bluuebunny/crossref_metadata_2025 huggingface dataset:
Density Estimates of Mysis relicta in Lake Michigan
Authors: Grossnickle Nevin E. , Morgan Mark D.
Published: April 2011

Density estimates of Mysis relicta based on night vertical net tows at stations of 30–50 m in Lake Michigan were about an order of magnitude larger than previous estimates based on sled tows. Significantly greater density estimates were obtained in night vertical net tows than those collected before sunset at these shallow stations. However, density estimates based on sled tows during daylight were not significantly different from those based on night vertical net tows at a 115-m station in Lake Michigan. At this deep station, a substantially larger percentage of late instar mysids was collected in sled tows than in night vertical net tows. Key words: Mysis relicta, Lake Michigan, density estimates, vertical net tows, epibenthic sled tows
Development of Economic Theory on Fisheries Regulation
Authors: Scott Anthony
Published: April 2011

A survey of the economic literature of fisheries regulation shows that little of analytical value for the comparison of alternative regulatory techniques has emerged. The suggestion that the general literature on regulation, and on public choice, has something to contribute to the understanding of alternative regimes produces eight criteria. These are applied to the choice between two systems of restricting entry: a tax, and quotas. The transactions costs of the two systems are also investigated. The hypothesis is formed that the eight criteria, plus expected transactions costs, give the edge to a quota system; but this is only illustrative of the approach. Key words: regulation, management, costs, quotas, taxes, revenue, licensing
Regulating Access in Canada's Inland Fisheries
Authors: Cauvin D. M.
Published: April 2011

Uncontrolled access in Canada's inland fisheries has served neither the resource manager's interest in protecting fish stocks nor the economist's interest in promoting the most efficient use of all factors of production, including fisheries resources. Economically accessible fisheries have generally attracted more labor and capital than is required to harvest the productive potential of fisheries resources. As a result, costs of production are high in relation to the value of production and profit margins have been eroded. Of equal importance, a return from the resource in the form of a resource rent has been foregone. Access control and a price system represent management options to control excess fishing effort, promote economic efficiency in the deployment of private and public resources, and promote fiscal accountability in government. Key words: economic efficiency, resource rent, fiscal accountability
Survey of Some Canadian Lakes for the Presence of Ultrastructurally Discrete Particles in the Colloidal Size Range
Authors: Massalski A. , Leppard Gary G.
Published: April 2011

Water samples from nine Canadian lakes were centrifuged and the pellets were analyzed by transmission electron microscopy. The pellets included small organisms, organic colloids, and clay particles. In almost all the samples, colloids were the major component revealed following thin-section analysis. When viewed at high magnification, much of each pellet consisted of morphologically discrete particles, some of which were readily categorized. Electron-opaque fibrils of colloidal size were frequently encountered (1) at different depths, (2) as a coating on the surface of algae and bacteria, (3) overlaying the sediments, (4) as an apparent adhesive between a variety of particles, and (5) as a component of froth at the water–air interface. They were common at all times and in lakes of various trophic levels and sizes. Key words: water, colloids, fibrils, lakes, electron microscopy
Tidal Energy and Sublittoral Macrobenthic Animals in Estuaries
Authors: Wildish D. J. , Kristmanson D. D.
Published: April 2011

A quantitative hypothesis is presented that current velocity and roughness at the sediment–water interface control the numbers, biomass, and growth of suspension-feeding macrobenthic animals. The controls are the effect of tidal currents on turbulent mass transfer of food to suspension-feeding animals and direct inhibition of growth and settlement by currents in excess of 12–30 cm/s. The rate of turbulent supply of ATP associated with seston is proposed as a practical way of determining growth potentials of suspension-feeding macrobenthos at current velocities less than 30 cm/s. Key words: sublittoral macrobenthos, tidal velocity, potential population growth, Bay of Fundy estuaries
A Rapid Method for the Estimation of, and Some Factors Affecting, Copepod Production Rates in the Burlington Canal
Authors: Borgmann U. , Loveridge C. , Cove R.
Published: April 2011

A method is described for estimating in situ biomass production rates of copepods. The youngest naupliar stages are isolated by filtration through two different size sieves, and growth is measured after laboratory incubation by filtering through a series of eight filters. Since the filters appear to be relatively efficient at separating copepods of different sizes, copepod size can be estimated from the pore size of the filters alone, resulting in a very rapid procedure for calculating biomass. This method allows experimental manipulation of environmental conditions, permitting for example, an estimation of the relative importance of temperature and food abundance in the seasonal growth cycles of these organisms. It was concluded that, in the Burlington Canal, temperature exerts a greater influence on growth rate than does food concentration, although adaptation to food levels may be expressed indirectly, due to a similarity in the seasonal cycles for temperature and food. The method is also useful in predicting the potential impact of toxic substances on copepod production rates under natural conditions. Key words: copepods, zooplankton, biomass production, temperature, food concentration
Difference in Taste Between the Right and Left Sides of Tainted Fish
Authors: Liem A. J. , Naish V. A.
Published: April 2011

