bluuebunny/crossref_metadata_2025 huggingface dataset:
Violent attacks on Middle Easterners in the United States during the month following the September 11, 2001 terrorist attacks: Figure 1
Authors: Swahn M H , Mahendra R R , Paulozzi L J , Winston R L , Shelley G A , Taliano J , Frazier L , Saul J R
Published: June 2003

Objectives:To document and describe hate related violent attacks on Middle Easterners or those perceived to be Middle Easterners during the month following the September 11, 2001 terrorist attacks in New York City and Washington, DC.

Methods:The LexisNexis database of newspaper reports were used to identify incidents of hate related violent acts against Middle Easterners or those perceived to be Middle Easterners in the US between September 1 and October 11, 2001. A total of 100 incidents of hate related violence were identified in the 2659 news articles that were reviewed.

Results:Of the 100 incidents of violent victimization that took place during the period September 1 to October 11, only one incident occurred before September 11. The 99 incidents that occurred after September 11 involved at least 128 victims and 171 perpetrators. Most violent victimizations occurred within 10 days of the attacks, involved male perpetrators and male victims, and occurred in convenience stores, on the streets, at gas stations, at schools/colleges, and at places of worship.

Discussion:Most violent victimizations occurred in the 10 days immediately following the terrorist attacks indicating that interventions that promote tolerance and understanding of diversity need to be implemented quickly in order to be effective. In addition, patrolling by police and Neighborhood Watch programs around convenience stores and gas stations may also be effective strategies for reducing hate related violent crimes.
Cyprinid fishes as samplers of benthic diatom communities in freshwater streams of varying water quality
Authors: Rosati Ted C , Johansen Jeffrey R , Coburn Miles M
Published: June 2003

The diatom composition of natural substrates in streams of different water qualities was compared among samples collected by researchers and samples collected from the intestine contents of three species of Cyprinid fishes: Campostoma anomalum, Pimephales notatus, and Semotilus atromaculatus. Campostoma and Pimephales were found to be robust samplers that efficiently collected diverse, representative diatom samples. Semotilus were adequate diatom samplers but collected the most diverse samples. In no instance were water-quality indices calculated from Pimephales samples significantly different from human-collected composite samples, whereas Campostoma and Semotilus samples diverged slightly from human-collected composite samples. Internal similarities of fish-collected samples were not significantly higher than those of human-collected samples, indicating that the fish were indiscriminately foraging on diatoms. Furthermore, samples clustered primarily by stream, indicating that fish-collected samples of diatoms were as representative of the stream as those collected by human researchers. By all standards measured in this study, these three fish species sample the benthic diatom community of mid-order streams with a facility equal to that of trained ecologists.
Physiological energetics of Lake Erie dreissenid mussels: a basis for the displacement of Dreissena polymorpha by Dreissena bugensis
Authors: Stoeckmann Ann
Published: June 2003

I measured respiration, shell growth, body mass, and reproduction in sympatric populations of zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels in western Lake Erie to determine if the species differ in physiological parameters and if any differences provide an explanation for the recent displacement of zebra mussels by quagga mussels. Between May and August, I measured respiration (1998), shell growth of marked mussels suspended in cages in the lake (19992000), soft body mass and mass of gametes released (19982001), and the number of gametes released by individual mussels (1999). Quagga mussels had lower respiration rates and greater shell growth and body mass. There was no difference in the percentage of spawning mussels or the number of sperm released by individuals, but zebra mussels generally released more eggs and a greater mass of gametes than did quagga mussels. Similar reproduction at a lower body mass indicates that zebra mussels devote a greater proportion of body tissue to reproduction. Lower respiration rates and larger size give quagga mussels a competitive advantage and may explain their displacement of zebra mussels.
Explaining diet composition of North Sea cod (Gadus morhua): prey size preference vs. prey availability
Authors: Floeter Jens , Temming Axel
Published: June 2003

The nature and significance of size preference for fish prey in the diet selection of North Sea cod (Gadus morhua L.) was analysed. The analysis combined information on size-specific abundance derived from bottom trawl surveys with prey size frequencies in cod stomachs from the International North Sea Stomach Database. To estimate the abundance of all potential fish prey in the sea, a length-based number spectrum was calculated, corrected for gear efficiency by the application of a species-specific correction factor, and weighted by local predator abundance to take the spatialtemporal overlap between cod and its prey into consideration. A prey size preference model for cod feeding on fish is presented. Results showed that the preferred predator-to-prey weight ratio is an exponentially increasing function of predator size and an exponentially decreasing function of the slope of the number spectrum. More than 75% of fish found in the stomachs of North Sea cod originated from the least preferred quartile of the prey size range, indicating that prey abundance is the main determinant of the diet composition.
pH 6 as the threshold to use in critical load modeling for zooplankton community change with acidification in lakes of south-central Ontario: accounting for morphometry and geography
Authors: Holt C A , Yan N D , Somers K M
Published: June 2003

