Showing papers in "Canadian Journal of Fisheries and Aquatic Sciences in 2001"
TL;DR: This paper provides a summary of recent empirical and theoretical results concerning available methods and gives recommendations for their use in univariate and multivariate applications.
Abstract: The most appropriate strategy to be used to create a permutation distribution for tests of individual terms in complex experimental designs is currently unclear. There are often many possibilities, including restricted permutation or permutation of some form of residuals. This paper provides a summary of recent empirical and theoretical results concerning available methods and gives recommendations for their use in univariate and multivariate applications. The focus of the paper is on complex designs in analysis of variance and multiple regression (i.e., linear models). The assumption of exchangeability required for a permutation test is assured by random allocation of treatments to units in experimental work. For observational data, exchangeability is tantamount to the assumption of independent and identically distributed errors under a null hypothesis. For partial regression, the method of permutation of residuals under a reduced model has been shown to provide the best test. For analysis of variance, o...
1,240 citations
TL;DR: Otolith bio-chronologies have been linked with otolith chemistry as mentioned in this paper, allowing accurate estimates of age and growth at both the daily and the yearly scale, based on the successes of calcified structures as environmental proxies in other taxa.
Abstract: The chronological properties of otoliths are unparalleled in the animal world, allowing accurate estimates of age and growth at both the daily and the yearly scale. Based on the successes of calcified structures as environmental proxies in other taxa, it was logical that researchers should attempt to link otolith biochronologies with otolith chemistry. With the benefit of hindsight, this anticipation may have been naive. For instance, the concentrations of many elements are lower in the otolith than in corals, bivalves, seal teeth, or the other bony structures of fish, making them less than ideal for elemental analyses. Nevertheless, there is growing interest in the use of otolith chemistry as a natural tag of fish stocks. Such applications are directed at questions concerning fish populations rather than using the fish as a passive recorder of the ambient environment and do not rely upon any explicit relationship between environmental variables and otolith chemistry. The questions that can be addressed w...
970 citations
TL;DR: In this paper, the authors examine evidence for the structuring of fish communities from stream and lake systems and the roles of biotic, abiotic, and spatial factors in determining the species composition.
Abstract: We examine evidence for the structuring of fish communities from stream and lake systems and the roles of biotic, abiotic, and spatial factors in determining the species composition. Piscivory by fish is a dominant factor in both stream and lake systems whereas evidence for the importance of competition appears less convincing. Within small streams or lakes, the impact of predation may exclude other species, thereby leading to mutually exclusive distributions and strong differences in community composition. Within a geographic region, abiotic effects frequently dictate the relative importance of piscivory, thereby indirectly influencing the composition of prey species present. The spatial scale of studies influences our perceived importance of biotic versus abiotic factors, with small-scale studies indicating a greater importance of competition and large-scale studies emphasizing abiotic controls. The scale of the individual sites considered is critical because smaller systems have higher variability and ...
927 citations
TL;DR: It is shown that the risk of water quality degradation by Cyanobacteria blooms is more strongly correlated with variation in total P, total N, or standing algae biomass than the ratio of N:P.
Abstract: A controversial precept of aquatic ecology asserts that low ratios of nitrogen to phosphorus (N:P) lead to noxious and sometimes toxic blooms of Cyanobacteria. Cyanobacteria dominance is a major ri...
742 citations
TL;DR: The effects of climate change on Canadian water quality and water quantity are discussed in this article, where it is shown that increasing industrial agriculture and human populations will require more sophisticated and costly water and sewage treatment.
Abstract: 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.
659 citations
TL;DR: Comparing 297 series of catch-per-unit-effort (CPUE) and independent abundance data and using observation error and random effects models to test the hypothesis that CPUE is pro- portional to true abundance found strong evidence thatCPUE was most likely to remain high while abundance declines.
Abstract: We compiled 297 series of catch-per-unit-effort (CPUE) and independent abundance data (as estimated by research trawl surveys) and used observation error and random effects models to test the hypot...
