bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Habitat and Microhabitat Partitioning within an Assemblage of Stream Fishes in Response to Predation by Sacramento Squawfish (Ptychocheilus grandis)
Authors: Brown Larry R. , Moyle Peter B.
Published: May 2008

The Sacramento squawfish (Ptychocheilus grandis), a piscivorous cyprinid, was recently (ca. 1979) introduced into the Eel River, California, USA. We compared habitat and microhabitat use of resident fishes between areas where squawfish were present and absent at one location and between years before and after invasion by squawfish at a second location. The resident species showed a variety of responses to the presence of the predator. Juvenile rainbow trout (Oncorhynchus mykiss) and juvenile Sacramento suckers (Catostomus occidentalis) increased their use of fast-flowing riffles at both locations, in the presence of squawfish. Suckers also used significantly shallower depths within habitat types. Adult California roach (Lavinia symmetricus) decreased their use of run habitat and increased use of pools and riffles at the first site, but not at the second. When squawfish were present, juvenile roach and threespine stickleback (Casterosteus aculeatus) were found in shallower water closer to the stream edge in all habitats. Spatial overlaps tended to be lower in the presence of squawfish. The introduction of squawfish has resulted in changes in the habitat and microhabitat use of the resident fish assemblage but no loss of species.
A Sigmoid Model to Predict Gastric Evacuation Rates of Smallmouth Bass (Micropterus dolomieui) Fed Juvenile Salmon
Authors: Rogers Jean Beyer , Burley Craig C.
Published: May 2008

Laboratory experiments were conducted to examine the effects of water temperature, predator size, prey size, and prey number on gastric evacuation of smallmouth bass (Micropterus dolomieui) fed juvenile salmon. The smallmouth bass were allowed to feed voluntarily after 24–48 h of starvation and stomachs were pumped at intervals of 1–4 h until 90% of the stomach contents were evacuated (E90). Evacuation approximated an S-shaped curve over time, and a sigmoid model was developed to predict evacuation at varying water temperatures, total meal weights, predator sizes, and prey number. The rate of evacuation increased with increasing water temperature, meal weight, or predator size. The E90 increased with larger meal weights but decreased with increasing temperature or predator size. E90 ranged between 4 and 95 h, depending upon conditions. E90 was slower than those estimated previously for another predator of salmon, the stomachless northern squawfish (Ptychocheilus oregonensis).
Bioindicators of Stress in Winter Flounder, Pleuronectes americanus, Captured Adjacent to a Pulp and Paper Mill in St. George's Bay, Newfoundland
Authors: Barker D. E. , Khan R. A. , Hooper R.
Published: May 2008

Winter flounder, Pleuronectes americanus, inhabiting a marine inlet (Port Harmon) adjacent to a pulp and paper mill, and from a reference site (St. George's) 12 km away, were examined for signs of stress. Fish from Port Harmon showed significantly lower condition (k) factors, hepatosomatic indices, blood haemoglobin, and lymphocyte levels, than those from the reference site. Delayed spawning or spermiation were evident in female and male flounder, respectively, from Port Harmon compared with those from St. George's. Prevalence and intensity of larval anisakid nematodes, metacercariae of the digenetic trematode, Cryptocotyle lingua, and cysts of the microsporan, Glugea stephani, were significantly higher at Port Harmon than at St. George's, whereas prevalence and intensity of an intestinal acanthocephalan were significantly lower at Port Harmon. The percentage of flounder with external lesions (fin necrosis, ulcers) was significantly higher at Port Harmon than at St. George's. Anaemia, low lymphocyte levels, low somatic indices, high incidence of external lesions, and abnormal parasitic infestations are all suggestive of immunosuppression. Because basic water chemistry at the two sites was similar, the evidence of chronic stress observed in winter flounder from Port Harmon can most likely be attributed to pollutants from the effluent that have accumulated in the sediment.
Detecting Small-scale Spatial Patterns in Lotic Predator–Prey Relationships: Statistical Methods and a Case Study
Authors: Muotka Timo , Penttinen Antti
Published: May 2008

We mapped the exact locations of two predaceous stream insects, a caddis larva (Rhyacophila obliterata) and a stonefly nymph (Isoperla grammatica), in 1-m2sampling windows in relation to their major prey, larval black flies (mostly Simulium sublacustre), which were quantified within the same areas by extensive systematic sampling. In mid-June, when black flies were abundant and highly clustered, R. obliterata was also aggregated on a scale of 5–10 cm. After the emergence of black flies in the beginning of July, the point pattern of the rhyacophilid was random. Isoperla grammatica was abundant only on the earlier sampling occasion, at which time it was randomly distributed. We also analysed spatial association between the two predators and found a weak indication of small-scale inhibition between them. In the range of current speeds of 40–60 cm/s, microhabitat overlap between the caddisfly and black fly was intensive, leading to high consumption of this semi-sessile prey. The second-order methods used proved powerful in detecting small-scale spatial patterns and could be more widely used by ecologists in place of classical single-statistic indices whenever detailed mapping of individuals is feasible.
Multiple Dating of a Freeze Core from Lake 227, an Experimentally Fertilized Lake with Varved Sediments
Authors: Wolfe Brent , Kling Hedy J. , Brunskill Gregg J. , Wilkinson Paul
Published: May 2008

