Match- mismatch Regulation for Bluegill and Yellow Perch Larvae and Their Prey in Sandhill Lakes

Food availability may regulate fish recruitment, both directly and indirectly. The availability of zooplankton, especially to newly hatched larvae, is thought to be crucial to their early growth and survival. We examined stomach contents of larval bluegill Lepomis macrochirus and yellow perch Perca flavescens in Pelican Lake and Cameron Lake, Nebraska, in 2004 and 2005. We also determined zooplankton availability and calculated prey selection using Chesson’s a. In addition, we investigated potential match–mismatch regulation of recruitment from 2004 to 2008. Bluegill positively selected copepod nauplii and Bosmina spp., and yellow perch often selected copepods. Abundant zooplankton populations were available for consumption. Matches of both larval bluegill and yellow perch abundance to zooplankton abundance were detected in all years; exact matches were common. Mismatches in predator and prey production were not observed. Predation by age-0 yellow perch on age-0 bluegill was not observed, even though yellow perch hatched 2 mo prior to bluegill. Given that zooplankton were abundant and well-timed to larval fish relative abundance over the time span of this study, the match–mismatch hypothesis alone may not fully account for observed recruitment variability in these populations. Environmental conditions may also affect recruitment and warrant further investigation

Match–Mismatch Regulation for Bluegill and Yellow Perch Larvae and Their Prey in Sandhill Lakes

Food availability may regulate fish recruitment, both directly and indirectly. The availability of zooplankton, especially to newly hatched larvae, is thought to be crucial to their early growth and survival. We examined stomach contents of larval bluegill Lepomis macrochirus and yellow perch Perca flavescens in Pelican Lake and Cameron Lake, Nebraska, in 2004 and 2005. We also determined zooplankton availability and calculated prey selection using Chesson’s a. In addition, we investigated potential match–mismatch regulation of recruitment from 2004 to 2008. Bluegill positively selected copepod nauplii and Bosmina spp., and yellow perch often selected copepods. Abundant zooplankton populations were available for consumption. Matches of both larval bluegill and yellow perch abundance to zooplankton abundance were detected in all years; exact matches were common. Mismatches in predator and prey production were not observed. Predation by age-0 yellow perch on age-0 bluegill was not observed, even though yellow perch hatched 2 mo prior to bluegill. Given that zooplankton were abundant and well-timed to larval fish relative abundance over the time span of this study, the match–mismatch hypothesis alone may not fully account for observed recruitment variability in these populations. Environmental conditions may also affect recruitment and warrant further investigation

Priority Effects Among Young-of-the-Year Fish: Reduced Growth of Bluegill Sunfish (Lepomis macrochirus) Caused by Yellow Perch (Perca flavescens)?

1. When available, Daphnia spp. are often preferred by age-0 yellow perch and bluegill sunfish because of energetic profitability. We hypothesised that predation by age-0 yellow perch could lead to a midsummer decline (MSD) of Daphnia spp. and that priority effects may favour yellow perch because they hatch before bluegill, allowing them to capitalise on Daphnia spp. prior to bluegill emergence. 2. Data were collected from 2004 to 2010 in Pelican Lake, Nebraska, U.S.A. The lake experienced a prolonged MSD in all but 1 year (2005), generally occurring within the first 2 weeks of June except in 2008 and 2010 when it occurred at the end of June. MSD timing is not solely related to seasonal patterns of age-0 yellow perch consumption. Nevertheless, when Daphnia spp. biomass was low during 2004 and 2006–2010 (\u3c4 mg wet weight L)1 ), predation by age-0 yellow perch seems to have suppressed Daphnia spp. biomass (i.e. \u3c1.0 mg wet weight L)1 ). The exception was 2005 when age-0 yellow perch were absent. 3. Growth of age-0 bluegill was significantly faster in 2005, when Daphnia spp. were available in greater densities (\u3e4 mg wet weight L)1 ) compared with the other years (\u3c0.2 mg wet weight L)1 ). 4. We conclude that age-0 yellow perch are capable of reducing Daphnia biomass prior to the arrival of age-0 bluegill, ultimately slowing bluegill growth. Thus, priority effects favour age-0 yellow perch when competing with age-0 bluegill for Daphnia. However, these effects may be minimised if there is a shorter time between hatching of the two species, higher Daphnia spp. densities or lower age-0 yellow perch densities

Overwinter Mortality of Sympatric Juvenile Bluegill and Yellow Perch in Mid-Temperate Sandhill lakes, Nebraska, U.S.A

