bluuebunny/crossref_metadata_2025 huggingface dataset:
An optimisation model of the diel vertical migration of northern krill (Meganyctiphanes norvegica) in the Clyde Sea and the Kattegat
Authors: Tarling Geraint , Burrows Michael , Matthews Jack , Saborowski Reinhard , Buchholz Friedrich , Bedo Alain , Mayzaud Patrick
Published: April 2011

An optimisation model was developed to examine the effect of predation risk and environmental conditions on the diel vertical migration (DVM) of adult northern krill (Meganyctiphanes norvegica). Model predictions were compared in two locations with contrasting environmental conditions, the Clyde Sea and the Kattegat. The model was constructed from a combination of parameterised functions and empirical field data obtained during summer conditions. Parameter matrices were set up to cover the entire water column over a 24-h period. The first matrix contained values for "net energy gain," which incorporated empirical data on temperature-dependent respiration, copepod and phytoplankton abundance, and a functional response model for feeding rate. The second matrix expressed the risk of encountering a generalised visual (fish) predator as a function of light levels. The optimisation procedure sought a path through depth and time such that the energy gain was equal to the amount necessary to grow, produce eggs, and moult, while the risk of predation was minimised. The model predicted DVM in both the Clyde Sea and the Kattegat. Sensitivity analyses showed that the predicted DVM pattern was mainly driven by food and predation risk, with temperature effects on metabolic costs having a minor effect.
Demography and life cycle of Antarctic krill, Euphausia superba, in the Indian sector of the Southern Ocean: long-term comparison between coastal and open-ocean regions
Authors: Pakhomov E A
Published: April 2011

Size/age composition and reproductive status of Antarctic krill, Euphausia superba, in the central part of the Indian sector of the Southern Ocean, e.g., the Cooperation Sea (Prydz Bay region) and the Cosmonaut Sea, during austral summers 1977-1990 were summarized to estimate growth rates, longevity, reproduction, recruitment, life span, and mortality rates. The life span of Antarctic krill exceeds 5 years in both the Cosmonaut and Cooperation seas. The age composition of the southern and northern groupings differs markedly, with substantial reduction in numbers of early age groups in the northern grouping. Long-term observations of spawning success, recruitment, and age composition suggest that a self-sustained grouping of krill persists in the Cooperation Sea south of the Antarctic Divergence. However, periodic gene flow via recruits from surrounding regions most probably accounts for the lack of spatial genetic differences between the Cooperation Sea and adjacent areas, thus preventing the establishment of an isolated subpopulation in the region investigated. The major factor responsible for the substantial interannual variability in krill dynamics appears to be macroscale oceanographic and atmospheric circulations, which determine a level of environmental isolation of the Cooperation Sea from adjacent waters.
The cumulative effects of climate warming and other human stresses on Canadian freshwaters in the new millennium
Authors: Schindler D W
Published: April 2011

Climate warming will adversely affect Canadian water quality and water quantity. The magnitude and timing of river flows and lake levels and water renewal times will change. In many regions, wetlands will disappear and water tables will decline. Habitats for cold stenothermic organisms will be reduced in small lakes. Warmer temperatures will affect fish migrations in some regions. Climate will interact with overexploitation, dams and diversions, habitat destruction, non-native species, and pollution to destroy native freshwater fisheries. Acute water problems in the United States and other parts of the world will threaten Canadian water security. Aquatic communities will be restructured as the result of changes to competition, changing life cycles of many organisms, and the invasions of many non-native species. Decreased water renewal will increase eutrophication and enhance many biogeochemical processes. In poorly buffered lakes and streams, climate warming will exacerbate the effects of acid precipitation. Decreases in dissolved organic carbon caused by climate warming and acidification will cause increased penetration of ultraviolet radiation in freshwaters. Increasing industrial agriculture and human populations will require more sophisticated and costly water and sewage treatment. Increased research and a national water strategy offer the only hope for preventing a freshwater crisis in Canada.
Use of fatty acids as dietary indicators in northern krill,Meganyctiphanes norvegica, from northeastern Atlantic, Kattegat, and Mediterranean waters
Authors: Virtue Patti , Mayzaud Patrick , Albessard Eric , Nichols Peter
Published: April 2011

Fatty acids of the triacylglycerol (TG) and polar lipid (PL) fractions were compared from northern krill, Meganyctiphanes norvegica, sampled in the Clyde Sea in the Atlantic, the Kattegat at the Alkor Deep, and the Ligurian Sea in the Mediterranean. Possible biotransformations of fatty acids in the food chain were examined in mixed zooplankton and krill faecal material from the Ligurian Sea and Kattegat. The Ligurian Sea population was distinguished from the Kattegat and Clyde Sea populations in terms of both TG and PL fatty acid profiles. The Kattegat and Clyde Sea populations were separated from each other in terms of their PL fatty acid profiles only. Krill sampled in winter from all sites had significantly higher levels of 20:1 and 22:1 fatty acids in the TG fraction (9-17%) than krill sampled in summer (1-10%). These fatty acids in particular indicate carnivorous dietary input, as they are found in high levels in copepods, which are the major prey species of M. norvegica. Levels of 22:6(n-3) were significantly higher than 20:5(n-3) in Ligurian krill, which, together with other specific marker fatty acids, suggested a predominance of dinoflagellates and other nondiatom species in their diet. TG fatty acids in Kattegat and Clyde Sea krill indicate a predominance of diatoms in the diet.
Divergence of brown trout (Salmo trutta) within glacial refugia
Authors: Sanz Núria , García-Marín José-Luis , Pla Carles
Published: April 2011

