bluuebunny/crossref_metadata_2025 huggingface dataset:
Lethal and Sublethal Effects of Binary Mixtures of Cyanide and Hexavalent Chromium, Zinc, or Ammonia to the Fathead Minnow(Pimephales Promelas) And Rainbow Trout (Salmo Gairdneri)
Authors: Broderius Steven J. , Smith Jr. Lloyd L.
Published: April 2011

Various models have been proposed to predict the combined interactive effect on fish of mixtures of poisons from separate toxicities of individual substances. The success of these models was tested, using data describing the lethal and sublethal effects of individual substances or binary mixtures of HCN and Cr(VI), Zn(II), or ammonia to the fathead minnow (Pimephales promelas) and rainbow trout (Salmo gairdneri). Using the strictly additive toxic unit and additive index approach, it was determined from log-dosage mortality curves that the Zn–HCN and ammonia–HCN mixtures were more acutely toxic and Cr–HCN less toxic than predicted. The concentration and response addition models, which have been proposed for toxicants whose joint action is similar or independent, respectively, could not be used to predict dosage–mortality curves for the HCN mixtures. Linear regression lines representing the growth response of fish to log concentration for toxicants alone and in binary combinations were not significantly different. Thus, for the toxic substances tested, the sublethal joint action of individual toxicants was not predictable from existing models and, in most cases, no interaction was indicated. The interactive nature of toxicants may be a function of the concentrations tested causing different biological processes to be affected (e.g. mortality vs. growth), and therefore different responses to be measured. A need still exists for development of a valid multiple toxicity approach for evaluating and predicting the toxicity of chemical combinations. Key words: multiple toxicity, binary mixtures, joint action, fish, bioassay, toxic substances
Comparative Susceptibility of Atlantic (Salmo salar) and Coho (Oncorhynchus kisutch) Salmon to Three Strains ofVibrio anguillarum From The Maine – New Hampshire Coast
Authors: Sawyer Evelyn S. , Strout Richard G. , Coutermarsh Bonita A.
Published: April 2011

Atlantic salmon (Salmo salar) were found to be as susceptible as coho salmon (Oncorhynchus kisutch) to Maine–New Hampshire strains of Vibrio anguillarum used in both injection and water transmission exposure. Exposure to 1–2.5 × 105 organisms/mL of one strain (569) in the water for 1 h killed 80–100% of Atlantic salmon at 10 and 15 °C. Should similar water exposure conditions occur in Maine estuaries, newly released Atlantic salmon smolts may encounter lethal levels of V. anguillarum. Key words: Vibrio anguillarum, Salmo salar, Atlantic salmon, susceptibility, marine bacteria.
Role of Phosphorus in Great Lakes Eutrophication: Is There a Controversy?
Authors: Schelske Claire L.
Published: April 2011

Phosphorus is undoubtedly the major plant nutrient controlling phytoplankton growth in the upper Great Lakes and the nutrient responsible for accelerated eutrophication in the lower Great Lakes. No studies published before 1970 provide conclusive evidence of the specific roles of phosphorus and other nutrients as growth limiting factors for phytoplankton. Improper citation of references can inadvertently cast doubt on the key role of phosphorus, or denigrate uncited work, depending on the reader's background. Key words: phosphorus, nitrogen, eutrophication, phytoplankton, limiting nutrients, Lake Michigan, Lake Superior, Lake Huron
Sampling Strategies and Life History of Non-Insectan Freshwater Invertebrates
Authors: Malley D. F. , Reynolds J. B.
Published: April 2011

Life history of benthic freshwater invertebrates, excluding insects, may influence a number of features of sampling programs, such as the environment sampled, sampling technique or equipment used, frequency and timing of sampling, and mesh sizes of nets or sieves. Consideration of the life history should increase the effectiveness of the program and, in the extreme, may allow one to recognize artifacts that would otherwise lead to incorrect conclusions.Aspects of life history that influence sampling programs are (1) direct or indirect embryonic development and the extent to which young are sampled simultaneously with adults during the breeding season, (2) times of year when various developmental stages are present, (3) differences in size between various life stages necessitating use of more than one sampling method during the year, (4) change in habitat due to migrations or assumption of a pelagic, parasitic, or aerial existence for part of the life cycle, (5) change in mobility over the life cycle, (6) sex differences in size or behavior, and (7) adaptations to adverse conditions. Examples of ways in which life history affects sampling are based on the literature and on original data on the opposum shrimp, Mysis relicta, and the crayfish, Orconectes virilis.We recommend that quantitative studies of benthic invertebrate communities be started with a pilot study employing at least two complementary sampling techniques and sufficiently frequent sampling times to allow the development of a reliable strategy for the objective. Key words: life history, sampling, benthic invertebrates, Crustacea, Mysis relicta, Orconectes virilis
Use of Macroinvertebrate Life History Information in Toxicity Tests
Authors: Buikema Jr. Arthur L. , Benfield Ernest F.
Published: April 2011

Life history information of macroinvertebrates is an important variable to consider when interpreting the results of toxicity tests. The importance of life history information has been recognized in the culturing of macroinvertebrates, but only in the last 5 yr has emphasis been placed on using this information in the design of acute and chronic toxicity tests. Sensitivity of organisms to toxicants is affected by nutrition, physiological requirements, behavior, predator–prey interactions, substrate, current, and light. There is need to integrate these, and other variables, to produce more defensible tests. Some features of life history may be used as end points in tests. Key words: macroinvertebrates, life history, toxicity, tests, design, sensitivity
Two Electivity Indices for Feeding with Special Reference to Zooplankton Grazing
Authors: Vanderploeg H. A. , Scavia D.
Published: April 2011