More tainting was found on the left than on the right side of rainbow trout (Salmo gairdneri) that were exposed to a kraft pulp mill "foul condensate." This sidedness was deduced from the results of the triangle taste test used to detect differences between exposed and control fish, and was observed when the tainting was moderate, in the range of effluent concentrations of 0.015–0.046% by volume. Key words: fish, tainting, taste, rainbow trout.
Assimilation Efficiency of Dietary Methylmercury by Northern Pike (Esox lucius)
Authors: Phillips G. R. , Gregory R. W.
Published: April 2011

Northern pike (Esox lucius) retained an average of 19% (range 6–31%) of the methylmercury which they ingested during consumption of young-of-the-year carp (Cyprinus carpio) collected from a pond; carp accumulated methylmercury naturally while in the pond. The total amount of mercury in pike increased with time (up to 42 d) but concentration in the tissue decreased due to growth dilution; duration of ingestion did not influence efficiency of methylmercury assimilation. This value (19%) is considerably lower than most efficiencies reported in the literature, demonstrating that methylmercury in this forage fish is less readily available to a predator fish than previous studies implied. Key words: bioaccumulation, mercury compounds, predators, Esocidae
Salmon and Trout Farming in Norway.
Authors: Ayles G. Burton
Published: April 2011

not available
Pathogenesis of Experimental Vibriosis in Larval American Oysters, Crassostrea virginica
Authors: Elston Ralph , Leibovitz Louis
Published: April 2011

Larval oysters were experimentally infected with isolates of pure cultures of marine Vibrio sp. These animals were studied live, histologically, with the immunofluorescent test and with electron microscopy. All inoculated groups, but no control groups, demonstrated decreased growth and/or high mortality.One bacterial isolate attached preferentially to larval shell and destroyed mantle tissue as it grew along the internal surface of the shell. Phagocytes consumed invading bacterial cells but were ultimately overwhelmed by the infection.The second bacterial isolate caused velar damage in young larvae that remained active. In these larvae, the velar cells became detached or internally disorganized and lost their rectractor muscle insertions. In more advanced larvae, detachment of absorptive cells of the digestive gland was the earliest change observed and seemed to result from attachment of bacterial antigens to the cell surface. In both younger and more advanced larvae, food cycling and nutrient utilization were disrupted early in the disease process. The older larvae showed a general atrophy.Clinical signs such as mantle cell detachment could be detected early in the disease. Other clinical observations and the immunofluorescent test were also useful in the early diagnosis of vibriosis in larval oysters.Key words: vibriosis, larval oysters, Crassostrea virginica, histology, electron microscopy, ultrastructure, immunofluorescence, oyster hatcheryDes larves d'huîtres ont été infectées expérimentalement par des isolats de cultures pures de Vibrio sp. marins. Ces animaux furent étudiés en vie, histologiquement, à l'aide du test d'immunofluorescence et enfin au microscope électronique. Tous les groupes inoculés, mais non les groupes témoins, accusent un déclin de croissance et/ou une mortalité élevée.
Bioenergetics of Stock and Recruitment
Authors: Ware D. M.
Published: April 2011

A new concept of recruitment is derived from bioenergetic considerations of life history phenomena. The proposed mechanism has two components, a stock-dependent process where individual reproductive effort is a decreasing function of the abundance of the mature stock, and a density-dependent mortality process which operates during the prerecruit stage. A generalized equation describing these processes yields a family of recruitment curves which vary from being asymptotic to dome-shaped, depending on the parameter values. The theory suggests that species like Atlantic herring (Clupea harengus harengus) which tend to have small density-dependent growth coefficients and which allocate most of their surplus energy to reproduction should have a small terminal body size, a high length at maturity to L∞ ratio, and a nearly asymptotic recruitment curve. By contrast, gadoids follow a different life history strategy and therefore should have a higher L∞ and more convex recruitment function. These consequences are shown to be in accord with observed differences in L∞ and with the graded series of recruitment curves found for a wide range of marine fish stocks. From a more general viewpoint, analysis of the energy dynamics of natural populations suggests that (1) there is a real — as opposed to inferred — limit to growth, L∞, which in many species is probably determined by their reproductive effort; (2) the increase in surplus energy with body size can be linked to the theory of optimal foraging; and (3) the intensity of density-dependent growth, which influences the shape of the recruitment curve, is an increasing function of the generation time of the prey organisms of different species. Thus gadoids tend to have dome-shaped reproduction curves because they feed on slow-maturing prey, which can be overcropped by large year-classes.Key words: stock and recruitment, bioenergetics, optimal foraging, growth, reproduction, life history strategies
Hemoglobin Levels and Red Cell Ionic Composition in Goldfish (Carassius auratus) Exposed to Constant and Diurnally Cycling Temperatures
Authors: Koss Ted F. , Houston Arthur H.
Published: April 2011

Hematological response in goldfish (Carassius auratus) held at constant temperature (20, 25, 30 °C) was compared with that of animals exposed to a diurnal temperature cycle (25 ± 5 °C), with particular reference to overall oxygen carrying capacity and cellular electrolytes influencing haemoglobin–oxygen affinity. All groups were sampled at 03:00, 09:00, 15:00, and 21:00. Hemoglobin and hematocrit were determined, as were plasma and packed red cell levels of water, sodium, potassium, magnesium, calcium, and chloride. The latter were used to estimate mean cellular ion concentrations. Temperature treatment influenced response. Under constant temperature conditions hemoglobin levels tended to increase at higher temperatures. This was associated with compositional changes which would be expected to reduce affinity and facilitate oxygen release. By contrast, under cycling temperature conditions hemoglobin levels were elevated whereas erythrocytic electrolyte concentrations tended to be stable. Observations are discussed in terms of their bearing on the interpretation of studies on the acclimatory process.Key words: goldfish, Carassius auratus; blood chemistry, temperature, hemoglobin, O2-carrying capacity
Short-term Forecasting in Marine Fish Stocks
Authors: Stocker Max , Hilborn Ray
Published: April 2011