A freeze core taken from Experimental Lakes Area Lake 227 in 1988 contained 321 rhythmically paired, dark and light laminations in the upper 60.7 cm. Tape peels revealed cyclic, seasonal abundance peaks in organic and inorganic remains, which suggested that the couplets are varves. However, comparison between varve chronology and 22 yr of experimental changes in phosphorus (P) and nitrogen (N) loading and their influence on the planktonic community confirmed that the most recent varve-year estimates were 5 or 6 yr too old; this was caused by irregular sedimentation and multiple algal blooms resulting from experimental fertilization since 1969, and indistinct laminations that hampered precise couplet identification and separation. Dated horizons determined from biostratigraphic markers were used to generate compatible profiles between 1-cm slices of Lake 227 137Cs flux and reference fallout records. Nutrient concentration profiles were less helpful, as increases in carbon, N, and, P were gradual and no distinct horizon was identified as a clear marker of eutrophication. Long-term assessment of the varve chronology using 210Pb was hindered by experimental additions of 226Ra to the lake in 1970, although similar sedimentation rates from varve years 1860–1934 suggested that the varve and the deep part of the 210Pb chronologies were comparable.
Cladocera Community Response to Experimental Eutrophication in Lake 227 as Recorded in Laminated Sediments
Authors: Hann Brenda J. , Leavitt Peter R. , Chang Philip S. S.
Published: May 2008

The response of pelagic zooplankton to experimental fertilization was compared with the fossil record of Cladocera obtained from the annually laminated sediments of Lake 227, Experimental Lakes Area, northwestern Ontario. Constrained cluster analysis of both total fossil Cladocera and littoral chydorid communities clearly distinguished between pre- and post-eutrophication communities and further differentiated between years of high and low nitrogen:phosphorus fertilization ratios. However, there were few chydorid species extirpations resulting from the manipulation. Total chydorid accumulation rates and indices of species diversity, richness, and equitability were relatively constant over the last century and were not affected by fertilization. Among pelagic Cladocera, Bosmina longirostris abundance declined > 60% after initial fertilization. Although harsh chemical conditions (pH > 10) may have contributed to reduced abundance of pelagic Cladocera, Bosmina populations were also naturally variable prior to manipulation. Changes in Bosmina morphology (mucrone, antennule, and carapace length) and cladoceran size ratios (Daphnia/[Daphnia + Bosmina]) suggested that zooplanktivory by fish and invertebrates exercised important control of herbivore populations. Fossil Bosmina concentration (remains∙[g dry wt]−1or remains∙[g organic matter]−1) were significantly correlated (r = 0.66, P < 0.01, 1970–1989) to standing crop in the water column (animals∙m−2). Fossil accumulation rate (remains∙cm−2∙yr−1) was not significantly correlated to Bosmina abundance, perhaps because of errors in determining bulk sediment accumulation rates.
Determination of Fish Age Using 210Pb: 226Ra Disequilibrium Methods
Authors: West I. F. , Gauldie R. W.
Published: May 2008

Previous workers have used disequilibrium in the 210Pb: 226Ra ratio in fish otoliths to estimate the age of four teleost species: Hoplostethus atlanticus, Macruronus novaezelandiae, Sebastes diploproa, and Sebastes mentella. We argue that uncontrollable errors due to degassing of intermediate 222Rn from otoliths, unknown sources and sinks of 210Pb and 226Ra, possible changes in the ratio with which these isotopes are accreted to the otolith over the life of the fish, contamination by 210Po, difficulties in obtaining otolith cores, and the dependence of the estimated radiometric ages on the mass growth-in-time model usually adopted for otoliths can invalidate the application of disequilibrium techniques to fish age estimation.
Genetic Aanalysis of Size in an Anadromous Population of Pink Salmon
Authors: Smoker William W. , Gharrett Anthony J. , Stekoll Michael S. , Joyce John E.
Published: May 2008

Variation of size, particularly among males, has a significant genetic basis in pink salmon (Oncorhynchus gorbuscha) in Auke Creek, southeast Alaska. Heritability (h2), based on variance components of 118 full sib − 59 paternal half sib families of mature fish tagged as fry with coded micro wires, are higher in males (h2 length: 0.8 ± 0.3 (mean ± SE); h2 weight: 0.6 ± 0.2, based on sire effect) than in females (h2 length: 0.3 ± 0.2; h2 weight: 0.4 ± 0.2). Realized heritability probably would be smaller because of environment variability between brood years in factors affecting size and growth. Estimates based on regression of offspring means on fathers' values are smaller (h2 length: 0.4 ± 0.1 in males; 0.2 ± 0.1 in females; h2 weight: 0.0 in males and 0.1 ± 0.1 in females). Estimates of genetic, environmental, and phenotypic correlations of length and weight are all >0.7 (SEs <0.1). Estimates of genetic correlation between length and day of migration from the sea are near 0.4 ± 0.2; estimates of environmental and phenotypic correlations between these traits are smaller (<0.2, SEs <0.1).
Survival to Fry and Seawater Tolerance of Diploid and Triploid Hybrids between Chinook (Oncorhynchus tshawytscha), Chum (O. keta), and Pink Salmon (O. gorbuscha)
Authors: Joyce John E. , Heintz Ron , Smoker William W. , Gharrett A. J.
Published: May 2008

