bluuebunny/crossref_metadata_2025 huggingface dataset:
Methods of Time Trends Analysis Applied to Contaminant Levels in Canadian Atlantic Cod (Gadus morhua)
Authors: Misra R. K. , Uthe J. F.
Published: April 2008

Similarities and differences between multiple linear regression (MLR) and analysis of variance (ANOVA) approaches which have been used as two seemingly different methodologies in time trend studies are explained. Difficulties encountered in choosing an appropriate MLR model are presented, and need for identifying outlying observations in a MLR analysis is emphasized. Univariate analyses such as MLR and ANOVA are of restricted scope and may even be misleading when employed on data sets containing several contaminants. Multivariate structures of these data sets have distinct advantages over a univariate model. The use of multivariate analysis of covariance (MANCOVA) for time trends investigation is illustrated with Canadian Atlantic cod (Gadus morhua) data. Significant linear time trends are shown, although these did not explain all variations between years.
Increased Growth Rate in Atlantic Salmon Parr (Salmo salar) by Using a Two-Coloured Diet
Authors: Jakobsen Per Johan , Johnsen Geir Helge , Holm Jens Christian
Published: April 2008

Fishes hunting by sight are known to pay a cost of confusion when faced with high densities of uniform food particles. Factors such as swarm size, density, and visual uniformity increase confusion. Therefore, it may be profitable in pisciculture to introduce food particles in low densities or to reduce the uniformity and density of each type of feed pellet. This was tested by feeding Atlantic salmon parr (Salmo salar) brown pellets, yellow pellets, or a mixed diet. Mean growth rates were significantly higher for those fish fed a mixed diet. Of the smaller fish in all groups, those in the mixed diet group showed the highest weight/length ratio. We suggest that small individuals have to pay more attention to conspecifics than do large ones, and thus tolerate less confusion when feeding. Larger individuals, tolerating higher confusion costs, achieve higher feeding rates in high densities of uniform feed pellets.
Aluminum, Iron, Zinc, and Lead in Bog Waters of Northeastern North America
Authors: Urban Noel R. , Eisenreich Steven J. , Gorham Eville
Published: April 2008

Aluminum, iron, zinc, and lead were measured in 37 surface waters from 24 bogs along an east to west transect from Manitoba and Minnesota to Maine and the Atlantic Provinces of Canada. The major influence upon Al and Fe is atmospheric deposition of soil particles. Zinc and Pb are derived primarily from air pollution. Concentrations of Al and Fe in bog waters greatly exceed those in regional atmospheric precipitation; dry deposition and evaporative concentration are the likely explanations. Concentrations of Zn and Pb are less than those in precipitation, presumably due to sorption by peat.
Influence of Complexation and pH on Individual and Combined Heavy Metal Toxicity to a Freshwater Green Alga
Authors: Starodub M. E. , Wong P. T. S. , Mayfield C. I. , Chau Y. K.
Published: April 2008

The effect of complexation and pH on heavy metal (Cu, Zn, Pb) toxicity to a freshwater green alga, Scenedesmus quadricauda, was investigated. Extracellular ligands produced by S. quadricauda were capable of binding heavy metals and reducing their single and combined toxicities. Apparent complexing capacities and the ability of the sediment humics and artificial complexing agents such as ethylenediaminetetraacetic acid (EDTA), citric acid, and glycolic acid to ameliorate Cu, Zn, or Pb toxicity were also assessed. The toxicity of metals to algal growth was enhanced at acidic pH. Combined toxicity of these metals was significantly greater at pH 4.5 than at pH 8.5 or pH 6.5. Synergistic effects (between Cu, Zn, and Pb) towards algal growth increased at low pH. Specific heavy metals, their respective concentrations, the presence of complexing ligands, and pH influence both individual and combined heavy metal toxicities.
Tumors in Cetaceans: Analysis and New Findings
Authors: Geraci J. R. , Palmer N. C. , St. Aubin D. J.
Published: April 2008

We describe 14 tumors, including 5 leiomyomas, 6 papillomas, 2 adrenal adenomas, and a bronchogenic carcinoma collected from over 1800 free-ranging and captive cetaceans examined since 1973. These bring to 41 the number of confirmable tumors reported from cetaceans. Of the 52 cases previously reported, 23 were described in sufficient detail to confirm the diagnoses, 15 were considered probable, and 4 were reclassified. Organ systems most commonly affected were the gastrointestinal tract (31%), skin (24%), and female reproductive tract (21%). Sampling bias may account for this apparent trend. Etioiogic agents have rarely been identified, and attempts to do so are hampered by inadequate sample sizes.
Effect of Surface Access and Oxygen Concentration on the Toxicity of Croton tiglium (Euphorbiaceae) Seed Extract to Brachydanio rerio (Cyprinidae)
Authors: Kulakkattolickal Augusthy Thevasia , Kramer Donald L.
Published: April 2008