The predictive power of stock production models and simple time series methods was considered for five marine fish stocks. The distinction between model fitting and forecasting future short-term catch is discussed, as is the difference between techniques to forecast short-term yield, and techniques to calculate long-term management practice. Fox's procedure for fitting Pella and Tomlinson's stock production model, Schnute's method for fitting Schaefer's model, and Gulland's method are all considered. We found that all methods except that of Gulland work well for some stocks, and the relative performance of the methods depends upon the exploitation history of the stock. In several instances one of the best forecasts of next year's catch per unit effort (CPUE) was the previous year's CPUE, emphasizing the fact that a good forecasting technique may have no utility in determining management policies.Key words: production models, catch and effort, fisheries, management, catch forecasting, time series
Extrathyroidal Effects of Low Concentrations of Thiourea on Rainbow Trout, Salmo gairdneri
Authors: Eales J. G.
Published: April 2011

Chronic exposure of fed immature rainbow trout (Salmo gairdneri) to a low ambient thiourea (TU) concentration did not depress circulating levels of T4 (thyroxine) or triiodothyronine, T4 degradation rate, or T4 deiodination rate indicating no significant T4 influence on thyroidal hormone output. However, TU increased the hematocrit and decreased distribution spaces for iodide and T4, indicating direct sensitivity of extrathyroidal processes to TU.Key words: thiourea, thyroxine, hematocrit, iodide metabolism, rainbow trout
Sterilization of Sea Lampreys (Petromyzon marinus) by Immersion in an Aqueous Solution of Bisazir
Authors: Hanson Lee H.
Published: April 2011

Groups of sea lamprey (Petromyzon marinus) eggs fertilized by males previously immersed in an aqueous solution of p,p-bis(1-aziridinyl)-N-methylphosphinothioic amide (bisazir) at concentrations of 10–100 mg/L produced fewer normal, live prolarvae after 15–17 d of incubation than did groups of eggs fertilized by normal males. Mortality of embryos or prolarvae was nearly 100% in groups of eggs fertilized by males that had been immersed in a 50 mg/L solution of bisazir for 4 h or in a 100 mg/L solution for 2 h. The immersion technique appears to be an efficient method of sterilizing large numbers of male sea lampreys for use in a proposed sterile-male-release program.Key words: sea lamprey, Petromyzon marinus; pest control, fish control, sterile-male technique, sterilization, chemosterilants, bisazir, Great Lakes
Species Replacement in a Reservoir Fish Community: Silverside Feeding Mechanics and Competition
Authors: McComas Steven R. , Drenner Ray W.
Published: April 2011

The brook silverside (Labidesthes sicculus) was the only atherinid species found in Lake Texorna, Oklahoma, from 1944 to 1953. Inland silversides (Menidia beryllina) were first collected in Lake Texoma in 1953 and had completely replaced Labidesthes by 1955. We conducted comparative studies of feeding mechanics and feeding efficiencies of Labidesthes and Menidia to see if there was a competitive differential between species that could have been a factor in the replacement of Labidesthes by Menidia. Menidia has a protrusible and tube-shaped mouth that is more successful capturing evasive copepod prey than the v-notched mouth of Labidesthes. While both species have similar feeding rates for slow-swimming daphnids, Menidia has higher feeding rates than Labidesthes for cyclopoid and calanoid copepods. Menidia's use of copepod prey is a competitive advantage over Labidesthes in laboratory competition experiments. We hypothesize the same advantage was an important factor in displacing Labidesthes from Lake Texoma.Key words: planktivory, Labidesthes sicculus, Menidia beryllina, Lake Texoma
Comparison of Two Methods of Combining Catch-Per-Unit-Effort Data from Geographic Regions
Authors: Quinn II Terrance J. , Hoag Stephen H. , Southward G. Morris
Published: April 2011

We examined two methods of combining catch-and-effort data from small geographic regions into large regulatory areas to estimate catch-per-unit-effort (CPUE): (1) weighting regional CPUE by bottom area occupied by the population; (2) weighting by fishing effort. Variance estimates and other statistical properties are presented for CPUE estimates by region and for the two methods, for the type of fishery where total catch is known. The CPUE estimator from area-weighting is approximately unbiased as an index of population density; the CPUE estimator from effort-weighting is biased but less variable than the former. Conditions of similarity are derived for estimators from the two methods to be identical, or, less restrictively, to show the same trend over time. In general, the area-weighted method is preferred, if sufficient samples are taken from all pertinent regions in the regulatory area. However, the effort-weighted method may be used with a gain in precision and no substantial bias, if there are no substantial changes in relative CPUE and effort among regions, or if relative CPUE and effort are inversely related. The two methods applied to catch and effort data for Pacific halibut (Hippoglossus stenolepis) and to produce highly similar CPUE estimates over time, despite large relative changes in both CPUE and effort among regions. The reasons for the similarity are traced back to conditions in the fishery.Key words: catch-per-unit-effort, combining data, sampling commercial fisheries, variance estimation, comparison of methods
Estimating Prey Preference by Predators: Uses of Various Indices, and a Proposal of Another Based on χ2
Authors: Pearre Jr. Sifford
Published: April 2011

