bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing results of a spatially explicit growth model with changes in the length-weight relationship of lake trout (Salvelinus namaycush) in Flaming Gorge Reservoir
Authors: Luecke Chris , Wengert M William , Schneidervin Roger W
Published: April 2011

We employed a spatially explicit simulation model to assess growth rate potential for lake trout (Salvelinus namaycush) in Flaming Gorge Reservoir, Utah-Wyoming. Late-summer water temperatures and forage fish densities in 168 habitat cells were collected from 1989 to 1996 and were used to estimate the potential growth of lake trout inhabiting each cell. Results of model simulations indicated that habitat quality for lake trout growth had decreased from 1990 to 1993. This decrease in lake trout growth rate potential was related to decreased forage fish densities during this period. Lake trout condition, as measured using length-weight analyses of individuals captured in spring gillnetting surveys, also decreased from the early 1990s to the mid-1990s. The change in the slope of the length-weight relationship was correlated with the proportion of habitat cells containing positive simulated growth rate potentials (r2 = 0.60, p = 0.024). No significant correlation between the sum of growth rate potentials in habitat cells and changes in the slope of the length-weight relationship was apparent. These correlations suggest that spatially explicit models of habitat quality have relevance to the performance of individual organisms functioning in field environments.
Temporal and spatial variability of 13C/12C and 15N/14N in pelagic biota of Prince William Sound, Alaska
Authors: Kline, Jr. Thomas C
Published: April 2011

Stable isotope ratios of carbon and nitrogen were used to identify seasonal and spatial patterns in carbon and nitrogen and to determine source of energy (Prince William Sound (PWS) versus the Gulf of Alaska (GOA)) for juvenile fishes in PWS. PWS-wide samples of bulk net zooplankton (all noncalcareous zooplankton collected in 335-µm-mesh nets), individual late copepodid stage of the large herbivore Neocalanus cristatus, juvenile Pacific herring (Clupea pallasi), and juvenile walleye pollock (Theragra chalcogramma) were collected in spring, summer, and fall in 1994 and 1995. For bulk zooplankton and N. cristatus, there was a strong 13C/12C gradient but weak 15N/14N gradient within PWS and GOA. Zooplankton 15N/14N was positively correlated with 13C/12C during the phytoplankton bloom but was not correlated during the zooplankton bloom, suggesting a decoupling of nitrogen and carbon cycles. Plankton isotopic signatures suggested a diagnostic 13C/12C for GOA carbon. For juvenile fishes and diapausing copepods in PWS, 13C/12C varied between years, suggesting that the origin of carbon differed between years (GOA more so in 1995 than in 1994). Use of a natural stable isotope tracer provided evidence for biophysical coupling via inferred fluctuations in oceanographic processes.
New perspectives in the analysis of fish distributions: a case study on the spatial distribution of largemouth bass (Micropterus salmoides)
Authors: Essington Timothy E , Kitchell James F
Published: April 2011

Analyses of fish distributions rarely account for spatial arrangement of habitat types, are typically conducted at a single scale, and use a null model of random distributions without considering other null models. This study demonstrates a procedure to circumvent these difficulties by analyzing telemetry data collected on largemouth bass (Micropterus salmoides) in Long Lake, Michigan. Bass were highly aggregated within the littoral region, showing peaks of aggregation at small (<60 m) and large (>160 m) spatial scales. A neutral movement model (no taxis or kinesis within habitat types) could explain some of the observed aggregation, yet substantial aggregation remains unexplained. Much of the large-scale aggregation could be generated by including a taxis towards the eastern half of the basin, but taxes towards shallower cells or cells containing woody emergent macrophytes were unable to generate the observed degree of small-scale aggregation. Our results highlight the utility of analyzing spatial distributions at multiple scales and the importance of the spatial arrangements of habitat types and suggest that nonrandom distributions at one scale may be due to processes occurring at different scales.
Estimating diel, depth-specific foraging opportunities with a visual encounter rate model for pelagic piscivores
Authors: Beauchamp David A , Baldwin Casey M , Vogel Jason L , Gubala Chad P
Published: April 2011

We developed a visual foraging model for piscivores that predicts search volume as a function of light and turbidity. We combined this model with diel hydroacoustic measurements of depth-specific prey fish densities during summer stratification in Lake Tahoe, Lake Washington, and Strawberry Reservoir to examine differences in diel, depth-specific visual encounter rates of prey. These study sites were selected to represent gradients of increasing limnetic prey fish density and declining transparency. The model predicted over a 30-fold difference in maximum depth-specific diel encounter rates among the three lakes. Lake Washington, which was characterized by intermediate transparency and moderate limnetic prey density, had the highest predicted prey encounter rates. The pattern of prey encounter rates among the three lakes was similar to the proportional contribution of limnetic prey fishes observed in the diet of piscivores from these waters. This approach may be used to construct temporally and spatially explicit trophic interaction models for examining mechanisms underlying predator and prey distributions or to predict the response of existing or introduced predators to changing environmental conditions, prey abundance, or distribution.
Simulated dispersal of exotic rainbow smelt (Osmerus mordax) in a northern Wisconsin lake district and implications for management
Authors: Hrabik Thomas R , Magnuson John
Published: April 2011

