bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of models predicting invertebrate assemblages for biomonitoring in the Fraser River catchment, British Columbia
Authors: Reynoldson T B , Rosenberg D M , Resh V H
Published: April 2011

A multivariate, predictive model based on the reference-condition approach is described for the Fraser River catchment in British Columbia. Benthic invertebrate assemblages and environmental descriptors were measured at more than 200 sites from 1994 to 1996, including 219 reference sites. Reference sites were classified into groups representing similar invertebrate assemblages. Five such classifications were produced, using three taxonomic levels (family, genus, and species) and species and family multimetrics. For each of the classifications, discriminant function analysis was used, with environmental descriptors, to develop a predictive model for the reference sites. These models predicted from 43.8% (species) to 61.6% (family) of the reference sites to the correct benthic group. Each model was used to assess deviation from reference condition for 21 test sites exposed to either agriculture, logging, or mining. The models were examined with regard to their sensitivity, robustness, usability, temporal variability, predictive performance, and model certainty. The family and family-metric models were ranked best, followed by the species-metric, genus, and species models. The family-level model is recommended for assessment purposes; its overall performance was slightly superior to the family-metric model and it avoids an extra step in calculation of the metrics. However, the species-level model is recommended for conservation or biodiversity issues.
Implications of seasonal variation for biomonitoring with predictive models in the Fraser River catchment, British Columbia
Authors: Reece Pamela F , Reynoldson Trefor B , Richardson John S , Rosenberg David M
Published: April 2011

Reference-condition models for the Fraser River catchment were developed using samples collected during the autumn of 1994, 1995, and 1996. The goal of this study was to examine applicability to the reference-condition models of samples collected in other seasons and the effect of taxonomic resolution (genus and family) on model sensitivity to seasonal variation in the benthic invertebrate assemblage. Samples from eight streams representing interior, coastal, and large-river habitats were collected in spring, summer, autumn, and winter of 1995 and in spring of 1996. The benthic invertebrate assemblage changed seasonally such that the models could not be used for seasons other than autumn. The models were equally sensitive to seasonal variation when genus-level or family-level data were used. We recommend that test samples (i.e., samples collected from disturbed sites and meant for comparison with the reference database) be collected either during the autumn or over multiple sampling dates to reduce the possibility that seasonal shifts or stochastic events will lead to erroneous conclusions about the state of a test site.
Early familiarity has fitness consequences for Arctic char (Salvelinus alpinus) juveniles
Authors: Seppä Teija , Laurila Anssi , Peuhkuri Nina , Piironen Jorma , Lower Nicola
Published: April 2011

Familiarity is an important factor reducing aggressiveness among individuals. Because of the reduced energy and time expenditure due to lowered aggression, individuals would be expected to perform better in groups of familiar conspecifics as compared with individuals in groups of strangers. However, few studies have examined potential fitness consequences of familiarity. We created familiar (from tanks where several thousands of unrelated fish had been kept since fertilization) and unfamiliar (by combining fish from several tanks) groups of underyearling Arctic char (Salvelinus alpinus) and followed their performance for a 21-day period. Familiarity within groups enhanced survival and body condition of the fish. The fish in familiar groups also grew better in weight and in length. Furthermore, familiar fish differed less in length variation after the experimental period compared with fish reared in unfamiliar groups. There was also a tendency towards similar difference in the variation of weight. These results provide direct evidence for beneficial fitness consequences of early familiarity in Arctic char.
Developing Baltic cod recruitment models. II. Incorporation of environmental variability and species interaction
Authors: Köster Friedrich W , Hinrichsen Hans-Harald , St. John Michael A , Schnack Dietrich , MacKenzie Brian R , Tomkiewicz Jonna , Plikshs Maris
Published: April 2011

We investigate whether a process-oriented approach based on the results of field, laboratory, and modelling studies can be used to develop a stockenvironmentrecruitment model for Central Baltic cod (Gadus morhua). Based on exploratory statistical analysis, significant variables influencing survival of early life stages and varying systematically among spawning sites were incorporated into stockrecruitment models, first for major cod spawning sites and then combined for the entire Central Baltic. Variables identified included potential egg production by the spawning stock, abiotic conditions affecting survival of eggs, predation by clupeids on eggs, larval transport, and cannibalism. Results showed that recruitment in the most important spawning area, the Bornholm Basin, during 19761995 was related to egg production; however, other factors affecting survival of the eggs (oxygen conditions, predation) were also significant and when incorporated explained 69% of the variation in 0-group recruitment. In other spawning areas, variable hydrographic conditions did not allow for regular successful egg development. Hence, relatively simple models proved sufficient to predict recruitment of 0-group cod in these areas, suggesting that key biotic and abiotic processes can be successfully incorporated into recruitment models.
Spatial covariation in survival rates of Northeast Pacific pink salmon (Oncorhynchus gorbuscha)
Authors: Pyper Brian J , Mueter Franz J , Peterman Randall M , Blackbourn David J , Wood Chris C
Published: April 2011