Zebrafish (Brachydanio rerio) (Cyprinidae) were exposed to a toxic extract of Croton tiglium (Euphorbiaceae) seeds (4 mg∙L−1) at 0.8, 1.1 and 8.1 mg O2∙L−1, with and without surface access. Equilibrium loss occurred more quickly at lower dissolved oxygen concentrations. At 0.8 and 1.1 mg O2∙L−1, equilibrium loss also occurred more quickly when access to the water surface was denied. Surface access is therefore an important factor in studies of the interaction between toxicity and dissolved oxygen concentration. We suggest that, by performing aquatic surface respiration, zebrafish with surface access in hypoxic water reduce their ventilation rate and hence their uptake rate of toxins.
Dual Tracer Studies of the Assimilation of an Organic Contaminant from Sediments by Deposit Feeding Oligochaetes
Authors: Klump J. Val , Krezoski John R. , Smith Michael E. , Kaster Jerry L.
Published: April 2008

The assimilation of [14C]2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) from Lake Michigan sediments by oligochaete worms was determined in laboratory microcosms using dual tracer techniques. Particle size selective feeding by oligochaetes makes single tracer calculations of assimilation from bulk feces subject to errors resulting from the changing distribution coefficients of adsorbed constituents as a function of particle size. 51Cr3+ adsorbed to sediments passes through the guts of worms without being assimilated and serves as a conservative tracer of ingestion. Assimilation efficiencies for HCBP decreased from 36 to 15% over the initial 10 d of active feeding and was inversely related to average defecation rate which increased from 0.05 to 0.25 mg sediment∙mg worm−1∙h−1 over the same period. In combination with measured defecation rates, assimilation efficiencies were used to estimate HCBP uptake rates of 3.9–8.1 pmol∙mg worm−1∙h−1. Assimilation efficiencies appear to be dependent upon gut clearing times which are a function of both gut volume and feeding rate and which are estimated to vary from <1 to >5 h.
Mortality Variations in Natural Populations of the Blue Mussel, Mytilus edulis
Authors: Mallet A. L. , Carver C. E. A. , Coffen S. S. , Freeman K. R.
Published: April 2008

To investigate environmental and seasonal patterns of mortality among natural populations of the blue mussel, Mytilus edulis, we transplanted 11 stocks of juvenile mussels to nine sites along the coast of Nova Scotia, Canada. Stock, Stock by Site, and Stock by Season together accounted for 53% of the variance in mortality whereas Site and Season together explained less than 1% of the variance. Genetic variability among stocks was inferred from differences in their cumulative mortality averaged over all environments. Several stocks, however, exhibited similar levels of mortality over all sites and were apparently insensitive to the environmental gradient. This implies physiological flexibility or the ability to tolerate a wide range of environmental conditions. We conclude that the blue mussel adapts to variable environments by maintaining both physiologically flexible and genetically variable populations. In addition, we noted that stocks originating from more stressful environments tended to exhibit lower mortalities than those originating from less stressful environments.
Interactions Between the Redside Shiner (Richardsonius balteatus) and the Steelhead Trout (Salmo gairdneri) in Western Oregon: The Influence of Water Temperature
Authors: Reeves Gordon H. , Everest Fred H. , Hall James D.
Published: April 2008

Water temperature influenced interactions between redside shiner (Richardsonius balteatus) and juvenile steelhead trout (Salmo gairdneri) (≥1 +) in the field and laboratory. Trout in cool water when shiner were absent and at intermediate water temperatures with shiner present occupied a similar range of habitats. Shiner alone in warm water occupied habitats similar to trout, but in the presence of trout occupied slower, deeper areas than when alone. In laboratory streams, production by trout was the same in the presence and absence of shiner in cool water (12–15 °C). In warm water (19–22 °C), production by trout decreased by 54% in the presence of shiner compared with when shiner were absent. Production of shiner in cool water decreased in the presence of trout, −0.3 g∙m−2∙d−1 together compared with 0.5 g∙m−2∙d−1 alone, but was not affected by the presence of trout in warm water. Trout distribution was not influenced by shiner in cool waters, but was influenced at warm temperatures. Shiner occupied all areas of the laboratory channels in the absence of trout in cool waters but were restricted to a few pools in the presence of trout. Distribution of shiner was not influenced by trout at warm temperatures.
Effects of Exercise Training on the Performance, Growth, and Protein Turnover of Rainbow Trout (Salmo gairdneri)
Authors: Houlihan D. F. , Laurent P.
Published: April 2008

Rainbow trout (Salmo gairdneri) that were made to swim continuously at 1 body length/s for 6 wk had double the growth rate of tank-rested control fish. The endurance to fatigue at a range of swimming velocities of these trained animals was significantly better than that of the controls. Measurement of the rate of protein synthesis in the tissues was carried out by the free pool flooding technique. Protein degradation rates were calculated from the difference between synthesis and net protein accretion. In controls and trained animals the fractional rates of protein synthesis and degradation were ranked gills > ventricle > red muscle > white muscle whereas the efficiencies of conversion of protein synthetised into protein retained as growth were in the reverse sequence. Synthesis rates in three of the four tissues of the trained animals were approximately double those of the control animals. Calculated degradation rates of proteins also increased in the trained animals; the increased growth rates resulted from the proportionately greater increase in the rate of synthesis. The rate of synthesis decreased to control levels once the trained animals ceased swimming.
Latitudinal influences on the Depths of Maximum Colonization and Maximum Biomass of Submerged Angiosperms in Lakes
Authors: Duarte Carlos M. , Kalff Jacob
Published: April 2008

