bluuebunny/crossref_metadata_2025 huggingface dataset:
Biomass of Freshwater Crustacean Zooplankton from Length–Weight Regressions
Authors: Culver David A. , Boucherle Mary M. , Bean David J. , Fletcher James W.
Published: November 2008

We present equations for calculating dry weight from body length for 14 common and widely distributed taxa of crustacean zooplankters; these were generated by regression from weights of individuals chosen from the range of lengths observed for each taxon, usually three replicate weights at each of five lengths. We include regressions for ovigerous and nonovigerous cladocerans, plus nauplii, early copepodites, and adult males and females for the copepods (30 length–weight relationships) and individual weights for given stages of copepods. We calculated the seasonal variation in crustacean biomass for a station in the Bay of Quinte, Lake Ontario, and for each of the three basins of Lake Erie. Biomass was dominated by Cladocera for both lakes, with Copepoda predominant in the spring. Mean individual dry weights varied seasonally for all taxa, confirming previous findings.
Changes in Territorial, Gill-flaring, and Feeding Behavior in Juvenile Coho Salmon (Oncorhynchus kisutch) following Short-term Pulses of Suspended Sediment
Authors: Berg L. , Northcote T. G.
Published: November 2008

The territorial, gill-flaring, and feeding behavior of juvenile coho salmon (Oncorhynchus kisutch) in a laboratory stream was disrupted by short-term exposure to suspended sediment pulses. At the higher turbidities tested (30 and 60 nephelometric turbidity units (NTU)), dominance hierarchies broke down, territories were not defended, and gill flaring occurred more frequently. Only after return to lower turbidities (0–20 NTU) was social organization reestablished. The reaction distance of the fish to adult brine shrimp decreased significantly in turbid water (30 and 60 NTU) as did capture success per strike and the percentage of prey ingested. Implications of these behavioral modifications suggest that the fitness of salmonid populations exposed to short-term pulses of suspended sediment may be impaired.
Catch-Per-Unit-Effort: A Statistical Model for Pacific Halibut (Hippoglossus stenolepis)
Authors: Quinn II Terrance J.
Published: November 2008

The empirical distributions of catch-per-unit-effort (CPUE) of Pacific halibut (Hippoglossus stenolepis) were positively skewed and could be modeled by a general family of distributions involving power transformations. The root normal distribution, a special case from the family, was found to be a convenient model for the data. Measures of the central tendency and variance of the distribution were derived. Estimators of the central tendency based on increasing variance of a function of catch as a function of effort were most appropriate for the data. A median-based estimator performed better than a mean-based estimator. Thus, statistical modeling of CPUE provided a tool for constructing a better estimator of an abundance index.
Limitations of Using Otoliths Recovered in Scats to Estimate Prey Consumption in Seals
Authors: Silva Jack da , Neilson John D.
Published: November 2008

Of three length classes of herring, Clupea harengus (30–35, 20–25, and [Formula: see text] total length), fed to a captive harbor seal, Phoca vitulina, otoliths were recovered only from herring 30–35 cm long; of these otoliths only 4% were recovered. Using surface area to volume ratios of otoliths, other fish species were predicted to be similarly underrepresented in scats. After digestion, otoliths showed fewer annuli and a reduction in length and width. Herring otoliths in harbor seal scats indicated the consumption of large herring ([Formula: see text] total length) only and could not be used to estimate numbers of prey consumed. The partial digestion of herring otoliths will result in underestimates of fish age, length, and weight if calculations are based on standard relationships between these parameters and measurements from undigested otoliths.
Moulting and Mating of Snow Crabs, Chionoecetes opilio (O. Fabricius), in Shallow Waters of the Northwestern Gulf of Saint Lawrence
Authors: Sainte-Marie Bernard , Hazel François
Published: November 2008

Chionoecetes opilio in baie Sainte-Marguerite, Gulf of Saint Lawrence, were sampled by beam trawl in spring from 1988 to 1991 and by divers in March 1991 to document an hypothesized annual moult in shallow waters. Each spring, C. opilio occurred at 4–20 m of depth where 29.3–97.3% of males and 20.3–81.4% of females were moulting or recently moulted. Males and females [Formula: see text] carapace width (CW) moulted only on bottoms < 60 m. Females were mature at [Formula: see text] CW and males were morphometrically mature at [Formula: see text] CW. Overall, 0.3% of morphometrically mature (N = 575) and 23% of morphometrically immature (N = 826) males [Formula: see text] CW, exclusive of soft-shelled, had a visible second carapace. These and other data support the hypothesis of a terminal moult coincident with morphometric maturity. Pubescent females mated with males 59.9–109.3 mm CW (88% were < 95 mm CW), 97% of which were morphometrically mature (N = 120). Mean size of these males was greater than that of males grasping immature females or other males, indicating male competition for pubescent females. Morphometrically mature males were larger on bottoms > 80 m deep, where multiparous females concentrated, than on shallower bottoms.
Decision Analysis of a Large-Scale Fishing Experiment Designed to Test for a Genetic Effect of Size-Selective Fishing on British Columbia Pink Salmon (Oncorhynchus gorbuscha)
Authors: McAllister Murdoch K. , Peterman Randall M.
Published: November 2008