Substantial mortality can occur in age-0 fish populations during their first year of life, especially in winter; this can potentially influence overall recruitment into the adult population. As such, we compared relative abundances between fall and spring catches of sympatric juvenile bluegill Lepomis macrochirus Rafinesque and yellow perch Perca flavescens (Mitchill) to evaluate the magnitude of overwinter mortality across locations (five lakes for two years) and through time (one lake for six years). In addition, we compared both quantile-quantile and increment plots, based on length-frequency histograms from fall- and spring-caught cohorts from 2004 to 2010, to determine if mortality was sizeselective while accounting for over winter growth. Bluegill relative abundances (as indexed by catch-per-unit-effort) significantly decreased from fall to spring, although size-selective mortality was not detected in 10 instances. Yellow perch relative abundances were similar from fall to spring in five Nebraska Sandhill lakes; however, size-selective mortality was detected, with size-selective over winter mortality of smaller individuals occurring in one of eight instances, whereas greater mortality in larger individuals occurred in two instances. Positive growth occurred in both species but was variable among lakes and appeared to be system-specific. In Nebraska Sandhill lakes, over winter mortality likely differs between these two species in its severity, size-selective effect, and scale (i.e., lake-specific vs. large-scale processes), and is likely influenced by combinations of these (and potentially other) factors

Exploring Spatial Distributions of Larval Yellow Perch Perca flavescens, Bluegill Lepomis macrochirus, and Their Prey in Relation to Wind.

The objectives of the present study were to determine if spatial differences existed between zooplankton, larval yellow perch Perca flavescens and bluegill Lepomis macrochirus (length, LT) in Pelican Lake (332 ha), NE, U.S.A. It was hypothesized that wind could act as a transport mechanism for larval fishes in this shallow lake, because strong winds are common at this geographic location. Potential spatial differences were explored, relating to zooplankton densities, size structure and densities of larval P. flavescens and L. macrochirus. Density differences (east v. west side of the lake) were detected for small- (two occasions), medium- (two occasions) and large-sized (one occasion) L. macrochirus larvae. No density differences were detected for small P. flavescens larvae; however, densities of medium- and large-sized P. flavescens were each higher on the west side of the lake on two occasions. There was no evidence that larval P. flavescens and L. macrochirus distributions were related to wind because they were not associated with large wind events. Likewise, large wind event days did not result in any detectable spatial differences of larval P. flavescens and L. macrochirus densities. There appeared to be no spatial mismatch between larval densities and associated prey in the years examined. Thus, wind was not apparently an influential mechanism for zooplankton and larval P. flavescens and L. macrochirus transport within Pelican Lake, and spatial differences in density may instead be related to vegetation and habitat complexities or spawning locations within this shallow lake

Overwinter Mortality of Sympatric Juvenile Bluegill and Yellow Perch in Mid-temperate Prairie Lakes

Substantial mortality can occur in age-0 fish populations during their first year of life, especially in winter; this can potentially influence overall recruitment into the adult population. As such, we compared relative abundances between fall and spring catches of sympatric juvenile bluegill Lepomis macrochirus Rafinesque and yellow perch Perca flavescens (Mitchill) to evaluate the magnitude of overwinter mortality across locations (five lakes for two years) and through time (one lake for six years). In addition, we compared both quantile-quantile and increment plots, based on length-frequency histograms from fall- and spring-caught cohorts from 2004 to 2010, to determine if mortality was sizeselective while accounting for over winter growth. Bluegill relative abundances (as indexed by catch-per-unit-effort) significantly decreased from fall to spring, although size-selective mortality was not detected in 10 instances. Yellow perch relative abundances were similar from fall to spring in five Nebraska Sandhill lakes; however, size-selective mortality was detected, with size-selective over winter mortality of smaller individuals occurring in one of eight instances, whereas greater mortality in larger individuals occurred in two instances. Positive growth occurred in both species but was variable among lakes and appeared to be system-specific. In Nebraska Sandhill lakes, over winter mortality likely differs between these two species in its severity, size-selective effect, and scale (i.e., lake-specific vs. large-scale processes), and is likely influenced by combinations of these (and potentially other) factors

Priority Effects Among Young-of-the-year Fish: Reduced Growth of Bluegill Sunfish (Lepomis macrochirus) Caused by Yellow Perch (Perca flavescens)?

1. When available, Daphnia spp. are often preferred by age-0 yellow perch and bluegill sunfish because of energetic profitability. We hypothesised that predation by age-0 yellow perch could lead to a midsummer decline (MSD) of Daphnia spp. and that priority effects may favour yellow perch because they hatch before bluegill, allowing them to capitalise on Daphnia spp. prior to bluegill emergence. 2. Data were collected from 2004 to 2010 in Pelican Lake, Nebraska, U.S.A. The lake experienced a prolonged MSD in all but 1 year (2005), generally occurring within the first 2 weeks of June except in 2008 and 2010 when it occurred at the end of June. MSD timing is not solely related to seasonal patterns of age-0 yellow perch consumption. Nevertheless, when Daphnia spp. biomass was low during 2004 and 2006–2010 (\u3c4 mg wet weight L)1), predation by age-0 yellow perch seems to have suppressed Daphnia spp. biomass (i.e. \u3c1.0 mg wet weight L)1). The exception was 2005 when age-0 yellow perch were absent. 3. Growth of age-0 bluegill was significantly faster in 2005, when Daphnia spp. were available in greater densities (\u3e4 mg wet weight L)1) compared with the other years (\u3c0.2 mg wet weight L)1). 4. We conclude that age-0 yellow perch are capable of reducing Daphnia biomass prior to the arrival of age-0 bluegill, ultimately slowing bluegill growth. Thus, priority effects favour age-0 yellow perch when competing with age-0 bluegill for Daphnia. However, these effects may be minimised if there is a shorter time between hatching of the two species, higher Daphnia spp. densities or lower age-0 yellow perch densities