We investigated the viability and seawater tolerance of all possible combinations of triploid and diploid hybrids between chinook (Oncorhynchus tshawytscha), chum (O. keta), and pink salmon (O. gorbuscha) in two brood years. Triploidy (induced by heat shock shortly after fertilization) was determined by flow cytometry of blood taken from a sample of the fish. A factorial mating design was used to estimate the effects of cross, heat shock (ploidy), and their interaction. With the exception of the chinook (♂) × chum (♀) cross, all combinations produced offspring that survived to yolk absorption. Survival of heat-shocked groups was lower than that of diploid controls at the eyed stage and at hatching, but not different from diploids between hatching and yolk absorption. Induced triploidy did not increase the viability of interspecies hybrids. The level of triploid induction averaged across all heat-shocked crosses was 88% in one year and 95% in the other. Seawater tolerance (measured by 24-h seawater challenge survival) was higher in chinook hybrids with pink and chum salmon than in chinook controls. Seawater tolerance did not differ between diploid controls and heat-shocked triploid groups. Combinations that had seawater tolerance shortly after yolk absorption include chinook × pink, pink × chinook, and chum × chinook.
A Preliminary Ploidy Analysis of Diploid and Triploid Salmonids
Authors: Teplitz R. L. , Joyce J. E. , Doroshov S. I. , Min B. H.
Published: May 2008

The findings indicate that mosaicism does occur in triploids and especially in triploid hybrids. Immature diploid and triploid salmon were obtained from the University of Alaska – National Marine Fisheries Service. These were fixed in 10% buffered formalin and blocks taken from various tissues including kidney, liver, spleen, and gonads. The paraffin blocks were sectioned at 4 μm and stained with hematoxylin and eosin for histologic evaluation and to quantitate nuclear DNA. The slides for DNA evaluation were stained using the Cell Analysis Systems, Inc. (CAS, Elmhurst, IL) kit following Feulgen hydrolysis. The Cell Analysis Systems, Inc. (Model 200) computer-assisted image analyzer was used for DNA quantitation. An attempt was made to evaluate the frequency of mosaicism, ploidy variation in somatic and gonadal tissues of triploids and hybrids as compared with normal diploids. Hepatic ploidy variation, normal in adult animals, was not present in these specimens. However, in gonads there was evidence of increased mosaicism among the triploids. Because of mosaicism in gonadal tissue, sterility of triploids cannot be presumed with certainty at this stage. Further studies are planned to examine this and other questions raised by these results.
Biochemical Genetic Survey of Sockeye Salmon (Oncorhynchus nerka) in Canada
Authors: Wood Chris C. , Riddell Brian E. , Rutherford Dennis T. , Withler Ruth E.
Published: May 2008

Allozyme variation was examined in sockeye salmon (Oncorhynchus nerka) from 83 distinct spawning sites representing all major sockeye-producing river systems in Canada. Of 33 nonselected loci examined, only 14 were highly polymorphic (q > 0.05) and 10 were less polymorphic (0 < q ≤ 0.05). No two populations were fixed for different alleles at any locus, but allele frequencies ranged from 0.01 to 0.86 at PGM-1* and from 0.07 to 0.89 at ALAT*, the two most variable loci. Mean heterozygosity ranged from 2.3 to 5.6% (mean 4.1%) across all sites. Hierarchical analysis was used to partition relative gene diversity among river systems (6.3%), major drainages within a river system (2.9%), nursery lakes within drainages (7.0%), spawning sites within lakes (1.0%), and individuals within spawning sites (82.8%). Extensive differentiation among nursery lakes affords excellent opportunities for genetic stock identification within river systems, but the relatively weak regional structuring limits opportunities for coast-wide stock identification. Genetic variation at highly structured loci corroborates the view that modern populations in Canada originated from sockeye that survived the late Wisconsin Glaciation in the Bering and Columbia refuges, and also suggests the existence of coastal refuges in British Columbia.
Genetic Variation in Sockeye Salmon (Oncorhynchus nerka) Populations of Asia and North America
Authors: Varnavskaya Nataly V. , Wood Chris C. , Everett Rebecca J.
Published: May 2008

We investigated population structure in sockeye salmon, Oncorhynchus nerka, in relation to ecological characteristics and geographical distribution using allozyme allelic frequencies compiled from new and previously published analyses for 71 populations (300 collections) throughout the species' range. Up to 87 protein-coding loci were screened in some samples, but of these, 55% were monomorphic, and another 31% were only slightly polymorphic with variant allele frequencies <0.01. Only 8 loci were moderately or highly polymorphic with variant allele frequencies exceeding 0.10 in at least some collections. The highest variation ever reported in salmon was discovered at LDH-B2* where the *100 allele was fixed in some populations but rare in others. Genetic differentiation was typically greater among populations within regions than among regions. However, stock composition analysis based on patterns of variation at the nine most useful loci appears to be feasible for most major stocks examined in this study. The low level of polymorphism in sockeye despite high variability at a few polymorphic loci is attributed to precise homing to natal rivers and interactions among several colonizing races that survived the Pleistocene ice age in isolated refugia with different habitat characteristics.
Genetic Differentiation of Subpopulations of Sockeye Salmon (Oncorhynchus nerka) Within Lakes of Alaska, British Columbia, and Kamchatka, Russia
Authors: Varnavskaya Nataly V. , Wood Chris C. , Everett Rebecca J. , Wilmot Richard L. , Varnavsky Vladimir S. , Midanaya Victoria V. , Quinn T. P.
Published: May 2008

