bluuebunny/crossref_metadata_2025 huggingface dataset:
Infectious Pancreatic Necrosis: Experimental Induction of a Carrier State in Trout
Authors: Reno P. W. , Darley S. , Savan M.
Published: April 2011

Infection of 11-mo-old rainbow trout (Salmo gairdneri) with a strain of infectious pancreatic necrosis virus (IPNV) resulted in an inapparent viremia and low levels of anti-IPN-NB antibodies in the serum. Virus was isolated from internal organs and at 110 d after infection reached 103.5 tissue culture infectious doses 50% endpoint (TCID50)/g in the spleen, kidneys, and pyloric ceca, but was 10–100-fold less in other organs. By 150 d after infection, IPNV was virtually undetectable. When 1-mo-old brook trout (Salvelinus fontinalis) were immersed in virus, survivors became carriers for 1 yr. Virus titer reached a maximum of 107 TCID50/g and then declined but remained at levels between 103 and 104 during the 1-yr observation period. Serum samples collected from the brook trout 10 mo after infection contained low levels of anti-IPN-NB antibodies. Thus an IPN carrier state was induced in yearling and juvenile trout and the infection was sustained for a long period. Key words: infectious pancreatic necrosis, inapparent infection, fish viruses, salmonids
Predation by Rainbow Smelt (Osmerus mordax) on Lake Herring (Coregonus artedii) in Western Lake Superior
Authors: Selgeby James H. , MacCallum Wayne R. , Swedberg Donald V.
Published: April 2011

The stock of lake herring (Coregonus artedii) in the Apostle Islands (Wisconsin) region of western Lake Superior has diminished severely during the past 30 yr, and predation by rainbow smelt (Osmerus mordax) on herring larvae has been considered a possible cause of this decline. In contrast, the herring stock in Black Bay, 160 km to the northeast, has remained nearly stable despite the presence of large numbers of smelt and high commercial production of herring. Predator–prey interactions were studied in both areas during 1974. Herring larvae and smelt were about 120 and 3 times as dense, respectively, in Black Bay as in the Apostle Islands region. Substantial predation by smelt on young herring was evident in Black Bay, where 17% of 1195 smelt stomachs examined contained herring larvae. From calculations of the relative densities of the two species, and of the daily ration of the predators, we estimated that smelt consumed 3.3–11% of the herring larvae. Nevertheless, the herring stocks have sustained average historical levels of commercial production. In contrast, no herring larvae were found in the stomachs of 1711 smelt collected in the Apostle Islands region. We conclude that predation by smelt on herring larvae is not the major factor controlling or suppressing herring stocks in either region. Key words: lake herring, rainbow smelt, predation, Lake Superior
Implication of Geographic Location on Temperature Preference of White Perch, Morone americana
Authors: Hall Jr. Lenwood W. , Hocutt Charles H. , Stauffer Jr. Jay R.
Published: April 2011

Temperature preference tests were conducted on freshwater white perch (Morone americana) collected from Albemarle Sound, N.C.; Wicomico River, Md.; and Mullica River, N.J. Collection temperatures for each population were 25 °C (±2 °C) and acclimation temperatures used in temperature preference tests were 6, 12, 18, 24, 30, and 33 °C. Analysis of covariance determined that a significant difference exists in the temperature preference of the white perch populations tested. The calculated final temperature preference using linear regression for North Carolina, Maryland, and New Jersey populations was 32.4, 28.9, and 29.6 °C, respectively. Calculated final temperature preferenda using the quadratic equation for North Carolina, Maryland, and New Jersey populations were 31.6, 29.3, and 29.2 °C, respectively. Visual estimation yielded final temperature preference values of 32.5, 30.6, and 29.6 °C for North Carolina, Maryland, and New Jersey populations, respectively. Key words: White perch, Morone americana, temperature preference, final preferenda, population responses, linear regression, quadratic equation, visual estimation
A removal experiment with Octopus dofleini (Wulker)
Authors: Hartwick E. B. , Breen P. A. , Tulloch L.
Published: April 2011

All Octopus dofleini martini were removed from a study area in Clayoquot Sound, B.C., during a 6-wk period, and they and their dens were measured. There was an exponential relation between octopus size and the size of den it occupied. In addition, small octopus tended to be found in newly dug dens, while large ones occupied natural dens. Some dens from which octopuses were removed were recolonized by animals of similar size but many remained empty and new dens were often dug in areas where dens already existed. Immigration of octopuses into the control area at the same time suggests that the observed recruitment was not brought about by the harvest. Females were more numerous than males, especially in the smallest sizes. Our study points toward the feasibility of a size-selective trap fishery. Key words: octopus, harvest, recruitment, denning, predation
Influences of Dieldrin on the Growth and Body Composition of Fingerling Rainbow Trout (Salmo gairdneri) Fed Oregon Moist Pellets or Tubificid Worms (Tubifex sp.)
Authors: Phillips Glenn R. , Buhler Donald R.
Published: April 2011

Fingerling rainbow trout (Salmo gairdneri) fed tubificid worms (Tubifex sp.) grew faster than those fed Oregon Moist Pellets (OMP) over a similar range of rations. Faster growth resulted because trout incorporated protein and fat from tubificids more efficiently than from OMP. Exposure to a sublethal concentration of dieldrin in water (0.18 μg/L) did not affect the protein elaboration of trout fed either diet or fat metabolism in trout fed OMP. However, dieldrin reduced fat elaboration in trout fed tubificids. The dieldrin concentrations in trout exposed to dieldrin in water increased as feeding level (and therefore body fat) increased. The different responses to dieldrin by fish fed these two diets provides evidence that the diet offered to fish can significantly influence the outcome of chronic toxicity tests. Key words: Rainbow trout, tubificid worms, Oregon Moist Pellets, dieldrin, growth, fat metabolism
Sublethal Effects of Environmental Acidification on Rainbow Trout (Salmo gairdneri)
Authors: Neville C. M.
Published: April 2011

