bluuebunny/crossref_metadata_2025 huggingface dataset:
Biological and Toxicologtcal Effects of Environmental Contaminants in Fish and Their Eggs
Authors: Niimi A. J.
Published: April 2011

Rainbow trout (Salmo gairdneri), white sucker (Catostomus commersoni), white bass (Morone chrysops), smallmouth bass (Micropterus dolomieui), and yellow perch (Perca flavescens) were collected from Lakes Ontario and Erie to examine the relationship between contaminant levels in females and their eggs. Factors such as the percent lipid in the fish and percent of total lipid deposited in the eggs significantly influenced (P < 0.01) contaminant transfer. The percentages of the 9–11 organic contaminants transferred generally showed less variation within a species than the percentages for a substance transferred among the five species examined. This relationship was consistent even though there was over a 10-fold range in contaminant concentrations within a given species. Mercury did not demonstrate this response because the percentage in eggs was low for all species. The levels of PCB monitored in eggs of rainbow trout collected from Lake Ontario suggest that egg and fry survival rates could be affected based on the toxicological evidence from other studies. An examination of the possible effects of spawning on the kinetics of contaminants among these species suggests that relative body concentrations of organic contaminants may be decreased by 5% or be increased by 10%, and mercury levels may be increased by 6–22% following the deposition of eggs. The amount of change varies with species and is influenced by the percent egg weight of body weight, and the rate of contaminant transfer from females to eggs.Key words: toxicology, contaminants, reproduction, Lake Ontario, Lake Erie
Adaptive Flexibility in the Foraging Behavior of Fishes
Authors: Dill Lawrence M.
Published: April 2011

Flexibility is an important adaptive feature of the foraging behavior of fishes, because most natural environments vary both spatially and temporally. Fish should respond to low levels of food availability by altering their behavior in ways which ensure higher feeding rates, larger feeding territories, and broader diets. It is shown that the gastric sensation of hunger and its rate of change may act as appropriate cues to food availability, and observed hunger-motivated changes in feeding behavior can produce all of these predicted effects. Data are presented to show that juvenile coho salmon (Oncorhynchus kisutch) alter their behavior in an adaptive manner when faced with variable degrees of threat of competition from territorial intruders, and of risk of predation. A review of similar studies on other species supports the generality of these results. Learning is an important mechanism providing behavioral flexibility, and changes in fish feeding behavior with experience are summarized. A graphical model is developed to show that these changes can result in training biases and food specialization. Learning also results in increased feeding rates. The consequences of these observations for the development of refined models of foraging are discussed.
A Test of Lead-210 Dating for the Measurement of Whole Lake Soft Sediment Accumulation
Authors: Evans R. Douglas , Rigler Frank H.
Published: April 2011

We have tested the hypothesis that variation in accumulation of soft sediments over a lake bottom is related to the lake morphometry, allowing an accurate measurement of whole lake sediment accumulation. In each of two Laurentian Shield lakes in southern Ontario, sediment accumulation was measured at ~20 locations. In both there was a statistically significant linear relationship between soft sediment accumulation and the water depth at the sample locations. The relationship explained 72 and 57% of sediment accumulation variation in Costello and Red Chalk lakes, respectively. Using these relationships, it was possible to calculate the whole lake sediment accumulation rate for each lake. The results indicate that, in general, there is a linear variation in sediment accumulation as a function of depth in small Shield lakes. This study points out the need for a closer examination of sediment movement and accumulation in the shallow regions of lakes.
Analysis of Multiple Objectives in Oregon Coho Salmon Policy
Authors: Walker K. D. , Rettig R. B. , Hilborn R.
Published: April 2011

Our objective was to determine whether formal decision analysis could assist fishery managers in Oregon to evaluate alternative strategies with respect to allocation and production of wild and hatchery coho salmon. The method chosen given multiple objectives and uncertainty is multiattribute utility analysis. The analytical model consists of two main components: (1) a computer model that simulates the life cycle of hatchery and stream spawning coho salmon given environmental variation, different hatchery juvenile release levels, and harvest rates and (2) an objective function that evaluates the aggregate levels of catch and escapement resulting from alternative release levels and harvest rates. The approach was used to rank the expected outcomes from 12 proposed policies. We concluded that (1) the most effective policy is achieved with a relatively low harvest rate and high smolt release level, (2) selection of a particular harvest rate is the most important decision variable, and (3) a large smolt release level can be maintained unless such releases adversely decrease the ocean survival of stream spawning coho. If the agency is to be significantly helped, the analysis must be expanded to involve a larger number of decision makers, incorporate additional objectives such as catch variability, and include a finer level of detail in the simulation model.
Community Gradients in the Scotian Shelf Zooplankton
Authors: Tremblay M. John , Roff John C.
Published: April 2011