Past work suggested that size-selective harvesting of large fish combined with heritability of body size has caused the large (up to 34%) decrease in mean adult weight of British Columbia pink salmon (Oncorhynchus gorbuscha) since 1950. In a companion paper (Can. J. Fish. Aquat. Sei. 49: 1294–1304) we evaluated the statistical performance of a large-scale fishing experiment that could enable managers to test this hypothesis and at the same time increase catch biomass if that hypothesis were correct. In this paper we evaluate the economic performance of the proposed experiment using Monte Carlo simulation and decision analysis under a wide range of conditions that encompasses existing biological uncertainties. We accounted for uncertainties through prior probabilities placed on two key biological hypotheses. We computed the expected economic value of catch biomass for the experimental and current nonexperimental (status quo) management strategies using a 20-yr time horizon and a 10-yr experiment with four spatial replicates. Under a variety of discount rates, the expected economic value of experimentation exceeded that of status quo management in most of the conditions examined, in some cases by as much as 60%.
Statistical Models for Estimating CPUE from Catch and Effort Data
Authors: Richards Laura J. , Schnute Jon T.
Published: November 2008

Catch-per-unit-effort (CPUE) provides one of the most commonly used abundance indices in fishery research. The literature, however, offers no unique method of estimating CPUE and its variance from catch and effort data. In this paper we develop two models (univariate and bivariate) that generalize previous approaches and remain valid under management restrictions on catch and/or effort. Both models estimate CPUE from measures of central tendency in the underlying catch and effort distributions. The models involve normalizing transformation parameters that, along with other parameters, are estimated by maximum likelihood. We illustrate the models using data from Pacific ocean perch (Sebastes alutus). For the four data sets examined, the univariate and bivariate models result in similar estimates of CPUE. However, other commonly used CPUE measures lead to inconsistent results, in particular for data sets in which catch was restricted by low trip limits. We recommend the bivariate model, since it accounts for the bivariate structure of catch and effort data. Furthermore, it can easily be adapted to accommodate alternative indices, for example, the effort required to attain a specified catch.
Radioisotope Method for Estimating Food Consumption by Brown Trout (Salmo trutta)
Authors: Forseth Torbjørn , Jonsson Bror , Næumann Roger , Ugedal Ola
Published: November 2008

A fast, simple, and reliable method for estimating food consumption using radioisotopes is presented. The method gives both sensitive short-term and robust long-term estimates of food consumption for brown trout (Salmo trutta). The estimates of daily food rations were similar to those estimated from rates of gastric evacuation and laboratory experiments. The radioisotope method can be used to detect variations in ration size due to temperature, fish size, and food availability. Information on radiocesium absorption from this study and earlier published data on radiocesium retention can be used to estimate daily ration for both piscivorous and benthivorous brown trout. The radioisotope method can be used in radiocesium-contaminated lakes, but it could also be used in other experimental situations by adding stable cesium to small water bodies. The same method is also applicable for use with other stable or radioactive isotopes.
Effects of Sounds from a Geophysical Survey Device on Behavior of Captive Rockfish (Sebastes spp.)
Authors: Pearson Walter H. , Skalski John R. , Malme Charles I.
Published: November 2008

Behavior of rockfish (Sebastes spp.) exposed to air-gun sounds was examined to establish parameters in a subsequent fishing experiment to determine the effects of a geophysical survey device on fishing success. Rockfish observed in a field enclosure showed startle and alarm responses during 10-min exposures to sounds from a single 1639-cm3 air gun. For olive and black rockfish (S. serranoides and S. melanops), the threshold for the startle responses lay between 200 and 205 dB re 1 μPa. Under sound presentation, blue rockfish (S. mystinus) milled in increasingly tighter mills, and schools of black rockfish collapsed to the bottom. Vermilion (S. miniatus) and olive rockfish formed stationary schools near the bottom and, on sound presentation, either rose in the water column or moved to the bottom and became almost motionless. The general threshold for the alarm responses was about 180 dB re 1 μPa. Regression analyses of changes in depth distribution and shifts to active behaviors suggested that more subtle behavioral responses to sounds might become evident at 161 dB re 1 μPa. These initial responses were sustained only for a few minutes and may differ from those of unconfined fish.
Spatial Analysis of Bering Sea Groundfish Survey Data Using Generalized Additive Models
Authors: Swartzman Gordon , Huang Chisheng , Kaluzny Stephen
Published: November 2008

Generalized additive models (GAM) are herein applied to trawl survey data in the eastern Bering Sea with an eye to (1) detecting trends in groundfish distributions and (2) improving abundance estimates by including the trend. GAM is a statistical method, analogous to regression, but without the assumptions of normality or linearity that relate a response variable (in this case, fish abundance) to location (latitude and longitude) and associated environmental variables (e.g. depth and bottom temperature). GAM provided reasonable (i.e. high r2) fits to the spatial distribution of five flatfish species and was able to define a spatial "signature" for each species, namely their preferred depth and temperature range. GAM also gave lower average abundance and abundance variability estimates for these five flatfish species than the stratified sampling procedure previously employed.
Application of Diel Feeding Chronology to Habitat Suitability Analysis of Warmwater Stream Fishes
Authors: Kwak Thomas J. , Wiley Michael J. , Osborne Lewis L. , Larimore R. Weldon
Published: November 2008

