bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Escape Modifications in Traps for Prawn, Pandalus platyceros
Authors: Boutillier J. A. , Sloan N. A.
Published: May 2008

Experimental fishing was done in 1986 to evaluate variables considered important in developing escape modifications for the prawn, Pandalus platyceros, trap fishery in British Columbia. Three major trap categories were used: flexible nylon mesh, rigid wire mesh, and solid sided. The efficacy of escape modifications depended upon the size of openings, the type of construction material, the placement of the modification on the trap, and soak time. The 44-mm web and wire material used for modifications allowed for escapement of prawns well above the 30.0-mm carapace length legal size limit. The rigid wire mesh used in escape modifications retained smaller prawns than did similar-sized flexible nylon mesh. In partially modified traps, escape material on the side/bottom combination was more effective for escapement than when just on the bottom or in the tunnels of the trap. Soak time was important in some traps which had escape material in ineffective locations. In these cases, longer soak times allowed the small prawns time to find their way out of the traps.
Effects of Biomass–Range Interactions on Catchability of Migratory Demersal Fish by Mobile Fisheries: An Example of Atlantic Cod (Gadus morhua)
Authors: Rose G. A. , Leggett W. C.
Published: May 2008

We used daily acoustic estimates of the abundance and range of a migratory demersal species, Atlantic cod (Gadus morhua), coupled with catch statistics from a mobile gillnet fishery in the northern Gulf of St. Lawrence, to verify two predictions of the Paloheimo–Dickie hypothesis: (1) that biomass and range of fish distributions are positive covariates and (2) that catchability (q) is negatively correlated with biomass and occupied range. Fishing power changed little during this study (1985–86) and was thus not a major cause of variation in q. The daily biomass (b) of cod surveyed on the fishing ground was significantly and positively correlated with the range occupied (a) in both 1985 and 1986 (b = 86a1.05; R2 = 0.71; P < 0.05). Local cod densities assessed at small scales (1 km) were relatively stable. Daily catchability was a negative multiplicative function of both biomass (q = 0.095b−0.787; R2 = 0.70; P < 0.05) and occupied range (q = 0.003a−0.747; R2 = 0.56; P < 0.05). The q–range relationship derived in 1986 was used to hindcast q in 1985. Hindcast and observed 1985 q's were significantly correlated (r = 0.74; P < 0.05).
Interactions between Two Distantly Related Species, Brook Trout (Salvelinus fontinalis) and White Sucker (Catostomus commersoni)
Authors: Tremblay Serge , Magnan Pierre
Published: May 2008

We compared spatial distribution and food habits of an allopatric brook trout (Salvelinus fontinalis) population to one living sympatrically with white sucker (Catostomus commersoni) in two small oligotrophic lakes. Small brook trout (< 20 cm) of both sympatric and allopatric populations were more abundant in the littoral than in the offshore zone whereas large [Formula: see text] were found equally in both habitats in May. From June to August, small and large trout from both populations shifted to the offshore zone; this shift was more pronounced for small sympatric trout. Allopatric trout fed mainly on zoobenthos whereas sympatric trout fed mainly on zooplankton except small ones which ate mostly zoobenthos during May and June. White sucker (< 20 and [Formula: see text]) were generally found in the littoral zone, feeding mainly on zoobenthos. These results suggest that brook trout shifted their spatial distribution and/or their feeding habits in the presence of white sucker and that the nature of these interactions varied according to fish size. Diet overlap between trout and sucker was the lowest when the biomass of benthic prey in the littoral zone was lowest (July), indicating that the intensity of interaction among these species varies according to the abundance of food resources.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Toxicity during Early Life Stage Development of Lake Trout (Salvelinus namaycush)
Authors: Walker Mary K. , Spitsbergen Jan M. , Olson James R. , Peterson Richard E.
Published: May 2008

Lake trout (Salvelinus namaycush) eggs containing [3H]TCDD concentrations from 0 to 302 parts per trillion (ppt) were observed through the fry stage for TCDD metabolism, elimination, and toxicity. All radioactive residues extracted from eggs and sac fry were due to TCDD; no metabolites were detected. [3H]TCDD was not eliminated from eggs and sac fry, but was rapidly eliminated from fry (t1/2, 35–37 d). Hatchability was less at egg TCDD concentrations [Formula: see text]; however, the greatest TCDD-related mortality occurred during the sac fry stage. In all TCDD groups (34–302 ppt), sac fry that died developed subcutaneous yolk sac edema prior to death, resembling blue-sac disease. The development of yolk sac edema preceded sac fry mortality, and the severity of edema varied directly with cumulative mortality. Based on TCDD concentrations in the egg resulting from a 48-h exposure, the no observable adverse effect level (NOAEL) for mortality was 34 ppt and the lowest observable adverse effect level (LOAEL) was 55 ppt. The TCDD concentration in eggs that caused 50% mortality above control at swim-up (LD50) was 65 ppt. Lake trout sac fry exposed as eggs are more sensitive to the lethal effects of TCDD than any mammalian, avian, or fish species investigated thus far.
Predation and Production by Salmonine Fishes in Lake Michigan, 1978–88
Authors: Stewart Donald J. , Ibarra Myriam
Published: May 2008

