Clay L. Pierce

Growth and Survival of Larval Fishes: Roles of Competition and Zooplankton Abundance

Abstract -Interactions among larval gizzard shad Dorosoma cepedianum, bluegills Lepomis macrochirus, and their zooplankton prey were examined in a controlled mesocosm experiment and by field sampling. In the mesocosm experiment, gizzard shad growth and survival were negatively correlated with gizzard shad density and positively correlated with macrozooplankton prey. Bluegill growth was positively correlated with prey availability, but survival was uniformly high despite differences in zooplankton abundance and fish density. Macrozooplankton and copepod biomasses were negatively correlated with fish density. In Lake Shelbyville, co-occurrence of larval gizzard shad and bluegills in the limnetic zone was limited to a 3-week period, and the period of greatest larval gizzard shad abundance preceded the appearance of bluegills. Zooplankton abundance declined greatly after the peak in larval gizzard shad abundance and remained low when bluegills were present. Growth rates of gizzard shad were highest early and ...

Behavior and Ecological Interactions of Larval Odonata

Enallagma aspersum and E. traviatum (Odonata: Coenagrionidae) are the most abundant larval odonates in Bays Mountain Park (Sullivan County, Tennessee, USA), although their spatial distributions are essentially nonoverlapping. E. traviatum coexists with insectivorous fish in a small lake, whereas E. aspersum is restricted to a small fishless pond nearby. Behavioral observations revealed that E. aspersum larvae were more active than E. traviatum, and tended to occupy more conspicuous positions. E. aspersum also enganged in more confrontations than E. traviatum, especially at higher density. In laboratory experiments with juvenile bluegills (Lepomis macrochirus) as predators, E. aspersum larvae were more vulnerable to predation than E. traviatum. Red—spotted newts (Notophthalmus viridescens) also preyed on E. aspersum disproportionately. Field enclosure experiments revealed that dry mass of individual E. aspersum larvae was density dependent, and that increased density of E. aspersum or addition of E. traviatum produced similar reductions. Competition was asymmetrical, as E. aspersum appeared to have no significant effect on E. traviatum. The substantial increase in confrontations among E. aspersum larvae at higher density, and the lack of evidence for prey depletion, suggest that interference may be the mechanism of competition. Our results suggest that the distribution of E. aspersum larvae may be limited by fish predation, but although competitive interactions were detected, we have no evidence that larval competition influences the distribution of either species.

Predator avoidance, microhabitat shift, and risk-sensitive foraging in larval dragonflies

SummaryDragonfly larvae (Odonata: Anisoptera) are often abundant in shallow freshwater habitats and frequently co-occur with predatory fish, but there is evidence that they are underutilized as prey. This suggests that species which successfully coexist with fish may exhibit behaviors that minimize their risk of predation. I conducted field and laboratory experiments to determine whether: 1) dragonfly larvae actively avoid fish, 2) microhabitat use and foraging success of larvae are sensitive to predation risk, and 3) vulnerability of larvae is correlated with microhabitat use. I experimentally manipulated the presence of adult bluegills (Lepomis macrochirus) in defaunated patches of littoral substrate in a small pond to test whether colonizing dragonfly larvae would avoid patches containing fish. The two dominant anisopteran species, Tetragoneuria cynosura and Ladona deplanata (Odonata: Libellulidae), both strongly avoided colonizing patches where adult bluegills were present. Laboratory experiments examined the effects of diel period and bluegills on microhabitat use and foraging success, using Tetragoneuria, Ladona and confamilial Sympetrum semicictum, found in a nearby fishless pond. Tetragoneuria and Ladona generally occupied microhabitats offering cover, whereas Sympetrum usually occupied exposed locations. Bluegills induced increased use of cover in all three species, and use of cover also tended to be higher during the day than at night. Bluegills depressed foraging in Tetragoneuria and to a lesser extent in Ladona, but foraging in Sympetrum appeared unaffected. Other laboratory experiments indicated that Sympetrum were generally more vulnerable than Tetragoneuria or Ladona to bluegill predation, and that vulnerability was positively correlated with use of exposed microhabitats. Both fixed (generally low use of exposed microhabitats, diel microhabitat shifts) and reactive (predator avoidance, predator-sensitive microhabitat shifts) behavioral responses appear to reduce risk of predation in dragonfly larvae. Evidence indicates that vulnerability probably varies widely among species and even among instars within species, and suggests that spatial distributions of relatively vulnerable species may be limited by their inability to avoid predation.

