bluuebunny/crossref_metadata_2025 huggingface dataset:
Baseline Levels of Volatile Hydrocarbons and Petroleum Residues in the Waters and Sediments of the Grand Banks
Authors: Levy E. M.
Published: April 2011

Baseline levels of low molecular weight volatile hydrocarbons and petroleum residues in the Grand Banks area were measured in April 1981 with a focus on the Hibernia and South Tempest sites where exploration for oil was occurring. Concentrations of volatile hydrocarbons ranged from 0.41 to 1.80 nmol/L (geometric mean = 0.74 nmol/L) in the water column and 0.05–3.20 mmol/L in the surficial bottom sediments. The former, almost exclusively methane, were of recent biological origin, while the latter, which also contained ethane, propane, and butane, were probably related to petroleum. There was no visible evidence of surface slicks at the time, and floating particulate petroleum residues were absent from most locations. Concentrations of dissolved/dispersed petroleum residues in the sea surface microlayer ranged from 14 to 440 μg/L (geometric mean = 28.9 μg/L) and in the water column from 0.05 to 4.1 μg/L. Concentrations of petroleum residues in the surficial bottom sediments ranged from 0 to 7.3 μg/g. While these levels are among the lowest found anywhere in the waters and sediments off eastern Canada and in the eastern Arctic, there was evidence that the oil industry, even at the level of its activity at the time, was having a detectable impact on background levels of petroleum-related substances in the sea surface microlayer and the surficial bottom sediments.
Particulate Hydrocarbon and Coprostanol Concentrations in Shelf Waters Adjacent to Chesapeake Bay
Authors: Wade T. L. , Oertel G. F. , Brown R. C.
Published: April 2011

Adjacent to the entrances of major estuaries, the concentrations and distributions of particulate coprostanol, hydrocarbons, and total suspended matter are controlled by both small-scale and large-scale processes. These processes result in the development of spatially separate plumes of coprostanol, hydrocarbons, and total suspended matter. Particle buoyancy appears to be a major factor controlling the sorting of particles into the three discrete plumes. At the inner shelf adjacent to the Chesapeake Bay entrance, patchiness of coprostanol, hydrocarbon, and total suspended matter concentrations is also controlled by alongshore wind stress which enhances the uncoupling of the distal ends of plumes. While Chesapeake Bay appears to be a chronic source of anthropogenic materials to adjacent shelf water, major pathways of several pollutants (sewage derived and hydrocarbons) do not spatially coincide with turbid or low-salinity plumes.
The Behavior of Arsenic in Selected United Kingdom Estuaries
Authors: Langston W. J.
Published: April 2011

High As concentrations occur in certain United Kingdom estuaries as a result of mineralization and associated processes including mining and metal refining. Analyses of dissolved and particulate As, carried out in estuaries of differing contamination, indicate that As is readily precipitated with Fe during mixing at the freshwater–seawater interface. This gives rise to significant correlations between the two elements in suspended and bottom sediments. More than 80% of the As entering Restronguet Creek, the most contaminated of the estuaries studied, is retained by estuarine sediments, which consequently act as sinks for riverine inputs and limit transport of dissolved species to coastal waters. However, the behavior of As in different estuaries varies with the physicochemical conditions present and the nature of the source. Most significantly, remobilization of sediments is recognized as a feature affecting the cycling of As in the Tamar Estuary.
Geochemkal Transport Through the Miramichi Estuary
Authors: Buckley D. E. , Winters G. V.
Published: April 2011

A 2-yr seasonal study of the physical oceanography, geochemistry, and sedimentology of the Miramichi Estuary, New Brunswick, demonstrated that the overall system consists of two compartments: a drowned river, variable salt wedge estuary which is normally highly stratified, and the connected Inner Bay which is slightly stratified to well mixed. Freshwater inputs at the head of the estuary vary from 50 to 250 m3∙s−1 during summer and winter to high flows of 300 to 1700 m3∙s−1 during spring. Suspended particulate matter (SPM) and several labile trace metals including Fe, Mn, Zn, Cu, Pb, and Cd were analyzed to determine the total transport of potential contaminants within the system and into the Gulf of St. Lawrence. Wide variations in concentrations of SPM and labile metal by more than an order of magnitude are a function of freshwater input rates, tidal prism flushing characteristics, and geochemical interactions within the estuary. The transports for SPM, particulate metals, and labile metals were calculated using a tidal prism flushing model. Although 70% of the annual input of SPM (95 000 t) is exported from the estuarine system, about 60% of the total Fe (2000 t) is trapped in the estuarine bottom sediments. By contrast, 50% more Mn (200 t) is exported in combined particulate and labile forms than is brought into the estuary by the river. The source of this additional Mn is remobilization from fine-grained reduced bottom mud. The most important sink for Fe, Zn, Pb, and Cd appears to be the organic-rich bottom muds of the upper estuary. During spring flood periods, which last for an average of 39 d, about 85% of the annual supply of SPM enters the river estuary from the Miramichi River. Also during this time, 30–55% of the annual supply of labile metals Fe, Mn, Zn, and Cu enter the system. Much of this spring influx of SPM and metal is remobilized in the estuary over the rest of the year.
Calculation of Diffusion Resistances Controlling Volatilization Rates of Organic Contaminants from Water
Authors: Mackay Donald , Shiu Wan Ying , Chau Eva
Published: April 2011

