bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin, Distribution, and Postglacial Dispersal of a Swimbladder Nematode, Cystidicola stigmatura
Authors: Black Geoff A.
Published: April 2011

New distributional records indicate that Cystidicola stigmatura occurs in lake trout (Salvelinus namaycush) and Arctic char (S. alpinus) in the Great Lakes and St. Lawrence River drainage basins, in lakes along an arc extending from northwestern Ontario to Great Bear Lake and into the Canadian Arctic Archipelago but not elsewhere. This distribution can be explained by the parasite's probable postglacial history. I hypothesize that the nematode survived in only one glacial refugium. During deglaciation the parasite probably dispersed with lake trout from its refugium in the upper Mississippi River region into the Lake Michigan basin. Confluence of glacial waters would have given the nematode access to the drainage basins of Lakes Huron, Erie, and Ontario. Invasion of the St. Lawrence River basin occurred during a postglacial connection with the Lake Ontario basin. Dispersal from the Lake Huron basin was via glacial Lake Algonquin and later via glacial Lake Barlow–Ojibway and gave rise to present populations in eastern Ontario and western Quebec. Northward dispersal was probably via the glacial waters of the Lake Michigan–Lake Superior basin through glacial Lakes Agassiz, McConnell, and Coppermine to the Arctic Ocean. Arctic char would have first acquired the parasite at this time. Extant parasite populations along this dispersal route occur in Minnesota, northwestern Ontario, Manitoba, Saskatchewan, and the Northwest Territories. Invasion of the Arctic Archipelago has been with anadromous fishes. The apparently restricted preglacial distribution of the nematode and recent history of its intermediate host (Mysis relicta) in freshwater suggests that C. stigmatura may have arisen as a species during the last glaciation.
Characterization of Organic Copper-Complexing Agents Released by Daphnia magna
Authors: Fish William , Morel François M. M.
Published: April 2011

Zooplankton release a variety of organic and inorganic compounds into their aqueous surroundings. To test the effects of this on trace metal speciation, we raised Daphnia magna in a defined, synthetic medium at various population densities. A series of Cu(II) and pH titrations using an ion-selective electrode apparatus confirmed the excretion of moderately strong metal-binding organic compounds. Control experiments established that bacteria do not produce the complexing agents. The mean hourly excretion rate in the cultures was 40 ± 8 pmol/organism. The complexing material is characterized by two model ligands with conditional stability constants (at pH 6.30) log K1 = 8.6 and log K2 = 6.4. These stability constants are similar to those obtained for humic and fulvic acids and suggest a role for this material in the trace metal speciation of natural waters. The release of complexing agents may also affect the results of Daphnia toxicity tests by reducing metal activities during incubation.
Deformation of the Active Space in the Low Reynolds Number Feeding Current of Calanoid Copepods
Authors: Andrews John C.
Published: April 2011

The active space is the zone around an alga where chemical exudates are sufficiently concentrated to promote a behavioral response in a grazing copepod. Chemosensory perception of algae by copepods is investigated with a numerical model of the effects of advection in copepod feeding currents on the chemical diffusing from algae. Recent observations of encounters between algae and calanoid copepods define length and speed scales for a doubly sheared, low Reynolds number flow. These scales and shears are incorporated in an analytical description of the feeding current. Advection of the chemical in the laterally sheared flow changes the distribution of the exudates to create a deformed active space. An initially spherical active space is elongated and the edge of the active space is projected an order of magnitude further in the direction of the flow than the undisturbed radius. The advance warning received by a copepod of an approaching alga is a function of the radius of the active space, the detection threshold, the position of the alga in the stream field, and the molecular diffusivity of the exudate. An example of the relation between radius, detection threshold, and diffusivity for a detection distance of 1000 μm demonstrates that the model is well behaved for widely varying parameter values and loosely defines some bounds for the controlling parameters.
Turbidity Maximum Migration and Harbor Siltation in the Tay Estuary
Authors: Dobereiner C. , McManus J.
Published: April 2011

Multiboat simultaneous survey along the 50 km macrotidal Tay Estuary suggested that the turbidity maximum was related to resuspension from tidal flats. New monthly analyses revealed that the turbidity maximum varies in position not only with neap/spring tidal cycles but also in response to river runoff. No relationship was found between elemental particle size and aggregate diameter. Both organic and inorganic particles were found to contribute to aggregate growth, the former exhibiting a slightly greater range of particle diameters than the latter. Aggregate diameters increased with suspension concentration and it is suggested that pH as well as salinity also contribute to aggregate formation.Continuous siltmeter recordings at Dundee show maximum suspension concentrations on the ebb phase of neap tides and on spring flood tides. In the lower estuary suspension concentrations and salinities vary from shore to shore. The lateral differences are substantial so that a purely one-dimensional variation pattern does not provide sufficient data for thorough analysis of the processes active in this estuary. The observed behavior of the turbidity maximum and related siltation patterns suggest that concentrating maintenance dredging in late spring and early summer would be cost-effective for Dundee Harbour and similar estuarial situations.Key words: turbidity maximum, suspended sediment, aggregation, estuary, fluvial discharge, harbor siltation
Optical Properties, Suspended Sediments, and Chemistry Associated with the Turbidity Maxima of the Delaware Estuary
Authors: Biggs Robert B. , Sharp Jonathan H. , Church Thomas M. , Tramontano John M.
Published: April 2011

