bluuebunny/crossref_metadata_2025 huggingface dataset:
Production and Population Dynamics of the Crayfish Orconectes virilis in Three Michigan Lakes
Authors: Momot Walter T. , Gowing Howard
Published: April 2011

Fluctuations in mortality rather than in growth rates produced most of the year-to-year differences in biomass accumulation of three different populations of the crayfish Orconectes virilis. Yearly biomass changes resulted from density-dependent control of mortality and fecundity during certain portions of the life cycle. Density-dependent changes in mortality rates controlled population size for adults in all lakes and for young-of-the-year in two of the three study lakes. Growth rates were much less responsive to fluctuating densities. Disparity between the number of ovarian and attached eggs increased as density of age I+ crayfish increased. This provided a strong density regulator on fecundity. Differences occurred in the number of recruits produced by a brood stock that survive to the end of the first growing season in the various lakes. Yet the number of females surviving to reproductive age 2 yr later was strongly regulated. Strong population regulation produced two female recruits of breeding age for every two–six parental breeding females. The high biomass and production levels of crayfish discovered in West Lost Lake in 1962–63 also occurred in the other area lakes. Higher but variable levels of recruitment resulted in larger standing crops and production in West Lost lake. This resulted from less effective density controls on the mortality rates of younger age-groups in that lake. Despite great variation in biomass of from 46 to 213 kg/ha and annual production from 60 to 142 kg/ha, the annual turnover ratio of the biomass was found to vary only between 0.94 and 1.53. Key words: crayfish, Orconectes virilis, population dynamics, annual production, Michigan lakes
Results of an Experimental Fishery on the Crayfish Orconectes virilis
Authors: Momot Walter T. , Gowing Howard
Published: April 2011

Populations of the crayfish Orconectes virilis were exploited using the Paulik–Bayliff modification of the Ricker model in two small lakes. After harvesting with traps at maximum sustained yield (MSY) for 3 yr, fishing effort was increased fourfold in one lake, West Lost, for two successive seasons, while in North Twin Lake it was not changed. In West Lost yields were stable during MSY; yields increased with overexploitation, but growth and recruitment declined. Distortions occurred in the age composition of the catch. In North Twin this pattern was repeated except that in 1975 the catch dropped drastically even though fishing effort had not been increased. Because of declining recruitment, North Twin was actually overfished by about 20% in 1974 and greatly overfished in 1975. Decreased recruitment in both lakes can be attributed to two factors: (1) a decreased survival of hatchlings in both lakes due to a decline in nursery habitat; as a consequence the stock-recruitment relationship was altered; and (2) an increase in the density of age I (subadult) females due to the selective fishery for males; as a result density-dependent mechanisms lowered the survival of females from age I to II, producing fewer spawning adults. However, the high density of these age II females at age I decreased the egg production per adult female. The changes in the productivity of the lakes for crayfish during the period of exploitation were related to loss of microhabitat for hatchlings. This change in productivity offset the benefits of MSY management and resulted in a drastic drop in stocks when deliberate overfishing took place. West Lost gave good yields prior to its certain collapse. Yields in weight were an unreliable indicator of the impact of the fishery. Key words: crayfish, Orconectes virilis, potential yield, production, recruitment, stock assessment, experimental fishery
Changes in Specific Gravity of Atlantic Salmon (Salmo salar) Alevins
Authors: Peterson R. H. , Metcalfe J. L.
Published: April 2011

The specific gravity of Atlantic salmon (Salmo salar) alevins decreases during posthatching development from 1.067 at hatching to 1.044 at terminal yolk resorption. The water content of the embryo is ca. 84% throughout posthatching development while that of the yolk is ca. 56%. Therefore, as the embryo grows at the expense of yolk material, the water content of the alevin increases during development. This increase in water content can entirely account for the observed change in specific gravity. Alevins reared at lower temperatures have a higher specific gravity for any given embryonic length, implying the presence of more yolk reserves. Splake alevins reared in a hatchery tray had a lower specific gravity at a given length than did alevins reared in gravel or artificial turf substrates. Measurements of specific gravity in conjunction with length measurements during development may be useful in comparing different incubation conditions. Key words: specific gravity, Atlantic salmon, alevin, yolk, embryo, water content, temperature, splake
Recent Invasion of a Red Alga (Bangia atropurpurea) in Lake Michigan
Authors: Lin C. Kwei , Blum John L.
Published: April 2011

Bangia atropurpurea was first found on the southwestern shore of Lake Michigan in 1968; by 1976 it had covered suitable substrates on the southern two thirds of the lakeshore. Optimal vegetative growth occurred above the low waterline during the spring and fall, especially near harbor areas. Vegetative growth is initiated from either perennating basal cells or monospores. Bangia contained extraordinarily high concentrations of bromine and zinc, suggesting it requires relatively high levels of halogens and trace metals, which are present in runoff waters and contaminated harbors. Key words: Bangia, invasion, Lake Michigan, halogens, trace metals, algal zonation
Farming the Edge of the Sea.
Authors: Bardach John E.
Published: April 2011

not available
Enhancement of Autotrophic Production by Nutrient Addition in a Coastal Rainforest Stream on Vancouver Island
Authors: Stockner John G. , Shortreed K. R. S.
Published: April 2011