We simulated geographic dispersal of exotic rainbow smelt (Osmerus mordax) as a function of present introduction rates, the probability of invasion through stream connections among lakes and watersheds, and survival based on physical and chemical factors of lakes within a northern Wisconsin watershed. One fourth of the habitable lakes contained rainbow smelt after 1000 years if dispersal was restricted to stream corridors. In contrast, with present rates of human transport, half contained rainbow smelt after 200 years, three quarters after 300 years, and all after 1000 years. Simulated human introductions increased the number of epicenters for spread and were the most influential parameter in the model. Stream connections between lakes increased the number of lakes colonized; decreases in migration ability led to fewer invaded lakes. Although extinction was operating, human introductions outweighed extinction and led to a saturation of rainbow smelt across all habitable lakes within the watershed within 1000 years. Our results highlight the importance of human vectors in driving exotic fish dispersal, suggest that isolated lakes are important refuges for species negatively affected by rainbow smelt, and show that agencies interested in controlling the spread of exotic fishes need to strongly consider the human vector of transport.
Demographic analysis of gummy shark (Mustelus antarcticus) and school shark (Galeorhinus galeus) off southern Australia by applying a generalized Lotka equation and its dual equation
Authors: Xiao Yongshun , Walker Terence I
Published: April 2011

Although Lotka's equation is commonly used for calculating the intrinsic rate of increase with time of a fish population in demographic analysis, its dual equation has never been derived. In this paper, we establish an explicit relationship between the intrinsic rate of increase with time of a fish population and its instantaneous rate of natural mortality from an age-dependent population dynamics model, derive a generalized Lotka equation for calculating the intrinsic rate of increase with time, and derive its dual equation for calculating the intrinsic rate of decrease with age. The virginal intrinsic rate of increase with time of the gummy shark (Mustelus antarcticus) population was calculated as 0.115957·year-1 and its intrinsic rate of decrease with age as -0.312957·year-1. The virginal intrinsic rate of increase with time of the school shark (Galeorhinus galeus) population was calculated as 0.109480·year-1 and its intrinsic rate of decrease with age as -0.216980·year-1. The generalized Lotka equation and its dual equation thus derived imply that both reproductive schedules of a population of animals and its instantaneous rate of total mortality determine its intrinsic rate of increase with time, whereas its reproductive schedules alone determine its intrinsic rate of decrease with age.
Influence of ingestion rate and food types on cadmium accumulation by the aquatic insect Chaoborus
Authors: Munger Catherine , Hare Landis
Published: April 2011

We measured the influence of two food-related variables, prey type and ingestion rate, on Cd uptake by larvae of the aquatic insect Chaoborus punctipennis. Larvae collected from a low-Cd lake (0.1 nM total dissolved Cd) were held in the laboratory where they were exposed to water and to various quantities of either copepods (Diaptomus minutus) or cladocerans (Diaphanosoma birgei) from a high-Cd lake (1 nM total dissolved Cd). The Cd content of larvae exposed to the metal in water only did not increase, confirming the results of previous experiments in which food was demonstrated to be the major Cd source for C. punctipennis larvae. Prey type did not influence predator Cd content, likely because Cd concentrations in the two prey types were approximately the same (~10 µg Cd·g-1) and because Cd was assimilated with the same efficiency by the predator from the two prey types. Cadmium assimilation efficiencies were greater at low prey ingestion rates (nearly 100%) than at high prey ingestion rates (~30%), which is likely explained by a shorter residence time of food in the gut at high prey consumption rates.
Effect of local sources on metal concentrations in littoral sediments and aquatic macroinvertebrates of the St. Lawrence River, near Cornwall, Ontario
Authors: Filion Alain , Morin Antoine
Published: April 2011

Concentrations of Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn were measured in surface sediments and in five aquatic macroinvertebrate taxa to assess metal contamination in ecologically important but understudied shallow littoral areas of the St. Lawrence River, near Cornwall, Ontario, and to test for the effect of local point sources. Metal concentrations in littoral sediments were generally below the lowest effect level of the Ontario provincial sediment quality guidelines and were positively related to the proportion of fine particles and of organic matter in sediments. Analyses of the spatial distribution of metal concentrations in sediments and macroinvertebrates showed that local sources of Hg and Zn had contributed to the contamination of littoral sediments and macroinvertebrates. Concentrations of Cr, Fe, Ni, and Zn in chironomids and oligochaetes were similar or higher than levels reported for deeper sites in the Cornwall area, despite the much lower concentrations in littoral sediments, suggesting a higher bioavailability of metals in littoral than in deeper sediments. Although the effect of local point sources of metals was still detectable in 1994, the comparison with Ontario sediment quality guidelines and with other sites in the Great Lakes - St. Lawrence ecosystem suggests that metal contamination of littoral sediments and invertebrates was relatively low.
Ranking the effects of site exposure, plant growth form, water depth, and transparency on aquatic plant biomass
Authors: Hudon Christiane , Lalonde Sophie , Gagnon Pierre
Published: April 2011

