bluuebunny/crossref_metadata_2025 huggingface dataset:
An assessment of shore‐based counts of gray whales
Authors: Rugh David J. , Muto Marcia M. , Hobbs Roderick C. , Lerczak James A.
Published: July 2008

Abstract

Counts of migrating whales depend on accurate sightings data. In this study, teams of shore‐based observers independently tracked whale pods during the southbound migration of gray whales (Eschrichtius robustus) while a routine (“standard watch”) census was underway. A comparison of sighting records showed that time and location accuracy was limited to 45 s, 3° (magnetic) horizontally, and 0.0057° (0.2 reticles) vertically. Of 242 attempts to track whale groups, 72 failed, 120 were “good tracks,” and 83 qualified as “best tracks” because they had ≥8 sightings/pod, ≥16‐min observation time, and unequivocal matches to sightings in the standard watch during uncompromised visibility. Between paired tracking teams, 39 attempts to conduct concurrent tracks resulted in 21 “good tracks” with complete agreement in 71% of the cases. Of 133 comparisons between trackers and the standard watch, 43% of the pod‐size estimates were the same, but the standard watch overestimated 10% of the pods and underestimated 47%. Thus, according to results from tracking teams, pods recorded as size 1 by observers on the standard watch should be corrected by +0.6; pods of 2 by +0.5; pods of 3 by +0.8; and pods >3 (4–10) were overestimated and should be corrected by −0.6.
Demographics and spatio‐temporal signature of the biotoxin domoic acid in California sea lion (Zalophus californianus) stranding records
Authors: Bejarano Adriana C. , Gulland Frances M. , Goldstein Tracey , St Leger Judy , Hunter Michele , Schwacke Lori H. , VanDolah Frances M. , Rowles Teri K.
Published: July 2008

Abstract

California sea lions (Zalophus californianus) in otherwise good nutritional condition have been consistently affected by the marine biotoxin domoic acid since the late 1990s. In this study we evaluated the temporal and spatial stranding patterns of suspected and confirmed cases of domoic acid intoxicated sea lions from 1998 to 2006, using records of strandings along the California coast obtained from members of the California Marine Mammal Stranding Network. The majority of domoic acid cases were adult females (47%–82% of the total annual domoic acid cases), a contrast to strandings that were not related to domoic acid, which were generally dominated by juveniles and pups. Exposure to this biotoxin led to a 6.67‐fold increase in adult female strandings in 2000, and a 5.44‐fold increase in adult female deaths in 2006, relative to strandings and deaths of adult female not affected by domoic acid. Domoic acid cases have occurred annually since 1998 (except for 1999) between April and August, with clusters centered primarily at Pismo Beach (San Luis Obispo County), as well as at other beaches in San Luis Obispo, Monterey, Santa Cruz, Santa Barbara, Orange, and San Diego counties. The larger ecological and population level implications of increased domoic acid strandings and deaths, particularly among adult female sea lions, warrant further attention and need to be investigated.
Differential Adaptive Response and Survival of
Salmonella enterica
Serovar Enteritidis Planktonic and Biofilm Cells Exposed to Benzalkonium Chloride
Authors: Mangalappalli-Illathu Anil K. , Vidović Sinisa , Korber Darren R.
Published: July 2008

This study examined the adaptive response and survival of planktonic and biofilm phenotypes of
Salmonella enterica
serovar Enteritidis adapted to benzalkonium chloride (BC). Planktonic cells and biofilms were continuously exposed to 1 μg ml
−1
of BC for 144 h. The proportion of BC-adapted biofilm cells able to survive a lethal BC treatment (30 μg ml
−1
) was significantly higher (4.6-fold) than that of BC-adapted planktonic cells. Similarly, there were 18.3-fold more survivors among the BC-adapted biofilm cells than among their nonadapted (i.e., without prior BC exposure) cell counterparts at the lethal BC concentration, and this value was significantly higher than the value for BC-adapted planktonic cells versus nonadapted cells (3.2-fold). A significantly higher (
P
< 0.05) proportion of surviving cells was noticed among BC-adapted biofilm cells relative to BC-adapted planktonic cells following a 10-min heat shock at 55°C. Fatty acid composition was significantly influenced by phenotype (planktonic cells or biofilm) and BC adaptation. Cell surface roughness of biofilm cells was also significantly greater (
P
< 0.05) than that of planktonic cells. Key proteins upregulated in BC-adapted planktonic and biofilm cells included CspA, TrxA, Tsf, YjgF, and a probable peroxidase, STY0440. Nine and 17 unique proteins were upregulated in BC-adapted planktonic and biofilm cells, respectively. These results suggest that enhanced biofilm-specific upregulation of 17 unique proteins, along with the increased expression of CspA, TrxA, Tsf, YjgF, and a probable peroxidase, phenotype-specific alterations in cell surface roughness, and a shift in fatty acid composition conferred enhanced survival to the BC-adapted biofilm cell population relative to their BC-adapted planktonic cell counterparts.
Peptide Nucleic Acid Fluorescent In Situ Hybridization for Hospital-Acquired Enterococcal Bacteremia: Delivering Earlier Effective Antimicrobial Therapy
Authors: Forrest Graeme N. , Roghmann Mary-Claire , Toombs Latoya S. , Johnson Jennifer K. , Weekes Elizabeth , Lincalis Durry P. , Venezia Richard A.
Published: July 2008