621 citations
TL;DR: Results were consistent with the hypothesis that zebra mussels promoted blooms of toxic M. aeruginosa in Saginaw Bay, western Lake Erie, and other lakes through selective rejection in pseudofeces.
Abstract: Microcystis aeruginosa, a planktonic colonial cyanobacterium, was not abundant in the 2-year period before ze- bra mussel (Dreissena polymorpha) establishment in Saginaw Bay (Lake Huron) but became abundant in three of five summers subsequent of mussel establishment. Using novel methods, we determined clearance, capture, and assimilation rates for zebra mussels feeding on natural and laboratory M. aeruginosa strains offered alone or in combination with other algae. Results were consistent with the hypothesis that zebra mussels promoted blooms of toxic M. aeruginosa in Saginaw Bay, western Lake Erie, and other lakes through selective rejection in pseudofeces. Mussels exhibited high feeding rates similar to those seen for a highly desirable food alga (Cryptomonas) with both large (>53 m) and small ( 53 m) et de petites (<53 m) colonies d'une souche non-toxique et d'une souche toxique de laboratoire de M. aeruginosa, qui inhibent l'alimentation chez le zooplancton, les moules maintiennent des taux eleves d'alimentation, semblables a ceux que l'on observe lorsqu'on les nourrit d'une algue tres recherchee (Cryptomonas). Dans des experiences d'alimentation utilisant des souches naturelles de M. aeruginosa toxiques de la baie de Saginaw et du lac Erie et un isolat toxique du lac Erie, les moules presentent des taux de filtration reduits ou normaux et rejettent M. aeruginosa dans leurs pseudofeces. Ce rejet selectif depend de la presence de grandes colonies de souches toxiques «a gout desagreable» de M. aeruginosa qui peuvent etre eliminees facilement, alors que les petites algues appetissantes sont ingerees.
513 citations
TL;DR: The marine FA synthesis/transport cycle and traditional and nontraditional sources of EFA are reviewed and it is suggested that, while some traditional sources of marine oils are in steady decline, other sources hold great promise for maintaining access to EFA.
Abstract: Fatty acids (FA) are inextricably linked with key physiological and biochemical processes and are thus integral to proper ecosystem functioning. FA not biosynthesized effectively by animals are ter...
512 citations
TL;DR: A widely cited hypothesis in ecology is that species-rich communities are less vulnerable to invasion than species-poor ones, owing to competition for limiting resources (the "biotic resistance" hypothesis).
Abstract: A widely cited hypothesis in ecology is that species-rich communities are less vulnerable to invasion than species-poor ones, owing to competition for limiting resources (the "biotic resistance" mo...
511 citations
TL;DR: Risk of depensatory effects should be a major target of recruitment research, and management policies should aim for considerably higher spawning abundances than has previously been assumed necessary based on recruitment data collected during adult stock declines associated with fishery development.
Abstract: Large, dominant fish species that are the basis of many fisheries may be naturally so successful due partly to "cultivation effects," where adults crop down forage species that are potential compet...
494 citations
TL;DR: Evidence is provided 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 than adjacent river channels.
Abstract: 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 chinoo...
TL;DR: Tributary confluences are sites along a main channel where, because of the introduction of water and sediment, the water volume, bed sediment character, and water quality of the mainstream can be affected.
Abstract: Tributary confluences are sites along a main channel where, because of the introduction of water and (or) sediment, the water volume, bed sediment character, and water quality of the mainstream can...
TL;DR: The von Bertalanffy parame- ters asymptotic length and growth rate, and natural mortality and maximum age were used to de- scribe the life-history strategies of elasmobranch fishes and it was found that the M/k ratio in elasmOBranchs is significantly different from those for other fish and reptile taxa.
Abstract: Published life-history parameters for sharks, skates, and rays over a wide geographic range were used to develop predictive models to estimate parameters that are difficult to measure or have not b...
