Golden Shiner Notemigonus Crysoleucas Research Articles

Resetting the Clock: How a Reconnection Event Reshaped Cove Fish Assemblages in a Nebraska Reservoir

AbstractCoves are part of the mosaic of fish habitats in many U.S. reservoirs, but over time these coves may be disconnected from the main reservoir for varying durations due to the buildup of sediment berms at the mouth that are higher than reservoir elevations. Our 4‐year study (2017–2020) of five coves in Harlan County Reservoir, Nebraska, across three seasons (spring, summer, and fall) provided an opportunity to compare fish communities between coves that have remained connected to the main body of the reservoir and coves that have been intermittently connected to or disconnected from the reservoir over the past 10 years. Further, we were able to evaluate fish community changes in coves following substantial flood events in 2019 that reconnected all disconnected coves to the main body of the reservoir. Taxonomic richness and diversity were lower in the intermittently connected and disconnected coves compared to the connected coves in 2017 and 2018. Only Common Carp Cyprinus carpio were found in the disconnected cove, and Black Bullheads Ameiurus melas were only found in intermittent coves. However, fish communities notably shifted in intermittently connected and disconnected coves after the reconnection event in 2019 and became more similar to those in connected coves. Most notably, species richness in the disconnected cove increased from 1 species preconnection to 18 species postconnection, and two new species (Flathead Catfish Pylodictis olivaris and Golden Shiner Notemigonus crysoleucas) were found in at least one cove type during the postflood period that had not been present in any coves prior to the connection. Results from this study underscore the importance of coves as habitats for some species and provide insights as to how fish communities may change when coves are reconnected, whether by human intervention or variations in reservoir elevation.

Effects of Crowding and Water Flow on Golden Shiners Notemigonus crysoleucas, Held in a Flow Tank.

Split-pond systems (SPS) such as those used for catfish are being considered for raising baitfish. When using these systems for baitfish such as golden shiners Notemigonus crysoleucas, an important factor to be considered is how well the species can tolerate crowding, as the design mandates fish be confined to a smaller portion of the pond. Another aspect of the SPS design is the water flow between the two units for at least 10–14 h each day. SPS can be successfully implemented for other species if factors such as crowding, and water flow do not affect growth. Two laboratory studies were conducted each using 12, 40-L tank flow-through system to observe the growth and physiological performance of golden shiners held for 28 days at three crowding densities: 600; 1,200, and 2,400 fish/m3, keeping water flow at 1 cm/s (Experiment 1) and using three flow rates: 1, 2, and 4 cm/s at similar densities (600 fish/m3) (Experiment 2). At the end of the experiments, fish were subject to acute 1-min confinement stress and whole-body cortisol was measured at 30 min intervals for up to 2 h to monitor the secretion pattern and recovery. Results from experiments showed no difference in the final weight, length, feed conversion, and survival among treatment groups; survival rates were lower in the flow study because of columnaris Flavobacterium covae infections. Baseline cortisol was also not different among the treatments. Cortisol increased 30 min after the acute stress and returned to near baseline in 2 h in the crowding study suggesting acclimation to the chronic stressor. However, in the flow study, cortisol remained elevated even after 2 h, and hence a compromised pathophysiological response. Crowding and water flow do not impair feed intake, growth, or survival in golden shiners, and in these aspects may be a suitable species for SPS.

Effect of Intermittent Traveling Water Screen Operation on Fish Survival

AbstractThe U.S. Environmental Protection Agency’s final rule for complying with section 316(b) of the Clean Water Act states that cooling water intakes withdrawing >7.6 million liters per day must use one of seven alternatives to reduce fish impingement mortality. Fish‐friendly traveling water screens (TWSs) are expected to be frequently utilized because of relative ease of retrofit. The final rule requires “continuous or near continuous screen rotation” to facilitate recovery of collected fish as soon as practical. However, intermittent TWS operation could be advantageous for operators because reductions in screen system operating time will extend equipment life and reduce operating costs. A laboratory evaluation was conducted with Golden Shiner Notemigonus crysoleucas, Bluegill Lepomis macrochirus, Largemouth Bass Micropterus salmoides, and Common Carp Cyprinus carpio (42–106 mm TL) to determine whether intermittent rotation would optimize TWS operation and maintain biological performance. A preliminary evaluation was conducted with three approach velocities (0.30, 0.45, and 0.60 m/s) at four stationary screen durations (2, 4, 6, 12 h) in small test flumes to select parameters for a larger‐scale evaluation. The full‐scale evaluation tested two approach velocities (0.30 and 0.45 m/s) at two stationary durations (2 and 4 h at 0.45 m/s; 6 and 12 h at 0.30 m/s) and continuous screen operation. Fish avoided impingement at 0.30 m/s, and approach velocity was the primary determinant of survival probability, with increased velocity leading to increased mortality. Severe injuries occurred more frequently during stationary screen trials than with continuous operation; over 50% of fish had >40% scale loss at 0.45 m/s for stationary trials. The results indicate that continuous rotation is optimal for fish survival at approach velocities between 0.30 and 0.45 m/s. However, intermittent operation at average approach velocities of 0.30 m/s or less may be acceptable for fishes with equal or greater swimming ability than those tested in this study.

