bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane Filtration – Fluorescent Antibody Staining Procedure for Detecting and Quantifying Renibacterium salmoninarum in Coelomic Fluid of Chinook Salmon (oncorhynchus tshawytscha)
Authors: Elliott Diane G. , Barila Theresa Y.
Published: April 2008

We developed a rapid method for detecting and quantifying the pathogen Renibacterium salmoninarum in coelomic fluid of spring chinook salmon (Oncorhynchus tshawytscha) by concentrating the bacteria on 0.2-μm polycarbonate filters and staining them with specific fluorescein-labeled antibody. Centrifugation of samples and resuspension of the sedimented material in phosphate-buffered saline containing Triton X-100 increased the ease of filtration. Background fluorescence was reduced by counterstaining filters with Eriochrome black T. Postfiltration staining, rinsing, and counterstaining were done in the syringe-mounted filter holders, reducing handling of the filters and possible loss of bacteria. The number of bacteria detected by the filtration – fluorescent antibody technique in a broth culture of R. salmoninarum ranged from 6.7 × 107to7.6 × 107/mL and was slightly higher than that determined by plate count (9.6 × 106/mL). Increasing the sample dilution or decreasing the number of microscope fields examined generally increased the variability of filter counts of R. salmoninarum. Using the filtration – fluorescent antibody technique, we detected the bacterium in the coelomic fluid of 85% of spawning female spring chinook salmon sampled from a hatchery population.
Scale Loss and Survival in Smolts of Atlantic Salmon (Salmo Salar) after Turbin Passage
Authors: Kostecki Paul T. , Clifford Patricia , Gloss Steven P. , Carlisle James C.
Published: April 2008

Field data obtained from smolts of Atlantic salmon (Salmo salar) passed through an Ossberger crossflow turbine indicated that scale loss was greater (24% of the total scaled surface area) in fish that died during the first 48 h after passage than in fish that survived longer than 48 h (16% scale loss) or in controls (15%). Histopathoiogy of selected tissues from turbine-passed fish revealed an incidence of lesions in brain and muscle greater than that detected by gross necropsy. The sensitivity of histologic examination approximately doubled the detection of damage among fish that survived longer than 48 h. Laboratory experiments indicated that an average scale loss of 27% increased mortality in fish held in freshwater. This increased mortality occurred after longer periods (8 d) than in the field, and we suggest that physical damage other than scale loss contributed to earlier mortality in turbine-passed fish.
Determination of Vitamin B6 Deficiency in Rainbow Trout (Salmo gairdneri) by Liver Enzyme Assay and HPLC Analysis
Authors: Hardy Ronald W. , Casillas Edmundo , Masumoto Toshiro
Published: April 2008

Rainbow trout (Salmo gairdneri), initially averaging 125 g, were fed a complete or a pyridoxine-deficient diet for 14 wk. Vitamin B6 status was evaluated biweekly by direct measurement of liver pyridoxine and pyridoxal levels by HPLC and by determining pyridoxal-5′-phosphate-enhanced liver aspartate aminotransferase (ASAT) activity. By 14 wk, mortality had severely reduced the number of fish remaining in the pyridoxine-deficient group. At 14 wk, no significant differences in liver pyridoxine and pyridoxal levels were detected between the trout fed the complete or pyridoxine-deficient diet. Significant differences between dietary groups are found in ASAT activity in liver and percent stimulation of liver ASAT by the addition of pyridoxal-5′-phosphate after 8 wk. Clinical signs of vitamin B6 deficiency including anorexia, listlessness, frantic and erratic swimming, and ataxia were observed after 11 wk of feeding a pyridoxine-deficient diet. This study shows that vitamin B6 deficiency in rainbow trout can be readily determined weeks before signs of clinical deficiency are apparent by measuring pyridoxine-enhanced liver ASAT activity. However, liver levels of pyridoxine and pyridoxal are not sensitive indicators of vitamin B6 status.
Adaptive Variation in Body Size, Age, Morphology, Egg Size, and Developmental Biology of Chum Salmon (Oncorhynchus keta) in British Columbia
Authors: Beacham T. D. , Murray C. B.
Published: April 2008

Chum salmon (Oncorhynchus keta) stocks in British Columbia spawning from August through January and in rivers of different size were surveyed for variation in sex ratios, age composition, meristic characters, morphology, and developmental biology. Males were more abundant than females at the younger (2 and 3 yr of age) and older (5 and 6 yr of age) age-classes. Males had larger heads, thicker caudal peduncles, and larger dorsal fins than did females, but females had larger anal fins than did males. Stocks from large rivers had larger heads, thicker caudal peduncles, and larger fins than did those from small rivers. Chum salmon in an area characterized by a lower number of gillrakers also had a lower number of branchiostegal rays. At the same incubation temperature, alevin hatching time was similar for all stocks examined except those from the Queen Charlotte Islands, which was later than the other stocks. Early-spawning stocks had older fish, larger eggs, and later times of fry emergence than did late-spawning stocks. Late-spawning stocks had higher survival rates of embryos at 4 °C than did early-spawning ones. Stocks had different trends in alevin and fry length and weight with respect to incubation temperature. Northern stocks were more efficient than southern stocks at converting egg yolk to fry body weight at low incubation temperatures (4 °C). Selection has produced stocks adapted to the various environments that they encounter in their natal streams, allowing chum salmon to exploit a wide variety of spawning habitats in British Columbia.
Use of Small, Temporary, Floodplain Tributaries by Juvenile Salmonids in a West Coast Rain-Forest Drainage Basin, Carnation Creek, British Columbia
Authors: Hartman G. F. , Brown T. G.
Published: April 2008