Both water transparency and lake latitude influence the depths of maximum biomass (Zb) and maximum depth of colonization (Zc) of submerged plants. The differences in the depth distribution of plants in lakes differing in water transparency become more pronounced as latitude decreases. Changes in transparency in low-latitude lakes should result in greater changes in macrophyte cover than similar changes in lakes at higher latitudes. The maximum depth of colonization appears to be largely a function of water transparency, whereas the depth of maximum biomass is best related to latitude. Relationships developed here allow better predictions of Zc and Zb for individual lakes than were possible before.
Effects of Nutrient Pulses on Community Structure and Cell Size of a Freshwater Phytoplankton Assemblage in Culture
Authors: Suttle C. A. , Stockner J. G. , Harrison P. J.
Published: April 2008

A natural assemblage of phytoplankton was removed from an oligotrophic lake and grown in semicontinuous culture under three nutrient addition frequencies, ranging from one addition every 4 d to one addition every 16 d. Changes in community structure, cell size, and nutrient chemistry were determined at several times during the 35-d experiment. Under the least frequent nutrient addition regime, cultures were dominated by Tabellaria fenestrata; in contrast, when nutrients were added more often, Synedra radians was dominant. As well as causing a shift in species composition, under the once per 16 d nutrient addition frequency the average cell volume increased from approximately 500 to 1300 μm3. This was mainly the result of the larger size of T. fenestrata, but was also in part because of an increase in the cell size of S. radians. It is argued that cells which are able to sustain elevated maximum uptake rates, and which are able to store the largest amount of nutrient relative to their minimum requirements, should be successful under conditions where saturating pulses of limiting nutrients occur.
Ecology and Growth of Postlarval and Juvenile Lobster, Homarus americanus, off Îles de la Madeleine (Quebec)
Authors: Hudon Christiane
Published: April 2008

Lobsters, Homarus americanus were studied in various habitats off Îles de la Madeleine, Quebec, from June to October 1985. Density, biomass, and size structure were estimated quantitatively using underwater corrals (40 m2) on rocky bottoms or transects (200 m2) on sandy bottoms and eelgrass beds. On the basis of behavioural observations during capture, lobsters were divided into postlarvae (<25 mm carapace length, CL), juveniles (25–76 mm CL), and adults (>76 mm CL). Density, biomass, and size structure were closely related to the coarseness of the bottom. Density and biomass were greater and mean size was larger on algae-covered boulders than on bare stones. Postlarval and juvenile lobsters were most numerous on shallow rocky bottoms where high densities (0.8–3.8 ind∙m−2) of small lobsters (mean size from 23.8 to 35.5 mm CL) were captured. Low density of juveniles and adults occurred on sand covered with eelgrass. No resident lobsters were found on bare sand. Temporal variation of postlarval density was synchronous at the three stations investigated. Postlarval density decreased during the summer until the settlement of planktonic postlarvae in mid-August. Moulting activity occurred throughout the summer, with a peak in early July. Mean size values for stages V–XIV were fitted to the cumulated size distribution and were used to calculate the percent increment for each moult stage (growth factor) and the expected duration of each stage. The 2-mo duration of the stage IV settlement period could result in a size range of 6–21 mm CL (mean size 14.5 mm CL, stage VIII) for a cohort by the end of its first season of benthic growth. The transition from planktonic to benthic life was characterized by a decrease of the growth factor at stage V, which was subsequently compensated at stages VI and VII by high growth factor values. In the first three growth seasons, spring and summer moults exhibit higher growth factor values than fall moults. These seasonal variations result in regular oscillations of the growth factor dampening progressively between stages V and XIV, instead of the smooth decline hypothesized in previous studies. A combination of factors, such as cryptic behaviour, high substrate selectivity, gradual settlement over the late summer months, and variability in growth factor, reflect the very fine tuning of the lobster's early benthic life stages to the constraints of its physical environment.
Contribution of Calcite to the Particle-Size Spectrum of Lake Michigan Seston and Its Interactions with the Plankton
Authors: Vanderploeg Henry A. , Eadie Brian J. , Liebig James R. , Tarapchak Stephen J. , Glover Rebecca M.
Published: April 2008

We determined the contribution of calcite to the total particle-size spectrum of Lake Michigan seston during different seasons in 1978–83 and 1985, employing a novel Coulter counter method, to examine the intensity and ecological effects of calcite whitings that result from autogenic precipitation of calcite. The whitings were most intense during September, when 12–56% of the total particle volume was calcite. Overall, food web dynamics were more controlling of than controlled by whitings. Year-to-year variation in calcite concentration was probably caused by predation-controlled variation in primary production, which drives calcite precipitation through CO2 uptake. Feeding rate of cladocerans in Lake Michigan is slightly reduced (16%) by calcite, but that of copepods is not. Light extinction is only slightly increased. Coprecipitation and sinking of P with calcite is probably a minor factor in regulating P concentration in the epilimnion of Lake Michigan. Removal of nutrients is enhanced by increased sinking rates caused by inclusion of calcite in fecal pellets and matter. Although all of the effects of calcite on plankton dynamics appear to be subtle in Lake Michigan, large effects can be expected for lakes of greater calcium hardness and eutrophy.
Size and Age at Metamorphosis in Marine Fishes: An Analysis of Laboratory-Reared Winter Flounder (Pseudopleutonectes americanus) with a Review of Variation in Other Species
Authors: Chambers R. Christopher , Leggett William C.
Published: April 2008

