bluuebunny/crossref_metadata_2025 huggingface dataset:
Heavy Metals in Tissues and Organs of the Narwhal (Monodon monoceros)
Authors: Wagemann R. , Snow N. B. , Lutz A. , Scott D. P.
Published: April 2011

Sixty narwhals (Monodon monoceros) were sampled in the vicinity of Pond Inlet, N.W.T., during the summer of 1978 and 1979. Concentrations of Pb, Cu, Cd, Hg, Se, As, and Zn were measured in liver, kidney, muscle, and blubber. All elements except As were lowest in concentration in the blubber and highest in kidney and liver; Cd and Zn were generally higher in kidney than in liver, while the converse was true for Pb, Cu, and Hg. Cadmium levels in liver and kidney had high interanimal variability but were generally higher than would be expected based on existing marine mammal Cd content data. Certain metals were correlated with animal size and sex. Mercury in kidney, muscle, and blubber and Cd in muscle appear to accumulate during growth. A number of interelement associations with extremely high probabilities were found: among them, that between Hg and Se and Cd and Zn in liver and kidney tissues. The latter association is thought to be related to the presence of metallothionein. The data presented are discussed in terms of what little is known of the biology of the narwhal and represent a baseline for a resource organism which is harvested in an area already subject to mining activity, the level of which is due to increase in the future.
Coupling of Organic Pollutants Between the Estuary and Continental Shelf and the Sediments and Water Column in the New York Bight Region
Authors: Boehm Paul D.
Published: April 2011

The composition and distribution of polynuclear aromatic hydrocarbons (PAH), poly-chlorinated biphenyls (PCB), and coprostanol in suspended particulate matter in the Hudson River–Lower Bay–New York Bight system were investigated. Fused silica capillary gas chromatography and gas chromatographic mass spectrometry were employed for PAH, PCB, and coprostanol determinations. Additionally, dredged material and sewage sludge waste deposits from the bight were size fractionated and analyzed. Between the estuary and shelf and between the benthos and water column, chemical flux mechanisms included Hudson River sediment resuspension and bottom water transport within the estuary, sewage effluent input to harbour–river surface waters followed by seaward transport, landward transport of resuspended bight sediment linked to resuspension of PAH-rich dredged material, and possible transport of sewage-associated organics down the Hudson Valley. The composition of PAH and PCB varied with sediment grain size. Dredged materials were rich in pyrogenic PAH, while PAH in sewage sludge were mainly of a petroleum origin. PAH, PCB, and coprostanol levels were decoupled in the water column particles, probably due to differential solubility behavior of the three compound classes.
Can the Oceans Be Protected?
Authors: Goldberg Edward D.
Published: April 2011

Effective regulation of marine pollutants is now hampered by problems associated with the magnitude of man's activities. Increasing numbers and quantities of contaminants lead to increasing uncertainties about sources and inputs, more interaction between pollutants and between pollutants and organisms, and increasing difficulties in elucidating the dynamics of contaminants. The examples of global toxaphene contamination, coastal eutrophication, and continuing use of chlorinated hydrocarbons are used to illustrate an optimistic prognosis and a need for increased levels of funding for ocean studies, long-term studies of ecological processes of unperturbed systems, greater involvement of international agencies, and refinement of remote sensing techniques.
Incubation of the Eggs of Atlantic Salmon, Salmo salar, at Low Temperatures
Authors: Heggberget Tor G. , Wallace Jeff C.
Published: April 2011

Eggs of Atlantic salmon (Salmo salar) from the River Alta in northern Norway were subjected to three experimental temperature regimes during prehatching incubation. Two of these were intended to simulate possible temperature situations in the river after hydroelectrical development of its upper reaches. The third temperature regime was that of the natural river. The results indicated that hydroelectrical development of the Alta may lead to an earlier hatch of the salmon embryos in the river. Incubation time, and perhaps also a "trigger" such as rising temperature, may be more important than the heat sum (degree-days) of the incubation period in determining the exact timing of the hatch.
Patterns in Growth and Smolting of Atlantic Salmon (Salmo salar) Parr
Authors: Evans Geoffrey T. , Rice Jake C. , Chadwick E. Michael P.
Published: April 2011

A simple model of growth and smolting of Atlantic salmon (Salmo salar) parr in Western Arm Brook (northern Newfoundland) can account for the distributions of ages and lengths of random samples of sea-run smolts collected over 10 yr. The parameters of the model determine growth rate, survival rate, and the length that a parr must attain to smolt at age 3 or 4. The parameters are specific to a year-class, not a calendar year, and vary between year-classes. To account for the observed patterns, it is necessary to assume that the criterion length for smolting is different for age 3 and age 4 parr. The variation between year-classes is as great for the criterion length for an age 3 smolt as for the expected length of an age 3 parr, and similarly for age 4. The best estimate of survival rate generally does not vary between year-classes.
An Improved Photo-Electric Fish Egg Counter
Authors: Tanasichuk R. W. , Armstrong C. , Ware D. M.
Published: April 2011