A marked decline of alewife (Alosa pseudoharengus) in Lake Michigan during 1981–83 led to diet shifts by coho (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) from feeding primarily on large alewife to eating proportionately more immature alewives and other prey. Diets of lake trout (Salvelinus namaycush) did not change greatly during that period. Population biomass conversion efficiency averaged 24.5% for coho and 16.6% for lake trout. Chinook salmon suffered an apparent 20% decline in gross conversion efficiency of biomass (25.1 to 20.8%) and a 25% decline in average weight of sport-caught fish. We infer that chinook salmon growth was inhibited by insufficient forage available to them. A simulation of chinook salmon feeding on bloater (Coregonus hoyi) at 8 °C suggested that such behavior could lead to further declines in growth rates. Extension of modeling results to include approximations for brown trout (Salmo trutta) and rainbow trout (O. mykiss) revealed peaks in total annual salmonine predation of 71 000 t in 1983 and 76 000 t in 1987. The alewife was 70% of all prey eaten by salmonines in 1987–88. Lakewide gross production by salmonines was 15 300 t (or 0.27 g∙m−2) in 1987. Ratios of annual gross production to average monthly population biomass were 1.6 for chinook, 1.15 for coho, and only 0.6 for lake trout.
Genetic Effects of Cultured Fish on Natural Fish Populations
Authors: Hindar Kjetil , Ryman Nils , Utter Fred
Published: May 2008

This paper addresses the genetic consequences of aquaculture on natural fish populations. The study is motivated by rapidly increasing numbers of intentionally and accidentally released fish and is based on empirical observations reported in the literature. A wide variety of outcomes, ranging from no detectable effect to complete introgression or displacement, has been observed following releases of cultured fish into natural settings. Where genetic effects on performance traits have been documented, they always appear to be negative in comparison with the unaffected native populations. These findings are consistent with theoretical considerations of the implications of elevated levels of gene flow between cultured and locally adapted natural populations; they raise concerns over the genetic future of many natural populations in the light of increasing numbers of released fish. Strategies for the genetic protection of native populations from the effects of aquaculture are outlined including more secure containment, the use of sterilized fish, and modifying the points of rearing and release. We recommend strong restrictions on gene flow from cultured to wild populations and effective monitoring of such gene flow.
The Coupling of Heterotrophic Bacterial and Phytoplankton Production in a Hypertrophic, Shallow Prairie Lake
Authors: Robarts Richard D. , Arts Michael T. , Evans Marlene S. , Waiser Marley J.
Published: May 2008

Data from hypertrophic Humboldt Lake (Zmax = 6 m), Saskatchewan, support published studies indicating that bacterial numbers and production do not increase proportionally with chlorophyll concentration and primary production. There was no compensation for these relationships with increased bacterial production per cell, but our data showed an increase in production per unit bacterial biomass (273 fmol TdR∙μg C−1∙h−1). Bacterial production (19.8–422 mg C∙m−2∙d−1) was correlated with primary production (r = 0.76), and maximum bacterial production coincided with summer cyanobacterial blooms. Water temperature was a dominant factor correlated with bacterial production (r = 0.85) and growth (r = 0.92). Depending upon the factors used to convert the rate of thymidine incorporation to gross carbon production, heterotrophic bacterial production was able to consume an average of 42% (408 mg C∙m−2∙d−1) to 67% (653 mg C∙m−2∙d−1) of plankton primary productivity. Based on these calculations, hypertrophic prairie lakes might accumulate autochthonously produced organic carbon, but this conclusion takes no account of benthic bacterial production which could be high in shallow lakes.
Dramatic Decline of Unionid Bivalves in Offshore Waters of Western Lake Erie After Infestation by the Zebra Mussel, Dreissena polymorpha
Authors: Schloesser Don W. , Nalepa Thomas F.
Published: May 2008

Unionid bivalves and attached epizoic zebra mussels (Dreissena polymorpha) were collected at one index station in 1989, 1990, and 1991 and at 17 stations in 1991 in offshore waters of western Lake Erie of the Laurentian Great Lakes. Sampling at the index station revealed that the proportion of live unionids declined from 53% in September 1989 to 17% in May–June 1990 and to 0% in September 1990: this 100% mortality coincided with heavy infestation by zebra mussels. Quantitative sampling with a Ponar grab at the 17 stations in 1991 revealed a widespread and dramatic reduction in unionid populations. In 1982, five unionid species occurred at 35% of the stations at a density of 4/m2, whereas in 1991, no live unionid species were found. Qualitative sampling with an epibenthic sled at the 17 stations in 1991 yielded only 4 live specimens of 2 species (Amblema plicata plicata and Fusconaia flava) and 187 dead specimens of 10 species. These and other results indicate that unionid populations are being negatively affected by zebra mussels in the Great Lakes. Similar impacts on unionids are expected to occur where zebra mussels become abundant throughout North America.
Recent Changes of N2-Fixation in Lake 227 in Response to Reduction of the N:P Loading Ratio
Authors: Hendzel L. L. , Hecky R. E. , Findlay D. L.
Published: May 2008