The Pleistocene glaciations produced a range of changes that affected the genetic population structure of fish species. Usually, studies focused on the population structure of species in postglacial recolonized areas and less attention was devoted to species differentiation within refuge areas. Allelic frequencies for 21 polymorphic protein-coding loci were compared among 25 collections within a northwestern Iberian glacial refuge of brown trout (Salmo trutta) using adjusted frequencies for nine populations to account for introgressions with exogenous hatchery fish. The high divergence observed (FST = 0.645) and geographical patterns of allelic variation are interpreted to reflect the existence of strong population structuring among native populations of this refuge. Four major geographic groups were defined within the region: (i) in the Tajo River, (ii) in the Duero River, (iii) in the Sil River, and (iv) among Cantabrian Sea flowing rivers including present anadromous populations. These gene pools have diverged genetically and ecologically in response to climatic oscillations. Anthropogenic effects on habitat and fish populations seriously compromise their future.
Krill and the unity of biology
Authors: Mangel Marc , Nicol Stephen
Published: April 2011

This supplement features some of the printed papers from the Second International Symposium on Krill (Santa Cruz, Calif., August 1999). Krill have long been recognized as key prey species for fish, birds, and marine mammals and as a target for fisheries in both hemispheres. However, the study of krill can contribute in many other areas of biology. Krill are an excellent model system for studies of growth and maturity, for connections between theory, experiment, and observation, and for tests of evolutionary theory in the field. Krill are also ideal model organisms for studying the interaction between environmental and organismal variability. Because they are widely distributed but only moderately speciose, the study of krill can also shed light on the relationship between abundance and range. The study of krill is an inherently interdisciplinary field, crossing boundaries and using a combination of oceanography, biochemistry, physiology, evolution, and ecology to understand krill and their role in the ecosystem.
Age-specific natural mortality rates of adult Pacific herring (Clupea pallasi) from southern British Columbia
Authors: Tanasichuk R W
Published: April 2011

I used data for over 665 000 Pacific herring (Clupea pallasi) seined or gillnetted in southern British Columbia between 1951 and 1998 to estimate age- and year-specific adult natural mortality rates. Apparent sampling bias precluded using data collected before 1980. The instantaneous natural mortality rate is an increasing exponential function of age. Surplus energy requirements for gonad recrudescence appear to cause the death of adult herring.
Using natural strontium isotopic signatures as fish markers: methodology and application
Authors: Kennedy Brian P , Blum Joel D , Folt Carol L , Nislow Keith H
Published: April 2011

To distinguish Atlantic salmon (Salmo salar) populations in tributaries of the Connecticut River, we studied the incorporation and stability of Sr isotopes in juvenile salmon. We established the geologic basis for unique isotopic signatures in 29 salmon sites. Stream-specific Sr isotopic ratios (87Sr/86Sr) were found in calcified tissues of salmon parr within 3 months of stocking. We found little seasonal variation in the Sr signatures of stream water or fish tissue. There were no significant differences among the Sr signatures of otoliths, scales, and vertebrae. For mature salmon raised under constant conditions, 70% of the Sr isotopic signature in calcified tissues was derived from food sources. We developed a criterion for identifying moving fish based upon the isotopic variability of genetically marked fish. Applying this criterion to our streams, 7% of the fish in our study had incorporated Sr from multiple streams. Strontium isotopes distinguished all 8 regions in the White River basin and 7 of the 10 regions in the West River basin. When watersheds are considered together, Sr isotopes differentiated 11 unique signatures from 18 regions. We conclude that Sr isotopes are an effective marking tool and discuss ways in which they can be combined with other marking techniques over larger spatial scales.
Testing mechanistic explanations of observed correlations between environmental factors and marine fisheries
Authors: Gargett A E , Li M , Brown R
Published: April 2011

Based on observed correlations, marine fisheries are often hypothesized to depend on environmental factors. Since correlations are unreliable as a predictive tool, it is desirable to seek mechanistic explanations for observed correlations. This paper considers methods available for testing such mechanistic explanations. As a specific example, we consider the optimal stability window, proposed as a mechanistic explanation of observed correlations between the survival of North Pacific salmon stocks and the state of the atmosphere over the North Pacific in winter, as applied to the coastal waters and fisheries of southern British Columbia, Canada.
The Precautionary Approach and risk management: can they increase the probability of successes in fishery management?
Authors: Hilborn Ray , Maguire Jean-Jacques , Parma Ana M , Rosenberg Andrew A
Published: April 2011