The maximum depth of macrophyte colonization and depth distribution of macrophyte biomass were assessed over 3 years, in late summer, at six sites in the St. Lawrence River and two sites in the Ottawa River (Lake des Deux Montagnes). Maximum depth of submerged plant colonization could be predicted from the light extinction coefficient (r2 = 0.82) and Secchi disk depth (r2 = 0.80). The aboveground and total biomass of macrophytes were related to a variety of environmental variables as follows in descending order of importance: exposure to wind and waves, plant growth forms, water depth, and light intensity. Together, these variables accounted for 67 and 74% of sampling variability of aboveground and total biomass, respectively. These environmental variables were used to elaborate hierarchical predictive models of aboveground and total biomass of emergent and submerged macrophytes. The empirical relationship that links St. Lawrence River and Ottawa River aquatic plants to environmental variables may eventually allow us to forecast wetland response to changes in water levels and water clarity resulting from climate variability and (or) discharge regulation.
Declivity in steelhead (Oncorhynchus mykiss) recruitment at the Keogh River over the past decade
Authors: Ward Bruce R
Published: April 2011

Survival and return of unharvested winter-run steelhead (Oncorhynchus mykiss) at the Keogh River, British Columbia, declined abruptly and remained persistently low after 1990. Adult returns averaged 1168 fish from 1976 to 1990 but were significantly lower from 1991 to 1998 (mean 223). Forty wild females returned to the 35-km river in 1995-1996, 20 in 1996-1997, and <10 in 1997-1998. The positive linear relationship between smolts and returns was significantly lower after 1990 and no longer correlated with smolt size. Smolt-to-adult survival averaged 15% (1976 to 1989) but recently averaged 3.5% (1990 to 1995). Smolt number steadily declined to <1000 by 1998 from an average annual count of 7000. Smolts per spawner from 1991 to 1994 were, on average, 70% lower than previous estimates based on the same spawner abundance. Recruitment scenarios based on survival histories during freshwater and marine life stages indicated that adult recruits are currently below replacement and unsustainable if conditions continue or worsen. Factors influencing steelhead in the ocean and freshwater are likely similar for other salmonids; harvest impacts must be reduced and appropriate stock rebuilding measures implemented.
Distribution and transformation of elemental mercury in the St. Lawrence River and Lake Ontario
Authors: Amyot Marc , Lean David RS , Poissant Laurier , Doyon Marie-Renée
Published: April 2011

Elemental Hg (Hg0) is a volatile species that is responsible for water-to-air transfer of Hg in Lake Ontario and the St. Lawrence River. We conducted two cruises in 1998 to identify spatial and temporal patterns in Hg0 levels in these systems and performed field and laboratory experiments on redox transformations of Hg. Elemental Hg concentrations were higher in Lake Ontario than in the St. Lawrence River. At stations in Lake Ontario, Hg0 levels were higher at the bottom of the water column than at the surface, whereas they were homogeneous throughout the water column of the river. Elemental Hg concentrations were generally higher in July than in September and, in contrast with experiments on inland lakes, were relatively constant during the day except for a narrow peak at sunrise. Field and laboratory experiments showed that photoreduction of Hg(II) in St. Lawrence River water was substrate limited and was influenced by visible and ultraviolet radiation. Pseudo first-order kinetics best described photoreduction, with k values between 1 and 2·h-1.
Population differences in the onset of cranial ossification in pumpkinseed (Lepomis gibbosus), a potential cost of rapid growth
Authors: Arendt Jeffrey D , Wilson David S
Published: April 2011

Interspecific comparisons suggest that a trade-off exists between development and somatic growth rate. We provide evidence for a trade-off between cranial ossification and growth rate within a single species, the pumpkinseed sunfish (Lepomis gibbosus). We compare fish derived from two populations known to differ in their somatic growth rates. Fish were hatched from eggs and maintained under common conditions. Juveniles were sampled weekly through the first 8 weeks after hatching, preserved, and stained to determine the onset of ossification of superficial cranial bones. Fish from both populations showed a similar pattern of ossification in the cranial bones, but fish from the fast-growth population showed an average delay of 2 days in the onset of ossification for each bone. As a result, the fast-growth fish were both older and larger at each stage of ossification. We suggest that such a delay in ossification may have fitness effects through feeding ability, swimming ability, and (or) defense against predators.
Cytochrome P450 1A and related measurements in juvenile chinook salmon (Oncorhynchus tshawytscha) from the Fraser River
Authors: Wilson J Y , Addison R F , Martens D , Gordon R , Glickman B
Published: April 2011

Juvenile chinook salmon (Oncorhynchus tshawytscha) were captured at six sites on the upper Fraser, Nechako, and Thompson rivers, British Columbia, Canada. Biological responses were measured in the liver to assess the effects of contaminants on the fish before they began migration downstream. Both ethoxyresorufin-O-deethylase (EROD) activity and CYP 1A concentrations were significantly enhanced, being two- to three-fold higher in Fraser River samples compared with those fish from reference sites on the Nechako River. DNA adduct concentrations were two- to four-fold higher in Fraser River fish, although liver histopathology appeared unaffected. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) in the carcasses contributed to total contaminant burdens of less than 1 pg·g-1. Polycyclic aromatic hydrocarbon (PAH) metabolites were undetectable in nearly all samples of bile. There were strong correlations between EROD activity, CYP 1A induction, and DNA adduct concentrations but no clear correlation between these responses and PCDD, PCDF, or PCB concentrations.
Trends in wild adult steelhead (Oncorhynchus mykiss) abundance for coastal regions of British Columbia support the variable marine survival hypothesis
Authors: Smith Barry D , Ward Bruce R
Published: April 2011