A theoretical analysis is presented describing the rates of volatilization (and thus half-lives) of organic compounds from solution in surface waters, which is a reformulation of the existing "two-resistance" approach. It is extended to treat the more complex situation of volatilization from water in which the solute is also present in dispersed oil particles or in sorbed form and experiences a dissolution resistance which may prolong the volatilization half-life. We suggest that the separate calculation of half-lives (1) for volatilization from solution and from dispersion and (2) for dissolution assists the elucidation of the dominant rate-controlling processes. Satisfactory agreement is obtained between predicted concentration decay behaviour and data obtained in exploratory laboratory experiments and under dispersed oil slicks at sea.
A Large-Volume Sampling Assembly for the Determination of Synthetic Organic and Petroleum Compounds in the Dissolved and Particulate Phases of Seawater
Authors: Lappe B. W. de , Risebrough R. W. , Walker II W.
Published: April 2011

A system for the in situ sampling of subsurface seawater for the determination of synthetic organic and petroleum compounds in concentrations of picograms per litre is described. Seawater from in front of the bow of the vessel was pumped through a stainless steel tube into a cleanroom, through a glass fiber filter, and through parallel or serial Teflon® columns packed with a porous polyurethane foam (PPF) solid adsorbent. The majority of hydrocarbons associated with seawater particles were quantitatively recovered. The efficiency of the foam columns in extracting the dissolved phase was determined by intercaiibration with liquid–liquid extraction using cyclohexane and by separate analyses of two columns mounted in series. Recovery of polychlorinated biphenyls, several chlorinated hydrocarbon biocides, and aromatic hydrocarbons was quantitative with a single PPF column. Measured concentrations were in the low picogram per litre range for chlorinated organics and the nanogram per litre range for total petroleum. Reduction of contamination during sampling remains of paramount importance in the determination of hydrocarbon concentrations in seawater.
Fate and Transport of Selected Herbicides in an Estuarine Environment
Authors: Means J. C. , Wijayaratne R. D. , Boynton W. R.
Published: April 2011

Representative compounds from three classes of herbicides (atrazine, linuron, and treflan) were studied to determine ambient levels in the Chesapeake Bay and its tributaries during portions of 1980. All levels were 1 μg/L or less, and all three herbicides exhibited non-conservative behavior in the estuary. Concentrations of herbicides in runoff from a defined watershed did not exceed 9 μg/L. Degradation rates for all three herbicides in estuarine sediment-water systems were 2–10 times greater than those reported for soils. Equilibrium sorption constants (Koc) of estuarine sediments were similar to soils, but suspended colloids were found to sorb atrazine and linuron 10–30 times more strongly on a per gram of carbon basis, suggesting that refractory hydrophobic pollutants may be transported greater distances in the water column than previously assumed. However, the large degradative capacity of the estuarine community may act to prevent transport of labile organics from the land to the oceans.
Recent Colonization of a Major Salmon-Producing Lake in British Columbia by Pacific Lamprey (Lampetra tridentata)
Authors: Farlinger Susan P. , Beamish Richard J.
Published: April 2011

Pacific lamprey (Lampetra tridentata) were first observed in Babine Lake, the largest natural lake wholly contained in British Columbia, in 1963 and are currently found along approximately 15% of the length of the lake near the outlet. The number of spawning adults in 1982 was estimated to be 7281. Since Babine Lake is a major nursery area for sockeye salmon (Oncorhynchus nerka), the colonization of this lake by a parasitic lamprey is of concern, particularly if the species can become nonanadromous. The colonization may be beneficial if a commercial fishery can be sustained and if the species does not begin to feed in freshwater. The reason for the recent colonization is unknown but it coincides with increased human manipulation of fishes and habitat, including the removal of a major rock slide, 65 km downstream of the lake.
Spawning Site Water Chemistry and Lake Trout (Salvelinus namaycush) Sac Fry Survival during Spring Snowmelt
Authors: Gunn J. M. , Keller W.
Published: April 2011

During the spring of 1982, lake trout (Salvelinus namaycush) sac fry were incubated at a spawning bed in a pH 5.7 lake with a history of lake trout recruitment failure. Four short episodes of substantial pH depression occurred at the spawning site. Observed sac fry mortalities (18%) occurred primarily during the longest depression (5 d at pH 4.5–5.0), which coincided with maximum surface runoff and peaks in concentrations (~50 μg/L) of inorganic (monomeric) Al. Although most mortalities were coincident with low pH and elevated inorganic Al concentrations, the high survival (82%) demonstrated that under natural conditions most sac fry could tolerate pH <5.0 and inorganic Al concentrations of 40–50 μg/L for at least 5 d. Substantially higher concentrations of inorganic Al (~80 μg/L) were observed in the interstitial waters of the spawning rubble than in ambient waters, which indicated that fry within a spawning substrate may be subjected to more toxic conditions than test fry in incubators above the substrate surface.
Contribution of Particulate Phosphorus (> 250 μm) to the Total Phosphorus Pool in Lake Water
Authors: Prepas E. E. , Vickery J.
Published: April 2011