Offspring of adult winter flounder (Pseudopleuronectes americanus) collected from Conception Bay, Newfoundland, were reared from fertilization to metamorphosis. We tested two hypotheses: 1) length and age at metamorphosis are equally variable among individuals and (2) length and age at metamorphosis are not correlated. Length at metamorphosis was significantly less variable than age at metamorphosis when data from all laboratory populations were pooled and in 15 of 18 populations. Coefficients of variation for length and age at metamorphosis for the pooled data were 0.051 and 0.123, respectively. Length and age at metamorphosis were positively correlated when the data were pooled (r = 0.42, p < 0.001) and within 8 of 18 populations. Larvae that metamorphose late do so at larger sizes. When length and age at metamorphosis were converted to growth and developmental rates for the full larval period, significant positive correlations were evident between these rates for the pooled data (r = 0.68, p < 0.001) and within 16 of 18 populations. Larvae that grow slowly, therefore, remain as larvae longer. An examination of published values on size and age at metamorphosis in marine fishes revealed a pattern consistent with our findings both within and among populations and environments: (1) variation in length was less than variation in age at metamorphosis and (2) positive correlations between growth and developmental rates were evident through the larval period. Increased size at metamorphosis may ameliorate competitive effects and reduce the risk of predation in the period immediately following metamorphosis. Due to the considerable variation in the duration of the larval period (age at metamorphosis) the number of individuals that successfully metamorphose and subsequently enter the mature population could be significantly altered under differing environmental conditions.
Histopathoiogy and the Pathogenesis of Embolism (Gas Bubble Disease) in Rainbow Trout (Salmo gairdneri)
Authors: Machado J. P. , Garling Jr. D. L. , Kevern N. R. , Trapp A. L. , Bell T. G.
Published: April 2008

Rainbow trout (Salmo gairdneri) affected with gas bubble disease (GBD) were examined histologically to determine the pathogenesis of the early stages of gas emboli formation. Lesions preserved by a rapid fixation method were located in tissues associated with acid-secreting glands or with high metabolic requirements. Following the development of small gas emboli formed in the retinal chorio-capillaries, a progressive development of unilateral exophthalmia was detected. A lesion found in every treated moribund fish but never in controls was gas displacement of the blood from the afferent arteriole within the gill filaments. The exposure of fish to well water containing graded levels of atmospheric gases from 114 to 118% nitrogen and 103 to 110% oxygen saturation resulted in high mortality. However, fish held in nitrogen varying between 103 and 117% and oxygen from 50 to 94% saturation experienced insignificant mortality. We suggest that hatchery oxygen levels should be maintained below 100% if nitrogen supersaturation is present to reduce mortality from GBD.
Dietary Protein Requirements of Fishes — A Reassessment
Authors: Bowen Stephen H.
Published: April 2008

It is widely believed that fishes require more dietary protein than other vertebrates. Many aspects of fish physiology, nutrition, and trophic ecology have been interpreted within the context of this high protein requirement. Here, fishes are compared with terrestrial homeotherms in terms of (1) protein requirement for maintenance, (2) relative protein concentration in the diet required for maximum growth rate, (3) protein intake rate required for maximum growth rate, (4) efficiency of protein retention in growth, and (5) weight of growth achieved per weight of protein ingested. The two animal groups compared differ only in relative protein concentration in the diet required for maximum growth rate. This difference is explained in terms of homeotherms' greater requirement for energy and does not reflect absolute differences in protein requirement. The remaining measures of protein requirement suggest that fishes and terrestrial homeotherms are remarkably similar in their use of protein as a nutritional resource. Reinterpretation of the role of protein in fish physiology, nutrition, and trophic ecology is perhaps in order.
Influence of Prey Type on Growth of Young Yellow Perch (Perca flavescens)
Authors: Confer John L. , Lake Gary J.
Published: April 2008

Growth of age 0 + yellow perch (Perca flavescens) fed different zooplankton diets was examined in the laboratory during June and July 1983. Fish were fed an equal mass of diet types that varied with respect to prey species, mean length of the same prey species, and species mixture. Fish consumed all prey within 4 h of feeding. In four trials the ranking of diet type by fish growth was always Diaptomus sicilis > Oneida Lake tow sample > Daphnia spp. Differences in fish growth frequently varied by 50–300%. These differences suggest that nutritional processes, such as digestion or assimilation, will influence the optimal prey selection for, at least, small zooplanktivorous fish.
Effect of the Outflow from the Gulf of St. Lawrence on Nova Scotia Shelf Zooplankton
Authors: Sameoto D. D. , Herman A. W.
Published: April 2008

Significant differences in concentrations (per square metre) of the copepods Calanus glacialis and C. hyperboreus found between the northeastern (NE) and southwestern (SW) halves of the Scotian Shelf were apparently related to the Gulf of St. Lawrence outflow. This outflow introduces these species to the Shelf during late winter and early spring and is probably responsible for maintaining their populations on the Shelf. Deep basins on the NE half of the Shelf are also sources of breeding animals of these two species. The influence of the Gulf outflow on C. finmarchicus was less clear because a large population of this species was found in the basins and beyond the Shelf break. Temora was the only other copepod genus to show a relationship with the Gulf outflow, indicating that it is carried onto the Shelf from the Gulf. The outflow dominated the surface water of the NE Shelf over the entire year; its influence was less marked on the SW Shelf due to mixing with slope water. This mixing in turn dilutes the concentrations of the Gulf Calanus spp. introduced by the Nova Scotia Current. The Gulf outflow is responsible for the high zooplankton biomass concentrations on the NE Shelf in June and October.
Influence of Water Clarity on the Catchability of Six Freshwater Fish Species in Bottom Trawls
Authors: Buijse Anthone D. , Schaap Leendert A. , Bust Tammo P.
Published: April 2008