We describe an improved design and operating procedure for a photo-electric fish egg counter. The design was simplified so that the apparatus can function as a flow-through system using tap water. The procedure for operating the counter was changed so that coincidence counting can be corrected for. Triplicate fecundity determinations, made gravimetrically for 10 randomly selected Pacific herring (Clupea harengus pallasi), were repeated using our method to compare the accuracy and precision of estimates made with both procedures. Mean fecundity estimates did not differ significantly between methods. The precision of estimates made using the counter was at least sixfold greater, and single determinations were accurate to within 5% of the true mean value with 95% probability. Our procedure is also less tedious and about 70% faster than the gravimetric method. The counter, unmodified, should be capable of counting eggs from 25 marine and 6 freshwater fish species. We believe that it can be easily adapted to count eggs that differ substantially in size from those of Pacific herring.
Evidence of Contaminant Loading to Lake Ontario from the Niagara River
Authors: El-Shaarawi A. H. , Esterby S. R. , Warry N. D. , Kuntz K. W.
Published: April 2011

The hypothesis that the concentrations of pollutants are the same throughout the length of the Niagara River, against the alternative that they are higher in the lower river, was examined using three sets of data: (1) Ontario Ministry of Environment's (MOE) results for organic substances in raw drinking water (1978–84); (2) MOE transect data for metals in water (1981); (3) Environment Canada data on organic substances in large-volume water samples and suspended sediments (1981). The designs of the studies dictated different statistical procedures for each set, with nonparametric procedures based on ranking being used for sets 1 and 3, and normal theory methods for set 2. Further, both univariate and multivariate procedures were used for set 3. Despite the considerable number of nondetections in these data, it was still possible to make quantitative comparative statements, with the degree of uncertainty providing the quantitative component. In each study, a number of substances were shown to be higher in the lower river than in the upper river, and by examining all substances of set 3 simultaneously, locations in the lower river were shown to be similar to each other as were locations in the upper river.
Bioenergetics of O+ Atlantic Herring (Clupea harengus harengus)
Authors: Kerr S. R. , Dickie L. M.
Published: April 2011

On the basis of the limited published information on herring bioenergetics, together with general considerations from other species, we propose a preliminary bioenergetic model for Atlantic herring (Clupea harengus harengus). Application of the model to published data for five larval cohorts from each of two years shows that temperature and body size interact with the apparent availability of suitable prey to result in quite different metabolic environments that support relatively uniform growth.
Statistical Properties of Alternative Parameterizations of the von Bertalanffy Growth Curve
Authors: Ratkowsky D. A.
Published: April 2011

The von Bertalanffy growth curve is often used in fisheries research to describe the relationship between the weight or length of a fish and its age. The equation is also encountered in various other branches of science and applied science in a variety of different parameterizations and names; for example, it is also known as the asymptotic regression equation or the three-parameter exponential equation. Since these equations are all nonlinear regression models, the properties of the least squares estimators of the parameters of these models may be very different from their large-sample properties, where the estimators are unbiased, have the minimum attainable variance, and are normally distributed, the conditions that pertain in a linear model. Different parameterizations will have estimators which approximate the asymptotic properties to varying degrees of closeness. My study of eight parameterizations shows that one of them, a generalization which allows unequal age increments of a parameterization proposed by Schnute and Fournier, is far superior to any of the other models, which include the most commonly used parameterization, in that it exhibits close-to-linear behavior. Two of the three parameters in this model represent the expected mean lengths corresponding to the youngest and oldest ages, respectively, in the sample, and thus have a ready biological interpretation. I discuss why it is important to have a close-to-linear model when one wishes to make comparisons between two or more data sets. Methodology is briefly described for carrying out such comparisons, and some further remarks are made about why biologists should be concerned about the statistical properties of the models that they use. Although most data sets I used for illustration are obtained from marine animals, the conclusions are general and apply to all disciplines which make use of the von Bertalanffy model in whichever guise or form it appears.
Effect of Body Form and Response Threshold on the Vulnerability of Four Species of Teleost Prey Attacked by Largemouth Bass (Micropterus salmoides)
Authors: Webb P. W.
Published: April 2011

Experiments were performed using four prey species (fathead minnow, Pimephales promelas, largemouth bass, Micropterus salmoides, bluegill, Lepomis macrochirus, and tiger musky, Esox sp.) with various body and fin forms attacked by largemouth bass predators to determine how body and fin morphology, performance, and response thresholds influenced prey vulnerability. Prey differed in three factors that could affect the outcome of predator–prey interactions: body depth, the presence of spiny rays, and locomotor performance capability. Captures were only successful for strikes near the center of mass. The presence of spines was not shown to substantially affect predator strike targets on prey, but large body depth misdirected strikes from the center of mass area and increased the probability of prey escaping. Prey escape speeds were variable and not maximum. Acceleration rates in the startle response varied among the prey species. Tiger musky had the highest acceleration rates (11.7–12.2 m∙s−2). Acceleration rates decreased for the other prey in the order bluegill, largemouth bass, and fathead minnow. Predators attacking prey with higher acceleration performance were more likely to abort attacks and less likely to chase prey. Prey response thresholds were defined as the rate of change of the angle subtended by the predator as viewed by the prey at the start of the prey's motor response. This looming threshold varied among the species tested, and predators were more likely to abort attacks on prey with low thresholds. Low prey response thresholds correlated with high acceleration rates. The basis for multiple, rather than complementing, adaptations facilitating prey escape is not known, but may be related to risks and benefits during foraging by fish with different diets.
Egg Loss from the American Lobster, Homarus americanus, in Relation to Nemertean, Pseudocarcinonemertes homari, Infestation
Authors: Campbell Alan , Brattey John
Published: April 2011