In 1976 streamside nutrient-enrichment experiments were conducted using wooden troughs. Tripling of the PO4-P concentration, with or without a similar increase of NO3-N, increased algal biomass on the troughs by 8 times after 35 days. Increasing NO3-N alone had no appreciable effect on algal growth. A sloughing of algal biomass in August 1976 is believed to have been due to the instability of the heavy algal mat on the troughs and to the very poor light conditions that prevailed throughout August. Visual observation indicated that the relatively heavy algal population in Carnation Creek rapidly declined concurrent with the decline in the troughs. The percentage of diatoms in the algal assemblage remained the same in all troughs, and Fragilaria vaucheriae replaced Achnanthes minutissima as dominant on the phosphorus enriched trough. No shift to green or blue-green algal dominated assemblages occurred despite alteration of the N:P ratio. The dynamics of species succession, distribution, and growth, with and without nutrient addition, are discussed. Key words: stream fertilization, autotrophic production, algal succession, N:P ratio, algal distribution, rainforest, algal biomass, diatoms, blue-green algae
Direct Potentiometric Measurement of Chloride In Fisheries Products by Ion-Selective Electrode Analysis
Authors: Whyte John N. C. , Englar John R.
Published: April 2011

Chloride in thawed fish, smoked fish, and fish roe was estimated by direct application of a combination chloride electrode to the respective tissues. The response potentials from the combination chloride electrode were correlated with the known concentrations of chloride in the tissues, as estimated by alkali fusion and subsequent argentometric titrations with an iodide-selective electrode, to provide fish calibration graphs. This ion-selective electrode technique was shown to be reliable, simple, and convenient. Key words: chloride determination, fish chloride, roe chloride, ion-selective electrodes
Feeding-Behavior Repertoire of the Alewife, Alosa pseudoharengus, and the Ciscoes Coregonus hoyi and C. artedii
Authors: Janssen John
Published: April 2011

Particulate feeding, where fish orient to and take prey one at a time, is shown by the alewife, Alosa pseudoharengus, and the ciscoes Coregonus hoyi and C. artedii. Specialized particulate feeding is found in ciscoes and alewives for capturing strongly swimming prey such as Mysis relicta and calanoid copepods. This involves simultaneous darting and sucking. Alewives filter feed by swimming with the mouth fully agape for 0.5–2 s while driving hard with the tail. Ciscoes do not filter feed, but they and alewives display gulping behavior where fish open and close the mouth 2–3 times/s, do not drive hard with the tail, and may take more than one prey per gulp. The alewife has difficulty feeding near or on the bottom. The ciscoes feed easily on or near the bottom and will also take buried prey. Key words: Alosa pseudoharengus, Coregonus hoyi, C. artedii, feeding behavior, Great Lakes, Lake Michigan
Medusa Predation and Plankton Dynamics in a Temperate Fjord, British Columbia
Authors: Huntley M. E. , Hobson L. A.
Published: April 2011

A second spring bloom, dominated by the diatoms Skeletonema costatum and Chaetoceros spp., has been repeatedly observed in a temperate fjord on southern Vancouver Island, B.C. Ammonia, possibly regenerated by herbivorous zooplankton, formed the principal nitrogen supply for the second spring bloom. High production of phytoplankton and zooplankton during the first spring bloom resulted in plentiful food for polyps of the leptomedusa, Phialidium gregarium, which then produced a large quantity of medusae (> 110 mg dry weight∙m−3). Medusa predation on zooplankton reduced herbivore grazing pressure, thus permitting development of the second spring bloom. Continuing predation by P. gregarium reduced the prey population to such an extent that medusa standing stock declined to 5% of its maximum value. The second spring bloom probably ended due to nitrogen limitation, and when medusa biomass declined herbivore and ammonia concentrations began to rise. Results indicate that the release of herbivore grazing pressure due to predation can stimulate phytoplankton growth. Key words: phytoplankton ecology, phytoplankton physiology, zooplankton grazing, zooplankton predation, Phialidium gregarium, Skeletonema costatum
Biochemical and Biophysical Perspectives in Marine Biology: Volume I.
Authors: Giles M. A.
Published: April 2011

not available
Larvae of the North American Caddisfly Genera (Trichoptera).
Authors: Flannagan John F.
Published: April 2011

not available
A Simple Fish-Population Model Including Environmental Influence, for Two Western Atlantic Shelf Stocks
Authors: Loucks R. H. , Sutcliffe Jr. W. H.
Published: April 2011

For several Scotian Shelf and Gulf of Maine stocks, correlations have been observed between ocean temperatures, subsequent fish catches, and fishing effort. We consider a simple fish-population model relating these elements. We suggest that variation in ocean climate triggers corresponding fluctuations in fish stock–recruitment and subsequent abundance and catch. Two pathways between abundance and catch are recognized: (1) catch is simply proportional to abundance (direct influence); and (2) in some cases at least, fishermen traditionally have sensed the abundance of a stock and adjusted their fishing effort accordingly; therefore, in periods of less favorable climate for a stock, catch would diminish indirectly because of reduced or "responsive" effort. In such cases, where the fishermen act to stabilize the stock, fishing effort and fish catch are correlated with ocean climate. In any case, ocean climate and "responsive" effort merit consideration as potentially significant factors in population models of these stocks. Key words: fish-population model, effort, recruitment, abundance, cod, yellowtail flounder
Feeding Response of Atlantic Salmon (Salmo salar) Alevins in Flowing and Still Water
Authors: Rimmer D. M. , Power G.
Published: April 2011