Two turbidity maxima were found in the Delaware Estuary and were distinct both in terms of optical properties of the water and in quantity of suspended material. The upstream maximum occurred at about 1‰ salinity. Both the diffuse attenuation coefficient (KD) and the beam attenuation coefficient (α) responded to the double turbidity maxima. The upstream maximum contains a larger number of individual mineral grains with a mean diameter of about 3 μm; the downstream maximum, which occurred at salinities of 7.5–10‰, was dominated by composite particles with a mean size of 12 μm; at salinities > 10‰, the suspended sediment population was dominated by large (10–20 μm) individual particles with few composite particles.Nutrients, productivity, particulate organic matter, and dissolved and particulate metals all showed relationships to the turbidity maxima when viewed on salinity and on geographic axes. An excess of dissolved inorganic nitrogen in relation to dissolved inorganic phosphorus was mirrored by exceptionally low particulate C/P ratios in the region of the turbidity maxima. Primary productivity appeared to be greatly reduced in the region of the downstream turbidity maximum.The trace metals Fe, Mn, Cd, Cu, Co, and Ni showed a general association with particulate phases at lowest salinities, at the upstream turbidity maximum. The more particle reactive metals (Fe, Mn, and Co) reflected this as enrichment relative to particulate aluminum. At the downstream turbidity maximum, in the mid-salinity range, the trace metals showed a minimum relative to Al, probably due to dilution by resuspended bottom sediments. In the lower estuary, the trace metals exhibited the highest enrichment (relative to aluminum) and an association with high concentrations of particulate carbon.Key words: Delaware Estuary, turbidity maxima, optical properties, suspended sediments, chemistry
Heterotrophic Bacterial Biomasses, Activities, and Productivities Within The Fraser River Plume
Authors: Albright L. J.
Published: April 2011

Most of the microorganisms within the silt-laden Fraser River water are bacteria, the majority of which are attached to detritus and suspended silt. However, within surface water of the Strait of Georgia bacteria constitute only about 4% of the microbial biomass; most are free-living. Within the plume, which results when the freshwater of the Fraser River mixes with the seawater of the Strait of Georgia (salinity of about 27‰ and containing mainly phytoplankton) stimulations of bacterial glucose heterotrophic activity and productivity occur throughout the year. Bacterial production is a relatively greater proportion of the total microbial, i.e. both algal and bacterial production, in the winter than in the spring or fall. Preliminary evidence indicates that the stimulation of bacterial activity and productivity may be, at least partially, due to entrainment of nitrate and phosphate-rich deep water of the Strait of Georgia into the Fraser plume.Key words: Fraser plume, bacteria, production, heterotrophic activity, Strait of Georgia
Particle Resuspension in the Benthic Boundary Layer Induced by Flow around Polychaete Tubes
Authors: Carey Drew A.
Published: April 2011

The effect of the projecting tubes of Lanice conchilega (Terebellidae) on particle flux in the benthic boundary layer was studied in laboratory flume experiments. Intact tubes, worms, and flume sediment were collected from an ebb channel of the Tay Estuary. Experiments were performed with dye and high contrast, near-neutral density particles to determine flow patterns and net particle movement in individual tube wakes. Projecting tubes produced characteristic vortex patterns which may increase resuspension of sediment particles. These vortex patterns were not strongly dependent on obstacle shape or flow regime and resulted in pronounced upward motion of fluid from the bed. Particle velocities within the wake were lower than ambient free stream velocity. Results of flume observations reported are consistent with detailed visualization studies of small-scale disturbances within a laminar boundary layer.Key words: resuspension, boundary layer, benthos, tubes, polychaete, Lanice conchilega, flow visualization
Microbial and Photochemical Degradation of Polycyclic Aromatic Hydrocarbons in Estuarine Waters and Sediments
Authors: Lee Richard F. , Ryan Charlotte
Published: April 2011

Radiolabeled polycyclic aromatic hydrocarbons (PAH) containing up to three rings, including naphthalene, methylnaphthalenes, and phenanthrene, were degraded (measured by 14CO2 production) in water samples from both Narragansett Bay and southeastern United States. Higher weight PAH, including benz[a]anthracene, chrysene, fluorene, and anthracene, showed little, if any, degradation in water but were readily degraded when added to sediment–water slurries. In areas with low levels of petroleum in the water or sediment there was a lag before appreciable degradation began, and the rate of degradation fitted a first-order equation. Half-lives, calculated for the various PAH added to water or sediment–water slurries, were very low during winter months; [14C]methylnaphthalene added to water from Skidaway River, Georgia, in January (8 °C) was 57 d, while in September (28 °C) it was 3 d. PAH added to sediments or water from oil-treated areas or mesocosms were rapidly degraded with no lag phase and the degradation rate was linear. [14C]Methylnaphthalene added to water from control and oiled mesocosms in May (10 °C) had half-lives of 300 and 5 d, respectively. We plotted the changes in turnover times with changes in the concentration of PAH and calculated the natural turnover times and Vmax for PAH added to water or sediment from the oiled mesocosms. When [14C]dimethylbenz[a]anthracene was incubated in water in the dark no degradation occurred, but when exposed to sunlight, 0.3% was mineralized in 18 h. In addition, a variety of photooxidation products were produced. The production of 14CO2 in the light was due to microbial degradation of photooxidation products of [14C]dimethylbenz[a]anthracene.
The Distribution of Dissolved and Organically Complexed Copper and Nickel in the Middle Atlantic Bight
Authors: Hanson Jr. Alfred K. , Quinn James G.
Published: April 2011