Continuous artificial additions of nitrogen (N) and phosphorus (P) to Lake 227 at a loading ratio of 11:1 (atom: atom; 5:1 by mass) from 1975 to 1989, combined with natural inputs, resulted in variable mean annual total N and total P concentrations and changes in phytoplankton species composition. Summer phytoplankton occasionally shifted from N2-fixing cyanobacteria to non-N2-fixing forms. In 1990, additions of N fertilizer were stopped in order to test the hypothesis that low N:P loading rates cause selection for heterocystous cyanobacteria and stimulate N2-fixation. Five years of phytoplankton nutrient-status measurements, together with estimates of N2-fixation before and after lowering the N:P loading ratio, verified the importance of this ratio in producing blooms of N2-fixing cyanobacteria. Nitrogen input via biological N2fixation increased, and summer dominance by heterocystous cyanobacteria returned as a consequence of lowering the N:P ratio of external inputs. Seasonally, N return from the epilimnetic sediments increased after a period of high planktonic N2-fixation rates. This regenerated N reduced the abundance of heterocystous cyanobacteria and lowered late summer N2-fixation rates. Over several years, preferential regeneration of N relative to P maintained the N:P ratio of the internally cycling nutrient pool, despite the reduction in the external N:P loading ratio.
Aphanizomenon schindleri sp.nov.: a new nostocacean cyanoprokaryote from the Experimental Lakes Area, northwestern Ontario
Authors: Kling Hedy J. , Findlay David L. , Komárek Jiri
Published: May 2008

Aphanizomenon schindleri sp.nov., a new nostocacean, bluegreen, cyanoprokaryote (cyanobacterium), is described from artificially eutrophied Canadian Shield lakes in the Experimental Lakes Area, northwestern Ontario. It is unique to low conductivity Canadian Shield waters to which nutrients have been added, and it became the dominant bloom species after years of phosphorus (P) and nitrogen (N) loading followed by N limitation (N:P ≤ 5:1 by mass) (Findlay et al. 1994. Can. J. Fish. Aquat. Sci. 51: 2254–2266). The new Aphanizomenon species appears to be most closely related to A. gracile but also resembles species of Anabaena with straight filaments. It differs from other species of Aphanizomenon in cell dimensions, length and width of akinetes and heterocytes, and in akinete and end cell shape.
Comparison of Fossil Pigments with 20 Years of Phytoplankton Data from Eutrophic Lake 227, Experimental Lakes Area, Ontario
Authors: Leavitt P. R. , Findlay D. L.
Published: May 2008

Fossil pigments from annually laminated sediments were calibrated with coeval phytoplankton data (1970–1989) from experimentally eutrophied Lake 227 in the Experimental Lakes Area, Ontario. Concentrations of ubiquitous pigments (β-carotene, pheophytin a) were correlated to total algal biomass standing crop (r = 0.56–0.65; P < 0.01) during the ice-free seasons, but not to carbon fixation or water-column chlorophyll (Chl). Indicator pigments were correlated to ice-free season algal biomass for cyanobacteria (echinenone, aphanizophyll) and chlorophytes (lutein–zeaxanthin, pheophytin b)(r = 0.53–0.55, P < 0.05), weakly correlated for cryptophytes (alloxanthin, α-carotene; r = 0.32–0.40, P < 0.10), but were uncorrelated for chrysophytes and diatoms (fucoxanthin, Chl c) or dinoflagellates (peredinin). Premanipulation concentrations of fossil pigments (nmol pigment∙(g organic matter)−1) from green algae and filamentous cyanobacteria (myxoxanthophyll) increased 4- to 10-fold in response to eutrophication of Lake 227. N2-fixing cyanobacteria (recorded as aphanizophyll) replaced chlorophytes after the nitrogen additions decreased threefold in 1975. In contrast, accumulation rates of pigments (nmol pigment∙rrr−2∙yr−1) were rarely correlated with algal standing crop or production and were less satisfactory than fossil concentrations for the purpose of detecting changes in phytoplankton community composition.
Paleolimnological analysis of whole-lake experiments: an overview of results from Experimental Lakes Area Lake 227
Authors: Leavitt P. R. , Hann B. J. , Smol J. P. , Zeeb B. A. , Christie C. E. , Wolfe B. , Kling H. J.
Published: May 2008

High resolution analysis of laminated sediments from experimentally fertilized Lake 227 was used to compare sediment geochemistry and fossil abundance (siliceous algae, pigments, cladoceran remains) with 20 yr (1969–1989) of continuous historical records. Members of all fossil groups were correlated to the biomass of their respective producer populations (r = 0.52–0.66, P < 0.05, n = 20). Correlations were greatest when fossil abundance was expressed per unit organic matter and least when calculated as the accumulation rate. Comparison of groups showed that fossils of soft-bodied zooplankton (copepods, rotifers) and pigments from dinoflagellates were completely unreliable. The most informative fossils were chitinous remains of zooplankton (e.g., Bosmina), remains of siliceous algae, and pigments from chlorophytes and cyanobacteria. Ecosystem-level paleolimnology showed that fertilization was the most significant eutrophication event in the last 400 yr and that it impacted both pelagic and littoral communities. However, fossil zooplankton and pigment analyses indicated that food-web interactions (zooplanktivory, herbivory) also regulated plankton abundance and composition. Additionally, fossil analyses showed that some natural eutrophication occurred prior to 1969 and that plankton communities have continued to vary since 1975, despite constant rates of fertilization with nitrogen and phosphorus.
Local Fisheries Co-management: A Review of International Experiences and Their Implications for Salmon Management in British Columbia
Authors: Pinkerton Evelyn W.
Published: May 2008