Seasonal movement of trout (Salmo clarki and S. gairdneri) into and out of three tributaries which drain areas ranging from 15 to 100 ha within the lower Carnation Creek catchment basin were monitored periodically from 1972 to 1985. The number of trout entering the three tributaries relative to total trout was as high as the number of coho salmon (Oncorhynchus kisutch) entering these tributaries relative to total coho. The percentage of the salmonid population represented by trout was highest in the two largest tributaries and lowest in the smallest. Trout were most clearly associated with nonvegetated sand and gravel bottom portions of the three tributaries. Coho were associated with this habitat too, but they also frequented portions of the tributaries that were vegetated and had a mud substrate. In the two largest tributaries, trout were represented by more age classes than were coho salmon. The paper considers some of the implications of use of small drainages by trout to habitat managers.
Abundance Estimation of a Dispersed, Dynamic Population: Hooded Seals (Cystophora cristata) in the Northwest Atlantic
Authors: Bowen W. D. , Myers R. A. , Hay K.
Published: April 2008

Pup production of hooded seals (Cystophora cristata) in the Northwest Atlantic was estimated by aerial survey. Simultaneous surveys and the collection of ground-truth data were conducted in March 1984 in both major whelping areas, namely the floe ice in the Davis Strait and off northeastern Newfoundland (the Front). Abundance estimates were obtained from both fixed-wing photographic and helicopter sighting surveys using a strip survey method for unequal-sized sampling units. These abundance estimates were corrected to account for pups which had left the ice and those pups which had yet to be born in each area. A maximum likelihood method was used to combine estimates of abundance from several surveys with estimates of the number of pups in each developmental stage to obtain an estimate of total production. This method weighted each survey point estimate of abundance by the estimated sampling variance and each estimate of the proportion of pups on the ice in each stage by the sample size corrected for loss of degrees of freedom associated with the sampling design. Total production at the Front was estimated to be 62 400 with 95% confidence limits of 43 700 to 89 400 and in the Davis Strait was 19 000 with a 95% confidence interval of 14 000 to 23 000. Total pup production estimates for the Front and Davis Strait are likely underestimates for several reasons, but are substantially higher than those previously assumed for the Northwest Atlantic.
Analysis of Mark–Recapture Data from Hatchery-Raised Salmon Using Log-Linear Models
Authors: Green Philip E. J. , Macdonald P. D. M.
Published: April 2008

Large numbers of hatchery-raised juvenile Pacific salmon are routinely marked with coded-wire tags before release from the hatchery. Log-linear models are an appropriate statistical technique to analyze the numbers of recaptures in different fisheries, and the numbers of tagged fish returning to the hatchery, in terms of such factors as brood year, treatment at the hatchery, timing of release, and size at release. Log-linear analysis of catches and hatchery returns of chinook salmon (Oncorhynchus tshawytscha) from Robertson Creek, British Columbia, indicates that all of these factors are important, but variation between brood years overrides all other factors. Within a brood year, the conditions that maximize the number of returns to the hatchery do not necessarily maximize the number of recaptures in the fishery. Log-linear analysis of hatchery returns from a designed experiment on a single brood year of coho salmon (O. kisutch) from Rosewall Creek, British Columbia, quantifies the effects of the various factors but will be of limited value until the causes of variations between brood years are better known.
Seminatural Rearing of Atlantic Salmon (Salmo salar) in Newfoundland
Authors: Pepper V. A. , Nicholls T. , Oliver N. P.
Published: April 2008

Atlantic salmon fry (Salmo salar) obtained from an artificial spawning channel and a deep-substrate incubator, were reared in mesh "troughs" in an artificial rearing channel and in floating lake cages. Fry placed in the lake cages were able to complete their first feeding phase on a diet of natural lake zooplankton but growth performance was improved when artifical diets were used to supplement natural food. Parr fed selectively on Daphnia catawba and mature Epischura lacustris. Parr reared in the mesh troughs were hand-fed a commercial diet. The 90-d average release weight ranged from 1.8 to 3.1 g for parr from the mesh troughs and from 0.9 to 3.1 g for parr from the lake cages. Growth of parr in these experiments resulted in an average weight advantage of approximately 2.3–4.5 times over parr captured from natural riverine habitat at the end of the experiment. Overall swim-up fry to fall-fingerling survival from these experiments was 52% in 1983 and 76% in 1984. Survival and growth varied inversely with density in the mesh trough experiments.
Behavioral and Biochemical Studies of Onset and Recovery from Acid Stress in Arctic Char (Salvelinus alpinus)
Authors: Jones Keith A. , Brown Scott B. , Hara Toshiaki J.
Published: April 2008