Dorsal aorta blood samples were taken from cannulated rainbow trout (Salmo gairdneri) exposed to pH 4.0 (acid group) or pH 7.0 (controls) in normocapnic conditions at 10 °C. Over a 5-d period there was a significant gradual decrease in pH and total CO2 in the acid group but no significant difference in pO2 and lactate compared to the controls. After uncannulated rainbow trout were exposed to the same conditions for 12 d there were significant increases in hemoglobin, hematocrit, and erythrocyte levels in caudal vein samples from the acid group. The results show that rainbow trout exposed to acid without hypercapnia develop acidaemia which is not a result of anaerobic respiration. The increase in erythrocyte concentration probably offsets the effects of acidaemia upon blood oxygen carrying capacity. Differences in ambient pCO2 and/or species differences could account for varying acid-base values in acid exposed fish reported by different workers. Key words: environmental acidification, acidaemia, lactate, pH, total carbonate, fish
Myxosoma cerebralis: a Method for Staining Spores and Other Stages with Silver Nitrate
Authors: Wolf Ken , Markiw Maria E.
Published: April 2011

Eleven dye substances were tested for their ability to stain Myxosoma cerebralis and to be retained through either the pepsin-trypsin-dextrose or the plankton centrifuge method of releasing and concentrating spores. Silver nitrate proved to be the best; it produced a distinctive brown color that has been retained by spores through 2.5 yr of storage. The method has applications in histologic studies of whirling disease, in quantifying the efficiency of spore detection procedures, and in teaching. Key words: myxosporidans, Myxosoma cerebralis, whirling disease, spore staining
Iodine Balance in Rainbow Trout (Salmo gairdneri) and Effects of Testosterone Propionate
Authors: Hunt David W. C. , Eales J. G.
Published: April 2011

Iodine balance was studied in immature rainbow trout (Salmo gairdneri) held at 12 °C in water of iodine content 1.85 μg/L and fed daily 1% of body weight with food containing 0.48 μg I/g. Iodide flux into the plasma pool was 148 ng I∙h−1∙100 g−1 of which < 1% was contributed by peripheral deiodination of thyroid hormones, up to 16% was obtained from the diet, and at least 84% was derived from the water. Less than 5% of iodide intake was required to satisfy thyroidal secretory demands. Testosterone injections elevated plasma iodide and protein levels, but did not alter the rate of plasma iodide turnover. Key words: trout, iodine balance, thyroid function, testosterone
Contribution of Life History Information to Taxonomy of Aquatic Insects
Authors: Oliver D. R.
Published: April 2011

Life history studies may contribute to taxonomy by providing corroborative or clarifying data about existing taxonomic systems or may suggest reevaluation. Specifically, life history studies may provide information on the presence or absence of reproductive isolation, associated life stages, monospecific specimens, specimens for character evaluation, and a forum where ecologists and taxonomists may interact. Key words: taxonomy, life histories, benthos, reproductive isolation, life stages, character evaluation
Temperature Selection and Estimated Thermal Acclimation by Rainbow Trout (Salmo gairdneri) in a Thermal Plume
Authors: Spigarelli S. A. , Thommes M. M.
Published: April 2011

Body temperatures of rainbow trout (Salmo gairdneri) caught from a thermal discharge into Lake Michigan were used to determine selected temperatures and to estimate acclimation temperatures of this species under field conditions. Approximately 65–75% of the variability in body temperatures was related to water temperature (direct) and fish weight (inverse). Body temperatures increased with increases in discharge temperature, but the difference between body and ambient water temperatures decreased at high water temperatures. The modal body temperature of small fish was 19 °C, the final preferred temperature predicted for rainbow trout by some lab studies. The modal body temperature of large fish was 15 °C. Estimates of acclimation temperatures indicate that the majority of rainbow trout caught in this discharge area were acclimated to plume temperatures. Estimated acclimation temperatures exceeded ambient acclimation by as much as 10 °C for individual fish while group means ranged between 2 and 6 °C over ambient acclimation. Key words: temperature selection, acclimation, thermal plume, rainbow trout, Lake Michigan, body temperature, size effect
Selective Predation by Drift-Feeding Brown Trout (Salmo trutta)
Authors: Ringler Neil H.
Published: April 2011

Consumption of three species of prey by brown trout (Salmo trutta) in a laboratory stream was studied during 7-d experiments. Two drift rates (5 and 10 organisms/min) and three ratios (1:1, 2:1, 5:1) of small:large alternative prey were employed. Responses to prey species stabilized after 4–6 d and 800–1200 prey captures, but no prey was completely excluded from the diet. Size-selective predation was a dominant characteristic of the response. The fish appeared to alter the area (depth) searched in response to prey density; electivity was greatest when prey densities were high. Disproportionate predation on abundant prey ("switching") was a temporary phenomenon, which may have been masked by prey size. Brown trout ultimately achieved 54–91% of a hypothetical diet in which prey are ranked in order of size (energy content). Deviations from an optimal diet may be explained in terms of a feeding strategy that deals with heterogeneous distribution of prey, as well as with the behavioral capabilities of the predator. Key words: behavior, fish, invertebrate drift, optimal foraging, predation, prey size and abundance, Salmonidae, search image, streams
World Distribution of Atlantic Salmon, Salmo solar
Authors: MacCrimmon Hugh R. , Gots Barra L.
Published: April 2011