Hospital-acquired vancomycin-resistant enterococcal bacteremia has been associated with increased hospital costs, length of stay, and mortality. The peptide nucleic acid fluorescent in situ hybridization (PNA FISH) test forEnterococcus faecalisand other enterococci (EFOE) is a multicolor probe that differentiatesE. faecalisfrom other enterococcal species within 3 h directly from blood cultures demonstrating gram-positive cocci in pairs and chains (GPCPC). A quasiexperimental study was performed over two consecutive years beginning in 2005 that identified GPCPC by conventional microbiological methods, and in 2006 PNA FISH was added with a treatment algorithm developed by the antimicrobial team (AMT). The primary outcome assessed was the time from blood culture draw to the implementation of effective antimicrobial therapy before and after PNA FISH. The severity of illness, patient location, and empirical antimicrobial therapy were measured. A total of 224 patients with hospital-acquired enterococcal bacteremia were evaluated, with 129 in the preintervention period and 95 in the PNA FISH period. PNA FISH identifiedE. faecalis3 days earlier than conventional cultures (1.1 versus 4.1 days;P< 0.001). PNA FISH identifiedEnterococcus faeciuma median 2.3 days earlier (1.1 versus 3.4 days;P< 0.001) and was associated with statistically significant reductions in the time to initiating effective therapy (1.3 versus 3.1 days;P< 0.001) and decreased 30-day mortality (26% versus 45%;P= 0.04). The EFOE PNA FISH test in conjunction with an AMT treatment algorithm resulted in earlier initiation of appropriate empirical antimicrobial therapy for patients with hospital-acquiredE. faeciumbacteremia.
Molecular and Biochemical Characterization of SHV-56, a Novel Inhibitor-Resistant β-Lactamase fromKlebsiella pneumoniae
Authors: Dubois Véronique , Poirel Laurent , Demarthe François , Arpin Corinne , Coulange Laure , Minarini Luciene A. R. , Bezian Marie-Christine , Nordmann Patrice , Quentin Claudine
Published: July 2008

A clinical strain ofKlebsiella pneumoniaewas found to possess the chromosomal geneblaSHV-56, encoding a new inhibitor-resistant β-lactamase with a pI of 7.6. SHV-56 is derived from SHV-11 by the single substitution K234R. This mutation therefore evidences a new critical site for inhibitor resistance among SHV enzymes.
Genetic Structure Associated withblaOXA-18, Encoding a Clavulanic Acid-Inhibited Extended-Spectrum Oxacillinase
Authors: Naas Thierry , Namdari Fatemeh , Bogaerts Pierre , Huang Te-Din , Glupczynski Youri , Nordmann Patrice
Published: July 2008

The genetic environment of theblaOXA-18gene encoding a peculiar clavulanic acid-inhibitable Ambler class D extended-spectrum β-lactamase was determined from the prototype OXA-18-producingPseudomonas aeruginosaMUS clinical isolate. An 8.2-kb genomic DNA fragment containingblaOXA-18was cloned fromP. aeruginosaMUS. Although most oxacillinases are located in integrons,blaOXA-18lacked gene cassette-specific features. It was bracketed by two duplicated sequences containing ISCR19, a novel insertion sequence of the ISCRfamily of mobile elements; ΔintI1, a truncated integrase gene; and a truncated Δaac6′-Ibgene cassette. It is likely that ISCR19was at the origin of theblaOXA-18gene mobilization by a rolling-circle transposition event followed by homologous recombination. Furthermore, analysis of the cloned genomic DNA fragment revealed the presence of the integron-containingblaOXA-20gene. Concomitantly, threeP. aeruginosaclinical isolates, displaying a synergy image as determined by double-disk diffusion tests on cloxacillin-containing plates, were isolated from three patients hospitalized in different wards over a 9-month period at the Saint-Luc University hospital (Brussels, Belgium). These isolates were positive by PCR forblaOXA-18andblaOXA-20genes, genetically related toP. aeruginosaMUS as determined by pulsed-field gel electrophoresis, and carried the sameblaOXA-18/blaOXA-20-associated genetic structures. This report characterized the genetic elements likely at the origin ofblaOXA-18gene mobilization inP. aeruginosaand suggests the spread of oxacillin-type extended-spectrum β-lactamases inP. aeruginosaat the Saint-Luc University hospital of Brussels, Belgium.
Evolution of the IS
CR3
Group of IS
CR
Elements
Authors: Toleman Mark A. , Walsh Timothy R.
Published: July 2008

The IS
CR
elements IS
CR3
, IS
CR4
, IS
CR5
, IS
CR14
, and IS
CR16
all share a percent G+C of 68 to 69%. They also share between 75% and 97% identity in their transposase open reading frames. Furthermore, with the exception of IS
CR5
, they are all found adjacent to sections of
groEL
that display the highest identity to the same gene from
Xanthomonas
spp. The combined information is consistent with the descent from an ancestral IS
CR
element in a
Xanthomonas
-like organism.
Microbial Growth Inhibition by Alternating Electric Fields
Authors: Giladi Moshe , Porat Yaara , Blatt Alexandra , Wasserman Yoram , Kirson Eilon D. , Dekel Erez , Palti Yoram
Published: July 2008