The electivity indices Ei and Ei′ of predator–prey interaction are currently used to quantify particle-size selection by grazers. Under conditions of passive, mechanical particle-size selection predicted by the leaky-sieve model, these indices yield electivity vs. particle-size curves that vary with the shape of the particle-size spectrum of food offered to the zooplankton. In addition to this bias, poor estimates of electivity will be obtained unless only a small fraction of the food is eaten in such experiments. The selectivity coefficient (Wi) used by modelers in feeding constructs and the electivity index Ei*, derived here, are recommended instead because they do not suffer from the shortcomings described for Ei and Ei′. Moreover, use of Wi′s and Ei*'s is recommended for quantifying selection for many other cases of predator–prey interaction. Key words: electivity indices, selectivity, selective grazing, predator–prey intraction
Correlations Between Daphnia magna and Fathead Minnow (Pimephales promelas) Chronic Toxicity Values for Several Classes of Test Substances
Authors: Maki A. W.
Published: April 2011

Chronic toxicity values were developed for Daphnia magna with six surfactants and a detergent builder, each selected on the basis of previously existing chronic fish test data. Predictive correlations were examined for testing end points between 21-d Daphnia chronics and 1-yr fish chronics to provide a short-term alternative chronic test species while developing toxicity data for an intermediate trophic level species. For the detergent materials tested, a strong correlation (r = 0.98) exists between Daphnia and fish no-effect concentrations. A replacement term, NOEC (no observed effect concentration), is suggested to clarify interpretive ambiguities associated with the definition of the MATC (maximum acceptable toxicant concentration) value. Additional chronic toxicity data from the current literature for these two test species and several test substances representing metals, polychlorinated biphenyl isomers, and pesticide formulations were similarly compared. A correlation analysis demonstrated an overall Pearson correlation coefficient of 0.79 for these data. Although significant outliers were evident from this correlation, these differences may be due primarily to differences in modes of toxic action of these test substances. The relatively short life cycle and 21-d duration of the test, small water volumes, ease in handling, high fecundity, and good correlation of 21-d chronic data with chronic fish toxicity data make Daphnia chronic tests an attractive alternative to the conduct of longer term fish tests. Key words: Daphnia, Pimephales promelas, toxicity tests, chronic, mortality, surfactants, metals, pesticides
Predation of Sea Scallops, Placopecten magellanicus, by the Rock Crab, Cancer irroratus, and the American Lobster, Homarus americanus
Authors: Elner Robert W. , Jamieson Glen S.
Published: April 2011

Various predation techniques used by rock crabs, Cancer irroratus, and American lobsters, Homarus americanus, to open sea scallop, Placopecten magellanicus, prey are reported. Adult rock crabs and lobsters successfully fed on sea scallops up to 72 and 76 mm in height, respectively. Juvenile lobsters were capable of preying on scallops whose height exceeded their own carapace length. Daily predation rates on a range of scallop sizes by various sizes of predator were obtained. Given a choice, both rock crabs and lobsters showed distinct and constant preferences for certain size scallops. This preferred prey size increased with predator size. These laboratory studies demonstrated that both rock crabs and lobsters are potential scallop predators. Key words: sea scallops, crabs, lobsters, predation techniques, prey selectivity
Quantification of Vitellogenin in Atlantic Salmon (Salmo salar) Plasma by Radioimmunoassay
Authors: Idler D. R. , Hwang S. J. , Crim L. W.
Published: April 2011

An antibody prepared against salmon egg yolk proteins has been used to quantify Atlantic salmon (Salmo salar) plasma vitellogenin using radioimmunoassay. A low molecular weight fraction isolated from salmon egg yolk was used for radioiodination and as standard solution because plasma vitellogenin could not be iodinated successfully. Parallelism of the egg yolk standard to displacement given by a fraction isolated from vitellogenic salmon plasma and dilutions of plasma samples allowed the assay to be used to evaluate the state of gonadal development of migrating females several months in advance of spawning and for sexing relatively immature salmon. Key words: salmon, plasma vitellogenin; vitellogenin, quantification in salmon plasma; radioimmunoassay, salmon vitellogenin
Pathogenesis of Infectious Pancreatic Necrosis in Atlantic Salmon (Salmo salar)
Authors: Swanson Robert N. , Gillespie James H.
Published: April 2011