Particulate phosphorus (PP) > 250 μm was concentrated in the euphotic zone of 17 lakes in central Alberta. When the euphotic zone extended below the epilimnion, PP >250 μm was concentrated deep in the euphotic zone. PP > 250 μm was a significant but variable portion of the total phosphorus (TP) pool in individual lakes; thus, samples should be collected from the euphotic zone on several dates to estimate the contribution of PP > 250 μm to the TP pool. As well, the contribution of this fraction varied among lakes: average summer values for the euphotic zone ranged from 3 to 19%. Among lakes, the contribution of large particles to the TP pool decreased proportionally as lake productivity (estimated by chlorophyll a (Chl a)) increased. The relative contribution of PP > 250 μm in summer accounted for a significant portion of the residual variation in the spring TP-summer Chl a relationship but not the summer TP-summer Chl a relationship in the study lakes. These apparently contradictory results can be explained by differences between lakes that mixed intermittently throughout the summer and those that remained permanently thermally stratified during this time.
Behavioral Response of Blacknose Dace (Rhinichthys atratulus) to Varying Densities of Predatory Creek Chub (Semotilus atromaculatus)
Authors: Fraser Douglas F. , Emmons Edward E.
Published: April 2011

We investigated the behavioral response of juvenile blacknose dace (Rhinichthys atratulus) to varying levels of predation risk by varying the density of predatory creek chub (Semotilus atromaculatus) and amount of structure in compartments of an artificial field stream. When structure in predator locations was low, dace did not avoid predators during the day but did at night, responding equally regardless of predator density. When structure was increased, the strength of avoidance at night was dependent on both the amount of structure and density of predators. Predators in experimental compartments caused dace to move to other locations of the stream. By moving away from predators, dace gain a short-term benefit in avoiding predation and a long-term benefit by reducing the chance of becoming trapped in pools with piscivorous fish when water levels in a natural stream drop. However, this shift could reduce feeding if dace move to locations poor for foraging or high in density of dace.
Fyke Net Catches as Indices of the Abundance of Brook Trout, Salvelinus fontinalis, and Atlantic Salmon, Salmo salar
Authors: Ryan P. M.
Published: April 2011

The catch per unit effort (CPUE) data of brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) in fyke nets set in two small lakes in central Newfoundland were compared with population densities estimated with Schnabel multiple mark–recapture experiments each spring and fall from 1978 to 1982. The catchability of brook trout did not differ significantly between lakes or seasons, and CPUE was an index of the relative abundance of trout within and between lakes. In contrast, the catchability of Atlantic salmon differed greatly between lakes and varied seasonally, being greater in the spring but less in the fall than the catchability of brook trout. Comparisons of relative salmon abundance between lakes or of the relative abundance of brook trout to Atlantic salmon within or between lakes require a correction for seasonal differences in the catchability of salmon.
Ethanol Fraction of Lacustrine Colloidal Fibrils
Authors: Burnison B. Kent , Leppard Gary G.
Published: April 2011

Ethanol fractionation of colloidal organic fibrils can provide a highly purified fraction in appropriate quantities for standard chemical analyses of fibril structure and function. Using a sequential ethanol precipitation procedure, applied to lacustrine fibrils isolated and concentrated by physical separation techniques, we obtained a fibril fraction (approximately 60% yield). Its characteristics were as follows: (1) absence of any major category of colloidal impurity detectable by transmission electron microscopy, (2) relative freedom from fibrils of atypical morphology, (3) relative freedom from a class of small granules, typically associated with lacustrine fibrils and with some other kinds of polyanionic fibrillar colloids found in nature, (4) freedom from derivatization reactions, and (5) freedom from an undesirable exposure to caustic reagents. Our objective was to arrive at a nondegradative fractionation procedure that yielded a fraction relatively free of other colloidal components found in lake water. This fraction would then be appropriate for assays of heavy metal binding and bioavailability.
Importance of Estuarine Residence for Adaptation of Chum Salmon (Oncorhynchus keta) Fry to Seawater
Authors: Iwata Munehico , Komatsu Shichiko
Published: April 2011

Within 24 h after release from the Otsuchi Salmon Hatchery in Japan, most chum salmon (Oncorhynchus keta) fry migrated the 1.7 km and were found in the surface layer (10–15‰ salinity) of the estuary. No fish were seen in the underlying seawater. Many fry remained in the brackish water for 2 d before migrating seaward. Plasma Na concentrations increased gradually from 134 to 156 mmol/L during seaward migration from the river to Otsuchi Bay. When fry were acclimated to one-third seawater for 3 and 6 h and then transferred to seawater, the Na concentration of the fry increased maximally to 161–172 mmol/L within 12 h. When they were acclimated to one-third seawater for 12 h, the Na concentrations reached the seawater-acclimated level without showing any peak; subsequent exposure to seawater did not cause any further change in plasma Na. Acclimation to isotonic estuary water for 12 h is thus sufficient for efficient adaptation of chum salmon fry to seawater.
Biological Availability of Soluble Reactive Phosphorus in Anoxic and Oxic Freshwaters
Authors: Nürnberg Gertrud , Peters Robert H.
Published: April 2011