The time course of acid stress was followed in Arctic char (Salvelinus alpinus) exposed to pH 4.5 (HCl) for 2 wk and then returned to control conditions (pH 7.8). Behavioral parameters (activity, thigmotaxis, appetite, and attraction to a food extract) and blood parameters (hematocrit and plasma Cl−, Na+, osmolality, protein, cortisol, and glucose) were monitored. Reaction to the acid was evident in all parameters. Fish were initially hyperactive but became hypoactive with continued exposure. Thigmotaxis was generally greater in the acid-stressed fish than the controls. Feeding intensity and attraction to food extract were depressed throughout the exposure, but periods of partial recovery occurred. Hematocrit, protein, cortisol, and glucose increased, while osmolality, Cl−, and Na+ decreased in acid-exposed fish. Partial recovery occurred in some blood parameters during the latter part of the exposure. After return to control conditions, behavioral and blood parameters except cortisol recovered within 2 wk but might have recovered earlier if fish had not contracted a Saprolegnia infection. Extract attraction was negatively correlated with hematocrit, protein, cortisol, and glucose and positively correlated with plasma Cl. Activity was negatively correlated with plasma protein and glucose. Thigmotaxis was not correlated with any blood parameter.
Improved Estimation of the Dry Weight of Holopedium gibberum (Crustacea, Cladocera) Using Clutch Size, a Body Fat Index, and Lake Water Total Phosphorus Concentration
Authors: Yan N. D. , Mackie G. L.
Published: April 2008

Holopedium gibberum is one of the most important species of crustacean zooplankton in Canadian Shield lakes, yet satisfactory length–weight relationships (LWR's) have not been constructed from North American populations. In this report we show that, despite assertions to the contrary, weights of individual H. gibberum can be successfully predicted from body length (L) of animals measured in a nonanaesthetized, relaxed position. We use a relationship between postabdomen length and L to show that LWR's of Ontario and Scandinavian populations of H. gibberum differ. As such differences among lakes are the rule and not the exception, it is not safe to assume that published LWR's for zooplankton are widely applicable. Consideration of clutch size (CS) and a body fat index (BFI) in addition to L significantly improved estimates of the dry weight of Holopedium from Plastic Lake in central Ontario. This model provided more accurate estimates of Holopedium dry weight in 29 test lakes than the simple LWR, i.e. it had wider applicability. Predicted weights in the test lakes were further improved by consideration of lake water total phosphorus concentrations.
Relationship between Bioenergetics and Behavior in Anadromous Fish Migrations
Authors: Bernatchez Louis , Dodson Julian J.
Published: April 2008

Minimizing energetic cost per unit distance is often considered the major criterion that anadromous migrants seek to optimize during upstream migration. To test this theory, we documented energetic expenditures and travel speeds of 15 anadromous fish populations involving 9 species observed during their upstream migration. Parameters that characterized fish migratory behavior and the spawning river were calculated for each population. In most cases, cost per unit distance is not minimized and migratory strategy does not conform to the theoretical optimum. Populations that make long or difficult migrations are more efficient in their use of energy reserves than populations that make shorter migrations. Only populations that need all their energy to complete the migration swim at speeds that approach the theoretical optimum. Migration length may lead to improved migratory efficiency by selecting for larger body size, more accurate upstream orientation, and travel speeds that optimize energy efficiency. The failure to minimize energy expenditures is sometimes due to environmental constraints that exceed the physiological capacities of migrants. Minimizing the probablity of death due to exhaustion may be the major factor determining migratory behavior. Selection for energetic efficiency appears important only in cases where energy reserves are exhausted during migration.
Physiological Changes during Seaward Migration of Wild Juvenile Coho Salmon (Oncorhynchus kisutch)
Authors: Rodgers Jeffrey D. , Ewing Richard D. , Hall James D.
Published: April 2008

Peaks in migration of wild juvenile coho salmon (Oncorhynchus kisutch) from Knowles Creek (Siuslaw River, Oregon) occurred in November and May. Condition factor of nonmigrant fish was higher than migrants or captives throughout the study. Skin guanine levels of migrant fish rose sharply during the first 2 wk of April and continued to rise through June. Gill (Na + K)-ATPase specific activity of migrants rose gradually from a low in January to a maximum in June. Gill (Na + K)-ATPase activity of migrants and nonmigrants was low and not significantly different during November to mid-March. During April, however, gill ATPase activity of migrants rose to become significantly higher than that of nonmigrants until the first 2 wk of May. Cyclic changes in gill (Na + K)-ATPase activity was not observed in these fish. Gill (Na + K)-ATPase activity of fish reared in a laboratory was similar to that of wild nonmigrants until it peaked during the last 2 wk of April, after which the specific activity was lower than either migrants or nonmigrants.
Lentic Spawning by the Pacific Lamprey, Lampetra tridentata
Authors: Russell J. E. , Beamish F. W. H. , Beamish R. J.
Published: April 2008

Anadromous Pacific lamprey, Lampetra tridentata, typically construct nests and reproduce in lotic environments. In the summer of 1984, Pacific lamprey were observed spawning in shallow lentic water in two regions of the Babine Lake system, British Columbia. Nests were subject to wave action but an obvious unidirectional flow was not observed.
Test of Biotic and Abiotic Environmental Determinants of Amphipod (Hyalella azteca) Preamplexus
Authors: France R. L.
Published: April 2008

Variation in reproductive behavior (preamplexus) of the amphipod Hyalella azteca among 10 Canadian Shield lakes in Ontario was positively correlated with water temperature, possibly through its influence on either activity patterns or diapausal endocrinology. Intensity of preamplexus was not correlated with other abiotic variables including lake pH, alkalinity, total phosphorus, or chlorophyll a concentration. Similarly, the complicated evolutionary "strategies" suggested by Strong involving alterations in optimal mating tactics in response to differences in intensity offish predation, amphipod density, or habitat heterogeneity did not occur in these lakes.
Lack of Genetic Stock Discretion in Pacific Cod (Gadus macrocephalus)
Authors: Grant W. Stewart , Zhang Chang Ik , Kobayashi Tokimasa , Ståhl Gunnar
Published: April 2008