TL;DR: The mean trophic level (TL) of fish landed in fisheries on the east and west coasts of Canada is declining by 0.030.10·decade1, similar to global trends.
Abstract: The mean trophic level (TL) of fish landed in fisheries on the east and west coasts of Canada is declining by 0.030.10·decade1, similar to global trends. This finding is based on data from United Nations Food and Agriculture Organization and the Canadian Department of Fisheries and Oceans and other Canadian sources for the period 18731997. Significant rates of decline in mean TL were obtained even when key species Atlantic cod (Gadus morhua) on the east coast and Pacific herring (Clupea pallasi) and Pacific hake (Merluccius productus) on the west coast were omitted from the analysis. Fish taken in inland water fisheries did not exhibit a decline in mean TL. Two models were developed, based on length and age, respectively, for correcting TL estimates of individual species for the effects of changes in body size due to changes in fishing mortality. Both produced corrections that were small relative to changes in mean TL that resulted from changes in species composition of the catch over time. Overall...
TL;DR: One dominant mode of recent zooplankton variation was a 19901998 cumulative shift to a more "southerly" copepod and chaetognath fauna: order-of-magnitude declines in several species endemic to the Northeast Pacific continental shelf and order- of- magnitude increases of species endemic of the California Current.
Abstract: A 15-year zooplankton time series collected off southern Vancouver Island (4849°N) shows large interannual anomalies of biomass for most major zooplankton species. Variations within groups of ecol...
TL;DR: Thirty streams in western Oregon and Washington were sampled to determine the responses of juvenile salmonid populations to artificial large woody debris (LWD) placement and density response was correlated with the number of pieces of LWD forming pools during summer and total pool area during winter.
Abstract: Thirty streams in western Oregon and Washington were sampled to determine the responses of juvenile salmonid populations to artificial large woody debris (LWD) placement. Total pool area, pool number, LWD loading, and LWD forming pools were higher in treatment (LWD placement) than paired reference reaches during summer or winter. Juvenile coho salmon (Oncorhynchus kisutch) densities were 1.8 and 3.2 times higher in treated reaches compared with reference reaches during summer and winter, respectively. The response (treatment minus reference) of coho density to LWD placement was correlated with the number of pieces of LWD forming pools during summer and total pool area during winter. Densities of age-1+ cutthroat trout (Oncorhynchus clarki) and steelhead trout (Oncorhynchus mykiss) did not differ between treatment and reference reaches during summer but were 1.7 times higher in treatment reaches during winter. Age-1+ steelhead density response to treatment during summer was negatively correlated with incre...
TL;DR: The maximum isotopic turnover rate of channel catfish (Ictalurus punctatus) tissues is determined and this maximum rate is compared with that of I. furcatus captured in the field over the 3-month Alosa spawning run.
Abstract: In the tidal freshwaters of Virginia, U.S.A., the blue catfish (Ictalurus furcatus), an introduced piscivore, derives a significant proportion of its nutrition from spawning anadromous fish (genus ...
TL;DR: In this article, the authors used information on human populations and land uses within the watershed of Waquoit Bay, Cape Cod, Massachusetts, U.S.A., to model how nitrogen loads derived from atmospheric deposition, fertilizer use, and wastewater disposal have changed since the 1930s.