The structure of the zooplankton community of the Scotian Shelf was investigated during eight cruises between August 1978 and September 1980. An inshore–offshore community gradient correlated with temperature, salinity, and distance to shore was the strongest pattern revealed by reciprocal averaging. Zooplankton taxa were grouped as inshore (characterized by Arctic species), intermediate (the dominant shelf species), or offshore (expatriate species) on the basis of reciprocal averaging results and correlations with environmental variables. Recurrent group analysis revealed a pattern consistent with that of reciprocal averaging. A shelf recurrent group was always present, dominated by the "core" species: Calanus finmarchicus, Metridia lucens, Pseudocalanus minutus, Oithona similis, and Limacina retroversa; related shelf edge/slope groups were also present. Substantial differences between cruises were apparent in both reciprocal averaging and recurrent group analysis results and appeared to be related to aperiodic changes in hydrographic conditions. Aperiodic incursions of slope water may represent an energy supplement (as nutrients or zooplankton prey species) or an energy loss if expatriate species exploit the shelf community.
A Modified Freeze-Core Technique to Quantify the Depth Distribution of Fauna in Stony Streambeds
Authors: Pugsley C. W. , Hynes H. B. N.
Published: April 2011

A freeze-coring device using liquid nitrogen is described, which enables one person to take a columnar core, extending from the surface to at least 50 cm below a stony streambed. An experiment to validate the technique showed that animals did not flee from the advance of the freezing-front. Using frozen streambed cores, the vertical distribution of benthic invertebrates of two streams in southern Ontario was investigated. In contrast to previous estimates,~70% of the fauna was found in the top 10 cm of the streambed, and invertebrate densities were often lower by an order of magnitude. These differences are attributed to problems of quantifying previous sampling methods.
Density of Fish and Salamanders in Relation to Riparian Canopy and Physical Habitat in Streams of the Northwestern United States
Authors: Hawkins Charles P. , Murphy Michael L. , Anderson N. H. , Wilzbach Margaret A.
Published: April 2011

Relationships between density of fish and salamanders, riparian canopy, and physical habitat were investigated by studying 10 pairs of streams. Among vertebrate taxa, salmonids and sculpins were more abundant in streams without riparian shading than in shaded streams. Abundance of salamanders was not affected by canopy type. Densities of both salamanders and sculpins were correlated with substrate composition, whereas salmonid abundance was not or only weakly so. Salamanders were found only at high-gradient sites with coarse substrates, and sculpins were most abundant at lower-gradient sites with finer-sized sediments. An interaction was observed between the influence of canopy and that of physical setting on density of both invertebrate prey and total vertebrates. Among shaded sites, densities decreased as percent fine sediment increased, but a similar relationship did not exist among open sites. Removal of the riparian vegetation surrounding a stream may therefore mask detrimental effects of fine sediment. These data provide one reason why it has been difficult in the past to generalize about the effects of fine sediment on stream biota.
Carrying Capacity of an Enhanced Side-Channel for Rearing Salmonids
Authors: Mundie J. H. , Traber R. E.
Published: April 2011

Two attempts were made to establish the yield of steelhead smolts (sea-run rainbow trout) (Salmo gairdneri) from a seminatural side-channel and compare it to that of the parent river. In the first, 10 000 fry were introduced to the channel which was maintained at a discharge of 0.42 m3/s. The fry, however, were largely displaced by extraneous coho salmon (Oncorhynchus kisutch), appeared unable to withstand the water velocity in winter, and were greatly reduced by infection from Cryptobia. In the second trial discharge was 0.14 m3/s. The fry tolerated this. The yield (i.e. numbers) per unit area of steelhead smolts, of mean weight 14.5 g, was 31 times that of the river; in terms of biomass it was 10 times. Channel discharge was 2.6% of the river discharge. Physical and biological factors determining smolt yield from streams are considered.
Modeling Suspended Sediment Dynamics of the Miramichi Estuary, New Brunswick, Canada
Authors: Winters G. V.
Published: April 2011

Polynomial models were used to estimate the annual transport of suspended sediment in an estuary with a variable salt-wedge. The models are empirical, based on water flux measurements and SPM concentration, and these are shown to be a function of the tidal oscillations and river discharge.The Miramichi River discharge varies from about 50 m3∙s−1 in January to 1700 m3∙s−1 in April. Diurnal inequality in the semidiurnal tides and variation in river discharge produces a continual inequality in the suspended sediment (SPM) transports for individual flood and ebb tides. Consequently, the models rely on integrating observations for each flood and ebb cycle. Empirical data indicate that semidiurnal tidal transport generally varies from 30 to 300 t in either ebb or flood direction. However, an order of magnitude increase can occur when the ebb tide couples with high runoff (i.e. 3300 t during a single ebb cycle in May 1976). A two-layer model gives a small (20%) increase in the residual sediment transport compared to a one-layer model. The 1976 net transport was calculated as −100 000 t (seaward). Sedimentation rates estimated from core samples agree with model estimates.Key words: Modeling, suspended sediment, SPM, transport, Miramichi, estuary
Suspended Particulate Loading on the Macrobenthos in a Highly Turbid Fjord: Knight Inlet, British Columbia
Authors: Farrow George E. , Syvitski James P. M. , Tunnicliffe V.
Published: April 2011