Hydrological control of a floodplain subsidy to littoral riverine fish

Ecological subsidies have been hypothesized to be key factors affecting the dynamics of the recipient ecosystems. We assessed the impact of the flood regime on the assimilation of a trophic subsidy produced in the floodplain of a large fluvial lake, Lake Saint-Pierre (Quebec, Canada) on five invertivore littoral fish species (yellow perch (Perca flavescens), pumpkinseed (Lepomis gibbosus), bridle shiner (Notropis bifrenatus), golden shiner (Notemigonus crysoleucas), and banded killifish (Fundulus diaphanus)). We hypothesized that the incorporation of floodplain-derived carbon into fish biomass and individual fitness would increase in years with higher magnitude and longer duration floods. Studying four consecutive years with contrasting spring-flood events, we used a stable isotope mixing model to estimate floodplain contribution, and linear mixed models to analyze the impact of hydrology on floodplain contribution and fish body condition. Floodplain and main river’s invertebrates exhibited statistically distinct isotopic ratios (t test: p value < 0.001). Floodplain contribution and body condition were positively correlated with flooding intensity and duration for all species. Body condition was positively correlated with the assimilation of floodplain-subsidy for golden shiner and banded killifish. Our study identified flooding intensity as a main driver influencing the assimilation of floodplain-derived carbon by littoral fish and their fitness in a large river ecosystem.

A needle in the haystack? Applying species co-occurrence frameworks with fish assemblage data to identify species associations and sharpen ecological hypotheses.

Different species can associate or interact in many ways, and methods exist for inferring associations and underlying mechanisms from incidence data (e.g., co-occurrence frameworks). These methods have received criticism despite their recent resurgence in the literature. However, co-occurrence frameworks for identifying nonrandomly associated species pairs (e.g., aggregated or segregated pairs) have value as heuristic tools for sharpening hypotheses concerning fish ecology. This paper provides a case study examining species co-occurrence across 33 stream fish assemblages in southeastern Oklahoma, USA, which were sampled twice (1974 and 2014). This study sought to determine (a) which species were nonrandomly associated, (b) what processes might have driven these associations and (c) how consistent patterns were across time. Associations among most pairs of species (24 species, 276 unique pairs) were not significantly different from random (>80%). Among all significant, nonrandomly associated species pairs (54 unique pairs), 78% (42 pairs) were aggregated and 22% (12 pairs) segregated. Most of these (28 pairs, 52%) were hypothesized to be driven by nonbiotic mechanisms: habitat filtering (20 pairs, 37%), dispersal limitation (two pairs, 0.4%) or both (six pairs, 11%). The remaining 26 nonrandomly associated pairs (48%) had no detectable signal of spatial or environmental factors involved with the association, therefore the potential for biotic interaction was not refuted. Only five species pairs were consistently associated across both sampling periods: stonerollers Campostoma spp. and orangebelly darter Etheostoma radiosum; red shiner Cyprinella lutrensis and bullhead minnow Pimephales vigilax; bluegill sunfish Lepomis macrochirus and redear sunfish Lepomis microlophus; redfin shiner Lythrurus umbratilis and bluntnose minnow Pimephales notatus; and bigeye shiner Notropis boops and golden shiner Notemigonus crysoleucas. Frameworks for identifying nonrandomly associated species pairs can provide insight into broader mechanisms of species assembly and point to potentially interesting species interactions (out of many possible pairs). However, this approach is best applied as a tool for sharpening hypotheses to be investigated further. Rather than a weakness, the heuristic nature is the strength of such methods, and can help guide biologists toward better questions by employing relatively cheap diversity survey data, which are often already in hand, to reduce complex interaction networks down to their nonstochastic parts which warrant further investigation.