Since the mid-19th century, numerous attempts have been made to restore or enhance populations of the Atlantic salmon, Salmo salar, within the endemic range, and to establish the species in other parts of the world. Despite all efforts, salmon have become naturalized locally only in eastern North America, Argentina, the Faeroe Islands, and New Zealand. Principal factors affecting the disappearance, restoration, or naturalization of populations are water temperature and availability of suitable spawning and nursery sites. Commercial exploitation of the species in coastal and offshore waters is viewed internationally as a factor of increased importance in the numerical regulation of river spawning runs. A further expansion of the world distribution of Atlantic salmon by naturalization seems unlikely except in areas where preliminary plantings have been made or brood stocks are presently held. Atlantic salmon produced by commercial sea farming operations in Norway, Scotland, Spain, and France are considered to be of comparable quality to fish harvested from the wild. Also, there is presently interest in the potential of sea ranching of Atlantic salmon. Key words: zoogeography, endemic range, naturalized range, artificial propagation, environmental impact, exploitation, aquaculture
Pygmy Whitefish, Prosopium coulteri, in Three Lakes of the Copper River System in Alaska
Authors: Bird Franklin H. , Roberson Kenneth
Published: April 2011

Pygmy whitefish (Prosopium coulteri) were recorded for the first time from the Copper River drainage in Alaska (from Tazlina, Klutina, and Tonsina lakes). Morphology of the specimens indicate affinity to the Lake Superior and Waterton Lake populations, falling outside the ranges previously established for "low-rakered" and "high-rakered" forms found in Alaska. Based on geographical proximity, however, probable origin for these fish is from an upper Yukon River unglaciated refugium. Key words: pygmy whitefish, Copper River, Alaska, morphology, Yukon River, unglaciated refugium
Net Entanglements of Baleen Whales in the Inshore Fishery of Newfoundland
Authors: Perkins J. S. , Beamish P. C.
Published: April 2011

This paper documents net entrapments of baleen whales in the inshore waters of Newfoundland and Labrador. The species involved are principally minke whales (Balaenoptera acutorostrata) and humpback whales (Megaptera novaeangliae). Finback whales (Balaenoptera physalus) are also caught in nets but far less frequently. The timing of these entrapments corresponds with the spawning season for capelin (Mallotus villosus) on the beaches around the province. The magnitude and implications of this problem, both to the whales and the fisherman, are assessed. Key words: baleen whales, net entrapments, mortality assessment, capelin, Balaenoptera acutorostrata, B. physalus, Megaptera novaeangliae
Physiology of Salinity-Dependent Naphthalene Toxicity in Fundulus heteroclitus
Authors: Levitan William M. , Taylor Malcolm H.
Published: April 2011

The influence of salinity on mortality in mummichogs, Fundulus heteroclitus, subjected to naphthalene and the physiological bases for the salinity-dependent mortalities were determined. Fish were acclimated to five salinities, 2, 8, 15, 23, and 33‰, and exposed to 6 and 4 mg naphthalene/L. At 4 mg/L, fish survival was greater at hypo- and near isoosmotic (15‰) salinities than at hyperosmotic salinities. At 6 mg/L, survival was generally greatest at 8 and 15‰ and decreased at the salinity extremes. In fish exposed to 4 mg naphthalene/L, uptake was more rapid at the iso- and hyperosmotic salinities than at hypoosmotic salinities and osmotic imbalance occurred only at hyperosmotic salinities. Serum cortisol levels and oxygen consumption rates increased at all salinities upon exposure to 4 mg naphthalene/L. However, the most significant increases in oxygen consumption rates occurred at hyperosmotic salinities. Thus, the greater naphthalene uptake, osmotic imbalance, and metabolic stress occurring at hyperosmotic salinities may contribute to the increased mortality of naphthalene-exposed fish acclimated to hyperosmotic salinities. Key words: toxicity, naphthalene, petroleum hydrocarbon, teleost, Fundulus heteroclitus, salinity, osmoregulation, uptake, oxygen consumption, stress
Plaque-Forming Cells and Humoral Antibody in Rainbow Trout (Salmo gairdneri) Induced by Immersion in a Yersinia ruckeri O-Antigen Preparation
Authors: Anderson D. P. , Roberson B. S. , Dixon O. W.
Published: April 2011

Rainbow trout (Salmo gairdneri) were exposed to the O-antigen of Yersinia ruckeri by various immunization regimens. The passive hemolytic plaque assay was used to show specific splenic plaque-forming cells (PFC) and passive hemagglutination demonstrated humoral antibody titers in fish injected with or immersed in the antigen preparations. Preceding antigen immersion with a 2-min immersion in either a 5.2 or a 2.6% NaCl solution did not affect the numbers of PFC or levels of antibody. Fish held for 2 min in ethyl m-aminobenzoate methanesulfonate (MS-222®) before antigen immersion showed no significant difference from the control fish. Dosage studies showed that the minimal concentration of antigen for induction of PFC by immersion was 5.0 μg/mL. Key words: plaque-forming cells, immunization, rainbow trout immersion, Yersinia ruckeri
Population Dynamics of Spiny Dogfish (Squalus acanthias) in British Columbia Waters
Authors: Wood C. C. , Ketchen K. S. , Beamish R. J.
Published: April 2011