Knight Inlet is a deep, low-energy but well-oxygenated fjord. The effects of turbidity are principally those of seasonally very high vertical flux from the sediment-laden surface layer. Submersible observations of the benthos are related to suspended load and sedimentation rate data. The bayhead delta slope receives a continual rain of glacial silt (30 cm/yr) and has summer sedimentation rates of 4 kg∙m−2∙d−1.The epifauna of the steep fjord walls shows a marked down-inlet increase in abundance, and the number of species increases from 9 to 45. Brachiopods (Laqueus californianus), solitary corals (Caryophyllia/Cyathoceros), and encrusting sponges are remarkably tolerant of high turbidity. The high sedimentation rates affect the epifauna in three ways: (1) subjection to the ubiquitous "gentle rain" of floes and agglomerates; (2) more locally, microturbidity flows set off by biological resuspension of unstable slope sediment; and (3) major slides of rock and/or sediment. Submarine soil-creep limits the slope infauna, by burrows requiring repeated reexcavation.Down-inlet decrease in sedimentation rate is accompanied by a change in feeding type. In the upper inlet, suspension feeders taking particles < 8 μm (e.g. sabellids, brachiopods) probably utilize bacteria associated with the high vertical flux of SPM. In the middle inlet, selective suspension feeders (e.g. crinoids, gorgonians) sort the SPM for larger particles. In the lower inlet, filter feeders (e.g. barnacles, glass sponges) increase, especially where currents are stronger. The soft-bottom detritus feeders also show a change: from epibenthic forms (e.g. pandalid shrimp, spider crabs) in the upper inlet, through burrowing shrimp in the middle inlet, to ophiuroids in the lower inlet. These changes are correlated with the greater amounts of organic carbon preserved in bottom sediments as they are less diluted by glacially derived inorganic material.The modern-day "turbid association" of brachiopods, solitary corals, and sponges recalls typical outer shelf-basinal shale facies of the Palaeozoic. Turbid, low-energy environments were thus colonized early but faunas have since become less diverse.Key words: fjord, benthos, sedimentation, submersible
Relations Between Annual Dredging Activities, Suspended Matter Concentrations, and the Development of the Tidal Regime in the Ems Estuary
Authors: Jonge V. N. de
Published: April 2011

This paper challenges Kühl and Mann's suggestion (1973) that an increase in organic matter in the Ems Estuary between 1950 and 1970 caused a five- to tenfold increase in the turbidity in that period. Their hypothesis is refuted because: (a) during that period the discharge of organic matter via both the River Ems and the River Westerwoldsche A did not change significantly; (b) the increase in particulate organic carbon in the western Dutch Wadden Sea and possibly also in the Ems Estuary resulting from eutrophication of the North Sea by the River Rhine during 1950–70 is unlikely to have been more than twofold; and (c) Secchi-disc data do not support the five- to tenfold increase in turbidity. It is suggested that dredging is probably responsible for the increase in turbidity because the volume of material dredged annually increased fourfold between 1950 and 1970. The mean annual concentration of suspended matter increased by a factor ranging from 1.3 to 2.1 between 1954 and the period 1970 to 1979. The fluctuations in concentrations of suspended matter showed a statistically significant correlation with the distance dredged annually and not with the volume dredged annually. This indicated that the relation depended more on how "extensive" rather than on how "intensive" the dredging was. The fluctuations in concentrations of suspended matter are caused by the intensified erosion and sedimentation cycle that is initiated after the local natural equilibrium between channel morphology and current pattern is disturbed. This explanation is supported by the morphological changes that occurred in part of the study area between 1975 and 1979. Further support for this hypothesis was found in the changes of the tidal regime in the estuary. It is postulated that the complete cessation of dredging would probably be accompanied by the concentrations of suspended solids falling from the 1979 levels to values nearer those obtained in 1954. The biological implications of the processes described are discussed.Key words: dredging, suspended matter, tidal regime, Ems Estuary, turbidity
Use and Relevance of Analytical Intercomparison Exercises in Monitoring the Marine Environment
Authors: Holden V. , Topping G. , Uthe J. F.
Published: April 2011

The results of several intercomparison exercises for heavy metals and organochlorine residues in marine samples are reviewed. We conclude that, with few exceptions, the levels of agreement between the participating analysts are not good enough to allow them all to take part in multilaboratory monitoring programs, particularly with respect to monitoring residues in fish to determine whether they comply with standards set for human consumption or for comparing levels of contamination in different areas. Reproducibility of analysis is generally better at the higher concentrations and may be sufficient to measure a decrease in contamination following the removal of a highly polluting discharge. However, at the lower concentrations existing in cleaner environments many techniques that analysts currently use may be unable to achieve a degree of precision (or accuracy) sufficient to measure long-term trends in contamination. Analyses carried out by individual laboratories for the purpose of measuring trends in contamination levels must include regular intralaboratory checks to ensure a constant level of performance throughout the period of study.
Potential Anthropogenic Influences on Trace Metal Distributions in the North Atlantic
Authors: Yeats P. A. , Bewers J. M.
Published: April 2011