Atlantic salmon (Salmo salar) fry and yearling were found to undergo an active but subclinical infection following exposure to infectious pancreatic necrosis (IPN) virus. Eight-week-old Atlantic salmon fry were fed live virus and the mortality and virus concentration in these fry were recorded over a period of 78 d following exposure. Yearling Atlantic salmon were inoculated intraperitoneally with IPN virus and the concentration of virus in the pancreas–intestine, kidneys, spleen, liver, and gonads of inoculated fish was determined over a period of 74 d following inoculation. Virus first appeared in the fry 3 d postinoculation (DPI) and virus titers reached a peak by 8 DPI. Low levels of virus persisted in fry sampled 78 DPI. Virus first appeared in the pancreas–intestine of Atlantic salmon 12 h postinoculation (HPI) and was detected in the kidneys, liver, and spleen by 72 HPI. Peak virus titers were reached in the pancreas–intestine by 72 HPI. Both the pancreas–intestine and kidneys continued to support viral growth frequently and appeared to be important reservoirs of virus. At no time was virus isolated from the gonads of inoculated yearling. Histological examination of yearlings revealed degenerative changes in the pancreatic acinar tissue and in some cases focal necrosis in the liver. No histological abnormalities were found in IPN-infected fry. Key words: infectious pancreatic necrosis, Atlantic salmon, virus, histology
Karyotypic and Evolutionary Relationships of the Yellowstone (Salmo clarki bouvieri) and West-Slope (S. c. lewisi) Cutthroat Trout
Authors: Loudenslager Eric J. , Thorgaard Gary H.
Published: April 2011

Yellowstone cutthroat trout (Salmo clarki bouvieri) have 64 chromosomes, without any subtelocentric chromosomes, while west-slope cutthroat trout (S. c. lewisi) have 66 chromosomes, including 12 subtelocentrics. Both subspecies have 104 chromosome arms. Chromosomal similarities are apparent between the Yellowstone cutthroat and Great Basin cutthroat subspecies, and between west-slope cutthroat trout and coastal cutthroat trout. These results demonstrate that at least two distinct evolutionary lines of cutthroat trout are present in the northern Rocky Mountain region. Key words: Salmo clarki, karyotypes, Yellowstone cutthroat trout, west-slope cutthroat trout, evolutionary relationships
Composition of Granules from Kidneys of Rainbow Trout (Salmo gairdneri) with Nephrocalcinosis
Authors: Gillespie D. C. , Evans R. E.
Published: April 2011

Histological sections and isolated granules from kidney tubules of rainbow trout (Salmo gairdneri) with nephrocalcinosis show that the mineral deposits form a network imbedded in a ceroid matrix. The mineral portion, about 80% by weight of the granules, contains 30% Ca, 2.5% Mg, 15% P, and 5% CO3. The matrix is basophilic, sudanophilic and acid fast, is insoluble in lipid solvents but will dissolve in hot 10% NaOH. Key words: nephrocalcinosis, calcification, ceroid, rainbow trout
Rate of Loss of Ammonia from Water to the Atmosphere
Authors: Weiler R. R.
Published: April 2011

The rate of loss of ammonia from water to the atmosphere has been measured both in the field and in the laboratory as a function of wind speed, temperature, and pH. The exchange coefficient, Ke, was found to be a linear function of wind speed and temperature. Although the loss rates (1–10 kg∙ha−1∙d−1) are quite high at pH 9 and at ammonia concentrations > 1 mg N∙dm−3, the rates are much smaller under the conditions found in most natural water bodies. Key words: ammonia, exchange coefficient, rate of loss from water
Anatomie de Latimeria chalumnae. Tome III. Appareil digestif — appareil respiratoire — appareil urogénital — glandes endocrines — appareil circulatoire — teguments — écailles — conclusions générales.
Authors: McAllister Don E.
Published: April 2011

not available
Economic and Social Implications of the Main Policy Alternatives for Controlling Fishing Effort
Authors: Crutchfield J. A.
Published: April 2011

Discussion of the need for economic rationalization has led to increasing interest in alternative strategies to control fishing effort in efficient ways. Three basic alternatives are considered: taxation, control of fishing inputs ("limited entry"), and direct limitation of output through individual fisherman quotas. Each is analyzed in terms of specified elements of economic efficiency, distribution effects, freedom to choose fishing methods and strategies, and administrative feasibility. It is noted that in practice all would be used in combination with other direct measures to assure flexible control over fishing mortality. A number of common objections to economic rationalization of open access fisheries (e.g. creation of monopoly power, unemployment, failure to reduce consumer prices, and nonmonetary values associated with fishing) are analyzed and rejected as largely invalid. While the inherent short-term instability of commercial fishing and data problems preclude any "maximizing" model of a rationalized fishery, the prospects for workable programs leading to improved economic performance without adverse societal impacts are excellent. Key words: fishery economics, taxation, limited entry, quotas, open access fishery, sociological aspects
Rational Fishery Management in a Depressed Region: the Atlantic Groundfishery
Authors: MacKenzie W. C.
Published: April 2011

The economic and social milieu of the commercial fisheries in the Atlantic provinces of Canada is described, followed by an analysis of the structure of the major sector, the fishery based on the demersal stocks of the region. Existence of the classic features of mature fisheries, i.e. congestion and economic distress, is established for this fishery and the causes considered. Extended national jurisdiction over the use of fishery resources, it is argued, while it improves opportunity for development, does not affect those causes. Possible approaches to rational management of the fishery are reviewed, in particular the institution of inducements for fishing enterprises to minimize production costs. A discussion in this respect of quasi property rights for resource users and associated problems concludes the paper. Key words: economic depression, congested fisheries, regional development, Atlantic provinces, groundfish(demersal) resources, industrial structure, fishery management, rationalization, quasi property rights.
Fisherman Behavior and the Design of Efficient Fisheries Regulation Programs
Authors: Wilen James E.
Published: April 2011