The availability of hypolimnetic phosphorus was assessed by a short-term bioassay, based on 32P uptake kinetics. In the anoxic hypolimnia of eight lakes and in anoxic model systems (core tubes), at least 80% of soluble reactive phosphorus is biologically available. However, biologically available phosphorus is only a small fraction of soluble reactive phosphorus in iron-rich, previously anoxic waters after aeration and in lake water from the anoxic–oxic interface. This result is supported by published data for oxic waters from epilimnia of lakes, rivers, sewage effluent, and precipitation.
Mollusca of Six Low-Alkalinity Lakes in Ontario
Authors: Rooke J. Brian , Mackie Gerald L.
Published: April 2011

In 1980 and 1981, we sampled the molluscs of six Ontario lakes with low alkalinity concentrations. Contrary to previous reports of rarity or absence of molluscs in low-alkalinity waters, we showed that there was no consistent difference in the number of species present in these lakes, across a limited range of alkalinity (0.24–3.17 mg∙L−1). It is possible that molluscs are more dense in lower alkalinity lakes, due primarily to large numbers of Pisidium casertanum and P. ferrugineum found there. Significant differences between mollusc densities in two intermediate-alkalinity lakes indicate that factors other than alkalinity may have affected mollusc distributions. The unionid clam, Elliptic complanata, was found in two lakes with mean alkalinities of 0.41 mg∙L−1.
A Medium for the Isolation and Differentiation of Yersinia ruckeri
Authors: Waltman W. Douglas , Shotts Jr. Emmett B.
Published: April 2011

A new medium, Shotts–Waltman (SW), was developed for the isolation and differentiation of Yersinia ruckeri; Y. ruckeri was distinguished by its ability to hydrolyze Tween 80 and inability to ferment sucrose. SW was shown to be as sensitive as MacConkey and trypticase soy agars for the growth of Y. ruckeri. SW is inexpensive, prepared easily, and should greatly increase the recovery of Y. ruckeri from clinical material and infected fish.
Influence of the Insecticide Diflubenzuron (Dimilin) on the Growth of Marine Diatoms and a Harpacticoid Copepod in Culture
Authors: Antia N. J. , Harrison P. J. , Sullivan D. S. , Bisalputra T.
Published: April 2011

Diflubenzuron (Dimilin) was tested, in the concentration range 0.1–5000 μg∙L−1, for possible injurious effects on the growth and photosynthesis of three chitin-producing (Thalassiosira weissflogii, T. norden-skioldii, Cyclotella cryptica) and one nonchitinaceous (Skeletonema costatum) diatoms. For comparison, the effects of the pesticide were also examined on adult survival and juvenile development of the harpacticoid copepod Tigriopus californicus. While the development of the copepod was hindered at concentrations of the order of 1–10 μg∙L−1, the diatoms were barely affected by Dimilin even at the highest concentration tested (5 mg∙L−1). We conclude that Dimilin acts specifically on insects and crustaceans as a larvicide by interfering with chitin deposition into cuticles during juvenile development through ecdysis. The lack of effect from Dimilin on the chitin-producing diatoms has suggested that the insecticide may not inhibit chitin biosynthesis per se as was previously believed, but that it presumably deregulates one or more of the larval postsynthetic processes responsible for chitin integration into cuticles.
Nutrient Dynamics in a Littoral Sediment Colonized by the Submersed Macrophyte Myriophyllum spicatum
Authors: Carignan R.
Published: April 2011

The distributions of porewater reactive phosphorus (RP), NH4+, K, and inorganic carbon (ΣCO2) are compared for sediments colonized by Myriophyllum spicatum (9–40 g∙m−2) and sediments experimentally maintained plant-free. Porewater nutrients are characterized by a high spatial and temporal variability. During the summer months, root activity induces marked reductions in porewater RP and NH4+ between 5 and 38 cm. However, this trend is reversed in spring and fall when higher nutrient concentrations are observed in the colonized sediments, presumably as a result of root decay. Root activity is also associated with higher ΣCO2 and K in the porewaters. Exchangeable NH4+ is the largest pool of available N and exhibits a relatively rapid (9.5–24 d) turnover time in colonized sediments. The mineralization of organic matter is an important source of sediment NH4+ and comparable in quantity with the N requirement of the macrophytes. These results suggest that under conditions of nutrient limitation, the rate of nutrient production from sedimentary organic matter decomposition may be a good predictor of macrophyte growth.
Standing Stock and Production of Fish in a Cascading Lake System on the Canadian Shield
Authors: Kelso John R. M.
Published: April 2011

To examine factors influencing fish biomass and production, I carried out a multiple mark and recapture program in a cascading lake system on the Canadian Shield. Standing stock and production were determined for all "large" fish (vulnerable to the gear in use) in the system. Total fish biomass (range 5.2–24.8 kg∙ha−1) decreased with progression downstream and with increasing depth. Production ranged from approximately 2.2 to 6.6 kg∙ha−1∙yr−1 and operated in a manner identical to standing stock. Salmonid flesh production, however, formed a greater proportion to overall fish production in the downstream, less productive lakes. Biomass was strongly influenced by lake depth in this watershed, and this was confirmed by examination of other published data for fish biomass and production in Shield lakes.
Some Speculations about the Baltic Herring (Clupea harengus membras) in Connection with the Eutrophication of the Baltic Sea
Authors: Aneer G.
Published: April 2011

