Spotfin Shiner Research Articles

Lost from Oz? Status of the Sunflower State's Ozarkian Fish Fauna

There are 10 native Kansas fish species that occur only in the Spring River subbasin (SRS) and nowhere else in the state, which we term Kansas` Ozarkian fish fauna. Eight of these fishes are listed as species in need of conservation (SINC), highlighting their conservation value. The temporal trends and current statuses of Kansas` Ozarkian fishes is unclear, and as such our objective was to assess the historic and current prevalence of these species. We accomplished our objective by compiling historic data from three datasets distributed across three time periods (i.e., 1962-1964; 1993-1995; 1995-2013), which we then compared to data we collected in the SRS during 2017-2020. We calculated occupancy and relative abundance for each species during each of the four time periods, then we visualized changes in prevalence over time. We found that all species were a relatively rare component of the SRS fish assemblage as indicated by their low occupancies and relative abundances across all four time periods, yet some species were rarer than others. Among Kansas's Ozarkian fishes, the Spotfin Shiner and Northern Hog Sucker were the most prevalent and exhibited stable trends. The Banded Sculpin, Sunburst Darter, and Striped Shiner were the rarest and exhibited declining trends, and the Highland Darter and Ozark Minnow exhibited intermediate prevalence and stability. Finally, the Black Redhorse was always rare across all four time periods, and the Least Darter and Plains Topminnow had not been detected in Kansas since 1963. Even though Kansas` Ozarkian fishes currently have a similar conservation listing of SINC or not listed, our research indicated that the Black Redhorse, Highland Darter, and Ozark Minnow may require uplisting to threatened, and that the Banded Sculpin, Striped Shiner, and Sunburst Darter may require uplisting to endangered. Taking action by propagating and repatriating the remaining Ozarkian fishes to their historical ranges in Kansas, coupled with other conservation measures, may help prevent these fishes from ending up like the fictional character, Dorothy, such that they are not in Kansas anymore.

Diet and isotopic niche of eastern sand darter (Ammocrypta pellucida) near the northern edge of its range: a test of niche specificity

Niche specificity can predispose species to population declines during periods of resource limitation, yet trophic niche specificity is poorly known for many small-bodied freshwater fishes. Applying a two-tiered approach involving stomach content and stable isotope analyses, we examined the diet and trophic niche of the threatened eastern sand darter (Ammocrypta pellucida (Putnam, 1863)) and co-occurring fishes in the Thames River, Ontario, Canada. As with previous studies, stomach content analysis revealed that eastern sand darter consumed a variety of benthic organisms including Chironomidae, Cladocera, Ostracoda, Oligochaeta, and Ephemeroptera; however, proportional contributions of prey groups differed based on stable isotope analysis, highlighting the potential for seasonal variation in prey consumption. Despite evidence of a generalist strategy, stable isotope analysis indicated eastern sand darter exhibited a relatively narrow trophic niche relative to co-occurring fishes. Trophic niche overlap was relatively minor between eastern sand darter and drift-feeding fishes (spotfin shiner (Cyprinella spiloptera (Cope, 1867)), emerald shiner (Notropis atherinoides Rafinesque, 1818), and buffalo sp. (genus Ictiobus Rafinesque, 1820)), but was more evident between eastern sand darter and benthic and benthopelagic fishes (johnny darter (Etheostoma nigrum Rafinesque, 1820) and blackside darter (Percina maculata (Girard, 1859))), indicating that competition with these species may be more likely during periods of prey scarcity.