We examined the ocean-wide genetic population structure of Pacific cod (Gadus macrocephalus) using electrophoretically detectable population markers at 41 protein loci. Samples were collected at 11 locations extending over most of the species's range from the Yellow Sea, Korea, to Puget Sound, Washington. Seven loci (17%) were polymorphic using the 0.05 criterion of polymorphism. Sample heterozygosities ranged from 0.018 to 0.041 and averaged 0.025 (±0.013). Two major genetic groups were detected: a western North Pacific Ocean (Asian) group and an eastern North Pacific group (including Bering Sea stocks). The UPGMA Nei genetic distance, D, (based on 41 loci) between samples from these two groups was 0.025, and this subdivision accounted for 18.9% of the total gene diversity. Genetic differentiation between these two groups appears to reflect the barrier effects of coastal Pleistocene glaciation. Morphological and tagging data from other studies suggest that Pacific cod are subdivided into several independent stocks. In this study, significant allele-frequency differences were detected between samples within the eastern North Pacific Ocean, the Bering Sea, and the western North Pacific Ocean, but not between stocks on a larger geographic scale. The average Nei genetic distance (based on 41 loci) between samples was only 0.0007, and a gene diversity analysis indicated that within-region differences represented only 3.1% of the total gene diversity. There was a slightly greater amount of differentiation between the Yellow Sea and the Sea of Japan (D = 0.0041), which reflects geographic isolation of the Yellow Sea stock not found in other areas. From theoretical considerations, little genetic divergence between stocks of Pacific Cod is expected because random genetic drift in large population sizes is insignificant and because migration between areas prevents genetic differentiation.
Dynamics of Lake Michigan Phytoplankton: Primary Production and Growth
Authors: Fahnenstiel Gary L , Scavia Donald
Published: April 2008

Primary production was measured with the 14C technique during May through July–August 1982–84. 14C experiments varied from short-term incubations (1–2 h) in a photosynthesis–irradiance (P–I) chamber to 24-h in situ incubations. The maximum assimilation number from six P–I experiments during thermal stratification averaged 2.1 mg C∙mg Chl−1∙h−1 which agreed well with estimates from the 1970s. Chlorophyll-corrected P–I curves were combined with incident irradiation, chlorophyll concentrations, and extinction coefficients to estimate daily production (model estimate). Summer average integral production estimates in 1983 and 1984 were 615–630 mg C∙m−2∙d−1. Approximately 50% of summer primary production occurred below the epilimnion. Daily model production estimates were higher than 24-h in situ estimates at light intensities above Ik, the light saturation parameter, and similar at intensities below Ik. Comparisons of production estimates converted to growth rates suggest that 24-h in situ estimates provide a measure close to net production whereas model estimates provide a measure greater than net production. Summer epilimnetic growth rate estimates were low (range 0.06–0.60∙d−1), reflecting the limited availability of phosphorus.
Dynamics of Lake Michigan Phytoplankton: Recent Changes in Surface and Deep Communities
Authors: Fahnenstiel Gary L. , Scavia Donald
Published: April 2008

Lake Michigan phytoplankton dynamics were studied from the end of spring isothermal mixing (May) through midstratification (July–August) in 1982–84. Phytoplankton composition shifted from a diatom-dominated community (75% of phytoplankton carbon) during May to a phytoflagellate-dominated community (71% of phytoplankton carbon) during July–August. This summer phytoflagellate dominance in the 1980s is distinctly different from the summer blue-green and green algae dominance in the 1970s. Foodweb interactions caused by a changing zooplankton composition and nutrient supply changes were two possible causes. A deep chlorophyll layer (DCL) developed after the onset of thermal stratification. The DCL initially developed in the 15–30 m region and deepended to 25–50 m in July and the 40–70 m region in August. The DCL in 1982–84 was larger in size and located deeper in the water column than those reported from the 1970s. This difference was related to increases in light transparency found in the 1980s that were a result of increased zooplankton grazing pressure.
Long-Term Changes in the Macrobenthos of Southern Lake Michigan
Authors: Nalepa Thomas F.
Published: April 2008

A benthic survey of 40 stations in southern Lake Michigan in 1980–81 was compared with results of studies conducted in the mid-1960's to evaluate long-term trends in populations. The three major benthic groups, Pontoporeia, oligochaetes, and sphaeriids, were significantly more abundant in 1980–81. Compared with the most comprehensive survey (conducted in 1964–67), Pontoporeia increased two- to fivefold at depths less than 50 m, but did not increase at depths greater than 50 m. Oligochaetes increased two- to threefold regardless of sampling depth, while sphaeriids increased twofold at depths less than 50 m but decreased somewhat at depths greater than 50 m. Although oligochaete abundances increased, overall shifts in species composition were not apparent. Changes in abundances of Pontoporeia may have been related to shifts in predation pressure from forage fish populations, but increased oligochaete abundances can likely be related to increased enrichment between the two sampling periods. Although apparent improvements in the water quality of Lake Michigan since the mid-1970's were not yet reflected by benthic populations in 1980–81, continued monitoring of the benthos should provide a useful indicator of future trends.
Ion Mass Balances and Seasonal Fluxes from Four Acidic Brownwater Streams in Nova Scotia
Authors: Freedman B. , Clair T. A.
Published: April 2008