In this paper the hypothesis is put forward that Baltic herring (Clupea harengus membras) spawning time, spring or autumn, is determined by feeding conditions during the adult phase and thus not genetically fixed. The present "absence" of autumn spawners is thought to be the result of improved feeding conditions during the latest decades as a result of the eutrophication of the Baltic Sea. During two spawning ground studies carried out in 1978 and 1982 unusually high mortality rates were noted for eggs in situ. In 1982, during 4 wk close to peak of spawning, the mortality increased substantially, especially for eggs among filamentous algae. A significant difference was noted between eggs on coarser algae and those among filamentous algae (p < 0.001). During this period the average mortalities were 33 and 75%, respectively. Very low levels of oxygen were measured at night among the filamentous algae. An increase in the amounts of this type of algae as a response to the eutrophication might constitute a new hazard to the reproductive success of the Baltic herring.
Life History Characteristics, Reproductive Value, and Resilience of Pacific Herring (Clupea harengus pallasi)
Authors: Ware D. M.
Published: April 2011

The energy supply available for growth and reproduction (surplus energy), fecundity, and egg size increase with female size in British Columbia stocks of Pacific herring (Clupea harengus pallasi). Fecundity is directly proportional to body weight, whereas egg weight is a curvilinear function with a weight exponent of about 0.2. The reproductive rate, defined as the product of fecundity and egg weight, is, therefore, proportional to the 1.2 power of the body weight. In 1974, 1978, and 1980 the size-dependent fecundity and reproductive rates were remarkably constant among management divisions along the coast. There is no evidence at present that these rates respond significantly to natural variations in stock abundance or marine climate, in contrast, there were interannual and regional differences in surplus energy that appeared as differences in the growth rate. Cluster analysis of the average length at ages 3–7 indicated that herring returning to the same division to spawn were more alike than those between divisions. An approximate reproductive value was calculated for the Queen Charlotte Island stock from the foregoing information, assuming that the population was momentarily at equilibrium. For the suspected natural mortality rate (M = 0.45), the maximum reproductive value occurred quite late in the life span: between ages 9 and 10. in other stocks of Pacific and Atlantic herring (Clupea harengus harengus), with adequate time series, the growth rates and hence weight-at-age have increased by as much as 50% in response to a combination of fishing and adverse environmental changes which reduced population size. Concurrently the age at first maturity fell by as much as 2 yr. It is argued that the maximum growth response of a herring population roughly defines its ability to stabilize itself. If the maximum compensatory response is a 50% increase in weight at age, the population should be able to sustain an annual exploitation rate between 0.2 and 0.3. In principle, at this level of harvesting the population will be as resilient to a short run of unfavorable conditions as an unexploited stock
Environmental Effects on Recruitment, Growth, and Vulnerability of Atlantic Herring (Clupea harengus harengus) in the Gulf of Maine Region
Authors: Anthony V. C. , Fogarty M. J.
Published: April 2011

Atlantic herring (Clupea harengus harengus) recruitment in the Gulf of Maine since 1947 has varied by a ratio of 20 to 1. Since heavy fishing began in the mid-1960's, recruitment has fluctuated by only a factor of 9 to 1. The greatest fluctuations in recruitment, therefore, historically occurred in the absence of high fishing mortality. Recruitment predictions and understanding of the causes of fluctuations are extremely important, since strong year classes traditionally have sustained the herring fisheries in the Gulf of Maine. The effect of environmental variables (particularly temperature) on herring recruitment and growth were examined in detail. Vulnerability of Gulf of Maine herring in response to moon phase is also considered. Indices of abundance of Atlantic herring in the Gulf of Maine were calculated for three time periods using three different procedures. Indices of abundance for the periods of 1915–67 and 1951–81 indicated that productivity, or amount of recruitment per amount of spawning stock, was positively related to temperature or other factors (e.g. food availability) related to temperature at intermediate to high levels of spawning stock biomass. For the shorter and most recent time period (1965–81), abundance was calculated by virtual population analysis and an attempt was made to relate temperature effects during several periods in the first year of life to recruitment levels at age 2. The mean, maximum, and minimum water temperatures during (1) September–December (spawning – early larval development), (2) January–April (overwintering and late larval development), and (3) May–August (postlarval) periods were correlated with abundance. Significant effects of mean and minimum temperature during period 2 and minimum temperature during period 3 were observed, suggesting that environmental influences on determination of year class strength occur during late larval – early juvenile phases. Possible reasons for the discrepancy between the long-term analyses bases on abundance indices and the more detailed analyses using population size estimates based on virtual population analysis are discussed. An indication of environmental limitation is also shown by density-dependent growth. Growth appears to be related to both age 2 abundance and summer water temperature. When abundance is great, its effect overcomes the positive effect of temperature (or other factors indicated by temperature). The environment also alters the availability and vulnerability of herring to the inshore fisheries. Young herring are more available and vulnerable to fixed gear during the dark phase of the moon. This effect is pronounced when abundance is low.
Environmental Variation and Recruitment of Pacific Herring (Clupea harengus pallasi) in the Strait of Georgia
Authors: Stocker Max , Haist Vivian , Fournier David
Published: April 2011

