bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue Accumulation and Enzymatic Effects of Hexavalent Chromium in Rainbow Trout (Salmo gairdneri)
Authors: Buhler Donald R. , Stokes Robert M. , Caldwell Richard S.
Published: April 2011

Two-year-old rainbow trout (Salmo gairdneri), reared for 2 yr in water containing about 0.00025 mg/ℓ hexavalent chromium (Cr+6) (Naches trout) or between 0.002 and 0.010 mg/ℓCr+6 (Hanford trout) accumulated appreciable chromium, yielding whole body residues of about 0.029 and 0.18 μg/g wet tissue, respectively. Highest concentrations were in the opercular bone, spleen, kidney, gastrointestinal tract, and gall bladder. Short-term exposure of Hanford trout to 2.5 mg/ℓCr+6 caused a rapid additional increase of tissue chromium, but at 22 days whole body levels were only 0.87 μg/g. Upon return of exposed fish to water containing 0.002–0.010 mg/ℓ chromium, the metal was rapidly depleted from most tissues except kidney, liver, gill, gall bladder, and bile. Chromium accumulated in tissues of trout exposed to 2.5 mg/ℓ Cr+6 was not distributed proportionally among the various subcellular fractions but concentrated in the cell cytosol, especially in the liver and gill.Mitochondrial cytochrome oxidase, NADH-cytochrome c reductase, and succinate cytochrome c reductase activities in liver, kidney, gill, and brain tissues of Naches trout, Hanford trout, and Hanford trout exposed to 2.5 mg/ℓ Cr+6 were not significantly different except for kidney NADH-cytochrome c reductase which was lower in Hanford and chromium treated fish. Microsomal nitroreductase, O-demethylase and NADPH-cytochrome c reductase and the soluble glucose-6-phosphate dehydrogenase activities in liver and kidney from Hanford trout were significantly lower than those of Naches trout. Exposure of Hanford trout to 2.5 mg/ℓ Cr+6, however, did not reduce the activities of these enzymes below control levels. In vitro studies showed that trout enzymes were fairly insensitive to Cr+6 inhibition. These results suggest that observed differences in enzyme activity between Naches and Hanford trout may be caused by factors other than chromium content of the water.
A Utility Function for Examining Policy Affecting Salmon on the Skeena River
Authors: Keeney Ralph L.
Published: April 2011

The interests of many groups, some with multiple objectives, are important to include in evaluating strategies affecting salmon in the Skeena River. A multiattribute utility model is proposed for addressing these issues. Two first-cut utility functions are assessed using the preferences of two individuals familiar with the problem. These utility functions provide a basis for constructive discussion to arrive at a reasonable utility function for examining alternative policies. Two unique features of this study are the explicit focus on value tradeoffs and equity considerations among interest groups, and a comparative examination of the two first-cut multiattribute utility models. This examination indicates the range of fundamental preferences which can be captured using multiattribute utility functions and illustrates the potential of the theory for conflict illumination and resolution.
DNA, RNA, Protein, and Free Amino Acids During Ontogenesis of Rainbow Trout (Salmo gairdneri)
Authors: Zeitoun Ibrahim H. , Ullrey Duane E. , Bergen Werner G. , Magee William T.
Published: April 2011

During the first 2 wk of incubation, the pattern of change in DNA concentration tended to precede similar changes in RNA concentration. Unfertilized eggs contained 23.2 and 77.2 μg of DNA and RNA, respectively. DNA concentration rose from 155.8 μg/fry (after 23 days of incubation) to 326.6 μg/larva (14 days after hatching), while RNA increased from 238.8 to 693.3 μg during the same period. Protein per ontogenetic unit was relatively constant during the prehatching stages but dropped markedly just prior to hatching. Of the protein in the unfertilized egg, approximately 20% was retained in the fry at hatching and approximately 50% was retained in the larva following yolk absorption. Total free amino acid concentrations declined just after fertilization, indicating the initiation of protein synthesis or a decline in yolk protein degradation. These concentrations increased to near initial values in the blastula and were nearly doubled in the yolk plus fry at hatching.
Inconnu, Stenodus leucichthys, Migration Studies in Alaska 1961–74
Authors: Alt Kenneth T.
Published: April 2011