This paper discusses the application of geochemical understanding of an estuarine and marginal sea environment to an assessment of marine contamination by trace metals. The estuaries and Gulf of St. Lawrence are used as an analogue of a section of the nearshore and continental shelf environment in which metal fluxes, in both dissolved and particulate form, can be estimated. Estuarine and nearshore removal of 99% of the particulate matter, >97% of the particulate Fe and Mn, and 25–50% of the Ni, Co, Cu, Zn, and Cd discharges are indicated. The dissolved Mn efflux is augmented slightly within the gulf. A generic coastal zone model is used to examine the magnitude of exchanges between particulate and dissolved metal phases during transport between the freshwater and deep marine environments. This model is also used to compare global river discharges with metal accumulations in nearshore and pelagic sediments. The current influxes of Zn and Cd to the ocean greatly exceed their rates of sedimentation. The imbalance for Zn may merely be due to limited and inaccurate measurements of Zn in continental runoff. The Cd imbalance, however, appears to be real and reflects a major increase in the mobilization of this metal. Finally, oceanic metal distributions are examined for evidence of contamination of the northwest Atlantic by metals of anthropogenic origin.
Uptake and Conversion of Selenium by a Marine Bacterium
Authors: Foda A. , Vandermeulen J. H. , Wrench J. J.
Published: April 2011

Bio-conversion of Se was examined by incubating Pseudomonas marina in seawater containing either selenite (Na2SeIVO3) or selenate (Na2SeVIO4). At the concentrations of selenite and selenate used (10−4–10−7 mol/L), the growth of P. marina was not inhibited. Under these conditions, selenite was taken up by P. marina, but selenate was not found to enter the cells. Pseudomonas marina incorporated selenite from filtered seawater into sub-cellular fractions, primarily protein (30–50%) and amino acids (44–70%). When incubated in marine broth, P. marina incorporated 75selenite primarily into protein (up to 75%), with a lesser amount into the amino acid fraction (approximately 25%). Insignificant amounts were associated with the bacterial lipid fraction. SeIV was found in the protein and amino acid fractions within 10 min of incubation in medium containing selenite. In uptake studies the level of SeIV in the incubating medium decreased markedly, corresponding presumably to SeIV entering the bacterial cells from the medium. However, simultaneous measurements of total Se in the medium (gas–liquid chromatography following photooxidation) revealed an increasing amount of non-SeIV species of Se in the medium throughout the same period. These results were interpreted as due to the bioconversion of selenite by P. marina into water-soluble non-SeIV metabolite(s) and their subsequent release back into the medium. Up to 35% of the total Se found in the medium after 24 h can be accounted for by this conversion of SeIV into another oxidation state. Pseudomonas marina is also capable of reducing SeIV to elemental Se; this pathway becomes increasingly evident at higher concentrations of Na2SeO3.
Eddy-Enhanced Dispersion of Ocean-Dumped Organic Waste at Deep Water Dumpsite - 106
Authors: Wiesenburg Denis A. , Brooks James M.
Published: April 2011

Volatile organic compounds (VOC) discharged into northwestern Atlantic slope waters at a deep ocean dumpsite were dispersed to background levels within 24 h. The main VOC (>85%) of the waste was toluene, with a large mercaptan component. Several trichlorobenzenes were present in trace amounts. Initial dilution from wake dispersion reduced the waste levels by a factor of 1300. Mixing processes and evaporative loss to the atmosphere further reduced surface water concentrations of VOC by a factor of 1000 in 9 h and to background levels within 24 h. The rapid loss of volatiles from the dumpsite waters results from the very volatile nature of the dumped material and physical mixing processes. The presence of the edge of a large, anticyclonic, warm-core Gulf Stream eddy (ring) in the dumpsite area probably increased local mixing processes which resulted in the rapid dispersion of the waste. The presence of the ring water in the dumpsite area could also account for the low background concentrations observed in the dumpsite.
Distribution of Digestive Enzymes in Zooplankton during the Spring Bloom in a Nova Scotia Inlet
Authors: Mayzaud P. , Conover R. J.
Published: April 2011

Nonparametric correlation and principal component analysis were used to examine relations between digestive enzyme activity in zooplankton and qualitative and quantitative measures of particulate organic matter and between enzymes and composition of the zooplankton community. Barnacle nauplii in near-surface (5 m) water during the first part of the bloom caused heterogeneity, which confounded relationships between enzyme activity and potential substrate concentration. Lack of coherence among enzymes in the 5 m zooplankton was also observed. The less variable deepwater community showed intercorrelation among the enzymes measured. At 30 m, enzyme concentrations in Pseudocalanus were correlated with concentration of particles less than 20 μm, which were dominant in the first part of the bloom. Two time-related events significantly affected zooplankton enzyme levels: one was clearly related to the period of dominance of barnacle larvae and the other with an increase in the C:N ratio from around 5 to greater than 7 in midbloom coinciding with a shift in phytoplankton from smaller forms of apparently higher protein content to large colonial diatoms. The results generally support the hypothesis that the amount and chemical composition of food supply can affect zooplankton digestive enzymes, but they also demonstrate the problems of interpretation if community structure is not well defined and spatial and temporal distribution of organisms not carefully circumscribed.
Distributions of Ferrous Iron and Sulfide in an Anoxic Hypolimnion
Authors: Cook Robert B.
Published: April 2011