Identifying thresholds of biotic community change along stressor gradients may be useful to both ecologists and lake managers; however, there are several weaknesses in the thresholds that have been identified for zooplankton communities along acidity gradients. The thresholds are often based on a single species even though pH sensitivities vary among species. They often measure changes in species occurrences, though abundances may be a more responsive indicator of damage. Their identification may be confounded by spatial and morphometric factors if they are derived from lake surveys. Finally, the thresholds have usually been subjectively identified. Our goal was to establish a threshold in zooplankton community change along an acidity gradient that did not have these four common weaknesses. We used two crustacean zooplankton community metrics: species richness and scores of a correspondence analysis based on species abundances. Spatial and morphometric patterns were detected in the zooplankton community data and then extracted. The relationship between zooplankton and acidity was then modeled using a step function that objectively identified a threshold of community change at pH 6 for lakes in south-central Ontario.
The importance of habitat quality for marine reserve  fishery linkages
Authors: Rodwell Lynda D , Barbier Edward B , Roberts Callum M , McClanahan Tim R
Published: June 2003

We model marine reserve  fishery linkages to evaluate the potential contribution of habitat-quality improvements inside a marine reserve to fish productivity and fishery catches. Data from Mombasa Marine National Park, Kenya, and the adjacent fishery are used. Marine reserves increase total fish biomass directly by providing refuge from exploitation and indirectly by improving fish habitat in the reserve. As natural mortality of the fish stock decreases in response to habitat enhancement in the reserve, catches increase by up to 2.6 tonnes (t)·km2·year1 and total fish biomass by up to 36 t·km2. However, if habitat-quality improvement reduces the propensity of fish to move out of the reserve, catches may fall by up to 0.9 t·km2·year1. Our results indicate that habitat protection in reserves can underpin fish productivity and, depending on its effects on fish movements, augment catches.
Optimal effort controls for the multispecies groundfish complex in New England: what might have been
Authors: Holland Daniel S , Maguire Jean-Jacques
Published: June 2003

Age-structured models are used to calculate catches and revenues of the principal stocks in the northeast multispecies groundfish fishery over the 19821997 period assuming alternative control rules on fishing effort had been employed. Various static levels of nominal effort are compared with controls that maintain fishing mortality below overfishing thresholds for all stocks. An unambiguous result from this analysis is that substantial reductions in fishing effort would have increased the value of the fishery even if resulting increases in spawning stock biomass (SSB) had not increased recruitment. Simple controls on nominal effort designed to maximize revenues would have provided nearly equivalent revenues to those achieved by maintaining fishing mortality for each stock at its individual maximum sustainable yield (FMSY) but would have led to overfishing of some stocks. Without the ability to tune the relative catches across stocks, strict controls on effort designed to prevent overfishing on individual stocks would likely have resulted in significantly lower and more variable revenues. Achieving SSB targets for three stocks would not have been possible given the observed recruitment.
Effects of adult common carp (Cyprinus carpio) on multiple trophic levels in shallow mesocosms
Authors: Parkos III Joseph J , Santucci, Jr. Victor J , Wahl David H
Published: June 2003

We examined the effects of adult common carp (Cyprinus carpio) on shallow aquatic ecosystems and compared the effects with those of a native benthic fish, channel catfish (Ictalurus punctatus). Experimental ponds contained enclosures (0.06 ha) with a low carp biomass (174 kg·ha1), high carp biomass (476 kg·ha1), high catfish biomass (416 kg·ha1), and no fish. We measured abiotic factors (turbidity, suspended solids, total phosphorus), as well as effects on adjacent trophic levels (aquatic macrophytes, zooplankton, and aquatic macroinvertebrates) from July to September. Common carp was positively related to total phosphorus, turbidity, suspended solids, and zooplankton biomass, and negatively related to macrophyte and macroinvertebrate abundance. Suspended solids in the carp treatments consisted primarily of inorganic particles. Carp were either positively or negatively related to phytoplankton, depending on zooplankton abundance. A high biomass of carp had greater effect on nutrients, turbidity, and suspended solids than a low biomass. Channel catfish was positively related to total phosphorus concentrations and altered zooplankton composition, but did not affect turbidity, suspended solids, macroinvertebrates, and macrophytes. These results suggest that common carp have a stronger influence on water quality and aquatic community structure than benthic fish native to North America.
Patterns and correlates of movement and site fidelity in individually tagged young-of-the-year Atlantic salmon (Salmo salar)
Authors: Steingrímsson Stefán Ó , Grant James W.A
Published: June 2003