Genetic differentiation among subpopulations of sockeye salmon (Oncorhynchus nerka) was investigated within nine intensively sampled lake systems located throughout the species' range using allozyme allelic frequency data collected by researchers in Canada, Russia, and the United States. Allelic frequencies at up to nine highly polymorphic loci were used to examine genetic diversity among 163 samples collected from 68 distinct spawning sites and to identify subpopulation structure within lakes. Significant heterogeneity was detected among sites within all lakes. The greatest differentiation was evident among subpopulations exhibiting different run timing (earlier vs. later) or utilizing different spawning habitat (tributary vs. littoral). These findings indicate that sockeye home precisely to natal streams, not just to lake systems, and underscore the importance of conserving individual spawning sites within sockeye populations.
Mitochondrial DNA Diversity and Population Structure in Marine Fish Species from the Gulf of Mexico
Authors: Gold John R. , Richardson Linda R. , Furman Carol , Sun Feng
Published: May 2008

Variation in mitochondrial DNA (mtDNA) was examined among 693 red drum (Sciaenops ocellatus), 300 black drum (Pogonias cromis), and 421 red snapper (Lutjanus campechanus) sampled from several localities in the Gulf of Mexico. The number of mtDNA genotypes (haplotypes) observed were: 99 in red drum, 37 in black drum, and 68 in red snapper. Variation in mtDNA haplotype frequencies among localities in all three species was not significant, although two mtDNA haplotypes in black drum appeared to be clinally distributed. Maximum-parsimony analysis and phenetic clustering of mtDNA haplotypes and of samples in each species revealed little evidence of phylogeographic structuring. These data indicate that gene flow among localities in each species is sufficient to preclude genetic divergence. Spatial autocorrelation analysis of mtDNA haplotype frequencies revealed an isolation-by-distance effect in red drum and black drum, and indicated that migration between neighboring estuaries or bays in black drum may be less frequent than in red drum. Spatial autocorrelations in red snapper were negative in all distance classes, suggesting little migration even between adjacent localities. Differences in intrapopulational mtDNA diversities were found in all three species, suggesting that geographic differences in effective female population size may occur within each species.
Comparison of Three Anadromous Rainbow Trout (Oncorhynchus mykiss) Populations Using DNA Fingerprinting and Mixed DNA Samples
Authors: Spruell Paul , Cummings Shawn A. , Kim Yousok , Thorgaard Gary H.
Published: May 2008

DNA fingerprinting of 15 individuals from three populations of steelhead trout (Oncorhynchus mykiss) was compared with DNA fingerprinting of mixtures of 15 individuals from the same populations. Three oligonucleotide fingerprinting probes were used to detect genetic variation in individuals and mixtures. Scanning image analysis coupled with customized software was used to assign band identity. The degree of band sharing of individuals within and between populations was then determined. Although band-sharing estimates were similar within and between populations, bands found predominately in one population were identified. DNA fingerprinting of mixtures detected bands found only in the majority of the individuals in the mixture, allowing differences between populations to be more readily identified.
Distribution of Satellite DNA Sequences Isolated from Arctic Char, Salvelinus alpinus, in the Genus Salvelinus
Authors: Hartley S. E. , Davidson W. S.
Published: May 2008

The distribution of satellite DNA sequences in the genus Salvelinus has been investigated by hybridization of four satellite DNA families isolated from Arctic char, Salvelinus alpinus, to the genomic DNA of S. alpinus, S. fontinalis, S. malma, S. namaycush, S. confluentus, and S. leucomaenis. The distribution of homologous AluI, DraI, and EcoRI satellite sequences suggests a close relationship between S. alpinus, S. malma, and S. confluentus with S. leucomaenis split from all the other species. S. namaycush has a closer relationship to the S. alpinus–malma–confluentus group than does S. fontinalis. The MboI satellite, which has potential as a marker for population differentiation in S. alpinus, has a species distribution suggestive of an ancient salmonid satellite that may have been lost from some species during transposition events.
Differences in Genetic Diversity for Mitochondrial DNA Between Hatchery and Wild Populations of Oncorhynchus
Authors: Nielsen Jennifer L. , Gan Christina , Thomas W. Kelley
Published: May 2008

Amplification by the polymerase chain reaction and sequencing of a highly variable segment (199 base pairs) of mitochondrial DNA (mtDNA) in 491 fish from 22 streams and 9 hatcheries revealed 9 mtDNA types in steelhead trout (Oncorhynchus mykiss), 5 types in coho salmon (O. kisutch), and 6 types in chinook salmon (O. tshawytscha). Likelihood chi-square analysis of frequencies of mtDNA types in eight paired comparisons of hatchery and geographically proximate wild populations of Oncorhynchus showed significant differences in mtDNA genotypes. More mtDNA types were found, on average, in contemporary hatchery populations for each species than in geographically proximate wild stocks. Factors potentially leading to genetic differences in hatchery and wild stocks sampled in California were historic introductions of geographically divergent populations into hatchery brood stocks and lack of introgression of geographically divergent genotypes from the hatchery into wild populations.
Genetic Risk Associated with Supplementation of Pacific Salmonids: Captive Broodstock Programs
Authors: Waples Robin S. , Do Chi
Published: May 2008