The theory and practice of community-based self-management and government–community co-management is examined in terms of the potential of these management systems to address some of the major biological, economic, and political problems of the salmon fishery of British Columbia, Canada. Particular attention is given to government–multiparty arrangements that integrate the concerns of multiple interests, while recognizing the special rights of aboriginal communities. Elements identified as key to the success of various arrangements include: (1) logistical arrangements, such as clear boundaries, membership criteria, interception agreements, and management-unit sizes appropriate to the abundance of natural and human resources; (2) cost-sharing arrangements, such as local cost recovery and local volunteerism; (3) power-sharing arrangements through checks and balances between local multiparty boards, a provincial board, and the Department of Fisheries and Oceans. The processes engendering social learning, through which government and local bodies could move toward such regimes, are discussed through a review of relevant literature on interorganizational conflict resolution, public policy, and organizational learning. Many of the elements of success of both arrangements and processes are likely to apply to a broad range of fisheries co-management situations.
Genetic Diversity Patterns of Chum Salmon in the Pacific Northwest
Authors: Phelps S. R. , LeClair L. L. , Young S. , Blankenship H. L.
Published: May 2008

We used starch-gel electrophoresis to examine over 13 000 adult chum salmon, Oncorhynchus keta, from 153 collections at 105 locations in Washington, Oregon, and southern British Columbia from 1985–92. We identified 39 variable loci and 36 monomorphic loci. In general, alleles that occurred at a frequency > 10% were found in all locations and were temporally stable within locations. Localized alleles usually occurred at a frequency <6%. Significant allele frequency differences were found among chum salmon populations with different spawning times (summer, fall, and winter), even within the same watershed, and among populations of the same spawning time in different regions. Significant among-population diversity was also found within regions. Multidimensional scaling and UPGMA cluster analysis grouped populations by geography and run-timing, except where past stock transfers have resulted in interbreeding of hatchery and wild fish. These analyses indicate that both geography and spawning time are important isolating mechanisms and that, compared with the other populations, summer-run chum salmon from the Strait of Juan de Fuca and Hood Canal are a distinct evolutionary lineage. This information is currently being used to conserve the genetic diversity of wild chum salmon and manage mixed-stock fisheries.
Genetic Stock Structure of Western Alaska Chum Salmon and a Comparison with Russian Far East Stocks
Authors: Wilmot Richard L. , Everett Rebecca J. , Spearman William J. , Baccus Ramone , Varnavskaya Natalya V. , Putivkin S.V.
Published: May 2008

Substantial genetic divergence was found among chum salmon (Oncorhynchus keta) populations collected from North America and Russia. Five major groups of populations can be identified by geographic region: (1) lower Yukon River summer run; (2) upper Yukon River fall run; (3) Bristol Bay area; (4) Alaska Peninsula; and (5) Russia. Mean heterozygosities were 0.064, 0.062, 0.065, 0.064, and 0.063, respectively; and the percent polymorphic loci values at the 0.99 level were 33.7, 31.3, 32.6, 30.6, and 30.9%, respectively. The hierarchical gene diversity analysis showed that 95.42% of the diversity can be explained by heterogeneity within sites, 1.36% among sites, 0.49% between Yukon River run timing, 1.69% among areas, and 1.04% among countries. The Alaska Peninsula populations are genetically more similar to populations from Russia than to those from western Alaska, and two populations from the upper Yukon River are distinct from other nearby populations. Possible reasons for these findings concern the complex glacial histories of the watersheds.
Population Structure of Eastern Oysters (Crassostrea virginica) Inhabiting the Laguna Madre, Texas, and Adjacent Bay Systems
Authors: King Tim L. , Ward Rocky , Zimmerman Earl G.
Published: May 2008

A survey of 16 enzyme systems and two structural proteins, among nine eastern oyster (Crassostrea virginica) populations in and adjacent to Laguna Madre, Texas, identified two genetically differentiated groups and the transition zone between them. The discontinuity in allele frequencies occurred between a reef in Corpus Christi Bay and reefs 26 km away in upper Laguna Madre. Although no fixed allelic differences were observed between populations from either side of the transition area, substantial frequency differences were observed at six gene loci, and both groups exhibited unique alleles. Spatial heterogeneity tests also suggested sizable allele frequency differences, as 8 of 15 polymorphic loci surveyed exhibited heterogeneity. Considerable genetic subdivision was observed, as 14 of 15 polymorphic loci surveyed exhibited significant fixation indices. The mean genetic similarity was 0.898 (range 0.813–0.977). Consequently, oysters inhabiting the Laguna Madre are genetically divergent from oysters inhabiting central and eastern Texas, the north-central and eastern Gulf of Mexico, and the western Atlantic coast. Thus, these groups should be considered as discrete management units, and the patterns of genetic exchange investigated. If eastern oysters inhabiting the Laguna Madre, Texas, are unique, they warrant protection.
Gene Differentiation in Pacific Salmon (Oncorhynchussp.): Facts and Models with Reference to Pink Salmon (O.gorbuscha)
Authors: Zhivotovsky Lev A. , Gharrett A. J. , McGregor A. J. , Glubokovsky M. K. , Feldman Marcus W.
Published: May 2008

