Notemigonus Research Articles

Behavioral response of juvenile silver and bighead carp to conspecific and heterospecific alarm cues

Predation is an important factor influencing the strength and success of a year class in many prey fishes. Many adaptations, including chemical cues, benefit shoaling groups by informing members of a possible impending predatory threat. Bighead (Hypophthalmichthys nobilis) and silver carps (Hypophthalmichthys molitrix) are widely dispersed invasive fishes that spend much of their first year at a size vulnerable to predation. The objective of this study was to evaluate the fright response of juvenile bighead and silver carps when exposed to alarm cues from conspecific and heterospecific fishes. Groups of carps were exposed to 5 mL of alarm cue from either bighead carp, silver carp, golden shiner (Notemigonus crysoleucas), or fathead minnow (Pimephales promelas). Behavior was recorded before and after the application of the treatment. Our results indicate that both species were unable to recognize chemical alarm cues from North American cypriniforms, yet both were able to recognize conspecific alarm cues. However, the two species of bigheaded carps respond to conspecific chemicals differently. Silver carp increase distance among individuals, whereas bighead carp reduce distance between individuals. Both show a reduction in activity after chemical application. Though both species recognize conspecific alarm cues, bighead carp exhibit similar fright patterns when exposed to alarm chemicals of silver carp, yet no behavioral responses were detected in silver carp when exposed to alarm chemicals of bighead carp. An understanding of fright response in bighead and silver carps aids understanding of predator interactions and ecological roles of these fishes, and can be utilized in population management applications.

Consensus of travel direction is achieved by simple copying, not voting, in free-ranging goats.

For group-living animals to remain cohesive they must agree on where to travel. Theoretical models predict shared group decisions should be favoured, and a number of empirical examples support this. However, the behavioural mechanisms that underpin shared decision-making are not fully understood. Groups may achieve consensus of direction by active communication of individual preferences (i.e. voting), or by responding to each other's orientation and movement (i.e. copying). For example, African buffalo (Syncerus caffer) are reported to use body orientation to vote and indicate their preferred direction to achieve a consensus on travel direction, while golden shiners (Notemigonus crysoleucas) achieve consensus of direction by responding to the movement cues of their neighbours. Here, we present a conceptual model (supported by agent-based simulations) that allows us to distinguish patterns of motion that represent voting or copying. We test our model predictions using high-resolution GPS and magnetometer data collected from a herd of free-ranging goats (Capra aegagrus hircus) in the Namib Desert, Namibia. We find that decisions concerning travel direction were more consistent with individuals copying one another's motion and find no evidence to support the use of voting with body orientation. Our findings highlight the role of simple behavioural rules for collective decision-making by animal groups.

Nature or Nurture: Can Prey-Based Diets Influence Species-Specific Physiological Performance Traits of Epidermal Lipid Content and Cutaneous Water Loss?

Epidermal lipids serve as the primary barrier to cutaneous water loss (CWL) and play a significant role in water conservation and homeostasis. Previous studies have shown the correlation between increased aridity of habitats and the amount of epidermal lipids among species. Generally, increased amounts of epidermal lipids lower skin permeability. Species-specific differences in CWL and prey preferences between two sympatric snake species, the Northern Cottonmouth (Agkistrodon piscivorus) and the Eastern Copperhead (Agkistrodon contortrix), motivated us to question if prey-base can result in these observed species-specific differences in CWL. We experimentally controlled the diets for a captive colony of Northern Cottonmouths (A. piscivorus) by feeding either fish (Notemigonus crysoleucas) or mice (Mus musculus) to investigate if diet can affect the quantity and quality of epidermal lipids and the rates of CWL. Snakes fed mice gained consistently more mass, but diet treatments did not affect growth rate. We found no significant differences in quantitative lipid content or rates of CWL between diet treatments. An analysis for qualitative lipid content using infrared spectrophotometry also showed no diet effect, thus suggesting that lipid content and CWL are strong species-specific physiological performance traits not influenced by recent dietary history. While there is some evidence that epidermal permeability may be variable under certain environmental conditions (e.g., humidity), our findings show that diet has no effect and that a shift in prey preference may not influence or enhance physiological performance for decreasing CWL.