Diel feeding chronology and daily ration were determined from stomach or foregut contents of common carp (Cyprinus carpio), golden redhorse (Moxostoma erythrurum), channel catfish (Ictalurus punctatus), smallmouth bass (Micropterus dolomieu), and longear sunfish (Lepomis megalotis) in the Vermilion River, Illinois. Feeding was highly variable among individuals, hours, and months for each species. Discontinuous feeding was detected in common carp, golden redhorse, and channel catfish. Common carp and the two centrarchid species fed with greatest intensity near sunrise and sunset; golden redhorse and channel catfish feeding was highest at night. Daily ration estimates were higher for fishes with stomachs than those for stomachless species. Microhabitats occupied by fish over the diel period were identified using nondisruptive techniques: direct observation, prepositioned electrofishing, and radiotelemetry. Microhabitat use during high-feeding periods was significantly different [Formula: see text] than that during low feeding for at least one habitat variable in each species examined. Association with cover also varied between feeding regimes. Our findings suggest that realism of instream flow assessments may be improved if habitat suitability criteria are stratified by feeding regime.
Profundal Sediment Organic Content and Physical Character Do Not Reflect Lake Trophic Status, but Rather Reflect Inorganic Sedimentation and Exposure
Authors: Rowan D. J. , Kalff J. , Rasmussen J. B.
Published: November 2008

An analysis of profundal sediment data from 83 north-temperate lakes shows that increasing inorganic sedimentation and exposure (or lake surface area) results in lower organic content and water content, and greater bulk density. Because sedimentation rates are unavailable for most lakes, we estimate sedimentation rates from readily available catchment sediment loads using a mass-balance model. The mass-balance estimate of sediment retention (per square metre of depositional zone) is an excellent predictor of measured inorganic sedimentation rates for a data set covering 19 lakes (R2 = 0.92). Multiple regressions are used to predict organic content, water content, and bulk density of profundal sediment from inorganic sedimentation rates and either exposure or lake surface area, which are surrogates for the energy of the depositional environment. These analyses explain 76, 74, and 66% of the between-lake variation in the three sediment parameters, respectively. Sediment organic content is not related to lake trophic status (chlorophyll a) and is negatively correlated with net organic matter sedimentation rates. The common occurrence of organic-rich sediments in oligotrophic shield lakes is, therefore, not a reflection of high organic matter inputs, but rather the extremely low inputs of mineral sediments to these lakes.
Comparison of Otolith-Based Back-Calculation Methods to Determine Individual Growth Histories of Larval Striped Bass, Morone saxatilis
Authors: Secor David H. , Dean John Mark
Published: November 2008

In rearing studies on 6- to 22-d-old larval striped bass, Morone saxatilis, we applied several back-calculation methods to known-growth larvae. A growth effect occurred on otolith diameter – standard length relationships, where slower growing larvae had relatively larger otoliths. Otolith growth was less affected by feeding regime than was somatic growth. Due to the conservative nature of otolith growth, proportional based (Biological Intercept Method) and simple linear regression methods linearized somatic growth transitions and did not estimate periods of negative growth. A quadratic regression method which used age as an additional predictor resulted in the accurate back-calculation of size at age in all groups of laboratory-reared larvae. However, when model coefficients were applied to a test population of pond-reared larvae, the quadratic model performed poorly. While differences in relative otolith size between pond- and laboratory-reared larvae could be ascribed to a temperature effect, the inability to apply the model also indicates a problem specific to regression-based methods. Theoretical rationale and experimental proof provided evidence for the inclusion of age in back-calculation models, but parameterization will have to occur for each field application.
Grazing by Zooplankton and Its Relationship to Community Structure
Authors: Cyr Hélène , Pace Michael L.
Published: November 2008

Zooplankton can consume a substantial portion of the phytoplankton, but grazing rates are notoriously variable seasonally and among sites. We developed models relating grazing rates to characteristics of Zooplankton communities, food concentration, and water temperature. Grazing rates were measured in 30 Zooplankton communities that differed in biomass, size distribution, and taxonomic composition. Crustaceans grazed per day 2–21% of the chlorophyll in algae <35 μm, which is within the range of most grazing rates measured in other studies. Grazing rates were positively related to Zooplankton biomass and negatively related to food concentration, although much variation among communities remains unexplained (R2 = 0.19–0.35). Surprisingly, we could not detect a general relationship between Zooplankton size distribution and grazing rate. Communities dominated by large Zooplankton (mostly Daphnia and Diaphanosoma) did not tend to have higher grazing rates than communities dominated by small Zooplankton. Zooplankton taxonomic composition was significantly related to grazing rates but explained little variation among communities. Grazing rates calculated from published allometric equations were biased, usually overestimating phytoplankton removal by Zooplankton.
Planktivores and Plankton Dynamics: Effects of Fish Biomass and Planktivore Type
Authors: Lazzaro Xavier , Drenner Ray W. , Stein Roy A. , Smith J. Durward
Published: November 2008