The relationship between nemertean (Pseudocarcinonemertes homari) infestaton and egg loss from ovigerous American lobsters, Homarus americanus, trapped near Grand Manan, New Brunswick, was investigated during 1980–83. The proportion of lobster eggs lost each month was variable, but generally increased to a maximum of 0.38–0.43 at the end of each of the three egg incubation periods. Up to 6.3% of the newly ovigerous lobsters tagged (N = 1413) during July–October 1982 has lost all their eggs by April–July 1983. Most ovigerous lobsters (74%) were infested with P. homari, but many lobsters had low mean densities of nemerteans (< 2/1000 lobster eggs). There was a significant but low correlation between P. homari densities and the proportion of eggs lost; however, egg losses could not be attributed solely to P. homari. Egg loss did not differ significantly between uninfested and nemertean-infested lobsters during each of the three egg incubation periods. The few lobsters that acquired high densities (> 4) of P. homari during the early stages of egg incubation appeared to suffer extensive or complete egg mass destruction. However, most lobsters maintained low densities (< 2) of nemerteans and hatched most (> 60%) of their eggs.
Predation on Larval Lake Whitefish (Coregonus clupeaformis) and Lake Herring (C.artedii) by Adult Rainbow Smelt (Osmerus mordax)
Authors: Loftus D. H. , Hulsman P. F.
Published: April 2011

Rainbow smelt (Osmerus mordax) predation on larval lake whitefish (Coregonus clupeaformis) and lake herring (C. artedii) in Twelve Mile Lake, Ontario, was intense in 1984. Coregonid larvae hatched in early April as smelt spawning was ending. Predation was continuous for a 7-wk period, beginning at the onset of hatching. Numbers of coregonid larvae observed in smelt stomachs were directly proportional (p ≤ 0.005) to their abundance in the lake. During the week when the larvae were most abundant, they occurred in 93% of the smelt stomachs containing food. The corresponding average daily consumption was 8.4 larvae per smelt. Simulation of the combined effects of smelt predation and "natural" mortality indicated that mortality of lake whitefish may be 100%. Survival of herring larvae must be greatly reduced as well. Rainbow smelt became established in Twelve Mile Lake in the 1950's; their effect on larval whitefish survival may have been aggravated by intensified dipnetting of spawning lake whitefish during the 1960's. There has been little or no recruitment of young whitefish to the population since 1975, although dipnetting for adults ceased in about 1970. Our results support the hypothesis that the primary cause of recruitment failure of this whitefish population is predation by smelt.
Interaction of Low pH and starvation on Body Weight and Composition of Young-of-Year Smallmouth Bass (Micropterus dolomieui)
Authors: Cunningham G. L. , Shuter B. J.
Published: April 2011

Effects of overwinter starvation on the body composition of young-of-year smallmouth bass (Micropterus dolomieui) were examined in laboratory and field studies. Interactive effects of starvation and low pH on body composition were examined in the laboratory. Changes in body composition associated with starvation were similar in laboratory and field studies: on a dry weight basis, the amount of water, ash, Ca, K, and Na increased progressively in both laboratory and wild fish. The amount of Cl per unit dry weight showed a moderate increase in the laboratory fish and a large decline in the wild fish. The effects on starving fish of 6-wk chronic exposures to nonlethal pH levels of 4.0–7.0 were examined in the laboratory. No pH effect was noted for levels greater than 5.0. Losses of water, ash, Ca, K, Cl, and Na increased as the pH declined. There was no consistent effect of pH on rate of loss of ash-free organic matter. The results suggest that starvation may reduce the tolerance of young smallmouth bass to low pH through progressive weakening of the osmoregulatory system.
Transport of 60Co between Water and Sediments in a Small Shield Lake
Authors: Cornett R. Jack , Ophel Ivan L.
Published: April 2011

Low levels of 60Co, discharged from a waste management area, have flowed into a small shield lake over a period of 22 yr. Constructing a mass balance using measured waterflows, measurements of 60Co activities in the inflow, in the bottom sediments, and in the lake outlet provides a unique record of the isotope's behaviour. The long-term, annual, and seasonal movements of 60Co between the water, sediments, and the outflow have been examined and compared. An instantaneously mixed, single reservoir model with constant parameters accurately simulated the average annual variations in 60Co activity in the water and in the sediments. The lake sediments were the major sink for 60Co. More than 90% of the 60Co present in the lake system at any one time was found in the sediments. However, less than half of the total 60Co inputs were retained in the sediments over the 22-yr period. The remainder left the lake through the outflow. The fractional rate of 60Co deposition in the sediments was independent of the rate of 60Co inputs and independent of the 60Co activity in the lake sediments. Seasonal changes in 60Co concentrations in the lake water were very large. Spring and summer concentrations were often 50–500% lower than predicted from a model that simulated annual average concentrations. The bias was likely due to rapid removal of 60Co by increased scavenging of the isotope by particulates. During the winter, 60Co concentrations in the lake water were greater than expected, probably due to the exclusion of 60Co from lake ice, incomplete mixing of the inflow with the lake water, or release of 60Co from the sediments. These seasonal variations in the 60Co activity were accurately simulated by a single reservoir model using different removal rates for the summer and winter periods.
Source of Error in Water Velocity Measurement for Aquatic Studies
Authors: Morantz D. L. , Barbour S. E. , Sweeney R. K.
Published: April 2011