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.

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.

Susceptibility of Representative Great Lakes Fish Species to the North Carolina Strain of Spring Viremia of Carp Virus (SVCV).

Spring viremia of carp virus (SVCV) is a notifiable pathogen of the World Organization of Animal Health. Since SVCV was isolated in Lake Ontario in 2007, concern has grown about its spread in the Great Lakes basin and its potential negative impacts on fish species of importance in stock enhancement programs basinwide. The susceptibility of representative fish species from the families Cyprinidae (Fathead Minnow Pimephales promelas, Golden Shiner Notemigonus crysoleucas, Spotfin Shiner Cyprinella spiloptera, and Creek Chub Semotilus atromaculatus), Centrarchidae (Largemouth Bass Micropterus salmoides), Percidae (Walleye Sander vitreus), Salmonidae (Rainbow Trout Oncorhynchus mykiss), and Esocidae (Muskellunge Esox masquinongy) to SVCV was evaluated by experimental infection under laboratory conditions. Morbidity and mortality were recorded, and virus re-isolation, seminested reverse transcription PCR, and histopathological assessments were performed. Using intraperitoneal (i.p.) injection, Fathead Minnows and Golden Shiners were highly susceptible to SVCV (40-70% mortality). All dead or moribund and apparently healthy surviving Fathead Minnows and Golden Shiners were SVCV positive. The SVCV was also detected in challenged but healthy Spotfin Shiners (30%) and Creek Chub (5%). However, noncyprinid species exhibited no morbidity or mortality and were free of SVCV following an observation period of 30 d. In a follow-up experimental challenge, Fathead Minnows and Golden Shiners were SVCV challenged at 103 and 105 PFU/mL by means of waterborne immersion. After immersion, Fathead Minnows and Golden Shiners exhibited characteristic SVCV disease signs, but mortality was less (30% and 10% mortality, respectively) than that in fish with i.p. injections. The SVCV was detected in all mortalities and a subset of healthy Fathead Minnows and Golden Shiners. Necrotic changes were observed in the kidneys, liver, spleen, ovaries, and heart, and other histopathological lesions also occurred. These findings suggest that two of the four cyprinids tested are susceptible to SVCV-induced disease and that all four can act as potential carriers of SVCV in the Laurentian Great Lakes. Received January 11, 2017; accepted July 17, 2017.

Toxic, invasive treefrog creates evolutionary trap for native gartersnakes

Possession of unique defensive toxins by nonindigenous species may increase the likelihood of creating evolutionary traps for native predators. We tested the hypothesis that nonindigenous, toxic Cuban Treefrogs (Osteopilus septentrionalis) have created an evolutionary trap for native, generalist snakes. Additionally, we explored the possibility that populations of snakes that co-occur with Cuban Treefrogs have responded in ways that allow them to escape potential trap dynamics. To evaluate a potential fitness cost of consuming Cuban Treefrogs, we monitored growth of 61 wild-caught Common Gartersnakes (Thamnophis sirtalis) fed exclusive diets of either Cuban Treefrogs, native Green Treefrogs (Hyla cinerea), or native Golden Shiners (Notemigonus crysoleucas). Snakes in the Cuban Treefrog diet treatment gained less than half the mass of those consuming native prey, and Cuban Treefrogs were significantly less digestible than native prey. There was no difference in the response of gartersnakes to prey scent cues of Cuban Treefrogs and Green Treefrogs. Our results indicate that Cuban Treefrogs likely represent an evolutionary trap for snakes because consumption of these frogs carries fitness costs, yet snakes fail to recognize this prey as being costly. We found no difference in growth or response to prey cues between snakes from invaded and non-invaded regions, suggesting snakes have not responded to escape trap dynamics. Interactions of native snakes and Cuban Treefrogs support the idea that introduced species with novel toxins may increase the likelihood of evolutionary trap formation.