Weak electric currents generated using conductive electrodes have been shown to increase the efficacy of antibiotics against bacterial biofilms, a phenomenon termed “the bioelectric effect.” The purposes of the present study were (i) to find out whether insulated electrodes that generate electric fields without “ohmic” electric currents, and thus are not associated with the formation of metal ions and free radicals, can inhibit the growth of planktonic bacteria and (ii) to define the parameters that are most effective against bacterial growth. The results obtained indicate that electric fields generated using insulated electrodes can inhibit the growth of planktonic
Staphylococcus aureus
and
Pseudomonas aeruginosa
and that the effect is amplitude and frequency dependent, with a maximum at 10 MHz. The combined effect of the electric field and chloramphenicol was found to be additive. Several possible mechanisms underlying the observed effect, as well as its potential clinical uses, are discussed.
Surveillance of Community-Based Reservoirs Reveals the Presence of CTX-M, Imported AmpC, and OXA-30 β-Lactamases in Urine Isolates of
Klebsiella pneumoniae
and
Escherichia coli
in a U.S. Community
Authors: Hanson Nancy D. , Moland Ellen Smith , Hong S. G. , Propst Katie , Novak Deborah J. , Cavalieri Stephen J.
Published: July 2008

β-Lactamases produced by urine isolates from patients in long-term care facilities (LTCFs), outpatient, clinics, and one hospital in a U.S. community were characterized. A total of 1.3% of all
Escherichia coli
and
Klebsiella pneumoniae
isolates collected from patients in 30 LTCFs and various outpatient clinics produced extended-spectrum β-lactamases (ESBLs) and/or imported AmpC β-lactamases.
Rχ-01, a New Family of Oxazolidinones That Overcome Ribosome-Based Linezolid Resistance
Authors: Skripkin Eugene , McConnell Timothy S. , DeVito Joseph , Lawrence Laura , Ippolito Joseph A. , Duffy Erin M. , Sutcliffe Joyce , Franceschi François
Published: July 2008

New and improved antibiotics are urgently needed to combat the ever-increasing number of multidrug-resistant bacteria. In this study, we characterized several members of a new oxazolidinone family, Rχ-01. This antibiotic family is distinguished by having in vitro and in vivo activity against hospital-acquired, as well as community-acquired, pathogens. We compared the 50S ribosome binding affinity of this family to that of the only marketed oxazolidinone antibiotic, linezolid, using chloramphenicol and puromycin competition binding assays. The competition assays demonstrated that several members of the Rχ-01 family displace, more effectively than linezolid, compounds known to bind to the ribosomal A site. We also monitored binding by assessing whether Rχ-01 compounds protect U2585 (Escherichia colinumbering), a nucleotide that influences peptide bond formation and peptide release, from chemical modification by carbodiimide. The Rχ-01 oxazolidinones were able to inhibit translation of ribosomes isolated from linezolid-resistantStaphylococcus aureusat submicromolar concentrations. This improved binding corresponds to greater antibacterial activity against linezolid-resistant enterococci. Consistent with their ribosomal A-site targeting and greater potency, the Rχ-01 compounds promote nonsense suppression and frameshifting to a greater extent than linezolid. Importantly, the gain in potency does not impact prokaryotic specificity as, like linezolid, the members of the Rχ-01 family show translation 50% inhibitory concentrations that are at least 100-fold higher for eukaryotic than for prokaryotic ribosomes. This new family of oxazolidinones distinguishes itself from linezolid by having greater intrinsic activity against linezolid-resistant isolates and may therefore offer clinicians an alternative to overcome linezolid resistance. A member of the Rχ-01 family of compounds is currently undergoing clinical trials.
Type I Interferon Signaling ExacerbatesChlamydia muridarumGenital Infection in a Murine Model
Authors: Nagarajan Uma M. , Prantner Daniel , Sikes James D. , Andrews Charles W. , Goodwin Anna M. , Nagarajan Shanmugam , Darville Toni
Published: July 2008

Type I interferons (IFNs) induced during in vitro chlamydial infection exert bactericidal and immunomodulatory functions. To determine the precise role of type I IFNs during in vivo chlamydial genital infection, we examined the course and outcome ofChlamydia muridarumgenital infection in mice genetically deficient in the receptor for type I IFNs (IFNAR−/−mice). A significant reduction in chlamydial shedding and duration of lower genital tract infection was observed in IFNAR−/−mice in comparison to the level of chlamydial shedding and duration of infection in wild-type (WT) mice. Furthermore, IFNAR−/−mice developed less chronic oviduct pathology in comparison to that in WT mice. Compared to the WT, IFNAR−/−mice had a greater number of chlamydial-specific T cells in their iliac lymph nodes 21 days postinfection. IFNAR−/−mice also exhibited earlier and enhanced CD4 T-cell recruitment to the cervical tissues, which was associated with increased expression of CXCL9 in the genital secretions of IFNAR−/−mice, but not with expression of CXCL10, which was reduced in the genital secretions of IFNAR−/−mice. These data suggest that type I IFNs exacerbateC. muridarumgenital infection through an inhibition of the chlamydial-specific CD4 T-cell response.
Life Table Evaluation of Chronic Exposure to a Pesticide
Authors: Daniels Richard E. , Allan J. David
Published: July 2008