A really useful prey-selection index should be statistically testable. A 2 × 2 contingency table formulation provides a simple way to test the significance of any degree of selection at any sample size. An index ranging from −1 to +1, and zero-valued for no selection, can be simply derived from the chi-square formulation. Some conflicting usages in biological statistics texts are discussed, as well as the usefulness and limitations of other commonly used indices.Key words: selection, index, chi-square, exact test, prey
Blood Protozoa as an Aid for Separating Stocks of Greenland Halibut, Reinhardtius hippoglossoides, in the Northwestern Atlantic
Authors: Khan R. A. , Dawe M. , Bowering R. , Misra R. K.
Published: April 2011

Samples of subadult Greenland halibut, Reinhardtius hippoglossoides, from several northwest Atlantic locations, the Gulf of St. Lawrence, and Fortune Bay, an inlet on the south coast of Newfoundland, were examined for the prevalence of two blood protozoa. Because prevalence of infection varied widely, the data were analyzed using the general least squares analysis of fitting constants on logit values. Trypanosome and piroplasm infections in samples from Davis Strait, NAFO divisions 2G–2H and div. 3L, were mostly similar, but differed significantly from div. 2J–3K. Trypanosome infections in samples from the northwest Atlantic locations were significantly higher than in the Gulf of St. Lawrence and Fortune Bay. Piroplasm infections were significantly higher in samples from Fortune Bay than in the Gulf of St. Lawrence. The results suggest that Greenland halibut from Davis Strait, div. 2G–2H and div. 3L, are composed of one stock complex, while fish from div. 2J–3K represent an isolated group or most probably a cline between areas. Greenland halibut from the Gulf of St. Lawrence and Fortune Bay appear to represent distinct stocks.Key words: blood protozoa, trypanosome, piroplasm, Greenland halibut, stock separation, northwestern Atlantic
Problems of Species Identity in the Lake Ontario Seulpins Cottus bairdi and C. cognatus
Authors: Godkin C. M. , Christie W. J. , McAllister D. E.
Published: April 2011

The sculpins Cottus bairdi and C. cognatus are difficult to distinguish in Lake Ontario because intermediate specimens are present and because C. bairdi in the lake is more variable than C. bairdi from the surrounding drainage basin. Our evidence indicates that intermediates are probably the products of hybridization between C. bairdi and C. cognatus. The greater variability of C. bairdi in Lake Ontario may be due to subspecies differences, but we suggest that backcrossing of C. bairdi with hybrids would also account for this phenomenon.Key words: sculpin, Lake Ontario, taxonomy, hybridization
Sublethal Toxicity of Cyanide to Rainbow Trout (Salmo gairdneri) at Different Temperatures
Authors: Kovacs Tibor G. , Leduc Gérard
Published: April 2011

At sublethal levels cyanide was more potent at lower temperatures. This was verified in 20-d laboratory growth experiments carried out on juvenile rainbow trout (Salmo gairdneri) in flow-through aquaria maintained at 6, 12, and 18 °C. Cyanide concentrations in the range of 0.005–0.045 mg∙L−1 HCN significantly reduced growth rates (wet weight, dry weight, and fat), the effective concentrations increasing with temperature. Some adaptation to cyanide seemed to occur as manifested by faster growth rates. Liver glycogen and lactic acid monitored for 20 d in rainbow trout exposed to 0.015 mg∙L−1 HCN showed an initial shift towards glycolysis, followed by a return to aerobic respiration. This response, however, varied with temperatures. Previous exposure to cyanide markedly reduced swimming performance of the fish tested at their acclimation temperatures, but in the absence of the toxicant. The effect also increased with decreasing temperatures.Key words: cyanide, sublethal toxicity, rainbow trout, temperature, growth, swimming, liver metabolites
Error Bounds for Estimates of Entrained Ichthyoplankton
Authors: Madenjian C. P. , Jude D. J.
Published: April 2011

Entrainment of fish larvae and eggs was monitored at the J. H. Campbell Plant, eastern Lake Michigan, from 1977 to 1979. A procedure for calculating error bounds for estimated number of fish larvae (or eggs) entrained by the plant for each year of operation, assuming independence among observations, was outlined. A new method for calculating these bounds was devised by adjusting the variance for its non-independent component, using time series analysis. Serial correlation in the data was accounted for by modeling the sequence of entrainment data for a year as a time series. For many taxa of fish larvae the entrainment observations were determined to be independent and no adjustment was necessary. The width of the adjusted error-bound intervals ranged from 4.8 to 87.9% greater than unadjusted ones for those taxa for which adjustment was required, thus assuming independence among observations could result in serious underestimation of the error-bound interval.Key words: error bounds, variance, entrainment, Lake Michigan, serial correlation, time series analysis
Total Dissolved Solids as a Predictor of Lake Biomass and Productivity
Authors: Prepas E. E.
Published: April 2011