We used an age-structured model to estimate recruitment for the Strait of Georgia Pacific herring (Clupea harengus pallasi) population. The model used for herring is a version of the model described in Fournier and Archibald (1982. Can. J. Fish. Aquat. Sci. 39: 1195–1207), modified to include spawn survey information. Three structural assumptions are made to include the spawn data: (1) the form of the relationship between the actual spawn and the observed spawn, (2) the form of the relationship between escapement and actual spawn, and (3) the existence of a Ricker spawn–recruitment relationship, with a multiplicative environmental component. In order to determine which environmental factors had a significant effect on recruitment, we attempted to explain the residual variation from the Ricker curve with the environmental variables using exploratory correlations. Temperature, river discharge, sea level, and sunlight were examined. A multiplicative, environmental-dependent Ricker spawn–recruitment model was used to identify significant environmental variables. The model suggests a significant dome-shaped relationship between temperature and spawning success with an optimal temperature during larval stages resulting in maximum production of recruits. Also, increased spawning success is associated with increased summer river discharge. The significant environmental variables were included in the age-structured model in a stock–environment–recruitment relationship, and all model parameters were reestimated. The overall model fit improved only marginally with the inclusion of environmental variables, as indicated by the objective function value. However, the S–R component of the objective function dropped by 23% when environmental variables were included.
Productivity of Pacific Herring (Clupea harengus pallasi) in the Eastern Bering Sea under Various Patterns of Exploitation
Authors: Fried Stephen M. , Wespestad Vidar G.
Published: April 2011

Pacific herring (Clupea harengus pallasi) is a major food source for western Alaska native people and has been commercially exploited in the eastern Bering Sea since the early 1900's. Commercial harvests were small and localized in coastal waters until foreign factory fleets located and developed a fishery on wintering herring concentrations in the early 1960's. Harvests peaked near 150 000 t in the early 1970's and then declined along with catch per unit effort. Foreign harvests were eliminated following establishment of the United States 200 mile Fishery Conservation Zone. In recent years a fishery has developed in State of Alaska coastal waters which harvests herring for sac roe (ovaries) during the spring spawning period. Proposals have been put forth by trawl fishermen to reestablish a food and bait fishery within Federal waters. Development of offshore mixed stock fisheries has been opposed by inshore commercial and subsistence users who fear that stocks will be overexploited. While both State and Federal managers have agreed to give subsistence users and inshore domestic commercial fishermen top priority, they have been unable to agree upon plans for dealing with potential offshore commercial harvests. In this paper we present results of a computer model that we developed to examine effects of various fishing patterns upon herring productivity and yield. Within our model, maximum sustainable yield (MSY) is achieved at an exploitation rate (E) of 0.3 (i.e. harvest of 30% of total spawning biomass). However, since stocks still appear to be below MSY biomass and since productivity and yield drop sharply at E values greater than 0.3, we suggest that an E of 0.2 be maintained under current conditions. This will result in a potential loss in yield of only 7% from an E of 0.3, but will allow a 52% increase in spawning biomass. Four fishing patterns in which both discrete and mixed stock fishery removals were allowed to occur were also examined. During years in which inshore fisheries fail to harvest 20% of available spawning biomass, an offshore allocation of up to 10 000 t could be permitted with minimal risk to damaging the reproductive potential of small spawning stocks. However, results indicated that mixed stock fisheries should be restricted to lower levels than would be appropriate for fisheries targeting on discrete stocks to avoid risks of overharvesting some stocks.
Fortuity Disguised as Fisheries Management: The Case History of Fortune Bay Herring
Authors: Winters G. H. , Dalley E. L. , Moores J. A.
Published: April 2011

The population dynamics of a stock of spring-spawning herring in Fortune Bay, Newfoundland, are described in relation to exploitation patterns, management strategies, and environmental variability. Biomass levels increased substantially during the late 1960's as a result of the recruitment of several strong year-classes that were pulse-fished by a purse-seine fishery. The resulting high fishing mortality rates caused a rapid stock decline in the early 1970's that was associated with an increase in the partial recruitment rate of the younger age-groups as well as an increase in the catchability coefficient of the purse-seine fleet. The combination of these classical changes resulted in a substantial overestimation of stock abundance and recruitment levels that was not corrected until an alternative series of catch rates and partial recruitment estimators were used to fine-tune population assessment. Environmental factors, rather than spawning stock size, were shown to explain a significant fraction of recruitment variability. Alternative fishing strategies such as the F0.1 and surplus production concepts were simulated and shown to be less efficient in extracting biomass yield than pulse-fishing. It is concluded, therefore, that management regimes whose objectives are promulgated on the basis of stock rebuilding, stock stability, and enhanced recruitment through protection of the spawning stock are unlikely to succeed (except fortuitously) for herring populations such as those in Fortune Bay due to the dominant controlling influence of environmental variability. For such herring stocks the most appropriate long-term management strategy that could be supported on biological grounds would be a minimum size limit established at or above the length of 50% maturity.
Optimal Thinning of a Year-Class with Density-Dependent Growth
Authors: Hannesson Rögnvaldur
Published: April 2011

I consider the impact of density-dependent growth on the optimal harvesting of a year-class of fish. In general, density dependence makes "thinning" of the year-class a desirable strategy. Moderate density dependence implies that thinning should be gradual, even in the case of zero harvesting costs where the optimal harvesting strategy would otherwise be instantaneous harvesting. Strong density dependence calls for an immediate thinning at an early date, in the case of zero harvesting costs.
Capture–Recapture Experiment with Fly-Caught Brown (Salmo trutta) and Rainbow Trout (S. gairdneri)
Authors: Favro L. D. , Kuo P. K. , McDonald J. F.
Published: April 2011