Precipitation and four brownwater streams in southwestern Nova Scotia were sampled for 3–5 yr. Precipitation cation chemistry was dominated by H+ (44% of cation equivalents) and Na+ (38%), while anions were dominated by Cl− (44%), SO42− (41%), and NO3− (15%); mean annual pH was 4.6, and acidity was correlated with concentrations of SO42− (r = 0.90) and NO3− (r = 0.82). Surface water chemistry was dominated by Na+ (51% of cation equivalents), Mg2+ (17%), and Ca2+ (16%), while H+ averaged only 4%; anions were dominated by Cl− (53%), organic anions (23%), and SO42− (21%); H+ was not strongly related to concentrations of other ionic constituents (the most consistent correlation was with sulfate, but this was weak and accounted for <30% of the variation). Hydrogen ion was consumed in all four watersheds by an average value of >75%. Water flow was by far the strongest determinant of annual pattern of flux of chemical constituents from the watersheds. Seasonal variations of concentration were of relatively small magnitude and had much less influence on patterns of flux.
Food Conditioning and Prey Selection by Young Yellow Perch (Perca flavescens)
Authors: Mills Edward L. , Widzowski Daniel V. , Jones Suzanne R.
Published: April 2008

We tested how diet conditioning influences prey species selection by age-0 yellow perch (Perca flavescens) in laboratory experiments. We conditioned yellow perch to diets of different ratios of Daphnia pulex and Diaptomus sicilis and then offered them an experimental 1:1 test mixture of each prey. The influence of conditioning on prey selection was found not to be random, and prey were consumed neither in proportion to the 1:1 test mix nor to the ratio of prey in the conditioning diet. Young yellow perch switched to novel prey and did not specialize on the most frequently encountered prey in conditioning diets. However, when yellow perch were conditioned and tested on the 1:1 Diaptomus to Daphnia mix, these fish selected Diaptomus until they reached 35–40 mm total length when they switched to the larger bodied Daphnia. We hypothesize that young yellow perch may switch to novel prey because nutritional advantages associated with diet breadth may outweigh the advantage of feeding on familiar prey.
Genetic Variation and Postglacial Dispersal of Populations of Northern Pike (Esox lucius) in North America
Authors: Seeb James E. , Seeb Lisa W. , Oates David W. , Utter Fred M.
Published: April 2008

We studied the genetic relationships and postglacial dispersal of northern pike (Esox lucius) populations in North America using allozyme data. Allelic products of up to 65 protein coding loci were examined in eight populations: five from drainages in western Canada, flowing into Hudson Bay and the Beaufort Sea; two from the Missouri River drainage, flowing into the Mississippi River; and one from the upper Mississippi River drainage, flowing into the Gulf of Mexico. Only two polymorphic loci were identified, Est-1 and Ck-1, and the average observed heterozygosity was only 0.001, much lower than that observed in most teleosts. All of the populations from the drainages in western Canada and the Missouri River were genetically identical. The Mississippi River population was unique, expressing Ck-1 (140), an allele nearly absent in all other populations, at a frequency of 0.99. Our data suggest that the Missouri River drainage, during the period when it was isolated from the Mississippi River, was the southern refugium from which northern pike radiated during deglaciation.
Genetic Structure of Anadromous Cutthroat Trout (Salmo clarki clarki) Populations in the Puget Sound Area: Evidence for Restricted Gene Flow
Authors: Campton Donald E. , Utter Fred M.
Published: April 2008

Genetic relationships among anadromous populations of coastal cutthroat trout (Salmo clarki clarki) in the Puget Sound area (United States) were investigated by electrophoretic methods between successive year classes within streams (populations), among streams within drainages, between drainages within each of two regions separated by Puget Sound, and between the two regions. Average allele frequencies for fish from the two regions differed by approximately 0.10 at several polymorphic loci, suggesting that gene flow between the two regions is restricted. Despite this divergence, the sampled populations were all very similar genetically (Nei's I > 0.97), possibly reflecting a common ancestral invasion following Pleistocene glaciation. The total gene diversity (expected heterozygosity) was 0.101 and was partitioned as follows: between regions, 1.24%; between drainages, 1.01%; among streams, 2.41%; between year classes, 1.17%; within individual year class samples, 94.2%. In addition, stream effects were significant in 7 of 12 intralocus ANOVA comparisons, suggesting that populations were structured genetically at this level of subdivision. This latter result may be reflecting the homing instinct of spawning adults.
Maximum Likelihood Estimation of Mixed Stock Fishery Composition
Authors: Millar Russell B.
Published: April 2008

In this paper the maximum likelihood method of estimating stock composition is initially presented under the assumption that all of the sampled characteristics are of discrete type (electrophoretic, meristic). The extension to allow continuous data (morphometric) is seen to follow from just a slight change in notation. It is shown that the classification method with error correction is a special case of the maximum likelihood method. Results from finite mixture theory are used to show that, in practice, the method is well defined and that the maximum likelihood estimates of composition are unique and can always be found using the EM (expectation–maximization) algorithm. A comprehensive discussion of the reliability of the estimates is undertaken. An explicit nonparametric (infinitesimal jackknife) estimator of estimate variability is presented. Procedures to reduce variance and bias are discussed. The composition of a test mixed stock fishery is estimated and many of the techniques proposed in the reliability discussion are used.
Reductions in Submersed Macrophyte Biomass and Species Richness by the Crayfish Orconectes rusticus
Authors: Lodge David M. , Lorman James G.
Published: April 2008