Analyzing population genetic data usually involves examining relationships among populations followed by analysis of the distribution of genetic variability. Genetic relationships are often depicted with multidimensional scaling or trees constructed from genetic distances; genetic variation within and among populations is partitioned using gene diversity measures such as FSTor GST. Genetic distances or gene diversity are often used to estimate influences of gene drift, migration, and/or selection on observed gene differentiation. We used allozyme data for pink salmon populations to examine the theoretical models available for estimating magnitudes of these factors in Pacific salmon populations. The models included (1) mutation and gene drift; (2) mutation and migration; (3) migration and gene drift; and (4) gene drift, migration, and selection. These models suggest that gene drift and migration are probably important at the lowest levels of population hierarchy, but even very small forces such as weak heterogeneous selection and low migration levels may be important at higher levels. The accuracy of some estimates should be questioned because for many situations appropriate models are either not yet available or are not sufficiently refined. Also, the dynamic genetic structure of salmon populations makes it unlikely that the steady state assumed for many theoretical models has obtained.
Life-History Organization of Yellowstone Cutthroat trout (Oncorhynchus clarki bouvieri) in Yellowstone Lake
Authors: Gresswell Robert E. , Liss William J. , Larson Gary L.
Published: May 2008

Life-history organization of the cutthroat trout (Oncorhynchus clarki) may be viewed at various levels, including species, subspecies, metapopulation, population, or individual. Each level varies in spatial scale and temporal persistence, and components at each level continually change with changes in environment. Cutthroat trout are widely distributed throughout the western United States, occurring in such diverse environments as coastal rivers of the Pacific Northwest and interior streams of the Great Basin. During its evolution the species has organized into 14 subspecies with many different life-history characteristics and habitat requirements. Within subspecies, organization is equally complex. For example, life-history traits, such as average size and age, migration strategy, and migration timing, vary among individual spawning populations of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) in tributary streams of Yellowstone Lake. Understanding the effects of human perturbations on life-history organization is critical for management of the cutthroat trout and other polytypic salmonid species. Loss of diversity at any hierarchical level jeopardizes the long-term ability of the species to adapt to changing environments, and it may also lead to increased fluctuations in abundance and yield and increase the risk of extinction.
Determining the most efficient method of age determination for estimating the age structure of a fish population
Authors: Worthington D. G. , Fowler A. J. , Doherty P. J.
Published: May 2008

Less precise, but economic methods for estimating the age of individual fish can provide better estimates of age structure than precise, but expensive methods. The benefits of using a precise ageing method can be compromised by its cost, which may restrict the size of the sample aged. If sample size is restricted, the effect of sampling error on an age structure may be greater than the effect of ageing error from a less precise ageing method that does not restrict sample size. We used Monte Carlo simulations to assess the relative size of sampling and ageing errors when estimating the age structure of populations of Pomacentrus moluccensis from the southern Great Barrier Reef, Australia. Sampling error associated with ageing less than 200 individuals was, on average, larger than the effects of most commonly reported ageing errors. Other factors that may complicate this comparison of ageing methods involve the financial cost of different methods and the logistics of sampling more fish.
Accumulation of trace metals (Cd, Pb, Cu, Zn) in Arctic char (Salvelinus alpinus) from oligotrophic Alpine lakes: relation to alkalinity
Authors: Köck G. , Hofer R. , Wögrath S.
Published: May 2008

We studied Arctic char (Salvelinus alpinus) from five oligotrophic Alpine lakes in northern Tyrol, Austria, that differed in altitude (929–2796 m above sea level), pH (pH 5.4–8.3), and alkalinity (1.3–2750 μequiv.∙L−1). Concentrations of Cd, Pb, Zn, and Cu were measured in the water and in the kidney of fish, allowing the calculation of metal bioconcentration factors between water and fish kidney. Despite relatively low Cd and Pb concentrations in the water (Cd, 0.1 μg∙L−1; Pb, 0.5 μg∙L−1, dissolved), metal concentrations in the kidneys of fish from the most acidic lake (Cd, 123 μg∙g−1; Pb, 19 μg∙g−1, dry weight) were comparable with those of fish from waters polluted by direct discharge of metals. Concentrations of Cd and Pb in the kidney were negatively correlated with the alkalinity of the lakes. Comparison with data from other studies confirms the predictive utility of water alkalinity for estimating Cd accumulation in fish from oligotrophic lakes. The correlation between bioconcentration factors and alkalinity was negative for Cd and Pb, positive for Zn, and nonsignificant for Cu.
Effect of foraging activity on the shoal structure of cod (Gadus morhua)
Authors: DeBlois E. M. , Rose G. A.
Published: May 2008

Acoustic methods used to quantify the shoaling dynamics of Atlantic cod (Gadus morhua) during their shoreward migration across the northeast Newfoundland shelf (spring 1992) showed that shoal structure and horizontal displacement were associated with the density distribution of small pelagic scatterers, for example, shrimp (Pandalus borealis). Cod speeds (to 20 km/d) were lower after encounters with shrimp (4–7 km/d). The relationship between several characteristics of the cod shoal (density, vertical spread, height off the bottom) and shrimp density was dome shaped. Internal shoal densities declined and shoal spread and height increased until shrimp densities surpassed a critical level. Above this threshold, these trends were reversed. The vertical spread of the cod shoal matched that of shrimp up to, but not beyond, a shrimp spread of 85 m. At this observed maximum in the expansion of the shoal, fish were eight body lengths apart. At all times during our survey, cod stayed within the warmer waters (> 2 °C) found at depths greater than 250 m. Our results are the first field verification of theoretical predictions and laboratory findings that shoals expand and contract in response to foraging activity and demonstrate the potential importance of cod aggregation dynamics to interpretations of trawl data.
Postsettlement eutrophication histories of six British Columbia (Canada) lakes
Authors: Reavie Euan D. , Smol John P. , Carmichael N. Bruce
Published: May 2008