Considerable progress has been made in the implementation of the Precautionary Approach to the protection of fish stocks, but applying the Precautionary Approach to the protection of fishing communities lags considerably. The principle of intergenerational equity, one of the main tenets of the Precautionary Approach, and the principle of sustainable utilization both imply that the Precautionary Approach should explicitly incorporate the protection of fishing communities, not only the resources they depend on. Risk assessment aims primarily at evaluating the consequences of various harvest strategies in terms of probabilistic statements about future trends in yields, biomass, and dangers to the stock, while risk management involves finding and implementing management policies, strategies, and tactics that reduce the risk to the communities exploiting them. Not all fishery management approaches deal equally well with risk, with some compounding rather than reducing risk. Portfolio management, whereby fishing enterprises have the ability to choose among a diverse portfolio of harvestable resources, would mitigate against the risk of fluctuations in the abundance, availability, or price of individual species. Although much remains to be achieved in better assessing risk, fishery management agencies should immediately implement risk management.
Marine protected areas in Canada  implications for both conservation and fisheries management
Authors: Jamieson Glen S , Levings Colin O
Published: April 2011

Legislated marine "protected" areas are now widely distributed throughout tropical and temperate waters, but the nature of human activities actually restricted in any area varies. This ambiguity about what "protected" means has resulted in contradictory claims as to both the benefits and costs of marine protected areas. Here, we give our perspective on the current status of marine resource protection in Canada in general and British Columbia in particular. We first describe and discuss the history of Canadian marine protected areas established to date. Many areas are claimed to be protected, with little understanding by either the general public or even most marine resource experts as to what human activities are actually regulated by legislative designations. Second, we present an overview of biological reasons and objectives for marine protected areas, followed by a review of both the conservation and fisheries management effects and implications resulting from effective renewable resource protection. Finally, we propose a unique qualitative scheme for classifying and describing marine protected areas of different types to determine relative measures of protection.
Grazing dynamics of Euphausia spinifera in the region of the Subtropical Convergence and the Agulhas Front
Authors: Perissinotto Renzo , Mayzaud Patrick , Labat Jean-Philippe , Razouls Suzanne
Published: April 2011

The feeding ecophysiology of the subtropical euphausiid Euphausia spinifera was investigated in the Indian sector of the Southern Ocean during JanuaryFebruary 1999. Gut pigment levels varied from 1.7 to 40.6 ng chlorophyll a (Chl a) equiv.·individual1 in adults and from 0.3 to 9.3 ng Chl a equiv.·individual1 in juveniles. Highest levels were observed at the Subtropical Convergence (Chl a concentrations 0.40.6 µg·L1) and minima in the area north of the Agulhas Front (Chl a concentrations 0.20.3 µg·L1). Gut evacuation rates ranged between 0.59 and 0.96·h1. Gut pigment destruction levels were among the highest ever recorded in euphausiids, with 94.298.5% of total pigments ingested converted to nonfluorescing end products. Size-selectivity experiments with natural phytoplankton showed that E. spinifera ingests mainly cells in the 0.7- to 20-µm range. The grazing dynamics of this important species are compared with those of subantarctic (Euphausia vallentini) and Antarctic krill (Euphausia superba). Individual ingestion rates, estimated from the autotrophic component of its diet (2.784.46 µg Chl a equiv.·individual1·day1), were just sufficient to account for respiratory requirements. While E. spinifera is clearly able to ingest large amounts of heterotrophic prey, it is not known to what extent these contribute to its total energy budget.
Seston supply to sea scallops (Placopecten magellanicus) in suspended culture
Authors: Pilditch C A , Grant J , Bryan K R
Published: April 2011

The filtration activity of dense aggregations of bivalves can locally reduce the concentration of seston, potentially limiting production. Under these conditions, the currents that supply seston cannot offset ingestion by the bivalves and the carrying capacity is exceeded. We conducted a field and modelling study to examine factors affecting seston supply to a culture of suspended sea scallops (Placopecten magellanicus) in Whitehaven Harbour, Nova Scotia. Even though seston flux to the scallops was reduced by 40% due to the attenuation of flow by culture gear, a reduction in seston concentration was not observed. The field data were then used to parameterize a quasi two-dimensional advection-diffusion model that quantified the relationship between the tidally driven seston supply and consumption by scallops. The model predicted a minimal reduction in seston concentration (<5%) within the lease (80 × 50 m), consistent with field observations. However, expanding the lease to occupy the area available for cultivation (1000 × 250 m) reduced the seston concentration in the centre of the lease by 20-50%, potentially limiting growth. Modelling results emphasized that by altering the lease geometry (lease width to length ratio), the supply of seston can be optimized.
Floodplain rearing of juvenile chinook salmon: evidence of enhanced growth and survival
Authors: Sommer T R , Nobriga M L , Harrell W C , Batham W , Kimmerer W J
Published: April 2011