We examined spatial patterns of covariation in indices of survival rate (residuals from the best-fit stock- recruitment curve) across four decades among 43 wild pink salmon (Oncorhynchus gorbuscha) stocks from 14 geographical regions in Washington, British Columbia, and Alaska. We found strong evidence of positive covariation among stocks within each region and between certain adjacent regions (e.g., correlations from 0.3 to 0.7) but no evidence of covariation between stocks of distant regions (e.g., separated by 1000 km or more). This suggests that important environmental processes affecting temporal variation in survival rates of pink salmon from spawners to recruits operate at regional spatial scales rather than at the larger ocean basin scale. Based on limited fry abundance data, we found that this covariation in spawner-to-recruit survival rates may be strongly influenced by marine processes.
Hierarchical Bayesian models of length-specific catchability of research trawl surveys
Authors: Harley Shelton J , Myers Ransom A
Published: April 2011

To estimate absolute abundance from research trawl surveys, the catchability of the fish to the gear must be known or estimated. Using 47 data sets of length-specific catchability, we conducted a hierarchical Bayesian meta-analysis of length-specific catchability for a number of different species groups. It was found that the Bayesian estimates of catchability were seldom near or above 1 for any species or size. This suggests that any assumption that swept-area abundance estimates are in fact absolute abundance would likely underestimate the true abundance. Catchability was higher for haddock (Melanogrammus aeglefinus) than for Atlantic cod (Gadus morhua) of the same size, suggesting behavioural differences between these two species. We found a seasonal difference in catchability with higher catchability for surveys in summerfall than for those in springwinter. The results of this study can be applied both for the reconstruction of fish community structure for ecosystem models and as auxiliary (or prior) information for single-species stock assessment where catchability is estimated within the stock assessment procedure.
A comparison of salmon escapement estimates using a hierarchical Bayesian approach versus separate maximum likelihood estimation of each year's return
Authors: Adkison Milo D , Su Zhenming
Published: April 2011

In this simulation study, we compared the performance of a hierarchical Bayesian approach for estimating salmon escapement from count data with that of separate maximum likelihood estimation of each year's escapement. We simulated several contrasting counting schedules resulting in data sets that differed in information content. In particular, we were interested in the ability of the Bayesian approach to estimate escapement and timing in years where few or no counts are made after the peak of escapement. We found that the Bayesian hierarchical approach was much better able to estimate escapement and escapement timing in these situations. Separate estimates for such years could be wildly inaccurate. However, even a single postpeak count could dramatically improve the estimability of escapement parameters.
Long-term effects of resource limitation on stream invertebrate drift
Authors: Siler Edward R , Wallace J Bruce , Eggert S L
Published: April 2011

We examined the effects of resource limitation on stream invertebrate drift by reducing inputs of terrestrial detritus to a headwater stream in western North Carolina. In the treatment stream, leaf-litter was excluded for 6 years (September 1993  August 1999), small woody debris was removed for 2 years (September 1996  August 1998), and large and small woody debris was removed for 1 year (September 1998  August 1999). Invertebrate abundance in the drift was significantly lower in the treatment stream during the study, but total biomass of invertebrate drift was similar. Although drift densities were higher in the reference stream, a greater proportion of total benthic invertebrate abundance and biomass drifted out of the treatment stream. The proportion of shredder, gatherer, and predator benthic abundance in the drift was significantly greater in the treatment stream, but scraper proportions were higher in the reference stream and filterer proportions were similar for the two streams. Combined data from both streams indicated that the relationship between drift densities and benthic abundance was positive and significant. Our results demonstrate that bottom-up effects of resource reduction in a detrital-based stream influence invertebrate drift, increasing the proportion of the benthic community emigrating from the detritus-poor stream.
Using demographic methods to construct Bayesian priors for the intrinsic rate of increase in the Schaefer model and implications for stock rebuilding
Authors: McAllister M K , Pikitch E K , Babcock E A
Published: April 2011

Even though Bayesian methods can provide statistically rigorous assessments of the biological status of fisheries resources, uninformative data (e.g., declining catch rate series with little variation in fishing effort) can produce highly imprecise parameter estimates. This can be counteracted with the use of informative Bayesian prior distributions (priors) for model parameters. We develop priors for the intrinsic rate of increase (r) in the Schaefer surplus production model using demographic methods and illustrate the utility of this with an application to large coastal sharks in the Atlantic. In 1996, a U.S. stock assessment obtained a point estimate for r of 0.26. For such long-lived and low-fecund organisms, this could potentially be too high. Yet it was used to predict that within about 10 years, a 50% reduction in the 1995 catch level should result in >50% chance of increasing the population to the abundance required to produce maximum sustainable yield. In contrast, a Bayesian assessment that used demographic analysis to construct a prior for r with a median of 0.07 and coefficient of variation (CV) of 0.7 indicated that within 30 years, this policy would have only a very small chance of increasing the population to maximum sustainable yield.
Evaluating sampling sufficiency in fish assemblage surveys: a similarity-based approach
Authors: Cao Yong , Larsen David P , Hughes Robert M
Published: April 2011