Total dissolved solids (TDS) and chlorophyll a were not related in 25 lakes which were all off the Precambrian Shield. Both on-shield and off-shield lakes were included in the previous reports which showed a significant relationship between TDS and productivity. When data from on-shield and off-shield lakes were analyzed separately, there was no significant positive relationship between TDS and lake biomass or productivity. It was also shown that mean depth ([Formula: see text]) was as good a predictor of fish production as the TDS: [Formula: see text] ratio, the morphoedaphic index.Key words: TDS, biomass, productivity, morphoedaphic index, chlorophyll a, lakes
Particle-Size-Conversion Efficiency and Contaminant Concentrations in Lake Ontario Biota
Authors: Borgmann Uwe , Whittle D. M.
Published: April 2011

The particle-size-conversion efficiency (log food consumption/production divided by log predator prey size ratio) is shown to be directly related to the relationship between the concentration of persistent contaminants accumulated primarily through the food chain and body size for organisms in pelagic ecosystems. The difference between particle-size-conversion efficiency for biomass and that for the contaminant gives the slope of the relationship between log contaminant concentration and log body size. This provides a useful theoretical framework for analyzing contaminant concentrations in aquatic biota without the need for specifying trophic level but still incorporating the idea of food chain accumulation. Concentrations of PCB, DDT, and mercury were examined in aquatic organisms from Lake Ontario, ranging in size from zooplankton to large salmonids (a 108 -fold range in dry weight). The slope of the double log plot of concentration versus weight varied from 0.20 to 0.22 for PCB and DDT and was approximately equal to 0.13 for mercury. This indicates that mercury is accumulated less efficiently through the food chain than PCB or DDT. After correcting for incomplete uptake and retention of the contaminant, an estimate of particle-size-conversion efficiency for biomass of about 0.26 was obtained, which agrees reasonably well with previous estimates obtained from growth efficiency experiments and analysis of particle-size spectra. These calculations indicate that potential fish production in Lake Ontario is ~ 120-fold lower than zooplankton production (for fish averaging 108-fold larger in body size as compared to zooplankton).Key words: particle-size-conversion efficiency, PCB, DDT, mercury, zooplankton production, fish production
Identification of Marine Fish Eggs: A Biochemical Genetics Approach
Authors: Mork Jarle , Solemdal Per , Sundnes Gunnar
Published: April 2011

We studied inter- and intra-specific variation at LDH (lactate dehydrogenase; EC 1.1.1.27) loci in 11 gadoid and 6 flatfish species regularly occurring in Norwegian coastal waters by means of isoelectric focusing and histochemical staining techniques. No two species showed identical locus A (white skeletal muscle predominating) zymograms. Polymorphism at LDH A was observed in haddock (Gadus aeglefinus), coalfish (G. virens), Norway pout (G. esmarkii), four-bearded rockling (Onos cimbrius), and dab (Limanda limanda). The allelic nature of observed LDH variants was confirmed by controlled crossings in cod (G. morhua, locus B), Norway pout (locus A), and haddock (locus A). Analyses of artificially fertilized eggs (in four species) and prenatal eggs from ripening ovaries (in 10 species) revealed a general predominance of locus A products. The maternal LDH A activity present in newly released eggs was overtaken by embryo-synthesized enzyme 1–2 d after fertilization. No unique embryonic LDH loci were observed. LDH A zymograms thus appear to be useful as a practically diagnostic tool for the identification of the pelagic fish eggs usually found in these waters. The identification method, applied to samples of pelagic eggs collected at the coast of northern Norway during March–May 1981 and 1982, showed that in a total of ~ 1500 eggs, the following species were represented: cod, Norway pout, haddock, coalfish, dab, plaice (Pleuronectes platessa), and long rough dab (Hippo-glossoides plates-soides). The species composition in these egg samples varied considerably with sampling location and sampling depth.Key words: fish egg identification, biochemical genetics, tissue enzymes, gadoids, flatfishes
Isolation of Colloidal Fibrils from Lake Water by Physical Separation Techniques
Authors: Burnison B. Kent , Leppard Gary G.
Published: April 2011

A colloid fraction, highly enriched for organic fibrils, can be isolated routinely by physical means. The physical isolation scheme used here provides gram quantities of un-denatured samples in a short time from the epilimnion of a small mesotrophic lake. The total scheme is described in detail and is accompanied by an assessment of yield and contamination at each individual step using a transmission electron microscope as a monitor. The potential importance of organic fibrils is emphasized by a 1980 summer measure showing a fibril fraction to contain three times more carbon than the conventional particulate organic carbon fraction (POC) and 33% of the total dissolved organic carbon (DOC).Key words: colloids, hollow-fiber ultrafiltration, dissolved organic carbon
Energy Metabolism in a Rapidly Developing Marine Fish Egg, the Red Drum (Sciaenops ocellata)
Authors: Vetter Russell D. , Hodson Robert E. , Arnold Connie
Published: April 2011