The literature on stream fish movement offers diverse views on the patterns (restricted vs. nonrestricted), causes (competition vs. habitat use), and consequences (mobile fish of lower vs. equal fitness) of movement. We tagged 320 young-of-the-year Atlantic salmon (Salmo salar) (30.155.3 mm), using relatively noninvasive tagging (elastomers) and recovery (snorkeling) techniques, to test these alternative views. Most fish (mean = 63.8%) stayed in the study sites (10120 m) throughout their respective study season (2874 days). Of the resighted fish, 61.8% moved less than 1 m up- or down-stream and only three fish moved more than 10 m, causing extremely leptokurtic movement curves. Movement and site fidelity were weakly affected by habitat use and competition. Fish originally found in slow water moved farther than fish from fast water, whereas fish found at high population densities were more likely to disappear than fish from low densities. Finally, mobile fish grew as fast or faster than more sedentary fish, supporting the idea that movement can be advantageous and is not just a by-product of density-dependent population regulation.
Responses of organic matter and macroinvertebrates to placements of boulder clusters in a small stream of southwestern British Columbia, Canada
Authors: Negishi Junjiro N , Richardson John S
Published: June 2003

Diversity and productivity of stream food webs are related to habitat heterogeneity and efficiency of energy retention. We tested the hypothesis that experimental boulder placements in a second-order stream would increase diversity and abundance of macroinvertebrates by restoring detrital retention and habitat heterogeneity. Two relatively natural, upstream, reference reaches and a downstream treatment reach with a relatively straight channel and less woody debris were studied for 3 months before and 1.2 years after the placement of six boulder clusters in the treatment reach. Mean velocity and its coefficient of variation increased in the treatment reach (140 and 115%, respectively), whereas the reference reaches remained relatively unchanged after the placements. Enhanced particulate organic matter storage (550%) was accompanied by increased total macroinvertebrate abundance (280%) in the treatment reach, converging with those of the reference reaches almost 1 year after the treatment. Detritivorous taxa numerically dominated the macroinvertebrate community, the total densities of which were best predicted by the fine fraction of organic matter biomass at microhabitat scale. However, the effect of boulder clusters on taxonomic richness was negligible. Our findings suggest that boulder clusters can be used at least as a short-term means to restore macroinvertebrate productivity in detritus-based stream systems.
A simple method for assaying extracellular hydroxyl radical activity and its application to natural and synthetic waters
Authors: Molot L A , Miller S A , Dillon P J , Trick C G
Published: June 2003

An assay has been developed to measure extracellular hydroxyl radical (OH*) activity in algal culture media and natural waters over a 4- to 5-day period. The first-order rate constant, k, for loss of absorbance at 590 or 620 nm was determined for erioglaucine, which is sensitive to OH*, insensitive to superoxide and hydrogen peroxide, and stable in the dark and under artificial radiation (280750 nm) and solar radiation in the absence of oxidants. Variation in irradiance was accounted for by normalizing k with k for a ferric iron reference solution with dye (k/kfe). Trends in k/kfe for streams and lakes were consistent with previous data on photochemical oxidation rates of dissolved organic matter. Values for k/kfe were similar in filtered surface waters of eutrophic Heart Lake and nearby mesotrophic Lake St. George under artificial radiation. Hence, extracellular OH* did not appear to be a direct cause of the onset of a nuisance cyanobacterial bloom in Heart Lake, nor did OH* appear related to the absence of a bloom in Lake St. George. k/kfe was two orders of magnitude higher in algal culture media supplied with 8.8 mM nitrate than in lake waters.
Effects of episodic acidification on Atlantic salmon (Salmo salar) smolts
Authors: Magee J A , Obedzinski M , McCormick S D , Kocik J F
Published: June 2003

The effect of episodic acidification on Atlantic salmon (Salmo salar) smolt physiology and survival in fresh water (FW) and seawater (SW) was investigated. Smolts were held in either ambient (control, pH 6.06.6), acidified (chronic, pH 4.46.1), or episodically acidified (episodic, pH reduction from control levels to pH ~5.2 for 48 h once weekly) river water for 31 days and then transferred to 34 SW. Smolts fed little while in acidified conditions and chronic smolts did not grow in length or weight. In FW, chronic smolts experienced increases in hematocrit and plasma potassium and reductions in plasma sodium and chloride. Upon transfer to SW, chronic and episodic smolts experienced reductions in hematocrit, increases in plasma sodium, chloride, and potassium levels, and suffered mortalities. Gill Na+,K+-ATPase and citrate synthase activities were reduced by exposure to acid. For most parameters, the effect of episodic acid exposure was less than that of chronic acidification. Exposure to acidic conditions, even when short in duration and followed by a 30-h recovery period in suitable water (pH 6.5), led to a 35% mortality of smolts upon transfer to SW. This study highlights the importance of measuring and assessing sublethal stresses in FW and their ultimate effects in marine ecosystems.
Long-term changes in the trophic level of western Mediterranean fishery and aquaculture landings
Authors: Pinnegar J K , Polunin N V.C , Badalamenti F
Published: June 2003