We simulated some of the genetic consequences of temporarily using captive broodstocks to supplement Pacific salmon (Oncorhynchus spp.) populations. Results were summarized in terms of the parameter ΔIBD, which represents the change in level of inbreeding in the postsupplementation population compared with the control. We found that: (1) the most important factor affecting ΔIBD was whether the population remained large after supplementation ceased; (2) the absolute number of wild adults taken for broodstock had a stronger influence on ΔIBD than did the proportion of the population sampled; (3) if a captive broodstock program is successful, virtually all of the genes in the postsupplementation population will be derived from fish taken into the hatchery for broodstock; (4) in programs that last longer than one generation, marking hatchery fish is essential to avoid additional increases in inbreeding, and marking rates < 100% may be ineffective; and (5) broodstock practices such as sib-avoidance mating and equalizing progeny number affected inbreeding levels during the captive phase but had little permanent effect on ΔIBD. A number of factors not considered in this study (e.g., domestication selection and the fitness consequences of given levels of inbreeding) should also be evaluated in deciding whether or how to implement captive broodstock programs.
Effect of habitat selection and behavior on vulnerability to predation of introduced fish
Authors: Wahl David H.
Published: May 2008

Losses from resident predators can be an important source of mortality for introduced fish, but may vary among species. I compared vulnerability between muskellunge (Esox masquinongy) and walleye (Stizostedion vitreum) to predation by largemouth bass (Micropterus salmoides). In pool experiments (N = 51) with simulated vegetation, muskellunge were more susceptible to predation than walleye. Habitat selection explained some of these differences as walleye spent more time in the simulated vegetation and associated with the substrate than muskellunge. Expectations from pool experiments were confirmed in reservoirs stocked with two size groups of walleye (N = 8 introductions) and esocids (N = 20). Walleye were less susceptible to largemouth bass predation for both small (mean 14% of stocked fish) and large (mean 0%) size groups than were small (mean 36%) and large (mean 21%) esocids of three taxa. For muskellunge only, walleye were less vulnerable to predation for large size groups, but not for small ones. Predation from largemouth bass should be a more important source of poststocking mortality for esocids than for walleye in lakes and reservoirs. Largemouth bass population demographics, specific to each system and year, should be considered more carefully in determining where esocids should be introduced than for percids.
Regeneration of nitrogen and phosphorus by bluegill and gizzard shad: effect of feeding history
Authors: Mather Martha E. , Vanni Michael J. , Wissing Thomas E. , Davis Scott A. , Schaus Maynard H.
Published: May 2008

We combined laboratory and field studies to experimentally assess how the effects of feeding regime and time since feeding influence nitrogen (N), phosphorus (P), and the N:P ratio excreted by two common freshwater fish, bluegill (Lepomis macrochirus) and gizzard shad (Dorosoma cepedianum). In addition, for adult gizzard shad, we modelled excretion rates as a function of the nutrient content of ingested sediment detritus. For both bluegill and gizzard shad, feeding significantly increased nutrient excretion rates and altered excreted N:P ratios. For both species, excretion rates were highest immediately after feeding and declined thereafter. Because the phosphorus excretion rate decreased more rapidly after feeding than did the nitrogen excretion rate, the excreted N:P ratio increased with time since feeding. Young-of-year gizzard shad excreted more nitrogen than adults, resulting in a higher excreted N:P ratio for these small fish. For P, predictions from our model agreed well with our experiments with gizzard shad; for N, the agreement was not as strong yet was still reasonable. In summary, N:P ratios excreted by these fish differed across species, size, and time since feeding. Variation in these factors may explain discrepancies among studies that examine both trophic interactions and nutrient budgets.
Spatial implications of a temperature-based growth model for Atlantic cod (Gadus morhua) off the eastern coast of Canada
Authors: Campana S. E. , Mohn R. K. , Smith S. J. , Chouinard G. A.
Published: May 2008

Lengths at age of Atlantic cod (Gadus morhua) off the eastern coast of Canada vary up to three-fold among geographic regions, with Georges Bank and the southern Gulf of St. Lawrence being the regions of fastest and slowest growth, respectively. Colour-coded contour maps of length at ages 2–8 (n = 59 518) based on research vessel surveys between 1971 and 1992 clearly showed the spatial variations in size at age. Corresponding maps of July–September bottom water temperature appeared to reflect relative growth rate, whereas those for depth did not. A polynomial expansion of a temperature-based von Bertalanffy growth model appeared to fit the data well, with no residual patterns across most ages, lengths, temperatures, or years. Model predictions were also consistent with reported lengths at age for cod in other regions and countries. Declines in bottom water temperature over the past 5–10 years appear to be at least partly responsible for observed declines in size at age of the cod stock on the eastern Scotian Shelf.
Mercury remobilization from flooded soils in a hydroelectric reservoir of northern Quebec, La Grande-2: results of a soil resuspension experiment
Authors: Mucci Alfonso , Montgomery Shelagh , Lucotte Marc , Plourde Yanick , Pichet Pierre , Tra Huu Van
Published: May 2008

An experiment was conducted during summer, 1992, in a protected bay of the La Grande-2 reservoir (northern Quebec) to evaluate the role of erosional processes in the transfer of mercury from a flooded soil to the water column. Up to 57% of the organic carbon, approximately 4% of the inorganic mercury, and nearly 71% of the methylmercury from the humic horizon of a flooded podzol were transferred to the water column and transported outside the experimental perimeter in the form of particulate matter after one resuspension event. In contrast, total dissolved mercury concentrations in the water column decreased during the resuspension event as a result of scavenging by suspended particles. We postulate that most of the methylmercury produced in the submerged soils is associated with fine-grained organic particles that remain in suspension for some time before flocculating and accumulating at the sediment–water interface. We suspect that these particles are a potential food source and can be readily ingested by pelagic and benthic detritus-feeders as well as trapped by periphyton. Resuspension and erosion processes along the exposed shores of a recently impounded reservoir may thus accelerate the transfer of mercury, primarily as methylmercury, from flooded soils to predatory fish.
Hypoxia and exercise: different models for different questions
Authors: Sheel A. William
Published: May 2008