Preliminary Understanding of Complexities in Swimming Performance of Common Minnow (Cyprinidae) Taxa

Understanding swimming performance of native freshwater fishes has implications for ecology, conservation, and management. In particular, this type of information has practical importance for improving the understanding of fish dispersal, occurrence, migration, and invasive potential. The objective of this study was to characterize swimming performance of 2 taxa from the comparatively understudied minnow family (Cyprinidae) and test for potential drivers as a function of total length, sex, habitat, morphology, or some combination. The study assessed Spotfin Shiner (Cyprinella spiloptera; n = 66) and Bluntnose Minnow (Pimephales notatus; n = 24) populations from an ontogenic range of male and female individuals from lentic and lotic habitats in Indiana and Ohio. Akaike information criterion (AIC) model selection identified the most parsimonious linear regression model to predict swimming performance of Spotfin Shiner and Bluntnose Minnow independently. Overall, larger Spotfin Shiners were superior swimmers compared with smaller individuals. In both species, individuals having more streamlined heads and elongated caudal regions were better swimmers. Additionally, Spotfin Shiners that were collected from lotic environments were generally better swimmers than individuals from lentic environments. Models did not recover sex-specific effects in either species—or meaningful total length, or habitat effects, in Bluntnose Minnows. Overall, this study provides evidence of a complex series of swimming performance covariates when assessing or understanding performance. This has implications for aquatic population, assemblage, and community ecology as well as management and conservation efforts.

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.

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.

Effects of historic flooding on fishes and aquatic habitats in a Missouri River delta

Understanding the effects of disturbances on aquatic biota is important for management of the world's rivers. Riverine deltas are among the most biologically productive ecosystems, yet the ecological effects of floods in deltas are poorly understood. Therefore, the goal of this study was to examine impacts of an historic flood in the Missouri River basin in 2011 on fishes and aquatic habitats in the Lewis and Clark Delta, located in South Dakota and Nebraska, USA. Fish community structural indices declined in the six years preceding the flood, with species richness and diversity (Fisher's α) decreasing from 25 to 22 and 4.56 to 3.48, respectively. However, the fish community exhibited short-term resistance to the flood as both metrics were similar to pre-flood levels after the disturbance in 2012. Evenness (J′) declined from 0.88 to 0.73 before the flood but increased to 0.84 after the disturbance. The majority of species exhibited greater relative abundance after the flood regardless of age class (i.e., juvenile, adult), morphology (i.e., small-bodied, large-bodied), introduction history (i.e., introduced, native), or recreational importance (i.e., sport fish, non-recreational). However, the flood reduced relative abundance of juvenile freshwater drum (Aplodinotus grunniens) and white crappie (Pomoxis annularis) and did not affect the three small-bodied species that were studied, including emerald shiner (Notropis atherinoides), red shiner (Cyprinella lutrensis), and spotfin shiner (Cyprinella spiloptera). The flood decreased side channel and backwater frequency and width/area but increased sandbar abundance. Physical alterations evidently had minimal effects on structural indices of the fish community. However, an overall increase in relative abundance across species suggests that interspersed fluvial and slackwater habitats in the delta provided refuge from floodwaters during the disturbance. Maintaining habitat connectivity in deltas during and after floods is particularly important for fisheries conservation. Illustrating the ecological effects and implications of a major flood, this study contributes to the nascent field of delta ecology.

Fish growth, physiological stress, and tissue condition in response to rate of temperature change during cool or warm diel thermal cycles

The effect of the rate of temperature change on fish was studied by exposing a variety of North American fish species to diel temperature cycles containing rates of change of 0.8, 1.1, 2.2, or 4.4 °C·h−1. During a simulated cool season (3.9–11.7 °C), bluntnose minnow (Pimephales notatus), spotfin shiner (Cyprinella spiloptera), and white sucker (Catostomus commersonii), but not smallmouth bass (Micropterus dolomieu), gained mass in response to 0.8, 1.1, or 2.2 °C·h−1but not constant mean temperature. White sucker did not grow under 4.4 °C·h−1, which was slower than expected based upon bioenergetics models. Physiological indicators of acute stress (day 1 cortisol), chronic stress (day 44 cortisol and triglycerides), and histomorphological measures suggested no effect of treatment. During a simulated warm season (20.0–27.8 °C), growth by channel catfish (Ictalurus punctatus), rosyside dace (Clinostomus funduloides), smallmouth bass, and spotfin shiner was not altered by any rate of temperature change; however, walleye (Sander vitreus) and white sucker grew slower than expected under 4.4 °C·h−1. Physiological indicators of acute stress (day 1 cortisol), chronic stress (day 29 cortisol and triglycerides), and histomorphological measures suggested no effect of treatment. Chronic exposure to temperature change of 4.4 °C·h−1may not induce an acute or chronic stress response but may slightly impair growth for some species.