The number and identity of fish species occurring at a site at a particular time provide basic information for assessing biological integrity, inferring fish assemblage  environment relationships, and determining biodiversity patterns. Conclusions are often dependent on how sufficiently species richness and composition of fish assemblages are characterized by sampling. The proportion of total species richness obtained in a sample is an explicit measure of sampling sufficiency. However, because total species richness (TSRtru) at a site is often unknown, sampling sufficiency cannot be determined directly. To overcome this difficulty, we developed a new approach, which is based on a relationship between the proportion of TSRtru or %TSRtru and the similarity among replicate samples (autosimilarity). With autosimilarity measured with the Jaccard coefficient (JC), a simple relationship was established: %TSRtru = 100JC. Fourteen sites where TSRtru was reached or approached during sampling were selected from four surveys to validate this relationship. We used the approach to estimate the sample sizes required for 90, 95, and 100% TSRtru, indicating that widely differing sampling efforts among sites are needed to obtain the same proportion of the local species pool. The results strongly support the use of the new approach in evaluating sampling sufficiency in stream and river fish surveys.
Rapid Communication / Communication rapideArea-dependent patterns of finfish diversity in a large marine ecosystem
Authors: Frank Kenneth T , Shackell Nancy L
Published: April 2011

The speciesarea relationship (SAR) is considered a cornerstone of terrestrial and freshwater ecology and conservation. It has rarely been examined in a large marine ecosystem because it has been assumed that sufficient data are lacking and (or) the scales of oceanic systems are too large. Using data drawn from fishery surveys, we show a positive relationship between the number of finfish species and the area of submarine, offshore banks on the continental shelf off eastern Canada. Banks of similar size yielded similar species richness regardless of the distance between them. Area per se had a stronger influence on species number than did habitat diversity. The slope of SAR observed is consistent with the tendency for many of the species to be highly migratory with widely dispersing offspring. This results in strong interactions among banks. The combined densities of all species increased with bank area, suggesting that larger banks have higher resources per unit area. Populations and species on larger banks should be more resilient to local extinctions relative to those on smaller banks, and natural or human-induced perturbations might be expected to impact the community structure of the small, extinction-prone populations at a faster rate.
Effect of predation on the low-density dynamics of vendace: significance of the functional response
Authors: Heikinheimo Outi
Published: April 2011

During the past 20 years, there have been prolonged vendace (Coregonus albula) recessions in several Finnish lakes. Hypotheses have been proposed that predation by brown trout (Salmo trutta m. lacustris) or perch (Perca fluviatilis) on young-of-the-year vendace could prevent the recovery of the vendace stocks from a low-density state. In this study, dynamic modelling was applied to examine the effect of predation, assuming a dome-shaped spawning stockrecruitment relationship for vendace, type II or III functional responses to predation by brown trout and perch, and a constant rate of fishing. The results showed that the form of the functional response is crucial in determining the significance of the predation on vendace stocks that have a steep dome-shaped stockrecruitment relationship. In all cases, however, predation by perch had more effect than that by brown trout, probably due to perch occupying the pelagic zone when the vendace stock is sparse. This may make the mortality of vendace increase with decreasing population density (depensatory mortality) at certain density levels.
Response of fish communities to different levels of white sucker (Catostomus commersoni) biomanipulation in five temperate lakes
Authors: Brodeur Philippe , Magnan Pierre , Legault Michel
Published: April 2011

The goal of this study was to evaluate the response of white sucker (Catostomus commersoni), brook trout (Salvelinus fontinalis), and other fish species to the mass removal of white sucker in five Québec (Canada) lakes. White sucker removal ranged from 14.2 kg·ha1 to 31.3 kg·ha1 3 years after mass removal. In four of the study lakes, the proportion of 2+ to 4+ white sucker increased following mass removal. Mean catch and biomass per unit of effort of 1+ brook trout increased significantly in the lakes where white sucker removal was highest. All white sucker populations experienced growth increases after mass removal, and improved brook trout growth was observed in lakes where the most intensive mass removal occurred. These growth increases led to higher mean length at maturity in white sucker females and decreases in mean age at maturity in white sucker males and brook trout males and females. Mean adjusted fecundity significantly increased in white sucker and brook trout in lakes where mass removal was most intense. The present study suggests that white sucker and brook trout exhibit compensatory responses following a reduction of intra- and inter-specific competition and that these responses are related to the intensity of mass removal.
The functional response of drift-feeding Arctic grayling: the effects of prey density, water velocity, and location efficiency
Authors: O'Brien W John , Barfield Michael , Sigler Karen
Published: April 2011

An important aspect of a predatorprey system is the functional response of the predator to changing prey densities. We studied the feeding rate response of drift-feeding Arctic grayling (Thymallus arcticus) on a small invertebrate prey, Daphnia middendorffiana, at densities ranging from 0.01 L1 to 1.8 L1 and current velocities of 25, 32, and 40 cm·s1. We videotaped the feeding of grayling to determine the duration of the search and pursuit components of the feeding cycle and the location efficiency of grayling feeding at different current velocities. Feeding rate increased approximately as the prey density to the 0.4 power from 0.01 to 1.25 prey·L1, above which the feeding rate dropped. Current velocity had no significant effect on feeding rate. Search and pursuit times dropped with increasing prey density, but neither was affected by current velocity. However, current velocity reduced both maximum location distance and location efficiency. The lack of increase in feeding rate with increasing current velocity may be due to a trade-off between the increasing likelihood of encounter and decreasing location efficiency as current velocity increases. These data suggest that grayling could effectively feed in a variety of stream habitats with different current velocity.
Climate change and abundance cycles of two sympatric populations of smelt (Osmerus mordax) in the middle estuary of the St. Lawrence River, Canada
Authors: Mingelbier M , Lecomte F , Dodson J J
Published: April 2011