Hydrological Alteration along the Missouri River Basin: A Time Series Approach

Abstract. Human alteration of large rivers is commonplace, often resulting in significant changes in flow characteristics. We used a time series approach to examine daily mean flow data from locations throughout the mainstem Missouri River. Data from a pre-alteration period (1925–1948) were compared with a post-alteration period (1967–1996), with separate analyses conducted using either data from the entire year or restricted to the spring fish spawning period (1 April–30 June). Daily mean flows were significantly higher during the post-alteration period at all locations. Flow variability was markedly reduced during the post-alteration period as a probable result of flow regulation and climatological shifts. Daily mean flow during the spring fish spawning period was significantly lower during the post-alteration period at the most highly altered locations in the middle portion of the river, but unchanged at the least altered locations in the upper and lower port ions of the river. Our data also corroborate other analyses, using alternate statistical approaches, that suggest similar changes to the Missouri River system. Our results suggest human alterations on the Missouri River, particularly in the middle portion most strongly affected by impoundments and channelization, have resulted in changes to the natural flow regime.

Empirical Assessment of Indices of Prey Importance in the Diets of Predacious Fish

Abstract Determining the importance of prey taxa in the diets of predacious species is a frequent objective in fisheries research. Various indices of prey importance are in common use, and all give different results because of their emphasis on different aspects of fish diets. We explored these differences by empirically comparing four well-known indices—percent weight (%W), percent occurrence (%O), percent number (%N), and percent index of relative importance (%IRI)—as well as a modified %IRI (%MIRI), as applied to an extensive data set on the diets of six fish species in Spirit Lake, Iowa. Correlations among all indices were positive but were weaker among component indices (%W, %O, and %N) than between the two compound indices (%IRI and %MIRI); correlations among component indices were also weaker than correlations of compound with component indices. Correlation strength of %MIRI with the three component indices varied greatly (%N < %O < %W), whereas the correlation strength of %IRI with component indic...

Potential Influence of Harvest on Shovelnose Sturgeon Populations in the Missouri River System

Abstract The collapse of the European and Asian caviar industry has raised concern about the overexploitation of shovelnose sturgeon Scaphirhynchus platorynchus in the Missouri River. Unfortunately, little is known about the potential effects of harvest on the population dynamics of this species. Therefore, this study was conducted to describe the population characteristics (e.g., growth, longevity, and mortality) and to determine the influence of exploitation and harvest regulations (minimum length limits) on the yield, size structure, and egg production of shovelnose sturgeon from three sites in the Missouri River using a Beverton–Holt equilibrium model. Despite differences in the population characteristics (e.g., growth and longevity) of shovelnose sturgeon among sites, all populations responded similarly to harvest at the conditional natural mortality rates (death rate in the absence of harvest) used in our simulations (i.e., 5% and 20%). Our simulations of yield indicated that growth overfishing (i.e...

Pesticide concentrations in frog tissue and wetland habitats in a landscape dominated by agriculture

Habitat loss and exposure to pesticides are likely primary factors contributing to amphibian decline in agricultural landscapes. Conservation efforts have attempted to restore wetlands lost through landscape modifications to reduce contaminant loads in surface waters and providing quality habitat to wildlife. The benefits of this increased wetland area, perhaps especially for amphibians, may be negated if habitat quality is insufficient to support persistent populations. We examined the presence of pesticides and nutrients in water and sediment as indicators of habitat quality and assessed the bioaccumulation of pesticides in the tissue of two native amphibian species Pseudacris maculata (chorus frogs) and Lithobates pipiens (leopard frogs) at six wetlands (3 restored and 3 reference) in Iowa, USA. Restored wetlands are positioned on the landscape to receive subsurface tile drainage water while reference wetlands receive water from overland run-off and shallow groundwater sources. Concentrations of the pesticides frequently detected in water and sediment samples were not different between wetland types. The median concentration of atrazine in surface water was 0.2 μg/L. Reproductive abnormalities in leopard frogs have been observed in other studies at these concentrations. Nutrient concentrations were higher in the restored wetlands but lower than concentrations thought lethal to frogs. Complex mixtures of pesticides including up to 8 fungicides, some previously unreported in tissue, were detected with concentrations ranging from 0.08 to 1,500 μg/kg wet weight. No significant differences in pesticide concentrations were observed between species, although concentrations tended to be higher in leopard frogs compared to chorus frogs, possibly because of differences in life histories. Our results provide information on habitat quality in restored wetlands that will assist state and federal agencies, landowners, and resource managers in identifying and implementing conservation and management actions for these and similar wetlands in agriculturally dominated landscapes.