Eutrophication is a serious problem in many British Columbia lakes. However, long-term nutrient data are rare or unavailable for most lake systems, so the natural, predisturbance characteristics of lakes are unknown, as are the trajectories of past environmental change. We used paleolimnological analyses of diatoms to quantitatively assess eutrophication trends for approximately the last 150 years in six British Columbia lakes. A transfer function was used to infer past lake-water total phosphorus concentrations from the sedimentary diatom assemblages in210Pb-dated sediment cores: all of the lakes had relatively high total phosphorus levels (> 13 μg/L) prior to European settlement. Three of the lakes showed significant eutrophication since that time, whereas the others were only mildly affected. Total phosphorus inferences using the transfer function satisfactorily estimated the modern total phosphorus concentrations of our six study lakes. Minor quantitative problems arose when some fossil assemblages provided poor analogues to the calibration function, but eutrophication trends were still clearly apparent. Our results confirm that some British Columbia lakes have suffered considerable eutrophication as a result of anthropogenically related nutrient inputs, while others, although situated within human-influenced regions, have been relatively unaffected. These results can now be used to help set realistic goals for restoration projects.
Food-web regulation by a planktivore: exploring the generality of the trophic cascade hypothesis
Authors: Stein Roy A. , DeVries Dennis R. , Dettmers John M.
Published: May 2008

The trophic cascade hypothesis currently being tested in north temperate systems may not apply to open-water communities in lower latitude U.S. reservoirs. These reservoir communities differ dramatically from northern lakes in that an open-water omnivore, gizzard shad (Dorosoma cepedianum), often occurs in abundance. Neither controlled by fish predators (owing to high fecundity and low vulnerability) nor by their zooplankton prey (following the midsummer zooplankton decline, gizzard shad consume detritus and phytoplankton), gizzard shad regulate community composition rather than being regulated by top-down or bottom-up forces. In experiments across a range of spatial scales (enclosures, 1–9 m2; ponds, 4–5 ha; and reservoirs, 50–100 ha), we evaluated the generality of the trophic cascade hypothesis by assessing its conceptual strength in reservoir food webs. We reviewed the role of gizzard shad in controlling zooplankton populations and hence recruitment of bluegill, Lepomis macrochirus (via exploitative competition for zooplankton), and largemouth bass, Micropterus salmoides (by reducing their bluegill prey). Reservoir fish communities, owing to the presence of gizzard shad, appear to be regulated more by complex weblike interactions among species than by the more chainlike interactions characteristic of the trophic cascade.
Do high-altitude natives have enhanced exercise performance at altitude?
Authors: Brutsaert Tom D.
Published: May 2008

Natives of high altitude (HA) may have enhanced physical work capacity in hypoxia due to growth and development at altitude or, in the case of indigenous Andean and Himalayan residents, due to population genetic factors that determine higher limits to exercise performance. There is a growing scientific literature in support of both hypotheses, although the specific developmental vs. genetic origins of putative population trait differences remain obscure. Considering whole-body measures of exercise performance, a review of the literature suggests that indigenous HA natives have higher mean maximal oxygen consumption (VO2 max) in hypoxia and smaller VO2 maxdecrement with increasing hypoxia. At present, there is insufficient information to conclude that HA natives have enhanced work economy or greater endurance capacity, although for the former a number of studies indicate that this may be the case for Tibetans. At the physiological level, supporting the hypothesis of enhanced pulmonary gas exchange efficiency, HA natives have smaller alveolar–arterial oxygen partial pressure difference ((A–a)DO2), lower pulmonary ventilation (VE), and likely higher arterial O2saturation (SaO2) during exercise. At the muscle level, a handful of studies show no differences in fiber-type distributions, capillarity, oxidative enzymes, or the muscle response to training. At the metabolic level, a few studies suggest differences in lactate production/removal and (or) lactate buffering capacity, but more work is needed in this area.
Effects of carbohydrate ingestion 15 min before exercise on endurance running capacity
Authors: Tokmakidis Savvas P. , Karamanolis Ioannis A.
Published: May 2008

This study examined the effects of pre-exercise carbohydrate ingestion on exercise metabolism and endurance running capacity. Eleven active subjects (VO2 max 49.0 ± 1.7 mL·kg–1·min–1, mean ± SE) performed two exercise trials 15 min after ingesting glucose (G; 1 g·kg body mass–1) and placebo (CON). Each subject ran on a level treadmill for 5 min at 60%, 45 min at 70%, and then at 80% of VO2 max until exhaustion. Serum glucose and plasma insulin reached their peak concentrations (p < 0.01) 15 min after glucose ingestion and declined at the onset of exercise. Serum glycerol concentrations were lower (p < 0.01) in the G trial than in the CON trial after 30 min of exercise to exhaustion. In addition, after 45 min of exercise to exhaustion, the levels of free fatty acids were lower in G than in CON (p < 0.05). No differences were observed in carbohydrate oxidation rates during exercise between treatments (G, 2.53 ± 0.08 g·min–1; CON, 2.40 ± 0.09 g·min–1). Time to exhaustion was 12.8% longer in G (p < 0.01) than in CON. These results suggest that glucose ingestion 15 min before prolonged exercise provides an additional carbohydrate source to the exercising muscle, thus improving endurance running capacity.
A walking intervention improves capillary glucose control in women with gestational diabetes mellitus: a pilot study
Authors: Davenport Margie H. , Mottola Michelle F. , McManus Ruth , Gratton Rob
Published: May 2008