An age-structure model that incorporates recent information regarding growth and reproduction has been developed to investigate the dynamics of spiny dogfish (Squalus acanthias) populations in British Columbia waters. Mechanisms for density-dependent regulation of abundance were evaluated on the basis of theoretical effectiveness and ability to predict observed patterns in simulations of the historical fishery. Compensatory change in the rate of natural mortality appears to be the principal mechanism for density-dependent response. The instantaneous rate of natural mortality at natural equilibrium was estimated to be 0.094 MSY for British Columbia waters is ~ 9000–11 000 t/yr. The minimum size at entry to the fishery has little effect on MSY. Sustained-effort, sustained-yield, and periodic fisheries were modeled to determine optimum harvesting strategies. Periodic fisheries were found to vary widely in feasibility and appear to be impractical from a management perspective whereas a sustained-effort fishery would ensure maximum stability. Key words: spiny dogfish, population dynamics, age-structure model, density-dependence, simulation model, commercial fishing strategies
Decrease in Mercury Content of Fishes in Ball Lake, Ontario, Since Imposition of Controls on Mercury Discharges
Authors: Armstrong F. A. J. , Scott D. P.
Published: April 2011

Weight, fork length, and white muscle mercury concentrations of walleye (Stizostedion vitreum vitreum), northern pike (Esox lucius), and lake whitefish (Coregonus clupeaformis) from Ball Lake, northwestern Ontario, were compared for 1971, 1972, and 1976. The lake had received mercury from 1962 to 1970; since then there have been increasingly rigorous controls. Adjusted mean white muscle mercury concentrations for walleye at the group mean length of 444 mm were 1.99, 2.71, and 1.39 mg/kg, respectively, for the three sample years. Corresponding values for pike 594 mm long were 5.05, 5.72, and 1.80 mg/kg. Whitefish values for 1972 and 1976 were 0.62 and 0.42 at 441 mm fork length. The changes are discussed in relation to the decreased input of mercury to the lake and it is suggested that mercury in suspension may be a controlling factor. Key words: mercury contamination, walleye, pike, whitefish, Ball Lake
Carbon Isotope Ratios of Particulate Organic Matter in the Gulf of St. Lawrence
Authors: Tan F. C. , Strain P. M.
Published: April 2011

Sixteen offshore surface samples within the Gulf of St. Lawrence show low δ13C values and are similar to eight offshore surface samples collected seaward of the Gulf of St. Lawrence. The δ13C surface values are consistent with δ13C values in plankton produced at the temperature found in the euphotic zone in the study area. Higher values are observed in four surface samples from the mouth of the St. Lawrence Estuary and probably result from high carbon demand during periods of high biological productivity. Lower values found in seven deep POC samples indicate changes in the nature of the POC caused by biological degradation of the organic matter. Significant differences (2–6‰) between the uniformly high δ13C values of the organic carbon in surface sediments and the low values of near-bottom water POC have been observed. The similarity between the δ13C values of surface water POC and the surface sediments suggest that surface water POC is an important source of organic carbon in surface sediments. Several observations of large vertical δ13C gradients in deep water POC suggest the presence of resuspended sediments 30–60 m above the sediment–water interface. Key words: particulate organic matter, carbon isotope ratios, isotope fractionation, sediment resuspension, sediment sources, Gulf of St. Lawrence
Quantitative Rights as an Instrument for Regulating Commercial Fisheries
Authors: Moloney David G. , Pearse Peter H.
Published: April 2011

A method of regulating commercial fisheries by providing fishing enterprises with transferable rights to harvest specific quantities of fish is described and analyzed in terms of its incentives for economic efficiency in harvesting, its administrative practicability, and its amenability to alternative objectives with respect to the division of resource rents between fishermen and the government. The regime proposed can, under certain realistic conditions, be expected to maximize resource rents and to permit the gains to be distributed flexibly. This approach is found to have certain superior characteristics over the main alternative proposals for rationalizing fishing. Key words: quantitative rights, fishermen's quotas, stinting, economic rationalization, licensing, regulation
Impact of Fishing on the Inshore Fishery of Lake Victoria (East Africa)
Authors: Marten Gerald G.
Published: April 2011

The inshore fishery of Lake Victoria has symptoms of severe overfishing. Curvilinear multiple regression analysis was used to examine the large variation in fishing effort, gear composition, and catches around the lake and suggest fishing practices that would give highest yields. The overfishing problem is due to the kind of gear in use and not to excessive fishing per se. Heavy fishing is often associated with the use of small mesh gillnets and seines to catch small fish such as Haplochromis, a practice that does not seem to justify the damage done to catches of the larger species by the same gear. The best strategy for maximizing the total tonnage yield is to fish optimally for the herbivorous genus Tilapia. This means using only the larger gillnets appropriate for Tilapia, as well as hooks, both at a very high fishing effort. The hooks capture large predators such as Bagrus, Clarias, and Protopterus, an abundant resource in themselves, and simultaneously appear to increase Tilapia yields indirectly by reducing losses of Tilapia to predators. Key words: Lake Victoria, ecosystem, succession, multispecies fishery, multigear fishery, fish yield, Africa, lake, lungfish, Tilapia, Haplochromis, catfish
Determining the Best Trade-Off Between Expected Economic Return and the Risk of Undesirable Events When Managing a Randomly Varying Population
Authors: Mendelssohn Roy
Published: April 2011