An analytical procedure involving C18 reverse-phase liquid chromatography and heated graphite atomizer–atomic absorption spectroscopy was used to isolate and measure dissolved organically complexed copper and nickel along a section from the shelf–slope boundary into the New York Bight apex. The dissolved organic matter isolated by C18 reverse-phase liquid chromatography was further separated and partially characterized by high-performance liquid chromatography. The distributions of dissolved copper and nickel were similar, with higher concentrations in the low-salinity surface waters and lower concentrations beneath the pycnocline and in slope waters. The concentration of total dissolved copper and nickel ranged from 0.77 to 8.67 nmol/kg and 2.3 to 14.7 nmol/kg, respectively. The concentrations of organically complexed copper (0.24–1.67 nmol/kg) increased uniformly across the shelf, with the highest concentrations at the New York Bight apex. A small percentage of the dissolved nickel (0–8%) was isolated as organically complexed nickel. The variation in the percentage of dissolved copper isolated as organically complexed copper (10–60%) was systematically related to other chemical properties and hydrographic features of the region. The organic components responsible for the copper complexation in these coastal waters are chromatographically similar to terrigenous fulvic acid and may originate in riverine waters.
Role of Marine Phytoplankton in Determining the Chemical Speciation and Biogeochemical Cycling of Arsenic
Authors: Sanders James G.
Published: April 2011

Biological mediation of arsenic speciation in marine systems is substantial and significant. Phytoplankton reduce and methylate arsenic, thus altering its geochemical cycle. Rates of arsenic reduction and methylation are proportional to the primary productivity of the ecosystem. In highly productive ecosystems, up to 80% of the total arsenic pool may undergo reduction and methylation. Experiments detailing rates of reduction have been performed in controlled marine ecosystems. Predictions of arsenic speciation based on these results agree well with actual samples taken from coastal areas. The form of reduced arsenic present varies between regions and temporally within regions, probably because of differences in phytoplankton community structure.
The Role of Zooplankton in the Accumulation and Deposition of DuPont Edgemoor Waste (an Acid-Iron Waste) at a Deepwater Dumpsite in the Northwest Atlantic
Authors: Capuzzo Judith M.
Published: April 2011

DuPont Edgemoor waste derived from titanium dioxide production is a highly acidic solution of ferric chloride containing relatively high levels of several trace metals including Cr, V, Pb, Ni, Cu, and Cd. Approximately 3 × 105 t∙yr−1 are dumped at Deepwater Dumpsite 106, ~160 km southeast of Ambrose Light, New York. Chemical dispersion studies at the dumpsite indicate that ferric oxide precipitates in the waste plume and that other trace metals may become associated with this particulate phase. Ingestion of this particulate phase by copepods is a significant route of uptake for the waste-derived metals in the laboratory. Accumulation of the various metals by exposed copepods ranged from 10.8% above control values for Fe to 54.7% for Cu. The ratios of the various trace metals relative to Fe were only slightly enhanced in exposed copepods in comparison with control copepods but 1 to 2 orders of magnitude higher than the metal ratios of a 105 waste dilution. Enhancement of metal concentrations in fecal pellets produced by exposed copepods ranged from 25.0% above control values for Fe to 60.3% for Cu. Metal deposition through fecal pellet production appears to be an effective means of depurating Fe, Pb, Ni, and Cu by copepods exposed to Edgemoor waste but not for Cd, which could not be detected in fecal pellets. The greater density of fecal pellets compared with the ferric oxide particles could result in a more rapid sinking rate of waste-derived metals to the deep ocean. The flux of waste-derived metals through Zooplankton biomass and the contribution of Zooplankton in the biogeochemical cycling of metals at Deepwater Dumpsite 106 suggests that biological processes may be as important as advective processes in determining the fate of waste-derived metals.
Utilization of Phytoplankton by Zooplankton during the Spring Bloom in a Nova Scotia Inlet
Authors: Conover R. J. , Mayzaud P.
Published: April 2011