We quantified the effects of planktivore biomass and planktivore type in an experimental mesocosm study of factorial design in which five levels of fish biomass (0–75 g/m3) were cross-classified with two plantivore types: filter-feeding gizzard shad (Dorosoma cepedianum) and visual-feeding bluegill (Lepomis macrochims). As fish biomass increased, cladocerans, cyclopoids, particulate phosphorus (PP) > 200 μm, and chironomids declined; conversely, rotifers, primary productivity, chlorophyll a, turbidity, unicellular flagellates, colonial and unicellular green algae, pennate diatoms, total phosphorus, and 20–200 and 12–20 μm PP were enhanced. In the presence of gizzard shad, as compared with bluegill, cyclopoids, turbidity, unicellular green algae, pennate diatoms, > 200 μm PP, and chironomid tubes were higher whereas colonial green algae and < 0.2 μm PP were lower. Fish biomass operated independently of planktivore type for most variables, except copepods, colonial green algae, turbidity, and 20–200 μm PP. Although gizzard shad and bluegill have different trophic cascade pathways, fish biomass was more important than planktivore type as a regulator of plankton communities and water quality.
Revised Estimates of Age and Growth of the Sandbar Shark (Carcharhinus plumbeus) from the Western North Atlantic
Authors: Casey John G. , Natanson Lisa J.
Published: November 2008

Age and growth of the sandbar shark (Carcharhinus plumbeus) were determined from tag and recapture data covering a 26-yr period (1964–90). Results were compared with previously published age and growth estimates based primarily on rings in vertebrae. Recent long-term tag returns suggest that the sandbar shark grows much slower than previously proposed and may take nearly 30 yr to reach maturity. Revised von Bertalanffy parameters (sexes combined) are L∞ = 186, k = 0.046, and t0 = −6.45. The limitations of ageing elasmobranchs solely from rings in vertebrae and the need for validating rings in hardparts of fishes are discussed.
Behaviour, Habitat Use, and Movements of Coho Salmon (Oncorhynchus kisutch) Smolte during Seaward Migration
Authors: McMahon Thomas E. , Holtby L. Blair
Published: November 2008

Coho salmon (Oncorhynchus kisutch) smolts formed aggregations in pools with large woody debris during their migration downstream and into the Carnation Creek estuary, British Columbia. Smolts utilized the estuary throughout the smolt run, with periods of high outmigration coinciding with spring tides which brought warmer, more saline water into the estuary. Smolt abundance in the stream and estuary was positively related to debris volume, and 82% of the 1260 smolts observed during underwater counts occurred within 1 m of debris. Debris volume and smolt density were significantly lower in clearcut than in buffered stream sections. Our observations support the need to retain and manage large woody debris for smolt habitat in streams and estuaries.
Spatial and Temporal Overlap of the American Lobster (Homarus americanus) and Sea Scallop (Placopecten magellanicus) as Related to the impact of Inshore Scallop Dragging
Authors: Roddick D. L. , Miller R. J.
Published: November 2008

Assessment of the damage of one fishery by another requires knowledge of the overlap, in time and space, of the damaging fishing effort and the abundance of the damaged species, as well as a measure of the rate of damage. This approach was used to measure the impact of inshore scallop dragging on lobsters in Nova Scotia. Areas of reported co-occurrence of lobster and scallop grounds were surveyed by divers to determine the extent of overlap. Only 2 of 52 sites surveyed had lobsters on scallop grounds that could be dragged. Divers surveyed one site six times during 1987 and 1988 and found lobsters most abundant during August and September. Only 2% of the lobsters in the path of scallop drags were either captured or injured. The estimated value of lobsters destroyed by dragging for scallops during periods of peak lobster abundance was minor: $757 at one site and $176 at the other. Restricting dragging to periods of low lobster abundance significantly reduces this cost.
Transport and Burial as a Cause of Whitefish (Coregonus sp.) Egg Mortality in a Eutrophic Lake
Authors: Ventling-Schwank Andrea R. , Livingstone David M.
Published: November 2008

Predictions based on the Shields diagram and confirmed by experiments conducted in eutrophic Lake Sempach imply that bottom currents associated with winter storm events are responsible for the simultaneous transport of coregonid eggs and fine silt and clay (grain size [Formula: see text]) from the spawning grounds into deeper lake regions. The critical shear stress required to initiate egg transport is estimated to lie in the range 0.02–0.04 N∙m−2, corresponding to mean current speeds of 10–15 cm∙s−1 at a reference height of 0.5 m above the sediment surface. On settling out, egg burial is likely. This will increase egg mortality not only by physically hindering oxygen transport to the egg, but also, in POC-rich eutrophic lake sediment, by relocating the egg in a zone of steep oxygen gradients and low mean oxygen concentrations. Microelectrode measurements and computation of the thickness of the oxygen diffusive boundary layer over the sediment reveal that even eggs that escape interment are likely to be subjected to ambient oxygen concentrations insufficient for development to hatching. It is suggested that transport and burial may in general be important factors determining coregonid egg mortality in eutrophic lakes.
Seasonal Changes in the Total Lipid Content of the Opossum Shrimp, Mysis relicta (Malacostraca: Mysidacea)
Authors: Adare Katherine I. , Lasenby David C.
Published: November 2008

Seasonal changes in the percent total lipid content of Mysis relicta were investigated in four lakes in southern Ontario. Stony and Twelve Mile lakes contain populations of Mysis with a 1-yr life cycle, while Crystal and Boshkung lakes have populations with a 2-yr life cycle. Mature female and male mysids have a lipid content between 15 and 33% and between 14 and 25%, respectively, while juvenile mysids have approximately 10% less total lipids than adults. The relationship between total lipid and lipid-free dry weight is best described by the power curve Y = aXb and is the same (ANCOVA, p < 0.05) in all four mysid populations. Lipid content accumulates steadily with time as the mysid grows, and lipid reserves do not appear to influence mysid time to maturity. For studies on the transfer of energy and lipophilic organic contaminants through the food web, the results imply that seasonal and body size differences of organisms are important considerations.
Otolith Elemental Fingerprinting for Stock Identification of Atlantic Cod (Gadus morhua) Using Laser Ablation ICPMS
Authors: Campana Steven E. , Fowler Anthony J. , Jones Cynthia M.
Published: November 2008