Predator Attack Strategy and Prey Behaviour Drive Individual Predation Risk in Schooling Prey

Predation is one of the main drivers of animal grouping. However, predation risk is not shared equally within groups. Despite long-standing theoretical work and strong empirical insights, very little work has examined the real-time dynamics of predators attacking groups of prey nor quantified the features that predict prey predation risk and survival. Here we used high resolution tracking of Northern pike (Esox lucius) attacking large schools of prey (golden shiner fish, Notemigonus crysoleucas) to get a mechanistic quantification of predation at every stage of the attack. We found that pike tended to attack the groups head-on, but did so stealthily, often striking only when partly within the school. From the predator’s perspective, relative position to the prey was the most important feature, with shiners very close and directly in front of the pike being most at risk. From the prey’s perspective, we found that central individuals, with relatively low local neighbour density and alignment, face increased risk. While the majority of attacks were successful, escape was associated with individuals achieving high maximum movement speeds, relative to others. Our study highlights both predator attack strategy and prey behaviour are key factors underlying the predation risk of grouping prey, and our results contradict the long-held assertion arising from Hamilton’s “selfish herd” concept that central positions are safer. To ultimately understand the cost-benefits that underly the evolution of animal grouping it is thus key to consider the multifaceted, and dynamical, nature of predator-prey relationships.

Economic effects of predation by scaup on baitfish and sportfish farms

AbstractFish‐eating birds have been found to consume baitfish and sportfish raised on farms in the United States. Understanding the on‐farm economic effects of such wildlife conflicts is essential for wildlife management agencies to make informed decisions. Lesser scaup, while not widely considered a fish‐eating bird, will consume farmed fish. Baitfish and sportfish farms in Arkansas (the major baitfish and sportfish producing‐state in the U.S.) were surveyed to gather data on the cost of protecting farm crops from scaup. The values of lost sales revenue from the various species of baitfish and sportfish consumed by scaup were estimated based on a concomitant field study on the abundance, distribution, and dietary habits of scaup that visited Arkansas baitfish and sportfish farms during winters of 2016–2017 and 2017–2018. Economic effects were estimated for golden shiner, fathead minnow, sportfish, and goldfish farms. Total annual costs to scare birds from baitfish and sportfish farms were $622 ± 742 per ha. The greatest components of bird‐scaring costs were manpower (56%), truck usage (32%), levee upkeep for vehicle access to scare birds (9%), firearms and ammunition (2%), and pyrotechnic devices (1%). The combined annual economic losses, calculated as reduced revenue from fish losses to scaup plus expenditures to scare birds, averaged $683/ha for golden shiners, $695/ha for fathead minnows, $663/ha for sportfish, and $673/ha for goldfish across the two study years. The fish losses to scaup alone averaged $1.06 million per year ($0.09 million in Year 1 and $2.03 million in Year 2) for the Arkansas baitfish industry. Total direct negative economic effects on the Arkansas baitfish industry were estimated to be, on average, $5.5 million per year ($4.6 in Year 1 and $6.3 million in Year 2).

NATURAL HYBRIDIZATION OF GOLDEN SHINER (NOTEMIGONUS CRYSOLEUCAS) AND RUDD (SCARDINIUS ERYTHROPHTHALMUS) IN A COLORADO RESERVOIR

Golden shiner (Notemigonus crysoleucas) and rudd (Scardinius erythrophthalmus) have been hybridized in a laboratory experiment and a hatchery setting but have not been reported in wild populations. Here we report the presence of golden shiner × rudd hybrids in the wild in Lake San Isabel, Colorado, where both parental species maintain reproducing populations. The hybrid was identified based on intermediate squamation of the keel (cultrate abdomen), where a small fleshy ridge was present at the posterior edge of the keel adjacent to the vent. In contrast, the keel of the golden shiner lacks squamation entirely while the keel of the rudd is completely covered by scales.