The focus of this symposium is on the physiological demands of exercise in hypoxia. The study of hypoxia by exercise physiologists has a strong tradition and many questions first asked over 100 years ago continue to be relevant, yet still unsatisfactorily answered. The primary theme of the following papers is how different models of hypoxia allow different questions to be asked. The first paper addresses questions of exercise ventilatory control using intermittent, rather than continuous, hypoxia. The second manuscript attempts to understand the hypoxic exercise responses using a population-level approach (i.e., generations spanning millennia). Lastly, the third paper uses acute hypoxia to better understand cardio-pulmonary interactions during exercise. Collectively, these reviews are intended to stimulate additional study and debate.
Is pulmonary gas exchange during exercise in hypoxia impaired with the increase of cardiac output?
Authors: Calbet José A.L. , Robach Paul , Lundby Carsten , Boushel Robert
Published: May 2008

During exercise in humans, the alveolar–arterial O2 tension difference ((A–a)DO2) increases with exercise intensity and is an important factor determining the absolute level of oxygen binding to hemoglobin and therefore the level of systemic oxygen transport. During exercise in hypoxia, the (A–a)DO2 is accentuated. Using the multiple inert gas elimination technique it has been shown that during exercise in acute hypoxia the contribution of ventilation–perfusion inequality to (A–a)DO2 is rather small and in the absence of pulmonary edema intrapulmonary shunts can be ruled out. This implies that the main mechanism limiting pulmonary gas exchange is diffusion limitation. It is presumed that an elevation of cardiac output during exercise in acute hypoxia should increase the (A–a)DO2. However, no studies have examined how variations in cardiac output independently affect pulmonary diffusion with increases in exercise intensity. We have consistently observed that during steady-state, submaximal (100–120 W) exercise on the cycle ergometer in hypoxia the lung can accommodate an increase in cardiac output of ~2 L·min–1 without any significant effect on pulmonary gas exchange. This result contrasts with the predicted effect of cardiac output on (A–a)DO2 using the model of Piiper and Scheid, and thus indicates that an elevation of cardiac output is not necessarily accompanied by a reduction of mean transit time and (or) diffusion limitation during submaximal exercise in acute hypoxia. It remains to be determined what is the influence of changes in cardiac output per se on pulmonary gas exchange during high-intensity exercise.
Association between HMOX-1 genotype and cardiac function during exercise
Authors: He Zihong , Hu Yang , Feng Lianshi , Lu Yingli , Bao Dapeng , Xi Yi , Wen Li , Lucia Alejandro
Published: May 2008

The human gene for heme oxygenase-1 (HMOX-1) plays an important role in the regulation of cardiovascular function and its adaptive response to a variety of stressors. The purpose of this study was to examine the possible association between HMOX-1 genotypes (for –1135A/G, –413A/T, and rs5755720 polymorphisms) and cardiac structural and functional parameters at rest and during submaximal cycle-ergometer exercise (50, 100, and 150 W) in a pre-training state (baseline) and after endurance training (18 weeks, 95%~105% individual ventilatory threshold). The study population consisted of 102 Chinese young males (non-athletes) of Han origin. For the –1135A/G polymorphism, we found a significant genotype effect (p < 0.05) in cardiac output (Q) corrected for body surface area (BSA; Q·BSA–1) at 50 W and stroke volume (SV) corrected for BSA (SV·BSA–1) at 100 W. For the –413A/T polymorphism, we found a significant genotype effect (p < 0.05) in ejection fraction (EF) at 100 W. For the rs5755720 polymorphism, we found a significant genotype effect (p < 0.01 or p < 0.05) in most variables (Q·BSA–1 across all workloads, SV·BSA–1 at 100 W, and EF at 50 and 100 W). Briefly, rs5755720 individuals with a CC genotype presented overall higher values in the different cardiac variables than their CT and (or) TT counterparts. In summary, although more research is needed with diseased populations and other ethnic groups, we found preliminary evidence of an association between cardiac response to submaximal exercise and HMOX-1 genotype. The present preliminary findings could provide insights to future studies searching for cardioprotective genotypes.
The effects of ibuprofen on muscle hypertrophy, strength, and soreness during resistance training
Authors: Krentz Joel R. , Quest Braden , Farthing Jonathan P. , Quest Dale W. , Chilibeck Philip D.
Published: May 2008

High doses of ibuprofen have been shown to inhibit muscle protein synthesis after a bout of resistance exercise. We determined the effect of a moderate dose of ibuprofen (400 mg·d–1) consumed on a daily basis after resistance training on muscle hypertrophy and strength. Twelve males and 6 females (~24 years of age) trained their right and left biceps on alternate days (6 sets of 4–10 repetitions), 5 d·week–1, for 6 weeks. In a counter-balanced, double-blind design, they were randomized to receive 400 mg·d–1 ibuprofen immediately after training their left or right arm, and a placebo after training the opposite arm the following day. Before- and after-training muscle thickness of both biceps was measured using ultrasound and 1 repetition maximum (1 RM) arm curl strength was determined on both arms. Subjects rated their muscle soreness daily. There were time main effects for muscle thickness and strength (p < 0.01). Ibuprofen consumption had no effect on muscle hypertrophy (muscle thickness of biceps for arm receiving ibuprofen: pre 3.63 ± 0.14, post 3.92 ± 0.15 cm; and placebo: pre 3.62 ± 0.15, post 3.90 ± 0.15 cm) and strength (1 RM of arm receiving ibuprofen: pre 18.6 ± 2.8, post 23.4 ± 3.5 kg; and placebo: pre 18.8 ± 2.8, post 22.8 ± 3.4 kg). Muscle soreness was elevated during the first week of training only, but was not different between the ibuprofen and placebo arm. We conclude that a moderate dose of ibuprofen ingested after repeated resistance training sessions does not impair muscle hypertrophy or strength and does not affect ratings of muscle soreness.
Central adiposity and associated lifestyle factors in Cree children
Authors: Downs Shauna M. , Marshall Dru , Ng Carmina , Willows Noreen D.
Published: May 2008

