Showing papers in "Canadian Journal of Fisheries and Aquatic Sciences in 1994"
TL;DR: Wetlands were found to be important sources of methyl mercury to the boreal forest ecosystem, and mass-balance estimates indicated that purely upland catchments and lakes were sites ofmethyl mercury retention or demethylation, while catchments with wetland areas were Sites of net methyl mercury production.
Abstract: Wetlands were found to be important sources of methyl mercury to the boreal forest ecosystem. Yields of methyl mercury were about 26–79 times higher from wetland portions of catchments (1.84–5.55 m...
536 citations
TL;DR: Temporal changes in demography, population sustainability, and harvest rates support the hypothesis that overexploitation precipitated the commercial extinction of northern cod, Gadus morhua, off N... as mentioned in this paper.
Abstract: Temporal changes in demography, population sustainability, and harvest rates support the hypothesis that overexploitation precipitated the commercial extinction of northern cod, Gadus morhua, off N...
529 citations
TL;DR: This work found substantial movement of trout in streams in Colorado and Wyoming using two-way weirs and radio telemetry and showed that movement was important in the response of the trout population to habitat enhancement.
Abstract: Gerking (1959 Biol Rev 34: 221–242) proposed a theory about the restricted movement of stream fishes that may be considered a paradigm in salmonid biology The restricted movement paradigm (our
509 citations
TL;DR: It is recommended that F40% be adopted as a target fishing mortality rate when the S–R relationship is unknown and that threshold levels of biomass be related to the estimated or assumed degree of density dependence in the S-R relationship.
Abstract: Relationships between various biological reference points (BRPs) used to define thresholds and targets of fisheries management strategies were examined for a range of combinations of life history c...
394 citations
TL;DR: It is suggested that chlorophyte dominance in hypertrophic shallow lakes is attributable to continuous input of nutrients and carbon from the sediment and exte...
Abstract: Phytoplankton dominance (as biomass) by heterocystous cyanobacteria, nonheterocystous cyanobacteria, and chlorophytes was studied along a trophic gradient (0.011–2.2 mg P∙L−1) by analyzing regularl...
346 citations
TL;DR: The trophic structure of pelagic communities in glaciated regions is highly variable due to restricted dispersal of glacial relict taxa and recent species introduction.
Abstract: The trophic structure of pelagic communities in glaciated regions is highly variable due to restricted dispersal of glacial relict taxa and recent species introduction. Much of the between-lake var...
274 citations
TL;DR: To test the hypothesis that the elemental fingerprint of the otolith nucleus could serve as a natural marker of fish hatched at different sites, Atlantic cod otoliths collected from five spawning grounds in the northwest Atlantic were tested for differences in elemental and isotopic composition.
Abstract: Trace element incorporation into fish otoliths varies among samples collected at different sites. If otolith elemental composition (the elemental "fingerprint") somehow reflects the characteristics...
236 citations
TL;DR: Channel morphology and habitat characteristics of stream segments draining unharvested old-growth forests were compared with those from streams within intensively and moderately logged basins to conclude that simple counts of instream LWD and channel units (habitat types) are not useful as management objectives.
Abstract: Channel morphology and habitat characteristics of stream segments draining unharvested old-growth forests were compared with those from streams within intensively and moderately logged basins. Site...
219 citations
TL;DR: A lacustrine IBI was developed that was 12 metrics of three broad types: species composition, trophic composition, and abundance and condition, and several biomass metrics were adopted to accommodate the large size range of lentic fishes.
Abstract: Karr's Index of Biotic Integrity (IBI) approach provides a biological measure of ecosystem health using a wide spectrum of metrics which can be extracted from fish catch data obtained using standardized methods. Extensive electrofishing surveys of littoral fish assemblages, conducted in three Great Lakes' Areas of Concern, provided the basis for developing a lacustrine IBI that was 12 metrics of three broad types: (i) species composition, (ii) trophic composition, and (iii) abundance and condition. In contrast with lotic IBIs where diversity and abundance metrics have mostly been used, several biomass metrics were adopted to accommodate the large size range of lentic fishes. The variability of repeated measures was low enough to allow valid testing of intertransect differences with three to five samples per transect. Comparisons among survey areas showed significant differences consistent with the varying levels of ecosystem degradation. Analyses of mean IBI values with measures of submerged vegetation de...
217 citations
TL;DR: The cloning and characterization of 64 microsatellite sequences from Atlantic cod, Gadus morhua were reported, with the most significant difference between microsatellites from teleost fishes and mammals being the propensity of the former to be of greater length.
Abstract: Microsatellites, in particular (dG-dT)n and (dG-dA)n dinucleotide repeats, are abundant and display a high degree of length polymorphism and heterozygosity in eukaryotic genomes. Here, we report th...