We explored changes in western Mediterranean fishery and aquaculture landings using trophic level (TL) estimates derived from nitrogen stable isotope analysis combined with geographically detailed fishery data collated by the General Fisheries Council for the Mediterranean (GFCM). Our analyses confirmed earlier suggestions that there has been a significant decline in the mean trophic level of Mediterranean landings (by ~0.15 TL over 26 years). However, this decline is suggested to be almost entirely a result of increased landings of bivalve molluscs from mariculture and not due to changes in landings from capture fisheries. The mean trophic level of finfish landings has not changed significantly since 1973, although both fish and total landings have become significantly more diverse. Inspection of small pelagic fish landings revealed a marked decrease in the contribution played by anchovy and replacement of this species by sardine. Since 1981, cage culture of high trophic level species such as sea bass (Dicentrarchus labrax) and seabream (Sparus aurata) has become increasingly important, such that when clupeoid landings were excluded from the analyses, the mean trophic level of finfish landings was actually demonstrated to have increased over the past 26 years.
A functional growth model with intraspecific competition applied to a sea urchin, Paracentrotus lividus
Authors: Grosjean Ph. , Spirlet Ch. , Jangoux M
Published: June 2003

A new growth model is fitted on data from reared sea urchins, Paracentrotus lividus. Quantile regressions are used instead of least-square regressions, because they are insensitive to the dimension of the measurement and accommodate more than just symmetrical distributions. Quantile regressions allow comparison of fittings on various parts of the size distributions, including large competitors versus small, inhibited animals, in the presence of a size-based intraspecific competition. The model has functionally interpretable parameters and allows quantifying of the intensity of growth inhibition. An extension of this model, called "envelope model", fits the whole data set at once, including size distributions. Its parameters are constrained using information about underlying biological processes involved, namely asymptotic growth with inhibition in early ages as the result of intraspecific competition, the intensity of which depends on the relative size of the individual in the cohort. The new model appears most adequate to describe growth of P. lividus and probably many other sea urchins species as well as other animals or plants.
Catchability and the spatial distribution of fishing vessels
Authors: Salthaug Are , Aanes Sondre
Published: June 2003

A central problem when using commercial catch per unit effort (CPUE) as an index of fish stock abundance is that fishing vessels search for concentrations of fish. For a given stock abundance, CPUE may become high if the vessels succeed in finding patches of fish and low if the vessels distribute their catching operations more randomly. In this work, the relationship between catchability and two measures of the degree of spatial concentration of a trawl fleet (the fleet's spatial extent and the fleet's degree of spatial patchiness) is investigated for four different fish stocks. The catchability of northeast Arctic cod (Gadus morhua) is strongly related to the fleet's degree of spatial concentration, but the relationship is weaker for northeast Arctic haddock (Melanogrammus aeglefinus), and no relationships appear for two saithe (Pollachius virens) stocks. Our findings suggest that adjusting CPUE with a measure of the fleet's average degree of concentration relates CPUE more strongly with abundance for migratory stocks.
Influence of streamside vegetation on inputs of terrestrial invertebrates to salmonid food webs
Authors: Allan J David , Wipfli Mark S , Caouette John P , Prussian Aaron , Rodgers Joanna
Published: June 2003

Salmonid food webs receive important energy subsidies via terrestrial in-fall, downstream transport, and spawning migrations. We examined the contribution of terrestrially derived invertebrates (TI) to juvenile coho (Oncorhynchus kisutch) in streams of southeastern Alaska by diet analysis and sampling of TI inputs in 12 streams of contrasting riparian vegetation. Juvenile coho ingested 12.1 mg·fish1of invertebrate mass averaged across all sites; no significant differences associated with location (plant or forest type) were detected, possibly because prey are well mixed by wind and water dispersal. Terrestrial and aquatic prey composed approximately equal fractions of prey ingested. Surface inputs were estimated at ~80 mg·m2·day1, primarily TI. Direct sampling of invertebrates from the stems of six plant species demonstrated differences in invertebrate taxa occupying different plant species and much lower TI biomass per stem for conifers compared with overstory and understory deciduous plants. Traps placed under red alder (Alnus rubra) and conifer (mix of western hemlock (Tsuga heterophylla) and Sitka spruce (Picea sitchensis)) canopies consistently captured higher biomass of TI under the former. Management of riparian vegetation is likely to influence the food supply of juvenile coho and the productivity of stream food webs.
Seasonal variations in tissue metabolic capacities of yellow perch (Perca flavescens) from clean and metal-contaminated environments
Authors: Audet Debbie , Couture Patrice
Published: June 2003