Distribution and abundance of scaup using baitfish and sportfish farms in eastern Arkansas

AbstractArkansas' bait‐ and sportfish facilities are commonly used by various piscivorous bird species, including lesser scaup (Aythya affinis) and greater scaup (A. marila) that consume substantial quantities of fish. To mediate this predation, farmers implement extensive bird harassment programs that create additional costs to fish loss, thus research investigating the distribution and abundance of scaup is needed to help farmers allocate their bird harassment efforts more efficiently. In winters 2016–2017 and 2017–2018 we conducted 1,368 pond surveys to investigate pond use by scaup on farms during birds' regular wintering period (i.e., November–March). We used intrinsic and extrinsic pond‐level and farm‐level characteristics as explanatory variables in generalized linear models to reveal characteristics associated with increased scaup use. Inter‐annual differences in scaup use were also considered in each model. Our pond‐level model showed that scaup occurred more frequently on larger golden shiner (Notemigonus crysoleucas) and fathead minnow (Pimephales promelas) ponds stocked at greater densities, particularly during our second study winter. Our farm‐level model suggested that farms further from major rivers and with an average pond size of approximately eight hectares had the greatest probability of scaup use. Producers can apply findings from our models to implement bird harassment efforts in times and locations where scaup predation is more likely to occur.

Acquired Functional Capsid Structures in Metazoan Totivirus-like dsRNA Virus

Non-enveloped icosahedral double-stranded RNA (dsRNA) viruses possess multifunctional capsids required for their proliferation. Whereas protozoan/fungal dsRNA viruses have a relatively simple capsid structure, which suffices for the intracellular phase in their life cycle, metazoan dsRNA viruses have acquired additional structural features as an adaptation for extracellular cell-to-cell transmission in multicellular hosts. Here, we present the first atomic model of a metazoan dsRNA totivirus-like virus and the structure reveals three unique structural traits: a C-terminal interlocking arm, surface projecting loops, and an obstruction at the pore on the 5-fold symmetry axis. These traits are keys to understanding the capsid functions of metazoan dsRNA viruses, such as particle stability and formation, cell entry, and endogenous intraparticle transcription of mRNA. On the basis of molecular dynamics simulations of the obstructed pore, we propose a possible mechanism of intraparticle transcription in totivirus-like viruses, which dynamically switches between open and closed states of the pore(s).

Validation of Annulus Formation in Golden Shiner Otoliths

Abstract Golden Shiner Notemigonus crysoleucas is found in many lakes and ponds across the southeastern United States. Though it is a common species, otolith age validation methods have not been published. The objective of this study was to confirm annulus formation in lapillar otoliths of Golden Shiners collected monthly from September 2015 through August 2016 in Lake Jackson, Florida (Leon County). We collected at least 12 individuals each month of similar length (168–249 mm; presumably of the same cohort) to document annulus formation throughout the year. We sacrificed a total of 177 individuals from the 2013 year class, and we used their lapillar otoliths for marginal incremental analysis to calculate an index of completion and validate annulus formation. The monthly index of completion was highest from January through March and lowest in May and June, indicating that annuli were deposited once per year and confirming that lapillar otoliths are a valid age estimation structure for Golden Shiners.

Diets of scaup occupying baitfish and sportfish farms in eastern Arkansas

Although not typically associated with eating fish, lesser scaup (Aythya affinis) and greater scaup (Aythya marila) have recently been reported consuming large quantities of bait- and sportfish produced on Arkansas commercial aquaculture facilities. During winters 2016–2017 and 2017–2018, we collected 529 lesser scaup and 19 greater scaup foraging on golden shiner (Notemigonus crysoleucas), fathead minnow (Pimephales promelas), goldfish (Carassius auratus), sunfish (Lepomis spp.), and other sportfish production ponds to investigate the diet composition of scaup. We compared lesser scaup diet between years, among temperature categories (Low, Medium, High), and among pond types using PERMANOVAs to investigate foraging dynamics. Lesser scaup diets differed between winters, and between Low and both Medium and High temperature categories. Only traces of fish were detected in scaup in winter 2016–2017, but fish comprised 18% of birds' overall diet in winter 2017–2018. Chironomidae was the most common prey item in lesser scaup during both winters, occurring in 86% and 68% of diets in winter 2016–2017 and 2017–2018, respectively. Chironomidae comprised 40% of lesser scaup diet by weight in winter 2017–2018, but 71% in winter 2016–2017. Similar to lesser scaup, Chironomidae was the most commonly occurring prey item in greater scaup, which occurred in 88% of the diets, or composed 74% of their overall diet. Fish comprised about 13% of the overall diet of greater scaup. We suspect that scaup increasingly exploited fish in colder winters, perhaps because of the birds' increased energy demands, prey availability, and ease of capture, or some combination of these.