Abstract: Historical changes in land use on coastal watersheds have increased rates of land-derived nitrogen loading to estuaries and altered their biogeochemistry and food webs. We used information on human populations and land uses within the watershed of Waquoit Bay, Cape Cod, Massachusetts, U.S.A., to model how nitrogen loads derived from atmospheric deposition, fertilizer use, and wastewater disposal have changed since the 1930s. Nitrogen loading into Waquoit Bay more than doubled between 1938 and 1990. The predominant source of nitrogen added to the bay changed from atmospheric deposition to wastewater disposal during the 1980s, reflecting the increasing urbanization of Cape Cod. Larger nitrogen loads increased nitrogen concentrations in the water, altering the assemblage of primary producers and resulting in eutrophication of the estuary. Biomass of phytoplankton and macroalgae increased, and areal cover of eelgrass (Zostera marina) decreased, with increasing nitrogen load. An increase in nitrogen load from 15 to
TL;DR: Comparisons of seventh-generation farm Atlantic salmon with wild Atlantic salmon from the principal founder population of the farm strain suggested that environmental effects of culture override genetic effects as time in captivity increases, and domestication selection may alter reaction norms of farmed animals over environmental gradients and time.
Abstract: Artificial culture may relax the selective pressures from predators, thereby altering behavioural and heart rate responses to predation risk. Culture may also impose new selection that adapts fish ...
TL;DR: The principle of intergenerational equity 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.
Abstract: 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 commun...
TL;DR: The relative impacts of four factors, commercial exploitation, predation, food availability, and the physical environment, on the changes in capelin biology are discussed in the context of capelin as a single species and in thecontext of the ecosystem.
Abstract: Capelin (Mallotus villosus), an important forage and commercial fish in the Northwest Atlantic, has exhibited dramatic changes in its biology during the 1990s, coincident with extreme oceanographic...
TL;DR: 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.
Abstract: 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...
TL;DR: Coho movers were not smaller than nonmovers, as predicted based on assumptions that movement results from competitive exclusion, and Habitat units that coho left were smaller and shallower but lower in density than units where coho remained.
Abstract: Movements of juvenile coho salmon (Oncorhynchus kisutch), cutthroat trout (Oncorhynchus clarki clarki), and steelhead trout (Oncorhynchus mykiss) were studied by observations and recapture of marked individuals in three western Washington streams to test the hypotheses that few fish would move, downstream movement would predominate, movers would be initially smaller and grow slower after movement than residents, and habitat quality would influence movement. Contrary to predictions, from 28 to 60% of marked fish moved at least one habitat unit, and immigration of unmarked fish also indicated considerable movement. Upstream movement predominated but the stream with the step-pool/cascade channel type had fewer upstream movers and greater distances moved downstream. Coho movers were not smaller than nonmovers, as predicted based on assumptions that movement results from competitive exclusion. Habitat units that coho left were smaller and shallower but lower in density than units where coho remained. Thus, mov...
TL;DR: 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.
Abstract: 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 evaluat...
TL;DR: Investigation of food chain length and trophic position across sites affected by differing levels of anthropogenic activity indicated that δ15N was a valid descriptor of eutrophication at sites with low dissolved inorganic nitrogen concentrations.
Abstract: Stable nitrogen isotope ratios (δ15N) were measured in fish, mussel, and sediment samples taken from 17 small freshwater sites to examine food chain length and trophic position across sites affecte...
TL;DR: In this article, the authors collected water quality, land use, and aquatic macrophyte information from 62 coastal and inland wetlands in the Great Lakes basin and found that species richness and community structure of macrophytes were a function of geographic location and water quality.