We conducted five 4- to 12-wk in situ enclosure–exclosure experiments in four macrophyte assemblages in three northern Wisconsin lakes to test the impact of grazing by the crayfish Orconectes rusticus. Size of cages and cageless controls ranged from 1 to 3 m2. Adult crayfish reduced total macrophyte biomass in two experiments and reduced species richness in three experiments. The natural occurrence of crayfish in the study lakes ranged from 1 to 223 g live crayfish∙m−2. Crayfish abundance of 19 g∙m−2 reduced total macrophyte biomass 64%, while abundance >140 g∙m−2 eliminated all macrophytes. Decline in species richness and comparison of species abundance over time suggested that crayfish grazed selectively. Both consumptive and nonconsumptive destruction by crayfish caused macrophyte decline. Single-stemmed species were more susceptible to destruction than rosulate or branched species. Our results suggest that crayfish play an important role in structuring the macrophyte and invertebrate communities that they inhabit.
Frequency Domain Filtering of Age-Structured Population Data
Authors: Welch David W.
Published: April 2008

A new approach is described for removing part of the density-independent noise present in stock–recruitment (SR) data. The method is based on filtering the time series of recruitment data in the frequency domain, an approach that allows complete removal of the identifiable environmental noise without reducing the length of the time series. Results from Monte Carlo simulations demonstrate that recruitment filtering allows more reliable estimation of SR parameters than is possible without filtering and that negligible bias is introduced into the parameter estimates obtained for commonly used SR models.
Natural Killer Cell Activity in Rainbow Trout (Salmo gairdneri): Effect of Dietary Exposure to Aroclor 1254 and/or Mirex
Authors: Cleland Glenn B. , Sonstegard Ronald A.
Published: April 2008

Rainbow trout (Salmo gairdneri) peripheral blood lymphocytes and splenocytes were found to have spontaneous cytotoxic activity against cultured mammalian and fish tumor cell lines. P 815 and YAC 1 target cells were found to be highly sensitive to trout natural killer (NK) cell lysis, while K 562 and ML cells were low and EL 4 was resistant. NK cell activity was not significantly altered by a 12-mo dietary exposure of fish to various concentrations of Aroclor 1254 and/or mirex.
Factors Influencing the Distribution of Phytoplankton in 97 Headwater Lakes in Insular Newfoundland
Authors: Earle J. C. , Duthie H. C. , Scruton David A.
Published: April 2008

Phytoplankton samples collected from 97 headwater lakes throughout insular Newfoundland were analyzed and used as a basis for a statistical evaluation of the environmental factors influencing species distributions. A selected subset of 77 taxa were clustered using a complete-linkage cluster analysis. The final 12 clusters represent the associations of species found occurring together in insular Newfoundland. Physical, chemical, and morphometric data collected with the phytoplankton served to characterize the environment. Factor analysis simplified the original variables, many of which were highly correlated and uninterpretable, into seven derived environmental factors: dystrophy, hardness, salinity, lake size, season, watershed influence, and orthophosphate enrichment. The resulting orthogonally rotated (VARIMAX) scores comprising these seven factors were correlated with species abundances. Spearman correlations showed several relationships between species distributions and the seven derived environmental factors. Although the analysis identified a subset of naturally acidic, dystrophic lakes, it failed to reveal any evidence of anthropogenic acidification in the lakes studied. For the most part, the members from each of the cluster groups demonstrated similar relationships with the derived environmental factors. The evidence suggests that the cluster groups may represent species associations; groups of species that co-occur because of their common requirements for specific environmental conditions. Phytoplankton autecological findings resulting from this study of insular Newfoundland lakes correspond well with conclusions derived independently from a comparable study of 95 headwater lakes in Labrador.
Factors Influencing Plankton Community Structure and Production in Freshwater Lakes
Authors: Paloheimo J. E. , Fulthorpe R. R.
Published: April 2008

Relationships among biomasses and levels of production of nannoplankton, netplankton, herbivorous zooplankton, and carnivorous zooplankton, as well their dependence on environmental parameters, were studied in 26 central Ontario lakes. Planktonic biomasses were only weakly correlated with each other. Correlations were improved by converting biomasses to production estimates using size-specific turnover rate corrections on size-structured data. Further use of size-structured data was of limited value. Sets of environmental parameters, particularly the water chemistry data, were better predictors of planktonic biomasses and productions than other biotic (predator/prey) data. Total Kjeldahl nitrogen was a better predictor of total plankton production estimates than total phosphorus. Lakes could not be clustered into stable community types due to the large year-to-year fluctuations in the data.
Influence of Cu, Cd, and Zn Preexposure on Hg Toxicity in the Mussel Mytilus edulis
Authors: Roesijadi G. , Fellingham G. W.
Published: April 2008