Atlantic salmon (Salmo salar) alevins presented with lake zooplankton in still water readily consumed prey items, but only if the prey were nearby and moving. Feeding was initiated from the bottom or from midwater, but no search or pursuit behavior was noted. Stomach analyses of alevins exposed to lake zooplankton assemblages for 3 h in still and flowing (7.2 cm∙s−1) water revealed that the two groups consumed similar diets, but that the still-water group had a greater total food consumption. We conclude that for alevins to feed successfully, food need not be carried in a water current, but that motion of the prey is necessary. This motion can be provided by water current or by the prey. The role of prey motility in the feeding of young salmonids is briefly discussed. Key words: Atlantic salmon, alevins, feeding, water current
Effect of Graded Levels of Supplemental Ascorbic Acid in Practical Diets Fed to Rainbow Trout (Salmo gairdneri)
Authors: Hilton J. W. , Cho C. Y. , Slinger S. J.
Published: April 2011

Deficiency symptoms, including anorexia, lethargy, lying prostrate at the bottom of the tank, scoliosis, and lordosis, were noted 20 wk after the start of the experiment in rainbow trout (Salmo gairdneri) held at 15 °C and fed a diet with no supplemental ascorbic acid. The apparent requirement was 40 mg/kg of supplemental ascorbic acid; however, the amount added to trout diets should be in excess of this level due to processing and storage losses and other factors. The ascorbic acid requirement for rainbow trout appears to vary with the age and rate of growth of the trout in that the requirement is higher in young fish. Ascorbic acid was noted to function in the iron metabolism of rainbow trout. Liver and spleen iron levels were correlated with the ascorbic acid level in the diet and suggest either a redistribution of iron stores due to impaired release of iron from reticuloendothelial stores or an increase in the efficiency of intestinal iron absorption. Scorbutic trout developed a gradual but progressive anemia. Key words: ascorbic acid, rainbow trout, vitamin requirement, iron, mineral metabolism, anemia
The Biology of Diatoms.
Authors: Healey F. P.
Published: April 2011

not available
Behavior of Age-Specific, Density-Dependent Models and the Northern California Dungeness Crab (Cancer magister) Fishery
Authors: Botsford Louis W. , Wickham Daniel E.
Published: April 2011

A continuous time and age model which reflects the effect of older age-groups on mortality in young is presented. The conditions under which this model is unstable and the characteristics of solutions under various conditions are examined. Results obtained are related to results obtained by others from stock–recruitment models. Analytical expressions for the period of oscillations, the effect of fishing all age-classes, and the effect of the slope of the stock–recruitment curve at the replacement point support earlier simulation results. The effect on the model of size-selective fishing is shown to be a decrease in the stability of the population in some cases. These results are demonstrated with a model that approximately reflects the Dungeness crab (Cancer magister) population in northern California. The cyclic behavior of this population is similar to an unstable mode of the model. Conditions under which this mode arises are derived and potential causes of decreased stability, among which is fishing, are examined. Key words: fishery, model, stability, Dungeness crab, age-specific, density-dependent, stock–recruitment, cannibalism, Carcinonemertes
Hyperosmotic Infiltration: Factors Influencing Uptake of Bovine Serum Albumin by Rainbow Trout (Salmo gairdneri)
Authors: Fender D. C. , Amend D. F.
Published: April 2011

Infiltration of bovine serum albumin (BSA) into the blood of rainbow trout (Salmo gairdneri) by hyperosmotic infiltration (HI) was studied by varying the osmotic pressure, immersion time, pH, temperature, stress, vacuum, and fish size. Compared with uptake of BSA from water solutions, about 1400 mosM (4.51%) NaCl was required to increase the plasma level of BSA during a 3-min immersion. Higher osmotic pressures resulted in higher plasma-BSA levels, but the uptake of BSA was limited by the length of time that fish could tolerate the high NaCl concentration. Comparison of immersion time in the solutions of the two-step HI method showed that maximum infiltration occurred after a 2–3-min bath in the 5.32% NaCl solution and only 30 s in the 2% BSA solution. Alkaline solution (pH 9) enhanced BSA uptake in the one-step method, but the two-step method was most effective if the NaCl solution was pH 9 and the BSA solution pH 5. BSA uptake was directly proportional to water temperature from 4 to 20 °C. Preimmersion stress, and injection of 10 μg epinephrine, reduced BSA uptake; vacuum and fish weight (2–8 g) had no effect on uptake of BSA. Hyperosmotic infiltration may be useful for mass delivery of vaccines, pharmaceuticals, and other materials. Key words: hyperosmotic infiltration, bovine serum albumin, osmotic pressure, vaccines, immersion, rocket immunoelectrophoresis
Fecundity Changes in Exploited Populations of Lake Whitefish (Coregonus clupeaformis) and Lake Trout (Salvelinus namaycush)
Authors: Healey M. C.
Published: April 2011

This report considers the possibility that exploited populations of lake whitefish (Coregonus clupeaformis) and lake trout (Salvelinus namaycush) may show increased individual fecundity. Average fecundity of both species in three exploited lakes varied significantly between 1972 and 1976, while fecundity in an adjacent unexploited lake did not vary. Changes in the fecundity of whitefish and trout in the exploited lakes were not clearly related to the pattern and intensity of exploitation, but fecundity of both species increased in all exploited lakes after exploitation, with trout showing the greater response. Key words: fecundity, lake whitefish, lake trout, exploitation, northern Canada
Effects of Aroclor® 1248 and 1260 on the Fathead Minnow (Pimephales promelas)
Authors: DeFoe D. L. , Veith G. D. , Carlson R. W.
Published: April 2011