Wild adult steelhead (Oncorhynchus mykiss) abundance for rivers in British Columbia was indexed using catch-per-angler-day (CpAD) calculated from data obtained using an angler questionnaire. Mean annual CpAD for primarily winter-run steelhead in rivers of four rainfall-driven coastal regions of British Columbia showed similar trends from the fiscal year 1967-1968 to 1989-1990. After 1989-1990 the trends diverged. The generally remote rivers of the west coast of Vancouver Island and the Queen Charlotte Islands maintained a steady or increasing trend in CpAD after 1989-1990. The long-term trend for these two regions correlated well with a joint index of winter and summer upwelling for the Coastal Upwelling Domain for the years that steelhead are at sea and is consistent with studies that relate marine survival of salmon to oceanic-atmospheric climate. In contrast with west coast Vancouver Island and the Queen Charlotte Islands, most rivers of the east coast of Vancouver Island and the lower mainland near Vancouver revealed declining trends since 1989-1990. Most of these rivers drain into the Strait of Georgia. Reasons for the discrepancy among regions after about 1990 are discussed. They include high angling pressure related to hatchery supplementation, differences in riverine and marine conditions, and smolt migration distance.
A dynamic programming model of fishing strategy choice in a multispecies trawl fishery with trip limits
Authors: Babcock Elizabeth A , Pikitch Ellen K
Published: April 2011

Dynamic programming was used to model targeting decisions made by bottom trawling vessels in the U.S. west coast groundfish fishery, under management-imposed limits on landings of each target species (trip limits). A model of choice of assemblage (bottom rockfish (Sebastes sp.) versus deepwater Dover sole (Microstomus pacificus) complex) within a fishing trip was parameterized with data from an observer study conducted in 1988 through 1990. The model predicted that the vessel would fish the bottom rockfish strategy exclusively without limits but would switch between strategies several times under restrictive trip limits. That higher limits increased switching was consistent with actual landings from trips made by the same vessels under the same trip limit regimes, although the actual landings were more variable. Different trip limits or different market prices for the limited species changed the predicted decisions. Changing the cost of fishing each strategy, probability of a premature trip ending, tow duration, and time between tows also changed the predicted decisions, but the input parameters had to be well outside the range of values observed in the fishery.
Metal exposure in a benthic macroinvertebrate, Hydropsyche californica, related to mine drainage in the Sacramento River
Authors: Cain Daniel J , Carter James L , Fend Steven V , Luoma Samuel N , Alpers Charles N , Taylor Howard E
Published: April 2011

A biomonitoring technique was employed to complement studies of metal transport in the upper Sacramento River affected by acid mine drainage. Metals (Al, Cd, Cu, Fe, Hg, Pb, and Zn) were determined in a resident invertebrate, Hydropsyche californica (Insecta: Trichoptera), and streambed sediments (<62 µm) to assess metal contamination within a 111-km section of the river downstream of the mining area. Metals in H. californica also were interpreted to be broadly indicative of metal exposure in fish. Total Hg was determined in the whole body of the insect, whereas Al, Cd, Cu, Fe, Pb, and Zn were additionally separated into operationally defined cytosolic (used as an indicator of exposure to bioavailable metal) and particulate fractions. Total concentrations of Cd, Cu, Hg, Pb, and Zn in sediments were consistent with documented upstream sources of acid mine drainage. Metal distribution patterns in H. californica and sediments were generally consistent for Cd, Cu, and Pb but inconsistent for Hg and Zn. Concentrations in H. californica indicated that bioavailable Cd, Cu, Pb, and Zn was transported at least 120 km downstream of the mine sources. Zinc in H. californica was elevated, but unlike sediments, did not decrease downstream. Mercury in H. californica was not elevated.
Genetic relationships among populations of northern pike (Esox lucius)
Authors: Senanan Wansuk , Kapuscinski Anne R
Published: April 2011

We assessed genetic variation, using microsatellite markers, in 14 populations of northern pike (Esox lucius) in the North Central United States and in six populations from Quebec, Alaska, Siberia, and Finland. Eight of 13 loci examined were polymorphic in at least one population with an average heterozygosity at all loci and across all populations of 0.14. The Rstand Fstvalues indicated differentiation among populations (Rst= 0.61, Fst= 0.42). Although microsatellite variation found in northern pike was much lower than that found in sympatric and other fish species, the polymorphisms differentiated populations of greater geographical proximity than was possible in prior studies using allozymes and mitochondrial DNA. We generated UPGMA-clustering phenograms based on five genetic distance measures with 2000 bootstrap replicates per measure. All measures yielded highly repeatable population structure between continents (supporting values = 92.4-100%) and within Finland (42.3-98%). Four measures differentiated the Alaskan population and Young Lake (Great Lakes drainage) from other North American populations (56.6-87.7%). Relationships among other North Central United States populations were unclear, as indicated by low supporting values. Results support the hypotheses of one refugium in the North Central United States and more than one refugium in Europe during the last glaciation.
Estimating food consumption rates of fish using a mercury mass balance model
Authors: Trudel Marc , Tremblay Alain , Schetagne Roger , Rasmussen Joseph B
Published: April 2011