The copepod Eurytemora affinis and the cladoceran Daphnia pulex were cultured at sublethal concentrations of dieldrin to test the usefulness of the intrinsic rate of population increase, r, as a bioassay statistic. The 48-h LC50 for E. affinis was 23 μg/L, but population growth rate measured by the life table method was only 12% of its control value at 5 μg/L and was zero at 10 μg/L, indicating a substantial sublethal effect. In contrast, D. pulex had a higher EC50 (251 μg/L) and showed little impairment of population growth potential below 220 μg/L. We suggest that the cladoceran was less sensitive than the copepod in both short- and long-term tests because of its simpler life cycle and larger size at hatching. The life table estimate of r appears to be an ecologically realistic measure of sublethal stress and requires an equivalent or shorter time to conduct than conventional long-term tests.Key words: acute toxicity, chronic toxicity, life table, r, toxic substances, Daphnia pulex, Eurytemora affinis, pesticide, dieldrin
Seasonal Particle-Size Selection by Diaptomus sicilis in Offshore Lake Michigan
Authors: Vanderploeg H. A.
Published: July 2008

Diaptomus sicilis feeding on offshore Lake Michigan seston exhibited a relatively invariant pattern of particle-size selection in 23 separate feeding experiments conducted from spring through fall over a 2-yr period. This pattern persisted for different feeding rates under varying conditions of particle-size spectrum shape, abundance and food quality of particles, and temperature. Selection was quantified by calculating W′ (filtering efficiency) as a function of particle size (equivalent spherical diameter). In all but one of the few experiments yielding a W′ curve that varied appreciably from the other W′ curves, serious bias from grazer-produced particles was evident and/or elongated particles dominated the seston. The elongated particles could have led to deviations because of differences in filtering efficiency between round and elongated particles of small volume and because elongated particles of large volume have to be captured raptorially. It is argued that the more variable patterns of particle-size selection observed in many of the other studies of zooplankton feeding on natural seston result from: (1) improper methods of quantifying selection, (2) serious bias from grazer-produced particles, and (3) varying particle shape, which is not usually specified. The mechanisms of particle selection by Diaptomus and other species that filter like Diaptomus are reviewed, and it is noted that invariant selection is not inconsistent with both filtering and raptorial modes of feeding operating simultaneously. All the evidence points to a strong passive-mechanical filtering mode of feeding that may be supplemented by a raptorial mode of feeding that selects large particles of high food quality.Key words: Diaptomus sicilis, particle-size selection, filter feeding, peak tracking, passive selection, Lake Michigan, food selectivity
Reduction, Methylation, and Incorporation of Arsenic into Lipids by the Marine Phytoplankton Dunaliella tertiolecta
Authors: Wrench J. J. , Addison R. F.
Published: July 2008

The metabolism of arsenate by the unicellular marine phytoplankton Dunaliella tertiolecta was studied using the isotope 74As. During a 45-min-exposure period the algal cells synthesized three polar arsenic metabolites which were identified as arsenite, monomethylarsonic acid, and dimethylarsinic acid. A large fraction of assimilated arsenic appeared in the lipid fraction and three arsenolipids could be separated by thin-layer chromatography. The turnover of dimethylarsinic acid and arsenolipids was rapid since all four metabolites reached equilibrium levels within the exposure period. Two of the arsenolipids were found to be labile in acid solution, and the primary acid hydrolysis product in both cases was identified as arsenite. One of these acid-labile arsenolipids behaved as an anionic compound on diethylaminoethyl cellulose ion-exchange columns and was also susceptible to hydrolysis by phospholipase D. A chromatographically identical compound could be synthesized from phosphadityl inositol and arsenite. The acid-labile anionic phosphatide produced by algae is therefore proposed to be a complex between arsenite and phosphadityl inositol.Key words: arsenic, arsenite, dimethylarsinic acid, phytoplankton, arsenolipids, phosphadityl inositol
Kinetic Properties of Digestive Carbohydrases and Proteases of Zooplankton
Authors: Mayzaud P. , Mayzaud O.
Published: July 2008

Copepod carbohydrases and proteases obtained from acetone-dried powder were tested for the effects of various physical–chemical factors. Influences of pH, temperature, substrate concentration, and time of incubation were studied to establish the optimal enzyme assay conditions. Enzyme activities were found that catabolyzed most sugars assayed (amylose, laminarin, cellulose, maltose, cellobiose, lactose, trehalose, α-mannoside, etc.) as well as those catabolyzing most proteins (hemoglobin, albumin, azocoll, cowhide azur). The spectrum of digestive enzymes found is discussed in terms of natural substrate availability. Certain enzymes, such as mannosidase or the chitobiases could be related to the bacterial component in the copepod intestinal flora or diet. From direct and indirect evidences it was possible partially to identify the amylase as an α-amylase, the acid protease as a cathepsin-like enzyme, and one of the alkaline proteases as a trypsin-like enzyme.Key words: kinetic properties, carbohydrases, proteases, zooplankton
Transmission of Bacterial Kidney Disease from Wild to Stocked Hatchery Trout
Authors: Mitchum Douglas L. , Sherman Loris E.
Published: July 2008

Natural, horizontal transmission of bacterial kidney disease (BKD) from infected wild brook trout (Salvelinus fontinalis) to newly stocked hatchery brook trout, brown trout (Salmo trutta), and rainbow trout (Salmo gairdneri) was shown in a small lake and stream system in southeastern Wyoming, USA. Stocked trout were infected naturally and died in 9 mo or less after exposure to infected wild fish. Dead and live fish collected from each of three stations were necropsied. Fluorescent antibody techniques (FAT) were used to detect the BKD organism in all samples. Low severity infections were often detected by FAT at a higher rate when feces were examined as compared to kidney tissues from the same fish. Because other known pathogens were essentially absent, BKD was diagnosed as the cause of all deaths in both stocked hatchery fish and wild fish. Rainbow trout were found to be the most refractory species.Key words: bacterial kidney disease, natural disease transmission, wild trout, brook trout, brown trout, rainbow trout, epizootics
Short-term Rearing of Pink Salmon (Oncorhynchus gorbuscha) Fry: Effect on Survival and Biomass of Returning Adults
Authors: Martin Roy M. , Heard William R. , Wertheimer Alex C.
Published: July 2008