Water velocity is an important component in aquatic studies but is subject to alteration by the presence of an underwater observer. Tests using two types of water velocity meter and a snorkeler showed the effects to be a function of the diver's distance from the probe. Lateral positions generally caused an acceleration of flow at the measurement point of up to 150%, while downstream positions resulted in a decrease in flow of up to 65%. It is recommended that where underwater observers are employed, they position instruments that can be read remotely and then move well away from the point of measurement.
Large-Scale Risk Assessment of Acid Rain Impacts on Fisheries: Models and Lessons
Authors: Minns C. K. , Kelso J. R. M. , Johnson M. G.
Published: April 2011

Lakes, streams, and their watersheds in large parts of the world have little ability to neutralize acidity associated with precipitation. Resource management agencies are concerned with the extent of these impacts including the loss/hazard to key fish species, and the likely status of these aquatic systems given alternate emission control scenarios. Two models designed to provide such a large-scale risk assessment are presented herein. The strengths and weaknesses are identified. Since models draw together the best of our theories, experimental, and survey data, these are compared with existing knowledge, theories, and data.
Genetic Population Structure of Atlantic Halibut,Hippoglossus hippoglossus
Authors: Fevolden Svein Erik , Haug Tore
Published: April 2011

Atlantic halibut, Hippoglossus hippoglossus, have been shown to home to the same spawning site in successive years, suggesting that distinct breeding populations could exist. The species' population structure has, therefore, been studied using biochemical genetic methods to reveal possible genetic differences among fish from different spawning sites. Genetic screening of 43 loci in Faroese halibut revealed only four polymorphic loci, including one highly polymorphic fumarase locus not previously detected in halibut. Comparing these four loci among stocks from the Faroes, the Norwegian coast and Greenland gave evidence of general genetic homogeneity over the sampling range. This lack of genetic differentiation is not taken as proof, but as strong evidence of substantial gene flow between geographical areas.
Impacted Stress: A Causal Agent of Reduced Whitefish (Coregonus Iavaretus) Egg Incubation Time
Authors: Næsje Tor F. , Jonsson Bror
Published: April 2011

The purpose of these experiments was to investigate whether whitefish (Coregonus Iavaretus) eggs subjected to induced agitation had a shorter incubation period to hatching than undisturbed incubating eggs. Eyed eggs were divided into four main groups: two incubated at river temperatures and two incubated in heated water. River temperature was 2 °C at the beginning of the experiment and increased to more than 10 °C at hatching. Heated water temperatures varied between 6.5 and 8.5 °C. One sample with four replicates at each incubating water temperature was continuously agitated with flowing water, while two samples with four replicates each were incubated undisturbed. At both temperatures, eggs kept in motion by flowing water hatched at fewer degree-days (heated water: 380 ± 6.4, natural water: 417 ± 6.6) from fertilization to 50% hatching than those laying undisturbed (heated water: 513 ± 10.5, natural water: 470 ± 7.3). Eggs agitated during incubation hatched with greater synchrony than those incubated undisturbed. Larvae incubated at river temperatures were larger than those incubated in heated water. Our findings revealed that eggs can hatch at different incubation stages during the ontogeny when exposed to varying environmental stimuli.
Promotion of Rapid Growth of Rainbow Trout (Salmo gairdneri) by a Recombinant Fish Growth Hormone
Authors: Agellon L. B. , Emery C. J. , Jones J. M. , Davies S. L. , Dingle A. D. , Chen T. T.
Published: April 2011

The rainbow trout (Salmo gairdneri) growth hormone (GH) cDNA clone isolated previously programs the synthesis in Escherichia coli of a chimeric GH polypeptide that differs from the mature form of the natural hormone by an additional 11 amino acid residues at the NH2-terminus. Treatment of yearling rainbow trout with an enriched preparation of this recombinant GH resulted in enhancement of growth. Specific growth rates, weight increase, and length increase of GH-treated fish were markedly higher than those of the mock-treated or untreated fish. In addition, the chemical composition and ultrastructure of muscle tissue of GH-treated fish were not significantly different from that of control fish. These results suggest that the recombinant GH possesses growth-promoting activity and that GH-treatment results in not only accelerated but also normal growth of fish.
Effects of Liming on the Distribution of Cadmium in Water, Sediment, and Organisms in a Swedish Lake
Authors: Andersson Paul , Borg Hans
Published: April 2011