214 citations
TL;DR: An objective method for identifying associations between environmental (habitat) conditions and the distributions of marine fishes using survey data is presented and the null hypothesis of a random association between fish distribution and habitat conditions is tested.
Abstract: We present an objective method for identifying associations between environmental (habitat) conditions and the distributions of marine fishes using survey data. The method tests the null hypothesis...
TL;DR: Greater adult divergence from the wild state was observed in multigeneration sea-ranched coho salmon, suggesting that evolutionary changes may accumulate with time.
Abstract: We quantified divergence in phenotype of sea-ranched, farmed, and wild Atlantic salmon (Salmo salar) of a common genetic stock (River Imsa, Norway). These first-generation fish were also contrasted...
TL;DR: In this paper, the authors explored the chemical and ecological factors that determine the bioaccumulation of radiocesium in fishes, and found that the fish bioaccume of 137C by fish was a negative function of both dissolved potassium and suspended sediment concentration, and a positive function of temperature.
Abstract: Although many measurements have been made on radiocesium levels in water and aquatic biota, no agreement has been reached regarding the factors affecting bioaccumulation of these radionuclides. With monitoring data from countries that operate nuclear facilities and data from the primary literature, we explored the chemical and ecological factors that determine the bioaccumulation of radiocesium. Using log–linear regression we found that the bioaccumulation of 137Cs by fish was a negative function of both dissolved potassium and suspended sediment concentration, and a positive function of temperature. Important ecological factors were the trophic level of the fish (piscivores bioaccumulate more than plank-tivores and benthivores), and the length of the food chain as reflected by the ratio of piscivore yield relative to net primary production. Fish from softwater drainages, which make up a large portion of northern Europe and Canada, are more vulnerable to radiocesium contamination than fish from hardwater ...
TL;DR: Four potential causes of a drastic decline in juvenile American eels, Anguilla rostrata, recruiting to Lake Ontario (81-fold decline from 1985 to 1992) and in juvenile eel dens...
Abstract: We critically review four potential causes of a drastic decline in juvenile American eels, Anguilla rostrata, recruiting to Lake Ontario (81-fold decline from 1985 to 1992) and in juvenile eel dens...
TL;DR: A general framework for developing sequential fishery models and estimating model parameters from available data is presented, which generalizes the conventional definition of state space model to include nonlinear equations with nonnormal error.
Abstract: A sequential fisheries model relates observed data to the biological dynamics of an underlying stock. Either model component, dynamic or observational, can be subject to statistical variation. Current fisheries literature includes models with (1) variable dynamics and no observation error, (2) deterministic dynamics and observations subject to measurement error, and (3) combined dynamic and measurement variability. This paper presents a general framework for developing sequential fishery models and estimating model parameters from available data. The framework encompasses most traditional stock assessment models and suggests new, potentially useful extensions. It generalizes the conventional definition of state space model to include nonlinear equations with nonnormal error. The paper rigorously compares two paradigms (KF: Kalman filter, EV: errors in variables) used for parameter estimation. Each paradigm is formulated in both frequentist and Bayes contexts, where Bayes is shown to be most appropriate fo...
TL;DR: This paper presents a meta-analyses of eight fisheries management practices in the Northern Hemisphere over a 25-year period (1995-2009) that shows clear trends in harvests and in particular in the performance of four of the five major harvesting policies.
Abstract: Scientific advice to fishery managers needs to be expressed in probabilistic terms to convey uncertainty about the consequences of alternative harvesting policies (policy performance indices). In most Bayesian approaches to such advice, relatively few of the model parameters used can be treated as uncertain, and deterministic assumptions about population dynamics are required; this can bias the degree of certainty and estimates of policy performance indices. We reformulate a Bayesian approach that uses the sampling/importance resampling algorithm to improve estimates of policy performance indices; it extends the number of parameters that can be treated as uncertain, does not require deterministic assumptions about population dynamics, and can use any of the types of fishery assessment models and data. Application of the approach to New Zealand's western stock of hoki (Macruronus novaezelandiae) shows that the use of Bayesian prior information for parameters such as the constant of proportionality for acou...
TL;DR: Periodic increments within the squid statolith microstructure are now routinely used to obtain individual age estimates, and there is now potential to use image analysis systems for increment counts and for width analysis of increments.
Abstract: Periodic increments within the squid statolith microstructure are now routinely used to obtain individual age estimates. Validation and culture studies have shown that statolith increments (similar...
TL;DR: The computational burden can be reduced substantially by analytically integrating over at least two "nuisance parameters" that occur in most assessment models: the observation error variance and the catchability coefficient.