Temporal Stability Patterns in Fish Species Richness, Diversity, and Evenness in Otter Creek, Vigo County, IN

We used abundance data from fish-population studies (1962–2010) on Otter Creek at Markle's Dam, Vigo County, IN, to examine temporal variation in stream-fish assemblages. Species-richness variation showed a declining trend during the 50 year study period with a mean of 49 ± 8.8 species per decade (range = 39–62 species). Cumulative study species richness comprised 76 fish species with a mean of 21.3 ± 6.1 species collected per sampling event. Dominant species, based on relative abundance during the 50 year period, included Cyprinella spiloptera (Spotfin Shiner), Pimephales notatus (Bluntnose Minnow), Hybognathus nuchalis (Mississippi Silvery Minnow), and Luxilus chrysocephalus (Striped Shiner). Relative abundance of Spotfin Shiner showed an increasing trend during the 50-year study period, whereas Bluntnose Minnow relative abundance showed a decreasing trend. Cumulative frequency-distribution of species richness normalized by decade showed no significant difference, with the exception of the 1970s, which showed a steep decline in the number of species. Repeated-measures analysis of variance showed no significant differences in species diversity (H') or evenness (Pielou's J) over the 5-decade study period. Eleven cool-water species including Chrosomus erythrogaster (Southern Redbelly Dace), Perca flavescens (Yellow Perch), Catostomus commersonii (White Sucker), and Ambloplites rupestris (Rock Bass), and lithophilic spawning species such as Nocomis micropogon (River Chub) and Hybopsis amblops (Bigeye Chub) were extirpated during the study period. Potential changes in sedimentation and thermal gradients may have contributed to these observed extirpations.

Day and Night Substrate Use in Six Minnow Species

We tested for diel substrate use in artificial stream experiments for six minnows: redfin shiner (Lythrurus umbratilis), silver shiner (Notropis photogenis), spotfin shiner (Cyprinella spiloptera), central stoneroller (Campostoma anomalum), striped shiner (Luxilus chrysocephalus), and bluntnose minnow (Pimephales notatus). Our experimental pools contained two of three possible substrate types (sand, cobble, and gravel) per trial, and we tested if habitat use differed in day and night observations. Over 85% of individuals and all species were observed over cobble substrate during the day, and no species occurred in higher abundances over a single substrate type at night. Fish locations during night observations were over cobble and sand or cobble and gravel. Our results suggest that minnows use coarse substrates during the day and do not have substrate preferences at night. Habitat use studies with only daytime observations of small-bodied fishes likely cannot be interpreted as complete. Further investigations of substrate use variation with 24 h observations and additional body size or life stage variation will provide species-specific habitat requirements and better understanding of stream assemblage structure.

Occurrence of Three Leech Species (Annelida: Hirudinida) on Fishes in the Kentucky River

ABSTRACT Leeches were collected from six fish species distributed among four of ten sites sampled. The leech species observed were Myzobdella reducta (Meyer 1940) and Myzobdella lugubris Leidy, 1851 of the family Piscicolidae and Placobdella pediculata Hemingway, 1908 of the family Glossiphoniidae. Attachment locations for Myzobdella lugubris included various sites in the buccal cavity of green sunfish [Lepomis cyanellus (Rafinesque)], largemouth bass [Micropterus salmoides (Lacepede)], and spotted bass [Micropterus punctulatus (Rafinesque)] and posterior to the eye of a largemouth bass. Attachment locations for Myzobdella reducta included on the caudal and pelvic fins of logperch [Percina caprodes (Rafinesque)] and the caudal and anal fin of spotfin shiners [Cyprinella spiloptera (Cope)] – a new host record. Attachment location observed for Placobdella pediculata was on the inside of the operculum of a freshwater drum [Aplodinotus grunniens (Rafinesque)]. This study established new host and attachment lo...