We studied the cadmium concentrations in water, sediment, suspended particles, a free-swimming insect larva (Chaoborus), a sediment-bound insect larva (Chironomus), and liver of northern pike (Esox lucius) before and after liming operations in Lake Långsjön, Sweden. In accordance with the higher pH levels obtained in the lake water after the limings, cadmium concentration decreased in the water but increased in the sediment. Cadmium concentration in fish liver and Chironomus decreased after the limings whereas the concentration in Chaoborus larvae increased after the first liming. Possible mechanisms are discussed.
Predation by Jellyfish on Larval Fish: An Experimental Evaluation Employing in situ Enclosures
Authors: Lafontaine Yves de , Leggett W. C.
Published: April 2011

Large in situ enclosures were used to investigate the mortality of yolk-sac larval capelin (Mallotus villosus) by four species of jellyfish predators. Daily instantaneous larval mortality increased linearly with predator density but was independent of initial larval density, indicating a linear functional response of the four jellyfish species. The addition of alternative prey did not modify the linearity of the functional response and did not significantly reduce or increase larval mortality imposed by two jellyfish species. The evidence of a linear response in large enclosures contrasts with the curvilinear (Type II) response previously reported in studies conducted in small laboratory containers. Larval mortality was strongly dependent on predator size within jellyfish species and increased with initial larval size. Larval capelin appeared more susceptible to predation at the time of transition from endogenous to exogenous feeding. Daily larval mortality rates due to predation varied between 0.015 and 1.58 depending on jellyfish species and appeared more strongly determined by body mass than differences in feeding appendages of jellyfish. Our results indicate that reduced larval mortality to jellyfish predation is achievable only by timing larval release in water mass where jellyfish numbers are naturally reduced. We estimated that macro invertebrate predation has the potential of being the primary regulator of larval survival and we hypothesized that large intra- and interannual variation in larval survival may be due to the variability in the emergence timing of capelin larvae relative to the growth trajectory of jellyfish.
Atmosphere–Ocean Coupling in the Northern Gulf of St. Lawrence: Frequency-Dependent Wind-Forced Variations in Nearshore Sea Temperatures and Currents
Authors: Rose G. A. , Leggett W. C.
Published: April 2011

We found nearshore sea temperatures and currents on the north shore of the Gulf of St. Lawrence to be linked to wind-forced upwellings and downwellings. Multiple coherence of alongshore and cross-shore wind stresses with sea temperature (f > 1/d removed) was significant at periods > 3 d (maximum K2 = 0.90) and at 1.8 d. Partial coherences were frequency dependent. At periods > 3 d, which contained most of the variance alongshore forces dominated. Cross-shore winds were significant only at 1.8 d. A time domain model using lagged wind stress and cumulative air temperature as predictors explained 95% of the variance in post-stratification nearshore temperature. Temperature changes were virtually synchronous along 150 km of coastline. Alongshore currents were coherent with alongshore winds at periods > 2 d. Cross-shore currents were coherent with cross-shore winds at periods of 1–2 d. These results are compared with Csanady's models of wind-forced coastal thermocline oscillation. We conclude that alongshore winds force major upwellings and downwellings in this region. Cross-shore forces are important at f > 0.5/d. These dynamics regulate local primary biological processes and the transport of energy through their influence on fish migration.
An Empirical Evaluation of the Duration-in-Beam Technique for Hydroacoustic Estimation
Authors: Thorne Richard E.
Published: April 2011

The duration-in-beam is an empirical technique for estimation of the effective sampling angle of a hydroacoustic beam. The technique potentially allows estimation of fish densities without the usual requirements for system calibration and target strength information. Duration-in-beam measurements from 50 hydroacoustic surveys of juvenile sockeye salmon (Oncorhynchus nerka) in Alaska were used to examine the variability in the technique. The results showed reasonable consistency in the beam angle measurement and indicated that the technique was not subject to the estimation errors usually associated with uncertainty in the acoustic system calibration and target strength parameters.
Fish Survival and Recruitment: Investigations Based on a Size-Structured Model
Authors: Schnute Jon T. , Richards Laura J. , Cass Alan J.
Published: April 2011

In this paper and its companion (Schnute et al. 1989, Can. J. Fish. Aquat. Sci. 46: 730–742), we present a statistical analysis of Schnute's size-structured model for exploited fish populations. Here we emphasize model parameters associated with survival and recruitment. We present a simple method of graphical analysis for assessing these parameters, and we develop a related statistical model, based on the modern theory of time series analysis. Our model incorporates a range of possible error structures that include both natural variability (process error) and data uncertainty (measurement error). We illustrate the model's application with data from an exploited lingcod (Ophiodon elongatus) stock. Preliminary graphical estimates of parameters agree remarkably well with final estimates from the statistical model. Where possible, we investigate alternative viewpoints associated with (1) choices of error structure, (2) dynamic and equilibrium versions of the model, (3) uncertain growth parameters, (4) different abundance indices, (5) mark–recapture experiments, and (6) availability of size-frequency data.
A Conditional Generalized Least Squares Method for Estimating the Size of a Closed Population
Authors: Crittenden R. N. , Thomas G. L
Published: April 2011