Abstract: The Bayes posterior probability distribution is a powerful way to represent uncertainty in fisheries stock assessments, and can be calculated for key population and policy parameters of practically...
TL;DR: Sampling at the index station revealed that the proportion of live unionids declined from 53% in September 1989 to 17% in May–June 1990 and to 0% inSeptember 1990: this 100% mortality coincided with heavy infestation by zebra mussels.
Abstract: Unionid bivalves and attached epizoic zebra mussels (Dreissena polymorpha) were collected at one index station in 1989, 1990, and 1991 and at 17 stations in 1991 in offshore waters of western Lake Erie of the Laurentian Great Lakes. Sampling at the index station revealed that the proportion of live unionids declined from 53% in September 1989 to 17% in May–June 1990 and to 0% in September 1990: this 100% mortality coincided with heavy infestation by zebra mussels. Quantitative sampling with a Ponar grab at the 17 stations in 1991 revealed a widespread and dramatic reduction in unionid populations. In 1982, five unionid species occurred at 35% of the stations at a density of 4/m2, whereas in 1991, no live unionid species were found. Qualitative sampling with an epibenthic sled at the 17 stations in 1991 yielded only 4 live specimens of 2 species (Amblema plicata plicata and Fusconaia flava) and 187 dead specimens of 10 species. These and other results indicate that unionid populations are being negatively ...
TL;DR: Differences in zooplankton size among lakes could differentially affect foraging success of larval fishes, in particular, systems with small zoopLankton may represent ideal foraging environments for gizzard shad whereas lakes with large zoop lankyton may favor larval bluegill.
Abstract: Small gape of zooplanktivorous larval fish limits their prey size; yet, within constraints set by gape, zooplankton size eaten influences larval growth and ultimately survival. To determine if optimal zooplankton size varied among fish species with different gapes, we conducted foraging trials with larval bluegill (Lepomis macrochirus, 10-26 mm TL) and gizzard shad (Dorosoma cepedianum, 18-31 mm TL). Larvae (n = 10) fed for 1 h on zooplankton assemblages that varied in size, after which all larvae and remaining zooplankton were preserved. Larval gape was measured; both larval gut contents and available zooplankton were quantified. Bluegill, the large-gaped species, fed on larger zooplankton than did gizzard shad with similar gapes. Further, larger bluegill fed on progressively larger zooplankton whereas all gizzard shad ate small prey (<0.60 mm). As available zooplankton size increased, bluegill prey size increased whereas gizzard shad consistently selected small prey. Therefore, differences in zooplankton size among lakes could differentially affect foraging success of larval fishes. In particular, systems with small zooplankton may represent ideal foraging environments for gizzard shad whereas lakes with large zooplankton may favor larval bluegill. If differential larval foraging translates to differential growth and survival, zooplankton size could influence recruitment success and ultimately fish community composition.
TL;DR: The theory and practice of community-based self-management and government-community co-management is examined in this paper in terms of the potential of these management systems to address some of the major problems of the world.
Abstract: The theory and practice of community-based self-management and government–community co-management is examined in terms of the potential of these management systems to address some of the major biol...
TL;DR: It is shown that spatially uniform changes in abundance can affect catchability given certain models for the distribution of fishing effort, but that this effect is slight compared with the effect of changes in the spatial spread of fish distribution.
Abstract: Catchability to commercial fisheries has been predicted to be density dependent due to density-dependent variation in stock area. Previous studies have used indices of stock area based on threshold...
TL;DR: Premanipulation concentrations of fossil pigments from green algae and filamentous cyanobacteria increased 4- to 10-fold in response to eutrophication of Lake 227 in the Experimental Lakes Area, Ontario.
Abstract: Fossil pigments from annually laminated sediments were calibrated with coeval phytoplankton data (1970–1989) from experimentally eutrophied Lake 227 in the Experimental Lakes Area, Ontario. Concentrations of ubiquitous pigments (β-carotene, pheophytin a) were correlated to total algal biomass standing crop (r = 0.56–0.65; P < 0.01) during the ice-free seasons, but not to carbon fixation or water-column chlorophyll (Chl). Indicator pigments were correlated to ice-free season algal biomass for cyanobacteria (echinenone, aphanizophyll) and chlorophytes (lutein–zeaxanthin, pheophytin b)(r = 0.53–0.55, P < 0.05), weakly correlated for cryptophytes (alloxanthin, α-carotene; r = 0.32–0.40, P < 0.10), but were uncorrelated for chrysophytes and diatoms (fucoxanthin, Chl c) or dinoflagellates (peredinin). Premanipulation concentrations of fossil pigments (nmol pigment∙(g organic matter)−1) from green algae and filamentous cyanobacteria (myxoxanthophyll) increased 4- to 10-fold in response to eutrophication of Lake ...