Prior exposure of the marine mussel Mytilus edulis to Cu, Cd, or Zn conferred increased tolerance to the toxicity of inorganic Hg. This acquired tolerance could, in part, be attributed to the apparent induction of metallothionein-like proteins during the preexposure, it appeared that some prior conditions must be satisfied during the preexposure for the enhanced tolerance to be elicited: (1) preexposure had to be sufficiently high that metal bioaccumulation occurred; this presumably initiated cellular compensatory responses; (2) preexposure had to be below levels which could itself become a major component to toxicity. Effective preexposure concentrations fell within this range of concentrations.
Viral Erythrocytic Inclusion Body Syndrome (EIBS) Occurring in Juvenile Spring Chinook Salmon (Oncorhynchus tshawytscha) Reared in Freshwater
Authors: Leek Steve L.
Published: April 2008

Erythrocytic inclusions in the blood of spring chinook salmon (Oncorhynchus tshawytscha) are the first confirmed occurrence of a natural infection caused by an erythrocytic necrosis virus in a population being reared in freshwater. The erythrocytic inclusion bodies ranged in size from 0.8 to 3 μm. Pinacyanol chloride stained the inclusions a pale purple. The viral particle size averaged 75 nm in diameter, and they were scattered randomly in the cytoplasm.
Effects of Photoperiod, Temperature, and Diet on the Reconditioning Response, Blood Chemistry, and Gonad Maturation of Atlantic Salmon Kelts (Salmo salar) Held in Freshwater
Authors: Johnston C. E. , Gray R. W. , McLennan A. , Paterson A.
Published: April 2008

Changes in feeding behavior, rate of reconditioning, gonadal development, and maturation were investigated together with changes in plasma electrolytes, triglycerides, cholesterol, protein, and alkaline phosphatase in female Atlantic salmon kelts (Salmo salar) exposed to advanced and simulated natural photoperiods and warmer and natural water temperatures. Natural photoperiod cycles at natural and 12 °C temperatures were most stimulatory for feeding behavior, reconditioning, gonadal development, and maturation. Advancing photoperiod only slightly stimulated gametogenesis at 12 °C whereas at low temperature, vitellogenesis did not proceed and oocyte maturation did not occur. In all regimes, early reconditioning was associated with gonadal maturation. The levels of calcium, triglycerides, and alkaline phosphatase were markedly elevated in spawners and were coincident with temperature and photoperiod manipulation. No similar change occurred in nonspawners. Ovulation occurred earliest in the advanced photoperiod and 12 °C temperature regime, suggesting an effect of both temperature and photoperiod on the rate of gonadal maturation. The factors influencing egg production and maturation in Atlantic salmon kelts are also discussed.
Highly Specialized Nitrogen Metabolism in a Freshwater Phytoplankter, Chrysochromulina breviturrita
Authors: Wehr John D. , Brown Lewis M. , O'Grady Kathryn
Published: April 2008

A field and laboratory culture study was carried out on the nitrogen metabolism of isolates of the freshwater phytoplankter Chrysochromulina breviturrita Nich. (Prymnesiophyceae). These were isolated from two different softwater lakes, one believed to be influenced by acidic precipitation (Cinder Lake) and another which was experimentally acidified with H2SO4 (Lake 302-South). The alga was able to utilize only NH4+ as an inorganic N source. A range of irradiances and molybdenum concentrations failed to induce NO3− utilization. Among 17 organic N compounds including amino acids, purines, and other amines, only urea plus Ni2+ as a cofactor would serve as the sole N source for this species. Nonetheless, growth rates in media supplied with urea were significantly less than with NH4+. Field data from Lake 302-S indicate that a predominance of NH4+ versus NO3− as the major inorganic N species may have favored the development of a Chrysochromulina-dominated community during August 1984. A detailed depth profile also indicated that a metalimnetic peak (> 20 × 106 cells/L) of this alga coincided with a distinct NH4+ depletion, which occurred at no other time during the year. Experiments with isolates of C. breviturrita and a Nannochloris sp. (Chlorophyceae) (~ 1 μm in diameter) from this community indicated that the former alga possessed a highly specialized N metabolism much like the Cinder Lake isolate. The Nannochloris sp. from the same environment grew on NO3− and NH4+ equally well. It is suggested that the specialized NH4+ utilization by C. breviturrita may itself influence the pH regime of poorly buffered waters through selective NH4+ uptake and H+ generation.
Nitrification: A Significant Cause of Oxygen Depletion Under Winter Ice
Authors: Knowles Roger , Lean David R. S.
Published: April 2008

Changes in concentrations of ammonium, nitrite, nitrate, and oxygen suggested the occurrence of significant nitrification throughout the water column of mesotrophic Lake St. George, Ontario, during the winter months from 1976 to 1984. The existence of nitrapyrin- and acetylene-sensitive 14C-bicarbonate incorporation confirmed that bacterial nitrification occurred. During late January to early March (water temperature 2–3 °C), nitrification occurred at an average rate of about 13 μg N∙L−1∙d−1 for the years studied. Numbers of detectable nitrifying bacteria appeared too low (by 2 to 4 orders of magnitude) to account for the observed activity. The nitrification activity observed would result in average oxygen consumption amounting to 71% of the observed oxygen depletion. This shows that winter nitrification can be an important factor in promoting oxygen depletion and possibly winter-kill of fish.
Measurements of Specific Rates of Net Methyl Mercury Production in the Water Column and Surface Sediments of Acidified and Circumneutral Lakes
Authors: Xun Luying , Campbell N. E. R. , Rudd John W. M.
Published: April 2008