In the corrected Leslie–DeLury catch-per-unit-effort method, estimation of the corrected cumulative catches causes the underlying model to be an errors-in-covariates structural model with a nondiagonal dispersion matrix. This violates the assumptions of regression and causes the corrected Leslie–DeLury method to give biased estimates of the population size and its variance. We use generalized least squares and a controlled variables design to resolve these difficulties, obtain the minimum-variance unbiased linear estimator, and compute unbiased variance estimates. We apply our method to sockeye salmon fingerlings (Oncorhynchus nerka) netted in a hatchery pond. For these data, arranged according to the controlled variables design, the corrected Leslie–DeLury method underestimates the standard error of the population size by 41%.
Distinction between American Eels (Anguilla rostrata) of Different Geographic Origins on the Basis of Their Organochlorine Contaminant Levels
Authors: Castonguay Martin , Dutil Jean-Denis , Desjardins Claude
Published: April 2011

This study presents evidence that organochlorine contaminant levels of fish tissues represent a valuable tool for stock discrimination. Variability of concentrations of 15 organochlorine contaminants allowed a discrimination among American eels (Anguilla rostrata) of unknown (captured during the migration down the St. Lawrence River) or known geographic origins. The study also exemplifies that information regarding environmental distribution of contaminants can be gained by comparing organic contaminant levels among groups of fish. Indeed we can infer from this study that mirex contaminated sediments have extensively (at least 400 km) drifted downstream from Lake Ontario in less than 19 yr.
Survival of Atlantic Halibut (Hippoglossus hippoglossus) Caught by Longline and Otter Trawl Gear
Authors: Neilson John D. , Waiwood Kenneth G. , Smith Stephen J.
Published: April 2011

To assess the effectiveness of a proposed minimum size limit (81 cm) for Atlantic halibut (Hippoglossus hippoglossus) in Canadian waters, the survival of small fish caught in longline and bottom trawl gear was examined using live holding facilities onboard a research vessel and subsequently, in a land-based laboratory. Commercial practices were simulated during fishing operations. Of halibut less than the proposed size limit, 35% of the otter trawl catch and 77% of the longline catch survived more than 48 h. Factors potentially influencing halibut survival (handling time, total catch, fish length, maximum depth fished, and trawl duration) were examined using proportional hazard models. On the basis of those analyses, it was concluded that in bottom trawl sets of duration used in the commercial fishery (≥ 2 h), higher survival times were associated with shorter handling time, larger fish size, and comparatively small total catch weight. Supplemental information on the condition of trawl-caught halibut was also obtained from observers stationed onboard commercial trawlers.
Bacteria–Organic Matter Relationship in Sediments: A Case of Spurious Correlation
Authors: Bird D. F. , Duarte C. M.
Published: April 2011

A longstanding claim regarding the existence of a strong positive relationship between bacterial abundance and organic matter in aquatic sediments is shown to be potentially spurious. The statistical significance of the relationship results primarily from standardization of both variables to dry weight of sediments. We suggest that other published relationships may be similarly artifactual. Deceptive results are possible unless standardization is done with caution.
Population Collapse of the Crayfish Orconectesvirilisin Response to Experimental Whole-Lake Acidification
Authors: Davies I. J.
Published: April 2011

A population of Orconectes virilis in Lake 223 at the Experimental Lakes Area, northwestern Ontario, was monitored from 1976 to 1982 during an acidification experiment. O. virilis from nearby Lake 240 served as a reference population. Crayfish abundance remained stable as average epilimnion pH was gradually lowered from 6.49 (1976) to 5.93 (1978). In 1979 (pH 5.64) recruitment of young was poor and the overall population size [Formula: see text] fell from 105 800 to 60 300 animals. The decline continued in the complete absence of recruitment during 1980 (pH 5.59, [Formula: see text] and 1981 (pH 5.02, [Formula: see text]. Few crayfish survived until the spring of 1982. None were present from mid-summer 1982 to fall 1983 (average pH 5.09 to 5.13). Hatchling mortality and some egg loss appeared to have been the causes of recruitment failure. Acidification also produced a noticeable softening in the carapace of all intermoult crayfish. Growth, mortality, behaviour, and the basic reproductive functions of juvenile and adult crayfish did not change in response to acidification. Fish predation and the incidence of a microsporidian parasite apparently contributed little to the population decline.
Temporal and Spatial Patterns of Porewater Phosphorus in Shallow Sediments, and its Potential Transport into Narrow Lake, Alberta
Authors: Shaw J. F. H. , Prepas E. E.
Published: April 2011

During 1985 and 1986, summer and spatial patterns of porewater soluble reactive phosphorus (SRP) from sediments ≤ 15-m depth were examined at Narrow Lake, a deep, mesoeutrophic Albertan lake. At three sites (different in depth and macrophyte colonization), trends in porewater SRP concentrations ([SRP]) in the top 5 cm of the sediment from May to August varied, possibly due to root uptake of SRP by macrophytes. At a depth of 5 m, mean (in the top 5 cm of the sediment) and variance of porewater [SRP] at one site (<0.15 m2) were the same as over the entire lake. Excluding data from macrophyte sites, porewater [SRP] were positively related to depth of the water column (P < 0.0001). Molecular diffusion of SRP from sediments with and without macrophytes located in the trophogenic zone was calculated. During summer, molecular diffusion from shallow sediments to the trophogenic zone was 0.05 mg∙m−2 d−1, or 29% of atmospheric deposition of phosphorus (P) (the major external source of P to the lake). A sampling strategy is discussed to enable the calculation of whole-lake P transport from shallow sediments to the trophogenic zone in lakes with similar morphometry and trophic status to Narrow Lake.
Quantitative and Qualitative Characteristics of Somatic and Gonadal Growth of Yellow Perch (Perca flavescens) from Lac Ste. Anne, Alberta
Authors: Tanasschuk R. W. , Mackay W. C.
Published: April 2011