We present a simple method for estimating food consumption rates of fish in the field based on a mercury (Hg) mass balance model. This method requires the determination of fish age, size, and growth and Hg concentration in fish and their food. The model was validated using data obtained from a previously published laboratory experiment. A field test of the model showed that food consumption rates determined with the Hg mass balance model differed from independent estimates obtained with the137Cs method by only 0.6-16.1%. The model was applied to fish from various lakes in Quebec and Ontario. Food consumption rates estimated with the Hg mass balance model varied significantly both among species and among populations. Furthermore, female fish tended to eat 30-40% more food than males, probably to meet the larger energy requirement associated with egg production. A sensitivity analysis indicated that the Hg mass balance model was mostly responsive to variables that can be easily measured in the field, such as fish size and Hg concentration in fish and their food. By providing a low-effort approach to quantifying food consumption rates of fish in the field, this method may help to refine our understanding of the environmental factors that influence the quantity of food consumed by fish.
Approaches to the assessment and management of multispecies skate and ray fisheries using the Falkland Islands fishery as an example
Authors: Agnew D J , Nolan C P , Beddington J R , Baranowski R
Published: April 2011

Eleven rajid species are taken around the Falkland Islands, with four species, Bathyraja griseocauda, Bathyraja albomaculata, Bathyraja brachyurops, and Raja flavirostris dominating commercial catches and generally occurring together. Catch limits for individual species are not used in management because species are not separated in the catch or reported separately. The catch per unit effort for the mixed rajid assemblage was standardised using generalised linear modelling techniques, and two production models were used to estimate stock size and sustainable yield. Maximum likelihood methods were used to demonstrate that there are two distinct rajid communities, one to the north and one to the south of the Falkland Islands, which have different sustainable yields. Changes in species composition over the 10-year course of the fishery confirm theoretical expectations that the larger, later-maturing B. griseocauda is being replaced in catches by the smaller, earlier-maturing B. albomaculata and B. brachyurops. These changes in composition were evident after only 6 years of directed fishing. The current fishery to the north of the Falkland Islands appears to be stable at an annual catch of about 3000 t, which is between 6.5 and 7.6% of the estimated pre-exploitation biomass.
Bioenergetic costs of heavy metal exposure in yellow perch (Perca flavescens): in situ estimates with a radiotracer (137Cs) technique
Authors: Sherwood Graham D , Rasmussen Joseph B , Rowan David J , Brodeur Julie , Hontela Alice
Published: April 2011

While the flow of energy is understood to determine the growth of organisms and the productivity of ecosystems, little is known about the sublethal effect of pollutants on the energetic efficiency of wild populations. We used field estimates of fish growth coupled to in situ estimates of food consumption rates obtained from the mass balance of a globally dispersed, trophically transferred radiotracer (137Cs) to demonstrate the bioenergetic impairment of yellow perch (Perca flavescens) from lakes polluted by heavy metals (Cd, Cu, and Zn). Annual growth increment relative to the total energy budget (conversion efficiency) was about three times lower in cortisol-impaired yellow perch from metal-polluted lakes relative to yellow perch from reference lakes (4.2% compared with 10.8%), suggesting that fish exposed to pollutants experienced greater total energetic costs. In addition, metal-polluted lakes were dominated by adult yellow perch populations and simplified prey bases, suggesting that effects are occurring at multiple levels of biological organization. Our in situ bioenergetic approach to toxicity assessment provides a measurable and ecologically relevant endpoint for assessing the sublethal effects of pollutants on fish communities.
Are trout populations affected by reach-scale stream slope?
Authors: Isaak Daniel J , Hubert Wayne A
Published: April 2011

Reach-scale stream slope and the structure of associated physical habitats are thought to affect trout populations, yet previous studies confound the effect of stream slope with other factors that influence trout populations. We isolated the effect of stream slope on trout populations by sampling reaches immediately upstream and downstream of 23 marked changes in stream slope on 18 streams across Wyoming and Idaho. No effect of stream slope on areal trout density was observed, but when trout density was expressed volumetrically to control for differences in channel cross sections among reaches in different slope classes, the highest densities of trout occurred in medium-slope reaches, intermediate densities occurred in high-slope reaches, and the lowest densities occurred in low-slope reaches. The relative abundance of large trout was reciprocal to the pattern in volumetric trout density. Trout biomass and species composition were not affected by stream slope. Our results suggest that an assumption made by many fish-habitat models, that populations are affected by the structure of physical habitats, is at times untenable for trout populations in Rocky Mountain streams and is contingent upon the spatial scale of investigation and the population metric(s) used to describe populations.
Factors influencing the growth of Mougeotia in experimentally acidified mesocosms
Authors: Klug Jennifer L , Fischer Janet M
Published: April 2011