This paper examines the importance of hypotheses about fisherman behavior for predicting, understanding, and designing efficient fisheries regulation programs. Particular attention is paid to flexible technology fisheries where individuals are free to alter several dimensions of effort. It is suggested that the appropriate hypothesis of share-focused behavior ensures that there will always be an incentive to combine inputs inefficiently although technical conditions may limit or block the actual ability to do so. Some observations on the success of existing programs are also offered. Key words: fisheries regulation, efficiency, behavior, fishing industry
Measurement of Complexing Materials Excreted from Algae and Their Ability to Ameliorate Copper Toxicity
Authors: Berg C. M. G. Van den , Wong P. T. S. , Chau Y. K.
Published: April 2011

The complexing capacities of three algal exudates and the conditional stability constants of their copper complexes have been determined by an ion exchange method. Their ability to ameliorate copper toxicity towards the primary production of Chlorella vulgaris is related to the conditional stability constants, which regulate the ionic copper concentration. Anabaena cylindrica, Navicula pelliculosa, and Scenedesmus quadricauda excreted 6.73, 2.86, and 0.66 μmol/L of complexing ligands, respectively, with conditional stability constants of 107.7, 108.1, and 108.6, respectively, for their corresponding copper complexes. When these constants were applied in calculations, a free copper ion concentration of 10−10.3 mol/L was found in each exudate. Key words: algal exudates, free copper ion concentration, complexing capacity, copper ion toxicity, primary productivity
Swimming Behavior of Salmonid Fish in Ocean Pens
Authors: Sutterlin A. M. , Jokola K. J. , Holte B.
Published: April 2011

Based on personal observations and questionnaires to Norwegian fish farmers, the behavior of three species and several different stocks of salmonid fish reared in ocean pens is described. Swimming activity and the constancy of swimming orientation (clockwise or counter clockwise) vary among species. With few exceptions, the orientation of Atlantic salmon (Salmo salar) at any one farm does not change with tide, season, or age offish. Stock origin and/or the early rearing history may impose this directionality. The swimming of Atlantic salmon in pens resembles schooling behavior. Possible departures from this stereotyped behavior are considered. The behavior of pen-reared salmonids and its implications in selective breeding, migratory mechanisms, and fish health are discussed. Key words: salmon, behavior, pen rearing, mariculture, swimming, orientation, Salmo salar, S. gairdneri, Oncorhynchus gorbuscha
Fecundity and Reproductive Effort in the Blue Mussel (Mytilus edulis), the Sea Urchin (Strongylocentrotus droebachiensis), and the Snow Crab (Chionoecetes opilio) from Populations in Nova Scotia and Newfoundland
Authors: Thompson R. J.
Published: April 2011

Fecundity varies from year to year in blue mussels (Mytilus edulis) from Petpeswick Inlet, N.S., and from Bellevue, Nfld. This observation is consistent with recent theory that suggests that reproductive effort (that proportion of the energy budget allocated to reproduction) should be variable in animals such as marine bivalves that are unable to "predict" the quality of the environment for their juveniles. Estimates of fecundity in the sea urchin (Strongylocentrotus droebachiensis) and the snow crab (Chionoecetes opilio) are also presented. Reproductive effort increases with advancing age in the three species of invertebrates studied, although in the mussel the transition from growth to reproduction is more gradual than it is in the sea urchin or the female snow crab, which exhibit early growth and delayed reproduction. The degree to which the growth and reproductive phases are separated in each species may be determined in part by the predictability of the food supply. The allocation of resources primarily to growth rather than to reproduction in young (small) individuals may be seen as a response to selective pressure resulting from higher mortality and from competition. Key words: growth, production, reproductive strategy, energy partitioning, marine invertebrates, gametes
Age-Groups from Size-Frequency Data: A Versatile and Efficient Method of Analyzing Distribution Mixtures
Authors: Macdonald P. D. M. , Pitcher T. J.
Published: April 2011

For estimating age-group parameters from size-frequency data, conventional efficient statistical methods, such as maximum likelihood, can be more effective than the commonly used graphical methods of dissecting a mixed distribution. Fisheries size-frequency data are usually grouped over size intervals and the efficient methods are easily programmed on a computer for this case. We show that several published alternatives offer no computational advantages over our method. We describe an interactive computer program that assists the user in determining which parameters may be estimated from a set of data. The program alternates between constrained direct-search optimization and fast iterative calculations. Two examples of fisheries length-frequency data show that fitting is made easier by employing a subsample aged by biological methods for the preliminary starting values of parameters, and that the best fit may involve a trade-off between statistical precision and biological plausibility. The value of mixture analysis to the fishery worker is to reduce field and laboratory time in the aging of large samples. Key words: length-frequency data, size-frequency data, aging of samples, polymodal distributions, distribution mixtures, maximum likelihood estimation, nonlinear optimization, Phoxinus phoxinus, Esox lucius
Quantification of the Sediment Phosphorus Available to Aquatic Macrophytes
Authors: Carignan R. , Kalff J.
Published: April 2011

The specific activity of phosphorus taken up by three species of submergent macrophytes grown in partitioned containers and rooted in 32P-labeled sediments was shown to be identical to the specific activity of the sediment mobile phosphorus as measured by two techniques. Therefore, the mobile phosphorus, as determined by isotopic dilution, represents the total pool of sediment phosphorus available to macrophytes. The ability to measure and to specifically label this pool will allow the testing of hypotheses concerning the role of macrophytes in phosphorus cycling. Key words: macrophytes, phosphorus availability, isotopic dilution
Measurements of Oxidants in Ozonized Seawater and Some Biological Reactions
Authors: Crecelius Eric A.
Published: April 2011

