional research is needed to elucidate fall spawning by shovelnose sturgeon in the MMR

Fatty Acid Profiles are Biomarkers of Fish Habitat Use in a River-Floodplain Ecosystem

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

Identification of Stocked Muskellunge and Potential for Distinguishing Hatchery-Origin and Wild Fish Using Pelvic Fin Ray Microchemistry

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 seven 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

High frequency sampling of the 1984 spring bloom within the mid-Atlantic Bight: Synoptic shipboard, aircraft, and in situ perspectives of the SEEP-I experiment

Moorings of current meters, thermistors, transmissometers, and fluorometers on the mid-Atlantic shelf, south of Long Island, suggest a cumulative seaward export of perhaps 0.35 g C/sq m/day between the 80 and 120 m isobaths during February-April 1984. Such a horizontal loss of algal carbon over the lower third of the water column would be 23 to 78% of the March-April 1984 primary production. This physical carbon loss is similar to daily grazing losses from zooplankton of 32-40% of the algal fixation of carbon. Metabolic demands of the benthos could be met by just the estimated fecal pellet flux, without direct consumption of algal carbon, while bacterioplankton needs could be served by excretory release of dissolved organic matter during photosynthesis. Sediment traps tethered 10 m off the bottom at the 120 m isobath and 50 m above the 500 m isobath caught as much as 0.16 to 0.26 g C /sq m/day during March-April 1984, in reasonable agreement with the flux estimated from the other moored instruments

Early generation hybrids may drive range expansion of two invasive fishes DataSet

Introgressive hybridization between two invasive species has the potential to contribute to their invasion success and provide genetic resiliency to rapidly adapt to new environments. Additionally, differences in the behaviour of hybrids may lead to deleterious ecosystem effects that compound any negative impacts of the invading parental species. Invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) exhibit introgressive hybridization which could influence their invasion ecology. In order to investigate the role hybrids may have in the invasion ecology of bigheaded carps, [CAA1] we examined the distribution, movements, and environmental cues for movement of two invasive fishes (bighead carp, silver carp) and their hybrids in the Illinois River (USA). Early generation hybrids (e.g., F1,F2, and first generation backcross individuals) composed a greater proportion of the population at the invasion front where abundances of bigheaded carp were low. A greater proportion of early hybrids passed through dams upstream towards the invasion front than did other hybrids and parental species. The movements and environmental cues for movement of late-generation backcrosses (more genetically similar to parental genotype) were not different from the parental species with which they shared the most alleles. Although the direction of the relationship between movement and environment was sometimes different for the parental species and associated advanced generation hybrids, these results indicate that management for parental species will also influence most hybrids. Although early generation hybrids are rare, our results indicate they may disperse towards low-density population zones (i.e., invasion fronts) or are produced at greater frequency in low density areas. These rare hybrids have the potential to produce a variety of unique genetic combinations which could result in more rapid adaptation of a non-native population to their invaded range potentially facilitating the establishment of invasive species

Contrasting Population Characteristics of Yellow Bass (Morone mississippiensis) in Two Southern Illinois Reservoirs

We investigated two southern Illinois reservoirs 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 these 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 from future studies to elucidate factors influencing population dynamics of this species

Establishment of invasive Black Carp (\u3ci\u3eMylopharyngodon piceus\u3c/i\u3e) in the Mississippi River basin: identifying sources and year classes contributing to recruitment

Black Carp (Mylopharyngodon piceus) was imported to the USA to control aquaculture pond snails. This species has escaped captivity and occurs in parts of the Mississippi River, several tributaries, and floodplain lakes, which is concerning due to potential competition with native fishes and predation on native mussels, many of which are imperiled. However, Black Carp captures have primarily been incidental by commercial fishers, and evidence of reproduction in the wild is limited. The objectives of this study were to assess relative abundance of aquaculture- origin and wild Black Carp using ploidy and otolith stable isotope analysis, identify spatial extent of natural reproduction using otolith microchemistry, assess age distributions of wild and aquaculturesource Black Carp to infer years in which natural reproduction occurred and timing of aquaculture escapement or introductions, and estimate size and age at maturation to assess whether recruitment to adulthood has occurred. Results revealed that Black Carp are established in parts of the Mississippi River basin based on findings that: (1) non-captive Black Carp primarily consist of fertile, naturally-reproduced fish, (2) reproduction has occurred in several rivers, (3) multiple year classes of wild fish are present, and (4) wild fish have recruited to adulthood. Multiple introductions or escapements of aquaculture-source fish into the wild, including both fertile and functionally sterile individuals, were also inferred. Individual growth appears to be rapid, although considerable variation was observed among fish. Additional study is suggested to refine understanding of where and when Black Carp reproduction is occurring in the Mississippi River basin