In the anoxic hypolimnion of Lake 227, Experimental Lakes Area, northwestern Ontario, ΣH2S exhibits a mid-depth maximum, while Fe2+ increases with depth. At the mid-depth ΣH2S maximum and below, saturation with respect to amorphous FeS is reached, and the concentration of ΣH2S is limited by the high Fe2+ concentrations, in accord with the FeS solubility product. Values for pKsp[Formula: see text] for FeS determined from the ΣH2S maximum and below averaged 3.16 in 1979 and agree well with other in situ and laboratory measurements. In the top 10 cm of sediment, pore water ΣH2S and Fe2+ are in equilibrium with amorphous FeS. Analyses of cores confirms the existence of an iron sulfide phase. Fe2+, which is produced in the pore water from the decomposition of organic matter, increases to concentrations at which siderite may form, although the presence of siderite has not been verified. Comparison of calculated pore water fluxes of Fe2+ with the observed increase of Fe2+ in the anoxic hypolimnion reveals that about 90% of the observed flux originates at the sediment–water interface, while the remainder is derived from pore water flux.
Divergent Structure in Fish Taxocenes of North Temperate Streams
Authors: Mahon Robin
Published: April 2011

The fish taxocenes of two typical river systems in Poland and Ontario differed in patterns of species richness, distribution, life history, and ecomorphology. In small streams there were more small nektonic and benthic fishes in Ontario. In Poland where large, nektonic cyprinids dominate, the fishes were larger, longer lived, later maturing, and absolutely and relatively more fecund and had longer reproductive spans, but egg diameters were similar. In Ontario, nester/guarders and brood hiders were common, whereas in Poland all but three species broadcast eggs. Small-stream fishes were small, early maturing, short lived, and sedentary and gave parental care to few, large eggs. Large-river fishes displayed opposite characteristics and often migrated to spawn in habitats suitable for young but not adults. The factor space of a principal components analysis of ecomorphological characteristics corresponded roughly to a longitudinal gradient in fluvial conditions. There was a significantly higher proportion of fishes from Poland in the downstream half of the space, and vice versa. The most prominent differences in taxocene structure generalize to west-central Europe and east-central North America. Evidently, several groups of North American fishes invaded and became adapted to small streams, facilitating speciation. European fishes retained the strategy of seasonal/ontogenetic longitudinal migration. Ancestors to the most diverse groups in North America inhabited both continents; consequently, long-term climatic patterns (glaciation) and/or the influence of lowland ichthyofauna are the most likely causes of the differences.
An Improved Flow-through Respirometer for Aquatic Macroinvertebrate Bioenergetic Research
Authors: Wrona Frederick J. , Davies Ronald W.
Published: April 2011

An improved flow-through respirometer that is simple to construct and operate is described. Using an impedance monitoring system, activity-specific aerobic metabolism of macroinvertebrates can be quantified under controlled temperatures and oxygen tensions. Application of the respirometer is demonstrated by examining the activity-specific respiratory responses of two species of Hirudinoidea to 100% air-saturated conditions and differing levels of hypoxia. Acclimation time of the animals to the respirometer chambers is also investigated. Using this type of flow-through system for macroinvertebrate bioenergetic studies, activity-specific respiration measurements can be made under constant abiotic conditions and minimal disturbance to the animals.
An Experimental Determination of the Effect of Increasing the Minimum Age (or Size) of Fish at Capture upon the Yield per Recruit
Authors: Majkowski Jacek , Hearn William S. , Sandland Ronald L.
Published: April 2011

The aim of this paper is to describe a tag release–recapture experiment designed to determine the quantitative effect of increasing the minimum age (or size) of fish at capture upon the yield per recruit for the current intensity of fishing, if the minimum age corresponding to the maximum catch weight per recruit for this fishing intensity is greater than the minimum age that currently applies in the fishery, this optimal minimum age can be determined from a single tag release–recapture experiment. The main advantage of the described tag release–recapture experiment over the experimental approach recommended in the past, but not yet applied, is a reduction in the use of trial and error procedures. Unlike the classical Beverton and Holt yield per recruit analysis, this approach does not require specific information on fish growth and natural and fishing mortalities. Consequently, it can be implemented for many complex fisheries systems. However, as with the classical approach, it does not enable useful predictions to be made when a change in the minimum age significantly alters the number of recruits to the fishable stock. The method of data analysis is developed and illustrated using data on southern bluefin tuna (Thunnus maccoyii).
Uptake of Zn, Cd, and Hg by Fish in the Presence of Competing Compartments
Authors: Ramamoorthy S. , Blumhagen Karen
Published: April 2011