Bottom trawl surveys are carried out every autumn to estimate the relative abundance of six major fish species, especially that of pikeperch (Stizostedion lucioperca) and Eurasian perch (Perca fluviatilis), in the 182 000-ha Lake IJssel, The Netherlands. The catchability of these species is influenced by light intensity at the bottom and therefore by water clarity and water depth. In autumn, water clarity can differ greatly from day to day because of wind-mediated resuspension of sediments. Catchability of ruffe (Gymnocephalus cernua) and age 0 pikeperch showed a significant inverse relationship with light intensity at the bottom, and therefore, a correction should be made when catch data for these species are used to estimate population size or year-class strength. Results were not consistent for perch, while for smelt (Osmerus eperlanus), roach (Rutilus rutilus), and bream (Abramis brama) the influence of light intensity on catchability was not significant. Corrected and uncorrected estimates of the abundance of age 0 pikeperch, based on trawl samples, were compared to demonstrate the effect of water clarity on the estimation of year-class strength. Increased water clarity can lead to zero catches and consequently diminish the effectiveness of sampling programmes.
Seasonal Cycle of Zooplankton off Southwestern British Columbia: 1979–89
Authors: Mackas David L.
Published: April 2008

Average seasonal cycles of zooplankton biomass, species composition, and environmental conditions are estimated from 1979–89 samples collected off the southwest coast of British Columbia. Average total dry weight biomass ranges from a winter minimum <1.5 g/m2 to a late spring maximum >8 g/m2. Three subregions within the study area can be distinguished based on bathymetry and current pattern: the inner shelf banks, the shelf break and slope, and a gyre off the mouth of Juan de Fuca Strait. Total zooplankton biomass, species composition, and seasonality differ sharply between subregions, as do temperature, salinity, and nutrient and phytoplankton distributions. From spring through autumn, there are large inputs of upwelled water (and nutrients) to the continental shelf. Phytoplankton biomass is high, especially in mid- to late summer, and is ample to support growth of herbivorous zooplankton. Despite high food availability and relatively low predation pressure, surface layer zooplankton populations decline on the continental shelf from late spring through autumn, while offshore zooplankton populations increase slowly. A high washout rate due to upwelling and subsequent seaward and alongshore transport is the most plausible explanation. For the continental shelf in summer, the advective component of population turnover is probably larger than local predation mortality.
Comparison of Three Methods of Measuring RNA and DNA Concentrations of Individual Pacific Herring, Clupea pallasi, Larvae
Authors: McGurk Michael D. , Kusser Wolfgang C.
Published: April 2008

Whole-body concentrations of RNA and DNA of individual Pacific herring, Clupea pallasi, larvae were measured with three methods that rely on the fluorescence of dyes bound to nucleic acids. Two methods use the dye ethidium bromide and do not purify nucleic acids, and one method uses ethidium bromide plus the DNA-specific dye bisbenzimidazole and purifies nucleic acids. Highly significant differences in RNA concentration and RNA–DNA ratios were found between the three methods. Significant differences in RNA concentration and RNA–DNA ratios were also found between yolk sac larvae and non-yolk sac larvae analyzed by one of the two ethidium bromide methods, with yolk sac larvae having the lowest ratios. These results suggest that compounds other than nucleic acids may interfere in the two ethidium bromide methods. Until a standard method for extraction and measurement of nucleic acids of larval fish is established, we recommend the use of techniques that purify nucleic acids.
Phytofaun of Eleven Macrophyte Beds of Differing Trophic Status, Depth, and Composition
Authors: Lalonde Sophie , Downing John A.
Published: April 2008

Macrophyte beds in 11 lakes of differing trophic conditions were sampled intensively to examine the influence of macrophyte abundance and composition, epiphyton biomass, phytoplankton concentration, and water depth on the abundance of phytophilous invertebrates. Numerical abundance and biomass of phytofaunal taxa were only weakly correlated. Phytofauna biomass ranged from 17 to 270 mg dry mass∙g macrophyte dry mass−1(1–29 g dry mass∙m−2) among the macrophyte beds. Multiple regression analysis showed that total phytofaunal biomass was positively correlated with the biomass of the three primary producers in the littoral zone: macrophytes, epiphyton, and phytoplankton. Phytofauna biomasses in deeper macrophyte beds or near the water surface were lower than those found in shallower water or near the sediment surface. Correlations of phytofauna biomass with macrophytes, epiphyton, and depth varied somewhat among phytofaunal taxa. The phytofauna biomass was often dominated by chironomid larvae, but gastropods, water mites, and oligochaetes were also important components of the phytofauna biomass. Small crustaceans such as cladocerans and copepods frequently were numerically dominant but usually composed only a small fraction of the biomass. Preference of various invertebrate taxonomic groups for particular species of aquatic macrophyte was slight.
A size and age-structured model of the European eel (Anguilla anguilla L.)
Authors: Leo G. A. De , Gatto M.
Published: April 2008