Survival of pink salmon (Onchorynchus gorbuscha) fry could theoretically be improved if they were reared to a larger size before being released into the estuary. Three lots of 1975-brood pink salmon fry, reared from eggs in a hatchery, were cultured in floating estuarine raceways for 30, 60, and 90 d before being released into the Little Port Walter estuary on Baranof Island, southeastern Alaska. An unfed control lot was released after emergence. Four groups of 15 000 fry each were differentially fin marked. Total marine survival for the four lots was computed from recoveries of marked adults in the Little Port Walter vicinity in 1977. Survival from release to return was lowest for the control lot (3.1%); increased for fry reared for 30 and 60 d (4.6 and 5.2%, respectively); and decreased for fry cultured for 90 d (4.3%). Mortalities in lots cultured for 60 and 90 d significantly reduced the numbers of fry released in these groups. Mortalities were associated with the marine diatoms Chaetoceros spp. Mean length and weight of returning adults declined with increased fry-rearing time. Compared with the control lot, adults from fry cultured for 30 d had 39% more biomass; adults from fry cultured for 60 d had the same biomass; and adults from fry cultured for 90 d had 45% less biomass. Culturing fry for 30 d in the raceways significantly increased the number and biomass of returning adults.Key words: short-term rearing, Oncorhynchus gorbuscha, floating estuarine raceways, marine survival, biomass
Recreational Fisheries Analysis: Management Modes and Benefit Implications
Authors: Copes Parzival , Knetsch Jack L.
Published: July 2008

The analysis of recreational fisheries management is a relatively neglected area of research. In this paper we have attempted to advance that analysis by adapting certain theoretical considerations that have been used in (commercial) fisheries economics and in recreational economics. Specifically, we have considered the implications of the different modes of management that would be expected to prevail under the different management regimes of a public authority, a private owner, and a private club. We have also commented on the problems of integrating management in fisheries utilized for both commercial and recreational purposes and on measuring recreational fisheries benefits.Key words: recreational fishing, management, limitation of entry, common property resource, benefit cost measurement, rationalization, property rights
Evolution de la variabilité génétique inter et intra-populations de populations de Salmonidés issues de mêmes pools géniques
Authors: Guyomard R. , Grévisse C. , Oury F. X. , Davaine P.
Published: July 2008

Through electrophoretic analysis of 14 enzymatic systems corresponding to 31 loci, we studied the change over six generations in the intra- and inter-population variability of salmonid populations from the same initial genetic pool. Four collections of brook trout (Salvelinus fontinalis) and five of brown trout (Salmo trutta) from recently acclimatized stocks in the Kerguelen Islands were examined. The heterozygosity level of these populations remained high and corresponded to the levels of variability observed in other polymorphism studies of the same species. In each species, there was a consistent pattern of genetic differentiation with the "hydrographic proximity" of the populations and with the genetic origin. Within one and the same initial genetic pool, the dendrograms grouped primarily the different ecotypes collected in the same hydrographic system. Thus, these ecotypes seem to result from a behavioral variability within a panmictic population. Finally, establishment of time–genetic distance relationships on the sole basis of electrophoretic data appears unwarranted.
Restriction Endonuclease Analysis of Salmonid Mitochondrial DNA
Authors: Berg William J. , Ferris Stephen D.
Published: July 2008

We have analyzed the mitochondrial DNA from four species of the teleost subfamily Salmoninae using restriction endonucleases and found that the salmonid mitochondrial genome is slightly larger than that of the human, about 16 670 base pairs. Systematic analyses by both cladistic and phenetic methods suggest a closer phylogenetic relationship between Oncorhynchus tshawytscha and Salmo (Parasalmo) gairdneri than either has with Salmo (Salmo) trutta. Salvelinus fontinalis appears to be most distantly related of these four species. Applications of this molecular technique to a variety of genetic and population studies appear promising.
Spatial Distribution of Plankton in Enclosures of Three Sizes
Authors: Stephenson G. L. , Hamilton P. , Kaushik N. K. , Robinson J. B. , Solomon K. R.
Published: July 2008

The horizontal distribution of plankton was studied in large (1000 m3, 16 m diameter, 5 m deep), medium (5 × 5 × 5 m deep) and small (2 × 2 × 5 m deep) enclosures in a 10.3-ha mesotrophic lake in southern Ontario. Zooplankton population estimates from samples collected along distance gradients in the small and medium enclosures varied slightly but no consistent patterned distribution was present. However, the large enclosures possessed a distinctive edge zone that extended about 1.0 m from the walls. On two of the three sampling times there were significantly more macrozooplankton and/or fewer microzooplankton in the edge zone. However, on no occasion were there fewer macroplankton or more microzooplankton in the edge zone. Although macrozooplankton, as a group, may be significantly more numerous in the edge zone (P ≤ 0.05), individual species within this group exhibited both positive and negative responses. There was no defined edge zone in any enclosure with respect to phytoplankton density or biomass. Definition of the spatial distribution of organisms is essential to maximize precision of population estimates when using enclosure systems for ecotoxicological studies.
Timing of Spawning of Atlantic Herring (Clupea harengus harengus) Populations and the Match–Mismatch Theory
Authors: Sinclair M. , Tremblay M. J.
Published: July 2008

