Showing papers in "Canadian Journal of Fisheries and Aquatic Sciences in 1999"
TL;DR: A fluorometric method is presented that gives precise measurements of ammonium over a wide range of concentrations and salinities emphasizing submicromolar levels and not only solves analytical problems but also substantially simplifies sample collection and preservation.
Abstract: The accurate measurement of ammonium concentrations is fundamental to understanding nitrogen biogeochemistry in aquatic ecosystems. Unfortunately, the commonly used indophenol blue method often yie...
1,227 citations
TL;DR: It is found that the number of spawners produced per spawner each year at low populations and the maximum annual reproductive rate is relatively constant within species and that there is relatively little variation among species.
Abstract: We examine a database of over 700 spawner-recruitment series to search for parameters that are constant, or nearly so, at the level of a species or above. We find that the number of spawners produced per spawner each year at low populations, i.e., the maximum annual reproductive rate, is relatively constant within species and that there is relatively little variation among species. This quantity can be interpreted as a standardized slope at the origin of a spawner-recruitment function. We employ variance components models that assume that the log of the standardized slope at the origin is a normal random variable. This approach allows improved estimates of spawner-recruitment parameters, estimation of empirical prior distributions for Bayesian analysis, estimation of the biological limits of fishing, calculation of the maximum sustainable yield, and impact assessment of dams and pollution.
583 citations
TL;DR: The range of information available to coastal Newfoundland fishers was identified, to see if it could be quantified, and to explore its potential for reconstructing trends within fisheries, describing ways to access the large reservoir of information held by fishers and the use of several cross-checks to identify consistent patterns.
Abstract: Fishers have detailed knowledge of their resources, their environment, and their fishing practices that is rarely systematically collected. We conducted three types of interviews with coastal Newfo...
383 citations
TL;DR: Fluctuations in Pacific salmon abundance in this century were synchronous with large fluctuation in climate in the Pacific, suggesting that a common event may cause the regime shifts.
Abstract: Large fluctuations in the trends of Pacific salmon production in this century have been linked to trends in climate in the Pacific that are in turn associated with climate trends throughout the Nor...
348 citations
TL;DR: Norwegian coastal (NC) and northeast Arctic (NA) Atlantic cod larvae were reared on live zooplankton to investigate temperature- and size-specific growth and a stock-specific difference in mean weight at age was observed, with NC growing better than NA.
Abstract: Norwegian coastal (NC) and northeast Arctic (NA) Atlantic cod (Gadus morhua) larvae were reared on live zooplankton to investigate temperature- and size-specific growth. Larval and juvenile growth ...
303 citations
TL;DR: Variability in the recruitment of fish has been attributed to either changes in the environment or variations in the size of reproductive stocks, and the effects of environment and stock changes are disentangling.
Abstract: Variability in the recruitment of fish has been attributed to either changes in the environment or variations in the size of reproductive stocks. Disentangling the effects of environment and stock ...
292 citations
TL;DR: It is hypothesized that concentration of the fish and fishery led to extreme hyperstability in the CPUE-abundance relationship, and CPUE was related to abundance at the local scales of a fishing set (local acoustic density) but not to abundance in regional or stock scales.
Abstract: Misinterpretations of elevated catch-per-unit-effort (CPUE) in the northern cod (Gadus morhua) fishery contributed to overestimations of stock size, inflated quotas, and unsustainable fishing morta...
274 citations
TL;DR: For example, twenty giant bluefin tuna were captured in September and October 1997 and tagged and released with pop-up satellite tags programmed to jettison from March through July, 1998 as mentioned in this paper.
Abstract: Twenty giant bluefin tuna were captured in September and October 1997 and tagged and released with pop-up satellite tags programmed to jettison from March through July, 1998. Seventeen tags success...
266 citations
TL;DR: It is found that salmonid spawning distributions track channel slope distributions in several west-slope Pacific Northwest watersheds, implying that spatial differences in channel processes influence community structure in these rainfall-dominated drainage basins.