EMERGENT SANDBAR CONSTRUCTION FOR LEAST TERNS ON THE MISSOURI RIVER: EFFECTS ON FORAGE FISHES IN SHALLOW‐WATER HABITATS

ABSTRACTEmergent sandbars on the Missouri River are actively managed for two listed bird species, piping plovers and interior least terns. As a plunge‐diving piscivore, endangered least terns rely on ready access to appropriately sized slender‐bodied fish: <52 mm total length for adults and <34 mm total length for young chicks. As part of a multi‐agency recovery programme, aimed at enhancing nesting habitat for plovers and terns, the U.S. Army Corps of Engineers mechanically created several emergent sandbars on the Missouri River. However, it was unknown whether sandbar construction is a benefit or a detriment to forage abundance for least terns. Therefore, we studied the shallow‐water (<1.5 m) fish community near river and mechanically created emergent sandbars during three nesting seasons (2006–2008). We sampled every 2 weeks each year from late May to July within 15–16 areas to document the relative abundance, species richness and size classes of fish. Fish relative abundance was negatively related to depth. Catches were dominated by schooling species, including emerald shiner, sand shiner, spotfin shiner and bigmouth buffalo. Significant inter‐annual differences in relative abundance were observed, with generally increasing trends in intra‐seasonal relative abundance of shiners and the smallest size classes of fish (<34 mm). Significant differences in the fish communities between the sandbar types were not detected in this study. Results suggest that mechanical sandbar habitats host comparable fish communities at similar levels of relative abundance. Further analyses are required to evaluate if the levels of fish relative abundance are adequate to support least tern foraging and reproduction. Published in 2011 by John Wiley & Sons, Ltd.

Substrate and Current Velocity Preferences of Spotfin Shiner (Cyprinella spiloptera) and Sand Shiner (Notropis stramineus) in Artificial Streams

ABSTRACT We used artificial streams to quantify substrate choice for spotfin shiner (Cyprinella spiloptera) and sand shiner (Notropis stramineus). In Wabash River field surveys, spotfin shiner abundance did not vary with substrate variation, but sand shiner occurred in higher abundance at sites with increased sand substrate. Single and mixed species groups in artificial streams were presented with substrate (sand or hardpan) and flow choices (high flow/no flow). Neither species had substrate preferences in single species experiments. In single species experiments, sand shiner preferred no flow, and spotfin shiner selected high flow. In mixed species groups, sand shiner preferred high flow and sand substrate. However, spotfin shiner preferences for flow and substrate did not change when in mixed species groups. These results demonstrate that species-specific habitat selection behaviors are influenced by interactions within a fish assemblage.

Fish Hosts and Conglutinates of the Pyramid Pigtoe (Pleurobema rubrum)

Little information exists on the life history of Pleurobema rubrum (Pyramid Pigtoe). We determined fish hosts and made observations on the conglutinate release of Pyramid Pigtoe. From 2003 to 2005, fourteen Pyramid Pigtoe individuals were collected during mussel sampling on the Green River, KY and held in captivity. In June of 2006, one captive female was observed releasing conglutinates (water temperature was 22.5 °C). Nine fish species were exposed to Pyramid Pigtoe glochidia. After 12–15 days, transformation of glochidia to juveniles occurred on 4 species from the family Cyprinidae: Cyprinella spiloptera (Spotfin Shiner), Erimystax dissimilis (Streamline Chub), Lythrurus fasciolaris (Scarlet Shiner), and Notropis photogenis (Silver Shiner). All 4 are potentially natural hosts and Spotfin Shiner appears to be the most suitable host fish for propagation purposes.

Sexual Size Dimorphism and Ecomorphology of Spotfin Shiner (Cyprinella spiloptera) from the Wabash River Watershed

ABSTRACT We quantified body morphology in individuals from 49 collections of spotfin shiner (Cyprinella spiloptera) in the Wabash River watershed. Ten morphological measurements were used to produce principal component (PC) axes that were examined for relationships with watershed area. Analyses of males and females resulted in sexual dimorphism for one PC axis that represented caudal fin length and head depth; both have increased size in males. An analysis of body shape with watershed area resulted in different relationships for males and females. Caudal peduncle length increased with stream size for males and decreased with stream size for females. No significant relationships were found for sexual size dimorphism (SSD) with stream size. Allometry for SSD supported Rensch's rule—male body size increased more rapidly than female body size with increased SSD. Morphology in spotfin shiners is constrained by a combination of sexual selection and the hydrologic regime of the watershed.