Aboriginal children are prone to central adiposity (CA), a component of the metabolic syndrome. The objective of this study was to determine if lifestyle factors were associated with CA in Canadian Cree children. Children aged 9–12 years were classified as having CA if their waist circumference met or exceeded the 85th percentile of the NHANES III reference. Weight status was determined using the CDC growth reference, dietary intake using three 24 h dietary recalls, physical activity using pedometers, and fitness by completion of the 20 m shuttle run test. Of the 178 children (79% participation rate), 32.6% were normal weight, 23.6% were overweight, and 43.8% were obese. Half (52.2%) of the children had CA (97.4% of obese children, 35.7% of overweight children, and 2.2% of normal weight children). Waist circumference was negatively correlated with pedometer step counts (r = –0.187, p = 0.012) and shuttle run time (r = –0.508, p < 0.001). In children with CA, waist circumference was positively correlated with sweetened beverage intake (r = 0.250, p = 0.016). The odds ratio (adjusted for age and sex) for CA for children consuming 3 or more fruits and vegetables per day was 0.43 (95% CI 0.18 – 0.98), for meeting step recommendations for a healthy body weight was 0.45 (95% CI 0.24 – 0.84), and for relative fitness was 0.12 (95% CI 0.04 – 0.33). CA was prevalent in children who were overweight and obese. Preventive strategies might include promoting a healthy diet, physical activity, and fitness.
A review of the early life history of zebra mussels (Dreissena polymorpha): comparisons with marine bivalves
Authors: Ackerman Josef Daniel , Sim Blair , Nichols S. Jerrine , Claudi Renata
Published: May 2008

The ecological and economic impacts of the introduced zebra mussel (Dreissena polymorpha (Pallas)) have been due in part to a life history that is conserved with marine bivalves but unique among the indigenous freshwater fauna. There are a number of life history events in D. polymorpha that follow external fertilization and embryology. The first is a brief trochophore stage. The development of a velum and secretion of a larval shell lead to a D-shaped veliger, which is the first recognizable planktonic larva. Later a second larval shell is secreted and this veliconcha is the last obligate free-swimming veliger. Conversely, the last larval stage, the pediveliger, can either swim using its velum or crawl using its foot. Pediveligers select substrates on which they "settle" by secreting byssal threads and undergo metamorphosis to become plantigrade mussels. The secretion of the adult shell and change in growth axis lead to the convergent heteromyarian shape. Zebra mussels produce byssal threads as adults, but these attachments may be broken, enabling the mussels to translocate to new areas. The recognition of these life history features will lead to a better understanding of zebra mussel biology. In summary, life history stages of zebra mussels are similar to those of marine bivalves and should be identified morphologically rather than on the basis of size.
Development of Myxobolus neurophilus (Guilford, 1963) (Myxosporea) in the brain of yellow perch (Perca flavescens) in Vinegar Lake, Nova Scotia
Authors: Dzulinksy K. , Cone D. K. , Faulkner G. T. , Cusack R.
Published: May 2008

The development of Myxobolus neurophilus (Guilford, 1963) in the optic tectum of yellow perch, Perca flavescens, inhabiting Vinegar Lake, Nova Scotia, is described. Young perch acquired infections during July when 2–3 months old. By early August, small plasmodia occurred in the cortex and consisted of an outer thin ectoplasm and inner endoplasm containing sporoblasts. By the end of August, plasmodia were found in the brain cortex and periventricular layers. They measured up to 310 μm in diameter and contained sporoblasts and fully developed spores. Some plasmodia had ruptured and released spores within the periventricular layer. It is estimated that in young-of-the-year fish the development of M. neurophilus requires 40–50 days. Prevalence was 100% in fish older than 1 year, with infections consisting of spore masses located in the periventricular layer. Spores were either free in tissue spaces or within unidentified mononuclear phagocytes. Spores were absent from other organs, and spores are probably released when the host dies or when it is eaten by a predator. Macroinvertebrates did not play a role in spore release from carcasses.
In vivo and in vitro studies on the viability and the infectivity to coots, Fulica americana, of Cyclocoelum mutabile metacercariae from three species of snails
Authors: McKindsey Christopher W. , Goring Jonas K. , McLaughlin J. Daniel
Published: May 2008