Abstract: Consideration of fundamental channel processes, together with map-based and field investigations, indicates that stream channel type influences salmonid spawning distributions across entire channel networks and salmonid abundance within channel reaches. Our analysis suggests that salmonid spawning patterns in mountain drainage basins of the Pacific Northwest are adapted to, among other things, the timing and depth of channel bed mobility. We hypothesize that because the bed of pool-riffle and plane-bed reaches scours to a variable fraction of the thickness of alluvium, survival to emergence is favored by either burying eggs below the annual scour depth or avoiding egg burial during times of likely bed mobility. Conversely, annual mobility of all available spawning gravel in steeper step-pool and cascade channels favors either adaptations that avoid egg burial during times of likely bed mobility or selection of protected microhabitats. Consistent with these expectations, we find that salmonid spawning distributions track channel slope distributions in several west-slope Pacific Northwest watersheds, implying that spatial differences in channel processes influence community structure in these rainfall-dominated drainage basins. More detailed field surveys confirm that different channel types host differential use by spawning salmonids and reveal finer-scale influences of pool spacing on salmonid abundance.
265 citations
TL;DR: The rate of advance of a front was related to the biomass of urchins; fronts did not advance below a threshold biomass of ~2 kg·m-2.25 m2 at both a wave-exposed site and a sheltered site in Nova Scotia over 3.5 years.
Abstract: We measured the rate of advance of urchin (Strongylocentrotus droebachiensis) feeding aggregations (fronts) as they destructively grazed kelp beds (Laminaria longicruris) at both a wave-exposed sit...
252 citations
TL;DR: Experimental testing of the suggested mechanisms responsible for the dome-shaped prey vulnerability function and whether a prey refuge affected the form of this function suggested that prey mortality was dome shaped for large and medium predators but decreased monotonically with prey size for small predators.
Abstract: Body size is known to play a crucial role in predator-prey interactions. For a given predator size, it has been suggested that prey mortality should be a dome-shaped function dependent on prey body size. In this study, we experimentally tested (i) the suggested mechanisms responsible for the dome-shaped prey vulnerability function and (ii) whether a prey refuge affected the form of this function. As prey, we used young-of-the-year Eurasian perch (Perca fluviatilis), and as predator, larger Eurasian perch. The prey mortality as a function of prey size was dome shaped for large and medium predators but decreased monotonically with prey size for small predators. Capture success of predators decreased monotonically with increasing prey size and was lower for small predators. In refuge trials, the mortality of prey declined monotonically with prey size for all predator sizes. Refuge use of prey increased with the sizes of both prey and predator. Our results suggest that the hypothesized dome-shaped relationshi...
TL;DR: By constructing equations that describe the combined effects of light and turbidity on reaction distances, this work can begin to model prey detection capabilities of piscivores at any depth at any time of day in natural environments.
Abstract: Most studies on visual foraging by fish have focused on reaction distances to invertebrate prey; however, these acuity-based results considerably overestimate reaction distances of piscivores to pr...
TL;DR: Four preservation methods were tested on the carbon and nitrogen isotopic composition of the muscle tissue of juvenile winter flounder and the tails of mud shrimp and formalin, formalin/EtOH, and saturated mercuric chloride solution produced significant increases in δ15N...
Abstract: When animal tissues are prepared for stable isotope ratio analysis, they may or may not be treated with acid prior to analysis to remove carbonates and are loaded into tin or silver weigh boats for...
TL;DR: Data is presented on Arctic char (Salvelinus alpinus) in Icelandic lakes exhibiting a variable degree of phenotypic and genotypic segregation, suggesting a role for trophic adaptation as a driving force in morph segregation.
Abstract: Resource polymorphism has been proposed as an important phase of diversification and speciation in vertebrates. Studies of fish in young lakes of the Northern Hemisphere indicate variably advanced ...
TL;DR: Diatom assemblages were selected as indicators of lake condition and to assess historical lake water quality changes in 257 lakes in the northeastern United States as mentioned in this paper, and the "top" (surface sediments, pr
Abstract: Diatom assemblages were selected as indicators of lake condition and to assess historical lake water quality changes in 257 lakes in the northeastern United States The "top" (surface sediments, pr
TL;DR: Chinook salmon receiving conspecific stimuli showed higher levels of several antipredator behaviors compared with chinook Salmon receiving green swordtail extracts, and the two groups of chinook salmon that were tested 2 days later with cutthroat trout stimulus alone spent more time motionless.