Fathead minnows were exposed to Aroclor® 1248 and 1260 in flow-through bioassays to determine the acute (30-d) and chronic (240-d life cycle) effects on the larvae and adults, as well as the bioconcentration of the mixtures of PCBs in the fish. Newly hatched larvae (< 8 h old) were the most sensitive; the calculated 30-d LC50 was 4.7 μg/L for Aroclor 1248 and 3.3 μg/L for Aroclor 1260. Reproduction in fathead minnows occurred at concentrations as high as 3 μg/L for Aroclor 1248 and 2.1 μg/L for Aroclor 1260, concentrations that significantly affected larval survival. The 20% reduction in the standing crop in the second-generation fish at concentrations as low as 0.4 μg/L was due to the death of the larvae soon after hatching. The bioconcentration factor for PCBs was independent of the PCB concentration in the water; in adult females at 25 °C it was ~ 1.2 × 105 for Aroclor 1248 and 2.7 × 105 for Aroclor 1260. Females accumulated about twice as much PCBs as the males because of the greater amount of lipid in the female. Exposed fish placed in untreated Lake Superior water eliminated < 18% of the body burden after 60 d. Key words: PCBs, bioassay, bioconcentration, chronic toxicity, embryo-larval, depuration
Fish Cell Lines: Comparisons of CHSE-214, FHM, and RTG-2 in Assaying IHN and IPN Viruses
Authors: Kelly R. K. , Souter B. W. , Miller H. R.
Published: April 2011

The rainbow trout, Salmo gairdneri, gonad (RTG-2) cell line was more sensitive to lytic infection by infectious pancreatic necrosis virus (IPNV) than was the fathead minnow, Pimephales promelas, (FHM) cell line in laboratory and field studies. Laboratory investigations with known strains of IPNV (VR 299 and Buhl) also indicated that the cytopathic response in IPNV-infected chinook salmon, Oncorhynchus tshawytscha, embryo (CHSE-214) cells was greater than in infected FHM cells. In contrast, titration experiments with standard infectious hematopoietic necrosis virus (IHNV) isolates (Oregon and Cedar River) showed that the FHM cells were more sensitive to destructive infection by IHNV than was either of the salmonid cell lines (RTG-2, CHSE-214). Key words: fish cell culture, infectious pancreatic necrosis virus, infectious hematopoietic necrosis virus, chinook salmon embryo cells, fathead minnow cells, rainbow trout cells, salmonid viruses
Management Alternatives and Strategic Planning for Canada's Fisheries
Authors: Sinclair William F.
Published: April 2011

The evils of operating Canada's commercial and recreational fisheries under open-access conditions were known before Confederation. Early recognition of these ills did not lead to an understanding of the basic problems nor to long-term solutions. In the early 1950s the first economic model was developed that articulated the underlying causes of excess capacity and the tendency of overexploitation in open-access fisheries. This was followed by a number of studies that explored the relationship between the biological reproductive capacity of a fishery and the economic consequences of managing publicly owned resources under open-access conditions. This early work provides a general framework from which a number of fisheries management alternatives emerge. Each of six management alternatives, which are implicit in policy for Canada's commercial fisheries, are assessed in terms of political acceptability, administrative feasibility, and effectiveness. It is emphasized that the responsibility of a government fisheries agency is to manage fisheries resources in the best interest of the owners of the resource – the nation's taxpayers. A properly implemented license control system would dissipate, rather than perpetuate, social and economic hardship among fishermen. This misplaced concern for unproven social problems often leads fisheries managers to support programs that sacrifice all the benefits that could be generated from the resource and the resource itself. A management scheme is recommended that encompasses a simple licensing system, a tax or a royalty on catch, and a limited variation of the "Grandfather System." The combination of these three incorporates the main advantages of most management alternatives while avoiding most of their main shortcomings. A carefully implemented program that accounts for economic and biological considerations would improve the efficiency of the industry, improve fishermen's incomes, minimize social disruptions, help to instill an environmental conscience, protect the resource, and induce less, rather than more, government intervention into the free operation of the fishing industry. Probably more important, the program would generate an economic return for the people of Canada. Key words: overcapitalization, open-access fisheries, fisheries economics, fisheries management, fisheries policy, fish licensing, license limitation, fish royalties, tax on fish landings
Thermal Ecology II.
Authors: McMahon J. W.
Published: April 2011

not available
Circulation, Variability, and Dynamics of the Scotian Shelf and Slope
Authors: Smith Peter C. , Petrie Brian , Mann C. R.
Published: April 2011