Rainbow trout (Salmo gairdneri) were exposed to Zn, Cd, and Hg in the presence of competing compartments compartmentalized in a novel experimental apparatus. In fish, uptake of Hg was more than doubled in the presence of Zn and Cd (0.45 μg/g). Organic matter decreased the uptake of Hg and Zn but enhanced that of Cd. We concluded that (1) equilibration with one heavy metal ion did not limit the fish in accumulating another heavy metal ion, and in addition to Hg uptake, 0.55 μg Cd/g and 22 μg Zn/g (wet weight) were taken up by fish, suggesting the possible existence of multiple binding sites in fish, (2) mass balancing showed excellent recoveries for Cd and Zn and losses up to 50% for Hg, and (3) the calculated partition coefficients (fish/substrate) for Zn, Cd, and Hg showed that these compartments are critical in the flux of Zn and Cd whereas sediment and suspended solids only determine the flux of Hg.
A Method for the Analysis of Total Nitrogen in Natural Waters
Authors: Kalff J. , Bentzen E.
Published: April 2011

This method for analyzing total nitrogen (TN) in freshwaters is based on the persulfate oxidation of nitrogen to nitrate, followed by the analysis of this nitrate by a modified version of the sodium salicylate method. The method is simpler than other reported techniques for TN in oligotrophy and mesotrophic waters and requires equipment readily available in most laboratories. The method is linear to 1000 μg N/L, with the range extendable by changing the sample size. The variability is lowest (coefficient of variation 6.6%) between 100 and 1000 μg N/L. We have successfully used the method for the determination of TN, as well as dissolved nitrogen (DN) on filtered samples and nitrate on nonoxidized samples.
The Herring: A Successful Species?
Authors: Blaxter J. H. S.
Published: April 2011

The herring has an elaborate racial system closely linked to its spawning habits. Its demersal eggs are laid in a wide range of environments from the deeper parts of the continental shelf to the intertidal zone and in a wide range of salinities and temperatures between latitudes 35 and 70°N. Depending on the race, spawning occurs in all months of the year and the relationship between fecundity and egg size is correlated with the season, with high fecundity and small eggs in the summer and fall and low fecundity and large eggs in the winter and spring. The herring is specially adapted in other respects. There is a complex camouflage system based on silvery layers of guanine crystals in the skin, a specialised retina, and a very complex acoustico-lateralis system linked to the swimbladder. It is physostomous, allowing rapid vertical movements of wide amplitude, and strongly schooling in habit with the facility to switch from particulate to filter-feeding. Filter-feeding can continue in darkness. Although many herring stocks have been overfished, there is no reason to suppose that they cannot recover, to the historical high levels, if properly managed. The stock size varies from millions to hundreds of tonnes, depending on the race, and this has interesting implications for the stock-recruitment relationship.
Growth and Maturation of Pacific Herring (Clupea harengus pallasi) in the Strait of Georgia
Authors: Haist V. , Stocker M.
Published: April 2011

Juvenile growth rate, adult surplus energy, and the maturation schedule for the Strait of Georgia Pacific herring (Clupea harengus pallasi) stock were investigated over the period 1950–81. The variance in weight at age 2 is largely accounted for by juvenile abundance and sea surface temperature, indicating density-dependent juvenile growth moderated by environmental factors. Density and environmental factors have been equally important in moderating juvenile growth. Yearly variation in maturation of 3-yr-old herring is related to their average length; however, in two of the eight years studied the 3-yr-olds matured at considerably smaller sizes. The variance in adult surplus energy (growth plus gonad production) was largely accounted for by body weight, adult biomass, and sea surface temperature. A dome-shaped relationship between surplus energy and biomass was indicated, suggesting that over a broad range of population size, adult surplus energy is not density dependent. The relationship of sea surface temperature to both juvenile growth and adult surplus energy was quadratic with an optimum value. Recruitment biomass has been a relatively larger component than adult production of total stock growth, particularly during the period of high fishing intensity. This resulted in large fluctuations in stock biomass; in recent years, with lower fishing intensity, adult production has been a larger component of stock growth, and the stock biomass has become more stable.
Recruitment Variability and Its Implication for Managing and Rebuilding the Georges Bank Haddock (Melanogrammus aeglefinus) Stock
Authors: Overholtz William J. , Sissenwine Michael P. , Clark Stephen H.
Published: April 2011

The Georges Bank haddock (Melanogrammus aeglefinus) fishery has fluctuated dramatically since the early 1960's. Abundance declined from the mid-1960's to the mid-1970's, partially recovered, and has declined again since 1980. In general, poor year-classes have been associated with a low spawning biomass although the relationship is variable. The fishery was simulated by using the Baranov catch equation, constant growth and natural mortality, and stochastic levels of recruitment whose probabilities correspond to historic patterns in the stock and recruitment data. Simulations suggest a low probability for stock recovery and improved yield under current conditions (F ≈ 0.5). Recovery time increased with increases in fishing mortality (F), and beyond F = 0.40 recovery is unlikely within 25 yr. With recruitment of a very large year-class (100 million fish) an initial strategy providing for a relatively low level of F(= 0.10) for 3−5 yr, followed by exploitation at historically sustainable levels (F = 0.35), would result in stock recovery. With recruitment of a smaller year-class (50 million fish) low initial levels (F = 0.10) and subsequent management at or near F0.1 (F = 0.26) would be required to initiate stock recovery and reasonable harvest levels in future years.
Wind Stress and Cycles in Dungeness Crab (Cancer magister) Catch off California, Oregon, and Washington
Authors: Johnson David F. , Botsford Louis W. , Methot Jr. Richard D. , Wainwright Thomas C.
Published: April 2011