Trace element incorporation into fish otoliths varies among samples collected at different sites. If otolith elemental composition (the elemental "fingerprint") somehow reflects the characteristics of the ambient water, the elemental fingerprint of the otolith nucleus could serve as a natural marker of fish hatched at different sites. To test this hypothesis, Atlantic cod (Gadus morhua) otoliths collected from five spawning grounds in the northwest Atlantic were tested for differences in elemental and isotopic composition. Laser ablation – inductively coupled plasma mass spectroscopy (LA-ICPMS) was used to assay the concentration of 14 isotopes (nine elements) in otolith nuclei. The sensitivity of the laser ablation system exceeded that of the electron microprobe by 2–4 orders of magnitude, with an average CV of 21% for any given isotope. Most isotopic concentrations were consistent between left and right otoliths of a given fish, and most differed significantly among sample sites; there were no significant differences by age, sex, or fish length. Multivariate analyses of the elemental fingerprints resulted in significant discrimination among sample sites. While the mechanism underlying trace element incorporation into otoliths is still unclear, otolith elemental fingerprinting has the potential to become an effective and accurate means of stock identification.
Sediment–Water Distribution Coefficients and Speciation of Cadmium in a Canadian Shield Lake
Authors: Wagemann R. , Capel M. J. , Hesslein R. , Stephenson M.
Published: November 2008

Sediment–water distribution coefficients for Cd were strongly pH dependent at pH > 6.5 for three surficial bottom sediments and suspended particles from a Canadian Shield lake (Lake 382). A single exponential equation in terms of pH fitted the distribution coefficients of all sediments. In the range 6.5 ≤ pH ≤ 8 the distribution coefficients were 109 × 10−3 to 1579 × 10−3 L/mg for suspended particulate matter and 0.6 × 10−3 to 129 × 10−3 L/mg for the bottom sediments. Speciation calculations performed using the computer program MACS80 and measured Cd fractions associated with suspended particles agreed well down to 7 m. In deeper water the measured fraction exceeded the calculated fraction, hypothetically because of CdS formation, differing sediment compositions, or nonequilibrium conditions. In September, H2S was 100–300 μg/L in the lower hypolimnion. Even at only 5 μg dissolved sulfide/L, some of the added Cd would precipitate as CdS at pH > 6, and the dissolved Cd, under anoxic conditions, would be largely Cd(HS)+ and Cd(HS)2. Under aerobic conditions at pH ≥ 7.5, approximately 85% of the Cd was on suspended particles and complexed with dissolved organic matter. The solids Cd(OH)2, CdCO3, and Cd3(PO4)2 played no role in the control of dissolved Cd.
Changes in Serum Free Thyroxine, Prolactin, and Olfactory Activity during Induced Smoltification in Atlantic Salmon (Salmo salar)
Authors: Morin Pierre-Philippe , Andersen Øivind , Haug Egil , Døving Kjell B.
Published: November 2008

Serum levels of free thyroxine (FT4) and prolactin (PRL) and olfactory activity were studied in juvenile Atlantic salmon (Salmo salar) induced to undergo premature smoltification by a regime of increasing temperature and photoperiod. The olfactory epithelium was stimulated with L-alanine or taurocholate (10−8–10−4 M) while electroencephalographic responses were recorded from the rostrolateral and rostromedial surfaces of the olfactory bulb. Two peaks of olfactory activity occurred during the 8-wk test period for three combinations of recording site and odorant, lateral–alanine, lateral–taurocholate, and medial–taurocholate, but not for the medial–alanine combination. The first peak occurred at the beginning of smoltification (the "acute phase") coinciding with the previously described sensitive period for olfactory imprinting. Whereas this peak of olfactory activity was not associated with a rise in serum FT4, the second peak, occurring after the acute phase of smoltification, coincided with a FT4 peak. PRL remained constant throughout the acute phase of smoltification but increased 1 wk after the second peak of olfactory activity. It is concluded that olfactory activity is at least partly related to thyroid activity during induced smoltification.
Size-related Change in the Visual Resolution of Sunfish (Lepomis spp.)
Authors: Walton William E. , Easter Jr. Stephen S. , Malinoski Celeste , Hairston Jr. Nelson G.
Published: November 2008

Visual resolution of juvenile sunfish (Lepomis spp.) (8–33 mm standard length (SL)), although extremely poor in comparison with the larger individuals (38–160 mm SL) used in previous studies, improves rapidly as they grow. Histologically and behaviorally determined (mean reaction angle) visual angles of fish between 10 and 33 mm SL decrease by approximately 50 and 100 minutes of arc, respectively, and decline non-linearly with increasing fish size. Behaviorally determined visual resolution of juvenile sunfish based on maximum location distance (MLD) is equivalent to that calculated from intercone spacing. The mean reaction angle used in previous studies may have underestimated behavioral visual resolution of larger (> 38 mm SL) sunfish by approximately 30%. Visual volume and search volume increase by nearly three orders of magnitude in sunfish between 8 and 50 mm SL. After sunfish exceed 50 mm SL (when they can safely return to the pelagic zone), visual resolution increases comparatively slowly as body size increases. Our results suggest that the size-related change in behavioral visual resolution in sunfish is influenced by other factors in addition to the growth-related changes in the resolving power of the retina.
Effects of Movement on Stock Assessment in a Restricted-Range Fishery
Authors: Mullen Ashley J.
Published: November 2008