Rates of utilization of different lipid classes, glycogen, protein, and adenine nucleotides in the eggs of red drum (Sciaenops ocellata) were measured concurrently throughout embryonic development. Red drum eggs are small, pelagic, and very rapidly developing, going from fertilization to hatching in as little as 19 h at natural spawning temperatures. Wax esters comprised about 50% of the neutral lipid reserve along with triglyceride. Lipid was quantitatively the most important energy reserve supplying virtually all of the catabolic demand. Total lipid content decreased 30% from 23.6 to 16.6 mg/g during development. Glycogen decreased 53% from 0.279 to 0.103 mg/g. Protein did not contribute to catabolism. Total adenylates, primarily ATP, decreased from 564 to 271 nmol/g. Adenylate energy charge decreased from 0.87 to 0.58. Glycogen and lipid were used concurrently rather than sequentially during development. The rapid rate of development could be accounted for by simple thermal effects on metabolism rather than any unique biochemical adaptation. High concentrations of wax ester may be an adaptation for maintaining buoyancy at reduced salinities.
Precocious Male Atlantic Salmon Parr (Salmo salar) in Insular Newfoundland
Authors: Dalley E. L. , Andrews C. W. , Green J. M.
Published: April 2011

The incidence of sexual precocity in male Atlantic salmon parr (Salmo salar) was examined in selected rivers in insular Newfoundland from 1974 to 1977. The incidence was variable but generally high, particularly in eastern rivers. Examination of age-specific lengths revealed that the faster growing males became precocious but percent precocity for these varied among river systems. Precocity did not influence growth of parr in comparison to immatures up to the smolt stage. No difference was found in the condition (using gutted weights) of mature and immature parr. However, condition deteriorated in precocious fish compared to immature fish with smoltification. Parr sex ratios frequently differed significantly from 1:1. Possible reasons are discussed in terms of sex related distribution patterns and mortality of precocious parr. From smolt runs examined, it appears that too few precocious parr migrate as smolt to contribute to the grilse population. As a result of the high mortality, rivers with a high percentage of sexually precocious males tend to have a corresponding high percentage of adult females.
Nutrient Limitation in Two Arctic Lakes, Alaska
Authors: Mccoy George A.
Published: April 2011

Batch-culture algal bioassays of Selenastrum capricornutum were used to predict the limiting nutrient in two small arctic–tundra lakes in 1979. In 1980 bioassays were performed again, and fertilizer was added to the lakes to test the predictions made from the 1979 bioassay results. In 1980, after the addition of phosphorus fertilizer, phytoplankton standing crop increased ~10-fold. After the addition of nitrogen fertilizer, another 10-fold increase in phytoplankton growth was measured. Concurrently, maximum daytime dissolved oxygen increased from 100 to 150% saturation, and pH increased from 7.0 to about 9.2. Further additions of fertilizer in late August and early September 1980 caused no significant increase in primary production. If the nitrogen content of the lake water is increased but that of phosphorus is not, no increase in algal growth occurs. Growth increases with phosphorus additions, but the magnitude of this increase is determined by the available nitrogen. When additional nitrogen is supplied to the system, further increases in algal growth occur. When nitrogen and phosphorus are supplied in excess, physical factors such as light or temperature become limiting in the lakes.
Effects of Low Environmental pH on Smolting of Atlantic Salmon (Salmo salar)
Authors: Saunders Richard L. , Henderson Eugene B. , Harmon Paul R. , Johnston C. Edward , Eales J. Geoffrey
Published: April 2011

We reared Atlantic salmon (Salmo salar) in soft water (hardness 13 mg/L as CaCO3) at two pH levels, 6.4–6.7 and 4.2–4.7, from February to June, to assess the effect of low pH on survival, growth, and the smolting process under rising (4–8.5 °C) or relatively constant (9.5–10.5 °C) temperature. Survival was lower as a result of low pH (4.2–4.7) under both temperature regimes. Neither group exposed to low pH gained weight whereas both control groups gained weight during the experiment. Parr–smolt transformation, as indicated by salinity tolerance and gill Na+, K+ ATPase activity, was impaired as a result of low pH. The large (17–19 cm) parr used in this study were initially salinity tolerant and those at control pH (6.4–6.7) increased tolerance to 35‰ salinity between March and May; those in low pH became intolerant of high salinity. ATPase levels in salmon reared at low pH were significantly lower than those at normal pH levels under both temperature regimes. ATPase activity was significantly greater in fish reared at pH 6.4–6.7 with rising than with constant temperature. Plasma chloride and sodium levels were low in response to low pH, indicating impaired ionic regulation in freshwater. Plasma calcium levels were higher at low pH in both temperature regimes; higher levels were reached under constant temperature. Moisture content rose less sharply under low than under control pH in both temperature regimes. In the rising temperature regime, lipid levels reached similar, low levels under low and control pH conditions. Thyroid hormone (T3 and T4) levels gave no clear indication of effects of low pH on smolting. Smoltification did not proceed normally in our Atlantic salmon subjected to low pH levels.
Methylation of Arsenic by Freshwater Green Algae
Authors: Baker M. D. , Wong P. T. S. , Chau Y. K. , Mayfield C. I. , Inniss W. E.
Published: April 2011

Isolates from four genera of freshwater green algae were capable of methylating sodium arsenite in lake water and Bold's basal medium. Analysis of the liquid phase of the methylation flasks revealed the presence of methylarsonic acid, dimethylarsinic acid, and trimethylarsine oxide. Volatile arsine and methylarsines were not detected in the headspace gases presumably because of the inability of the algae to reduce completely the methylated–arsenic species. Although the algae varied with respect to their methylating abilities, the levels of methylated–arsenic compounds were always significantly higher when the algae were grown in lake water. This may have been due to the lower phosphate concentration in the lake water. We suggest that arsenic methylation by green algae constitutes an additional source for the formation and cycling of organo-arsenic compounds in freshwater ecosystems.
Relative Influences of Riverine and Macroalgal Phenolic Materials on UV Absorbance in Temperate Coastal Waters
Authors: Carlson David J. , Mayer Lawrence M.
Published: April 2011