Conditions are given that imply there exist policies that "minimize risk" of undesirable events for stochastic harvesting models. It is shown that for many problems, either such a policy will not exist, or else it is an "extreme" policy that is equally undesirable. Techniques are given to systematically trade-off decreases in the long-run expected return with decreases in the long-run risk. Several numerical examples are given for models of salmon runs, when both population-based risks and harvest-based risks are considered. Key words: Markov decision processes, risk, salmon management, Pareto optimal policies, trade-off curves, linear programing
Evaluation of the Dual Beam Acoustic Fish Target Strength Measurement Method
Authors: Traynor J. J. , Ehrenberg J. E.
Published: April 2011

During surveys to assess fish stocks, the acoustic scattering properties of the fish population are required to obtain stock size measurements. The recently developed dual beam technique of target strength measurement has shown great promise as a method for fish target strength measurement. An improved dual beam target strength measurement system is described, and we report the application to a marine population of walleye pollock (Theragra chalcogramma). In addition, we discuss field calibration using a ping-pong ball as a standard target. Results of target strength measurements of the fish and ping-pong ball are compared with predicted values based on simulation analyses of the technique operating under the noise conditions observed in the field. The agreement between field results and theoretical predictions were quite good. Key words: hydroacoustic, walleye, pollock, dual beam, target strength measurement, fish assessment
Morphological and Ecological Divergence Within the Lake Whitefish (Coregonus clupeaformis) Species Complex in Yukon Territory
Authors: Bodaly R. A.
Published: April 2011

Two forms of lake whitefish (Coregonus clupeaformis species complex sensu McPhail and Lindsey [1970]) were found in each of five lakes in Yukon Territory. They are characterized by differences in gill raker counts. Low gill raker fish are benthic feeders and are found almost exclusively near the bottom while high raker fish are largely plankton feeders, being found throughout the lake water column. High raker fish have longer and more closely spaced gill rakers than low raker fish. They also have shorter life spans and mature earlier than low raker fish. Lakes supporting these sympatric populations of lake whitefish have no cisco populations. The low gill raker member of these sympatric populations seems to be equivalent to most other Yukon lake whitefish whereas the high raker member appears to be the unusual member of each sympatric pair. Key words: whitefish, lake, feeding, morphology, growth, divergence, Yukon Territory, sympatric populations
Laboratory Study of Cylindrical Sedimentation Traps
Authors: Lau Y. L.
Published: April 2011

Observations of the motion of fluid particles in cylindrical sedimentation traps showed that with an increase of the aspect ratio, there is also an increase in the Reynolds number below which neutrally buoyant droplets that were placed near the floor of the trap would remain in the bottom layer. The dependence of the fluid motion on these two dimensionless variables was demonstrated using traps of different diameters. For single cylindrical traps, the experimental results can be used to obtain estimates of the Reynolds number below which resuspension of settled material would not be expected to occur. Key words: sedimentation trap, aspect ratio, Reynolds number, limnological instrument
Overdominance of a Muscle Protein (Mp-1) Locus in the Japanese Oyster, Crassostrea gigas (Ostreidae)
Authors: Buroker N. E.
Published: April 2011

A microgeographical population genetic study of the Japanese oyster, Crassostrea gigas, revealed a case of overdominance for a muscle protein (Mp-1) locus. This locus consists of a two allele polymorphism. A study of the relative "fitness" of the three genotypes (Mp-1105/105, Mp-1105/100, and Mp-1100/100) revealed a heterozygote superiority in the segment of the oyster population at the lowest tidal level (+ 1.2 m). In segments of the population at higher tidal heights (i.e. + 1.8 and + 2.4 m), there appears to be a selective advantage for Mp-1105 allele since the highest "fitness" values belong to the Mp-1105/105 genotype. Since oysters do not appear at the field station lower than 1.2 tidal m, it could not be determined if the Mp-1100 allele had a selective advantage at tidal levels lower than 1.2 m. However, the Mp-1105 allele possibly exhibits a selective advantage in the subtropical marine environment of southern Japan, while the Mp-1100 allele is favored in the temperate marine environment of northern Japan. This suggests perhaps that a micro- and macrogeographical cline in gene frequency exists for the Mp-1 locus due to a thermal gradient. Key words: Japanese oyster, Crassostrea gigas, population genetic study, overdominance, heterozygote superiority, Mp-1 locus, micro- and macrogeographical cline, thermal gradient, tidal height, latitude
Indicators of Phosphorus and Nitrogen Deficiency in Five Algae in Culture
Authors: Healey F. P. , Hendzel L. L.
Published: April 2011

Five freshwater algae (Chlamydomonas reinhardi, Scenedesmus quadricauda, Anabaena variabilis, Pseudoanabaena catenata, and Cryptomonas erosa) were grown in batch culture without nutrient limitation and with various degrees of P and N limitation. They were analysed for several aspects of composition and some metabolic activities of potential use as indicators of nutrient deficiency to aid in establishing values indicative of the presence or absence of nutrient deficiency. Ratios of N/C, P/C, N/P, protein/C, carbohydrate/C, and protein/carbohydrate most clearly differentiated between no, P, and N deficiency. The initial saturated rate of phosphate uptake, P debt, and alkaline phosphatase activity increased distinctly in P deficiency in some of the algae but not in others. Similarly, the initial saturated rate of ammonium uptake and N debt rose in some but not all N-deficient algae. Cryptomonas erosa tended to form walled resting cells (cysts) during growth into P or N deficiency. Key words: algae, nitrogen, nutrient deficiency, nutrient uptake, phosphatase, phosphorus
Fish Viruses: A Double-Stranded RNA Icosahedral Virus from a North American Cyprinid
Authors: Plumb J. A. , Bowser P. R. , Grizzle J. M. , Mitchell A. J.
Published: April 2011