A simple spatial model is proposed for yellowfin tuna (Thunnus albacores) in the eastern Pacific Ocean for the period prior to the late 1960's, when the fishery was confined to a relatively narrow coastal belt and a few offshore islands and banks. Yellowfin are highly mobile, but they exhibit little or no tendency towards directed movement; their movement can be characterized as highly diffusive. The effect of the fishery extends far beyond the range of the fleet. Within this context the concept of a "stock" is not well defined. Diffusive transport distorts the equilibrium yield – effort curve: an asymmetry is imparted to the Schaefer model. It appears that the catches of the coastal fishery were largely sustained by immigration from the larger offshore region, which constituted a refuge. If the cost of effort is considered as a function of distance from shore, then the expansion of the fishery might be attributed to a change in that function. Costs change with improved technology, and innovation may have been spurred by regulations that were imposed to conserve yellowfin in the eastern Pacific Ocean.
A Test of Hypotheses to Explain the Sigmoidal Relationship between Total Phosphorus and ChlorophyllaConcentrations in Canadian Lakes
Authors: Chow-Fraser P. , Trew D. O. , Findlay D. , Stainton M.
Published: November 2008

We tested five hypotheses to explain the sigmoidal relationship between total phosphorus (TP) and chlorophyll a (Chl a), two assuming that the nonlinearity is an artifact of various measurement biases and three assuming that it is based on underlying ecological interactions. Our first hypothesis was rejected; accounting for differences in extraction protocol of Chl a among published studies did not affect the sigmoidality. Our second hypothesis could not be rejected; there was an uncoupling between Chl a and PHYTO in oligotrophic lakes which may explain the initial nonlinearity. Our third hypothesis was upheld; the initial nonlinearity may be attributed to the presence of a disproportionately large fraction of unavailable phosphorus, since Chl a varied linearly with the proportion of total biologically active phosphorus in the TP fraction. The proportion of filamentous cyanophytes varied significantly with TP concentrations, and this was consistent with our fourth hypothesis that the higher Chl a:TP ratio at intermediate TP concentrations is attributable to reduced grazing impact of zooplankton in more productive lakes. Finally, Chl a varied linearly with total nitrogen, and this was consistent with our fifth hypothesis that the departure from linearity at extremely high phosphorus concentrations is indicative of nitrogen limitation.
Feeding Ecology of Walleye, Stizostedion vitreum, Larvae: Effects of Body Size, Zooplankton Abundance, and Zooplankton Community Composition
Authors: Johnston Thomas A. , Mathias J. A.
Published: November 2008

We conducted laboratory experiments to examine the functional response and conducted comparative laboratory and field studies to examine the prey selection of walleye, Stizostedion vitreum, larvae. Maximum consumption rate (Cmax, micrograms per hour) increased exponentially with walleye mean length whereas the prey abundance at which 90% of Cmax is attained (D90, prey per litre) increased initially and then declined with mean length. Prey size had no significant effect on Cmax whereas D90 declined significantly with increasing prey size. Selection for relatively larger prey and selection for large cladocerans relative to cyclopoid copepods increased significantly with walleye mean length. Walleye larvae consistently selected most strongly for relatively uncommon prey. Selection for relatively smaller prey and selection for cyclopoid copepods relative to large cladocerans increased significantly with total prey abundance in field studies and some laboratory studies. Variance in prey selection showed a significant, negative relationship with prey abundance in laboratory studies. Selection for medium (≥ 0.3–0.6 mm body width) relative to small (< 0.3 mm) prey declined significantly with increasing temperature in field studies. Our results suggest that the feeding success of walleye larvae may be limited by both the abundance and size composition of the zooplankton communities in natural environments.
Phosphorus Metabolism Monitored by 31P NMR in Juvenile Sea Scallop (Placopecten magellanicus) Overwintering in Pearl Nets at a Nova Scotian Aquaculture Site
Authors: Jackson A. E. , deFreitas A. S. W. , Hooper L. , Mallet A. , Walter J. A.
Published: November 2008

31P Nuclear magnetic resonance (NMR) spectroscopy has been used to examine in vivo phosphorus metabolism in juvenile sea scallop (Placopecten magellanicus) from an aquaculture site in Nova Scotia. NMR-visible arginine phosphate (Arg P) concentrations declined from summer to winter whereas inorganic phosphate (Pi) levels increased and those of adenosine triphosphate (ATP) remained relatively constant. Our results indicate that, in the scallop that uses the phosphagen Arg P to replenish ATP, the ratio of Arg P to Pi is a better indicator of energetic status than is the ratio of adenylate concentrations known as adenylate energy charge. Scallops collected in fall and winter, when exposed to hypoxic conditions, showed pronounced decreases in Arg P associated with increases in Pi and decreases in ATP levels whereas these remained relatively unchanged in scallops collected in summer. Scallops maintained under simulated winter conditions showed lower levels of Arg P associated with poor nutrition, and a response to hypoxia similar to field scallops. The marked seasonality in concentrations of phosphorus metabolites emphasizes their potential importance as useful biomarkers in environmental stress assessment and the optimization of hatchery and grow-out conditions.
Cooperative Fisheries Management Involving First Nations in British Columbia: An Adaptive Approach to Strategy Design
Authors: McDaniels Timothy L. , Healey Michael , Paisley Richard Kyle
Published: November 2008