Coulter counter and microscope counts were used to estimate filtration and ingestion rates experimentally for total zooplankton caught by a 233-μm mesh net from two depths during the spring bloom in Bedford Basin. Initially, most phytoplankton were <20 μm with larger, chain-forming diatoms becoming more important as the bloom developed. Peak concentrations were >14 μg chlorophyll∙L−1and >1 mg C∙L−1and particle volume was >10 mm3∙L−1. Maximum primary production was >30 mg C∙m−3∙h−1. Dominant phytoplankton included Chaetoceros septentrionale early in the bloom, followed by Skeletonema costatum and Thalassiosira, Rhizosolenia, and Chaetoceros spp. Barnacle nauplii and Acartia hudsonica were the most common zooplankton near surface and Pseudocalanus sp. in deeper water. Ingestion was usually greatest at or near peaks in the Coulter counter particle spectrum. Filtration rate was proportional to grazer size and amount ingested and also to ambient particle concentration for near-surface but not deeper zooplankton. Higher ingestion was measured with the Coulter counter but microscopic counts gave higher filtration rates. Smaller surface-layer zooplankton apparently destroyed cells or chains that were not completely ingested. Microscopic estimates of particle volume ingested were 9–60% of that measured with the Coulter counter, suggesting utilization of detritus. Despite discrepancies in what the methods apparently measured, neither suggested a saturating functional response at ambient concentration, but with further concentration, both methods showed reduced filtration activity. Neither method revealed evidence for size-selective feeding, even when particles were compared on the basis of their maximum dimensions, but optical counts showed that single cells or chains of cylindrical shape were preferred to needle-like or spiney cells. Selection for biomass peaks could not be demonstrated using cell volume calculated from microscopic measurement. The 233-μm zooplankton utilized about 10–30% of daily primary production during the bloom.
An Integration of Forest and Lake Fertilization: Transport and Transformations of Fertilizer Elements
Authors: Perrin C. J. , Shortreed K. S. , Stockner J. G.
Published: April 2011

Forest fertilization (435 kg urea∙ha−1) on the Mohun drainage, northern Vancouver Island, during late fall 1979 resulted in a combined increase in urea, ammonia, and nitrate concentrations to 8000 μg N∙L−1 above control levels in streams not protected with 50-m-wide leave (i.e. unfertilized) strips and 350 μg N∙L−1 in those having leave strips. By spring 1980, dissolved nitrogen loads to Mohun Lake increased by a minimum of 55% in the largest basin and 1924% in the smallest basin. This corresponded to fertilizer losses of 2.1% of the total applied from drainages that had leave strips and up to 5.2% from those where the treatment included direct application to stream channels. Nitrogen transport was dominated by reduced nitrogen species and lasted up to 144 d. Relatively small changes in nitrate transport were attributed to low temperatures, which reduced rates of nitrification. Duringthe3-yr prior to forest fertilization, nitrogen and phosphorus were added to the lake at an N:P ratio of 4.5 (wt/wt) and a load of 1.4–2.2 mg P∙m−2∙wk−1. Spring overturn phosphorus concentrations were 4–5 μg∙L−1 throughout the study and, except during the spring following forest fertilization, N:P ratios (NO3-N:TP) at spring overturn were 3–6 (wt/wt). Despite the low ratios, nitrogen-fixing phytoplankton were not dominant in Mohun Lake. After forest fertilization, average epilimnetic chlorophyll concentrations were 1.8 times higher than in 1979, the last year of lake fertilization. The increase is attributed to the much higher spring overturn N:P ratio that occurred after forest fertilization and to phosphorus recycling processes within the extensive littoral zone of the lake.
Development of Larvae of the Saffron Cod, Eleginus gracilis, with Comments on the Identification of Gadid Larvae in Pacific and Arctic Waters Contiguous to Canada and Alaska
Authors: Dunn Jean R. , Vinter Beverly M.
Published: April 2011

A developmental series (4.2–28.7 mm standard length, SL) of larvae and pelagic juveniles of the saffron cod, Eleginus gracilis, from the Bering and Chukchi seas is described and illustrated for the first time. Larvae of E. gracilis hatch at about 3.5 mm SL, and yolk is absorbed by about 6.5 mm SL. Notochord flexion commences at about 11 mm SL and is completed by about 17 mm; transformation to the pelagic juvenile stage occurs at about 24–27 mm SL. Eleginus gracilis larvae are characterized by gut pigment and by the presence of two distinctive postanal bars of pigment. They may be distinguished from other cooccurring gadid iarvae in the Gulf of Alaska (walleye pollock, Theragra chalcogramma; Pacific cod, Gadus macrocephalus; Pacific tomcod, Microgadus proximus) as well as those in the Bering and Chukchi seas south of 70°N (T. chalcogramma, G. macrocephalus, and Arctic cod, Boreogadus saida) based on pigment patterns and meristic characters. Comments are included on the status of knowledge of larvae of three other gadids (in addition to E. gracilis and B. saida) present in North American arctic waters: ogac (Gadus ogac), toothed cod (Arctogadus borisovi) and polar cod (A. glacialis).
Characteristics of a Previously Unidentified Virus from Channel Catfish (Ictalurus punctatus)
Authors: Amend Donald F. , McDowell Terry , Hedrick Ronald P.
Published: April 2011

A virus (strain F82-34) was isolated from channel catfish (Ictalurus punctatus) that was clearly distinct from channel catfish virus (CCV). The virus induced extensive syncytia in channel catfish ovary (CCO) cells incubated at 26 °C. The BB and CHSE-214 cell lines supported virus replication but the FHM line was refractory. Virus replication was optimal at 25 °C where, after 96 h, approximately 50% of the virus was found to be released from CCO cells. Virus infectivity was stable for 1 mo at4, 16, and 23 °C and for 5 mo at −20 and −8Q °C but was lost after 7 d at45 °C. Partially purified virions are double-shelled hexagonal capsids characteristic of reoviruses and have an average diameter of 75 nm. F82-34 was related to but distinct from two other reoviruses from fish in neutralization studies; these three viruses, and possibly a fourth from American oysters (Crassostrea virginica), appear to represent a new taxonomic group within the family Reoviridae. We therefore propose that this new virus be tentatively designated catfish reovirus (CRV).
Seasonal and Phenotypic Variations in Plasma Protein Antifreeze Levels in a Population of Marine Fish, Sea Raven (Hemitripterus americanus)
Authors: Fletcher G. L , Kao M. H. , Haya K.
Published: April 2011