In this study, we provide evidence that the Yolo Bypass, the primary floodplain of the lower Sacramento River (California, U.S.A.), provides better rearing and migration habitat for juvenile chinook salmon (Oncorhynchus tshawytscha) than adjacent river channels. During 1998 and 1999, salmon increased in size substantially faster in the seasonally inundated agricultural floodplain than in the river, suggesting better growth rates. Similarly, coded-wire-tagged juveniles released in the floodplain were significantly larger at recapture and had higher apparent growth rates than those concurrently released in the river. Improved growth rates in the floodplain were in part a result of significantly higher prey consumption, reflecting greater availability of drift invertebrates. Bioenergetic modeling suggested that feeding success was greater in the floodplain than in the river, despite increased metabolic costs of rearing in the significantly warmer floodplain. Survival indices for coded-wire-tagged groups were somewhat higher for those released in the floodplain than for those released in the river, but the differences were not statistically significant. Growth, survival, feeding success, and prey availability were higher in 1998 than in 1999, a year in which flow was more moderate, indicating that hydrology affects the quality of floodplain rearing habitat. These findings support the predictions of the flood pulse concept and provide new insight into the importance of the floodplain for salmon.
A fisheries management strategy robust to ignorance: rotational harvest in the presence of indirect fishing mortality
Authors: Myers Ransom A , Fuller Susanna D , Kehler Daniel G
Published: April 2011

We develop a simple theoretical model of yield and spawning stock biomass per recruit for the American sea scallop (Placopecten magellanicus), which appears to have high indirect fishing mortality when harvested with dredges, i.e., mortality caused by the act of fishing that does not result in landings. The age at and degree to which individuals are affected by the indirect mortality are unknown, and it does not appear possible to develop a robust harvest strategy with yearly harvests unless indirect fishing mortality is well quantified. We show that there could be substantial benefits to a rotational harvest strategy for sessile species with high indirect fishing mortality. First, the strategy appears to be robust to ignorance about indirect fishing mortality and results in equal or better yields than a yearly harvest across a wide range of indirect fishing mortalities. Second, under most conditions, a higher spawning stock biomass is maintained. Third, rotational management is more easily enforced, as it does not require specifying a narrow range of fishing mortality in order to maximize yield.
Detection of population trends in threatened coho salmon (Oncorhynchus kisutch)
Authors: Shea Katriona , Mangel Marc
Published: April 2011

Populations of coho salmon (Oncorhynchus kisutch) in California are listed as threatened under the U.S. Endangered Species Act. Such listings refer to adult populations, but often, juvenile life history stages are censused, so it is important to understand what affects the relationship between true adult and observed juvenile numbers. We present models to address how observational uncertainty, census length, and autocorrelation in vital rates affect our ability to observe trends. We ask two questions about our ability to detect declines in one life history stage from censuses of another. First, given an observed decline in parr numbers, what is the chance that this reflects a decline in adults? Second, given that adult numbers are declining, what is the chance that we see that decline in parr? Our results indicate that statistical power decreases with increasing observational uncertainty and decreasing census lengths and demonstrate how these two parameters interact. Power increases as the level of autocorrelation in mortality rates increases. Management recommendations include obtaining more accurate estimates of autocorrelation in mortality and of observational uncertainty.
Validation of three back-calculation models by using multiple oxytetracycline marks formed in the otoliths and scales of bluegill × green sunfish hybrids
Authors: Klumb Robert A , Bozek Michael A , Frie Richard V
Published: April 2011

We assessed the accuracy of the FraserLee, biological-intercept, and Weisberg back-calculation models to estimate growth from otoliths and scales of laboratory-reared juvenile bluegill × green sunfish hybrids (Lepomis macrochirus × Lepomis cyanellus). Hybrid sunfish were injected three times with oxytetracycline hydrochloride at 90-day intervals to mark bony structures, creating simulated annuli for model validation. Back-calculated lengths (BCLs) with otoliths were generally less accurate than scales for all three models. Errors ranged from 8.2 to 7.8% for the FraserLee model, from 8.0 to 8.3% for the biological-intercept model, and from 6.5 to 14.3% for the Weisberg model. For all three models, there was no significant difference in BCLs using left or right otoliths, and BCLs using the FraserLee and biological-intercept models were not significantly different from each other. In contrast with otoliths, all three models produced accurate BCLs from scales; errors ranged from 4.3 to 0.1%. For juvenile hybrid sunfish, we recommend using scales for back-calculation of growth. The FraserLee (with zero intercept) and biological-intercept models produced the most accurate BCLs from otoliths. However, due to potential decoupling of otolith and body growth, caution should be exercised when estimating juvenile hybrid sunfish growth from otoliths.
IV: REPORT ON THE FLORA OF ST. ANDREWS, N.B.
Authors: FOWLER LL. D. JAMES
Published: April 2011

not available
VI: THE PAIRED FINS OF THE MACKEREL SHARK
Authors: PRINCE E. E. , MacKay Dr. A. H.
Published: April 2011

not available
Physical and biological processes over a submarine canyon during an upwelling event
Authors: Allen S E , Vindeirinho C , Thomson R E , Foreman M GG , Mackas D L
Published: April 2011