Seasonal and Ontogenic Shifts in Microhabitat Selection by Fishes in the Shallow Waters of the Detroit River, a Large Connecting Channel

AbstractWe examined the relationship between microhabitat variables and fish distributions in a large connecting channel, the Detroit River. Fishes were sampled by boat seine at 60 sites in shallow (<2.5 m) Canadian waters in May, July, and September 2004. Length‐frequency distributions were used to separate species into small‐ and large‐species size categories. Fish–microhabitat associations were examined by applying canonical correspondence analysis separately for each season. Small fishes were often more strongly associated with microhabitat variables than large conspecifics. For example, small centrarchids were more strongly associated with complex macrophytes than large centrarchids in the spring; however, this pattern varied among seasons. We attribute the stronger microhabitat associations of small fishes to predator avoidance. Small‐bodied species also selected habitats that provided protection against predation: The spotfin shiner Cyprinella spiloptera preferred shallow water, and the round goby Neogobius melanostomus preferred coarse substrate. We observed a strong difference in microhabitat preferences between the small and large size categories of a species. Fish size played a greater role than season in determining fish–microhabitat associations. We found that macrophytes with a complex morphological structure were the most important factor in determining fish distributions in all seasons, while depth ranked second or third in importance. Fishes use an array of microhabitats in the Detroit River, and habitat heterogeneity is essential for promoting a diverse fish assemblage.

Larval Fish as Indicators of Reproductive Success in Unchannelized and Channelized Tributaries of the Red River Basin, Minnesota

ABSTRACT During 1998 and 1999, larval fish phenology, abundance, and diversity were characterized at 13 reaches in the Buffalo River and Sand Hill River, tributaries of the Red River of the North. Channelized reaches were less stable than unchannelized reaches, showing more overall variation and greater daily fluctuation in temperature and dissolved oxygen (DO), and a higher level of intermittent flow. These reaches also exhibited significantly lower larval diversity. Principal component analysis explained > 84% of the variance for the first two axes for larval catch, with axis 1 associated with channelization and axis 2 associated with temperature and DO. Fathead minnow (Pimephales promelas) was associated with channelized reaches, whereas spotfin shiner (Cyprinella spiloptera), common shiner (Luxilis cornutus), redhorse (Moxostoma spp.), and darters (Etheostoma spp.) were associated with unchannelized reaches in both years. Clear associations of reproductive guilds with channel type were not detected, but species of intermediate pollution tolerance were associated with unchannelized reaches and tolerant species were associated with channelized reaches.

Entrainment and impingement studies at two power plants on the Wabash River in Indiana

Abstract Fish entrainment and impingement studies were conducted at Cayuga and Wabash River generating Stations in 1987 and 1988, respectively. Concurrent river samplings were conducted upstream from the stations to assess adult fish and ichthyoplankton populations. The original 316(b) studies at these stations were conducted in 1976–1977 and concluded that the stations were having minimal adverse impact on the Wabash River fish community. The state regulatory agency did not agree with this interpretation and requested the subsequent 1987 and 1988 studies. The major issue at these once-through cooling power plants was the large water withdrawals at Cayuga and Wabash River Stations [1318 and 1096 cubic feet per second (cfs) maximum plant flows, respectively], in contrast to the relatively low average annual Wabash River flows (10,070 and 11,110 cfs, respectively). The close proximity of the stations (35 river miles apart) together with the high percentage of water withdrawn suggest that the potential risk of unacceptable impacts is high. The six-month impingement estimates for Cayuga and Wabash River Stations were 15,086 and 11,401 fish, respectively. Impingement catches at both stations were dominated by young-of-the-year (YOY) channel catfish and gizzard shad. In addition, small minnows (primarily bullhead minnow and emerald shiners) were commonly impinged at Cayuga Station. Minnows (predominantly spotfin shiner, bullhead minnow and emerald shiner) were also the dominant species in the river samplings upstream from the stations. In the entrainment samplings, an estimated 26,920,382 and 107,503,876 fish eggs and larvae were entrained each year at Cayuga and Wabash River Stations, respectively. Ictiobinae (buffaloes and carpsuckers) and Cyprinidae (minnows and shiners) were the dominant ichthyoplankton in the river. Approximately 3.5 and 23% of the total river ichthyoplankton were entrained at Cayuga and Wabash River Stations, respectively. Gizzard shad at Cayuga Station, and Ictiobinae and Cyprinidae at Wabash River Station (WRS) were the dominant taxa entrained by the stations. Unusually low river flows during the spring and summer of 1987 and 1988 provided worst-case conditions for entrainment and impingement at the stations. However, the relatively low impingement and entrainment numbers during these worst-case conditions indicated that these stations were not adversely affecting the Wabash River fish community.