A previously unreported virus disease of cultured golden shiners (Notemigonus crysoleucas) is described. The condition is called golden shiner virus (GSV) disease. The virus is icosahedral, measures approximately 70 nm, is ether and heat resistant, stable at pH 3, 7, and 10, and appears to have a double stranded RNA core. It was not neutralized by infectious pancreatic necrosis virus specific antiserum. GSV causes syncytial like cytopathic effect in fathead minnow cells but not brown bullhead, rainbow trout gonad (RTG-2) or channel catfish ovary cells. Severe mortalities in golden shiner culture ponds do not appear to be associated with GSV infections. Key words: fish viruses, RNA virus, fish pathology, fish cell cultures, Cyprinidae, golden shiner
Detection of Bacterial Kidney Disease in Wild Salmonids in the Margaree River System and Adjacent Waters Using an Indirect Fluorescent Antibody Technique
Authors: Paterson W. D. , Gallant C. , Desautels D. , Marshall L.
Published: April 2011

The indirect fluorescent antibody technique demonstrated the enzootic nature of bacterial kidney disease in 224 of the 605 wild salmonids sampled from the Margaree River system and some adjacent waters. Asymptomatic infections were observed in 33.4% of 456 Atlantic salmon (Salmo salar) parr and 35.1% of 37 returning adults in samples taken from the source of the Margaree River to and including saltwater areas off the coast. Key words: kidney disease, Atlantic salmon, wild, distribution, fluorescent antibody
Influence of Detritus upon Colonization of Stream Invertebrates
Authors: Peckarsky Barbara L.
Published: April 2011

The effect of introduced detritus on the colonization of cages by benthic invertebrates within the substrate of two stony streams was examined. Pairs of substrate-filled screen cages were buried to a depth of 10–20 cm within the substrate of Otter Creek, Sauk County, Wisconsin, and the East River, Gunnison County, Colorado. Variously conditioned coarse particular detritus was added to experimental cages, and no detritus to control cages. Total macroinvertebrates and total detritivores did not preferentially colonize cages enriched with detritus. Shredders showed higher colonization of experimental cages during fall trials using leaves conditioned by inoculation with microbial flora from Otter Creek. This observation reflects habitat choice by availability of high-quality food for shredders during the season of their greatest abundance. Shredders preferentially colonized detritus-enriched cages during combined summer trials in the East River and during summer trials when leaves were not microbially conditioned before use. Shredders in this high-altitude stream showed opportunistic colonization of introduced large-particle detritus where natural allochthonous matter was less readily available.Key words: detritus, streams, macrobenthos colonization, leaf conditioning, shredders, experimental manipulation
Attempts to Acclimate Embryos and Alevins of Atlantic Salmon, Salmo salar, and Rainbow Trout, S. gairdneri, to low pH
Authors: Daye P. G.
Published: April 2011

Embryos and alevins from three strains of Atlantic salmon, Salmo salar, and one strain of rainbow trout, S. gairdneri, were tested for low pH tolerances following exposures at several pH values. Acclimation to low pH, judged by resistance adaptation, did not occur. Alevins had 10 000 min LL50's for pH of about 4.3 for all strains and were less tolerant than embryos.Key words: pH, acclimation, Atlantic salmon, rainbow trout, embryo, alevin
Prey Location Volume of a Planktivorous Fish: A New Measure of Prey Vulnerability
Authors: Luecke Chris , O'Brien W. John
Published: April 2011

The probability that bluegills (sunfish) (Lepomis macrochirus) will locate prey varies with distance and position of the prey in three-dimensional space. Location ability is greatest in the hemisphere directly ahead of the fish. The probability that bluegills will locate prey declines steadily when prey are placed to the side, behind, or directly above or below the fish. Bluegills could locate prey farthest when placed slightly to the side of the area directly in front of the fish. Under all experimental conditions, fish could locate prey, at least some of the time, at distances considerably farther than suggested by reported reactive distance measurements, indicating that the water volume searched by bluegills has generally been underestimated.Key words: planktivorous fish, zooplankton, reactive distance, location volume, predator search
Improvements in Quantifying the Phosphorus Concentration in Lake Water
Authors: Prepas E. E. , Rigler F. H.
Published: April 2011

Vertical and horizontal patterns in limnetic phosphorus concentrations ([P]) were detected in an oligotrophic lake by dividing the total phosphorus pool into two fractions: dissolved and particulate matter smaller than 250 μm (smaller fraction) and particulate matter larger than 250 μm (larger fraction). The smaller fraction was estimated from samples collected with a water bottle, and the larger fraction was estimated with tow net samples taken at several stations and to various depths. Our samples were digested with potassium persulfate which gave less variable results than other acid digestion techniques. The average variance associated with the mean [P] (n = 3) for samples collected and analyzed according to our procedure was less than 0.05 mg P/m3. During summer stratification there was a consistent metalimnetic maximum in the smaller fraction, and there were small but significant differences in the concentrations found at two stations less than 1 km apart. During the same period the larger fraction was a significant portion (14–28%) of the phosphorus pool in the epilimnion which varied from 3 to 5 m in depth. It was a relatively constant portion of the phosphorus in the trophogenic zone (0–10 m) and in the 0- to 20-m portion of the water column i.e. 10–14% and 7.3–8.8%, respectively. In a separate experiment it was shown that by removing the larger fraction, the average variance associated with the mean [P] was reduced from 1.0, to 2.4 × 10−2 mg/m3. This reduction occurred because the larger fraction contained zooplankters with relatively high but variable amounts of phosphorus, and which occur in densities too low to be adequately sampled with the smaller fraction.Key words: phorphorus, lakes, phosphorus in zooplankton
Determination of Protein Digestibility in Atlantic Cod (Gadus morhua) with Internal and External Indicators
Authors: Lied E. , Julshamn K. , Braekkan O. R.
Published: April 2011