Short, shelf-break canyons are shown to have a substantial influence on local water properties and zooplankton distribution. Barkley Canyon (6 km long) off the west coast of Vancouver Island was extensively sampled in July 1997 and found to have water property and current patterns similar to those observed over Astoria Canyon (22 km long) off the coast of Washington State. Results from Barkley Canyon reveal that the canyon influence can occur very close to the surface (at the thermocline depth of 10 m) and that, near the canyon rim, the stretching vorticity generated over the canyon is strong enough to produce a closed cyclonic eddy of sufficient strength to trap deep passively drifting tracers. Most zooplankton species are advected by the currents; those near the ocean surface pass over the canyon, while those at depth are advected toward the coast. Euphausiids (Euphausia pacifica and Thysanoessa spinifera), the strongest swimming zooplankton collected in the 1997 study, were most prevalent in the closed eddy region near the head of the canyon. The observed aggregation of these animals appears to be linked to their ability to remain at specific depths combined with advection by horizontally convergent flows in the eddy.
III: ON THE FAUNA OF THE ATLANTIC COAST OF CANADA.: An Introductory Report
Authors: STAFFORD M.A., PH.D. J.
Published: April 2011

not available
V: THE DIATOMACEÆ OF CANSO HARBOUR, NOVA SCOTIA.: A PROVISIONAL LIST.
Authors: Mackay Dr. A. H.
Published: April 2011

not available
VI: REPORT ON THE FLORA OF CANSO, NOVA SCOTIA.
Authors: FOWLER LL.D., F.R. PROF. JAMES
Published: April 2011

not available
VIII: REPORT ON THE MARINE POLYZOA OF CANSO, N.S.
Authors: Cornish B.A. George A.
Published: April 2011

not available
IX: NOTES ON THE FISHES OF CANSO.
Authors: CORNISH B.A. GEORGE A.
Published: April 2011

not available
Calculation of biomass trend, exploitation rate, and surplus production from survey and catch data
Authors: Hilborn Ray
Published: April 2011

If survey data and historical catches are available, it is possible to estimate the history of surplus production from a fishery as long as the scalar between the survey and absolute biomass can be estimated. Alternative hypotheses about present stock size correspond to alternative hypotheses about the scalar, so that by specifying an estimate of the current stock size or exploitation rate, the entire trend of surplus production can be calculated. An example, using monkfish (Lophius americanus) in the eastern United States, is given that shows quite robust conclusions to alternative assumptions about current stock size, and the analysis suggests that the surplus production from monkfish has been the highest during the period of lowest stock size.
A numerical model of flow modification induced by suspended aquaculture in a Chinese bay
Authors: Grant Jon , Bacher Cedric
Published: April 2011

A finite element circulation model of flow was constructed for Sungo Bay, China, a site of dense cultivation of both marine bivalves and kelp, to assess the magnitude of friction due to culture structure and its implications for particle exchange. In the model, parameterization of friction was modified to reflect the patterns of culture configuration in the bay and the results compared with the default case with no culture. Results of model output indicate that suspended aquaculture results in a 20% reduction in current speed in the main navigation channel and a 54% reduction in speed in the midst of a culture area. In the channel, reduced flow had little effect on tracer exchange under mid-ebb conditions, but the presence of culture structure caused a 41% decrease in exchange rate compared with the absence of culture. These results indicate that disregard for physical barriers associated with culture will result in a serious over estimation of the particle renewal term and thus an overestimation of carrying capacity. Further work is required to measure the characteristics of culture (spacing, length scale), quantify their magnitude of flow retardation in the field, and improve model parameterization of the frictional effects of various types of culture.
Application of a two-dimensional hydrodynamic reservoir model to Lake Erie
Authors: Boegman L , Loewen M R , Hamblin P F , Culver D A
Published: April 2011

The relative impacts of changes in nutrient loading and zebra mussel establishment on plankton in large lakes are strongly influenced by hydrodynamics, yet adequately modelling the temporal-spatial complexity of physical and biological processes has been difficult. We adapted a two-dimensional public domain model, CE-QUAL-W2, to test whether it could provide a hydrodynamically accurate simulation of the seasonal variation in the vertical-longitudinal thermal structure of Lake Erie. The physical forcing for the model is derived from surface meteorological buoys and measurements of precipitation, inflows, and outflows. To calibrate and validate the model, predictions were compared with an extensive set of field data collected during May through September 1994. The model accurately predicted water-level fluctuations without adjustment. However, significant modifications to the eddy coefficient turbulence algorithm were required to simulate acceptable longitudinal currents. The thermal structure was accurately predicted in all three basins, even though this laterally averaged model cannot simulate Coriolis effects. We are currently extending the model's water-quality module to include the effects of nutrient loading and zebra mussels on the plankton.
Dreissena distribution in commercial waterways of the U.S.: using failed invasions to identify limiting factors
Authors: Allen Yvonne C , Ramcharan Charles W
Published: April 2011