A brief summary of historical data relating to the mean circulation on the Scotian Shelf and Slope reveals the distribution of various water masses and certain general characteristics of the current field, supported by geostrophic calculations and observations of surface drift. However, extreme variability resulting from wind and tidal forces is evident in all measurements made on the shelf and slope. Various measurements and models of the first-order variable flows, including wind-driven circulation, diurnal and semidiurnal tides, and inertial waves, are also reviewed. Results from a new model for inertial motions in a variable-depth mixed layer are found to closely reproduce the transient behavior of inertial energy at the 50-m depth on the shelf, but certain aspects of the model are inconsistent with the observations. With results from a mooring program on the shelf in September–December 1968, the dynamics of the mean circulation are examined in the context of a vertically integrated, two-dimensional model. Reynolds stresses associated with the first-order flows are found to be insignificant in the inshore zone (within 90 km of the coast) where the balances are between mean wind and bottom stresses, surface pressure gradients, and Coriolis forces. Over the outer shelf, however, the geostrophic onshore balance breaks down and Reynolds stress divergences in the inertial and tidal bands become important. At the shelf break, generation of the baroclinic semidiurnal tide produces internal Reynolds stress forces comparable to the barotropic terms on the shelf. Key words: mean circulation, semidiurnal barotropic and internal tides, inertial waves, mixed layer, wind-driven circulation, Reynolds stress, geostrophic, Scotian Shelf
Permanent Sedimentation of Nitrogen, Phosphorus, and Organic Carbon in a High Arctic Lake
Authors: March L. de
Published: April 2011

The sediments of Char Lake, Resolute, Northwest Territories, were studied to determine storage rates of nitrogen, phosphorus, and organic carbon which could be compared with retention estimates of N and P and primary production and respiration estimates for organic C. The storage rate for P (0.018 g∙m−2∙yr−1) was 129% of measured retention, storage of N (0.087 g∙m−2∙yr−1) was 43% of measured retention, and the 1 g∙m−2∙yr−1 storage estimate for organic C was 18% of the difference between primary production and respiration. Lacustrine sediments were found to be very unevenly distributed with accumulations from 7 cm to an estimated 3 m in the last 6200 yr and to vary in N, P, and organic C concentrations from place to place. Key words: sedimentation, nutrient budgets, arctic, lake, carbon, nitrogen, phosphorus
Seasonal Changes in Nitrogen Compartments of Lakes Under Different Loading Conditions
Authors: Liao C. F.-H. , Lean D. R. S.
Published: April 2011

To develop a better conceptual picture for nitrogen dynamics in lake ecosystems, the seasonal changes in the concentrations of nitrate, ammonia, dissolved organic and particulate nitrogen were monitored in the water contained in three limnocorrals located in the Bay of Quinte, Ontario. Following the decline in summer particulate N, there was an increase in ammonia. This was followed by an increase in nitrate throughout the winter suggesting that nitrification was a significant process. To assess the potential contribution of the sediments, ammonia, nitrate, and dissolved organic N were measured for pore waters and total N, exchangeable ammonia, and nitrate in the solid fraction. The influence of nutrient addition was evaluated by comparing corral I, receiving no nutrient additions, with corral II to which phosphate was added (0.92 g P/m2 per yr) and corral III which received the same amount of phosphate plus nitrate at an N:P weight ratio of 13. Increases and decreases in phosphorus, nitrogen, and chlorophyll a seemed to take place in all three corrals at the same time. There was a considerable delay in the response to nutrient enrichment, but the addition of nitrate and phosphate eventually resulted in a chlorophyll a level greater than that for phosphate enrichment alone. The importance of sediments as a net source of N for the planktonic community was insignificant, but the flux rate for nitrogen to and from the sediment was important. During the summer an input–output budget showed that nitrate loading plus N2 fixation was approximately equal to the net change in the total combined N in the water. This implied that denitrification was not important, but over 12 mo most of the nitrogen that entered the system was lost; hence denitrification must be important at certain times. A lake ecosystem tends to compensate for low or high levels of NO3 loading. Without the addition of nitrogen the requirement was partly met through nitrogen fixation and this can be enhanced by P enrichment. Key words: ammonia, nitrate, nutrient kinetics, nitrogen fixation, denitrification, sediments
Nitrogen Transformations Within the Trophogenic Zone of Lakes
Authors: Liao C. F.-H. , Lean D. R. S.
Published: April 2011

The uptake rates for ammonia and nitrate were measured in limnocorrals and in the adjacent water in the Bay of Quinte, Ontario. Even though the net change of nitrate exceeds that for ammonia over the summer, it is ammonia that is the most significant source of N for the plankton. The uptake rates were light dependent; in the dark uptake of nitrate was reduced 60–95% and ammonia by 40–70%. The uptake of N is not correlated to net production but to gross production. These rates were integrated with sedimentation, N release by zooplankton excretion, and N2-fixation. Although N2-fixation provides only a small amount of the daily N requirement compared with ammonia uptake, ammonia is rapidly recycled and the N2-fixation is the vital process controlling the amount of this essential nutrient in systems where it is in short supply (corral II). Zooplankton grazing and sedimentation (decomposition) can account for much of the ammonia regeneration, but direct release of ammonia from the plankton appeared to be important. Key words: ammonia, nitrate, 15N kinetics, zooplankton grazing, nitrogen fixation
Circulation in an Open Bay
Authors: Petrie Brian , Drinkwater Ken
Published: April 2011

The circulation of St. Georges Bay, Nova Scotia, under stratified conditions is presented. The mean surface circulation is characterized by a clockwise eddy with velocities of about 10 cm∙s−1. Bottom (30 m) flow at the mouth is found to be < 2 cm∙s−1 out of the bay. Depth-averaged currents still exhibit the clockwise eddy. Although energy is found to be equally partitioned among the mean circulation, the tides, and low-frequency events, the latter determines the rate of exchange between the bay and the Gulf of St. Lawrence. Estimates of flushing time for tides and the mean circulation is of the order of a month, while low-frequency events could flush the bay on a time scale of days. Low correlation between current meters reveals the vertical and horizontal length scales of the bay are < 10 m and 5 km, respectively. The circulation and exchange rates can significantly affect the dispersal (or exchanges with populations existing outside the bay) for passive particles such as fish eggs or larvae. Key words: coastal, bay, circulation, gyre, tides, low-frequency stratified, exchange, fish larvae
A Device to Simulate the Variability in Sunlight Intensity for Laboratory Cultures of Algae
Authors: Boyd Carl M. , Marra John
Published: April 2011