Exercise prescriptions that can be translated into clinical recommendations are clearly needed for women with gestational diabetes mellitus (GDM). A pilot project was developed to document the effectiveness of a structured low-intensity walking protocol on capillary glucose control in GDM women. Ten GDM women followed conventional management of diet and insulin therapy, plus a low-intensity walking program (W) from diagnosis to delivery. Capillary glucose concentrations, insulin requirements, and pregnancy outcomes were compared with a matched cohort by body mass index (BMI), age, and insulin usage (20 GDM women who followed conventional management alone (C)). Baseline capillary glucose concentrations were not significantly different between the W and C groups. The W group had an average acute drop in capillary glucose concentration from pre- to post-exercise of 2.0 mmol·L–1. In addition, the W group had significantly lower mean glucose concentrations in the fasted state and 1 h after meals than the C group in the week prior to delivery. These lower glucose concentrations were achieved while requiring fewer units of insulin per day (C, 0.50 ± 0.37 U·kg–1; W, 0.16 ± 0.13 U·kg–1; p < 0.05), injected less frequently. These results suggest an effective role in glucose regulation for this structured walking program.
Effects of weight lifting training combined with plyometric exercises on physical fitness, body composition, and knee extension velocity during kicking in football
Authors: Perez-Gomez Jorge , Olmedillas Hugo , Delgado-Guerra Safira , Royo Ignacio Ara , Vicente-Rodriguez German , Ortiz Rafael Arteaga , Chavarren Javier , Calbet Jose A.L.
Published: May 2008

The effects of a training program consisting of weight lifting combined with plyometric exercises on kicking performance, myosin heavy-chain composition (vastus lateralis), physical fitness, and body composition (using dual-energy X-ray absorptiometry (DXA)) was examined in 37 male physical education students divided randomly into a training group (TG: 16 subjects) and a control group (CG: 21 subjects). The TG followed 6 weeks of combined weight lifting and plyometric exercises. In all subjects, tests were performed to measure their maximal angular speed of the knee during instep kicks on a stationary ball. Additional tests for muscle power (vertical jump), running speed (30 m running test), anaerobic capacity (Wingate and 300 m running tests), and aerobic power (20 m shuttle run tests) were also performed. Training resulted in muscle hypertrophy (+4.3%), increased peak angular velocity of the knee during kicking (+13.6%), increased percentage of myosin heavy-chain (MHC) type IIa (+8.4%), increased 1 repetition maximum (1 RM) of inclined leg press (ILP) (+61.4%), leg extension (LE) (+20.2%), leg curl (+15.9%), and half squat (HQ) (+45.1%), and enhanced performance in vertical jump (all p ≤ 0.05). In contrast, MHC type I was reduced (–5.2%, p ≤ 0.05) after training. In the control group, these variables remained unchanged. In conclusion, 6 weeks of strength training combining weight lifting and plyometric exercises results in significant improvement of kicking performance, as well as other physical capacities related to success in football (soccer).
A single protein meal increases recovery of muscle function following an acute eccentric exercise bout
Authors: Etheridge Timothy , Philp Andrew , Watt Peter W.
Published: May 2008

The purpose of this study was to examine the effects of acute protein ingestion on the recovery of muscle function and markers of muscle damage in the 72 h post eccentric-exercise. Nine recreationally active males recorded quadriceps maximum isometric voluntary contraction (MVC), peak 5 s power output (PPO), and perceived muscle soreness. Plasma creatine kinase (CK) and protein carbonyl (PC) content were measured prior to exercise. Delayed-onset muscle soreness (DOMS) was induced by a 30 min downhill run (–10°) at a target intensity of 75% age-predicted heart rate maximum, immediately followed by ingestion of 100 g protein (containing 40 g essential amino acids; PRO) or placebo (CON) solution. The pre-exercise measures were re-taken in the subsequent 24, 48, and 72 h. CK, PC, and perceived muscle soreness increased significantly following exercise and with each supplement at 24 h. PC and muscle soreness remained elevated at 48 and 72 h (p < 0.05), whereas CK returned to baseline values. No difference between conditions was observed for these measures. Peak MVC significantly declined in CON to –7.9% at 24 h, reaching a nadir of –10% at 48 h (p < 0.05). In the PRO group, MVC remained within pre-exercise values at all time points. PPO followed a similar trend, reaching its nadir of –8.7% at 48 h in CON (p < 0.05), but had recovered in the PRO trial. Ingestion of a single post-exercise protein mixture increases the rate of force and power restoration at 48 h, suggesting potential for protein as an ergogenic aid during the DOMS period.
A comparative histological and histochemical study of the stomach from three species of pleuronectid, the Atlantic halibut, Hippoglossus hippoglossus, the yellowtail flounder, Pleuronectes ferruginea, and the winter flounder, Pleuronectes americanus
Authors: Murray Harry M. , Wright Glenda M. , Goff Gregory P.
Published: May 2008