Preventing the introduction of an invasive species and managing the ecological and economic effects of successful invasions often rely on accurate predictions of the potential distribution of the species in its new habitat. Instances of failed invasion can highlight factors other than dispersal that limit range expansion in an invasive species. The commercially available waterways (CAWs) of the U.S. are a network of interconnected rivers that support a regular traffic of commercial and maintenance vessels. As such, they are at extremely high risk of infestation from Dreissena, yet not all the rivers are infested. We used traffic, water chemistry, and impoundment characteristics of the rivers in this system to develop a set of logistic-regression models to predict the occurrence of Dreissena. Four single variable models correctly classified 20 out of 24 (83%) river systems. The best two-variable models had only one misclassified river, for an overall accuracy of 96%. Among rivers to which Dreissena has successfully dispersed, permanent populations are most likely to establish in systems that have moderate ionic strength and that also have some impoundment areas to increase long-term population persistence. We use this hierarchy of factors to extend predictions to four systems that currently lack the high dispersal intensity of the CAWs.
Implications of protracted recruitment for perception of the spawnerrecruit relationship
Authors: Sheehy M RJ
Published: April 2011

In European lobster, Homarus gammarus, wide growth variation means that annual recruitment to a fishery (individuals reaching legal size in the same year) consists of at least six year-classes (individuals hatching in the same year). In this paper, a simple simulation analysis is used to explore the effects of uncertainty about the specifics of this protracted recruitment pattern on the way that we perceive the spawnerrecruit relationship. In the simulation, if the age range of recruits is underestimated or a simple correction for growth variation is applied by averaging numbers of recruits across years, a spawnerrecruit relationship with artefactual curvature and noise arises. Growth variability is typical in animal populations and problems with protracted recruitment may occur in any situation where recruitment is based on size. Asymptotic spawnerrecruit curves may not necessarily reflect density-dependent compensatory mortality and resilience to harvesting. The evidence presented here has important management implications for lobster and other exploited species.
Microsatellite evaluation of haddock (Melanogrammus aeglefinus) stocks in the northwest Atlantic Ocean
Authors: Lage Christopher , Purcell Maureen , Fogarty Michael , Kornfield Irv
Published: April 2011

The goal of this study was to gain insight about the impact of intensive fishing on a single haddock (Melanogrammus aeglefinus) stock, and examine the genetic structuring of spatially discrete spawning aggregations in the northwest Atlantic. We analyzed genetic change at four microsatellite loci for Georges Bank haddock over a 40-year time span in which significant changes in demographics and abundances have occurred in the population. Allelic diversities have changed little, indicating that, although the commercial fishery has collapsed, stock sizes have remained large enough to insulate against major reductions in genetic variation due to drift. Results indicate significant genetic divergence among decadally separated samples. Potential causes for these differences include admixture from other spawning regions, fluctuations in the effective number of spawners contributing to a single spawning event, drift, or a combination of these. Examination of discrete spawning aggregations from Georges Bank, Browns Bank, the Scotian Shelf, and Nantucket Shoals indicated significant differences among stocks. Genetic distance based measures supported the clustering of Scotian Shelf, Browns Bank, and Georges Bank haddock to the exclusion of Nantucket Shoals haddock. Haddock spawning on Nantucket Shoals may be genetically discrete from other haddock populations in the northwest Atlantic.
Analyses of length and age distributions using continuation-ratio logits
Authors: Rindorf Anna , Lewy Peter
Published: April 2011

Sampling of length and age distributions of catches is important for the assessment of commercially fished stocks. This paper presents a new method for statistical analyses and comparisons of length and age distributions based on generalised linear models of continuation-ratio logits. The method allows statistical testing of the effects of both continuous and discrete variables. Further, by utilising the smoothness of length and age distributions as a function of length, the method provides more accurate estimates of these distributions than traditional methods. The observations are assumed to be multinomially distributed, but cases in which the variance exceeds that of this distribution may also be analysed. The implementation of the method in existing statistical analysis software is straightforward and is demonstrated using length and age distributions of the lesser sandeel, Ammodytes marinus Raitt.
Productivity and survival rate trends in the freshwater spawning and rearing stage of Snake River chinook salmon (Oncorhynchus tshawytscha)
Authors: Petrosky C E , Schaller H A , Budy P
Published: April 2011

Stream-type chinook salmon (Oncorhynchus tshawytscha) populations in the Snake River (northwest United States) have declined dramatically since completion of the federal hydrosystem. Identifying the life stage that is limiting the survival of these stocks is crucial for evaluating the potential of management actions to recover these stocks. We tested the hypothesis that a decrease in productivity and survival rate in the freshwater spawning and rearing (FSR) life stage since completion of the hydropower system could explain the decline observed over the life cycle. The decline of chinook populations following completion of the hydrosystem was not accompanied by major survival changes in the FSR life stage. FSR productivity showed no significant decline, and the FSR survival rate decline was small relative to the overall decline. However, significant survival declines did occur in the smolt-to-adult stage coincident primarily with hydrosystem completion, combined with poorer climate conditions and possibly hatchery effects. Potential improvements in survival that occur only at the FSR life stage are unlikely to offset these impacts and increase survival to a level that ensures the recovery of Snake River stream-type chinook.
Offshore spawning and year-class strength of northern cod (2J3KL) during the fishing moratorium, 1994-1996
Authors: Anderson John T , Rose George A
Published: April 2011