The annual cycle of plasma antifreeze polypeptide levels and Na+and Cl−concentrations were measured in sea raven (Hemitripterus americanus) from a New Brunswick population. Both Na+and Cl−concentrations showed a distinct seasonal cycle, with the highest concentration of both ions occurring during the winter months. Mean plasma antifreeze levels also showed a significant seasonal cycle, with the highest values occurring during winter. Two features of the annual plasma antifreeze cycle differed considerably from the annual cycles observed in other temperate water fish: antifreeze polypeptides were present throughout the year and, during the winter, 40–50% of the fish had antifreeze levels that were the same as those observed during the summer. Thus, our results modify the generally accepted view that the presence of plasma antifreeze proteins correlates with the seasonal period of low water temperatures and that only fish inhabiting polar oceans maintain high levels of antifreeze peptides in their blood all year round.
Excess Unsupported 210Pb in Lake Sediment from Rocky Mountain Lakes: A Groundwater Effect
Authors: Norton Stephen A. , Hess Charles T. , Blake Geneva M. , Morrison Marilyn L. , Baron Jill
Published: April 2011

Sediment cores from four high-altitude (approximately 3200 m) lakes in Rocky Mountain National Park, Colorado, were dated by 210Pb chronology. Background (supported) 210Pb activities for the four cores range from 0.26 to 0.93 Beq/g dry weight, high for typical oligotrophic lakes, integrated unsupported 210Pb ranges from 0.81 (a typical value for most lakes) to 11.0 Beq/cm2. The 210Pb activity in the surface sediments ranges from 1.48 to 22.2 Beq/g dry weight. Sediment from Lake Louise, the most unusual of the four, has 22.2 Beq/g dry weight at the sediment surface, an integrated unsupported 210Pb = 11.0 Beq/cm2, and supported 210Pb = 0.74 Beq/g dry weight. 226Ra content of the sediment is insufficient to explain either the high unsupported 210Pb or the Rn content of the water column of Lake Louise, which averaged 96.2 Beq/L. We concluded that 222Rn-rich groundwater entering the lake is the source of the high 222Rn in the water column. This, in turn, is capable of supporting the unusually high 210Pb flux to the sediment surface. Groundwater with high 222Rn may control the 210Pb budget of lakes where sediment cores have integrated unsupported 210Pb greater than 2 Beq/cm2.
Macroinverfebrate Abundance and Production of Psammophifous Chironomidae in Shifting Sand Areas of a Lowland River
Authors: Soluk Daniel A.
Published: April 2011

Abundance and biomass of benthic macroinvertebrates from shifting sand areas in the bed of the Sand River in central Alberta, Canada, were examined for 1 yr. Macroinvertebrate density ranged from 12 000 to 78 000 individuals/m2, but total biomass was low (50–490 mg/m2 dry mass) due to the small size of most organisms. The interstitial larvae of two chironomid species (Robackia demeijerei and Rheosmittia sp.) contributed a mean of 80.6% biomass and 92.8% of total number of macroinvertebrates. Total annual secondary production of these two species (752.0 ± 144.5 mg∙m−2∙yr−1) was used as an estimate of total secondary production of benthic macroinvertebrates in shifting sand areas. Both R. demeijerei and Rheosmittia sp. exhibited larval growth and development rates much slower than those reported for comparably sized species in other habitats. Food or frequent disturbance may limit the growth of these species. Although unit area biomass and production were low relative to other lotie habitats, shifting sand areas make significant contributions to the river ecosystem because they occupy a large proportion of the river bed.
Year-Class Strength and Survival of O-Group Clupeoids
Authors: Smith Paul E.
Published: April 2011

Global marine fish catch has been stable over the past decade but the clupeoid contribution has declined from one-half to one-third of the marine fish catch. This decline appears to be caused by changes in recruitment success during heavy fishing pressure. Theoretical population approaches and correlative environmental indices are not yet sufficient for setting catch limits. For some time the direct measurement of current biomass appears to be necessary for setting clupeoid quotas. Precision and cost studies on the estimation of biomass with current methods indicate that a standard error of estimate less than 25% cannot be justified based on the increased long-term yield of the stock. Assembly of a prospective life-table for the central subpopulation of the northern anchovy (Engraulis mordax) allows the discussion of intra-population and environmental controls on growth of the population. Using reasonable values for survival and growth in the embryonic, larval, and juvenile stages in the context of a life-table allows one to evaluate the stages where recruitment is controlled. From this manipulation it appears that significant decreases in recruitment could originate at any stage but marked increases in recruitment are only likely to arise from lower mortality rates in the embryonic and larval stages. The late larval stage of the anchovy could exhibit remarkable control on the level of recruitment through plasticity of the interaction between growth rate and survival. Maximum cohort biomass of the anchovy occurs late in the first year of life but current measures of juvenile survival and biological production are inadequate to explore density-dependent survival and growth rates.
Spatial Configurations of Young Herring (Clupea harengus harengus) larvae in the St. Lawrence Estuary: Importance of Biological and Physical Factors
Authors: Henri M. , Dodson J. J. , Powles H.
Published: April 2011