During studies on inconnu, Stenodus leucichthys, in the Kobuk, Yukon, Koyukuk, Kuskokwim, Holitna, and Chatanika rivers, and the Selawik and Minto Flats areas, 3907 fish were marked. Nine hundred and ten (23.3%) had been recovered by December 31, 1974.Tag return data indicate that tagged inconnu comprise four major populations: Kobuk–Selawik, lower Yukon, Kuskokwim, and Minto Flats.Inconnu undertake rapid downstream postspawning migrations to wintering areas in lower reaches of large rivers (Yukon, Kuskokwim) or slightly brackish inlets (Hotham Inlet, Selawik Lake), then begin slow upstream migration before spring ice breakup, with nonspawning fish travelling to summer feeding areas and spawners migrating to spawning grounds during summer and fall. Minto Flats fish are nonanadromous.Three fish, tagged in the lower Yukon River and recaptured in the Koyukuk River, migrated upstream 1035–1156 km, averaging 13.8 km/day. The longest migration recorded was nearly 1,600 km.
Surface Area of the Euphausiid Thysanöessa raschii and Its Relation to Body Length, Weight, and Respiration
Authors: Harding Gareth C. H.
Published: April 2011

A method is described for estimating the surface area of marine crustaceans. The external surface area of the euphausiid Thysanöessa raschii (M. Sars) is proportional to length2.4, dry weight0.95, and wet weight0.84. Oxygen consumption is proportional to wet weight0.82, which indicates that respiration should be proportional to respiratory surface area. The implications of this finding regarding the relations of metabolic rate, size, and surface area are discussed in a broader framework by comparing them with similar studies on vertebrates and other invertebrates.
Preferred, Avoided, and Lethal Temperatures of Fish During Rising Temperature Conditions
Authors: Cherry Donald S. , Dickson Kenneth L. , Cairns Jr. John , Stauffer Jay R.
Published: April 2011

Selected temperatures increased for 15 fish species in a laboratory gradient when acclimated to 3 °C increments from 12 to 27 °C. Temperature preferences exceeded acclimation temperatures between 12 to 27 °C for all except the telescope shiner (Notropis telescopus), yellow perch (Perca flavescens), rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis). At 30, 33, or 36 °C acclimation, preferred temperatures were less than the acclimation temperature. The highest temperature preferences occurred at acclimations of 27, 30, or 33 °C. Bluegill (Lepomis macrochirus), spotted bass (Micropterus punctulatus), rockbass (Ambloplites rupestris), and the spotfin shiner (Notropis spilopterus) consistently selected the highest temperatures while the lowest temperatures were preferred by the salmonids. Final temperature preferences were usually greater than 29 °C for most centrarchids, above 24 °C for most cyprinids, and less than 19 °C for salmonids.Avoidance temperatures increased as acclimation temperature increased. Upper avoidances tested at high acclimation temperatures (30–36 °C) either equalled or exceeded the 7-day upper lethal temperature limit of the species by 1–2 °C, while avoidances were below this upper lethal limit when tested at the acclimation temperature closest to the species' final temperature preference.
Responses to Crude Oil Contamination by Cricotopus (Cricotopus) bicinctus and C. (C.) mackenziensis (Diptera: Chironomidae) in the Fort Simpson Area, Northwest Territories
Authors: Rosenberg David M. , Wiens Allen P. , Sæther Ole A.
Published: April 2011

Cricotopus (Cricotopus) bicinctus (Meigen) and C. (C.) mackenziensis Oliver, two common species of Chironomidae in the Fort Simpson area, N.W.T., were examined for changes resulting from experimental field exposure to Norman Wells crude oil. Larvae of both species were always present in higher numbers on oiled than unoiled artificial substrates but numbers of C. bicinctus increased more quickly than C. mackenziensis in response to the oil. Cricotopus mackenziensis larvae occurred in higher numbers than C. bicinctus larvae on unoiled artificial substrates. Cricotopus bicinctus tended to dominate C. mackenziensis on oiled artificial substrates. Size of larvae, as measured by head capsule width, was unaffected by increased food supply during periods of maximum algal biomass on oiled artificial substrates. Larvae on oiled artificial substrates apparently produced part of another generation when compared to larvae on unoiled artificial substrates.
Genetics of Larval Tolerance to Reduced Salinities in Two Populations of Oysters, Crassostrea virginica
Authors: Newkirk G. F. , Waugh D. L. , Haley L. E.
Published: April 2011