Two new surveys have been conducted in recent years to assess the status of the northern cod (Gadus morhua) stock (2J3KL). An offshore acoustic survey in spring sampled concentrations of spawning adults and estimated potential fecundity. A pelagic juvenile fish survey carried out in late summer measured cod year-class strength prior to settlement. Spawning biomass of offshore cod decreased from 11 700 t in 1994 to 2000 t in 1995 to 900 t in 1996 with a corresponding decrease in eggs spawned. This decline was mirrored in the distribution and abundance of pelagic juvenile cod. Natural mortality estimated between the egg and pelagic juvenile stages increased from 0.068·day1 in 1994 to 0.084·day1 in 1995 to 0.112·day1 in 1996. The decline in year-class strength of cod appeared to result primarily from a reduction in the number of offshore spawners compounded by an increase in natural mortality during the egg and larval stages. The decline in spawners occurred 2 years after the implementation of a fishing moratorium and cannot be linked to fishing. The rapid decline in abundance of adult fish combined with increased natural mortality during the egg and larval drift is consistent with depensation.
Annual variation in size-selective mortality of Atlantic salmon (Salmo salar) fry
Authors: Good S P , Dodson J J , Meekan M G , Ryan D AJ
Published: April 2011

We investigated the size-selective mortality of Atlantic salmon (Salmo salar) fry during two consecutive summers that differed markedly in weather conditions. We sampled fry shortly after emergence in June and at the end of August to compare the distributions of back-calculated body size at hatching by examining otolith microstructure. Size-selective mortality was observed in both summers; however, the direction and strength of mortality differed. During the drought conditions of 1995, selective mortality was relatively weak and directed towards the smaller fry in the population. During the flood conditions of 1996, selective mortality was relatively strong and directed towards the larger fry of the same population. Interannual variability in size-selective mortality contributed to significant differences in the mean size of fry at the end of their first summer of life. Size-selective mortality rates estimated from the shifts in fish length at hatching observed during the first summer of life were comparable with published estimates of total mortality of Atlantic salmon fry, indicating that early mortality may be largely size selective. Mortality associated with hydroclimatic events can select against either small or large fish and is a key determinant of mean size attained by the end of the first summer of life.
Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island lakes (Nunavut, Canada) and reconstruction of summer water temperature
Authors: Joynt III Ernest H , Wolfe Alexander P
Published: April 2011

Diatoms from the surface sediments of 61 lakes on Baffin Island, Nunavut, were identified, enumerated, and interpreted quantitatively. The samples span a latitudinal transect from 62 to 74°N, reflecting climatic and vegetational gradients that range from low Arctic to transitional mid-Arctic to high Arctic. While the sampled lakes encompass both predominantly maritime and continental climatic regimes, sites have been deliberately restricted to basins in Precambrian crystalline terrain to mitigate the edaphic consequences of alkaline sedimentary bedrock. Canonical correspondence analysis, using forward selection and Monte Carlo permutation tests, identified pH, conductivity, summer lake water temperature, and mean annual air temperature as significant environmental controls over diatom assemblages. Using weighted-averaging regression and calibration, predictive models for these parameters have been developed. When applied to down-core assemblages, the summer lake water temperature model provides realistic reconstructions when compared with other paleoenvironmental records. Over the past 5000 years, the amplitude of reconstructed summer lake water temperature is on the order of 4.0°C, expressed primarily as progressive Neoglacial cooling culminating in the Little Ice Age. Diatom-inferred summer water temperatures have increased by 2.0°C in the past 150 years, again in agreement with independent paleoclimatic reconstructions.
Landscape variables influencing nutrients and phytoplankton communities in Boreal Plain lakes of northern Alberta: a comparison of wetland- and upland-dominated catchments
Authors: Prepas E E , Planas D , Gibson J J , Vitt D H , Prowse T D , Dinsmore W P , Halsey L A , McEachern P M , Paquet S , Scrimgeour G J , Tonn W M , Paszkowski C A , Wolfstein K
Published: April 2011

A review of headwater lakes in undisturbed watersheds on the Boreal Plain, with indirect gradient analyses of chemical data, indicated a clear separation between those in wetland-dominated watersheds (57100% wetland with variable proportions of bog, fen, swamp, and marsh cover) and those in upland-dominated watersheds (044% wetland cover). In the former, percentage wetland cover in the watershed was positively correlated with total phosphorus (TP, r2 = 0.78, primarily bog), total nitrogen (TN, r2 = 0.50), and dissolved organic carbon (DOC, r2 = 0.74) concentrations. Rich fens appeared to sequester both TP and TN. In upland-dominated lakes, the ratio of catchment area to lake volume (CA/LV) was the strongest watershed correlate of TP concentration (r2 = 0.56), whereas most limnetic nitrogen and DOC were generated in situ. Colour concentration, being highest in wetland lakes, was correlated with the ratio of isotopically defined effective drainage basin area to lake volume (eDBA/LV, r2 = 0.63). Drainage basin slope was only weakly associated with water quality, likely because of low topographic relief ([Formula: see text]11%). Higher Chlorophyta and Peridineae biomasses in wetland-dominated systems than in upland-dominated ones may coincide with greater NH4+ availability.
Sulfur burial in and loss from the sediments of Little Rock Lake, Wisconsin
Authors: Urban N R , Monte A E
Published: April 2011