TL;DR: Density was positively linked with temperature and negatively correlated with river velocity and turbidity, and diversities in littoral and pelagic areas were not different, but densities were higher nearshore (mostly copepods and cladocerans); rotifers were usually more common in the main channel.
Abstract: Ohio River Zooplankton were collected monthly or quarterly for 1 yr from littoral and pelagic (main channel) areas in three navigation pools (constricted and floodplain) with four intrapool locations (lower pool and above, below, and within major tributaries). Total densities were minimal (1.64/L) when discharge and turbidities peaked (December–April) but were relatively high otherwise (21.63/L). Seasonal rises in rotifer density preceded increases in cladocerans and copepods; rotifers were nearly twice as abundant as cladocerans and copepods. Diversity (species richness) was not correlated with temperature, velocity, or turbidity. Density was positively linked with temperature and negatively correlated with river velocity and turbidity. Diversities in littoral and pelagic areas were not different, but densities were higher nearshore (mostly copepods and cladocerans); rotifers were usually more common in the main channel. Neither proximity to low-head navigation dams nor channel morphology had detectable ...
TL;DR: It is determined with power analysis that IBI can distinguish between five and six nonoverlapping categories of biotic integrity based on a model that includes the effects of measurement error, variability of fish assemblages through time, and statistical interaction of location and time.
Abstract: We determined the statistical properties of the index of biotic integrity (IBI) from electrofishing samples collected from Ohio streams. Although IBI is widely used to evaluate the condition of water resources by biologists and resource managers, expanding its role as a regulatory tool depends on statistical validation of its precision and power. We addressed these issues by constructing an additive variance model for IBI and testing the assumptions of that model directly with a bootstrap resampling algorithm and simulations using field data. Statistical properties of IBI supported the use of standard analysis techniques such as ANOVA for hypothesis testing. We determined with power analysis that IBI can distinguish between five and six nonoverlapping categories of biotic integrity based on a model that includes the effects of measurement error, variability of fish assemblages through time, and statistical interaction of location and time. We conclude that IBI is an effective monitoring tool that can be u...
TL;DR: The results indicate that rearing cod at intermediate salinities, such as would occur in estuaries or coastal regions, could confer an advantage for cod aquaculture.
Abstract: Growth rates of Atlantic cod (Gadus morhua) were measured under different salinity conditions to test the hypothesis that growth would be best in an isosmotic environment. The results of two experi...
TL;DR: It is found that the most important factor affecting ΔIBD was whether the population remained large after supplementation ceased, and the absolute number of wild adults taken for broodstock had a stronger influence on Δ IBD than did the proportion of the population sampled.
Abstract: We simulated some of the genetic consequences of temporarily using captive broodstocks to supplement Pacific salmon (Oncorhynchus spp.) populations. Results were summarized in terms of the paramete...
TL;DR: This paper describes some of the ways that the uncertainty in fisheries scientific advice has been communicated to managers for different fisheries in the United States in the past several years.
Abstract: This paper describes some of the ways that the uncertainty in fisheries scientific advice has been communicated to managers for different fisheries in the United States in the past several years D
TL;DR: It was found that Sr/Ca ratios in Otolith primordia of fish of known anadromous origin were significantly higher than those in otolith primORDia ofFish of known resident origin, however, variation among samples was associated with differences in chemistry of the freshwater environments.
Abstract: We used a wavelength dispersive microprobe to describe patterns in otolith microchemistry of sockeye salmon (Oncorhyncbus nerka). Patterns in Sr/Ca ratios in transects across otoliths were consistent with changes in environmental chemistry associated with life history. The patterns we observed were consistent with those described for other salmonids. We found that Sr/Ca ratios in otolith primordia of fish of known anadromous origin were significantly higher than those in otolith primordia of fish of known resident origin. However, variation among samples was associated with differences in chemistry of the freshwater environments. These differences could confound attempts to discriminate sympatric resident and anadromous forms in lakes where Sr/Ca ratios are high. Samples used to discriminate origin of emigrants from Redfish Lake, Idaho, confirmed the presence of both resident and anadromous fish, but the two groups were not clearly resolved. Otolith microchemistry has the potential to determine the parent...
TL;DR: Analyses of the relationships between total phosphorus (TP) and chlorophyll a (Chl) among a large number of temperate lake ecosystems having contrasting herbivore communities and thermal stratification reveal that systems lacking large Daphnia (SH systems) exhibit four times more Chl yields than systems having large LH systems in oligotrophic as well as eutrophic and hypereutrophic systems.
Abstract: Analyses of the relationships between total phosphorus (TP) and chlorophyll a (Chl) among a large number of temperate lake ecosystems having contrasting herbivore communities and thermal stratifica...