In 1991, a substantial program of cooperative salmon fishery management involving First Nations was initiated in British Columbia. This paper considers how ongoing cooperative management initiatives in this fishery could be designed and implemented. The process discussed in the paper could be viewed as an adaptive management experiment in institutional design for cooperative management. First, sets of fundamental objectives for cooperative management and strategies for achieving these objectives are developed. The methods for structuring objectives and developing strategies are drawn from decision analysis practice. Then the actual experience in implementing a version of one of the strategies during the 1992 Fraser River sockeye salmon First Nations fishery is discussed. The highly publicized and controversial events of the 1992 season are instructive about how cooperative management should be implemented in other contexts.
What Can Be Learned from the Collapse of a Renewable Resource? Atlantic Cod, Gadus morhua, of Newfoundland and Labrador
Authors: Hutchings Jeffrey A. , Myers Ransom A.
Published: November 2008

Temporal changes in demography, population sustainability, and harvest rates support the hypothesis that overexploitation precipitated the commercial extinction of northern cod, Gadus morhua, off Newfoundland and Labrador in 1992. Annual estimates of realized population growth (r) indicate that the stock was rarely sustainable at the age-specific survival and fecundity rates experienced since 1962. A twofold decline in annual survival probabilities in the 1980s was concomitant with increased inshore and offshore fishing effort, declining catch rate, and spatial shifts in gillnetting effort from areas of low (inshore) to high (offshore) catch rates. We reject hypotheses that attribute the collapse of northern cod to environmental change. Water temperature was associated neither with juvenile nor adult abundance nor with adult distribution by depth. Harvests equivalent to those of the past decade were sustainable in the nineteenth and early twentieth centuries in a considerably colder environment. An updated analysis of previous work indicates that salinity has little effect on recruitment. We conclude that the collapse of northern cod can be attributed solely to overexploitation and that population sustainability indices such as r provide a means by which the susceptibility and resilience of exploited populations can be assessed and their probability of commercial extinction reduced.
GEODESIC FLOW ON EXTENDED BOTT–VIRASORO GROUP AND GENERALIZED TWO-COMPONENT PEAKON TYPE DUAL SYSTEMS
Authors: GUHA PARTHA
Published: November 2008

This paper discusses an algorithmic way of constructing integrable evolution equations based on Lie algebraic structure. We derive, in a pedagogical style, a large class of two-component peakon type dual systems from their two-component soliton equations counter part. We study the essential aspects of Hamiltonian flows on coadjoint orbits of the centrally extended semidirect product group [Formula: see text] to give a systematic derivation of the dual counter parts of various two-component of integrable systems, viz., the dispersive water wave equation, the Kaup–Boussinesq system and the Broer–Kaup system, using moment of inertia operators method and the (frozen) Lie–Poisson structure. This paper essentially gives Lie algebraic explanation of Olver–Rosenau's paper [31].
A NONLINEAR MODEL FOR RELATIVISTIC ELECTRONS AT POSITIVE TEMPERATURE
Authors: HAINZL CHRISTIAN , LEWIN MATHIEU , SEIRINGER ROBERT
Published: November 2008

We study the relativistic electron-positron field at positive temperature in the Hartree–Fock approximation. We consider both the case with and without exchange terms, and investigate the existence and properties of minimizers. Our approach is non-perturbative in the sense that the relevant electron subspace is determined in a self-consistent way. The present work is an extension of previous work by Hainzl, Lewin, Séré and Solovej where the case of zero temperature was considered.
AMPHICHEIRALS ACCORDING TO TAIT AND HASEMAN
Authors: HONGLER CAM VAN QUACH , WEBER CLAUDE
Published: November 2008

In this essay, we present our interpretation of the work of P. Tait and M. Haseman on achiral alternating knots. We have tried to elucidate the meaning of several concepts used by them such as: Amphicheirals, skew-amphicheirals, 1st or 2nd order, 1st or 2nd class, distorsions, etc. We also comment on some of their many pictures.
A MULTI-VARIABLE POLYNOMIAL INVARIANT FOR VIRTUAL KNOTS AND LINKS
Authors: MIYAZAWA YASUYUKI
Published: November 2008

We construct a multi-variable polynomial invariant for virtual knots and links via the concept of a decorated virtual magnetic graph diagram. The invariant is a generalization of the Jones–Kauffman polynomial for virtual knots and links. We show some features of the invariant including an evaluation of the virtual crossing number of a virtual knot or link.
MÖBIUS TRANSFORMATIONS OF POLYGONS AND PARTITIONS OF 3-SPACE
Authors: RANDELL RICHARD , SIMON JONATHAN , TOKLE JOSHUA
Published: November 2008

The image of a polygonal knot K under a spherical inversion of ℝ3 ∪ ∞ is a simple closed curve made of arcs of circles, perhaps some line segments, having the same knot type as the mirror image of K. But suppose we reconnect the vertices of the inverted polygon with straight lines, making a new polygon [Formula: see text]. This may be a different knot type. For example, a certain 7-segment figure-eight knot can be transformed to a figure-eight knot, a trefoil, or an unknot, by selecting different inverting spheres. Which knot types can be obtained from a given original polygon K under this process? We show that for large n, most n-segment knot types cannot be reached from one initial n-segment polygon, using a single inversion or even the whole Möbius group.