Dungeness crab (Cancer magister) catch records along the coasts of northern California, Oregon, and Washington covary in a cyclic pattern with a period of 9–10 yr. Both environmental forcing and density-dependent recruitment have been proposed as the mechanisms causing these cycles. Spring wind stress in a southward direction is correlated with crab catch along this coast at typical lags of 4 and 5 yr. This time lag corresponds to the time required for growth from the larval phase to the size caught in the fishery. Also, computed autocorrelations show that wind stress is itself cyclic. Since crab larvae appear to be transported offshore and northward during the early larval phase, the observed correlation may result from a dependence of subsequent successful settlement on wind-driven southward, onshore transport during the late larval phae in the spring. However, the exact mechanisms are not known. The computed correlations indicate that wind stress may contribute to the observed cycles.
Calculating the Sensitivity of a Salmonid Population Model
Authors: Evans Geoffrey T. , Dempson J. Brian
Published: April 2011

We present a simple model of salmonid life history, and calculate the sensitivity of its outputs to its parameters. Theoretical calculations are preferred to computer simulations. There are some parameters for which the sign of the sensitivity is independent of the actual parameter values. In an uncertain world, management actions aimed at altering such parameters are safer than other actions. For example, habitat protection measures are more certain to have the desired effect than are changes in fishery regulations.
Smolt Transformation and Seaward Migration in 0-Age Progeny of Adult Spring Chinook Salmon (Oncorhynchus tshawytscha) Matured Early with Photoperiod Control
Authors: Zaugg W. S. , Bodle J. E. , Manning J. E. , Wold E.
Published: April 2011

Maturation of hatchery-held adult spring-run chinook salmon (Oncorhynchus tshawytscha) was accelerated by decreasing photoperiods. Spawning occurred 1 mo earlier than with nontreated fish. Because of early hatching, progeny from the photoperiod regulated adults were larger and exhibited signs of parr–smolt transformation such as changes in coloration and behavior, elevation of gill Na+-K+ ATPase activity, and active seaward migration at age 0, nearly 1 yr prior to usual releases of juveniles from normally spawned adults.
Effects of Initial Conditions on Monte Carlo Estimates of Bias in Estimating Functional Relationships
Authors: Kope Robert G.
Published: April 2011

Some of the results presented by Walters (1985. Can. J. Fish. Aquat. Sci. 42: 147–149) for the magnitude of bias in estimating functional relationships from time series data resulted from his choice of initial stock size in Monte Carlo simulations rather than the dynamics of the model. Walters used the same initial stock size in each simulation while varying parameters in the stock–recruitment relationship. Starting each simulation at the equilibrium stock size or allowing initial stock size to vary randomly produces larger estimates of bias and leads to different conclusions about the relationship of bias to parameter values in the model.
Life History and Smolt-to-Adult Survival of Keogh River Steelhead Trout (Salmo gairdneri) and the Relationship to Smolt Size
Authors: Ward B. R. , Slaney P. A.
Published: April 2011

A decade of data on wild steelhead trout (Salmo gairdneri) from a coastal stream in British Columbia demonstrated large fluctuations in smolt number, age structure, size, estimates of adult run sizes, smolt-to-adult survival, and adult age. Adult runs averaged 922 (range 209–2730) with approximately 10% repeat spawning incidence. Females repeat spawned more than males and were more abundant as kelts, but maiden run adults were equally male and female. The proportion of males returning after 1, 2, and 3 yr in the ocean averaged 3, 62, and 35%, respectively; 58 and 42% of females returned after 2 and 3 yr, respectively. Adult age structure, smolt number, and smolt size varied biennially. Adult size decreased with freshwater age, but increased with ocean age of returns. Males were larger at each ocean age. Mean number of smolts (50:50 sex ratio) was 5543 and varied fivefold. Mean smolt length was 173 mm and mean weight was 49 g. Smolts were 2–5 yr old, and freshwater age 3 was most prevalent (average 56%). Mean survival from smolt to adult was 16% (7% from 1978 cohorts to 26% from 1982 cohorts). Survival was positively correlated with smolt length and weight. However, 1982 cohorts had twice the survival of other cohorts, possibly related to El Niño. No clear relationship was found between return age and mean smolt size, but on average, freshwater age was inversely related to ocean age. The relationships suggest that predictive models may be developed over the longer term from this type of study.
Hydraulic Geometry in Small, Coastal Streams: Progress Toward Quantification of Salmonid Habitat
Authors: Hogan Daniel L. , Church Michael
Published: April 2011