Acidification causes profound changes in species composition in aquatic systems. We conducted mesocosm experiments in three northern Wisconsin lakes (Trout Lake, Little Rock - Reference, Little Rock - Treatment) to test how different phytoplankton communities respond to acidification. Major differences exist among these lakes in water chemistry and phytoplankton community composition. In each lake, three pH treatments (control, press (sustained pH 4.7), and pulse (alternating pH 4.7 and ambient pH)) were maintained for 6 weeks. We observed a striking increase in species in the genus Mougeotia in all systems. Mougeotia is a filamentous green alga often found in acidified lakes. The magnitude of the Mougeotia increase differed among lakes and treatments, and we used an autoregressive model to identify potential factors responsible for these differences. Our results suggest that biotic factors such as competition with other algae played a relatively minor role in regulating Mougeotia dynamics. Instead, pH and abiotic factors associated with changes in pH (e.g., dissolved inorganic carbon) were important predictors of Mougeotia dynamics.
A new approach toward evaluation of fish bioenergetics models
Authors: Madenjian Charles P , O'Connor Daniel V , Nortrup David A
Published: April 2011

A new approach was used to evaluate the Wisconsin bioenergetics model for lake trout (Salvelinus namaycush). Lake trout in laboratory tanks were fed alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax), prey typical of lake trout in Lake Michigan. Food consumption and growth by lake trout during the experiment were measured. Polychlorinated biphenyl (PCB) concentrations of the alewife and rainbow smelt, as well as of the lake trout at the beginning and end of the experiment, were determined. From these data, we calculated that lake trout retained 81% of the PCBs contained within their food. In an earlier study, application of the Wisconsin lake trout bioenergetics model to growth and diet data for lake trout in Lake Michigan, in conjunction with PCB data for lake trout and prey fish from Lake Michigan, yielded an estimate of PCB assimilation efficiency from food of 81%. This close agreement in the estimates of efficiency with which lake trout retain PCBs from their food indicated that the bioenergetics model was furnishing accurate predictions of food consumption by lake trout in Lake Michigan.
Cryptic species diversity and evolution in the amphipod genus Hyalella within central glaciated North America: a molecular phylogenetic approach
Authors: Witt Jonathan DS , Hebert Paul DN
Published: April 2011

Many benthic freshwater invertebrates are strong candidates for diversification as a result of their short generation times, the divergent selection pressures that they encounter across habitat gradients, and the insular nature of aquatic environments. We analysed populations of the amphipod crustacean Hyalella azteca s.l. from habitats in Ontario, Wisconsin, New Brunswick, and the Yukon Territory. Combined analysis of allozymes and the mitochondrial cytochrome c oxidase I gene revealed that H. azteca is a complex of at least seven species showing marked genetic, but little morphological divergence. Two or more co-occurring species were detected in at least 15 of the 24 habitats. Evidence suggests that diversification has arisen as a consequence of both isolation in different glacial refugia and habitat specialization. A recent origin for the subgenus Hyalella, following the formation of the Isthmus of Panama, is improbable; the subgenus appears to have originated as early as the mid-Miocene.
Social dominance, growth, and habitat use of age-0 steelhead (Oncorhynchus mykiss) grown in enriched and conventional hatchery rearing environments
Authors: Berejikian Barry A , Tezak E Paul , Flagg Thomas A , LaRae Anita L , Kummerow Eric , Mahnken Conrad VW
Published: April 2011

This study investigated whether culturing age-0 steelhead (Oncorhynchus mykiss) in habitat-enriched rearing tanks, containing a combination of in-water structure, underwater feeders, and overhead cover, affected competitive ability and habitat use compared with juveniles cultured in more conventional vessels. In laboratory tests, steelhead juveniles grown in the enriched tanks socially dominated size-matched competitors grown in conventional tanks. When both treatments were introduced into separate sections of a quasi-natural stream, no differences in growth were found between them. However, when intermixed, fish reared in the enriched tanks grew at a higher rate than conventionally reared competitors, suggesting greater competitive ability of juveniles grown in the enriched tanks. Visual isolation and defensible food resources in combination in the enriched tanks were considered as the primary factors causing the observed competitive asymmetries. Steelhead juveniles from the two rearing environments exhibited very similar use of woody structure in the quasi-natural stream, both in the presence and in the absence of mutual competition. Rearing steelhead in more naturalistic environments could result in hatchery fish that behave and integrate into the postrelease (natural) environment in a manner more similar to wild fish.
Tandemly repeated sequences in mtDNA control region of whitefish,Coregonus lavaretus
Authors: Brzuzan Pawel
Published: April 2011

Length variation of the mitochondrial DNA control region was observed with PCR amplification of a sample of 138 whitefish (Coregonus lavaretus). Nucleotide sequences of representative PCR products showed that the variation was due to the presence of an approximately 100-bp motif tandemly repeated two, three, or five times in the region between the conserved sequence block-3 (CSB-3) and the gene for phenylalanine tRNA. This is the first report on the tandem array composed of long repeat units in mitochondrial DNA of salmonids.Key words: Coregonus lavaretus, D-loop mitochondrial DNA, tandemly repeated sequences.
Identification of RFLP markers for resistance to wheat spindle streak mosaic bymovirus (WSSMV) disease
Authors: Khan Aftab A , Bergstrom G C , Nelson J C , Sorrells M E
Published: April 2011