Simulation in the laboratory of the variability of environmental light intensity is achieved by automatic continuous control of voltage applied to a tungsten light source. Key words: light intensity, variable light, photosynthesis, diurnal rhythms
Production, Mortality, And Sustainable Yield Of Northwest Atlantic Harp Seals (Pagophilus groenlandicus)
Authors: Winters G. H.
Published: April 2011

From recent and historical data the natural mortality rate of adult harp seals (Pagophilus groenlandicus) is estimated to be 0.10 which is within the range of previous estimates (0.08–0.11). New estimates of bedlamer and 0-group natural mortality rates were not significantly different from those of adult seals. Pup production estimates from survival indices agreed well with those from sequential population analyses and indicated a decline from about 350 000 animals in the early 1950s to about 310 000 animals in the early 1970s. Over the same period the 1+ population size declined from 2.5 to 1.1 million animals but has been increasing at the rate of 3%/yr since the introduction of quotas in 1972. The relative contribution of the "Front" production to total ("Front" plus Gulf) production during the past decade has fluctuated from 49 to 87%, the average of 64% being very similar to the 61% obtained previously. These fluctuations suggest some interchange between "Front" and Gulf adults and it is concluded that homing in the breeding areas is a facultative rather than obligatory aspect of seal behavior. Thus the heavier exploitation of the "Front" production is probably sufficiently diffused into the total population to avoid serious effects on "Front" production. The maximum sustainable yield of Northwest Atlantic seals harvested according to recent patterns is estimated to be 290 000 animals (80% pups) from a 1+ population size of 1.8 million animals producing 460 000 pups annually. The sustainable yield at present levels of pup production (335 000 animals) is calculated to be 220 000 animals which is substantially above the present TAC of 180 000 animals and coincides with present harvesting strategies designed to enable the seal hunt to increase slowly towards the MSY level. Key words: mortality, production, sustainable yield, population dynamics, marine mammal
Rapid Method for Determining Concentrations of Bayer 73 in Water During Lampricide Treatments
Authors: Dawson V. K. , Harman P. D. , Schultz D. P. , Allen J. L.
Published: April 2011

Two simple, rapid, sensitive methods were developed for determining the concentration of the lampricide 2′,5-dichloro-4′-nitrosalicylanilide (Bayer 73) in stream water. Bayer 73 was extracted from acidified water samples with chloroform and then hydrolyzed to 2-chloro-4-nitroaniline (CNA) with either acid or base. The CNA was diazotized with sodium nitrite, and an azo dye was formed with either N-(1-naphthyl) ethylenediamine dihydrochloride (after acid hydrolysis) or 1-naphthol (after base hydrolysis). There was no interference from the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) in either method. Standard curves were prepared with untreated water to compensate for interfering substances that occurred naturally in some streams. The methods were sensitive to about 0.005 mg/L (ppm). Time required for analysis of a sample ranged from 25 min to 1 h. Key words: Bayer 73, Bayluscide®, 2′,5-dichloro-4′-nitrosalicylanilide, lampricide, phenylamide, analysis, water, colorimetric, sea lamprey, Great Lakes
Index to Scientific and Technical Proceedings.
Authors: Marshall K. E.
Published: April 2011

not available
Effect of Ozonation on Microbial Fish Pathogens, Ammonia, Nitrate, Nitrite, and BOD in Simulated Reuse Hatchery Water
Authors: Colberg P. J. , Lingg A. J.
Published: April 2011

The effectiveness of ozone as a disinfectant of makeup water and its potential for treatment of recycled water in commercial reuse hatcheries was considered in this study. Comparative survival rates in water were established for four bacterial fish pathogens (Aeromonas salmonicida, A. liquefaciens, Pseudomonas fluorescens, Yersinia ruckeri [the causative agent of enteric redmouth disease]), Bacillus polymyxa, and a bacterium–protozoan population during batch and continuous flow ozonation. A specific microbial ozone demand was exerted during batch ozonation, and > 99% mortality of the fish pathogens was observed within 60-s contact during continuous flow exposure at 1.0 and 0.1 mg O3/L. Spores of B. polymyxa were resistant to a concentration of 1.0 mg O3/L for at least 10 min. The oxidation rate for the combined bacterial–protozoan biomass closely approximated rates established in pure culture studies, with no significant difference in relative survival rates between bacteria and protozoa. Elevated carbon levels did not appear to exert a preferential ozone demand when added to suspensions of test organisms. Oxidation of carbon and nitrite by ozone was rapid at low ozone concentrations, with carbon and ammonia oxidation rates exhibiting pH-dependence. The oxidation capacity of ozone in water was greatest at elevated pH even though the measurable ozone concentration was lower. Key words: ozone, fish pathogens, BOD, nitrite, ammonia, protozoans
Model for Examining Early Ocean Limitation of Pacific Salmon Production
Authors: Walters Carl J. , Hilborn Ray , Peterman Randall M. , Staley Michael J.
Published: April 2011