Commercial catches of two ecologically distinct sympatric smelt (Osmerus mordax) populations segregated along the two shores of the St. Lawrence middle estuary exhibited inverse patterns with periodicities on the order of 30 years. The influence of water level in the St. Lawrence River and air temperature, chosen to reflect variations in hydrology and climate, differed markedly between the two populations. Analyses revealed that both water level and temperature were generally positively related with north-shore smelt landings and negatively related with south-shore smelt landings. For both populations, a number of significant climatic factors contributing to variance in smelt landings were lagged by one to three years relative to the year of landings, indicating that climatic variables influenced smelt recruitment. The contrasting role of hydroclimatic variables in driving these abundance cycles is likely related to differential exploitation of estuarine habitats; the south-shore population is associated with shallow shoal habitat, whereas the north-shore population is associated with deep channel habitat. The responses of the two smelt populations also reflect the fundamental ecological differences existing between shoal and channel habitats, indicating that future climate change may differentially affect other populations or species that are segregated between these two habitats.
The von Bertalanffy growth function, bioenergetics, and the consumption rates of fish
Authors: Essington Timothy E , Kitchell James F , Walters Carl J
Published: April 2011

The von Bertalanffy growth function (VBGF) is based on a bioenergetic expression of fish growth; therefore, size-at-age data can theoretically be used to estimate fish consumption rates. We evaluated the accuracy of VBGF-derived consumption rates by performing a meta-analysis and sensitivity analysis of VBGF assumptions, and we used Bayesian parameter estimation to quantify uncertainty in these estimates. The VBGF was robust to its assumption regarding the allometry of catabolism but was highly sensitive to the assumed allometry of consumption. Consequently, the commonly used form ("specialized" VBGF), which makes a strong assumption regarding the allometric slope of consumption, often grossly underestimates (>50%) consumption. The precision of the VBGF depended on characteristics of the size-at-age data used to parameterize the model. When data indicate decelerating growth, consumption rates were estimated with good precision; we estimated a 70% probability that bluefin tuna (Thunnus thynnus) consumption rates were between 1 and 2% body mass per day. Otherwise, consumption estimates were poorly defined; yellowfin tuna (Thunnus albacares) consumption rates between 2 and 7% per day were all equally likely. We conclude that VBGF can be a useful tool for estimating fish consumption rates, but potential biases and precision of these estimates should be evaluated on a case-by-case basis.
Direct and indirect effects of sediment pulse duration on stream invertebrate assemblages and rainbow trout (Oncorhynchus mykiss) growth and survival
Authors: Shaw E Al , Richardson John S
Published: April 2011

Elevated concentrations of inorganic sediment supply in streams may impair many biological functions. However, the contribution of exposure duration to the observed impacts has not been previously considered. We evaluated the effects of sediment pulse duration using 14 streamside flow-through experimental channels, each of which contained a naturally colonised invertebrate assemblage and 10 rainbow trout (Oncorhynchus mykiss) fry. Channels were exposed to fine sediment pulses of constant concentration but varied pulse duration (ranging from 0 to 6 h) every second day over 19 days. Total abundance of benthic invertebrate and family richness declined as sediment pulse duration increased. Invertebrate drift total abundance increased as pulse duration increased; however, family richness of drift decreased. Trout length and mass gain over the 19-day period was negatively correlated with pulse duration. Path analysis suggests that the direct effects of fine sediment on trout (impaired vision leading to reduced prey capture success and (or) increased metabolic costs from physiological stress) are more important to trout growth than indirect effects (decreased drift and benthic invertebrate richness and drift abundance).
Patterns of gross deposition in reservoirs enriched in inorganic tripton
Authors: Effler Steven W , Matthews (Brooks) Carol M , Matthews David A
Published: April 2011

Magnitudes and patterns in the deposition of chlorophyll (Chl), organic carbon, particulate phosphorus (PP), and suspended solids are documented for seven New York reservoirs based on analyses of metalimnetic and near-bottom sediment trap collections. Inorganic material dominated the trap collections and caused a decoupling of the downward fluxes of Chl and PP because of major contributions of inorganic components to P deposition. These contributions were manifested in the stoichiometry of trap collections, the much higher estimates of settling velocity (SV) for PP compared with Chl, and differences in patterns of Chl and PP deposition within individual reservoirs and among these systems. Most of the deposited phosphorus in these reservoirs (7198%) was associated with nonphytoplankton particles. In contrast to the other constituents, the estimates of SV for Chl were lower and more uniform; nearly 50% of the individual estimates (n = 188) were between 0.15 and 0.25 m·day1. Longitudinal gradients in sediment deposition occurred as a result of gradients in both overlying water concentrations and settling characteristics of the particles. Seasonal and vertical patterns in trap collections and budget calculations indicate that resuspension contributed to deposition, to varying extents, in all of the reservoir basins.
A new ageing method for eggs of fish species with daily spawning synchronicity
Authors: Bernal M , Borchers D L , Valdés L , Lanzós A Lago de , Buckland S T
Published: April 2011