This study examined seasonal variations in tissue metal contamination and physiological condition of yellow perch (Perca flavescens) from a clean lake (Halfway Lake) and a metal-contaminated environment (Whitson Lake) in spring, summer, and fall of 1999. Dietary metal content influenced liver metal concentrations, especially for cadmium. Fulton's condition factor (FCF), an indicator of recent feeding activity, was lower in Whitson fish except in summer, when higher FCF values corresponded with higher liver copper concentrations, presumably because of higher feeding rate. Tissue protein concentrations and indicators of biosynthetic capacities (nucleoside diphosphate kinase and RNA/DNA ratios) suggested lower biosynthesis in Whitson fish. Muscle aerobic and anaerobic capacities (using citrate synthase and lactate dehydrogenase as indicators, respectively) were consistently lower in Whitson fish, with maximal differences in summer. In contrast, although liver aerobic capacities were generally comparable among populations, anaerobic capacities were much higher in Whitson fish. Finally, gill sodium/potassium adenosinetriphosphatase (Na+/K+ATPase) activity peaked in the spring in fish from both lakes, and higher activities were correlated with elevated gill copper concentrations. This study highlights the importance of seasonal variations in tissue metal concentrations and fish condition. This information is essential to evaluate the extent of impairment in condition faced by metal-contaminated wild fish.
Fish habitat management implications of the summer habitat use by littoral fishes in a north temperate, mesotrophic lake
Authors: Pratt Thomas C , Smokorowski Karen E
Published: June 2003

Compensation measures in response to Fisheries and Oceans Canada (DFO) Policy for the Management of Fish Habitat includes provisions for habitat creation and enhancement. Thus, an assessment of nearshore habitat utilization patterns by fishes is needed to put DFO compensation measures in the context of the "no net loss of the productive capacity of fish habitat" directive. Measures of abundance, richness, and diversity of fishes were compared across nine habitat types in a lake using rapid visual underwater assessment. Multivariate analyses separated habitats into three groups and identified two distinct species assemblages. Most species were associated with macrophytes, but a few were primarily associated with rocky substrate. Shallow mud (open) habitats contained significantly fewer species and had lower mean scores and diversity than all other habitat types. Rocky habitats had lower mean scores and diversity than some vegetated habitat types containing similar fish assemblages. Surprisingly, within-site fish assemblage heterogeneity was similar to among-site heterogeneity, and among-habitat heterogeneity was lower than within-habitat heterogeneity, further supporting our inability to distinguish among vegetated habitat types. Our results suggest that habitat heterogeneity is critical in maintaining diverse communities and that compensation measures should account for differences in fishhabitat associations among varied habitats.
Swimming performance of blacknose dace (Rhinichthys atratulus) mirrors home-stream current velocity
Authors: Nelson Jay A , Gotwalt Portia S , Snodgrass Joel W
Published: June 2003

Flowing waters may represent a force that structures the locomotor capacity of stream fishes. We used a modified critical swimming speed (Ucrit) procedure to investigate the relationship between base-flow conditions and locomotor performance of blacknose dace (Rhinichthys atratulus) from five sites within three watersheds of Baltimore County, Maryland. Our modified test used 5-min intervals between incremental increases of 5 cm·s1in swim-tunnel current velocity. This time increment represented a realistic transit time across riffles found in the home streams of dace. To characterize current velocity conditions of the streams, we measured current velocity at 55 evenly spaced points per site during base-flow conditions. Swimming performance varied greatly among 32 individual fish from the five sites (55Ucritfrom 26.33 to 69.00 cm·s1) and was positively correlated (r2= 0.38, p = 0.002) with mean base-flow current velocities at the site of collection. Additionally, among fish from the site with the widest and most even distribution of current velocities (from 0 to 54 cm·s1), we observed the largest range of swimming performances. Our results suggest that variation in flow conditions among streams influences swimming ability of blacknose dace and can result in heretofore-unappreciated intraspecific variation in swimming performance.
Effects of condition on fecundity and total egg production of eastern Scotian Shelf haddock (Melanogrammus aeglefinus)
Authors: Blanchard Julia L , Frank Kenneth T , Simon James E
Published: June 2003

A fecundity study of the eastern Scotian Shelf haddock (Melanogrammus aeglefinus) stock during the 19971999 spawning seasons is reported. We developed a model that accounted for fecundity changes at the individual level and that could be used to estimate population egg production beyond the study period. Incorporating condition factors into the model (relative condition factor (Kn) and hepatosomatic index) accounted for a significant proportion of the residual variation. The model predicted that a change in Kn from 0.8 to 1.0 resulted in a twofold increase in fecundity at length. This variability was as great as that observed for fecunditylength relationships among stocks. Three time series (19792001) of total egg production (TEP) were constructed using different fecundity relationships: one with a condition effect, one based on length only, and one based on weight only. The magnitude of change in TEP resulting from the condition effect ranged from +30 to 20%. Condition effects during the first half of the time series resulted in an enhancement of TEP, whereas in the latter half, condition effects depressed TEP. This evaluation of TEP generated new insights into haddock stock dynamics but did not result in a dramatic improvement of the relationship between recruitment and stock reproductive potential.
Predicting stream temperatures: geostatistical model comparison using alternative distance metrics
Authors: Gardner Beth , Sullivan Patrick J , Lembo, Jr. Arthur J
Published: June 2003