Ozonization of seawater oxidizes bromide ion to bromine (hypobromus acid and hypobromite ion) and then to bromate. If seawater is ozonized for more than 60 min, essentially all bromide is converted to bromate. Ozonization of high purity sodium chloride solution did not produce significant oxidants. However, ozonization of sodium bromide solution produced both bromine and bromate. Ozone is unstable in seawater and was undetectable several minutes after the ozonization was completed. Bromate toxicity tests on marine animals indicate the levels of bromate produced by chlorination or ozonization of power plant cooling waters are not acutely toxic. The LC50 ranged from 30 mg/L bromate for Pacific oyster, Crassostrea gigas, larva to several hundred mg/L for fish, shrimp, and clams. Key words: ozone, oxidants, bromate, bromine, seawater, toxicity
Exploitation of Marine Mammals: r-Selection of K-Strategists?
Authors: Estes James A.
Published: April 2011

The importance of marine mammals as predators to the organization of marine communities is poorly known, although in several structurally analogous systems the ecological and evolutionary roles of predators are known to be of considerable importance. Occupation of the marine environment by mammals probably carried physiological constraints for single-young pregnancies thereby limiting all species to low intrinsic rates of population increase. As such, species subjected to high mortality rates from predation or other natural disturbances became extinct; those that survived probably were largely resource limited. In view of this scenario it is suggested that stable populations of marine mammals can be maintained at high levels without being manipulated in most communities. Exploitation probably constitutes a rather dramatic environmental change to marine mammals consequently subjecting them to selective forces fundamentally different from many of those under the influence of which they evolved. Key words: community structure, evolution, exploitation, fitness, life history, marine mammal, predation, resource limitation
Recovery of Invertebrate and Vertebrate Populations in a Coal Ash Stressed Drainage System
Authors: Cherry Donald S. , Larrick Stephan R. , Guthrie Rufus K. , Davis Ernst M. , Sherberger Fred F.
Published: April 2011

The influence of coal ash effluent upon the densities of macrobenthic invertebrate and mosquitofish (Gambusia affinis) populations in a swamp drainage system was studied for a period of 50 mo. Density of the aquatic biota was periodically altered by three major perturbations: (1) heavy ash siltation from inefficient basin operation, (2) lowered pH from the fly ash addition, and (3) coal ash associated elemental concentrations. Siltation appeared to be most influential in reducing the invertebrate densities while low pH (mean change from 7.2 to 5.5, extreme of 3.5) was more effective in reducing mosquitofish populations and retarding the recovery of invertebrates. Dipterans (chironomids) and odonates (Plathemis lydia and Libellula spp.) were the invertebrates most tolerant to coal ash stress. Upon the completion of an efficient primary–secondary retaining basin system, most invertebrate groups in the swamp were able to recover to a level of abundance equal to or greater than that which existed 4 yr earlier. Key words: coal ash stress, heavy ash siltation, fly ash acidity, elemental accumulation, benthic macroinvertebrates, Gambusia affinis
Obligate Anaerobic Bacteria in the Gastrointestinal Microflora of the Grass Carp (Ctenopharyngodon idella), Goldfish (Carassius auratus), and Rainbow Trout (Salmo gairdneri)
Authors: Trust T. J. , Bull L. M. , Currie B. R. , Buckley J. T.
Published: April 2011

Grass carp (Ctenopharyngodon idella), bred in Arkansas and maintained in British Columbia under defined culture conditions on pelleted diets and on aquatic weeds, were examined to determine their commensal gastrointestinal bacterial flora. Using anaerobic incubation, the total bacterial numbers cultured ranged from 6 × 104 to 4 × 108 (average 4 × 106) per g of alimentary tract plus contents. Obligately anaerobic bacteria were isolated and identified as species of Actinomyces, Bacteroides, Eubacterium, Fusobacterium, and Peptostreptococcus. This is the first description of the presence of these strictly anaerobic organisms in the gastrointestinal tract of fish. Indeed, many of the anaerobes isolated did not conform to previously described species. Members of the Genus Clostridium were also isolated by enrichment culture and appeared to be associated with a pond weed diet. A wide variety of facultative anaerobic bacteria were also isolated, with Aeromonas hydrophila predominating. The gastrointestinal tracts of goldfish (Carassius auratus) were also found to contain sizable numbers of obligate anaerobes, but the gastrointestinal tracts of hatchery-cultured rainbow trout (Salmo gairdneri) contained insignificant numbers. Key words: grass carp, anaerobic bacteria, gastrointestinal microflora, Aeromonas hydrophila, rainbow trout, goldfish
Relative Efficiency of Multifilament and Monofilament Nylon Gill Net Towards Lake Whitefish (Coregonus clupeaformis) in Lake Huron
Authors: Collins J. J.
Published: April 2011

In the early 1970s Lake Huron fishermen converted their gill nets from multifilament to monofilament nylon web in the lake whitefish (Coregonus clupeaformis) fishery. Catch comparisons in the two gears showed that monofilament nets were 1.8 times more efficient (but varied seasonally), resulting in biased commercial catch statistics. The use of monofilament web has probably increased exploitation pressure on whitefish. Both gears selected whitefish of the same size despite stock differences in individual size and shape. Catches in both gears declined during the full moon phase, possibly due to increased net visibility. Key words: mono-multifilament gillnet efficiency, selectivity, lunar illuminance, Coregonus clupeaformis, Lake Huron
Impact of Brook Trout (Salvelinus fontinalis) Predation on the Crayfish Orconectes virilis in Three Michigan Lakes
Authors: Gowing H. , Momot W. T.
Published: April 2011