A new method for ageing staged eggs of fish is presented. The method is intended for species that show spawning synchronicity and for which the egg phase can be classified into development stages, each of which lasts less than a day, such as sardines and anchovies. It combines biological information on the daily frequency of spawning and egg development rates, via a probabilistic resampling method. A general methodology that allows the use of models of daily spawning frequency and egg development as a function of temperature is provided and applied to sardine egg data from three surveys in northern Spain. Unlike previous ageing methods, the proposed method allows for the variability of egg ages in a way that reflects the extent of the assumed daily spawning period, and estimates of the uncertainty in the stage-to-age conversion can be obtained. These estimates of uncertainty can be incorporated into subsequent analyses that involve age as a covariate, such as in the daily egg production method (DEPM), thus allowing more reliable estimates of the variance of egg production.
Changes in zooplankton and the phenology of the spiny water flea, Bythotrephes, following its invasion of Harp Lake, Ontario, Canada
Authors: Yan Norman D , Blukacz Agnes , Sprules W Gary , Kindy Paul K , Hackett David , Girard Robert E , Clark Bev J
Published: April 2011

The crustacean zooplankton community of Harp Lake, Ontario, Canada, has changed appreciably since the invasion by the spiny water flea, Bythotrephes. Crustacean species richness has declined, large-bodied Cladocera have replaced small-bodied ones, and there has been a downward trend in the total abundance of zooplankton because copepod abundance has remained stable while Cladoceran abundance has declined. Although the zooplankton community has now been stable for 4 years (19951998), the biology of the invader has changed dramatically. In particular, there have been 10-fold differences in the mean annual abundance of Bythotrephes in this 5-year period and substantial changes in the timing of population maxima. We attribute these changes to two factors: (i) transition from a summer to a fall switch from parthenogenesis to gametogenesis and (ii) interannual differences in the thickness of a warm, dark stratum in the lake. We hypothesize that this stratum provides a refuge for Bythotrephes from predation by lake herring, Coregonus artedii.
Application of decision analysis to evaluate recovery actions for threatened Snake River spring and summer chinook salmon (Oncorhynchus tshawytscha)
Authors: Peters Calvin N , Marmorek David R
Published: April 2011

There is uncertainty about the importance of various factors in explaining declines of chinook salmon (Oncorhynchus tshawytscha) populations in the Snake River basin of Oregon and Idaho. This uncertainty has prevented implementation of long-term recovery actions for these stocks. We used simulation models and decision analysis to evaluate three management actions for seven index stocks of Snake River spring and summer chinook salmon: (i) continue current operation of the Columbia River hydropower system, (ii) maximize transportation of smolts, and (iii) natural river drawdown (breaching) of four Snake River dams. Decision analysis provided a useful approach for including multiple hypotheses about population responses to environmental and anthropogenic factors, systematically assessing the importance of alternative hypotheses, and identifying risk-averse recovery strategies that meet survival and recovery goals over a wide range of uncertainties. We found that the most influential uncertainties were related to hypothesized causes of estuary and ocean mortality. Current monitoring provides limited information on survival in this life stage; carefully designed management experiments are more likely to generate useful information. Given that these uncertainties exist, drawdown was the most risk-averse action, meeting long-term survival and recovery goals over a wider range of assumptions than the other actions.
Application of decision analysis to evaluate recovery actions for threatened Snake River fall chinook salmon (Oncorhynchus tshawytscha)
Authors: Peters Calvin N , Marmorek David R , Deriso Richard B
Published: April 2011

We used models and decision analysis to incorporate uncertainties into evaluations of two recovery actions for Snake River fall chinook salmon (Oncorhynchus tshawytscha): (i) maximize transportation and (ii) natural river drawdown of four lower Snake River dams. In the retrospective analysis, we compared alternative stockrecruit models and selected one that was consistent with historical spawnerrecruit data and allowed us to implement alternative hypotheses about hydrosystem, hatchery, harvest, and environmental effects. In the prospective analysis, we used this model and posterior distributions of its parameters in a decision analysis framework to compare projected escapements for the two actions over a range of alternative hypotheses. We found that drawdown was most risk averse, producing larger long-term escapements than maximizing transportation under most hypotheses and model assumptions. Maximizing transportation and drawdown produced similar escapements only if we assumed high or increasing estuary and ocean survival rates of transported fish coupled with either severe reductions in harvest rates or insensitivity of upstream survival rates to dam construction and removal. Although there was relatively little information available for Snake River fall chinook (particularly about estuary and ocean survival rates of transported smolts), decision analysis was a useful technique for organizing data, assessing actions over a range of uncertainties, and identifying research priorities.
Thermal heterogeneity along a braided floodplain river (Tagliamento River, northeastern Italy)
Authors: Arscott David B , Tockner Klement , Ward J V
Published: April 2011