Specific rates of mercury methylation and demethylation were determined for water and surficial sediment samples taken from several lakes located in the Experimental Lakes Area, northwestern Ontario. Specific rates of mercury methylation were found to increase with decreasing pH in epilimnetic water samples in which pH was adjusted prior to incubation and in epilimnetic water samples taken from lakes of different pH. Reduction of pH also increased methyl mercury production at the sediment surface. Both increases and decreases in pH reduced specific rates of mercury demethylation. However, these changes were smaller than for methylation. Proportionally, specific rates of methylation increased faster than increasing concentrations of Hg2+, while specific rates of mercury demethylation increased linearly with increasing concentrations of methyl mercury. Overall, this study predicts that the net rate of methyl mercury production in the water column and at the sediment–water surface will increase as a result of lake acidification, and this may at least partially explain why the mercury concentration of fish appears to increase during lake acidification.
Genetic Relationships among Populations of Alaskan Chinook Salmon (Oncorhynchus tshawytscha)
Authors: Gharrett A. J. , Shirley S. M. , Tromble G. R.
Published: April 2008

Chinook salmon (Oncorhynchus tshawytscha) collected from 13 Alaskan drainages were genetically characterized at 28 protein coding loci using starch–gel electrophoresis. Chinook salmon in western Alaska are generally quite similar to each other but are distinct from the more diverse southeastern Alaskan populations. Genetic compositions of southeastern Alaskan populations are generally intermediate between those of western Alaska and previously studied non-Alaskan populations to the south. Given that chinook salmon survived the Wisconsin glaciation in both the Bering and Pacific refuges, we propose that chinook salmon from both refuges participated in the post-Wisconsin colonization of southeastern Alaskan rivers.
Comparing Imprecise Abundance Indices with a Symmetric Model
Authors: Richards Laura J.
Published: April 2008

Richards and Schnute (1986. Can. J. Fish. Aquat. Sci. 43: 1214–1227) presented an errors-in-variables model for testing the assumption that catch per unit effort (CPUE) is an index of stock abundance. Here, I generalize the model and extend its application to any pair of abundance indices for which the ratio of variances in the two indices can be estimated. I used the model to relate density indices from two years, CPUE values from two years, and the two CPUE–density combinations. Density estimates of nearshore reef fishes from the strait of Georgia, British Columbia, were obtained by SCUBA, and CPUE estimates were obtained by angling at the same sites. Among-site differences in both CPUE and density tended to be consistent between years. For quillback rockfish (Sebastes maliger), the relationship between CPUE and density was one of strict proportionality, as found by Richards and Schute over a different depth range.
Dynamics of Drift and Microdistribution of Two Mayfly Populations: A Predictive Model
Authors: Ciborowski Jan J. H.
Published: April 2008

A model is derived to predict changes in larval microdistribution of Ephemerella inermis Eaton and Baetis tricaudatus Dodds (Ephemeroptera) that result from drift. Transport by drift was assumed to be a Markov process. Estimates of departure from the substrate, downstream movement, and lateral transport were combined to produce transition matrices from which changes in microdistribution, magnitude of drift, and mean daily downstream displacement of live and dead animals were determined. Predictions from the model were compared with observations made in a river similar in composition to the area modelled. There were marked differences between expected drift of living versus dead animals; estimates for drift of living animals corresponded most closely to values observed in the field. Predicted drift either corresponded to or was less than observed levels. Observed changes in benthic microdistribution were minimal, but the model predicted large-scale relocation of animals toward river margins. Thus, magnitude and spatial pattern of drift could be adequately modelled but benthic distribution could not. Drift is an important redistribution mechanism but animals must have a complementary ability to actively travel towards the river center to maintain constant benthic distribution patterns. Inhibition of movement during floods should produce increased abundance at margins. During stable flow conditions, drift and benthic activity probably act together to produce and maintain microdistributional patterns among vagile organisms. In contrast, drift of invertebrates possessing poor locomotory ability probably reflects larger-scale, permanent displacement events that are a normal aspect of development, or the outcome of aggressive interactions.
Thermally Modulated Biliary Excretion of [14C]Taurocholate in Rainbow Trout (Salmo gairdneri) and the Na+,K+-ATPase
Authors: Kemp Christopher J. , Curtis Lawrence R.
Published: April 2008

Biliary excretion rate of [14C]taurocholate was 53–63% greater in rainbow trout (Salmo gairdneri) acclimated to and tested at 18 than 14 or 10 °C. Acute 4° temperature shifts up or down increased or decreased respectively biliary excretion rate by 40–53%. Furthermore, 10 °C acclimated fish shifted to 14 °C had 125% greater biliary excretion rate than 18 °C acclimated fish shifted to 14 °C. Apparent hepatic blood flow was greater in fish acclimated to and measured at 18 than 14 or 10 °C but was not different when 10 or 18 °C acclimated fish were measured at 14 °C. Acclimation to 10 versus 18 °C did not affect the Vmax or the temperature/activity relationship for the liver plasma membrane (LPM) Na+,K+-ATPase or the LPM Mg2+ -ATPase but did cause a major shift in the Km of the Na+,K+-ATPase (0.14 and 1.11 mM, respectively). This Km shift was observed at an 18 °C but not a 37 °C assay temperature. Thus, acclimation-induced changes in this enzyme were only observable at physiologically relevant temperature and substrate conditions. Depending on the thermal treatment, both hepatic blood flow and LMP Na+,K+-ATPase may module biliary excretion.