Fertilization of Fresh Water Fish Ponds

This document outlines the principles and practices of fertilizing freshwater fish ponds to enhance their productivity. Fertilization, akin to its use in land-based agriculture, can significantly boost the production of small natural food-consuming fish species such as bluegill and golden shiner by increasing the availability of algae and zooplankton. This process not only supports small fish but also benefits larger predatory fish, like largemouth bass, by improving their food supply. Phosphorus is identified as the most critical nutrient, often supplemented with nitrogen for better results. The document discusses the forms and application methods of fertilizers, emphasizing liquid fertilizers for their rapid effectiveness. Practical guidelines for determining the timing and frequency of fertilization based on water temperature and clarity are provided, alongside techniques for applying both liquid and granular fertilizers efficiently. The document also addresses common challenges such as muddy water, aquatic weeds, water exchange, and low alkalinity, and offers solutions for each. Finally, it highlights the importance of a committed, long-term fertilization program to avoid inefficiencies and aquatic weed issues. First published June 1990.

Asian Fish Tapeworm (Schyzocotyle acheilognathi) Found in New York State for the First Time After a Long-Term Fish-Parasite Survey

The first report of Asian fish tapeworm (AFT), Schyzocotyle acheilognathi (Yamaguti, 1934) Brabec, Waeschenbach, Scholz, Littlewood and Kuchta, 2015, is provided for New York State. This finding resulted from a long-term fish parasite survey in various water bodies in Otsego County in central-east New York that took place during 2008–2018. In total, 1,637 individual fish representing 44 species were examined for AFT, with 4 (9%) of the 44 species of fish infected with S. acheilognathi. These 4 species were all cyprinids: Notemigonus crysoleucas (golden shiner), Notropis heterodon (blackchin shiner), Pimephales promelas (fathead minnow), and Semotilus atromaculatus (creek chub). Among these host species, the prevalence of Schyzocotyle acheilognathi was highest in Notemigonus crysoleucas, with 19 (15.7%) of 121 fishes infected. The infection in Notropis heterodon constitutes a new host record for S. acheilognathi. The observed occurrence of S. acheilognathi only in cyprinid species was generally consistent with previously reported infection patterns for this cestode, but we note that AFT was absent from multiple fish species in our survey that had elsewhere been reported as hosts. The source of AFT for water bodies in Otsego County, New York is unknown, but bait-bucket introduction of infected Notemigonus crysoleucas is considered a possible explanation. This study contributes to a growing body of molecular data for this highly invasive tapeworm by providing sequence data for 2 markers (large ribosomal subunit, 28S, and cytochrome c oxidase I) for 6 specimens.

The Effects of Different Winter Feeding Regimens on Growth, Survival, and Fatty Acid Composition of Fathead Minnow and Golden Shiners