The phenomenon of larval retention has recently been identified as central to the structuring of herring stocks. It has been shown that retention of larval fish populations in estuaries is dependent on active vertical migration, the capacity for which develops with growth, but the present study shows that mechanisms for spatial structuring of larval herring (Clupea harengus harengus) populations act at the earliest (yolk sac and post-yolk sac) stages. The study was carried out on the Isle-Verte stock of the St. Lawrence estuary in 1981 and 1982. Length–frequencies and tide-related abundance fluctuations suggested that larvae are retained in the study area. As a result, larvae remain aggregated throughout the sampling period of approximately 1 mo. Yolk sac larvae were significantly more abundant near the bottom than in the water column, while post-yolk sac larvae were significantly less abundant in the suprabenthic layer than in the water column. Larvae, being negatively buoyant, tend to sink in slack water but are transported upwards by turbulence resulting from tidal flows. The extent of vertical transport of larvae in the water column is greatest for larvae with lesser specific gravities; specific gravity is at a maximum at hatching and decreases to a minimum at yolk sac absorption. We conclude that larval specific gravity, current velocity, and the two-layer residual circulation are the major factors causing retention and aggregation of larvae.
Morphological Comparison of Two Northwest Atlantic Redfishes, Sebastes fasciatus and S. mentella, and Techniques for Their Identification
Authors: Kenchington T. J.
Published: April 2011

A knowledge of the taxonomy of the Atlantic redfishes, Sebastes spp., and techniques for their field identification are essential prerequisites for rational management of their fishery, but both remain poorly known. Through analysis of a set of morphological data for Sebastes fasciatus and S. mentella of the Scotian Shelf, using multivariate techniques, I examined the potential of 15 characters as field identifiers. Although the species are significantly different, they cannot be fully separated using these characters. I suggest that electrophoretic techniques are needed for precise identifications, although a rapid method for determining the species compositions of large samples, using anal fin ray counts, could be developed.
Empirical Prediction of Crustacean Zooplankton Biomass in Nutrient-Poor Canadian Shield Lakes
Authors: Yan N. D.
Published: April 2011

A comparison of the predictive power of nine existing empirical zooplankton biomass models indicated that lake water phosphorus concentration may be a better predictor of zooplankton biomass in Canadian Shield lakes than phytoplankton biomass, chlorophyll a, midsummer epilimnetic temperature, mean surface water temperature, mean depth, and Carlson's trophic state index. To develop models specifically applicable to nutrient-poor Canadian Shield lakes, a variety of morphometric, chemical, and planktonic parameters were assessed for three consecutive years from 16 Canadian Shield lakes in south-central Ontario. Total nitrogen was the best univariate predictor of zooplankton biomass for data averaged over single ice-free seasons, but total phosphorus was the best predictor when data were averaged over the entire study period. Consideration of pH and maximum depth improved certain models. Total phosphorus is clearly a good predictor of (long-term) average zooplankton biomass in nutrient-poor lakes as it is in lakes exhibiting a wide range in trophic state.
Accumulation of Cadmium by White Suckers (Catostomus commersoni) in Relation to Fish Growth and Lake Acidification
Authors: Bendell-Young Leah I. , Harvey Harold H. , Young Jeffrey F.
Published: April 2011

The liver, kidney, muscle, and bone tissues of white suckers (Catostomus commersoni) captured from six lakes in south-central Ontario were analyzed for Cd content. The lakes ranged in pH from 4.8 to 6.4 and contained elevated Cd concentrations in the recently deposited sediments. Cd was found to be bioaccumulating in the livers of fish from both acid and circumneutral lakes, with fish from (acid) George Lake (ages 2–5) and (neutral) Red Chalk Lake (ages 7–14) containing similar concentrations. Calculated growth constants for each of the six populations revealed considerable variations in fish growth rates. A method is presented which represents the age, weight, and tissue Cd concentrations data for the six populations such that interlake comparisons of metal bioavailability can be made with the possible effects that the different fish growth rates may have on rates of metal accumulation factored out. When presented in this manner, our results imply that, on the linear portion of the growth curve, the growth rates of each population, and not effects due to lowered lake pH, can account for the concentrations of Cd in five of the six fish populations. Therefore, since tissue-metal concentrations in fish from stressed lakes will be dependent on both metal bioavailability and fish growth rates, it is essential that these be reported together.
Evaluation of Factors Related to the Unusually Low Chlorophyll Levels in Prairie Saline Lakes
Authors: Campbell C. E. , Prepas E. E.
Published: April 2011