The crayfish Orconectes virilis is a major component of the benthos of three small lakes in northern Michigan. These lakes contained stocked brook trout (Salvelinus fontinalis) populations (age-0 and age-I) at densities of 188, 411, and 1398 fish/ha. Crayfish were preyed upon by brook trout, but only during their first year of life. Two-year production of age-0 crayfish was approximately 94 kg in each lake; brook trout consumed only about 1–2% in lakes with lower density offish. Even with greater trout density and accompanying higher rate of exploitation (40%), there was no impact on recruitment of young crayfish because compensatory mortality of crayfish occurred in lakes with less trout predation. However, stocking trout at higher densities decreased trout growth and condition. While 2-yr production was highest (59 kg/ha) in the lake stocked at the highest density and lowest (17 kg/ha) in one stocked at the lowest density, the former was achieved at the cost of a very slow growing trout population. Most of the crayfish production is not utilized as trout food but enters the non-predatory pool of detrital organic matter. Key words: Orconectes virilis, brook trout, predation, production growth, mortality
Influence of the Shelf-Break Front Off Nova Scotia on Phytoplankton Standing Stock in Winter
Authors: Fournier R. O. , Det M. Van , Wilson J. S. , Hargreaves N. B.
Published: April 2011

Observations made on the shelf-break front off Nova Scotia during winter on 2 successive yr show the concentration of chlorophyll a in the euphotic zone to be correlated to the inclination of the subsurface front. The steepness of the front influences the depth to which phytoplankton are mixed which in turn controls the average amount of illumination received by a given cell. The two winter observations showed the subsurface front at each of two extremes: vertical with little phytoplankton biomass and almost horizontal with significant quantities of chlorophyll. Calculations were made as to the amount of production enchancement that could result from shallowing of the mixed layer by decreased frontal inclination. They show that during the winter under ideal conditions as few as 35 d of intermittent growth increase annual production in the frontal region by 25%. Key words: front, winter production, phytoplankton, shelf-break, chlorophyll a, frontal oscillations, growth enhancement, stability, stratification
Temperature Influence on Basal Activity and Induction of Mixed Function Oxygenase Activity in Fundulus heteroclitus
Authors: Stegeman John J.
Published: April 2011

Treatment of Fundulus heteroclitus acclimated to 6.5 °C with benzo(a)pyrene did not elicit any change in the levels of hepatic microsomal NADH- or NADPH-cytochrome c reductase activity, nor in the levels of cytochrome P-450 or its catalytic activities. However, the same treatment offish at 16 5 °C resulted in a marked induction of benzo(a)pyrene hydroxylase and NADPH-cytochrome c reductase. Cytochrome P-450 content was also higher in the warm, treated fish and the Soret maximum of reduced, CO-treated microsomes was shifted to the violet. Levels of aminopyrine demethylase and NADH-cytochrome c reductase activities did not show a significant treatment effect. At neither temperature could treated and control fish be distinguished on the basis of in vitro inhibition of benzo(a)pyrene hydroxylase activity by 7,8-benzoflavone. Levels of NADPH-cytochrome c reductase and benzo(a)pyrene hydroxylase activities were greater in control Fundulus acclimated to 6.5 °C than to 16.5 °C, when normalized to microsomal protein, but not when based on body weight. The results indicate that habitat temperature alone may not affect the capacity for initial hydrocarbon metabolism in fish, but that it can strongly influence the induction of cytochrome P-450. Key words: temperature, cytochrome P-450, hydrocarbon metabolism, mixed-function oxygenase, Fundulus heteroclitus
Feeding by Hatchery-Reared and Wild Atlantic Salmon (Salmo salar) Parr in Streams
Authors: Sosiak A. J. , Randall R. G. , McKenzie J. A.
Published: April 2011

Hatchery-reared Atlantic salmon (Salmo salar) parr were captured 1–3 mo after release in streams, along with wild parr from the same streams. Identification of their stomach contents showed total number of organisms and number of taxa per stomach were greater and there was a higher index of stomach fullness in wild than in hatchery parr resident ≤ 2 mo in a stream. Wild parr consumed more Brachycentridae, Hydroptilidae, Diptera, and Plecoptera than did hatchery parr, but sometimes less Odontoceridae and Heptageniidae. These differences may have arisen from size-dependent food selection, the effects of feeding experience, or possible microhabitat differences between wild and hatchery parr. Key words: salmon parr, hatchery-reared, wild, feeding
Influence of Benthos Life History upon the Estimation of Secondary Production
Authors: Waters T. F.
Published: April 2011

Synchrony of cohorts is one of the life history features having most important effects upon the estimation of benthic secondary production, because most methods depend heavily upon recognition of discrete cohorts. The Hynes method, intended to circumvent the necessity of cohort distinction, still depends upon determination of trophic level, voltinism, minimum and maximum sizes, and length of aquatic life. Knowledge of preferred habitat, distribution, and behavior are essential for accurate production estimates. Use of the production:mean standing stock (P/B) ratio (fairly constant at about 5 for cohort P/B of benthic invertebrates) to approximate production from standing stock data, also must account for trophic level, voltinism, and length of aquatic life. Various life history features are compared as to their probable effect on production estimation; in addition, they are compared to the effect of sampling errors. Key words: benthos, life history, production, secondary production, productivity
Aggregation, Transformation, and the Design of Benthos Sampling Programs
Authors: Downing John A.
Published: April 2011