The Beaverkill Watershed in the Catskill Mountains of New York, U.S.A., shows evidence of high summer stream temperatures throughout critical trout habitat. Because habitat quality, as characterized by stream temperature, dramatically influences trout communities, it is important for biologists to identify and map these characteristics and to monitor how they change over time. Stream temperatures were recorded over time throughout the Beaverkill Watershed and were used to identify thermal refugia and areas of thermal stress. Seventy-two temperature loggers were placed throughout the watershed during the summer of 2000. Three geostatistical metrics for predicting temperature across the watershed were constructed and evaluated. The first metric utilized the shortest path between temperature loggers without using stream network information. A second metric used distances calculated along the stream network in both upstream and downstream directions. Our final metric was a modified network system in which the distances were weighted by stream order. Each metric was found to provide predictive capability, with added complexity improving the accuracy of represented stream temperatures.
Derivation of cause-effect based sediment quality guidelines
Authors: Borgmann Uwe
Published: June 2003

Unlike Canadian Water Quality Guidelines, Canadian Interim Sediment Quality Guidelines (ISQGs) are not based on clear causeeffect relationships. They were derived using a modified U.S. National Status and Trends Program (NSTP) approach in which biological effects were compared with contaminant concentrations in field-collected sediments. Exceeding an assessment value indicates an increased likelihood of toxic effects, but correlation is not proof of cause, and it cannot be assumed that the contaminant present in excess of the assessment value is necessarily responsible for the observed effects. This has sometimes caused confusion and misinterpretation of the toxicological significance of sediment chemistry data. An alternative approach to computing sediment guidelines, based on estimating the bioavailable contaminant concentration and comparing this with concentrations known to be toxic, is proposed. Examples are given of guidelines for cadmium, copper, nickel, lead, and zinc computed using both methods for toxicity data collected from sediments in Canadian Shield lakes near smelters. The causeeffect based guidelines can be much higher than those computed using the NSTP approach. They can also be higher than toxic thresholds estimated from experiments with metal-spiked sediments. Only true causeeffect based guidelines should be used for predicting the cause of toxicity in sediments.
Stability of elemental signatures in the scales of spawning weakfish, Cynoscion regalis
Authors: Wells Brian K , Thorrold Simon R , Jones Cynthia M
Published: June 2003

We quantified elemental signatures in scales of ages-1 and -2 weakfish, Cynoscion regalis, collected during the spawning season in Pamlico Sound, Chesapeake Bay, and Delaware Bay in 1998. We compared these signatures with elemental signatures from scales of juvenile weakfish collected while still resident in natal estuaries at five locations along the Atlantic coast in 1996 and 1997. Although Mg/Ca and Mn/Ca were lower in the juvenile portion of scales from adults compared with scales from juvenile fish, Sr/Ca and Ba/Ca were similar in the three age groups. We compared scale and otolith chemistries from juveniles and adults to determine if relative concentrations of elements/Ca in scales remained consistent, even if absolute levels were altered. Scale Mn/Ca and Ba/Ca remained correlated with those in otoliths of adult fish. Finally, we examined the ability of elemental signatures in scales to act as natural tags of natal estuaries in spawning weakfish. Allocation of fish to natal estuaries based on geochemical signatures in scales and otoliths from age-1 fish was similar; however, allocation was different for age-2 fish. Elemental signatures in scales degraded after the juvenile period and after maturation were insufficiently stable for use as a natural tag of natal origins in weakfish.
Using mixed models to combine smooth size-selection and catch-comparison curves over hauls
Authors: Fryer R J , Zuur A F , Graham N
Published: June 2003

Parametric size-selection curves are often combined over hauls to estimate a mean selection curve using a mixed model in which between-haul variation in selection is treated as a random effect. This paper shows how the mixed model can be extended to estimate a mean selection curve when smooth nonparametric size-selection curves are used. The method also estimates the between-haul variation in selection at each length and can model fixed effects in the form of the different levels of a categorical variable. Data obtained to estimate the size-selection of dab by a Nordmøre grid are used for illustration. The method can also be used to provide a length-based analysis of catch-comparison data, either to compare a test net with a standard net or to calibrate two research survey vessels. Haddock data from an intercalibration exercise are used for illustration.
Dynamic factor analysis to estimate common trends in fisheries time series
Authors: Zuur A F , Tuck I D , Bailey N
Published: June 2003

Dynamic factor analysis (DFA) is a technique used to detect common patterns in a set of time series and relationships between these series and explanatory variables. Although DFA is used widely in econometric and psychological fields, it has not been used in fisheries and aquatic sciences to the best of our knowledge. To make the technique more widely accessible, an introductory guide for DFA, at an intermediate level, is presented in this paper. A case study is presented. The analysis of 13 landings-per-unit-effort series for Nephrops around northern Europe identified three common trends for 12 of the series, with one series being poorly fitted, but no relationships with the North Atlantic Oscillation (NAO) or sea surface temperature were found. The 12 series could be divided into six groups based on factor loadings from the three trends.
Brook trout (Salvelinus fontinalis) response to wood removal from high-gradient streams of the Adirondack Mountains (N.Y., U.S.A.)
Authors: Warren Dana R , Kraft Clifford E
Published: June 2003