Chromium(III)-oxide added to feed was determined by flame atomic absorption spectrophotometry in the same Kjeldahl digest as protein (N × 6.25). The recovery was 98.0% compared with only 40.0% using nitric/perchloric acid digestion. Samples of apparent indigestible protein in Atlantic cod (Gadus morhua) could be collected from the middle and distal part of the intestine 24 h after feeding a diet based on fillets of saithe (Pollachius virens). The level of reference substance and the apparent digestibility of protein indicated that feces samples from the rectum representing the feed could not be obtained until 72 h after the first feeding. Water-insoluble protein from the intestine and rectum accounted for 35–47% and 27%, respectively, of the total dry matter protein. Postdefecation loss of water-soluble nitrogenous components would therefore cause overestimation of protein digestibility. Chromium(III)-oxide and titanium(IV)-oxide were equivalent as external indicators. With titanium(IV)-oxide as indicator substance, calcium, iron, and zinc present in the feed were examined as internal reference substances. The gastric ratios of protein over calcium or zinc were compared with the corresponding ratios in the distal part of the intestine. The apparent protein digestibility agreed with the corresponding estimates obtained by titanium(IV)-oxide. Estimates of protein digestibility from capelin (Mallotus villosus) predating cod caught at sea using the gastrointestinal levels of calcium and zinc as internal reference substances corresponded well with estimates from experiments with cod fed whole capelin with titanium(IV)-oxide as external reference substance. The estimates indicate that samples of feces should be taken from the distal part of the intestine excluding the rectum. Because of large differences between individuals, a sufficient number of fish should be included in digestibility studies.Key words: cod, protein digestibility, digestibility indicators, feces sampling
Variation of Hepatic Ethoxycoumarin O-de-ethylase Activity with Body Weight and Other Factors in Brook Trout (Salvelinus fontinalis)
Authors: Addison R. F. , Willis D. E.
Published: April 2011

Data from several previous experimental studies of hepatic mixed function oxidase (MFO) activity were reexamined to study the possible relationship between ethoxycoumarin O-de-ethylase activity and body weight and other factors in "uninduced" brook trout (Salvelinus fontinalis). Weight-specific O-de-ethylase activity was inversely related to body weight; regression of the log transformation of the total hepatic O-de-ethylase activity on log liver weight yielded a regression coefficient of 0.850 ± 0.047 close to the value of ~0.75 expected for a relationship based on overall metabolic rate. The regression coefficient was significantly higher in males than in females. Multiple regression analysis showed O-de-ethylase activity to be positively correlated with both microsomal protein and cytochrome P-450 content. The data confirm that size (or age) is a factor to be eliminated in any biological effects monitoring program based on MFO assays.Key words: mixed function oxidases, ethoxycoumarin O-de-ethylase, brook trout, Salvelinus fontinalis; hepatic mono-oxygenases
Relationship Between Thickness of Daily Growth Increments in Sagittae and Change in Body Weight of Sockeye Salmon (Oncorhynchus nerka) Fry
Authors: Wilson Kenneth H. , Larkin P. A.
Published: April 2011

Sixty-four laboratory-reared sockeye salmon (Oncorhynchus nerka) fry were marked to enable identification as individuals. Each was weighed initially on June 6 or 8, 1979; and again on July 6; and surviving fish were weighed a third time on July 20. After the final weighing, sagittae were removed and a standard otolith radius, corresponding to each weight, was determined by counting back from the otolith edge the appropriate number of daily increments. The regression of ln otolith radius on ln fish weight was linear, with r2 = 0.92, demonstrating a relationship between mean thickness of a daily increment in sagittae, and mean daily change in weight of the fry. Using this regression line, previous weights were back calculated from corresponding otolith radii with errors in the order of 15%.Key words: otoliths, daily growth increments, back calculation, sockeye salmon
Carbon Inputs to Bivalve Mollusks: A Comparison of Two Estuaries
Authors: Incze Lewis S. , Mayer Lawrence M. , Sherr Evelyn B. , Macko Stephen A.
Published: April 2011

Corresponding trends in δ13C values for particulate organic carbon (POC) and the tissues of several filter-feeding bivalve mollusks in the Sheepscot estuary, Maine, indicate assimilation of terrestrial organic matter by these estuarine organisms. An adjacent estuary, the Damariscotta, of similar morphology but receiving little river input shows no such isotope change in either POC or bivalves, but rather a domination by marine isotopic values. Geographically localized or species-specific departures from these trends appear to be related to two mechanisms: (1) the influence of locally abundant, isotopically distinct, aquatic macrophytes in an area of seasonally low flushing; (2) surface-deposit feeding on benthic microalgae with anomolously high δ13C values.Key words: δ13C, Mytilus edulis, Mya arenaria, Macoma balthica, POC, estuarine comparisons, bivalve feeding
Spawning Behavior and Early Life History of Pink Salmon (Oncorhynchus gorbuscha) in the Great Lakes
Authors: Kwain Wen-hwa
Published: April 2011