Abstract: We collected water quality, land use, and aquatic macrophyte information from 62 coastal and inland wetlands in the Great Lakes basin and found that species richness and community structure of macrophytes were a function of geographic location and water quality For inland wetlands, the primary source of water quality degradation was inputs of nutrients and sediment associated with altered land use, whereas for coastal wetlands, water quality was also influenced by exposure and mixing with the respective Great Lakes Wetlands within the subbasins of the less de- veloped, more exposed upper Great Lakes had unique physical and ecological characteristics compared with the more developed, less sheltered wetlands of the lower Great Lakes and those located inland Turbid, nutrient-rich wetlands were characterized by a fringe of emergent vegetation, with a few sparsely distributed submergent plant species High- quality wetlands had clearer water and lower nutrient levels and contained a mix of emergent and floating-leaf taxa with a diverse and dense submergent plant community Certain macrophyte taxa were identified as intolerant of turbid, nutrient-rich conditions (eg, Pontederia cordata, Najas flaxilis), while others were tolerant of a wide range of condi- tions (eg, Typha spp, Potamogeton pectinatus) occurring in both degraded and pristine wetlands Resume : Des donnees recueillies sur la qualite de l'eau, l'utilisation des terres et les macrophytes aquatiques dans 62 terres humides des regions cotieres et interieures du bassin des Grands Lacs indiquent que la richesse specifique et la structure des communautes de macrophytes dependent de la situation geographique et de la qualite de l'eau Dans les terres humides interieures, la source principale de degradation de la qualite de l'eau est l'apport de nutriments et de sediments cause par les changements dans l'utilisation des terres, alors que, dans les terres humides cotieres, la qualite de l'eau est aussi influencee par le contact avec le Grand Lac adjacent et les melanges d'eau qui s'y produisent Les terres humides des sous-bassins des Grands Lacs d'amont, qui ont subi moins de developpement et qui sont plus expo- ses, possedent des caracteristiques physiques et ecologiques tout a fait particulieres, par comparaison avec les terres humides des Grands Lacs d'aval qui sont plus developpes et moins proteges, et les terres humides interieures Les terres humides turbides et riches en nutriments sont caracterisees par le developpement d'une ceinture de vegetation emergente et la presence sporadique de quelques plantes submergees Les terres humides de grande qualite possedent une eau plus claire, des concentrations plus faibles de nutriments et une combinaison de taxons de plantes emergentes et de plantes a feuilles flottantes, d'une part, et d'une communaute diversifiee et dense de plantes submergees, d'autre part Certains taxons de macrophytes se sont reveles intolerants aux conditions de turbidite et de richesse en elements nutritifs elevees (eg, Pontederia cordata, Najas flexilis), alors que d'autres tolerent une gamme etendue de conditions (eg, Typha spp, Potamogeton pectinatus) et se retrouvent dans les terres humides tant degradees qu'intactes
TL;DR: Two distinct fish assemblage types are identified: one characterized by small-bodied species, mainly cyprinids, and a second by large- bodied centrarchid species, e.g., smallmouth bass.
Abstract: Fish assemblages in small lakes (50 ha) in central Ontario were characterized to determine the impact of smallmouth bass (Micropterus dolomieu) predation and habitat complexity on the structure of ...
TL;DR: It is suggested that the difference in growth potential between the three habitats is partly related to the size at which fish first enter the diet.
Abstract: The growth rate of salmonid fishes is typically fastest in oceans, intermediate in lakes, and slowest in streams. We compiled literature data to test whether differences in the size of prey eaten by salmonids in the three habitats could account for these differences in growth rate (i.e., the prey-size hypothesis). In all three habitats, salmonid fishes exhibited ontogenetic niche shifts from feeding primarily on invertebrates when small to feeding on fishes when large. Contrary to the prey-size hypothesis, invertebrates eaten in streams were larger than those eaten in lakes or oceans, whereas fish eaten in oceans were smaller than those eaten in streams or lakes. Consistent with the prey-size hypothesis, salmonids began eating fish at a smaller size in oceans (8 cm) than in lakes (15 cm) or streams (27 cm). However, the size at which salmonids became predominantly piscivorous (31 cm) did not differ significantly between habitats. We suggest that the difference in growth potential between the three habitats is partly related to the size at which fish first enter the diet.
TL;DR: 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.
Abstract: 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 fis...
TL;DR: The results indicate that isotopic fractionation factors may not be independent of age as has largely been assumed, and significant age effects in the δ15N composition of adult walleye that were not attributable to observed changes in diet are documented.
Abstract: Stable nitrogen and carbon isotope ratios were measured for walleye (Stizostedion vitreum) collected across Lake Champlain, Vermont, to determine relationships between isotopic composition and diet...