It is difficult to quantify in-stream physical attributes of salmonid habitats, yet quantification is necessary if conditions are to be compared within or between streams over time or space. This paper presents an objective method based on hydraulic geometry to quantify hydraulic characteristics of fish habitat. Two small streams in coastal British Columbia provide examples. Morphological mapping and streamflow measurements were used to generate the bivariate distributions of mean depth and mean velocity at cross sections within the study reaches at various discharges. The distributions are used to generate measures of potentially useable area within the streams. Survey criteria and numerical adjustments are presented to improve comparability between channels. The streams respond similarly to a change in discharge. The main hydraulic difference is a decrease in area useful to coho salmon (Oncorhynchus kisutch) for rearing at higher discharges in Bonanza Creek (logged) compared with Hangover Creek (unlogged). The example indicates that quantitative comparisons can be made, at comparable flows, between reaches and between streams, or over time.
Mitochondrial DNA Sequence Similarity of Atlantic and Pacific Albacore Tuna (Thunnus alalunga)
Authors: Graves John E. , Dizon Andrew E.
Published: April 2011

Restriction endonuclease analysis of mitochondrial DNA purified from 11 south Atlantic (Capetown, South Africa) and 12 north Pacific (San Diego, USA) albacore tuna (Thunnus alalunga) revealed no restriction sites which could distinguish an Atlantic from a Pacific albacore. Although restriction site variation was found within the pooled sample, variants were found only in single fish. These results suggest either recent isolation of Atlantic and Pacific albacore or, more likely, at least a small amount of migration between the two ocean basins.
Characterization of Aeromonas salmonicida Strains using DNA Probe Technology
Authors: Hennigan Martha , Vaughan Laurence M. , Foster Timothy J. , Smith Peter , Gannon Frank
Published: April 2011

Epizootiological studies on Aeromonas salmonicida are important in view of its role as the causative agent of furunculosis. The use of DNA probes to detect restriction fragment length variations promised to provide a new way to distinguish between different strains of the organism. We used four different DNA probes in combination with seven restriction enzymes to compare seven strains of A. salmonicida. Despite the diversity of the geographical origins of the organisms no differences in the patterns of the hybridizing bands were found. This suggests that the DNA sequences of A. salmonicida are very strongly conserved and that the potential for DNA probes to identify different strains may be limited.
Variability, Tuning, and Simulation for the Doubleday–DerisoCatch-at-Age Model
Authors: Kimura Daniel K.
Published: April 2011

This paper presents a method for estimating the variances of biomass estimates made using the nonlinear least squares catch-at-age model. The estimates begin with the standard covariance matrix of parameters estimated using nonlinear least squares and is therefore an extension of usual methods. In this paper the catch-at-age model is tuned to independent survey estimates of biomass. If the variances of these survey estimates are known, it is possible to estimate an optimal value for the weighting variable λ in the nonlinear least squares. The methods are applied to the walleye pollock (Theragra chalcogramma) fishery in the Eastern Bering Sea. Results from this study generally support the theoretical interpretation of λ as a ratio of variances. When the model is constrained to recent survey biomass estimates, estimates of the coefficient of variation of biomasses in earlier years are large. Also, the results largely depend on what constraints on selectivities are assumed. A simulation was performed assuming catches-at-age are distributed as lognormal random variables and that selectivities are all estimated. Results from the simulation indicate that modelled biomass estimates for early years are questionable, and probably seriously biased. However, the simulation generally validated the analytic estimates of the variance of modelled biomass estimates.
Concentration of Infectious Hematopoietic Necrosis Virus from Water Samples by Tangential Flow Filtration and Polyethylene Glycol Precipitation
Authors: Batts W. N. , Winton J. R.
Published: April 2011

Infectious hematopoietic necrosis virus (IHNV) was concentrated from water samples by polyethylene glycol (PEG) precipitation, tangential flow filtration (TFF), and by a combination of TFF followed by PEG precipitation of the retentate. Used alone, PEG increased virus titers more than 200-fold, and the efficiency of recovery was as great as 100%. Used alone, TFF concentrated IHNV more than 20-fold, and average recovery was 70%. When the two techniques were combined, 10-L water samples were reduced to about 300 mL by TFF and the virus was precipitated with PEG into a 1 to 2 g pellet; total recovery was as great as 100%. The combined techniques were used to isolate IHNV from water samples taken from a river containing adult sockeye salmon (Oncorhynchus nerka) and from a hatchery pond containing adult spring chinook salmon (O. tshawytscha). The combination of these methods was effective in concentrating and detecting IHNV from water containing only three infectious particles per 10-L sample.
Maximum Likelihood Estimation of Water Quality Concentrations from Censored Data
Authors: El-Shaarawi A. H. , Dolan D. M.
Published: April 2011

Concentration data for water quality parameters reported as less than the detection limit (DL) may be considered to have come from a censored probability distribution. Traditionally, if it was necessary to assign a value to a sample reported as less than DL, various ad hoc methods were used such as selecting arbitrary values (0, 1/2 DL, DL, etc.). As analytical methods improved, DL's became smaller and the choice of ad hoc methods had less of an effect. However, there are two cases where the choice of estimation method is still a problem: (1) it is desired to calculate a differential loading (i.e. downstream minus upstream); (2) a loading estimate is desired in a tributary whose flow rate is extremely large. Both cases apply in connecting channels such as the Niagara and Detroit Rivers. The background for development of a nonarbitrary method for handling these situations is presented and the resultant estimator is used on water quality data from the connecting channels and Lake Ontario. The equations for confidence intervals for estimated mean concentrations or loadings are also presented. The effect of changing the DL is discussed.