Using stable isotope analysis to assess the effects of hypolimnetic oxygenation on diet in a mixed cold- and warmwater fish community

Line-diffuser hypolimnetic oxygenation was initiated in North Twin Lake, Washington, in 2009 to mitigate reductions in Rainbow Trout (Oncorhynchus mykiss) and Brook Trout (Salvelinus fontinalis) habitat due to temperature-dissolved oxygen “habitat squeeze”. Previous studies demonstrated that trout populations rapidly expanded into increased hypolimnetic habitat within the first few years of oxygenation and previous short-term diet analyses indicated an effect on fish diet; however, the long-term effects on fish ecology have yet to be established. In this study, stable isotope analysis of fish liver tissue suggests relatively few differences in feeding ecology of principal coldwater fish species in North Twin Lake compared to unoxygenated South Twin Lake. When compared between lakes, Rainbow Trout and Brook Trout diets contained similar proportions of Daphnia, Chironomidae, and Chaoboridae. Littoral and epilimnetic-focused Golden Shiner (Notemigonus crysoleucas) diets were also similar between lakes. Observed similarities between Golden Shiner and trout diets suggest the effects of interspecific competition between salmonids and non-salmonids may be limiting trout growth and survival. Fisheries managers should therefore consider both habitat limitations and interspecific competition when managing for coldwater fish species in mesotrophic, dimictic lakes.

Feeding Ecology of Brook Silverside, Golden Shiner, and Subyearling Pumpkinseed in a Lake Ontario Embayment

Abstract Fish feeding ecology has been shown to vary over a 24-h period in terms of the prey consumed and feeding intensity. Consequently, in order to best determine the interspecific feeding associations within a fish community, examination of the diet at multiple times over a 24-h period is often necessary. We examined the diel feeding ecology of three fish species that were numerically dominant in a Lake Ontario embayment during summer. The diet of each of the three species, young-of-year Pumpkinseed Lepomis gibbosus, Golden Shiner Notemigonus crysoleucas, and Brook Silverside Labidesthes sicculus, was distinct with no significant overlap in diet composition occurring within any of the 4-h time intervals. The diet composition of each species suggested that Brook Silverside were feeding at the surface (terrestrial invertebrates and aquatic surface dwelling hemipterans), whereas young-of-year Pumpkinseed (amphipods) and Golden Shiner (tipulids) were feeding on different benthic prey. Differences in feeding periodicity were most pronounced for young-of-year Pumpkinseed. Our findings provide valuable insights on interspecific feeding associations among these three fish species during summer in a Lake Ontario embayment.

General and histological indicators of health in wild fishes from a biological mercury hotspot in northeastern North America.

Kejimkujik National Park and National Historic Site, Nova Scotia, Canada, is considered a biological mercury (Hg) hotspot because the tissues of yellow perch (Perca flavescens) and common loons (Gavia immer) inhabiting the lakes frequently exceed so-called safe levels of Hg. In the present study, the relationships between Hg and overall health of males and females of 3 forage fish species (brown bullhead Ameirus nebulosus, banded killifish Fundulus diaphanus, and golden shiner Notemigonus crysoleucas; n = 6-18/sex/lake) in 6 lakes at the park were assessed using condition factor, liversomatic index (LSI), and macrophage aggregates (MAs; indicators of tissue damage). Mean muscle total Hg (THg) concentrations of brown bullhead, banded killifish, and golden shiner across lakes were 0.32 μg/g, 0.27 μg/g, and 0.34 μg/g, respectively. Condition was negatively related to muscle THg in golden shiner and banded killifish, LSI was not related to THg in any species, and all species showed evidence of increasing MA prevalence (counts and area) with increasing THg concentrations. The MAs were most prevalent in spleen tissues of golden shiner, with mean percentage cover ranging from 0.36% to 5.59% across lakes. In addition, the area of MAs appeared to be better predicted by THg concentration than was the number of MAs in the same tissue. These findings suggest that Hg is affecting the health of wild fishes in Kejimkujik National Park and National Historic Site and that other populations with similar or higher concentrations of this metal may also be at risk. Environ Toxicol Chem 2017;36:976-987. © 2016 SETAC.

Effect of Turbidity on the Swimming Performance of the Golden Shiner,Notemigonus crysoleucas

Of the many environmental factors that could affect swimming performance and critical swimming speed (Ucrit), turbidity has received relatively little attention. The purpose of this study was to examine the effects of turbidity on Golden Shiner (Notemigonus crysoleucas) swimming performance through the analysis of critical swimming speed. It was found that turbidity had an effect on critical swimming speeds; critical swimming speeds increased significantly with rising turbidity values. At the highest turbidity levels reported in this paper, Golden Shiner experienced a 56.5% increase in critical swimming speed over controls swimming in clear water. We likewise observed an increase in swimming efficiency and cost of transport with increasing turbidity. We suggest that a hydrodynamic effect may be the most likely explanation for the increase in performance and swimming efficiency observed in this study.

Fathead minnow nidovirus infects spotfin shiner Cyprinella spiloptera and golden shiner Notemigonus crysoleucas.