The host response to and the viability and infectivity of metacercariae of Cyclocoelum mutabile were examined in three species of pulmonate snails, Stagnicola elodes, Gyraulus parvus, and Promenetus exacuous. Host response was generally similar among snail species at 8 weeks post infection. Host responses increased with age of infection in S. elodes. There was no difference in the excystment success of metacercariae from each species at 8 weeks post infection. The mean excystment time in vitro was greater for metacercariae from S. elodes than for those from either G. parvus or P. exacuous at 8 weeks post infection. There were no differences in either excystment success or mean excystment time of metacercariae from 5-, 8-, and 30-week-old infections from S. elodes. The mean infection success of metacercariae from S. elodes was lower than that of metacercariae from G. parvus and P. exacuous in juvenile coots. Adult coots were less susceptible to infection than juveniles. There was no difference in the infection levels established in naive and previously infected adult coots.
Food-dependent aggregation and mobility of the water fleas Ceriodaphnia dubia and Daphnia pulex
Authors: Cuddington K. M. , McCauley E.
Published: May 2008

In this paper, we show that two freshwater cladoceran zooplankters (Ceriodaphnia dubia and Daphnia pulex) differ in swimming speed and ability to locate local regions of high food concentration in a flow-through circular chamber. This comparison is of general interest, since models of spatially structured predator–prey dynamics have predicted that differences in individual mobility and foraging behaviour may affect spatial distributions and, consequently, population dynamics. Daphnia pulex was more mobile than C. dubia, and also located the high end of a food gradient while C. dubia did not. It seems likely that the mechanisms used by D. pulex to locate these regions are related to ingestion and (or) filtering rates. It was hypothesized that individuals reduce their swimming speed in order to linger in regions of high food concentration. Differences in mobility and behaviour between C. dubia and D. pulex were used to generate hypotheses about the distribution and stability of their respective populations. Specifically, it was predicted that C. dubia populations would have a more aggregated and, consequently, a more stable population in smaller environments than D. pulex.
Seasonal and annual variation in brood attendance, prey type delivered to chicks, and foraging patterns of male Common Terns (Sterna hirundo)
Authors: Burness Gary P. , Morris Ralph D. , Bruce Jeffrey P.
Published: May 2008

The study took place over 2 years (1990 and 1991) on a concrete breakwater located 1 km offshore on Lake Erie near Port Colborne, Ontario. Ten male Common Terns (Sterna hirundo) in 1990 and 12 in 1991 were radio-tracked by boat or car during the chick-rearing stage. Concurrent behavioural observations of the radio-tagged birds and 23 additional control birds documented the time each sex spent away from or at the nest. The frequency and prey species/size composition of feeds to chicks were recorded. Individuals that carried transmitters had predictable foraging patterns. In peak- (clutch initiation in early May) and late-nesting males (clutch initiation in late June) intra-individual variability was low. Late-nesting males exhibited greater interindividual variability than peak-nesting males. Adults recaptured in 1991 exhibited similar foraging patterns to those they expressed in 1990. There were diurnal, seasonal, and interannual variations in prey delivered to chicks. We suggest that these were due to the temperature tolerances of the prey, rainbow smelt (Osmerus mordax) and emerald shiner (Notropis atherinoides), that controlled their vertical distribution in the water column, and to the presence of large schools of larval fish during the late nesting season.
Impact of the zebra mussel, Dreissena polymorpha, on populations of Unionidae (Bivalvia) in Lake St. Clair
Authors: Glllis P. L. , Mackie G. L.
Published: May 2008

Both density (number/m2) and species diversity of unionid populations in the southwestern region of Lake St. Clair have declined since the introduction of the epizoic zebra mussel (Dreissena polymorpha). The unionid population in the offshore waters of Puce, Ontario, was surveyed from 1990 to 1992. The density of living unionids decreased significantly [Formula: see text] from 1.75/m2in 1990 to 0.06 in 1991. The number of living species declined from 11 in 1990 to 4 in 1991. No living unionids were found at the Puce site in 1992. The decline in the unionid population corresponded to a significant increase in the number of attached zebra mussels. The average number of zebra mussels per unionid increased from 143 in 1989 to 642 in 1990. The unionid population in the offshore waters of Grosse Pointe Farms, Michigan, was surveyed in 1991 and 1992. The population declined from 1.98 unionids/m2 in 1991 to 1.36 in 1992, although this was only significant at p = 0.059. The average number of zebra mussels per unionid significantly increased from 9 in 1991 to 155 in 1992. Although thin, alate species of unionids appeared to decline sooner than species with more inflated and rounded shells, all species were affected, with an average of 64% of all dead unionid shells collected containing either living zebra mussels or their byssal threads.
Spacing, movements, and habitat selection of the river otter in boreal Alberta
Authors: Reid D. G. , Code T. E. , Reid A. C. H. , Herrero S. M.
Published: May 2008

Seasonal spacing patterns, home ranges, and movements of river otters (Lontra canadensis) were studied in boreal Alberta by means of radiotelemetry. Adult males occupied significantly larger annual home ranges than adult females. Males' ranges overlapped those of females and also each other's. In winter, home ranges of males shrank and showed less overlap. Otters often associated in groups, the core members typically being adult females with young, or adult males. Otters tended to be more solitary in winter. In winter, movement rates of all sex and age classes were similar, and much reduced for males compared with those in other seasons. These data indicated a strong limiting effect of winter ice on behaviour and dispersion. We tested the hypothesis that otters select water bodies in winter on the basis of the suitability of shoreline substrate and morphology for dens with access both to air and to water under ice. Intensity of selection was greatest in winter, with avoidance of gradually sloping shorelines of sand or gravel. Adults selected bog lakes with banked shores containing semi-aquatic mammal burrows, and lakes with beaver lodges. Subadults selected beaver-impounded streams. Apart from human harvest, winter habitats and food availability in such habitats are likely the two factors most strongly limiting otter density in boreal Alberta.