Seasonal changes in profiles of both UV absorbance and phenolic material versus salinity were observed in some estuarine and coastal waters of the Gulf of Maine. Profiles of riverine UV-absorbent and phenolic materials were seasonally invariant, with slight losses from high molecular weight fractions during estuarine mixing. In estuaries containing significant populations of fucoid macroalgae, exudation by the macroalgae increased levels of these parameters by as much as threefold. These increases showed a strong seasonal pulsing, following water temperature. This pulsing was detectable in seasonal transects of adjacent shelf waters.
Distribution of Resting Cysts of Gonyaulax tamarensis var. excavata and Shellfish Toxicity
Authors: Thayer P. E. , Hurst J. W. , Lewis C. M. , Selvin R. , Yentsch C. M.
Published: April 2011

Our objective was to determine whether intertidal dinoflagellate resting cyst distributions might be useful for determining areas which should be closely monitored for toxins in shellfish. Gonyaulax tamarensis var. excavata cyst distributions in Gulf of Maine sediments were examined semiquantitatively each winter for a 5-yr period and compared with locations of shellfish toxicity. Although distribution patterns over broad geographical ranges may be a reflection of shellfish toxin rise, they do not predict timing of future shellfish intoxication at specific locations.
Movements of Coho Salmon (Oncorhynchus kisutch) Fingerlings in a Stream Following Marking with a Vital Stain
Authors: Mundie J. H. , Traber R. E.
Published: April 2011

For population estimates we used a vital stain on nine occasions throughout two winters to mark coho salmon (Oncorhynchus kisutch) fingerlings living at high density in a side-channel of a river. On recapture 2–3 d after staining the marked fish were fairly evenly distributed in the channel on one occasion only; on three occasions (at 5 °C or higher) they showed conspicuous upstream movements, and on five occasions (below 5 °C) downstream movements. Such changes in distribution should be taken into account in the estimation of population size.
Modeling Tidal Stress, Circulation, and Mixing in the Bristol Channel as a Prerequisite for Ecosystem Studies
Authors: Uncles R. J.
Published: April 2011

A depth-averaged hydrodynamical numerical model is used to evaluate tidal stresses, currents, and mixing in the Bristol Channel and Severn Estuary. Benthic macrofaunal associations and sediment bed types are shown to depend on the magnitude of the tidal stress, and the direction of sediment transport (as bed-load) in the central parts of the Channel is shown to be a consequence of ebb dominated stress. This asymmetry in the tidal stress is mainly caused by M4 currents, and computed M4 elevations and currents are compared with observed values at a number of stations. Residual flows and horizontal mixing are deduced from the hydrodynamical model, and used to construct transport relationships for an ecosystem model. Agreement between observed salinity over a number of years and that computed by the ecosystem model is generally good.Key words: Bristol Channel, hydrodynamical model, salinity model, tidal stress, M4 tides, sediment movement
Distribution and Behavior of Fine Sediment in the Severn Estuary and Inner Bristol Channel, U.K.
Authors: Kirby R. , Parker W. R.
Published: April 2011

During the 10 yr, 1970–80 a variety of field measurements using some new techniques have allowed the distribution of muddy sediment in the Severn Estuary and Inner Bristol Channel to be defined. Based on these measurements, a behavioral model has been adopted comprising mobile and stationary suspensions, and settled mud. The regional distribution of mobile suspensions shows a suspended solids front located along the main channel axis with the more turbid water on the southern, English, side. At maximum current velocities on spring tides, vertical suspended sediment profiles are homogeneous. As velocity decreases, a stepped structure develops due to settling, which is then remixed on the next accelerating semidiurnal tidal phase. Over the lunar timescale these steps become more stable, eventually settling to the bed. The steps are unrelated to salinity, temperature, grain-size, or mineralogy. On neap tides, layered, acoustically detectable stationary suspensions, which occasionally consolidate to form settled mud, develop from the mobile suspensions. An idealized "three-zone" model has been devised characterizing the structures developed in the mobile suspensions.Key words: Severn Estuary, vertical profiling, siltmeter, densimeter, suspended solids, fronts, stratification
The Northern Muddy Intertidal: Seasonal Factors Controlling Erosion and Deposition — A Review
Authors: Anderson Franz E.
Published: April 2011