Solutions are offered to the problems of data transformation and the design of efficient programs for sampling the benthos of lakes and large rivers. All types of benthic animals from many types of substrate, sampled with diverse sampling gear, are aggregated in a similar fashion. Aggregation can be indexed by the unbiased exponent of the power relationship between density and variance. A single variance stabilizing transformation can be used for all macrobenthos population data since the relationship of sample variance to mean density is similar in all taxa of benthic animals. Stabilized variance in population data satisfies one of the main assumptions of the analysis of variance and allows use of normal statistics provided that the other assumptions are met. The fourth-root transformation stabilized the variance in all macrobenthos samples while either the commonly used square root or logarithmic transformations did not. Sampling programs can be optimized empirically. Standard deviation (s) is predictable from mean density (M; m−2) and sampler size (A; cm2) from the equation: log10s = 0.581 + 0.696 log10M − 2.82 × 10−4 A. The data show that it is easier to obtain a precise estimate of macrobenthos density at high densities. Small diameter samplers are most efficient in obtaining high levels of precision. Data were taken from the literature. Key words: aggregation, benthos, freshwater, regression, sampling, transformation
Polycyclic Aromatic Hydrocarbon Carcinogens in Commercial Seafoods
Authors: Dunn Bruce P. , Fee John
Published: April 2011

Fresh and processed commercial seafoods were analyzed for the polycyclic aromatic hydrocarbon carcinogen benzo(a)pyrene using a thin-layer chromatographic separation technique and quantitation by fluorescence. Commercial samples of vertebrate fish did not contain detectable levels, except where fish were packed with vegetable oil, an exogenous source of carcinogens. Levels in most shellfish samples were generally less than 10 ng/g wet weight, but occasional samples contained up to 36 ng/g. Crab and shrimp samples contained little or no benzo(a)pyrene (ND to 0.5 ng/g). Commercial lobsters contained 0.8 to 7.9 ng/g. The source of contamination of lobsters was further investigated, utilizing high pressure liquid chromatography to measure 13 polycyclic aromatic hydrocarbon isomers. Freshly caught lobsters had less than 1 ng/g benzo(a)pyrene. Lobsters which had been kept in a commercial tidal pound constructed of creosoted timber contained highly elevated levels of benzo(a)pyrene and other carcinogenic hydrocarbons, including chrysene, benzo(a)anthracene, benzo(b)fluoranthene, dibenz(a,h)anthracene, and indeno(1,2,3-cd)pyrene The maximum level of benzo(a)pyrene was 2300 ng/g wet weight in digestive gland, and 281 ng/g in edible tail meat. These levels are substantially higher than previously reported for any foodstuff, and are most probably attributable to creosote contamination during impoundment. Key words: benzo(a)pyrene, polycyclic (polynuclear) aromatic hydrocarbon, carcinogen, seafood, lobster, shellfish, creosote
On Representing the Length Dependence of Acoustic Target Strengths of Fish
Authors: Foote Kenneth G.
Published: April 2011

The problem of representing the length dependence of acoustic target strengths of fish is addressed by studying the legitimacy of merging target strengths that are inhomogeneous in species or frequency. The target strengths are of two kinds: maximum and averaged dorsal aspect target strengths, which are derived from measurements of gadoid target strength functions of three species at two ultrasonic frequencies. The target strengths are expressed variously according to unnormalized, wavelength-normalized and length-normalized schemes. Overall coincidences and coincidences of slopes among simple linear regressions of target strength on fish length, when segregated by target strength type and manner of representation, are investigated through analysis of covariance. Examination of computed significance levels demonstrates that merging of target strengths in species or frequency is generally unjustified and that no one representation method is superior to another in facilitating the merging of such data. The unnormalized representation is to be preferred when merging is justified because of its simplicity and avoidance of the frequency bias inherent in the normalized representations. The hypothesis of scaling of target strengths is refuted. Key words: target strength, regression, covariance analysis, fish abundance estimation
Mode of Life and Feeding in Maldanid Polychaetes from St. Margaret's Bay, Nova Scotia
Authors: Hughes T. G.
Published: April 2011

The habits and behavior of Axiothelia catenata, Praxillella gracilis, and Nicomache lumbricalis (Polychaeta: Maldanidae) are described. Each feeds from a different level in the sediment thereby reducing competition for food and space. All three maldanids are generally unselective in the material they ingest and from which they construct tubes. Thus within certain limits the particle size of the sediment is thought not to be a critical factor in determining their distribution and abundance. Axiothella catenata does not produce fecal pellets but particles are still aggregated in the gut and a large proportion of bacteria attached to sediment particles though the gut undigested. Axiothella catenata egests material in proportion to its size; a specimen of 4-mm internal tube diameter egests 1.10 ± 0.15 mL/d. Key words: benthos, detritus feeders, Annelida, Polychaeta, Maldanidae
A Bacterium Associated with Disease of Pond Cultured Channel Catfish, Ictalurus punctatus
Authors: Hawke John P.
Published: April 2011