Prairie saline lakes in Canada have remarkably low chlorophyll a (Chl a) levels relative to total phosphorus (TP) and total nitrogen (TN) levels. To evaluate factors related to low Chl a levels, three Alberta saline lakes (total dissolved solids > 5 g∙L−1) were studied in 1983 and 1984. Mean summer phytoplankton Chl a ranged from 3 to 10 μg∙L−1, mean summer periphyton Chl a was less than 70 mg∙m−2, while mean summer TP and TN ranged from 2 to 13 and from 4 to 11 mg∙L−1, respectively. Chl a and phytoplankton primary production were extremely low relative to predictions from measured TP and TN levels and empirical models for freshwaters. Bioassays indicated that inorganic phosphorus was not limiting, whereas inorganic nitrogen was limiting algal growth. Bacterial densities and zooplankton dry weight were high (> 107 cells∙mL−1 and > 1.0 mg∙L−1, respectively) relative to predictions from Chl a and empirical models for freshwaters. Phytoplankton biomass was insufficient to maintain the zooplankton populations; bacteria and detritus were likely a major food source for zooplankton. This study suggests that freshwater models are not applicable to prairie saline lakes.
Exclusion of Adult Alewife, Alosa pseudoharengus Using Low-Frequency Sound for Application at Water Intakes
Authors: Haymes Gerard T. , Patrick Paul H.
Published: April 2011

Experiments to test the effectiveness of low-frequency, high-intensity sound in excluding alewife, Alosa pseudoharengus, from an experimental net structure were conducted on Lake Ontario near Pickering, Ont. Sound was generated by modified seismic devices called pneumatic poppers. The number of alewife entering the experimental structure was reduced by 71–99% when the poppers were operating. Sonar evidence from one test suggested that another species which was not caught in the collection nets was less influenced by the acoustic deterrent. The results suggest that low-frequency, high-intensity sound may be effective in reducing losses of adult alewife at water intakes.
Growth Patterns in Bluegill (Lepomis macrochirus) and Pumpkinseed (L. gibbosus) Sunfish: Environmental Variation and the Importance of Ontogenetic Niche Shifts
Authors: Osenberg Craig W. , Werner Earl E. , Mittelbach Gary G. , Hall Donald J.
Published: April 2011

Size-specific growth rates were determined for bluegill (Lepomis macrochirus) and pumpkinseed (L. gibbosus) sunfish collected between 1978 and 1985 in nine lakes in southwestern Michigan. Variation in growth rates was attributable to lake effects as well as an interaction between lake and year effects. Year effects explained none of the observed variation, suggesting that growth rates were influenced more by unique lake differences than by annual climatic differences. Analyses of the covariation in growth among different size-classes of bluegill and pumpkinseed revealed that small bluegill (< 55 mm standard length (SL)) and small pumpkinseed (< 40 mm SL) exhibited similar responses to environmental factors, while large bluegill (> 55 mm SL) and large pumpkinseed (> 50 mm SL) responded differently. These breaks in the growth patterns coincide with the sizes at which each species exhibits an ontogenetic shift in diet. Comparison of growth rates and resource densities suggests that the growth rates of the large fishes were food limited. Small fishes showed significant density-dependent growth. This correlative evidence for competition is in agreement with recent experimental work. We suggest that the competition between juvenile sunfishes is driven by the effects of adult resources on adult performance and the eventual recruitment of juveniles into the littoral habitat.
Effects of Water Acidity on Swimbladder Function and Swimming in the Fathead Minnow,Pimephales promelas
Authors: Jansen Wolfgang A. , Gee John H.
Published: April 2011

Swimbladder function, buoyancy-related behavior, and swimming performance were examined in fathead minnows (Pimephales promelas) following chronic (>4 d) exposure to acid-treated water (pH 5.3). When denied surface access in still water, treated fish, unlike controls (pH 7.7), failed to increase buoyancy and standard volume over "access to air" levels and had significantly higher proportions of swimbladder CO2and O2. In current, treated fish reduced buoyancy over 48 h to a lesser extent than controls and were severely limited in their ability to increase internal pressure of swimbladder gases. pH significantly affected the maintenance of a minimum buoyancy over 32 d. Upon transfer from current to still water without access to air, the rate of buoyancy adjustment over 48 h was significantly slower in treated fish. With surface access, fish of both groups filled swimbladders within 6–12 h following removal from current; however, treated fish displayed significantly lower proportions of swimbladder CO2and O2at 12 and 24 h. Both groups of fish compensated hydrodynamically for insufficient static lift with higher frequencies of pectoral fin beats, treated fish having generally higher frequencies. Swimming performance was unaffected by water pH, but treated fish lost more weight than controls. We propose that impaired swimbladder function contributes to the elimination of fathead minnows from acidified environments.
Significance of the Functional Response of Predators to Changes in Prey Abundance in Multispecies Virtual Population Analysis
Authors: Hisdén Mskael
Published: April 2011

Recent applications of multispecies assessment methods (MSVPA) to North Sea Fish stocks indicate that MSVPA and single-species assessments give highly corrected recruitment estimates. This may be an artifact due to the choice of the relationship between predation mortality and prey cohort size. If the predation mortality is an increasing function of prey cohort size over a certain range of cohort sizes, even a constant predator biomass may cause fluctuations in the number of fish recruiting to the fishable part of the population. Thus the correlation between single-species and multispecies recruitment estimates may be lower than earlier analyses have suggested, and changes in predation mortality may have caused fluctuations in year class strengths which previously have been attributed to unspecified environmental conditions. Because a relatively minor alteration of the predation function can cause such a drastic change in the perceived dynamics of the fish stocks, I suggest that more studies of the predation processes in fish communities are needed before one can hope to gain deeper insights into the recruitment of fish stocks by applying multispecies assessment methods.
Morphological Deformities in Chironomus, Cryptochironomus, and Procladius Larvae (Diptera: Chironomidae) from Two Differentially Stressed Sites in Tobin Lake, Saskatchewan
Authors: Warwick W. F. , Tisdale N. A.
Published: April 2011