Predator response to releases of American shad larvae in the Susquehanna River basin

Abstract— Predation on American shad (Alosa sapidissima) larvae within the first two hours of release was examined from 1989 to 1992 on 31 occasions at stocking sites in the Susquehanna River basin. Twenty‐two fish species consumed shad larvae; the dominant predators were spotfin shiner (Cyprinella spiloptera), mimic shiner (Notropis volucellus) and juvenile smallmouth bass (Micropterus dolomieu). The number of shad larvae found in predator stomachs ranged from 0 to 900. Mortality of shad larvae at the stocking site was usually less than 2%. The greatest mortality (9.6%) occurred at the highest stocking level (1.5 million larvae). Highly variable predation rates and release levels of shad insufficient to achieve predator satiation hindered the ability to determine a specific type of functional response of predators. Predator numbers increased with stocking density, indicating short‐term aggregation at the release site. Because of practical problems associated with releasing the large numbers of larvae that would be required to satiate predators, routine stocking at these levels is probably unreasonable. Releases of 400,000 to 700,000 larvae may reduce predation by offsetting depensatory mechanisms that operate on small releases and the effects of increased predation due to predator aggregation on large releases. Night stocking may reduce predation on larval shad at the release site.

Impingement and Entrainment of Fishes Within a High Volume-Low Velocity Deep Water Intake System on Lake Michigan

ABSTRACT We determined the extent of fish entrainment and impingement for a low velocity-high volume Lake Michigan water intake system where the entrance of the intake system occurred in deep waters. There was no evidence of any fish entrainment probably because of the location of the entrance to the water intake system. Fish impingement was also low and comparable to the lowest impingement found for power plant intakes. The number of impinged fish was 93 fishes for 58 sampling dates from April 23 to November 13. Of the 93 fishes, 61 were alewives, 11 were yellow perch, an the remainder included black crappie, black bullhead, bloater, bluegill, emerald shiner, johnny darter, pumpkinseed, slimy sculpin, and spotfin shiner. The impact of this intake systemon the fish community was insignificant, since the estimated total of impinged fishes during the operating season of the intake was 280.

Evolutionary dynamics of tandem repeats in the mitochondrial DNA control region of the minnow Cyprinella spiloptera.

Length variation due to tandem repeats is now recognized as a common feature of animal mitochondrial DNA; however, the evolutionary dynamics of repeated sequences are not well understood. Using phylogenetic analysis, predictions of three models of repeat evolution were tested for arrays of 260-bp repeats in the cyprinid fish Cyprinella spiloptera. Variation at different nucleotide positions in individual repeats supported different models of repeat evolution. One set of characters included several nucleotide variants found in all copies from a limited number of individuals, while the other set included an 8-bp deletion found in a limited number of copies in all individuals. The deletion and an associated nucleotide change appear to be the result of a deterministic, rather than stochastic, mutation process. Parallel origins of repeat arrays in different mitochondrial lineages, possibly coupled with a homogenization mechanism, best explain the distribution of nucleotide variation.