Seasonal Distribution, Aggregation, and Habitat Selection of Common Carp in Clear Lake, Iowa

Abstract The common carp Cyprinus carpio is widely distributed and frequently considered a nuisance species outside its native range. Common carp are abundant in Clear Lake, Iowa, where their presence is both a symptom of degradation and an impediment to improving water quality and the sport fishery. We used radiotelemetry to quantify seasonal distribution, aggregation, and habitat selection of adult and subadult common carp in Clear Lake during 2005-2006 in an effort to guide future control strategies. Over a 22-month period, we recorded 1,951 locations of 54 adults and 60 subadults implanted with radio transmitters. Adults demonstrated a clear tendency to aggregate in an offshore area during the late fall and winter and in shallow, vegetated areas before and during spring spawning. Late-fall and winter aggregations were estimated to include a larger percentage of the tracked adults than spring aggregations. Subadults aggregated in shallow, vegetated areas during the spring and early summer. Our study, w...

Diet dynamics of the juvenile piscivorous fish community in Spirit Lake, Iowa, USA, 1997-1998

Pelham ME, Pierce CL, Larscheid JG. Diet dynamics of the juvenile pisM. E. Pelham1*, C. L. Pierce1, civorous fish community in Spirit Lake, Iowa, USA, 1997–1998. J. G. Larscheid2 Ecology of Freshwater Fish 2001: 10: 198–211. C Munksgaard, 2001 1U.S. Geological Survey – Biological Resources Division, Iowa Cooperative Fish and Wildlife Abstract – We assessed temporal dynamics and variation among species Research Unit, Department of Animal Ecology, and age-classes in the diets of age 0 and age 1 piscivorous fish species in Iowa State University, Ames, Iowa, 2Iowa Spirit Lake, Iowa, USA during 1997 and 1998. Species included walleye Department of Natural Resources, Spirit Lake, Iowa, USA Stizostedion vitreum, yellow perch Perca flavescens, smallmouth bass *Present address: Minnesota Department of Micropterus dolomieui, largemouth bass Micropterus salmoides, black Natural Resources, Montrose Area Fisheries, crappie Pomoxis nigromaculatus and white bass Morone chrysops. Thirty 7372 State Highway 25 SW, Montrose, taxa were identified in diets, including 12 species of fish. We found draMinnesota 55363, USA matic differences in diets among species, among age-classes within species and over time. Walleye, largemouth bass, smallmouth bass and white bass were piscivorous at age 0. Black crappie began piscivory at age 1. Yellow perch also began piscivory at age 1, but fish were a very small fraction of age-1 diets. The primary temporal pattern, seen in several species and ageclasses, was an increase in piscivory from spring to fall. This pattern was due to the lack of small, age-0 prey fish in spring. Although some patterns were evident, the taxonomic composition of the diets of all species was highly variable over time, making generalizations difficult. A surprising

Back-Calculation of Fish Length from Scales: Empirical Comparison of Proportional Methods

Abstract We compared three proportional back-calculation methods for scales using data sets for pumpkinseeds Lepoinis gibbosus and golden shiners Notemigonus crysoleucas from 10 southern Quebec lakes, and we validated back-calculations by comparing them with observed lengths at time of annulus formation. Ordinary least-squares regression (OR) was compared with geometric mean regression (GMR) for describing body–scale relationships. Although minor differences were detected in body–scale regressions among lakes, pooling data across lakes yielded linear body–scale relationships with very high r 2. Differences between OR and GMR body–scale relationships were negligible in both species. Likewise, all back-calculation methods produced equivalent results. Back-calculated lengths generally corresponded well with observed lengths in all pumpkinseeds age-classes and in golden shiners older than l year. Observed lengths were often greater than back-calculated lengths for age-1 golden shiners. Our results, indicating...