The morphology and the histochemistry of the mucus of the pleuronectid stomach were examined using light and electron microscopy. The stomach of the winter flounder (Pleuronectes americanus) and the yellowtail flounder (Pleuronectes ferruginea) possessed a glandular or cardiac region and an aglandular or pyloric region, whereas the stomach of the Atlantic halibut (Hippoglossus hippoglossus) was entirely glandular in nature. The epithelia of the glandular region in all three species could be divided into three distinct zones based upon ultrastructural differences in the cell types present. Zone 1 contained surface mucus-secreting cells, zone 2 contained mucous neck cells, and zone 3 contained oxyntico-peptic cells or gland cells. The presence of ultrastructurally distinct cells in the neck region is not consistent with observations of all teleost species and supports the theory that teleost gastric glands may exist with or without distinct mucous neck cells. Variation in mucous histochemistry across gastric zones as well as between species suggests that the chemical nature of the luminal environment during digestion may be different as a consequence of differences in natural diet. Two types of enteroendocrine-like cells were identified in association with zone 1, based upon granule morphology: type I was of the "closed" variety, but the variety of the type II enteroendocrine-like cell was not resolved from this study.
Antibacterial activity of the seminal plasma of Paracentrotus lividus
Authors: Stabili Loredana , Canicattì Calogero
Published: May 2008

Seminal plasma from Paracentrotus lividus exerted an inhibitory action on the growth of bacterial colonies. The antibacterial reaction took 30 min to reach full expression and depended on both the dose of seminal plasma and the bacterial cell number. Heating at 56 °C for 60 min did not lower the antibacterial power of the seminal plasma. Morphological examination of bacteria treated with seminal plasma revealed a conspicuous alteration of their surface and suggested a lytic mode of action for the antibacterial factor(s). Lysozyme could be involved in this process. In fact, inhibition of bacterial growth strongly decreased when this hydrolase was inactivated by heating at a basic pH.
Thermoacclimatory hematological response: Have we been using appropriate conditions and assessment methods?
Authors: Houston Arthur H. , Schrapp M. Pilar
Published: May 2008

Goldfish (Carassius auratus L.) were acclimated to three types of thermal regime: constant temperature (12, 28 °C), a diurnal sine-wave cycle (20 ± 8 °C), and a randomly fluctuating pattern of ±2 °C changes at 2-h intervals between 12 and 28 °C. Assessment of hematological response was based on determination of total red cell numbers and hematocrit values, and through characterization of circulating red cell populations in terms of absolute and relative abundances of juvenile, developing, mature, Trypan Blue-positive, karyorrhectic, dividing, and tailed or recently divided cells. While no significant differences in cell counts were observed, cell population composition was markedly affected by temperature regime. Variation during acclimation, particularly when this resembled that likely to be experienced under natural circumstances, was associated with significantly increased numbers of juvenile and developing cells, and thus with increased potential for reorganization of hemoglobin isomorph systems. The converse was true of mature cell abundances; these varied inversely with temperature and were significantly reduced under varying temperature conditions. It is concluded that studies involving constant acclimation temperatures are unlikely to provide valid information regarding functional hematological status, in this species at least. It is also concluded that the primary hematological indices and their derivatives (red cell numbers, hemoglobin, hematocrit, mean erythrocytic volume, and hemoglobin) commonly used to monitor hematological response to environmental change are insufficiently sensitive for the purpose.
Influence of temperature and other factors on the daily roosting times of Mourning Doves in winter
Authors: Doucette Denis R. , Reebs Stéphan G.
Published: May 2008

From November 1992 to February 1993, observations were made during 30 departures and 30 arrivals at a Mourning Dove (Zenaida macroura) roost in Moncton, New Brunswick, Canada. Our objective was to identify the effect of cold on the timing of roosting flights in this species, a recent addition to the local wintering fauna. The effect of other environmental factors was taken into account by including them, along with temperature, in a multiple regression analysis. Doves left the roost later relative to sunrise (i) on longer days, (ii) on cloudy mornings, (iii) when fewer birds were using the roosts, (iv) on colder mornings, and (v) when winds were high. They returned to the roost later relative to sunset (i) on colder evenings and (ii) in clear weather. Late arrivals on colder days represent an unusual finding. Anatomical and behavioural considerations suggest that Mourning Doves cannot reduce heat loss as substantially as other species; therefore, late arrivals on cold evenings may reflect the more important role of energy gain through extended foraging required to survive the long winter night.
Food habits of the river otter in a boreal ecosystem
Authors: Reid D. G. , Code T. E. , Reid A. C. H. , Herrero S. M.
Published: May 2008

Food habits of river otter (Lontra canadensis) were quantified by analysis of 1191 scats systematically collected in the Winefred Lake area (Athabasca River drainage) of northeastern Alberta to assess seasonal prey selection, the utility of scats for fish inventory, and the prominence of beavers as otter food. Fish dominated the annual diet, being found in 91.9% of scats. Insects, molluscs, crustaceans, and waterfowl were also substantial prey. Less agile, abundant shallow-water fish, such as a catostomid and various cyprinids, were the most common prey. Coregonine fish dominated the diet during their autumn spawning, were rarely eaten in summer when in the hypolimnion, but appeared to be preferred prey. In winter, with virtually no open water, the diet was less diverse and was dominated by cyprinid and gasterosteid fish. Such a fish fauna exists in small lakes, bog ponds, and beaver impoundments. We hypothesize that in winter, otters select water bodies, and consequently available prey, on the basis of shoreline substrate and morphology and relative ease of passage from air to water. Otter scats contained 14 of 18 fish species known to be in the study area. However, the contents of scats overestimated the diversity offish species inhabiting individual lakes. Beavers were occasionally eaten by otters, but were a minor component of the diet.