A new bacterial disease affecting primarily pond reared fingerling channel catfish, Ictalurus punctatus, is described from 17 instances reported from June 1976 through December 1978. Terramycin medicated feed controlled the disease when early diagnosis was possible. Terramycin resistant strains were not detected. The causitive organism was confirmed as a previously unidentified species of Edwardsiella by the Center for Disease Control Atlanta Georgia. The disease is referred to as Enteric Septicemia of Catfish (ESC). Optimum growth temperature is between 25 and 30 °C; this correlated with pond water temperatures during instances of mortality on fish farms. Koch's postulates were fulfilled using channel catfish fingerlings in 40-L aquaria. Key words: Fish disease, bacterial fish pathogen, enteric bacteria, channel catfish diseases
Wax Esters in the Marine Environment: Origin and Composition of the Wax from Bute Inlet, British Columbia
Authors: Lee Richard F. , Nevenzel Judd C.
Published: April 2011

During severe winters large amounts of a solid lipid accumulate on the water surface and on the shores of Bute Inlet, a deep fjord on the mainland of British Columbia. Chromatographic analyses show that this wax consists chiefly of wax esters (48%), with minor amounts of hydrocarbons (4%) and triacylglycerols (6%). Dominant among the zooplankton in this inlet is the copepod Calanus plumchrus, which also is rich in wax esters (40–50% of dry weight). Except for the lack of polyunsaturation in Bute Inlet wax there is a close similarity between the wax ester, alcohol, and fatty acid compositions of C. plumchrus and Bute Inlet wax. The major hydrocarbon of both is pristane. We hypothesize that Bute Inlet wax is produced by some major change in water conditions which cause a massive kill of copepods. At winter temperatures this lipid is a solid and as such may accumulate on the beach. Copepods are the likely source for the wax esters in slicks and sediments reported from oceanic areas throughout the world. Key words: marine pollution, biological pollutant, lipid, hydrocarbon, wax, zooplankton, Copepoda
Opossum Shrimp (Mysis relicta) Predation on Zooplankton
Authors: Cooper Scott D. , Goldman Charles R.
Published: April 2011

Mysis relicta clearance rates were not affected by changes in prey and predator density in single-prey systems where Epischura nevadensis late instars were used as food. A comparison of the results obtained from single-, two-prey, and multiple-prey systems revealed that Mysis clearance rates of E. nevadensis late instars and Diaptomus tyrrelli males were significantly affected by the presence and abundance of alternative prey.When offered natural prey assemblages, the smallest Mysis preyed preferentially on the smallest available prey (Bosmina, Ceriodaphnia, Diaptomus nauplii) while larger Mysis showed an increased preference for larger prey (Epischura, Daphnia). In general, Mysis preferred Daphnia over copepods; Epischura, Ceriodaphnia, Bosmina, and cyclopoid copepods over Diaptomus copepodites and adults; and Diaptomus males over Diaptomus females. Total consumption rates increased with increasing predator size and starvation duration. Food selectivity patterns exhibited by Mysis were attributed to the mechanical efficiency with which the predators captured and handled food particles of different sizes, to the vigor of prey escape responses, and to predator–prey encounter frequencies.Key words: Mysis relicta, predation, zooplankton, feeding preferences, opossum shrimp
Assessment of Thermal Discharges on Zooplankton in Conowingo Pond, Pennsylvania
Authors: Mathur Dilip , Robbins Timothy W. , Purdy Jr. Edmund J.
Published: April 2011

Assessment of the impact of power station operation on zooplankton communities requires separation of natural variations from those due to the facility. Analysis of covariance (density of zooplankton at control station, ambient water temperature, and average daily river flow as covariates) proved powerful in separating the natural variations from those due to the operation of Peach Bottom Atomic Power Station (once-through cooling system) in Conowingo Pond, a 35.8-km2 impoundment on the lower Susquehanna River. The covariance technique overcame some of the problems associated with using ratio of density at control station to the density at an affected station to adjust for ambient variations. Significant differences in adjusted preoperational and postoperational means occurred but were not attributable to station operation. Multiple regression analysis indicated that an increase in zooplankton production, particularly in winter, would result with addition of heated water when river flows are < 280 m3/s. The zooplankters were subjected to an average ΔT of 10.0 °C in winter and up to 8.0 °C in summer. Zooplankton population showed a great amount of resiliency in Conowingo Pond.Key words: zooplankton, heated effluents, statistical analysis, power plant impact
Modeling Growth–Time and Weight–Length Relationships in a Single Year-Class Fishery with Examples for North Carolina Pink and Brown Shrimp
Authors: Cohen Marc-David , Fishman George S.
Published: April 2011

This paper presents an extension of the classical concepts of growth over time and of a weight–length relationship for a single year-class fishery that explicitly accounts for the stochastic variation known to exist in such a population. It also shows how the extended conceptualization enables one to look at alternative characterizations of a fish population that can be useful when deciding whether or not to allow fishing. Techniques for estimating the extended models efficiently are described, as are procedures for testing for differences in growth and weight–length parameters based on sex and subspecies. The potential use of these models to facilitate the quantification of population biomass is also presented. Data on North Carolina pink and brown shrimp (Penaeus duorarum and P. aztecus) are used to illustrate the concepts and models. Algorithms for effecting several of the proposed procedures are included.Key words: growth, weight, length, biomass, Penaeus duorarum, P. aztecus, von Bertalanffy curve