Daily and seasonal water temperature patterns were investigated at 22 habitats in five geomorphic reaches along an Alpine-Mediterranean river. Study reaches spanned 2nd- to 7th-order river segments. Habitats included headwater streams, main and secondary channels, backwaters, and isolated pools. Multiple linear regression analyses extracted elevation and azimuth (aspect) out of eight geographical and environmental variables to explain average daily temperature patterns among habitats. Azimuth and, to a lesser degree, slope, depth, velocity, and canopy were primary determinants of diel temperature amplitude and maximum rates of diel heating and cooling. Within lowland floodplain reaches, the relative influence of groundwater and surface water varied substantially among habitats. Thermal variation among habitats was greatest in lowland floodplain reaches (nearly 15°C difference). In summer and autumn, variation between lowland floodplain aquatic habitats exceeded thermal variation observed in the main channel along the entire river corridor (120 km; 51100 m above sea level). Spatiotemporal variation in temperature was greatest in lower reaches owing to the interaction of water level and connectivity of isolated water bodies. Influence of groundwater and cool-water tributaries exemplified the importance of local factors (geomorphology and hydrology) superimposed on regional factors (climate and altitude) in determining large-scale thermal patterns.
Multiyear homing of Atlantic cod to a spawning ground
Authors: Robichaud D , Rose G A
Published: April 2011

Long-term sonar transmitting tags were implanted in 27 female and 21 male cod (Gadus morhua) at the Bar Haven spawning ground in Placentia Bay, Newfoundland, in April 1998. Two thirds of tagged fish were relocated. All relocations during the 1999 and 2000 spawning seasons were within 10 km of the tagging site, the majority being within a few hundred metres. No tagged fish were relocated at other spawning grounds or elsewhere in the bay during the spawning season. Outside the spawning season, several tagged fish were relocated in other parts of the bay at ranges of a few kilometres to 110 km from the tagging site, as were 13 of 15 fishery returns (2 returns from several hundred kilometres outside the bay). Homing rates in 1999 and 2000 were 39% and 53%, respectively, after adjustments for tag loss, mortality, misreporting, and relocation efficiency based on returns from a sea-bed beacon tag left at the Bar Haven grounds. Multiyear homing was observed in 26% of cod. This study provides the first direct evidence that cod undertaking long-distance feeding migrations may home to a specific spawning ground in consecutive years, and a hypothesis for the slow recolonisation rates observed in North Atlantic cod stocks.
IV.: Plankton Diatoms, their Distribution and Bathymetric Range in St. Andrews Waters.
Authors: Fritz B.A., M.Sc. Clara W.
Published: April 2011

not available
XIV: Key to the Hydroids of Eastern Canada.
Authors: Fraser C. McLean
Published: April 2011

not available
No. 9: THE QUILL LAKES OF SASKATCHEWAN AND THEIR FISHERY POSSIBILITIES
Authors: HUNTSMAN A. G.
Published: April 2011

not available
No. 2: THE ISOPODA OF DEPARTURE BAY AND VICINITY, WITH DESCRIPTIONS OF NEW SPECIES, VARIATIONS, AND COLOUR NOTES
Authors: FEE A. R.
Published: April 2011

not available
No. 12: THE HYDROIDS OF THE CHETICAMP EXPEDITION OF 1917
Authors: FRASER C. MCLEAN
Published: April 2011

not available
A COMPARATIVE STUDY OF AUTOLYSIS AND BACTERIAL DECOMPOSITION IN HADDOCK, LOBSTER AND CLAM MUSCLE
Authors: REED GUILFORD B. , RICE CHRISTINE E. , SINCLAIR R. J.
Published: April 2011

not available
THE INTESTINAL AND SLIME FLORA OF THE HADDOCK: A PRELIMINARY REPORT
Authors: REED GUILFORD B. , SPENCE C. MARION
Published: April 2011

not available
PACIFIC SALMON MIGRATION: REPORT ON THE TAGGING OPERATIONS IN 1926, WITH ADDITIONAL RETURNS FROM THE OPERATIONS OF 1925
Authors: WILLIAMSON D.SC., F.R.S.E. H. CHAS.
Published: April 2011

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AN INVESTIGATION OF THE LIFE HISTORY AND PROPAGATION OF THE SOCKEYE SALMON (ONCORHYNCHUS NERKA) AT CULTUS LAKE, BRITISH COLUMBIA: NO. 1. INTRODUCTION AND THE RUN OF 1925
Authors: FOERSTER PH. D. R. E.
Published: April 2011

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BACTERIA CONCERNED IN THE SPOILAGE OF HADDOCK III. FURTHER OBSERVATIONS ON THE FLORA OF LIVE FISH
Authors: GEE A. H.
Published: April 2011

not available
THE SPAWNING AND EARLY LIFE HISTORY OF THE WHITEFISH, COREGONUS CLUPEAFORMIS (MITCHILL), IN THE BAY OF QUINTE, ONTARIO
Authors: HART JOHN LAWSON
Published: April 2011