A computer simulation model was used to examine growth and survival of all major British Columbia salmon stocks during their first 6 mo of ocean life. Factors included in the calculations were the space–time distribution of zooplankton production, timing of salmon ocean arrival and migration especially as regards overlaps between stocks, feeding and growth in relation to food availability, and mortality rates in relation to body size. It is concluded that ocean limitation of production is unlikely unless only a small fraction of total zooplankton production is available to the salmon. The model emphasizes several critical uncertainties about the marine biology of salmon: rates of replenishment of near surface zooplankton stocks (where most salmon feeding occurs) from deeper water have not been adequately measured, and the functional response of salmon to prey density is not understood. There is inadequate data on the relationship between body size and mortality rate, and migration patterns of juvenile fish have not been documented precisely enough. Hopefully some of these uncertainties will be resolved through the salmon enhancement programs. Key words: salmon, population limitation, juvenile marine production, simulation model
Prediction of Egg Development Times of Freshwater Copepods
Authors: Cooley John M. , Minns Charles K.
Published: April 2011

Available literature data on the relationship between freshwater copepod egg development time and temperature were summarized and fitted where possible to Bělehrádek's temperature function[Formula: see text]where D is development time, T is temperature, a, b, and α are fitted constants. In the calanoids, and to a lesser extent cyclopoids, a and α were predictably related as were α and in situ egg hatching temperature (TH) when b was assumed to be constant for all copepods. This information was used to describe a simple procedure whereby a curve relating egg development and temperature could be constructed by only knowing TH and applying it to Bělehrádek's temperature function. Key words: Calanoidea, Cyclopoidea, zooplankton, temperature, production assessment
Helminths of the Alimentary Tract from a Stranded Herd of the Atlantic White-Sided Dolphin, Lagenorhynchus acutus
Authors: Beverley-Burton M.
Published: April 2011

Six species of helminths were collected from the gut of 37 Lagenorhynchus acutus. The following are new host–parasite records: Pholeter gastrophilus, Oschmarinella laevicaecum, Tetrabothrius forsteri, Anisakis sp., and Bolbosoma sp. Stenurus globicephalae was also found. Prevalence for O. laevicaecum was 49% and for T. forsteri 78%. Key words: Atlantic dolphins, digenea trematodes, cestodes, nematodes, acanthocephala, biological tags
Use of Aniline Blue for Distinguishing Between Live and Dead Freshwater Zooplankton
Authors: Seepersad B. , Crippen R. W.
Published: April 2011

It is possible to distinguish between live and dead freshwater zooplankton after 15-min immersion in an aqueous solution of aniline blue. Organisms physiologically dead at the time of staining are dyed blue, whereas living organisms remain unstained. This mortal staining technique has been repeatedly used in evaluating the survival of individuals belonging to all major groups of freshwater zooplankton. It has special application where the survival of large numbers of plankters must be determined either within a short interval, for successive intervals, or where conditions do not permit such evaluations immediately following collection or treatment. Stained samples preserved in formalin showed no evidence of leaching when stored at 4–15 °C for several months. This technique has been used successfully for entrainment studies for power plants with once-through cooling systems. Key words: freshwater plankton, zooplankton, phytoplankton, ichthyoplankton, dead–live determinations, mortal staining, power plant(s) entrainment, industrial monitoring
Capture Probability: The Role of Zooplankter Escape in the Selective Feeding of Planktivorous Fish
Authors: Drenner Ray W. , Strickler J. Rudi , O'Brien W. John
Published: April 2011

The conditional probabilities (P3) of being captured by a simulated fish-suction intake ranged from P = 0.76 to P = 0.96 for cladocerans and from P = 0.07 to P = 0.28 for copepods. Gizzard shad (Dorosoma cepedianum) feeding experiments confirmed that these differential capture probabilities can result in an apparent planktivore feeding selectivity for cladoceran zooplankters. Key words: capture probability, zooplankter escape, planktivore feeding selectivity, gizzard shad
Effect of Organic Color and Turbidity of Secchi Disk Transparency
Authors: Brezonik Patrick L.
Published: April 2011

Secchi disk transparency in lakes is a function not only of the turbidity caused primarily by plankton, but also of the organic color level in the water. Multiple regression analysis of data from 55 Florida lakes yielded a close-fitting equation of the type (SD)−1 = a(Color) + b(Turbidity) + c. The statistical relationships between inverse transparency and chlorophyll a and between log transparency and log chlorophyll a exhibited greater scatter. Experiments in which concentrated solutions of humic substances were added to a large plastic "limno-bag" verified the linear relationship between (SD)−1 and color content but yielded a different slope than that obtained by regression analysis. The maximum possible transparency (assuming zero turbidity) was similar for both the experimental and regression relationships at color levels above 50 platinum (Pt) units, but increasingly divergent results were predicted by the two approaches at lower color levels. At a color of 100 Pt units, the maximum Secchi disk transparency is about 2.4–2.8 m. Because of the crudeness of transparency measurements, use of the above regression equation to compute transparencies from measured turbidities appears to be more reliable than use of the experimentally derived equation. Key words: Secchi disk, transparency, color, turbidity, trophic indicator, chlorophyll a, light attenuation
Effects of Age and Overhead Illumination on Temperatures Preferred by Underyearling Rainbow Trout, Salmo gairdneri, in a Vertical Temperature Gradient
Authors: Kwain Wen-Hwa , McCauley Robert W.
Published: April 2011