A data base on angler-captured brown (Salmo trutta) and rainbow trout (S. gairdneri) in the Au Sable River of Michigan is analyzed and compared with electrofishing data. The angling recapture frequency for brown trout increases rapidly with increasing length, while the recapture frequency for rainbow trout is independent of length. Anglers caught a greater number of fish over 33 cm long than did the electrofishers in the same water. The anglers and the electrofishers appear to have captured fish from different subpopulations; therefore, conclusions based on data obtained by one capture method may not be applicable to the other.
Genetic Variation and Population Structure of Pacific Ocean Perch (Sebastes alutus)
Authors: Seeb Lisa Wishard , Gunderson Donald R.
Published: April 2011

We conducted an allozyme analysis of 27 collections representing over 1500 individuals of Pacific ocean perch (Sebastes alutus). Data were gathered from 25 presumptive loci of which 20% were polymorphic. Average observed heterozygosity was 0.069. Samples originated from throughout the commercially important range of the species from the Washington coast to the Bering Sea. Pacific ocean perch are highly similar throughout the range, with only a slight amount of population differentiation (FST = 0.023). However, a cline of gene frequencies within the Gulf of Alaska exists at Ada2, and there are significant frequency differences between the extremes of the range for several additional loci. There is no evidence of an interruption of gene flow between the western Gulf of Alaska and the Bering Sea. Stock delineations based on age structure, age–length relationships, and ages at maturity were not supported by the allozyme data and are either influenced by nongenetic environmental factors or are under a selective regime not measured by allozyme analyses.
Resident and Dispersal Behavior of Adult Sablefish (Anaplopoma fimbria) in the Slope Waters off Canada's West Coast
Authors: Beamish R. J. , McFarlane C. A.
Published: April 2011

A total of 72 735 adult sablefish (Anaplopoma fimbria) were tagged and released off the west coast of Canada from 1977 to 1982. As of December 31, 1985, 11 212 (15%) have been recaptured or 16 539 (23%) when recaptures were standardized for differences in recovery effort and unreported recaptures. Off Vancouver Island, relatively few sablefish moved more than 200 km. More movement occurred in Queen Charlotte Sound and off the Queen Charlotte Islands. Thirteen percent of recaptures were made in the United States zone and 96% of these were made in waters off Alaska. Movement was not related to length, age, or sex of adult fish. There was also no relationship between time at liberty and distance travelled; however, there was a trend to move out of the release area with time at liberty. In general, most adults remained within the release area. This resident behavior could result in overfishing because recruitment is dependent on occasional strong year-classes rather than movement from other areas.
Dynamics of Lake Michigan Plankton: A Model Evaluation of Nutrient Loading, Competition, and Predation
Authors: Scavia Donald , Lang Gregory A. , Kitchell James F.
Published: April 2011

Lake Michigan's offshore ecosystem has been altered dramatically during the past decade. Summer zooplankton dominance has changed from calanoid copepods to Daphnia and the substantial contribution of filamentous blue-green algae to summer phytoplankton has been replaced by phytoflagellates. These changes occurred concurrently with reduced P load, P concentration, and abundance of the dominant zooplanktivore, the alewife (Alosa pseudoharengus). In this analysis we pose alternative hypotheses of nutrient loading and species interactions as determinants of zooplankton and phytoplankton species composition in the summer epilimnion. We evaluate these hypotheses with a food web model that was calibrated to measurements of the 1980s Lake Michigan plankton composition and algal production, sedimentation, and growth rates and literature estimates of zooplankton secondary production and nutrient excretion. The model simulates the influence of gradients of both P load and alewife abundance on predation–competition interactions. We conclude that summer plankton composition in Lake Michigan is controlled largely by predation. The model further predicts a return to a plankton community similar to that of the 1970s under a scenario of increasing invertebrate predation by a new zooplankton species for Lake Michigan, Bythotrephes cederstroemi.
Incubation of Eggs of Atlantic Salmon (Salmo Salar) from Different Norwegian Streams at Temperatures below 1 °C
Authors: Wallace Jeff C. , Heggberget Tor G.
Published: April 2011

Atlantic salmon (Salmo salar) eggs obtained from fish from five widely separated localities were incubated from fertilization until hatching at mean temperatures of 1.0 and 0.17 °C. The results indicate that an existing model used to predict time of hatching in Atlantic salmon at temperatures greater than 2 °C can also be applied for lower temperatures. The eggs hatched 250–260 d after fertilization at mean temperatures of 0.15–0.17 °C (38–44 day-degrees) and after 206–221 d at temperatures of 0.97–1.03 °C (205–214 day-degrees). There was no evidence of stock adaptation or of within stock adaptation to temperature at any of the different localities during the period from fertilization to hatching.
Ecological Significance of Differences in Frequency of White Fin Margins Among Four Brown Trout (Salmo trutta) Populations
Authors: Taugbøl Trend , Skurdal Jostein , Andersen Ragnvald
Published: April 2011