Each population of Atlantic herring (Clupea harengus harengus) has its own seasonally fixed spawning period of a few weeks duration, but the mean spawning times of different populations differ substantially. The extant theory explains the population-specific timing of spawning relative to the plankton production blooms in the inferred larval distributional area. Support of this theory is evaluated, and found lacking, in the light of a recent "stock" hypothesis involving larval retention. The new hypothesis involves two constraints. First, the larvae of a discrete herring population develop within, and are thus adapted to, the specific oceanographic conditions of their larval retention area. Second, metamorphosis from the larval to juvenile form occurs primarily within a restricted period of the year (April to October). Given these two constraints, it is hypothesized that the timing of spawning of a herring population is a function of the time necessary to complete the larval phase and yet metamorphose within the acceptable seasonal envelope. Populations that have "good" larval retention areas can spawn in the spring and still metamorphose within the seasonal envelope. Populations with larval retention areas that are less "good" for larval growth have to spawn earlier to satisfy the two constraints. The implications of the hypothesis on the "match–mismatch" theory are briefly discussed.
Homing and Straying in Chinook Salmon (Oncorhynchus tshawytscha) from Cowlitz River Hatchery, Washington
Authors: Quinn Thomas P. , Fresh Kurt
Published: July 2008

The patterns of homing and straying of spring chinook salmon (Oncorhynchus tshawytscha) from the Cowlitz River, Washington, were analyzed, based on coded wire tag recoveries. Out of an estimated escapement of 41 085 chinook salmon, 98.6% returned to Cowlitz River and the rest were recovered in other rivers. Almost all strays were within the Columbia River system, and most were found in the Lewis and Kalama rivers, upstream of Cowlitz River. Straying was positively correlated with age at return and negatively correlated with number of returning salmon.
Zooplankton Community Structure, but not Biomass, Influences the Phosphorus–Chlorophyll a Relationship
Authors: Pace Michael L.
Published: July 2008

Simultaneous observations were made of total phosphorus (TP), chlorophyll a (Chl a), and zooplankton biomass and community structure at 12 sites in the Eastern Townships (ET) region of Quebec to determine if zooplankton parameters reduced residual variation in the TP–Chl a relationship. Similar data from three stations in Lake Memphremagog and the literature were also analyzed. Zooplankton biomass was not significant in explaining residual variation in the TP–Chl a relationship of any data set studied. The mean body size of cladocerans was also not a significant additional variable in a TP–Chl a model based on the seasonal mean values in the ET lakes, but cladoceran body size was a significant factor in 13 lakes of the Indian River district of New York. The difference between these results is attributed to the rarity of large daphnids in the ET lakes. An index of zooplankton community structure derived from the slope of log abundance–log weight regressions was significant in explaining residual variation in TP–Chl a relationships for the among- and within-lake data and improved the predictive capability of TP–Chl a models. Lakes with higher concentrations of macrozooplankton relative to microzooplankton have less Chl a per unit TP. These results extend the generality of the hypothesis that large zooplankton differentially reduce Chl a relative to TP. In the ET lakes the effect of zooplankton size structure, however, was weak and this suggests that manipulation of zooplankton community structure to manage algal biomass may be of limited value in many lakes.
Early Life History of Redfish (Sebastes spp.) on Flemish Cap
Authors: Anderson John T.
Published: July 2008

Studies were carried out on Flemish Cap, 1978–82, to assess fish spawning cycles, the distribution, abundance, and growth of early life stages, and their relationship to environmental factors. Redfish larvae (Sebastes spp.) were the most abundant fish larvae found on Flemish Cap. Redfish began releasing larvae during March, reaching an abrupt peak in late April. Larval abundances of 733 larvae∙m2 were observed during the last week of April 1979, with highest sampled larval abundance for the study area being 6.8 × 1012 larvae. Redfish larvae first appeared in the southwest corner of Flemish Cap and within 3 wk were found in waters throughout the area over depths > 200 m. In July the survivors were concentrated over the Cap supporting the concept that Flemish Cap redfish constitute a distinct group. Larval growth for redfish was exponential through the periods sampled. However, in 1981, growth rate ranged from 0.40 to 1.66%∙d1. While larval growth was significantly correlated with average surface water temperature, high temperatures appeared to reduce larval growth. Slow growth during warm years appeared to be related to increased larval mortalities.
A Commentary on Environmental Impact Assessment for Large Projects Affecting Lakes and Streams
Authors: Larkin P. A.
Published: July 2008

In this essay I look at environmental impact assessment as it concerns major projects influencing aquatic environments in Canada. Environmental impact assessment is a process aimed at guarding the public interest in the proper use of resources in the aggregate. Compromises are usually worked out on a local basis for each project. More widely conceived trade-offs are favored by all but practised by few. All projects go through various stages, all begin as vague schemes; some crystallize as firm proposals and then go through the assessment process to construction and a subsequent period of operation. Environmental impact assessment as a process should reflect this pattern of activity rather than being just the preparation of statements about projects that are imminent. I have given particular emphasis to the need for follow up on whether what occurred was what was predicted. Also I have stressed the importance of anticipating that some impacts will not be foreseen and, therefore, the necessity for making appropriate financial provision. Environmental impact assessment, as presently practised, does not make the contribution it might to environmental science. Impact assessment should not be seen as a substitute for research that would lead to new understandings of ecological systems and to new appreciations of what to look for in making environmental impact assessments.
Impact of Harvesting on Irish Moss (Chondrus crispus Stackhouse) Frond Size-Class Structure
Authors: Pringle J. D. , Semple R. E.
Published: July 2008