A beforeafter, controlimpact study was conducted to evaluate brook trout (Salvelinus fontinalis) response to the removal of debris dams and woody debris from an ice-storm-impacted stream system in the eastern Adirondack Mountains in New York State. A total of 10 reach pairs were established on two first-order streams, two second-order streams, and one third-order stream, all within the same watershed. Analyses, conducted separately for each stream order, used linear contrasts to compare differences in trout abundance between reference (upstream) and removal (downstream) reaches 1 month and 1 year after the manipulation. We expected trout abundance to decrease in removal reaches relative to reference reaches; however, responses varied temporally and with respect to stream order. Trout abundance had not changed significantly 1 month after removal. One year after removal, relative trout abundance had increased in the third-order stream, decreased in the second-order streams, and exhibited no significant change in the first-order streams. In areas with abundant boulders and preexisting habitat complexity, accumulated woody debris may have limited influence on trout abundance.
Quantifying habitat associations in marine fisheries: a generalization of the KolmogorovSmirnov statistic using commercial logbook records linked to archived environmental data
Authors: Reynolds Julie A
Published: June 2003

Understanding specieshabitat associations is critical for designing marine reserves, defining essential fish habitat, and predicting the impacts of climate change on fisheries. For many species, however, there is a paucity of fisheries-independent data that simultaneously track abundance and environmental variables, as is the case for widow rockfish (Sebastes entomelas), a commercially important fishery off the west coast of the United States. In this paper, I generalize a previous approach to identifying habitat associations so that fisheries-dependent data can be used. In analyzing Oregon commercial logbook records and archived environmental data from the National Oceanographic Data Center, I found three environmental variables (bottom depth, vertical depth of fish in the water column, and temperature) to be statistically adequate. Using a generalized KolmogorovSmirnov test statistic, I compared an empirically derived cumulative distribution function (CDF) of the habitat sampled to a CDF weighted by widow rockfish catch. Results suggest that the significant habitat association for widow rockfish includes bottom depths between 136 and 298 m, vertical depths between 101 and 197 m, and temperatures between 7.1 and 8.1°C. This novel use of commercial logbook data, which links disparate data sources and explicitly accounts for unequal spatial sampling, is a methodological advance that also provides initial insights into widow rockfish habitat preferences.
Population structure of two ecologically distinct forms of ninespine stickleback,Pungitius pungitius: gene flow regimes and genetic diversity based on mtDNA sequence variations
Authors: Takahashi Hiroshi , Tsuruta Tetsuya , Goto Akira
Published: June 2003

The population structure and its effect on genetic diversity were investigated in two ecologically distinct forms (fresh- and brackish-water types) of ninespine stickleback (Pungitius pungitius L.), which coexist on the coast of eastern Hokkaido, Japan. Obvious population subdivision (φST= 0.102 to 0.668) between freshwater systems in the freshwater type compared with that in the brackish-water type (φST= <0 to 0.078) was revealed on the basis of mitochondrial DNA (mtDNA) control region sequence variations. Results of the nested clade analysis suggested that the geographic distribution patterns of mtDNA lineages were mainly due to the contemporary population structure, rather than population histories. Although local populations were sampled from a similar geographic range for the two types, gene and nucleotide diversities of the freshwater type were significantly greater (0.94 and 0.016) than those of the brackish-water type (0.55 and 0.003). The increment of genetic diversity should be attributable to the obvious population structure and existence of divergent mtDNA lineages in the former, which clearly increased the effective population size of a subdivided population. Although these two forms maintain distinct gene pools, small sequence differences among mtDNA haplotypes obtained from each type suggested that mtDNA introgression has occurred between them.
Effects of disturbance on contribution of energy sources to growth of juvenile chinook salmon (Oncorhynchus tshawytscha) in boreal streams
Authors: Perry Russell W , Bradford Michael J , Grout Jeffrey A
Published: June 2003

We used stable isotopes of carbon in a growth-dependent tissue-turnover model to quantify the relative contribution of autochthonous and terrestrial energy sources to juvenile chinook salmon (Oncorhynchus tshawytscha) in five small boreal streams tributary to the upper Yukon River. We used a tissue-turnover model because fish did not grow enough to come into isotopic equilibrium with their diet. In two streams, autochthonous energy sources contributed 23 and 41% to the growth of juvenile salmon. In the other three, fish growth was largely due to terrestrial (i.e., allochthonous) energy sources. This low contribution of autochthonous energy appeared to be related to stream-specific disturbances: a recent forest fire impacted two of the streams and the third was affected by a large midsummer spate during the study. These disturbances reduced the relative abundance of herbivorous macroinvertebrates, the contribution of autochthonous material to other invertebrates, and ultimately, the energy flow between stream algae and fish. Our findings suggest that disturbances to streams can be an important mechanism affecting transfer of primary energy sources to higher trophic levels.
Analysis of plankton size spectra irregularities in two subtropical shallow lakes (Esteros del Iberá, Argentina)
Authors: Cózar Andrés , García Carlos M , Gálvez José A
Published: June 2003