Since the initial isolation of the fathead minnow nidovirus (FHMNV), concerns have been raised regarding the risks it may pose to other fish species. In this study, 7 fish species resident to the Laurentian Great Lakes were challenged intraperitoneally with 2 doses of FHMNV: 102.8 and 104.8 median tissue culture infective dose (TCID(50)) ml(-1). Infected spotfin shiner Cyprinella spiloptera and golden shiner Notemigonus crysoleucas suffered morbidity and mortality during the 40 d observation period, while other species, including creek chub Semotilus atromaculatus, rainbow trout Oncorhynchus mykiss, largemouth bass Micropterus salmoides and walleye Sander vitreus, showed no clinical signs or mortality. FHMNV was re-isolated on the epithelioma papulosum cyprini cell line from the tissues of infected spotfin shiner and golden shiner, which harbored high numbers of viral RNA copies as measured by quantitative loop-mediated isothermal amplification. Infected spotfin shiner and golden shiner exhibited external petechiae, exophthalmia, oedematous kidneys, and liver pallor. Histopathological analysis revealed multifocal areas of necrosis in the kidney, spleen and liver of infected fish. Spotfin shiner and golden shiner were then infected with 2 doses of FHMNV (10(3.5) and 10(3.9) TCID(50) ml(-1)) by immersion to mimic more natural modes of infection. Spotfin shiner experienced 60% mortality at both doses, while golden shiner did not experience mortality nor develop any clinical signs following a 40 d observation period. Overall, piscivorous fish tested in this study do not seem to be at risk for infection, while cyprinids appear to vary in their susceptibility to the strain of FHMNV used in this study.

Reconstructing a trophic cascade following unintentional introduction of golden shiner to Lake Minnewaska, New York, USA

Introductions of new species may rapidly and irreversibly change lake food webs and ecosystems, but such events are rarely documented as a result of inadequate pre-invasion monitoring. We examined the unintentional introduction of a fish species, golden shiner (Notemigonus crysoleucas), a small planktivorous minnow, to Lake Minnewaska, New York State, USA. We predicted that the introduction had caused a trophic cascade resulting in increased algal biomass and decreased water clarity mediated by decreasing zooplankton size and biomass. This prediction was confirmed using limited monitoring data through comparisons made between “control” lakes (both with fish in Mohonk Lake and without fish in Lake Awosting) and the “intervention” lake (Minnewaska).

Vision in two cyprinid fish: implications for collective behavior.

Many species of fish rely on their visual systems to interact with conspecifics and these interactions can lead to collective behavior. Individual-based models have been used to predict collective interactions; however, these models generally make simplistic assumptions about the sensory systems that are applied without proper empirical testing to different species. This could limit our ability to predict (and test empirically) collective behavior in species with very different sensory requirements. In this study, we characterized components of the visual system in two species of cyprinid fish known to engage in visually dependent collective interactions (zebrafish Danio rerio and golden shiner Notemigonus crysoleucas) and derived quantitative predictions about the positioning of individuals within schools. We found that both species had relatively narrow binocular and blind fields and wide visual coverage. However, golden shiners had more visual coverage in the vertical plane (binocular field extending behind the head) and higher visual acuity than zebrafish. The centers of acute vision (areae) of both species projected in the fronto-dorsal region of the visual field, but those of the zebrafish projected more dorsally than those of the golden shiner. Based on this visual sensory information, we predicted that: (a) predator detection time could be increased by >1,000% in zebrafish and >100% in golden shiners with an increase in nearest neighbor distance, (b) zebrafish schools would have a higher roughness value (surface area/volume ratio) than those of golden shiners, (c) and that nearest neighbor distance would vary from 8 to 20 cm to visually resolve conspecific striping patterns in both species. Overall, considering between-species differences in the sensory system of species exhibiting collective behavior could change the predictions about the positioning of individuals in the group as well as the shape of the school, which can have implications for group cohesion. We suggest that more effort should be invested in assessing the role of the sensory system in shaping local interactions driving collective behavior.