Irish moss (Chondrus crispus Stackhouse) is cropped annually by dragrakes in certain southern Gulf of St. Lawrence Marine Plant Harvesting Districts (MPHD). Mean annual yield declined between 1972 and 1979, from peak years 1966–71, through a standing crop decrease. The present study compares frond size-class structure between three dragraked districts (light, moderate, and intense harvesting pressure) and two non-dragraked districts. Fronds, sampled by hand, were classified by pattern of dichotomy (branch) number; both mean frond weight and length were determined for each district. Frond size-class frequency distributions were bimodal from the moderate and intensely dragraked districts. Densities peaked at Classes 0 (no branching) and 5 or 6 (five or six branches), mean frond dry weights ranged from 0.09 g (intensely dragraked) to 0.18 g, mean frond length was between ~7 and ~10 cm, and mean frond dichotomy number was between ~3.6 and ~5.2. Frond size-class frequency distributions were unimodal from the non-dragraked and lightly dragraked districts, peaks were at Classes 6–8, mean frond dry weight per district was 0.40 g, mean frond length was between ~8 and ~12 cm, and mean frond dichotomy number was 7.5–8.2. The hypothesis that frond size-class frequency, mean frond dry weights, and mean frond dichotomy number were similar between intensely dragraked and non-dragraked beds was rejected. It was concluded that annual yield in the former beds would be substantially higher, were the mean frond size-class of the harvest increased by even one dichotomy. Frond length per class was not significantly different between intensely dragraked and non-dragraked beds. However, fronds higher than Class 6 from the former beds were heavier than those from the latter beds. These results are discussed in relation to dragrake selection pressure.
Production of Hexagenia limbata (Serville) and Ephemera simulans Walker (Ephemeroptera) in Dauphin Lake, Manitoba, with a Note on Weight Loss due to Preservatives
Authors: Heise Brian A. , Flannagan John F. , Galloway Terry D.
Published: July 2008

Annual production and biomass of Hexagenia limbata (Serville) and Ephemera simulans Walker were estimated from samples taken from May through September of 1982 and 1983 in Dauphin Lake, Manitoba. The size–frequency estimates (± 2 SE) of production for H. limbata were 12.6 ± 2.68 g/m2 (wet weight) in, 1982 and 10.1 ± 2.10 g/m2 in 1983. Instantaneous growth production estimates were 9.51 and 9.76 g/m21982) and 9.49 and 8.55 g/m2 (1983) based on life history interpretations of four versus seven cohorts, respectively. Elucidation of complex life histories involving overlapping cohorts may not be necessary in order to make accurate production estimates for similar semivoltine populations. Annual [Formula: see text] ratios for H. limbata ranged from 1.68 to 2.38. Production estimates for E. simulans in 1983 were 9.02 ± 3.10 and 9.90 g/m2, using the size–frequency and instantaneous growth methods, respectively. Hexagenia limbata weight loss due to preservation in 10% formalin followed by 75% ethanol resulted in a production underestimate of 25%. Length changes of H. limbata in the same preservatives were not significant (p > 0.05). Hexagenia limbata was found at all stations having a silt/clay component. Ephemera simulans was found only on a matrix substrate of clay, silt, sand and gravel.
Factors Influencing Egg Extrusion in the American Lobster (Homarus americanus)
Authors: Nelson K. , Hedgecock D. , Borgeson W.
Published: July 2008

American lobster (Homarus americanus) females characteristically extrude eggs in the summer of the year following a summer or autumn molt, but young females may extrude in the same year. Adult female lobsters were exposed to periods of 40, 80, or 120 d of short photophase (8 h light: 16 h dark) at different times during the molt cycle or as controls were kept under continuous long-day conditions (16 h light: 8 h dark). They were found to require 80 d of short photophase to complete primary vitellogenesis; they then completed secondary vitellogenesis and extruded following long day onset (LDO) only if the latter fell within ± 1400 dd6 (day-degrees above 6 °C) of the molt. The dependence of this latter relationship upon prior delayed extrusion and molting suggests that the decay in probability of LDO-elicited extrusion following the molt proceeds independently of the advance of the current molt cycle. The hypothesis is therefore rejected that the decay in extrusion potential following the molt is a result of increasing probability of interference from the oncoming premolt. Alternative hypotheses are discussed.
A Hydrophobic Large-Volume Sampler for Collecting Aquatic Surface Microlayers: Characterization and comparison with the Glass Plate Method
Authors: Hardy John T. , Coley James A. , Antrim Liam D. , Kiesser Steven L.
Published: July 2008

The atmosphere–water interface represents a vital biological habitat and a collection point for natural and anthropogenic materials originating in the atmosphere and the water column. A Teflon-coated aluminum rotating drum sampler was constructed and tested. This sampler rapidly collects large-volume samples of the aquatic surface microlayer uppermost 34 μm). The collection characteristics of the sampler are similar to those of the more time-consuming glass plate technique. Samples from estuarine, coastal, and offshore areas are generally highly enriched in selected organic compounds, metals, and microorganisms as compared with the subsurface bulk seawater. The sampler provides an efficient means of collecting hydrophobic pollutants from the water surface.
Estimating Total Fish Abundance and Total Habitat Area in Small Streams Based on Visual Estimation Methods
Authors: Hankin David G. , Reeves Gordon H.
Published: July 2008