A yellow perch (Perca flavescens) population from a shallow eutrophic north temperate lake was sampled 10 times between March 1976 and June 1977 to determine the characteristics of somatic and gonadal growth. Quantitatively, somatic growth differed in timing and extent among age-sex groups. One + males and females grew mostly in June whereas 2 + males grew mainly in July; 2 + females grew from June through September. Two + males grew less over the year than did the other age-sex groups. The qualitative characteristics of somatic growth were not influenced by sex or maturation. The timing of gonadal growth and the associated endogenous energy utilization differed between the sexes. One + females did not mature. Testes grew in late summer (August). There was no impact of gonad development on somatic composition of 1 + males whereas 2 + males appeared to use visceral fat. Gonadal growth for 2 + females began in August and continued through March and presumably to spawning in April; somatic lipid was depleted during ovarian growth.
Prey Detection in Cyprinids during Early Development
Authors: Wanzenböck Josef , Schiemer Fritz
Published: April 2011

Larval and juvenile fish of roach (Rutilus rutilus L), bleak (Alburnus alburnus L), and blue bream (Abramis ballerus L.) were investigated weekly to define the ontogenetic development of prey detection capacities. Visual acuity was determined by measuring reactive distances for zooplankton prey for fish from 8 to 50 mm standard length using video recordings. Data of reactive distances, swimming speeds, and the characteristics of the visual field were combined to calculate prey location volumes. Prey location capacity increased exponentially with fish size which implies enormous differences in prey encounter rates among size classes of cyprinids. Distinct differences of prey location capacities occurred between species in the juvenile, planktivorous stages of the three cyprinids coinciding with the trophic differentiation of the adults.
Changes in Prey Rank and Preference by Young Planktivores for Short-Term and Long-Term Ingestion Periods
Authors: Confer John L. , O'Bryan Linda M.
Published: April 2011

Feeding by young planktivorous fishes (yellow perch, Perca flavescens, rainbow trout, Oncorhynchus mykiss, and lake trout, Salvelinus namaycush) was examined. Prey rank was determined by offering a swarm of one prey type and observing ingestion rates. During the initial feeding burst, larger prey generally ranked higher. During long-term feeding the largest prey, large Daphnia magna, generally declined in rank while the smallest prey, Diaptomus sicilis, increased to the highest or second highest rank. Prey preference was measured with fishes feeding in a swarm of mixed prey. Initially small rainbow trout and yellow perch selected for large Daphnia then switched to Diaptomus. For small rainbow trout this switch in prey preference paralleled the change in prey rank. For yellow perch, large Daphnia and Diaptomus provided essentially the same long-term ingestion rates. The nearly exclusive selection for Diaptomus during long-term feeding did not agree with prey rank based on caloric ingestion rates. Previous work has shown that yellow perch have a high growth efficiency on a diet of Diaptomus. Selection for Diaptomus suggests that fish can rank prey by nutritional quality as well as caloric ingestion rates.
Ultrastructural Observations on the Ovary and Eggs, and the Development of Egg Adhesion in Pacific Herring (Clupea harengus pallasi)
Authors: Gillis D. J. , McKeown B. A. , Hay D. E.
Published: April 2011

Changes in Pacific herring ovarian tissues and eggs during the four stages, late vitellogenic, ovulating, ovulated, and fertilized, were investigated by transmission and scanning electron microscopy. During the late vitellogenic and transitional stages the egg membranes consisted of five layers: the externus, distal inter-layer, internus, proximal inter-layer, and the sub-internus. The proximal and distal inter-layers do not appear to have been described elsewhere. A class of small, non-vitellogenic oocytes which were observed in late vitellogenic and ovulating ovaries, but not in ovulated ones or spawned eggs, are tentatively described as 'pre-ovulatory atretic oocytes'. Transmission electron microscopy (TEM) results demonstrated a collapse of the pores in the internus which may serve as a mechanical means of achieving egg membrane semipermeability during the first, or ovulation hydration. A thin, electron-dense layer was deposited on the external surface of the externus during ovulation. This epi-layer expanded on contact with seawater and became strongly adhesive. The results of the analyses are discussed in relation to an industrial roe-product quality problem called 'fragile roe' — an expression which describes a condition of reduced adhesion of eggs.
Stimulation of Plasma Thyroxine Levels by Novel Water Chemistry during Smoltification in Chinook Salmon (Oncorhynchus tshawytscha)
Authors: Hoffnagle Timothy L. , Fivizzani Albert J.
Published: April 2011