Oysters, Crassostrea virginica (Gemlin), were taken from a low- and an intermediate-salinity habitat. Males from each population were crossed with females from both populations and the offspring were raised at three salinities. Observations on survival during the larval period indicate that there are genetic differences between the two populations with regard to their tolerance to high and low salinity.
Relationship Between Two Stock–Recruitment Curves
Authors: Eberhardt L. L.
Published: April 2011

The Beverton and Holt and Ricker stock–recruitment curves can be used to generate population growth curves. The Beverton and Holt curve is then identical to a difference equation model for the logistic growth curve, and may be derived in terms of equations for linearly density-dependent population regulation. The same equations lead to the Ricker curve if the density-regulating effect is assumed to depend only on population size at the beginning of the interval between generations. At low rates of population growth, the Ricker curve approaches that of Beverton and Holt. The two curves appear to represent certain concepts known in population biology as "r and K selection."
A Biochemical Genetic Study of Zoogeography of Lake Whitefish (Coregonus clupeaformis) in Western Canada
Authors: Franzin W. G. , Clayton J. W.
Published: April 2011

Frequencies of alleles of the genes governing electrophoretic phenotypes of lake whitefish (Coregonus clupeaformis) muscle glycerol-3-phosphate dehydrogenase (G-3-PDH) and lactate dehydrogenase (LDH) enzymes, the genetics of which were determined previously, proved useful tools for characterizing populations. Malate dehydrogenase (MDH) and hemoglobin electrophoretic phenotypes, the genetics of which have not been determined, proved useful only for discerning differences among large groups of populations. Using all these characters we determined postglacial routes of gene flow among western Canadian lake whitefish populations and related the biochemical data to the glacial refugia in which lake whitefish are believed to have survived the Wisconsin glaciation. Apparently most lake whitefish populations west of the Ontario–Manitoba boundary and east of the Rocky Mountains were derived from a Mississippi refugium stock with some input from the Bering refugium. At an early stage in the mixing of the two stocks, headwaters of the Peace, Athabasca, and Mackenzie rivers and the Fraser River system were invaded. Subsequently, these areas were cut off from mainstem rivers of the plains, and a G-3-PDH allele not found in early emigrants from the Mississippi refugium appeared and spread throughout the major river systems of central Canada. No evidence was found that any Mississippi stock lake whitefish were able to invade the upper Liard River and Yukon River system including the area of the Bering refugium. Bering stock lake whitefish probably emigrated from that refugium by way of headwater transfer from the Yukon River to the Liard River and possibly, by way of the Porcupine and Peel rivers, from the Yukon River to the lower Mackenzie River. Routes of postglacial dispersal suggested by geological information, rather than selection, appear to provide adequate explanations for the distributions of the biochemical characters in present day lake whitefish populations. This explanation of the biochemical data is also in accord with the distribution of modal gillraker counts in lake whitefish populations and also with the distribution of other freshwater fishes in western Canada. Key words: fish, lake whitefish, Coregonus clupeaformis, salmonidae, zoogeography, dehydrogenase, postglacial, biochemical genetics
Precipitation Loading of Acid and Heavy Metals to a Small Acid Lake near Sudbury, Ontario
Authors: Beamish R. J. , Loon J. C. Van
Published: April 2011

The pH of Lumsden Lake was closely related to the measured amount of acid entering the lake from bulk precipitation. In 1972 it was estimated that an excess of 2135 kg of H2SO4 was added to the lake from the atmosphere. The predicted annual change in lake pH was from 5.2 to 4.8 and the actual measured change was from 5.2 to 4.7. In 1973 an estimated excess of 1271 kg of H2SO4 was added to the lake from the atmosphere. The predicted annual pH change was from 4.8 to 4.7 and there was no net change in the lake pH in 1973.Lumsden Lake also had high concentrations of sulfate, manganese, zinc, and nickel in comparison with remote or "unpolluted" lakes. High concentrations of manganese and possibly some zinc in the lake appeared to result from increased mobilization from the lake sediments or watershed or both as the pH decreased. Atmospheric fallout also contributed substantial quantities of nickel and copper to the watershed, some of which appeared to be retained in the lake water. The high concentrations of lead in the precipitation were not retained in the lake.
Recent Sedimentary History of a Eutrophic Reservoir: Long Lake, Washington
Authors: Thomas Sylvan R. , Soltero Raymond A.
Published: April 2011