We present sampling designs for estimating total areas of habitat types and total fish numbers in small streams. Designs are applied independently within strata constructed on the basis of habitat unit type and stream reach. Visual methods for estimating habitat areas and fish numbers are used to increase sample sizes and thereby reduce errors of estimation. Visual estimates of area are made for all habitat units, and visual estimates of fish numbers are made for systematic samples of units within given habitat types. Use of systematic sampling circumvents the requirement for a preexisting map of habitat unit locations and simplifies selection of units. We adjust for possible proportional bias of visual estimation methods by calibrating visual estimates against more accurate estimates made in subsamples of those units for which visual estimates are made. In a test application of these sampling designs, correlations between visual estimates and more accurate estimates were generally high, r > 0.90. Calculated 95% confidence bounds on errors of estimation were 13 and 16% for total areas of pools and riffles, respectively, and were 17 and 22% for total numbers of 1 + steelhead trout (Salmo gairdneri) and juvenile coho salmon (Oncorhynchus kisutch), respectively. Our methods appear to offer a cost-effective alternative to more traditional methods for estimating fish abundance in small streams. In addition, visual estimation surveys can produce detailed maps of the areas and locations of all stream habitat units.
Inseason Forecasting of Bristol Bay, Alaska, Sockeye Salmon (Oncorhynchus nerka) Abundance Using Bayesian Probability Theory
Authors: Fried Stephen M. , Hilborn Ray
Published: July 2008

A Bayesian probability model was developed for the Bristol Bay, Alaska, sockeye salmon (Oncorhynchus nerka) fishery to examine potential benefits of using a formal framework for incorporating several independent run size estimators into a single "best" estimate of total run size. To simulate performance of the technique, a hindcasting procedure was used for the years 1980–87. The Bayesian composite forecast was always more accurate than the least accurate individual forecast and was sometimes more accurate than the most accurate individual forecast. Since forecast accuracy for each independent method varied greatly both among and within years, the Bayesian method avoided the difficult problem of selecting the most accurate individual forecast and allowed forecasts to be easily revised each day of the season as new information became available. The documentation provided by our method should make it easier to evaluate and improve inseason run size estimation procedures and should allow for smoother transitions when management staff changes occur.
Density-Dependent, Trophic Level Responses to an Introduced Run of Sockeye Salmon (Oncorhynchus nerka) at Frazer Lake, Kodiak Island, Alaska
Authors: Kyle G. B. , Koenings J. P. , Barrett B. M.
Published: July 2008

Sockeye salmon (Oncorhynchus nerka) have developed into a major run at Frazer Lake, Kodiak Island, Alaska, reaching over 600 000 adults 34 yr after the first egg-plant in 1951. In the last nine years (1978–86), escapements have averaged over 250 000 with a record high of 486 000 adults in 1985. The increase in escapements were inversely related to seasonal macrozooplankton densities (p < 0.05; r2 = 0.42) but directly correlated with increases in the cladoceran to copepod ratio (p < 0.001). In addition, the average body length of the smallest macrozooplanker (Bosmina) has shifted below the observed threshold length of 0.40 mm for juvenile sockeye prey. We also found an inverse relationship between greater parental escapements and age 1. smolt length (p < 0.01; r2 = 0.75). Small-sized smolts produced from a density-dependent rearing environment indicate that spawning capacity equals or exceeds rearing capacity. Juvenile recruits from larger escapements (~400 000) exerted a controlling, density-dependent influence on the secondary trophic level which drastically reduced subsequent adult returns. Moreover, adverse trophic level changes, particularly after the largest escapements, also appeared to reduce the rearing efficiency for lower densities of juveniles, as subsequent smolt sizes from smaller escapements were less than expected. Thus, these findings not only provide a rationale for suggesting that fewer spawners would provide recruits more closely matching the rearing capacity of this lake, but also provide empirical evidence for the potential adverse density-dependent effects of large escapements.
Planktonic Growth of Larval Lobster (Homarus americanus) off îles de la Madeleine (Quebec), Gulf of St. Lawrence
Authors: Hudon Christiane , Fradette Pierre
Published: July 2008

The carapace length of the three planktonic larval and one postlarval stages of Homarus americanus was measured for larvae collected off îles de la Madeleine over three summers. Mean larval size did not vary between years or locations around the islands. The size of stages I and II remained constant throughout the summer, but after molting into stages III and IV, larvae diminished in size through the summer. Size frequency distribution became more scattered as larvae grew into more advanced stages. The increase of variance with size between stages I–IV followed the same progression as that observed between stages V–XIII, allowing prediction of the variance associated with mean size at each stage. The size of stage I larvae collected in nine regions along the Atlantic coast was not correlated with the July surface water temperature or with the smallest female size at maturity. Comparison of various body proportions suggested that a single morphometric measurement is not sufficient to describe geographical variations in size. Percentage growth per molt decreased with each successive molt. During summer, increment at molt decreased and molt frequency increased. Larval growth rates followed closely the temperature regime, with maximum growth rate attained during the warmest period of the summer (July 30 – August 9). The duration of the first three larval stages estimated from field data was of 24 d compared with 21 d calculated from previous laboratory studies. The maximum abundance of stage I larvae was synchronized with the period of most rapid increase in summer temperature, thus insuring that larvae achieved highest net growth rates through their planktonic phase.