Abstract: The present study examined the effects of chemical antipredator conditioning on antipredator behavior and the relative effects of antipredator conditioning and seminatural rearing environments on postrelease survival of chinook salmon (Onocrhynchus tshawytscha). Hatchery-reared juvenile chinook salmon were exposed to extracts from conspecific tissue or to comparable stimuli from green swordtail (Xiphophorus helleri). These "injured fish" stimuli were paired with water that contained the odour of predatory cutthroat trout (Oncorhynchus clarki). Chinook salmon receiving conspecific stimuli showed higher levels of several antipredator behaviors compared with chinook salmon receiving green swordtail extracts. When the two groups of chinook salmon were tested 2 days later with cutthroat trout stimulus alone, the chinook salmon that had originally received injured conspecific stimuli paired with cutthroat trout odour spent more time motionless than chinook salmon that had received green swordtail stimuli and cu...
TL;DR: The ease with which Bayesian nonlinear state-space models can now be used for practical fisheries stock assessment is illustrated using Gibbs sampling via BUGS, a freely available software package that automates the hitherto tedious calculation of the full conditional posterior distributions.
Abstract: This paper illustrates the ease with which Bayesian nonlinear state-space models can now be used for practical fisheries stock assessment. Sampling from the joint posterior density is accomplished ...
TL;DR: It is shown that fertilization may be a limiting factor in some exploited populations when distances separating spawning individuals are too large and recruitment failures reported for South Australian populations of H. laevigata have occurred when densities fell below ca.0.3 animals·m-2.
Abstract: A combination of laboratory and field experiments with the commercial abalone species Haliotis laevigata showed that fertilization may be a limiting factor in some exploited populations when distan...
TL;DR: A redistribution of fishing effort among alternative fisheries or area will result in a redistribution of Fishing effort amongAlternative fisheries or areas under regulations and changes in market and environmental conditions.
Abstract: Regulations and changes in market and environmental conditions that change the profitability of one fishery or area will result in a redistribution of fishing effort among alternative fisheries or ...
TL;DR: In this article, the authors investigated carbon dynamics in the water column and CO2 and CH4 exchange across the air-water interface in four closed-basin lakes in northern Wisconsin: two with clear, low dissolved organic carbon (DOC) waters and two bog lakes with stained, high DOC waters.
Abstract: We investigated carbon dynamics in the water column and CO2 and CH4 exchange across the air-water interface in four closed-basin lakes in northern Wisconsin: two with clear, low dissolved organic carbon (DOC) waters and two bog lakes with stained, high-DOC waters. Clear-water lakes quickly became undersaturated following ice-out and remained undersaturated until fall turnover. Bog lakes were supersaturated in CO2 throughout the ice-free season, although surface CO2 concentrations dropped sharply following ice-out and increased again during autumn turnover. Differences in seasonal patterns of CO2 were attributed to morphometry and the timing and intensity of mixing events. Ice-free season fluxes of CO2 were 6.7 and 10.0 mol·m-2 in the bog lakes and 1.2 and 0.09 mol·m-2 in the clear-water lakes. Fluxes of CH4 were significant only immediately after ice-out and during autumn turnover and were <0.4 mol·m-2 in the bog lakes and <0.05 mol·m-2 in the clear-water lakes. Compared with changes in carbon pools in th...
TL;DR: Individual differences in Atlantic cod reproductive behaviour at a field-reported spawning density under experimental conditions are quantified.
Abstract: We quantified individual differences in Atlantic cod, Gadus morhua, reproductive behaviour at a field-reported spawning density under experimental conditions. Marked individuals (nine females, seve...
TL;DR: The rapid influx of Ponto-Caspian species into the Great Lakes warrants further study including identification of source populations, mechanisms of dispersal, impacts on recipient ecosystems, and efficacy of ballast water exchange programs.
Abstract: Cercopagis pengoi, a waterflea native to the Ponto-Caspian region, was discovered during 1998 in Lake Ontario. Individuals were found throughout the lake during summer snagged on sportfishing lines...
TL;DR: This work examines the basis for consideration of Bayesian probability networks for surface water quality assessment and prediction with a focus on Bayes nets.
Abstract: It is a common strategy in surface water quality modeling to attempt to remedy predictive inadequacies by incorporating additional mechanistic detail into the model. This approach reflects the reas...
TL;DR: This work uses the statistical technique of meta-analysis to quantitatively evaluate the results of 27 independent studies that examine various life history responses of Daphnia to kairomones released from three common predators: Chaoborus, Notonecta, and planktivorous fish.