The number of knot types is bounded by the number of complementary domains of a certain system of round 2-spheres in ℝ3. We show the number of domains is at most polynomial in the number of spheres, and the number of spheres is itself a polynomial function of the number of edges of the original polygon. In the analysis, we obtain an exact formula for the number of complementary domains of any collection of round 2-spheres in ℝ3. On the other hand, the number of knot types that can be represented by n-segment polygons is exponential in n.

Our construction can be interpreted as a particular instance of building polygonal knots in non-Euclidean metrics. In particular, start with a list of n vertices in ℝ3 and connect them with arcs of circles instead of line segments: Which knots can be obtained? Our polygonal inversion construction is equivalent to picking one fixed point p ∈ ℝ3 and replacing each edge of K by an arc of the circle determined by p and the endpoints of the edge.
BRANCHED SHADOWS AND COMPLEX STRUCTURES ON 4-MANIFOLDS
Authors: COSTANTINO FRANCESCO
Published: November 2008

We define and study branched shadows of 4-manifolds as a combination of branched spines of 3-manifolds and of Turaev's shadows. We use these objects to combinatorially represent 4-manifolds equipped with Spinc-structures and homotopy classes of almost complex structures. We then use branched shadows to study complex 4-manifolds and prove that each almost complex structure on a 4-dimensional handlebody is homotopic to a complex one.
Effect of intraperitoneal and intravenous administration of cholecystokinin-8 and apolipoprotein AIV on intestinal lymphatic CCK-8 and apo AIV concentration
Authors: Lo Chun-Min , Xu Min , Yang Qing , Zheng Shuqin , Carey Katherine M. , Tubb Matthew R. , Davidson W. Sean , Liu Min , Woods Stephen C. , Tso Patrick
Published: November 2008

CCK and apolipoprotein AIV (apo AIV) are gastrointestinal satiety signals whose synthesis and secretion by the gut are stimulated by fat absorption. Intraperitoneally administered CCK-8 is more potent in suppressing food intake than a similar dose administered intravenously, but the reason for this disparity is unclear. In contrast, both intravenous and intraperitoneally administered apo AIV are equally as potent in inhibiting food intake. When we compared the lymphatic concentration of CCK-8 and apo AIV, we found that neither intraperitoneally nor intravenously administered CCK-8 or apo AIV altered lymphatic flow rate. Interestingly, intraperitoneal administration of CCK-8 produced a significantly higher lymphatic concentration at 15 min than did intravenous administration. Intraperitoneal injection of apo AIV also yielded a higher lymphatic concentration at 30 min than did intravenous administration. Intraperitoneal administration of CCK-8 and apo AIV also resulted in a much longer period of elevated CCK-8 and apo AIV peptide concentration in lymph than intravenous administration. Furthermore, enzymatic activity of dipeptidyl peptidase IV (DPPIV) and aminopeptidase was higher in plasma than in lymph during fasting, and so, satiation peptides, such as CCK-8 and apo AIV in the lymph, are protected from degradation by the significantly lower DPPIV and aminopeptidase activity levels in lymph than in plasma. Therefore, the higher potency of intraperitoneally administered CCK-8 compared with intravenously administered CCK-8 in inhibiting food intake may be explained by both its higher concentration in lymph and the prolonged duration of its presence in the lamina propria.
No effect of nutritional adenosine receptor antagonists on exercise performance in the heat
Authors: Cheuvront Samuel N. , Ely Brett R. , Kenefick Robert W. , Michniak-Kohn Bozena B. , Rood Jennifer C. , Sawka Michael N.
Published: November 2008

Nutritional adenosine receptor antagonists can enhance endurance exercise performance in temperate environments, but their efficacy during heat stress is not well understood. This double-blinded, placebo-controlled study compared the effects of an acute dose of caffeine or quercetin on endurance exercise performance during compensable heat stress (40°C, 20–30% rh). On each of three occasions, 10 healthy men each performed 30-min of cycle ergometry at 50% V̇o2peak followed by a 15-min performance time trial after receiving either placebo ( Group P), caffeine ( Group C; 9 mg/kg), or quercetin ( Group Q; 2,000 mg). Serial blood samples, physiological (heart rate, rectal, and mean skin body temperatures), perceptual (ratings of perceived exertion, pain, thermal comfort, motivation), and exercise performance measures (total work and pacing strategy) were made. Supplementation with caffeine and quercetin increased preexercise blood concentrations of caffeine (55.62 ± 4.77 μM) and quercetin (4.76 ± 2.56 μM) above their in vitro inhibition constants for adenosine receptors. No treatment effects were observed for any physiological or perceptual measures, with the exception of elevated rectal body temperatures (0.20–0.30°C; P < 0.05) for Group C vs. Groups Q and P. Supplementation did not affect total work performed ( Groups P: 153.5 ± 28.3, C: 157.3 ± 28.9, and Q: 151.1 ± 31.6 kJ; P > 0.05) or the self-selected pacing strategy employed. These findings indicate that the nutritional adenosine receptor antagonists caffeine and quercetin do not enhance endurance exercise performance during compensable heat stress.