The life cycle of the European eel (Anguilla anguilla) presents several distinctive features, such as high plasticity in body growth, marked sexual dimorphism, sex ratio strongly skewed in favor of females and sexual maturation largely dependent upon the size of individuals. A demographic model incorporating all these characteristics is derived on the basis of a multiple classification of individuals by age and size, and variability in individual growth is explicitly included. Existing theory for size-structured stocks is extended to include the dependence of sexual maturation on size, while natural mortality is age specific. Using 1989 population data from Comacchio lagoons (Italy), we estimate mortality and metamorphosis rate and abundance in each age- and size-class for both yellow and silver eels, crucial information for the management of the Comacchio fishery. The use of a nonparametric technique (bootstrapping) yields not only the moments, but also the distributions of these estimates. Validation of the model is performed on the data collected in 1990. The approach adopted is very flexible and different assumptions about survival, sexual maturation, and net selectivity can be easily incorporated in the model.
Production of germline transgenic Pacific salmonids with dramatically increased growth performance
Authors: Devlin Robert H. , Yesaki Timothy Y. , Donaldson Edward M. , Du Shao Jun , Hew Choy-Leong
Published: April 2008

Transgenic Pacific salmon have been produced by microinjection of a DNA construct consisting of chinook salmon (Oncorhynchus tshawytscha) growth hormone sequences driven by an ocean pout (Macrozoarces americanus) antifreeze protein promoter. This construct was retained in approximately 4% of fish derived from injected eggs, and resulted in dramatic enhancement of growth relative to controls. For coho salmon (O. kisutch) at 15 months of age, the average size of transgenic fish was more than 10-fold that of controls, with the largest fish more than 30-fold larger than nontransgenic siblings. Dramatic growth enhancement was also observed in transgenic rainbow trout (O. mykiss), cutthroat trout (O. clarki), and chinook salmon using this same gene construct. Transgenic coho salmon underwent precocious parr–smolt transformation during their first fall, approximately 6 months in advance of their nontransgenic siblings. At 2 years of age, five male transgenic coho salmon became sexually mature, and four of these transmitted the gene construct to sperm, the negative fish being transgenic in blood but not fin tissue. These results show that while some fish are mosaic for the gene construct in different tissues, most are transgenic in both germline and somatic tissue.
Experimental assessment of the effect of temperature and salinity on elemental composition of otoliths using solution-based ICPMS
Authors: Fowler Anthony J. , Campana Steven E. , Thorrold Simon R. , Jones Cynthia M.
Published: April 2008

Retrospective determination of the early life history of fish using the microelemental analysis of their otoliths is dependent upon understanding the factors that affect this elemental composition. Here, juvenile Atlantic croaker (Micropogonias undulatus) were reared under different treatments of temperature and salinity to determine their impacts on elemental inclusion rates in otoliths. Solution-based inductively coupled plasma mass spectrometry (ICPMS) was used to measure 21 isotopes in each otolith: isotopic concentrations ranged over seven orders of magnitude, and differed significantly amongst the temperature–salinity regimes. Univariate analyses identified 13 isotopes that contributed to these multivariate differences; the influence of temperature was stronger than that of salinity. Within each treatment there was a significant relationship between otolith microchemistry and otolith size. To some extent this confounded the interpretation of the between-treatment effect of temperature. In contrast, both the otolith and somatic growth rates were similar between the two salinity treatments, indicating that differences in elemental fingerprints were unambiguously related to the salinity difference, probably a response to the elemental concentrations in the tank water. Overall the study highlighted the current poor understanding of the mechanism of contamination of otoliths by trace elements and their incorporation into the otolith microstructure.
Biogeographic patterns of fish species richness in Ontario lakes in relation to historical and environmental factors
Authors: Mandrak Nicholas E.
Published: April 2008

Fish species richness in Ontario lakes was summarized for 80 equal-area quadrats and ranged from 59 species per quadrat in southwestern Ontario to 17 species per quadrat in northern Ontario. Correlograms based on Moran's I coefficient indicated the spatial structure of lake species richness was anisotropic and exhibited a strong south–north gradient of decreasing richness. Relationships among Euclidean distance matrices based on richness, postglacial dispersal, climate, elevation, lake chemistry, and lake morphometry were identified with the aid of the Mantel test and principal coordinates analysis. The presence of spatial autocorrelation may bias matrix correlations; therefore, spatial autocorrelation was removed using the partial Mantel test. The results of the partial Mantel test indicated regional lake species richness was significantly correlated with postglacial dispersal and climate. In particular, the results of principal coordinates analysis identified length of time since deglaciation, length of time covered by glacial lakes, distance from dispersal corridor, and mean annual air temperature as the dominant variables in these data sets.
Seasonal, inverse cycling of length- and age-at-recruitment in the diadromous gobies Sicydium punctatum and Sicydium antillarum in Dominica, West Indies
Authors: Bell Kim N. I. , Brown Joseph A. , Pepin Pierre
Published: April 2008