Lake sediments often are regarded as accurate records of changes in climatic conditions, rates of atmospheric deposition of substances to the lake, or other processes occurring within lakes. In this study, the sedimentary record of sulfur was examined in Little Rock Lake, Wisconsin. This lake received experimental sulfate additions from 1985 through 1990, and a mass balance showed that 35% (425 kg) of experimental sulfur additions were buried in the sediments. Sediment cores collected before and after sulfur additions confirmed that burial of 180360 kg of sulfur occurred during the 6 years of experimental sulfur additions. However, cores collected in 1992 and 1996 contained less sulfur than cores taken in 1990 and suggested that sulfur incorporation in sediments is not permanent. To examine seasonal sulfur loss from sediments, sulfur inventories in the top 4 cm of sediments were measured in multiple cores before and after fall overturn. At water depths greater than 5 m, surface sediments retrieved after fall overturn had significantly less sulfur than did those collected before overturn. The small seasonal release from the sediments (25 kg S in 1996) might be caused by organic matter decomposition or sulfide oxidation.
A hierarchical Bayesian model for estimating historical salmon escapement and escapement timing
Authors: Su Zhenming , Adkison Milo D , Van Alen Benjamin W
Published: April 2011

In this paper, we present an improved methodology for estimating salmon escapements from stream count data. The new method uses a hierarchical Bayesian model that improves estimates in years when data are sparse by "borrowing strength" from counts in other years. We present a model of escapement and of count data, a hierarchical Bayesian statistical framework, a Gibbs sampling approach for evaluation of the posterior distributions of the quantities of interest, and criteria for determining when the model and inference are adequate. We then apply the hierarchical Bayesian model to estimating historical escapement and escapement timing for pink salmon (Oncorhynchus gorbuscha) returns to Kadashan Creek in Southeast Alaska.
Influence of sediment biofilm on the behaviour of aluminum and its bioavailability to the snail Lymnaea stagnalis in neutral freshwater
Authors: Ballance S , Phillips P J , McCrohan C R , Powell J J , Jugdaohsingh R , White K N
Published: April 2011

An important influence on the behaviour, bioavailability, and toxicity of Al in neutral freshwater is its ability to form complexes with organic material such as humic acids and extracellular polymeric substances (EPS). This paper examines the influence of EPS, secreted by a natural bacterial biofilm associated with a pebble substrate ("sediment biofilm") and by the snail Lymnaea stagnalis, on the behaviour of Al in the water column and its bioavailability to the snail. Both sediment biofilm and snails were a significant source of aqueous EPS. Added Al stimulated the production of EPS by the snail but not by bacterial biofilm. Repeated elevation of the concentration of Al in the water by 500 µg Al·L1 but not 100 µg Al·L1 over 10 days resulted in a progressive rise of Al in the water column in the absence but not in the presence of sediment biofilm. Up to 150 µg Al·cm2 was associated with the sediment biofilm, and we suggest that sediment is a significant "sink" for aqueous Al. EPS avidly binds colloidal Al, and we propose that the sediment biofilm is an important influence on the behaviour and bioavailability of Al in running waters when amounts of humic substances are low.
Metabolic enzyme activity during smolting in stream- and hatchery-reared Atlantic salmon (Salmo salar)
Authors: Leonard Jill BK , McCormick Stephen D
Published: April 2011

To evaluate the metabolic differences between Atlantic salmon (Salmo salar) parr and smolts and the effect of rearing environment, we examined metabolic enzyme activity in white muscle, liver, and heart in stream- and hatchery-reared juveniles. Spring increases in gill Na+,K+-ATPase (3.5-fold) and cardiosomatic index (3769%) and decreases in condition factor (~17%) occurred in smolts, but not in parr. White muscle phosphofructokinase (PFK) increased during spring and was 3.6-fold higher in smolts than in parr by late spring. There were seasonal increases in liver citrate synthase (CS) (~42%), liver β-hydroxyacyl-coenzyme A dehydrogenase (HOAD) (~60%), and heart CS (~23%) and decreases in liver lactate dehydrogenase (LDH) (~28%) in parr and smolts. Activity of liver HOAD was greater in stream-reared smolts (~18%) than in parr or hatchery smolts. Heart PFK activity increased during spring in wild-reared parr and smolts, while it decreased in hatchery-reared smolts. White muscle LDH and PFK increased earlier in spring in hatchery- than in stream-reared smolts. Our results suggest that increased heart size and high white muscle PFK occur during smolting and may be adaptive for downstream and ocean migration. Hatchery- and stream-reared Atlantic salmon differ in the timing of metabolic changes during smolting, which may impact their long-term survival.