The spawning run of whitefish is described in respect to the details of the migration and sex ratio, age and size, and breeding characters of the fish. An investigation of the eggs in the spawning grounds by the use of a pump indicates that the proportion of eggs to be fertilized is high but that there is a high mortality during the development. Many whitefish eggs are eaten on the spawning grounds by the common perch (Perca flavescens). For the first time there is recorded the capture of a complete series of whitefish young of the year. Based on this material are descriptions of the stages of the young from twelve millimetre to eighty millimetre stages and the characters differentiating whitefish from cisco. The rate of growth of the fry is slow at first but is much accelerated in the latter part of May and until the end of July. The food from the first consists of Entomostraca, chiefly Bosmina, Daphnia and Cyclops. The first movement of the newly hatched fry is inshore close to the surface. Later they form schools and finally take to deeper water. Records of physical conditions in the habitat of young whitefish are recorded. Consideration of the food and other habits and the concentration of predaceous species where young whitefish are abnormally abundant leads to the recommendation that hatchery fry should be widely distributed in shallow water.
DESCRIPTION OF TWO NEW FORMS OF BRITISH COLUMBIA TROUT
Authors: DYMOND J. R.
Published: April 2011

The Kamloops and Cut-throat trout found at high altitudes in British Columbia differ in so many respects from those occurring at lower levels that it has been found advisable to recognize them as subspecifically distinct from the latter. Two new subspecies are therefore described, viz., Salmo kamloops whitehousei and Salmo clarkii alpestris.
THE INFLUENCE OF LOW TEMPERATURES ABOVE FREEZING UPON THE RATE OF AUTOLYTIC AND BACTERIAL DECOMPOSITION OF HADDOCK MUSCLE
Authors: HESS ERNEST
Published: April 2011

The influence of temperature upon autolytic and bacterial decomposition of haddock muscle within the range of 36 to 30° F. (+2.2 to −1.1 °C.) has been followed by determining the increase in the amount of volatile basic nitrogen parallel with the increase in the number of bacteria. A mixed flora of bacteria normally occurring on haddock was used for inoculation purposes. The experimental results show that practically no autolysis takes place at these temperatures, and that the bacterial decomposition and bacterial growth rate at 30° F. is only about half of that at 36° F. Expressed in mathematical terms, it was found that the temperature coefficients (Q10) for these reactions during the phases of logarithmic increase were considerably higher than the values for Q10 for ordinary life processes at medium temperatures (Q10 = 2 to 3, van't Hoff). The values for Q10 increased rapidly with decreasing temperature range. The practical application of these findings has been demonstrated to be of economical importance in the holding of fresh fish at 30° F. instead of the customary holding in crushed ice at about 36° F.
NOTE ON THE PARTITION OF NON-PROTEIN NITROGEN IN AUTOLYSED HADDOCK'S MUSCLE
Authors: KOMAROV S. A.
Published: April 2011

Aseptic autolysis of haddock muscle gives a great increase in non-protein and amino nitrogen (due chiefly to liberation of ammonia and hydrolysis of proteins), small increase in nitrogenous bases, and a decrease in urea content.
A BACTERIOLOGICAL STUDY OF "ICE FILLETS"
Authors: GIBBONS NORMAN E.
Published: April 2011

Twenty-nine "ice fillets" (mostly haddock) were examined bacteriologically after varying periods of storage at temperatures from −5° to −18 °C.Quantitative examinations would indicate that, after an initial decrease due to freezing, there is little change in the number of bacteria in fillets at −18 °C. for a year. A gradual decrease follows. In fillets stored at −5 °C. there is an increase after about fifty weeks. A psychrophilic flora seems to predominate after long periods of storage.Sixty-eight species and varieties of bacteria were isolated and grouped, as far as possible, according to the species they most closely resembled. Twenty strains, belonging to the genus Achromobacter, could not be placed.
FLUCTUATIONS IN THE ABUNDANCE OF PLANKTONIC DIATOMS IN THE PASSAMAQUODDY REGION, NEW BRUNSWICK, FROM 1924 TO 1931
Authors: DAVIDSON VIOLA M.
Published: April 2011

Collections made during a period of seven and a half years (1924–1931) weekly at a station of 30 m. depth in the St. Croix estuary and monthly at a station of 90 m. depth in the Outer bay show three dominant species. Thalassiosira Nordenskiöldi dominates during spring at both stations, being definitely stenothermic, finding somewhat under 6 °C. most favourable, and disappearing at that temperature, which is reached earlier in the estuarine station. Chaetoceros debilis dominates in June at that station. It is most abundant at 10–12 °C., but occurs at lower as well as at higher temperatures up to the summer maximum of 15 °C. Biddulphia aurita, an early spring littoral species, reaches its maximum at about 2 °C., and disappears when the spring freshet takes place. The forms were arctic-neritic in spring (beginning with the melting of the snow), arctic and boreal in June and July, and temperate and oceanic in late summer and autumn.There is no apparent lack of nutrient salts, nitrates, phosphates and silica being reduced but never depleted. Light is an important factor, but its effect is not clearly distinguishable, the peak of diatom production being reached usually in June at the outer station and in late June or early July at the inner station, while July had the most effective light. Marked reduction in surface salinity from river discharge with consequent stability of the water precedes the spring maximum of phytoplankton, and to a less degree local rainfall of summer has a corresponding effect.
MATING IN THE AMERICAN LOBSTER
Authors: TEMPLEMAN W.
Published: April 2011