Wheat spindle streak mosaic bymovirus (WSSMV) causes an economically important disease of winter wheat in Europe and North America. Artificial inoculation with this virus to identify resistant wheat genotypes is difficult. This study was conducted to identify restriction fragment length polymorphism (RFLP) markers associated with resistance to this disease. A population, consisting of 104 F5 recombinant inbred lines from a cross between hexaploid Triticum aestivum cultivars 'Geneva' (resistant) and 'Augusta' (susceptible), was evaluated for WSSMV symptoms under field conditions for four years. Two linked markers on the long arm of chromosome 2D, Xbcd1095 and Xcdo373, were determined to be associated with WSSMV resistance by bulked segregant analysis of the 10 most resistant and 10 most susceptible lines. Marker Xcdo373 accounted for 79% and Xbcd1095 for 73% of the phenotypic variation. Our results suggest that resistance to WSSMV in this population is qualitative in nature and is controlled by few genes. These markers should be useful in the development of wheat cultivars resistant to WSSMV and perhaps also to wheat yellow mosaic bymovirus (WYMV).Key words: wheat, wheat spindle streak mosaic virus (WSSMV), RFLP markers, resistance, bymovirus, wheat yellow mosaic virus, barley yellow mosaic virus.
Nucleolar dominance does not occur in root tip cells of allotetraploid Brassica species
Authors: Hasterok Robert , Maluszynska Jolanta
Published: April 2011

Using in situ hybridization and silver staining methods, the numbers of active and inactive rDNA loci have been established for three allotetraploid species of Brassica (B. napus, B. carinata, and B. juncea) and their diploid ancestors (B. campestris, B. nigra, and B. oleracea). The allotetraploid species have chromosome numbers equal to the sum of the numbers in their diploid relatives, but have fewer rDNA loci. All species investigated have lower numbers of active NORs (AgNORs, nucleolar organizer regions) compared with the numbers of rDNA sites revealed by in situ hybridization. The number of active rDNA loci of the allotetraploid species is equal to the number of AgNORs in their diploid ancestors, indicating the absence of nucleolar dominance in amphidiploid Brassica species, at least in root meristematic cells.Key words: AgNOR, Brassica, FISH, nucleolar dominance, rDNA.
Homoeoallelic geneNcc-tmpofTriticumtimopheeviiconferring compatibility with the cytoplasm ofAegilops squarrosain the tetraploid wheat nuclear background
Authors: Asakura Nobuaki , Nakamura Chiharu , Ohtsuka Ichiro
Published: April 2011

A nuclear gene, Ncc-tmp1A, of Triticum timopheevii is required for the nucleus-cytoplasm (NC) compatibility in tetraploid NC hybrids with the cytoplasm of Aegilops squarrosa. A euploid NC hybrid of T. durum was previously produced by introgressing the gene from chromosome 1A of T. timopheevii. To examine the possible presence of a functional homoeoallele in the G genome of T. timopheevii, segregation of seed viability was studied as a marker phenotype in BC1s involving the two types of NC hybrids, (Ae. squarrosa) - T. timopheevii and (Ae. squarrosa) - T. turgidum. The result of these test crosses suggested that the G genome possesses a functional homoeoallele Ncc-tmp1G. Segregation of two RAPD (random amplified polymorphic DNA) markers that were closely linked to Ncc-tmp1A was further studied among the viable BC1s obtained from a test cross of (Ae. squarrosa) - T. timopheevii × T. turgidum. Some viable BC1segregants without the markers were obtained, suggesting a limited degree of transmission of chromosome 1G carrying Ncc-tmp1G. However, a similar RAPD analysis of BC1s obtained after backcrosses of reciprocal F1s of T. timopheevii / T. turgidum with T. turgidum showed random marker segregation. Thus, it was concluded that Ncc-tmp1A is not required for compatibility with its own cytoplasm. Southern blot analysis of the euploid NC hybrid using RFLP (restriction fragment length polymorphism) markers on the homoeologous group 1 chromosomes showed that Ncc-tmp1A locates in the centromeric region.Key words: nucleus-cytoplasm (NC) compatibility, Ncc genes, Aegilops squarrosa, Triticum timopheevii, durum wheat.
Production of inbred progenies of diploid potatoes using anS-locus inhibitor (Sli) gene, and their characterization
Authors: Birhman R K , Hosaka K
Published: April 2011

To develop inbred lines from self-incompatible, cultivated diploid potatoes, an S-locus inhibitor (Sli) gene derived from a self-compatible variant of a wild potato species, Solanum chacoense, was incorporated into various cultivated diploid potatoes. The progeny was selfed twice by the action of the Sli gene to obtain 74 S2inbred clones belonging to 8 families. More than 40% of them were either non-flowering or pollen sterile. Among the pollen fertile clones, self-compatible clones occurred with a much lower frequency (20.9%) than expected (83.3%). The result demonstrated that self-compatibility was introduced and expressed in the gene pool of cultivated diploid potatoes by an action of the Sli gene, although serious inbreeding depression associated with selfing occurred. The genotypes of S2inbreds were surveyed using 46 S. chacoense - specific RFLP (restriction fragment length polymorphism) markers covering the whole potato genome. More than half of the markers (67.4%) showed distorted segregation. Particularly, all markers on chromosome 12 were overrepresented in the S2inbreds. This confirms our earlier finding that the Sli gene locates on chromosome 12 and the alleles linked with this gene are preferentially transmitted because of its essential requirement for selfing.Key words: RFLP markers, inbreds, diploid potato, distorted segregation.
A repeat complex in the mitochondrial control region of Adélie penguins from Antarctica
Authors: Ritchie Peter A , Lambert David M
Published: April 2011