During their first 12 mo of life rainbow trout, Salmo gairdneri, preferred progressively cooler temperatures as they grew older; 19 °C was selected during the 1st mo and the selected temperature declined by intervals of 0.5 °C for each of the following months up to the 3rd mo. Fish swam higher in temperature gradients exposed to overhead illumination than in those in total darkness. This trend was reversed during the following 9 mo. These findings demonstrate the important role that age plays in the temperature preference of this species and the influence that overhead light may have on the distribution of fish in vertical gradients. Key words: preferred temperature, age, Salmo gairdneri, light gradients
Testing for Density-Dependent Marine Survival in Pacific Salmonids
Authors: Peterman Randall M.
Published: April 2011

Marine survival data for several different salmonid stocks were reviewed to determine whether there was significant density-dependent survival occurring in the ocean. Four classes of interaction were examined: (1) within-cohorts, (2) between-cohorts, (3) between stocks on the same or nearby rivers, and (4) between stocks of distant rivers. Results of statistical tests indicate that some stocks do not produce an increase in adult returns with increased smolt abundance, and that marine survival rate of other stocks is affected by abundance of other cohorts or stocks. Only a few stocks exhibit these density-dependent relations, but given present data, it is impossible to predict the frequency of occurrence of such limiting processes in future enhanced stocks. Salmonid enhancement planning is discussed in the context of this uncertainty and experimental enhancement projects are suggested that aim to obtain information about marine survival processes as well as additional catches. Key words: density dependent, marine survival, salmonids, experimental enhancement, stock interaction, adaptive
Correlations Between Specific Algae and Heavy Metal Binding in Lakes
Authors: Briand Frédéric , Trucco Ramiro , Ramamoorthy S.
Published: April 2011

Long-term experiments conducted at Heney Lake, Quebec, show the binding capacity for the metal ions Cu2+, Hg2+, Pb2+, and Cd2+ to be related to algal species composition rather than to total algal biomass or physicochemical parameters. Most of the binding could be accounted for by certain species of green algae, diatoms, and chrysomonads that usually constituted only a minor fraction of the total algal volume. Key words: freshwater phytoplankton, heavy metal binding, field study, diatoms, chrysomonads, green algae
Ichthyoplankton of the St. Lawrence Estuary: Composition, Distribution, and Abundance
Authors: Able Kenneth W.
Published: April 2011

The composition, distribution, and abundance of ichthyoplankton in the St. Lawrence estuary, including adjacent portions of the Saguenay River and the northwestern Gulf of St. Lawrence, were investigated during June–July 1973, June–October 1974, and May–September 1975. The eggs and larvae of 25 species from 14 families (principally osmerids, gadids, cottids, cyclopterids, and pleuronectids) were represented. The larvae, in every year, were almost exclusively forms with demersal eggs. Larvae were consistently more abundant in the upper estuary during every sampling period due to its use as a major spawning and nursery area for several species. Both eggs and larvae were most abundant in June and July. Probable spawning times, areas, and growth of larvae are discussed for selected species. Key words: ichthyoplankton, St. Lawrence estuary, distribution, larvae, osmerids, gadids, cottids, cyclopterids, pleuronectids
Life History and Taxonomic Status of an Isolated Population of Arctic Char, Salvelinus alpinus, from Gros Morne National Park, Newfoundland
Authors: Rombough P. J. , Barbour S. E. , Kerekes J. J.
Published: April 2011

Landlocked Arctic char, Salvelinus alpinus, from Candlestick Pond, Gros Morne National Park, Newfoundland, were characterized by slow growth, short life span (max 7 yr), and small size (max fork length = 164 mm). Sexual maturity was obtained at age 3, fecundity was low (max 104 ova per fish), and spawning annual. Major food items were zooplankton and aquatic insect larvae. Eight morphometric and eight meristic characters were examined and compared with available literature data for nonanadromous S. alpinus in eastern North America. Arctic char from Candlestick Pond were not significantly different from S. alpinus oquassa from Quebec and Maine but were significantly different from char from Labrador and other locations in insular Newfoundland. It is proposed that Arctic char from Candlestick Pond are descendents of an aboriginal form of S. alpinus that has been largely displaced along the Atlantic coast of North America. Key words: Salvelinus alpinus, Newfoundland, life history, taxonomic status
Changes in Gill ATPase Activity and Smolt Status of Atlantic Salmon (Salmo salar)
Authors: Saunders Richard L. , Henderson Eugene B.
Published: April 2011

Gill Na+K+-activated ATPase activity increased during winter–spring in Atlantic salmon (Salmo salar) held at 10 °C and subjected to simulated natural or reciprocal (light/dark ratio opposite that of natural) photoperiods. ATPase activity increased earlier and was greater under the reciprocal than under the natural photoperiod regime. Body lipid decreased and moisture content increased sooner and more sharply in reciprocal than in natural photoperiod fish. Salinity tolerance (to 40‰) increased between March and April. Exposure to 40‰ salinity for periods up to 14 d gave marked increases in ATPase activity over levels measured in freshwater. Gill ATPase activity is a sensitive indicator of the ability of Atlantic salmon to osmoregulate in seawater. Together with lipid-moisture content, tolerance to high salinity, and migratory behavior, gill ATPase activity provides a valid indication of smolt readiness to migrate to sea. Key words: smolt criteria, photoperiod manipulation, Atlantic salmon, smolt physiology, salinity tolerance, osmoregulation