The Effectiveness of Flow‐Through or Static Copper Sulfate Treatments on the Survival of Golden Shiners and Fathead Minnows Infected with Flavobacterium columnare

AbstractFour studies were conducted to compare the effects of copper sulfate (CuSO4), when delivered in either a flow‐through or a static system, on the survival of Golden Shiners Notemigonus crysoleucas and Fathead Minnows Pimephales promelas infected with Flavobacterium columnare. The treatment regimens were administered to fish in well water and were based on the recommended treatment rate (1% of alkalinity). Golden Shiners (experiments 1 and 3) and Fathead Minnows (experiments 2 and 4) were treated separately. In experiments 1 and 2, the treatment rate was 2.0 mg/L CuSO4 applied to a flow‐through system daily for five consecutive days; control fish were untreated. Study durations were 7 d with the majority of the mortalities occurring in the first 5 d. Survival rates in the flow‐through system were 77% and 69% for CuSO4‐treated Golden Shiners and Fathead Minnows, respectively. Survival in both species was significantly different from that in their untreated control fish, which was 33% for Golden Shiners and 41% for Fathead Minnows. Static applications of CuSO4 were investigated in experiments 3 and 4. Treatment doses were 0, 0.5, 1, 2, and 4 mg/L (approximately 0.0, 0.25, 0.5, 1, and 2 times the recommended rate). Survival of Fathead Minnows in this experiment was 10, 28, 52, 47, and 35% in the 0, 0.5, 1, 2, and 4 mg/L CuSO4 treatments, respectively. The corresponding survival of Golden Shiners was 49, 50, 65, 75, and 60% in the 0, 0.5, 1, 2, and 4 mg/L CuSO4 treatments, respectively.

Hypolimnetic oxygenation in Twin Lakes, WA. Part II: Feeding ecology of a mixed cold- and warmwater fish community

Line-diffuser hypolimnetic oxygenation (HO) was initiated in North Twin Lake, Washington, in 2009 to mitigate loss of coldwater fishery habitat due to temperature–dissolved oxygen “habitat squeeze” and to reduce internal phosphorus cycling. Active tracking, net-captures, and hydroacoustic analyses demonstrated that trout populations rapidly expanded into increased hypolimnetic habitat within the first few years of oxygenation; however, long-term fishery benefits and many basic ecological aspects of HO have yet to be established. Diet and food web analyses indicate significant changes in feeding ecology of principal coldwater fish species in North Twin in 2012 compared to preoxygenation (2005) and to unoxygenated South Twin in 2012. North Twin rainbow trout (Oncorhynchus mykiss) consumed significantly more large-bodied Daphnia during midsummer 2012 than in South Twin, where rainbow trout fed primarily on littoral amphipods. Additionally, relative gut weight for brook trout (Salvelinus fontinalis) in August 2012 was significantly higher in North Twin compared to South Twin, apparently due to increased access to hypolimnetic zooplankton. Golden shiner (Notemigonus crysoleucas) diets also seem to include more zooplankton in oxygenated North Twin. Littoral-focused largemouth bass (Micropterus salmoides) diets were not altered by HO. Observed changes in feeding ecology following HO have significant implications for future fishery management in the Twin Lakes.

Effects of Dietary Protein and Fish Density on Performance and Production Economics of Golden Shiners in Pools

AbstractWe conducted an outdoor feeding trial with Golden Shiners Notemigonus crysoleucas using diets with 22% or 28% protein from different sources. The 28% protein diet with soybean (SOY) meal was the control, and the three other diets contained 22% protein mainly from SOY, corn gluten feed (CGF), or corn distillers dried grains with solubles (DDGS). The 22% protein SOY diet was also offered as a meal or pellet in separate treatments. Each of the five diets was fed to fish at two densities: 250,000 fish/ha (low density) or 750,000 fish/ha (high density). Fish with an initial weight of 0.25 ± 0.003 g (mean ± SE) were stocked into four 4.1‐m3 pools per treatment and fed daily to apparent satiation for 9 weeks. Diet effects were assessed by measuring growth, survival, feed conversion, condition index, and body composition. An enterprise budget analysis was conducted to determine the economic effects of different treatments. Fish weight gain was higher at the low density regardless of diet. Weight gain was also higher in fish fed the diet with 28% protein than in those fed other diets at either density. Relative weight (Wr) was higher at the high density and in fish fed the SOY diets compared with those fed the CGF or DDGS diets. Survival was higher at the high density, and no diet effects were apparent. Gross yield was higher at the high density and in the 28% protein SOY control. Feed conversion ratio was better at the low density. Whole‐body lipid was higher in fish at the low density. The most economically beneficial diet was the 28% protein SOY diet, but producers must consider feed choice in the context of their overall business model. The 22% protein diets were inadequate for rapid growth, but did not compromise survival, indicating a possible use for maintenance feeding when fish reach market size.