We have determined the nucleotide sequence of the entire mitochondrial control region (CR) of the Adélie penguin (Pygoscelis adeliae) from Antarctica. Like in most other birds, this CR region is flanked by the gene nad6 and transfer (t)RNA trnE(uuc) at the 5' end and the gene rns and trnF(gaa) at the 3' end. Sequence analysis shows that the Adélie penguin CR contains many elements in common with other CRs including the termination associated sequences (TAS), conserved F, E, D, and C boxes, the conserved sequence block (CSB)-1, as well as the putative light and heavy strand promoters sites (LSP-HSP). We report an extraordinarily long avian control region (1758 bp) which can be attributed to the presence, at the 3' peripheral domain, of five 81-bp repeat sequences, each containing a putative LSP-HSP, followed by 30 tetranucleotide microsatellite repeat sequences consisting of (dC-dA-dA-dA)30. The microsatellite and the 81-bp repeat reside in an area known to be transcribed in other species.Key words: Aves, microsatellite, evolution, D-loop, TAS, WANCY.
AmphidiploidBrassica junceacontains conserved progenitor genomes
Authors: Axelsson T , Bowman C M , Sharpe A G , Lydiate D J , Lagercrantz U
Published: April 2011

To perform a detailed study of genome evolution in the natural Brassica amphidiploid B. juncea, we have constructed two linkage maps based on RFLP (restriction fragment length polymorphism) markers; one generated from a cross between a resynthesized B. juncea (a chromosome doubled interspecific B. rapa × B. nigra hybrid) and a natural B. juncea cultivar, the other from a cross between two B. juncea cultivars. By using a common cultivar in both crosses, the two maps could be unambiguously integrated. All loci exhibited disomic inheritance of parental alleles in the natural × resynthesized cross, showing that B. rapa chromosomes paired exclusively with their A-genome homologues in B. juncea and that B. nigra chromosomes likewise paired with their B-genome homologues. The maps derived from the two crosses were also perfectly collinear. Furthermore, these maps were collinear with maps of the diploid progenitor species (B. nigra and B. rapa) produced using the same set of RFLP probes. These data indicate that the genome of B. juncea has remained essentially unchanged since polyploid formation. Our observations appear to refute the suggestion that the formation of polyploid genomes is accompanied by rapid change in genome structure.Key words: RFLP, comparative mapping, Brassica rapa, Brassica nigra, genome evolution.
Phylogenetic relationships of five morphological groups of hexaploid wheat (Triticum aestivumL. em Thell.) based on RAPD analysis
Authors: Cao Wenguang , Scoles G , Hucl P , Chibbar R N
Published: April 2011

The genetic relationships among the five groups of hexaploid wheat: common, spelta, macha, vavilovii, and semi-wild wheat (SWW) are not clear. Random amplified polymorphic DNA (RAPD) analysis was used to assess phylogenetic relationships among these five morphological groups of hexaploid wheat. RAPD data were analyzed using the NTSYS-PC computer program to generate Jaccard genetic similarity coefficients. A dendrogram based on RAPD analysis grouped 15 accessions into five distinct clusters. These results are in agreement with those based on morphological classification, suggesting that common wheat is most closely related to SWW, followed by spelta, vavilovii, and macha.Key words: RAPD, macha, spelta, vavilovii, semi-wild wheat, phylogenetic relationships.
Comparative study of satellite sequences and phylogeny of five species from the genusPalorus(Insecta, Coleoptera)
Authors: Metrovic Nevenka , Mravinac Brankica , Juan Carlos , Ugarkovic Ðurdica , Plohl Miroslav
Published: April 2011

Major satellite sequences are analysed in the three tenebrionid beetles Palorus cerylonoides, P. genalis, and P. ficicola, and compared with the ones from P. ratzeburgii and P. subdepressus reported elsewhere. All of them are A+T rich, pericentromerically located, and with lengths of about 150 bp, either in the form of monomers or formed by more complex repeating units. A preliminary phylogenetic analysis of Palorus species using the 3' end of the mitochondrial Cytochrome Oxidase I gene shows that the five Palorus species have been diverging for a considerable amount of evolutionary time, with the pair P. ratzeburgii and P. genalis being the most closely related. Only these two taxa showed some similarity between their respective high-copy-number satellite sequences, while other satellites are mutually unrelated and might have originated independently. However, all the satellites have in common tertiary structure induced by intrinsic DNA curvature, a characteristic which is conserved within the genus. Palorus major satellites were previously detected in the genomes of congeneric species as low-copy-number clusters (Metrovic et al., Mol. Biol. Evol. 15: 1062-1068. 1998). Given the divergences between the analysed species, the substitution rate deduced from high- and low-copy-number repeats is unexpectedly low. The presence of sequence-induced DNA curvature in all Palorus satellites and similar satellite DNAs in the species pair P. ratzeburgii and P. genalis suggest (i) that constraints are at the tertiary structure; and (ii) that the satellite DNA evolutionary turnover can be dependant on the history of the taxa under study, resulting in retention of similar satellites in related taxa.Key words: satellite DNA, evolution, mitochondrial cytochrome oxidase I, DNA curvature.