Abstract: Daphnia respond to kairomones from a variety of predators by altering their morphology, behavior, and life history. I use the statistical technique of meta-analysis to quantitatively evaluate the results of 27 independent studies that examine various life history responses of Daphnia to kairomones released from three common predators: Chaoborus, Notonecta, and planktivorous fish. Daphnia exhibit a fundamentally different set of life history responses to Chaoborus (delayed reproduction, decreased size of first clutch, slight tendency toward increased size at maturity) than they do to Notonecta and fish (earlier reproduction, increased clutch size, smaller size at maturity). These opposite responses appear to be related to different patterns of prey selection exhibited by the predators. Food level does not affect the life history responses of Daphnia to Chaoborus kairomones; however, the length of exposure to these kairomones does influence the degree of delay in reproduction. In addition, changes in size a...
TL;DR: A general quantitative framework to estimate movement and mortality of fish populations from tagging data is described, represented by an advection-diffusion process, which is the population equivalent of individual movement based on a biased random walk.
Abstract: The mobility of fish populations is often ignored in population dynamics models. However, in many cases (with tunas being a prime example), movement and spatial heterogeneity may be striking features of the fish populations and their exploitation. We describe a general quantitative framework to estimate movement and mortality of fish populations from tagging data. Movement is represented by an advection-diffusion process, which is the population equivalent of individual movement based on a biased random walk. Finite difference approximations for solving the partial differential equation are provided. The model is parameterized by assuming that movement parameters are homogeneous within specified geographical regions and seasons, that fishing mortality is proportional to fishing effort, and that natural mortality is constant over area and time. All model parameters are estimated simultaneously by maximum likelihood. The method is illustrated by application to skipjack tuna (Katsuwonus pelamis) in the weste...
TL;DR: The trophic isotope fractionation of mysids, in response to a change in the isotopic composition in their diet, was examined in the laboratory and may form a basis for diet selection in muscle, exuviae, and feces.
Abstract: The trophic isotope fractionation of mysids, in response to a change in the isotopic composition in their diet, was examined in the laboratory. Field-caught Mysis mixta and Neomysis integer had sim...
TL;DR: Energetic costs of contaminant-induced changes in metabolism and food consumption can be integrated with a bioenergetics model to demonstrate biological significance of chemical exposure in a natural environment.
Abstract: We present empirical support for a conceptual framework in which chemical contaminants are considered as sources of physiological stress to fish. Physiological stress was quantified in terms of ene...
TL;DR: This study shows that fasting affects the stable-isotope ratios (δ13C and δ15N) and tissue concentrations of protein and lipid in anadromous Atlantic salmon during their spawning migration along the Exploits River, Newfoundland, in 1996.
Abstract: Anadromous Atlantic salmon (Salmo salar) were collected during their spawning migration along the Exploits River, Newfoundland, in 1996 and analyzed for stable-isotope ratios (δ13C and δ15N) and tissue concentrations of protein and lipid. Fish became progressively more 13C enriched during the spawning migration (about -24 to -19), and the degree of enrichment was dependent on tissue type (red muscle: +4.1, liver: +2.6, white muscle: +1.3). Only liver showed consistent changes in δ15N, as overwintering kelts (13.5 ± 0.8) were about +2 more enriched than upstream migrants (11.4 ± 1.5). Isotopic enrichment in migrating salmon appeared to result from mobilization, reorganization, and catabolism of stored lipid and protein reserves associated with the cessation of feeding upon entering freshwater. The most significant correlations existed between lipid content and δ13C in red muscle (r2 = 0.67) and protein content and δ15N in liver (r2 = 0.32). This study shows that fasting affects the stable-isotope ra...
TL;DR: The aim of this paper is to compare methodologies that have been used in studies involving intraspecific variability in the locomotor performance of fishes with respect to the promising nature of initial studies incorporating individual variability in fish performance.
Abstract: Physiological research of locomotor performance in fishes has traditionally adopted an approach in which the mean performance of a number of fish was considered "real" and variation around the mean...
TL;DR: To test the hypothesis that N:P supply ratios influence phytoplankton species composition, mesocosms at one pelagic and two littoral sites within the Experimental Lakes Area, Ontario, were fertilized for 10-12 weeks with similar amounts of P but different amounts of N.
Abstract: To test the hypothesis that N:P supply ratios influence phytoplankton species composition, and particularly that cyanobacteria are favored by a low ratio, mesocosms at one pelagic and two littoral ...