The frequency of distinct white fin margins was investigated in four brown trout (Salmo trutta) populations, living in the small stream Austadbekken (anadromous and stream resident) and in Lake Selura (lake and stream spawners). The frequency varied within and among populations. White margins were most common among parr and mature residents from Austadbekken. Sea trout had very low frequencies compared with parr and mature residents from the same population. Among stream spawners from Lake Selura (which stay the first 0–2 yr in the stream), white margins were less frequent than in Austadbekken; lake spawners (which spend their entire life in the lake) had even fewer. While a previous author stated that white fin margins were under genetic control, our observations indicate that the environment can affect the coloration. We hypothesize that white fin margins play a role in territorial behavior and are developed strongly where territorial behavior is pronounced, i.e. in stream- and river-dwelling trout. There may be a selective pressure, favoring easily seen signals showing that a territory is occupied so that energy-demanding fights can be avoided. In open sea and estuaries where predators are frequent, conspicuous fin margins may be a disadvantage due to greater predation risks.
Poststocking Movements of Large Coho Salmon (Oncorhynchus kisutch) Fingerlings Introduced in February into a Small Coastal stream
Authors: Irvine J. R.
Published: April 2011

Juvenile coho salmon (Oncorhynchus kisutch), introduced into alternating 100-m sections of the lower kilometre of a steep-gradient stream in British Columbia, dispersed rapidly along the stream. After several days, fish originating from downstream of unstocked sections were almost as numerous in the unstocked sections as fish originating from upstream. The largest coho [Formula: see text], many of which had undergone smoltification, left the stream almost immediately after stocking. Six weeks after stocking, virtually no coho remained in the stream. Freshets apparently were responsible for displacing many of the fish out of the system.
Retinal Structure of Sympatric and Allopatric Populations of Cutthroat Trout (Salmo clarki clarki) and Dolly Varden Char (Salvelinus malma) in Relation to their Spatial Distribution
Authors: Henderson M. A. , Northcote T. G.
Published: April 2011

Retinal structures of cutthroat trout (Salmo clarki clarki) and Dolly Varden char (Salvelinus malma) were compared to determine if these features were consistent with the different light regimes in which the species live, depending on their sympatry or allopatry in lakes. Cone cell density in sympatric trout was over twice that of sympatric char and rod cell density was slightly less. The cross-sectional size of cone cells in sympatric trout was approximately 30% less than in sympatric char. The ratios of photoreceptor cells to ganglion cells in sympatric trout and char retinas were approximately 40:1 and 80:1, respectively. There were no differences between sympatric and allopatric trout with respect to these structural features. Estimates of cone cell density, cone size, and number of photoreceptor cells per ganglion cell for allopatric char were significantly different and intermediate between those for sympatric trout and char. All four populations had similar cone cell mosaics with four paired cones surrounding each single cone. Results are considered in relation to differences in vertical distribution and feeding of sympatric and allopatric populations in three study lakes.
Activity, Respiration, and Excretion of Ammonia by Atlantic Salmon (Salmo salar) Smolt and Postsmolt
Authors: Wiggs A. J. , Henderson E. B. , Saunders R. L. , Kutty M. N.
Published: April 2011

Spontaneous activity, oxygen consumption, and excretion of ammonia by juvenile Atlantic salmon (Salmo salar) were measured over 17 wk as the appearance of the fish changed from early smolt to smolt and then postsmolt. A substantial change in routine oxygen consumption from 66 to 148 mL∙kg−1∙h−1 was primarily correlated with the increase in activity. An initial increase in ammonia excretion from about 5 to about 14 mL∙kg−1∙h−1 was largely correlated with the decline in condition factor from 0.99 to 0.79 suggesting that increased metabolic needs caused by the increased activity were not being met by the amount of food ingested. This is supported by the secondary increase in condition factor (C.F. = 0.93) and decrease in ammonia excretion (to about 7 mg∙kg−1∙h−1) that occurred after the meal size was increased.
Adaptive Changes in Hematologic and Plasma Chemical Constituents in Captive Beluga Whales, Delphinapterus leucas
Authors: St. Aubin D. J. , Geraci J. R.
Published: April 2011

Forty-two beluga whales, Delphinapterus leucas, were captured in the Seal and Churchill River estuaries in western Hudson Bay during July, 1985 and 1987. Blood samples were drawn from each whale, and analyzed for cellular elements, electrolytes, metabolites, enzymes, proteins, and adrenocortical hormones. Most of the whales were released immediately after sampling; six were maintained in holding facilities for 10 k during 1985. Blood samples drawn during the early stages of acclimation to captivity, and at irregular intervals thereafter, revealed the variety of metabolic adjustments that accompanied the transition to captivity. The stress and exertion of capture resulted in increased levels of aldosterone, Cortisol, glucose, iron, potassium, and the enzymes creatine kinase, aspartate aminotransferase, alanine aminotransferase, and γ-glutamyltranspeptidase. Acute changes in leucocytes included lymphopenia, eosinopenia, and mild neutrophilia. Most of these indices normalized within the first week in captivity. Progressive changes were noted in triglycerides and creatinine, reflecting the whales' altered diet and caloric intake. A steady decline in red cell mass was indicative of reduced demands on oxygen carrying capacity, and provided a clue to the significance of low hematocrits reported for whales sampled after several weeks in shallow estuaries.