AbstractWinter mortality is a common problem for Arkansas baitfish farmers that produce Fathead Minnow (FHM) Pimephales promelas and Golden Shiners (GS) Notemigonus crysoleucas. Winter feeding programs are a potential avenue to improve survival and condition and reduce weight loss of baitfish. Methods of winter feeding vary widely among producers, and currently there are no recognized best management practices. The impacts of different winter feeding regimens on FHM and GS survival, growth, and lipid storage were evaluated in temperature‐controlled aquarium systems. Fathead Minnow (mean ± SD = 0.88 ± 0.04 g) or GS (0.88 ± 0.02 g) were stocked at ambient water temperature, and the temperature was reduced to 6°C (FHM) or 8°C (GS) to mimic winter conditions. Three feeding regimens were implemented (3 tanks/regimen) that included ad libitum feeding twice per week (2×/week), once per week (1×/week), or once per month (1×/month). Significant differences in weight gain (loss), condition factor (K), and specific growth rate were observed after 13 weeks for FHM. Fish that were fed 2×/week gained nearly 3%, while fish that were fed 1×/week or 1×/month lost weight (2.3% and 10.1%, respectively). There were no significant differences in GS final weight (0.79–0.82 g), survival (65.0–88.3%), or weight gain (−6.84% to −9.50%) among treatments after 12 weeks. The GS from the 2×/week treatment had significantly higher K‐values than GS that were fed 1×/week or 1×/month. Fatty acid profiles of both species differed among treatments, showing a decline in saturated fatty acids from initial levels and an increase in polyunsaturated fatty acids (PUFAs) as feeding frequency decreased. Results suggest that fish may lose weight during the winter, but it does not appear to adversely affect survival, and both species alter their fatty acid compositions to optimize n‐3 PUFAs during cold water temperatures.

Integrating Visual Psychophysical Assays within a Y-Maze to Isolate the Role that Visual Features Play in Navigational Decisions.

Collective animal behavior arises from individual motivations and social interactions that are critical for individual fitness. Fish have long inspired investigations into collective motion, specifically, their ability to integrate environmental and social information across ecological contexts. This demonstration illustrates techniques used for quantifying behavioral responses of fish, in this case, Golden Shiner (Notemigonus crysoleucas), to visual stimuli using computer visualization and digital image analysis. Recent advancements in computer visualization allow for empirical testing in the lab where visual features can be controlled and finely manipulated to isolate the mechanisms of social interactions. The purpose of this method is to isolate visual features that can influence the directional decisions of the individual, whether solitary or with groups. This protocol provides specifics on the physical Y-maze domain, recording equipment, settings and calibrations of the projector and animation, experimental steps and data analyses. These techniques demonstrate that computer animation can elicit biologically-meaningful responses. Moreover, the techniques are easily adaptable to test alternative hypotheses, domains, and species for a broad range of experimental applications. The use of virtual stimuli allows for the reduction and replacement of the number of live animals required, and consequently reduces laboratory overhead. This demonstration tests the hypothesis that small relative differences in the movement speeds (2 body lengths per second) of virtual conspecifics will improve the speed and accuracy with which shiners follow the directional cues provided by the virtual silhouettes. Results show that shiners directional decisions are significantly affected by increases in the speed of the visual cues, even in the presence of background noise (67% image coherency). In the absence of any motion cues, subjects chose their directions at random. The relationship between decision speed and cue speed was variable and increases in cue speed had a modestly disproportionate influence on directional accuracy.

Seasonality of a Floodplain Subsidy to the Fish Community of a Large Temperate River

This study examines the temporal and spatial variability of the floodplain trophic contribution to the fish community of Lake Saint-Pierre, a large (≈ 300 km2), shallow (≈ 3 m) widening of the St. Lawrence River (Quebec, Canada). We hypothesized that floodplain contribution to fish diet would be maximal during the early growing period following the seasonal flood and at sites located closest to the floodplain. Carbon stable isotope ratios (δ13C) of invertebrates and 35 fish species were analyzed at the beginning and at the end of two growing seasons, at increasing distances from the floodplain. Floodplain contribution, in the form of exported aquatic invertebrates, was estimated at the fish community (littoral versus main river), species and individual fish level, using a stable isotopic mixing model and a linear mixed model selection. As hypothesized, fish captured in the early part of the growing season near the floodplain benefitted from the largest floodplain contribution, which decreased during the late growing season. In addition, floodplain contribution differed among fish species, being higher in small or immature littoral species (northern pike, yellow perch, blackchin and golden shiners) than for larger taxa inhabiting the main river channel (shorthead redhorse, white sucker and channel catfish). Our study revealed that floodplain production during the early growing season represents a key food resource to a large portion of the riverine food web, thus highlighting the essential role of the floodplain in human-altered temperate rivers.