Biomass irregularities in the plankton size spectra of two subtropical shallow lakes have been quantified assuming the classical observed generalities of the size spectra. During a seasonal cycle, three main functional size ranges determined the allocation of the spectra irregularities: microbial food web, nanoplanktonmicroplankton autotrophs, and herbivorous organisms. The structural adjustments within these trophic positions responded to the internal competition between functional guilds, mainly as the result of size-based characteristics related to the ability to eat and the susceptibility to be eaten. Despite the existence of a typical spectrum undulation resulting from self-organization (well-defined trophic positions, limneticbenthic interaction), the biomass irregularities were an indicator of the main interactions disturbing the steady state. The mechanisms responsible for the irregularities operated jointly at ecosystem and individual levels. Thus, the irregular spectra of the eutrophic Laguna Iberá suggested a strong top-down control through cascade effects. Specific properties of peculiar organisms like filamentous cyanobacteria contributed to hold these stable irregularities. The higher spectrum regularity of the meso-oligotrophic Laguna Galarza emerged from a more balanced flow of biomass along the food chain.
The precision of otolith radiometric ageing of fish and the effect of within-sample heterogeneity
Authors: Francis R.I.C Chris
Published: June 2003

Ageing of fish using radiometric methods applied to otoliths is a widely accepted and valuable technique for validating annulus counts. Initially, whole otoliths were analysed, but it is now more frequent, and requires less stringent assumptions, to analyse otolith cores. Data from published studies were used to calculate typical ageing errors, assuming linear growth in otolith mass. These errors increase with increasing age, are much smaller if an improved method for measuring 226Ra is used, and, for older ages, are greater when cores are used (nevertheless, the use of cores, rather than whole otoliths, is recommended because the stronger assumptions required for the latter are hard to justify or verify). It is common to use more than one otolith per sample (sometimes more than 100) so as to provide sufficient sample mass, and to assume no within-sample heterogeneity in otolith age and mass-growth rate. A simulation experiment was carried out to determine whether any violation of this assumption was likely to have a significant effect on the accuracy of estimated ages. Plausible levels of heterogeneity were found to produce only a negligible decrease in precision and small bias (<10%).
Red blood cell Hsp 70 mRNA and protein as bio-indicators of temperature stress in the brook trout (Salvelinus fontinalis)
Authors: Lund Susan G , Lund Mervyn E.A , Tufts Bruce L
Published: June 2003

The purpose of this study was to examine the heat shock protein (Hsp) 70 mRNA and protein response in several tissues of Miramichi brook trout (Salvelinus fontinalis) under both acute and extended heat stress conditions to determine the utility of the red blood cell (rbc) heat shock response as a biomarker of sublethal temperature stress. Red blood cells consistently produced one of the highest responses of all of the tissues examined. Recovery of Hsp 70 mRNA following acute temperature increase required between 24 h and 48 h. In contrast, Hsp 70 protein levels remained significantly elevated for more than 48 h after the heat stress was terminated. During a 6-day extended (23°C) heat stress, rbc Hsp 70 mRNA returned to control levels between 72 and 144 h, whereas Hsp 70 protein was still significantly elevated after 6 days. Thus, although Hsp 70 mRNA proved to be a more sensitive indicator of heat stress in all tissues examined, Hsp 70 protein levels were more sustained. This study confirms the utility of rbcs as a biomarker tissue of thermal stress in fish and indicates that water temperatures presently being reached in brook trout habitats in Canada are capable of inducing a significant heat shock response in this species.
Energy allocation among developmental stages, age groups, and types of Atlantic salmon (Salmo salar) spawners
Authors: Jonsson Nina , Jonsson Bror
Published: June 2003

Relationships between energy density (kJ·100 g1) and body length (mm), which varied between life-history stages of Atlantic salmon (Salmo salar), were described by power functions. The variation was chiefly caused by differences in lipid concentrations. Energy densities of maturing and rematuring parr were higher than those of similarly aged smolts. Monthly specific growth rate was higher in maturing parr than in salmon at sea. Mature parr males allocated relatively more energy to gonadal development and less to soma development than anadromous males. Spawning expenditure increased from 34 to 53% for 55- to 72-cm-long females. In males, similar losses were from 47 to 49% of their total energy content at river entry. More energy was used in reproduction in a long river than in a short one. Male allocation to gonads relative to soma was highest in the shorter river. Energy allocation pattern varied among developmental stages. Very energy-rich male parr rematured in subsequent years without going to sea; less energy-rich ones smolted and migrated to sea.