This review summarizes the seasonal physical and biological processes which take place on and in the muddy intertidal zone during the year and affect the erosion or deposition of sediment. The main physical processes that are considered are the effects of ice, waves, sediment dewatering, rain, and mud and water temperatures. The biological processes include the growth of benthic diatoms, algal mats, and higher plants as well as the effects of bioturbation, pellet formation, biodeposition, and changes in the intertidal microrelief.In the early spring in northern temperate estuaries, ice break-up is the most significant factor affecting muddy intertidal sedimentation. The ice-roughened intertidal has not yet been affected significantly by either plant or animal activity, and is particularly susceptible to sediment resuspension by waves. During the summer, organic processes dominate the intertidal as organisms feed on, pelletize, and bioturbate the sediments. Plant growth, especially benthic diatoms and algal mats, may stabilize the sediment. The few storms during this season combined with lower rainfall insure that the muddy intertidal only rarely undergoes erosion. In fall, seasonal storms increase while both plant and animal activity begin to slow down. Lower rates of bioturbation make the muddy intertidal more resistant to erosion, but the intensity of the fall storms, and higher rainfall, cause significant sediment scouring. With the onset of winter, ice forms over and on the muddy intertidal, reducing resuspension and erosion. However, significant sediment erosion and transportation occurs during winter thaws, when temporary ice break up occurs. But the effect of ice "armoring" all but eliminates sediment resuspension by waves over the muddy intertidal for most of the coldest winter months.Key words: intertidal zone, erosion, deposition
Chemical Composition of Suspended Particles in an Estuarine Turbidity Maximum Zone
Authors: Loring D. H. , Rantala R. T. T. , Morris A. W. , Bale A. J. , Howland R. J. M.
Published: April 2011

The detrital and nondetrital elemental compositions of suspended particles in the Tamar Estuary, U.K., have been examined when the estuarine turbidity maximum was well developed and also when high river flow restricted the development of a turbidity maximum. Correlation matrices and 'r'-mode factor analyses were used to identify significant relationships within and between the variances in the fractionated particulate compositions and in the ambient physico-chemical conditions. Marked temporal and spatial differences in the elemental composition of suspended particles were found. At high river flow, suspended particulate compositions throughout the estuary were dominated by dilution and dispersion of an overwhelming flux of riverborne material. Under normal conditions of low riverine particle flux, internal cycling of particles, especially within the turbidity maximum region, controlled the spatial distributions of suspended particle compositions and subsidiary inputs were of greater significance.Key words: estuaries, suspended sediment, particle transport, trace elements
Sediments and Metal Pollutants in a Turbid Tidal Estuary
Authors: Thorn M. F. C. , Burt T. N.
Published: April 2011

An engineering study has been carried out in the tidal River Parrett, U.K., to investigate to what extent metals are trapped and stored within the estuary in its sediments. The River Parrett is a muddy estuary for which the sedimentary regime has been thoroughly studied and is quite well understood. Recently deposited bank sediments and sediments in suspension were sampled in a regular seasonal program, and their metal concentrations analyzed. In general, the relative magnitudes of metal concentrations correlated with the known annual inputs and the spatial distributions of all the metals within the estuary system were similar. The metal pollutants were found to have an affinity for the finer, cohesive sediment particles, and all comparisons of results are therefore based on concentrations on the same particle size fraction of the samples. The longitudinal distribution of metal pollutants in the tidal River Parrett was found to show a systematic seasonal variation. This variation is also mirrored in the layered depth variation of metal concentrations in accumulated sediment in a disused riverside berth. The results are consistent with the hypothesis that metal adsorption is enhanced by increased water salinity. There is no detectable long-term increase in metal concentrations in the sediments of the tidal River Parrett: the metal input is being adsorbed by the much larger sediment resources of the Severn Estuary without any noticeable effect on concentration levels.Key words: estuary, metals, mud, pollution, sediment
Spatial and Temporal Variability of Dinoflagellate Cyst Abundance in a Tidal Estuary
Authors: Balch William M. , Reid Philip C. , Surrey-Gent Sonia C.
Published: April 2011

A study of dinoflagellate cysts was made in an estuary near Plymouth, England for 1 yr. The data show that the cysts were most concentrated in sediments near the entrance of the estuary (3000 cysts (mL∙flocculant−1)) and less concentrated upstream (< 500 cysts (mL∙flocculant−1)). Dinoflagellate cysts were observed in 99% of the plankton samples with an average concentration of 9.2 cysts∙L−1. Thirty percent of the variance in planktonic cyst concentration was associated with tidal range, wind stress, and river flow. The potential for inoculation of nearshore dinoflagellate populations by estuarine populations is discussed.Key words: benthic resting cyst, dinoflagellate, estuary, frontal convergence, sediment trap, spring tides, turbulence
Effect of Turbidity on the Temporal and Spatial Utilization of the Inner Bay of Fundy by American Shad (Alosa sapidissima) (Pisces: Clupeidae) and its Relationship to Local Fisheries
Authors: Dadswell M. J. , Melvin G. D. , Williams P. J.
Published: April 2011

Since 1750, a unique, directed fishery for American shad (Alosa sapidissima) has existed in shallow, turbid, mega-tidal embayments of the inner Bay of Fundy during summer and fall. Tagging experiments indicated that migrating shad consisting of intermixed, river populations from the entire Atlantic coast of North America occur there between June and October. Shad migration was counterclockwise around the Bay following the residual current structure. Presence and duration of the shad run in Cumberland Basin was a result of interaction between migration timing, turbidity, and temperature. Mean daytime swimming depth was related to tidal phase and turbidity. High turbidity (Secchi [Formula: see text]) of the mega-tidal embayments apparently extends the preference zone for light intensity of ocean-feeding shad into surface waters (2–10 m), making them accessible to the local fishery.Key words: drift gillnets, shad migration, light intensity preference, swimming depth, mega-tidal, eastern Canada