The separate influences of changes in water chemistry and flow rate on plasma thyroxine levels were assessed in a freshwater population of chinook salmon (Oncorhynchus tshawytscha) undergoing smoltification. Fish subjected to a change in water source had plasma thyroxine levels significantly greater than those of controls on several sampling dates. Maximum levels were observed 10 d after water change. Conversely, plasma thyroxine levels in fish for which the flow rate was increased showed little change and were never significantly different from controls. Plasma thyroxine levels were greater in fish held under a natural rather than artificial photoperiod but the patterns of change were similar in the two groups. Control fish transported to a new hatchery and novel water source attained plasma thyroxine levels which were even greater than those of novel water-exposed fish at the original hatchery. The results indicated that altered water chemistry rather than increased flow rate was the stimulus for the elevation in plasma thyroxine levels associated with smoltification in these chinook salmon.
Effect of Dietary Ascorbate on the Concentration of Tissue Ascorbic Acid, Dehydroascorbic Acid, Ascorbic Sulfate, and Activity of Ascorbic Sulfate Sulfohydrolase in Rainbow Trout (Oncorhynchus mykiss)
Authors: Dabrowski Konrad , Lackner Reinhard , Doblander Cristine
Published: April 2011

The concentrations of ascorbic acid in several tissues of rainbow trout (Oncorhynchus mykiss) are significantly influenced by various dietary treatments. Ascorbic acid was taken up readily by erythrocytes, kidney, liver, intestine, spleen, and brain in fish fed an ascorbate supplemented diet (AA group), the concentration being from 1.5 to 14.8-fold higher than in fish fed a diet lacking ascorbate (control group). In fish fed a diet supplemented with an equimolar amount of ascorbic acid in the form of ascorbic sulfate (AS group) the ascorbic acid concentrations in kidney, intestine, and erythrocytes were significantly elevated above those of the control group. Ascorbic sulfate was found in kidney, liver, and intestine of the AS group, but not in other groups. In fish fed a diet devoid of vitamin C the ascorbic acid concentrations in kidney, liver, intestine, and spleen were signficantly lower than in fasting fish over the same period of time (28 d), suggesting a high demand for vitamin C in an actively feeding animal. Salmonid fish are therefore probably unable to utilize ascorbic sulfate sufficiently to prevent the appearance of vitamin C deficiency, and thus resemble scurvy-prone mammals in this respect.
Inorganic Monomeric Aluminum and pH as Predictors of Acidic Water Toxicity to Brook Trout (Salvelinus fontinalis)
Authors: Parkhurst Benjamin R. , Bergman Harold L. , Fernandez Joseph , Gulley David D. , Hockett J. Russell , Sanchez Deborah A.
Published: April 2011

Inorganic monomeric aluminum concentrations were found to be the primary determinant of survival of brook trout feeding fry exposed for 21 d to various combinations of total aluminum and pH, plus several concentrations of fluoride or DOC, or several temperatures. Total aluminum concentrations in the 4 × 4 × 4 experimental matrices ranged from 3–1276 ppb, pH from 4.4–6.7, fluoride from <10–328 ppb, DOC from <1–9.2 ppm, and temperatures from 5.4–12.0 °C. Stepwise logistic regression was used to determine the significance of the effect of each water quality variable on survival. Inorganic monomeric aluminum accounted for 78–98% of the variation in survival. Except in the fluoride bioassay where pH was not significant, pH was the second-most important variable, accounting for up to 16% of the variation in survival. Fluoride or temperature accounted for 1–2% of the variation in survival, while DOC accounted for 6% of the variation in survival.
Distribution of Nitzschia pungens in Coastal Waters of British Columbia
Authors: Forbes J. R. , Denman K. L.
Published: April 2011

Concern about the potential for contamination of Pacific coast molluscan shellfish by domoic acid prompted us to review the distribution of Nitzschia pungens in coastal waters of British Columbia. From 1980 to 1988, N. pungens occurred throughout waters of the continental shelf, most frequently as a minor component of the large diatom aggregations observed off southwest Vancouver Island during July and August. The species was less common in the Strait of Georgia and north of Vancouver Island, but interannual variability in distribution and abundance was considerable. Maximum concentrations recorded were 106 cells∙L−1 in Hecate Strait in July 1983 and 5 × 105 cells∙L−1 off southwest Vancouver Island in August 1986. Discrimination of presence or absence on the basis of existing environmental variables produced mixed results, but has potential. Scanning electron microscopy showed that both N. pungens f. pungens and N. pungens f. multiseries (the latter being implicated in the contamination of shellfish in Atlantic Canada) occur in British Columbia. It remains to be shown whether N. pungens produces domoic acid in Pacific coast waters and whether the high abundances observed over the continental shelf also occur near shore.
Local-Scale versus Large-Scale Factors Affecting Recruitment
Authors: Cohen Edward B. , Mountain David G. , O'Boyle Robert
Published: April 2011

Recent analyses of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) stocks in the northwest Atlantic have indicated that large-scale factors (several hundred to thousands of kilometres) dominate over effects operating on more local scales (10 to a few hundred kilometres} in determining recruitment patterns for these stocks. Adding additional years and additional stocks to the data set, the recruitment time series for cod and haddock have been reexamined. A first differencing technique was used to remove trends in the data. The results indicate that while large-scale effects probably do affect recruitment, the dominant factors are operating on more local scales and correlations are strongest for neighboring stocks.