Competition during early ontogeny: Effects of native and invasive planktivores on the growth, survival, and habitat use of bluegill

Abstract Early life stages of fishes are sensitive to ecological and environmental disturbances and experience very high mortality rates. During early ontogeny, the growth and survival of larval fish often depends on food availability. Because habitat and diet shifts are strongly tied to individual body size, factors that influence the growth rates of individuals (e.g. resource limitation, competition) also affect other aspects of ontogeny including the timing of habitat or diet shifts. In the context of biological invasions, non‐native species can potentially disrupt the interaction of larval fish with their food via competition for shared prey, reducing growth and survival during a vulnerable period of an organism's life history. We hypothesised that invasive planktivores negatively affect native species through the vulnerable larval life stage via competition for zooplankton resources. To test this hypothesis, we conducted a series of experiments to assess and contrast the effects of invasive (bighead carp, Hypophthalmichthys nobilis) and native (golden shiners, Notemigonus crysoleucas) planktivores on zooplankton densities, and their effects on the growth, survival, abundance, and habitat use of larval bluegill (Lepomis macrochirus). Overall, the effects of the invasive planktivore were consistently greater than the native planktivore in terms of reduced prey densities, reduced bluegill growth rates, and delays to the timing of ontogenetic habitat shifts. Growth rates of bluegill larvae were reduced by 58–87% in the presence of bighead carp and 37% in the presence of golden shiners (relative to controls), but such reductions did not consistently lead to reduced survival (in mesocosm experiment) or relative abundance (in pond experiment). However, we estimated that bighead carp and golden shiners delayed ontogenetic habitat shifts in bluegill by 9–24 and 1–3 days, respectively. Although we did not detect an effect of planktivores on the numbers of larval bluegill, our findings suggest that bighead carp may still affect bluegill ontogeny and freshwater food webs by disrupting the timing of ontogenetic habitat shifts. By affecting the coupling of habitats via organism movements during early ontogeny, bighead carp may indirectly disrupt predator–prey interactions of native taxa.

Development of a loop-mediated isothermal amplification assay for the detection and quantification of epizootic epitheliotropic disease virus (salmonid herpesvirus-3)

Epizootic Epitheliotropic Disease Virus (EEDV; Salmonid Herpesvirus-3) causes a serious disease hatchery-reared lake trout (Salvelinus namaycush), threatening restoration efforts of this species in North America. The current inability to replicate EEDV in vitro necessitates the search for a reproducible, sensitive, and specific assay that allows for its detection and quantitation in a time- and cost-effective manner. Herein, we describe a loop-mediated isothermal amplification (LAMP) assay that was developed for the quantitative detection of EEDV in infected fish tissues. The newly developed LAMP reaction was optimized in the presence of calcein, and the best results were produced using 2 mM MgCl2, 1.8 mM dNTPs and at an incubation temperature of 67.1 °C. This method was highly specific to EEDV, as it showed no cross-reactivity with several fish viruses, including Salmonid Herpesvirus-1, -2, -4, and -5, Infectious Pancreatic Necrosis Virus, Spring Viremia of Carp Virus, Infectious Hematopoietic Necrosis Virus, Golden Shiner Reovirus, Fathead Minnow Nidovirus, and Viral Hemorrhagic Septicemia Virus. The analytical sensitivity of the EEDV-LAMP method was estimated to be as low as 16 copies of plasmid per reaction. When infected fish tissue was used, a positive reaction could be obtained when an infected gill tissue sample that contained 430 viral copies/μg was diluted up to five orders of magnitude. The sensitivity and specificity of the newly developed LAMP assay compared to the SYBR Green qPCR assay were 84.3% and 93.3%, respectively. The quantitative LAMP for EEDV had a correlation coefficient (R2 = 0.980), and did not differ significantly from the SYBR Green quantitative PCR assay (p > 0.05). Given its cost- and time-effectiveness, this quantitative LAMP assay is suitable for screening lake trout populations and for the initial diagnosis of clinical cases.

Retail Baitfish in Michigan Harbor Serious Fish Viral Pathogens.