Observation of 24 cases of mating shows that usually it lasts about 60 seconds, and occurs between males with fairly hard shells and females with very soft shells (less than twelve hours after moulting). Correspondingly the males moult several weeks before the females. Of two males the one larger or superior in combat mates with the female. There may be repeated matings of one female with several males or of one male with several females. Preferably males should be slightly larger than females; if much larger mating rarely, if ever, occurs. At sexual maturity the two sexes are similar in size. Sperms retain their vitality in the female annulus for at least two years.
COD MOVEMENTS ON THE CANADIAN ATLANTIC COAST
Authors: McKENZIE R. A.
Published: April 2011

From 1925 to 1933 inclusive, during the summer season, 8,774 cod were tagged at eight points along the coasts of Nova Scotia and Prince Edward Island and eight per cent were recaptured during the following years, none after the sixth.Cod performing a restricted migration (less than 40 kilometres) were found to be in the majority off Halifax from July to September and off Shelburne in June and August in certain areas.Near Seal island in June, off Shelburne in July and September, and off Glace Bay in July and August, the majority of the cod were found to show orderly extended migrations. In the first two instances this movement was shoreward in the summer and seaward to about 130 metres in the early winter. The Glace Bay cod moved from the offshore banks just west of the Laurentian channel to the Cape Breton vicinity in the summer, returning early in the winter.A small percentage of the various stocks of cod performed roving migrations.The complete forsaking of the Cape Breton district for the offshore banks in the winter is attributed to the unfavourable ice cold water, while south-westward of Canso the movement off shore is thought to be caused by the very warm water inshore in the autumn and continued through the influence of the cold inshore waters several months later.As they grow older, the Shelburne cod remain progressively a little farther off shore when they move to shoal water each summer.
The Effects of Freezing on Marine Bacteria.: I. Quantitative Studies.
Authors: Hess Ernest
Published: April 2011

When marine bacteria were exposed to a moderate freezing temperature, −16 °C., for short periods, sea-water offered greater protection than broth media or distilled water. Reduction in number of bacteria was least severe in broth media of optimum salt-concentration and hydrogen ion concentration. During freezing in distilled water, transfer of bacteria from the crystallizing portion to the liquid part occurred. Old strains were more resistant to freezing, and previous cultivation at −3° produced more resistant strains. A higher percentage of cells were killed by freezing at lower freezing temperatures, by prolonged freezing, rapid freezing and repeated freezing. In truly super-cooled sea-water higher percentage reduction occurred than in frozen sea-water at −6.5° and −10°.
Digestion and Digestive Enzymes in the Herring (Clupea harengus L.)
Authors: Battle Helen I.
Published: April 2011

Crustacean food is partially broken down and digested in the caecum of the stomach of the herring. It becomes more finely divided in the pyloric sac and consists of an oily chyme, intermingled with chitin, mucus and bacterial clumps in the pyloric caeca and intestine. The acidic condition of the gastric contents is probably instrumental in the reddening of chitinous food in the tract. Pepsin from the stomach and trypsin from the pyloric caeca increase in digestive power over a temperature range from 2.4 to 37.5 °C. The stomach secretes a protease (pepsin), a weak amylase, and possibly a weak lipase. The pyloric caeca secrete a strong protease (trypsin), a strong amylase, and a lipase rendered active by bile. The intestinal mucosa exhibits lipolytic and amylolytic ferments, while the bile has some amylolytic properties.
The Function of the Claspers and Clasper-Glands in the Skate
Authors: Friedman M. H. F.
Published: April 2011

The clasper is erected by powerful adductor muscles as well as by vascular dilatation and is used as an organ of intromission. The gland secretes simultaneously from all its papillae a fluid which washes sperm down the clasper-tube into the female's cloaca. A centre for clasper erection exists in the cord between spinal nerves 48 to 50. In a spinal male tapping on the anal region causes a reflex erection of the claspers. Adrenaline apparently lowers the stimulus threshold for clasper erection.
The Reduced Strychnine Method for Determining Nitrates in Sea Water
Authors: Riddell William A.
Published: April 2011

A satisfactory procedure for the estimation of the dissolved nitrates in the waters of the strait of Georgia is described involving the use of a Duboscq colorimeter. Seven ml. of sample and reagent plus 3 drops of concentrated hydrochloric acid develop a satisfactory colour. A large number of small glass vials are used in place of the regular Duboscq cups. Standards are prepared from random samples of sea water. The proportionality between colour developed and nitrate concentration is practically linear up to 4.8 mg. of NO3 ion per litre but the factor is not 1. This necessitates an appreciable correction for all observed concentrations which differ greatly from that of the comparison standard.
The Number of Vertebrae in Trout (Salmo)
Authors: Mottley C. McC.
Published: April 2011

The European species of Salmo have fewer vertebrae than those from western North America, the mean values of two of each group as reared at the Cowichan hatchery being found to be: salar 59.0, trutta 58.3, gairdnerii 63.5, clarkii 62.5. Hatchery-reared gairdnerii were usually found to be different from those of the natural environment as well as varying with different experimental conditions, and even differed from their own parents, this seeming on the whole to be related to the temperature during development. A correlation was found between the length of the fish and the number of vertebrae. Caution is suggested in the use of the character for identifying populations of Salmo.