Pink salmon (Oncorhynchus gorbuscha) from a single introduction to Lake Superior in 1956 have reproduced naturally and expanded into all the Great Lakes. Pink salmon feed at or near the surface as they approach spawning streams and some can still be found with food in the stomach on the spawning bed. Spawning behavior of these freshwater pink salmon is similar to that of marine stocks. Fecundity was 1060 ± 229 (24) per fish and total weight averaged 0.68 kg. Total mortality of embryos to 50% hatch ranged from 67 to 87% at five test temperatures (7, 9, 11, 13, 15 °C); 15 °C is considered to be the upper limit for freshwater pink salmon incubation. Juveniles moved downstream only at night and all juveniles usually took a month to complete this movement. Mean preferred temperature for pink salmon up to 36 wk old was 10 °C. Substantial numbers of pink salmon progeny of the 1975 year-class, which entered the Michipicoten River on Lake Superior to spawn in 1977 survived to, and matured at, each age from II to IV yr in a freshwater laboratory environment.Key words: pink salmon, feeding, spawning behavior, fecundity, incubation, emigration, preferred temperature, early life history, age IV, late maturation
Temperature and Scale Size Errors in the Use of [14C]Glycine Uptake by Scales as a Growth Index
Authors: Smagula Carl M. , Adelman Ira R.
Published: April 2011

Measurement of glycine uptake by largemouth bass (Micropterus salmoides) scales at several acclimation (14, 20, and 26 °C) and incubation (14–32 °C, 3 °C increments) temperatures revealed significant interaction between these factors (P < 0.005). Therefore, comparison of uptake data from several acclimation groups could not be made at any arbitrary "standard" incubation temperature without introducing error. An error-free scale incubation criterion was tentatively proposed as optimum incubation temperature for each fish acclimation temperature, determined from a laboratory response surface model. Incubation temperature of maximum uptake was associated with temperature of maximum body growth of bass which suggests that uptake may be integrated with growth. Use of scale weight to express uptake relative to scale size will probably introduce systematic error, and scale area should provide the "best" measure for normalization of uptake data. Glycine uptake by 14, 20, and 26 °C acclimated scales was linearly related to body growth on a loge–loge basis (P < 0.05); however, within acclimation groups significant correlation was not noted.Key words: acclimation temperature, incubation temperature, response surfaces, largemouth bass, Micropterus salmoides
Measurements of Growth and Consumption of Sauger (Stizostedion canadense): Implication for Fish Energetics Studies
Authors: Minton Joseph W. , McLean Richard B.
Published: April 2011

The energy budget of sauger (Stizostedion canadense), in Watts Bar Reservoir, Tennessee, was studied over a 17-mo period. Field determinations of consumption and laboratory determinations of metabolism were incorporated into the balanced energy equation of Winberg to predict growth in energy value of sauger in age-classes I+ and II+. The equation included energetic costs of specific dynamic action and the metabolic efficiency penalty of metabolizing body energy stores. Observed and predicted growth during the warm months, March through October, agreed within 2.5–9.6% for the I+ and II+ age-classes, respectively. Observed and predicted growth over the winter for the only age-class modeled, the I+, did not agree. High food consumption during winter did not result in the amount of growth expected, suggesting that the physiological assumptions of the balanced energy equation are invalid for describing the winter energetics of sauger. We emphasize the potential error in inferring consumption from growth and metabolism.Key words: sauger, Stizostedion, bioenergetics, feeding, growth, modeling
Homing by Canada's West Coast Herring to Management Units and Divisions as Indicated by Tag Recoveries
Authors: Hourston A. S.
Published: April 2011

The change from a fishery for reduction to meal and oil to one primarily for roe resulted in major shifts in the herring fishing grounds on Canada's west coast. To meet management needs for the new fishing pattern, the former stock concept of seven "populations" was revised into 35 "management units." Reanalysis of tag recovery data for the period 1937–67, in terms of the 22 management units represented, showed a degree of homing between 66 and 96% for 18 of these management units. This is comparable to the homing displayed by the seven former populations (54–84%) estimated from essentially the same data base. Homing to some of the more isolated management units was comparable to that for the six major divisions of the coast (77–94%), as currently defined. Stevenson's (1954) conclusion "… the herring of British Columbia tend to form a series of integrating populations" is supported by the present analysis.Key words: Clupea harengus pallasi, tagging, homing, stocks, populations
Zooplankton Diversity and Biomass in Recently Acidified Lakes
Authors: Confer John L. , Kaaret Thomas , Likens Gene E.
Published: April 2011

Ten small headwater lakes in the Adirondack Mountains of New York State and 10 in the White Mountains of New Hampshire were examined for possible effects of acidification on zooplankton. The results showed that acidification, or some close correlate, had a significant negative effect on zooplankton diversity and biomass. A loss of 2.4 species of zooplankton and 22.6 mg dry wt/m2 was correlated with each unit decrease in pH. These results, in contrast to some previous work, show a continuous decrease in diversity and biomass over the entire range of pH in the sampled lakes, 4.5–7.2. Cladocera, with the exception of Holopedium and Polyphemus, and Epischura lacustris, Mesocyclops edax, and Cyclops scutifer, were abundant at higher pH values but rare or absent at pH values less than 5. Diaptomus minutus was predominant at pH values less than 5.Key words: acid rain, lakes, Adirondack Mountains, White Mountains, zooplankton, Cladocera, Epischura, Mesocyclops, Cyclops, Diaptomus