We report on an 18-month field study of temporal pattern and interrelationships of size- and age-at-recruitment (to fresh waters) for two diadromous hill-stream gobies in Dominica, West Indies (15°30′N, 61°25′W). Recruitment is panseasonal in Sicydium punctatum and Sicydium antillarum and supports a directed fishery similar to other goby fry fisheries. We found both size and age of recruits to vary seasonally, but the relationship of size to age is complex. Although positively related within lunar-monthly recruiting cohorts, the overall relationship of size and age was poor because seasonal variation in size is out of phase with age. Among recruiting cohorts, mean (or predicted) size and age are negatively correlated. Recruitment (fishery yield) also varies seasonally, in phase with size and out of phase with age. Peak fishery yields coincide with the youngest, but largest, recruits; low yields coincide with the reverse, implicating growth rate variations in fishery yield. This is the first such report of systematic seasonal variation in age-at-recruitment. Given these findings, size- and age-at-recruitment (here similar to settlement or metamorphosis) should not be assumed invariant, even for tropical fishes.
Effect of lake-wide planktivory by the pelagic prey fish community in Lakes Michigan and Ontario
Authors: Rand Peter S. , Stewart Donald J. , Lantry Brian F. , Rudstam Lars G. , Johannsson Ora E. , Goyke Andrew P. , Brandt Stephen B. , O'Gorman Robert , Eck Gary W.
Published: April 2008

We compared predatory demand by pelagic planktivorous prey fish with invertebrate production in Lake Michigan during 1987 and in Lake Ontario during 1990. Predation by the planktivores in Lake Ontario was nearly fourfold higher than in Lake Michigan (approx. 87 g wet weight∙m−2∙year−1). Predation rates on Mysis were comparable in Lakes Michigan and Ontario (approx. 21 g∙m−2∙year−1), while predation on Diporeia was markedly higher in Lake Michigan than in Lake Ontario (21.3 vs. 8.5 g wet weight∙m−2∙year−1). In Lake Ontario, predatory demand on zooplankton exceeded our best estimate of production by a factor of 1.7. Similarly, predation estimates on Mysis in Lake Ontario were 1.2–2.0 times the estimated rate of production, depending on the production model used. Lake Michigan planktivores consumed approximately 55% of available zooplankton production in 1987, indicating that competition for prey resources, if operating, was not as intense as that in Lake Ontario in 1990. It is unclear how to resolve the paradox that predation could markedly exceed available prey production in some cases. There could be sources of error in the estimates of both the supply and demand sides of these trophic relationships.
A spatially explicit bioenergetics measure of habitat quality for adult salmonines: Comparison between Lakes Michigan and Ontario
Authors: Mason Doran M. , Goyke Andrew , Brandt Stephen B.
Published: April 2008

We used spatially explicit modeling to compare habitat quality for chinook salmon, Oncorhynchus tshawytscha, and lake trout, Salvelinus namaycush, in Lakes Michigan and Ontario. This grid-based approach predicts a predator's physiological growth response, growth rate potential, from measured physical and biological environmental conditions and is a species-specific measure of habitat quality. Underwater acoustics was used to map prey spatial distributions, abundances, and sizes. A foraging model defined predator consumption rates from prey data. A bioenergetics model calculated growth rate potential based on consumption rates and prevailing thermal conditions. We compared habitat quality between lakes using both the mean growth rate potential and the volume (or proportion) of water capable of supporting positive growth rates. Mean growth rate potential for both chinook salmon and lake trout was similar between the lakes despite known differenes in the prey species composition and abundance. However, Lake Michigan provided a greater volume of water capable of supporting growth for both chinook salmon (26%) and lake trout (21%) compared with that for Lake Ontario (19% for both species). Our measure of habitat quality based on species-specific physiological requirements should provide a tool to compare ecosystems and quantify ecosystem change.
Characterization and mapping of a male-sterility mutant, tapetum desquamation (t), in rice
Authors: Zhang Yi , Mao Jin-Xiong , Yang Kun , Li Yun-Feng , Zhang Jian , Huang Yuan-Xin , Shen Fu-Cheng , Zhang Chao-Di
Published: April 2008

A spontaneously mutated male-sterile material was found among the offspring of the indica restorer line Jinhuiyihao. To understand the status and function of the related gene and clone the gene, a near-isogenic line (NIL) of the male sterility was bred, and characterization of the mutant and gene mapping were performed. The results indicated that there are obvious differences between the male-sterile NIL and the indica maintainer line II-32B. The anther size of the NIL is smaller than that of II-32B, and the anther color is white in the NIL but yellow in II-32B. No pollen from the matured anther in the NIL was observed to be stained using KI–I2 solution. In transverse sections of the sterile anther, at early microspore stage the cytoplasm of the tapetum concentrates but the tapetum itself does not degenerate after microspores are released from the tetrads; the tapetum then desquamates from the anther wall and enwraps microspores; subsequently, the surrounded microspores collapse completely at late microspore and early bicellular pollen stages. Inheritance analysis showed that the male sterility was controlled by a single recessive gene, ostd (t). This gene was mapped between the SSR markers RM7434 and RM275 on chromosome 6, and the physical distance from RM7434 to RM275 is about 389 kb.
Microsatellite accumulation on the Y chromosome inSilene latifolia
Authors: Kubat Zdenek , Hobza Roman , Vyskot Boris , Kejnovsky Eduard
Published: April 2008