Evidence for Bluegill Spawning Plasticity Obtained by Disentangling Complex Factors Related to Recruitment

Fishes can exhibit many forms of plasticity to maximize fitness. However, limited information exists on the ability of freshwater fish to adjust spawning behavior and characteristics (e.g., timing, duration, magnitude of spawning events) to minimize mortality of recruits and ultimately maximize fitness.Wewanted to test the life history hypothesis for bluegill (Lepomis macrochirus) (i.e., opportunistic strategy) utilizing existing literature and results from our study to further evaluate the potential for spawning plasticity in this species. Our objective was to identify bluegill recruitment bottlenecks (i.e., periods of high mortality) and factors associated with these events in a single lake during 7 consecutive years. Bluegills exhibited shorter spawning durations and fewer spawning pulses (i.e., peaks in larval production) compared with bluegill in previous studies. Late-hatched (compared with early-hatched) bluegills consistently contributed the most to the fall juvenile population; these recruitment patterns were primarily attributed to biotic drivers. Our study suggests that bluegill could exhibit spawning plasticity and extends our current understanding of adaptations that are potentially capable of increasing fitness for a freshwater fish species under a wide range of environmental conditions and uncertainty. Les poissons peuvent présenter différentes formes de plasticité leur permettant de maximiser leur aptitude. Peu de renseignements sont toutefois disponibles sur la capacité des poissons d\u27eau douce d\u27ajuster leur comportement de frai et les caractéristiques de ce dernier (p. ex. moment, durée, magnitude des évènements de frai) afin de minimiser la mortalité des recrues et, au final, maximiser leur aptitude. Nous voulions tester l\u27hypothèse du cycle biologique (c.-a` -d. stratégie opportuniste) pour le crapet arlequin (Lepomis macrochirus) a` la lumière d\u27études existantes et des résultats de notre étude pour évaluer plus en détail le potentiel de plasticité du frai chez cette espèce. L\u27objectif consistait a` cerner les goulots d\u27étranglement en ce qui concerne le recrutement de crapets arlequins (c.-a` -d. périodes de mortalité élevée) et les facteurs associés a` ces évènements dans un seul lac pendant 7 années consécutives. Comparativement aux études antérieures, les crapets arlequins présentaient des durées de frai plus courtes et moins de pointes de frai (ou de production de larves). La contribution a` la population juvénile automnale des crapets arlequins a` éclosion tardive était uniformément plus importante que celle des individus a` éclosion précoce, ces motifs de recrutement étant principalement attribuables a` des facteurs biotiques. L\u27étude donne a` penser que les crapets arlequins pourraient présenter une plasticité de frai et elle élargit la compréhension actuelle des adaptations pouvant potentiellement accroître l\u27aptitude d\u27une espèce de poissons dulcicoles pour un vaste éventail de conditions ambiantes et de niveaux d\u27incertitude

Common Carp Disrupt Ecosystem Structure and Function Through Middle-out Effects

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and nonunidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes

Collaborative International Research in Clinical and Longitudinal Experience Study in NMOSD.

Objective: To develop a resource of systematically collected, longitudinal clinical data and biospecimens for assisting in the investigation into neuromyelitis optica spectrum disorder (NMOSD) epidemiology, pathogenesis, and treatment. Methods: To illustrate its research-enabling purpose, epidemiologic patterns and disease phenotypes were assessed among enrolled subjects, including age at disease onset, annualized relapse rate (ARR), and time between the first and second attacks. Results: As of December 2017, the Collaborative International Research in Clinical and Longitudinal Experience Study (CIRCLES) had enrolled more than 1,000 participants, of whom 77.5% of the NMOSD cases and 71.7% of the controls continue in active follow-up. Consanguineous relatives of patients with NMOSD represented 43.6% of the control cohort. Of the 599 active cases with complete data, 84% were female, and 76% were anti-AQP4 seropositive. The majority were white/Caucasian (52.6%), whereas blacks/African Americans accounted for 23.5%, Hispanics/Latinos 12.4%, and Asians accounted for 9.0%. The median age at disease onset was 38.4 years, with a median ARR of 0.5. Seropositive cases were older at disease onset, more likely to be black/African American or Hispanic/Latino, and more likely to be female. Conclusions: Collectively, the CIRCLES experience to date demonstrates this study to be a useful and readily accessible resource to facilitate accelerating solutions for patients with NMOSD