Indigenous small cyprinid fish species play an important role in Great Lakes ecosystems and also comprise the backbone of a multimillion‐dollar baitfish industry. Due to their widespread use in sport fisheries of the Laurentian Great Lakes, there are increasing concerns that baitfish may introduce or disseminate fish pathogens. In this study, we evaluated whether baitfish purchased from 78 randomly selected retail bait dealers in Michigan harbored fish viruses. Between September 2015 and June 2016, 5,400 baitfish divided into 90 lots of 60 fish were purchased. Fish were tested for the presence of viral hemorrhagic septicemia virus (VHSV), spring viremia of carp virus (SVCV), golden shiner reovirus (GSRV), fathead minnow nidovirus (FHMNV), fathead minnow picornavirus (FHMPV), and white sucker bunyavirus (WSBV). Using the epithelioma papulosum cyprini cell line and molecular confirmation, we demonstrated the presence of viruses in 18 of the 90 fish lots (20.0%) analyzed. The most prevalent virus was FHMNV, being detected in 6 of 30 lots of Fathead Minnow Pimephales promelas and 3 of 42 lots of Emerald Shiners Notropis atherinoides. We also confirmed GSRV in two fish species: the Golden Shiner Notemigonus crysoleucas (5 of 11 lots) and Fathead Minnow (3 of 30 lots). Two VHSV (genotype IVb) isolates were recovered from a single lot of Emerald Shiners. No SVCV, FHMPV, or WSBV was detected in any of the fish examined. Some of the infected fish exhibited clinical signs and histopathological alterations. This study demonstrates that live baitfish are a potential vector for the spread of viral pathogens and underscores the importance of fish health certifications for the Great Lakes baitfish industry.

Vulnerability of Juvenile Bighead and Silver Carps to Predation by Largemouth Bass

AbstractThe establishment of Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix throughout the Mississippi River basin potentially expands the prey base for native predators. A mechanistic understanding of interactions between nonnative prey and native predators is needed to assess the potential for predator regulation of Hypophthalmichthys carp populations and impacts on native predator assemblages. We conducted a series of experiments to quantify the selectivity and efficiency of Largemouth Bass Micropterus salmoides predation on juveniles of both of these Hypophthalmichthys species and behaviors that potentially influence this selectivity and efficiency. Selectivity was measured over 24 h in 2‐m‐diameter pools containing one of two prey assemblages consisting of three individuals from each of three species: (1) Bighead Carp with native littoral (Bluegill Lepomis macrochirus) and pelagic prey (Golden Shiner Notemigonus crysoleucas) or (2) Bighead Carp, Silver Carp, and a morphologically similar native prey (Gizzard Shad Dorosoma cepedianum). Foraging efficiency and predator–prey behaviors were quantified in 45‐min trials in which Largemouth Bass foraged on 10 individuals of a single prey species inside a 750‐L observation tank. All prey species were readily attacked and consumed by Largemouth Bass; Silver Carp were selected less often than Gizzard Shad, and Bighead Carp were selected at a higher rate than any of the other prey species. Of the species tested, Bighead Carp formed the tightest schools and were captured most efficiently by Largemouth Bass. Overall, Hypophthalmichthys carps were similar to native prey in their vulnerability to Largemouth Bass; therefore, factors affecting Hypophthalmichthys carp availability relative to native prey may shape postinvasion predator–prey interactions.

Collective gradient sensing in fish schools

Throughout the animal kingdom, animals frequently benefit from living in groups. Models of collective behaviour show that simple local interactions are sufficient to generate group morphologies found in nature (swarms, flocks and mills). However, individuals also interact with the complex noisy environment in which they live. In this work, we experimentally investigate the group performance in navigating a noisy light gradient of two unrelated freshwater species: golden shiners (Notemigonuscrysoleucas) and rummy nose tetra (Hemigrammus bleheri). We find that tetras outperform shiners due to their innate individual ability to sense the environmental gradient. Using numerical simulations, we examine how group performance depends on the relative weight of social and environmental information. Our results highlight the importance of balancing of social and environmental information to promote optimal group morphologies and performance.