Morphological deformities in Chironomus plumosus type larvae from two differentially stressed sites in the Tobin Lake reservoir are described and compared. The frequency of deformities was 41.3% at Site 2 where larvae are directly exposed to contaminants entering the reservoir from the Saskatchewan River. At Site 17, where larvae are only indirectly exposed in a backwater area, the frequency was 31.8%. The frequency of deformities was higher at Site 2 in all head capsule structures except antennae. At Site 17, the significantly higher frequency of antennal deformities suggests that (1) antennae respond to contaminants according to a quantal dose–response relationship, (2) antennae and other head capsule structures may respond through different mechanisms or at different rates, or (3) other environmental factors may modify larval responses to contaminants. Descriptions of the deformities in other head capsule structures provide a framework for individual indices of severity of deformation similar to that developed previously for antennae. These eventually will be incorporated into an Index of Total Morphological Response. Deformities in Procladius and Cryptochironomus larvae are also described.
Time Series Models of the Maine Lobster Fishery: The Effect of Temperature
Authors: Fogarty Michael J.
Published: April 2011

I used Box–Jenkins transfer function models to analyze the relationship between water temperature and Maine lobster catch and catch-per-unit-effort (CPUE). I first modelled catch and CPUE with univariate autoregressive – integrated moving average (ARIMA) models to provide a basis for comparison with transfer function models. Time series models were constructed for annual Maine lobster landings during two periods: 1928–85 and 1945–85; catches during the latter period were assumed to be less dependent on changes in fishing effort. I also modelled annual CPUE for the period 1930–85 and monthly landings for 1968–85. Landings and CPUE for 1986 were held in reserve to check forecast estimates. An immediate temperature effect (lag 0–1 yr) was demonstrated for each annual series. This result is consistent with known aspects of lobster biology; activity levels and hence vulnerability to capture increase with water temperature. In addition, the probability of molting increases with increasing water temperature, affecting the short-term supply of legal-sized lobsters. A significant effect of temperature at a 6-yr lag was also indicated, but only for the 1945–85 catch series. Delayed effects of this type may indicate environmental influences on natality or survival during early life history stages. Time series models for the Maine lobster fishery provided forecasts for 1986 catch and CPUE which differed by no more than 4% of the actual 1986 levels.
Growth Inhibition, Gluconeogenesis, and Morphometric Studies of the Pituitary and Interrenal Cells of Acid-Stressed Brook Trout (Salvelinus fontinalis)
Authors: Tam W. H. , Fryer J. N. , Ali I. , Dallaire M. R. , Valentine B.
Published: April 2011

Somatic growth was stunted in yearling brook trout (Salvelinus fontinalis) maintained for up to 73 d in pH 4.5. Plasma cortisol level increased in pulses after 1.5 h (from 10 to 82.3 ng∙mL−1) on days 4 (46 ng∙mL−1) and 15–30 (20–25 ng∙mL−1) of acid treatment. Interrenal nuclear hypertrophy and cell hyperplasia occurred respectively on days 4 and 15. Electron microscopic observations revealed that the somatotropes and thyrotropes were atrophic for about half of the experimental period whereas the corticotropes displayed sustained hypertrophy. Plasma glucose and amino acid levels rose simultaneously by 300–600 and 130%, respectively, from day 4 of acid exposure. Hepatic L-alanine aminotransferase activity increased on day 30 just as plasma protein concentration began to decline. When adrenalin and cortisol acetate were administered to trout maintained in neutral pH to raise circulating cortisol levels from 10–20 to 1876 ng∙mL−1, blood glucose remained normal up to 6 d after treatment. These results suggested that acid stress suppressed somatotropin, thyrotropin, and indirectly thyroid hormone secretion but stimulated the pituitary–interrenal axis, leading to inhibition of protein synthesis and accumulation of amino acids in the circulation. The elevation of blood sugar level was caused by some as yet unidentified factors.
Prolactin Cell Cytology, Plasma Electrolytes, and Whole-Body Sodium Efflux in Acid-Stressed Brook Trout (Salvelinus fontinalis)
Authors: Fryer J. N. , Tam W. H. , Valentine B. , Tikkala R. E.
Published: April 2011

Twelve-month-old brook trout (Salvelinus fontinalis) of both sexes were exposed to acidified water (pH 4 5) for a period of 52 d. Ultrastructural morphometric studies of the prolactin cells of the pituitaries of acid-stressed female trout revealed a reduction, after a latent period of about 1 wk, in prolactin cell area, cytoplasmic area and nuclear area which gradually recovered to control values by day 52 of acid exposure. In both male and female trout, acid exposure resulted in significant decreases in plasma osmolarity, and plasma sodium, which gradually returned to control values by day 52 of the study. Total plasma calcium was not altered by acid exposure in either male or female trout. For both male and female trout, acid exposure resulted in transient elevations in haematocrit and a prolonged suppression of blood pH. The whole-body sodium efflux for trout introduced into dechlorinated tap water or distilled water was significantly greater at pH 4.5 than at pH 7.35. Possible relationships between the acid-induced inhibition of the secretory activity of the prolactin cells and impairments in osmotic and ionic regulation observed in acid-stressed trout are discussed.