The dioecious plant Silene latifolia possesses evolutionarily young sex chromosomes, and so serves as a model system to study the early stages of sex chromosome evolution. Sex chromosomes often differ distinctly from autosomes in both their structure and their patterns of evolution. The S. latifolia Y chromosome is particularly unique owing to its large size, which contrasts with the size of smaller, degenerate mammalian Y chromosomes. It is thought that the suppression of recombination on the S. latifolia Y chromosome could have resulted in the accumulation of repetitive sequences that account for its large size. Here we used fluorescence in situ hybridization (FISH) to study the chromosomal distribution of various microsatellites in S. latifolia including all possible mono-, di-, and tri-nucleotides. Our results demonstrate that a majority of microsatellites are accumulated on the q arm of the Y chromosome, which stopped recombining relatively recently and has had less time to accumulate repetitive DNA sequences compared with the p arm. Based on these results we can speculate that microsatellites have accumulated in regions that predate the genome expansion, supporting the view that the accumulation of repetitive DNA sequences occurred prior to, not because of, the degeneration of genes.
Chemistry and ectomycorrhizal communities of coarse wood in young and old-growth forests in the Cascade Range of Oregon
Authors: Elliott J. C. , Smith J. E. , Cromack K. , Chen H. , McKay D.
Published: April 2008

Coarse wood provides important ecosystem structure and function such as water and nutrient storage and critical habitat for the conservation of a variety of organisms, including ectomycorrhizal (EM) fungi. The chemistry and EM communities were compared in coarse wood samples collected from two advanced decay stages of logs in 12 paired young and old-growth stands in the Oregon Cascade Range. Average total C and nonpolar extractives were higher in young stands (15–55 years) (mean = 53.38%, 95% CI of 52.48–54.27 and mean = 8.54%, 95% CI of 6.92–10.16, respectively) compared with old-growth stands (200–500 years) (mean = 51.22%, 95% CI of 49.67–52.77 and mean = 6.75%, 95% CI of 5.88–7.62, respectively). Averages for total and extractable P were higher in old-growth stands (mean = 0.03%, 95% CI of 0.02–0.04 and mean = 82.91, 95% CI of 52.24–113.57, respectively) compared with young stands (mean = 0.02%, 95% CI of 0.02–0.02 and mean = 56.17, 95% CI of 45.84–66.50, respectively). Average pH and total N were highest in logs in the most advanced decay stage (mean = 4.17, 95% CI of 3.97–4.38 and mean = 0.35%, 95% CI of 0.29–0.40, respectively). No differences between log decay class or stand age were detected for water-soluble extractives, hemicellulose plus cellulose (or acid-hydrolyzable fraction), or acid-unhydrolyzable residue. Observed differences in average wood property values between decay stages and between young and old-growth stands were small and, although statistically significant, may not reflect an important difference in EM fungal habitat. EM communities were similar between young and old-growth stands and between logs in decay classes 4 and 5. Results suggest that down wood in advanced decay stages provides similar habitat for EM fungi in both old-growth and young, managed stands.
Breeding for improved growth and juvenile corewood stiffness in slash pine
Authors: Li Xiaobo , Huber Dudley A. , Powell Gregory L. , White Timothy L. , Peter Gary F.
Published: April 2008

The importance of integrating measures of juvenile corewood mechanical properties, modulus of elasticity in particular, with growth and disease resistance in tree improvement programs has increased. We investigated the utility of in-tree velocity stiffness measurements to estimate the genetic control of corewood stiffness and to select for trees with superior growth and stiffness in a progeny trial of 139 families of slash pine, Pinus elliottii Engelm. grown on six sites. Narrow-sense heritability estimates across all six sites for in-tree acoustic velocity stiffness at 8 years (0.42) were higher than observed for height (0.36) and diameter at breast height (DBH) (0.28) at 5 years. The overall type B genetic correlation across sites for velocity stiffness was 0.68, comparable to those found for DBH and volume growth, indicating that family rankings were moderately repeatable across all sites for these traits. No significant genetic correlations were observed between velocity stiffness, DBH, and volume growth. In contrast, a significant, but small, favorable genetic correlation was found between height and velocity stiffness. Twenty percent of the families had positive breeding values for both velocity stiffness and growth. The low cost, high heritability and nearly independent segregation of the genes involved with in-tree velocity stiffness and growth traits indicate that acoustic methods can be integrated into tree improvement programs to breed for improved corewood stiffness along with growth in slash pine.
A novel rapid sampling method for pinewood nematode, Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae)
Authors: Zhao Lilin , Wei Wei , Liu Xinzhong , Kang Le , Sun Jianghua
Published: April 2008

The pinewood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, is listed as a quarantine pest in the legislation of more than 40 countries. Rapid and accurate detection of the pinewood nematode in coniferous chips, sawn wood, and logs is critical in preventing the introduction of the nematode and forms the basis for quarantine regulations. The traditional but laborious Baermann-funnel sampling technique delays the detection of pinewood nematode. We applied the chemotactic response of pinewood nematode to its insect vector, Monochamus alternatus Hope, to develop a novel and rapid sampling method. A trap tube, baited with a blend of attractant terpenes (α-pinene, β-pinene, and longifolene, 1:2.7:1.1) is shown to effectively capture third-stage dispersal juveniles of pinewood nematode from infested wood under laboratory and field conditions. Nematodes were first isolated after a 2 h trapping period, and the number of nematodes recovered increased with the duration of trapping. This chemical attraction technique is simple, effective, and rapid and should assist greatly in the detection of pinewood nematode at both ports-of-entry and forest habitats.