Through abatement of present high nutrient loadings to the reservoir and preservation of sediment integrity, we predict that eutrophic Long Lake will experience a rapid recovery after the City of Spokane, Washington, establishes an advanced wastewater treatment plant with phosphorus removal. Two sediment cores were zoned into annual layers according to profile concentrations of organic matter, nitrogen, phosphorus, and diatom frustules. Sedimentation rate was 26 mm∙yr−1 between 1958 and 1973. Below the 25 mm-depth, phosphorus and diatom profiles were most obvious because clay particles, entering the reservoir during spring runoff, covered the biological material precipitated the previous year. This mechanism effectively prevents internal recycling of nutrients, particularly phosphorus, from the bottom sediments. Key words: reservoir, sediment cores, phosphorus, nitrogen, organic matter, diatom frustules, clays, internal nutrient recycling, recovery
Potential Contribution of Atmospheric Fallout to the Phosphorus Budget of Columbia Lake, Connecticut
Authors: Rich Peter H. , Pallotti Barbara L.
Published: April 2011

The Dillon–Rigler Model applied to a heavily "urbanized" lake in New England predicts that less than one half the total input of total phosphorus enters as stream runoff. Of the remaining predicted input, about two thirds may be entering as atmospheric fallout. The balance is suspected to be septic tank seepage and lawn fertilizer runoff. Lake level management dominates the annual pattern of discharge from the watershed and basin and severely restricts the structure of the upper littoral zone. This may have an adverse effect upon the accuracy of the Dillon–Rigler Model. Key words: phosphorus budget, Columbia Lake, artificial lake, atmospheric fallout
Copepod Instar Survival and Predation by Zooplankton
Authors: Confer J. L. , Cooley J. M.
Published: April 2011

The survivorship of each instar of three cohorts of Leptodiaptomus minutus from Bluff Lake, Nova Scotia, is presented. High naupliar mortality but low copepodite mortality occurred. The previously reported values for the predation rate and size selection of prey by omnivorous zooplankton are compared with the observed mortality rates for the different sizes of instars. We estimate that predation by the omnivorous zooplankton could account for most of the naupliar mortality. Our analysis supports Dodson's hypothesis that size-selective predation by zooplankton can be a significant factor determining the proportion of a cohort that reaches maturity.
Physiological and Behavioral Reactions of Fishes to Temperature Change
Authors: Crawshaw L. I.
Published: April 2011

Teleost fishes possess a central nervous system thermoregulatory mechanism remarkably similar to that of other vertebrates. Inputs from peripheral and anterior brainstem thermosensitive elements are integrated to effect appropriate thermoregulatory responses. The integrated output signal from the thermoregulatory center also appears to provide an input to the respiratory system. Short-term deviations from a given temperature alter respiratory requirements, produce acid–base imbalance, and cause disturbances in fluid–electrolyte regulation. Acclimation to a given temperature involves changes that counteract these disturbances. Key words: fish, temperature change, behavioral responses, physiological responses, temperature regulation
Heavy-Metal Contamination by Atmospheric Fallout of Several Flin Flon Area Lakes and the Relation to Fish Populations
Authors: Loon J. C. Van , Beamish R. J.
Published: April 2011

High concentrations of zinc and other heavy metals were found in lakes in the immediate vicinity of the Flin Flon smelters. In a study of 31 lakes, 7 had Zn levels above 100 μg/ℓ, 6 had levels between 50 and 100 μg/ℓ, and the remainder had concentrations < 50 μg/ℓ. The accuracy and precision of the heavy metal chemical analyses were evaluated using intercomparisons with other laboratories and a standard reference water. A linear relationship was demonstrated between log10 concentration of Zn, Cu, and SO42− and log10 distance from the smelter, suggesting atmospheric fallout as the main source of these substances in the lakes. Fishes were more tolerant of these high zinc concentrations than would be expected on the basis of the responses of fish and other aquatic organisms to similar concentrations of zinc in some laboratory toxicity tests. Key words: heavy metals, zinc, atmospheric fallout, fish toxicity, lake contamination, chemical analysis, Flin Flon, Canada
Phytoplankton Production and Distribution in Howe Sound, British Columbia: A Coastal Marine Embayment–Fjord Under Stress
Authors: Stockner John G. , Cliff David D. , Buchanan Douglas B.
Published: April 2011

Phytoplankton production and distribution were examined over a 2-yr period in relation to man-induced and natural factors that stress the system by mainly affecting the light regime in surface layer(s) of Howe Sound, British Columbia. Production rate and biomass values were greatest at the seaward boundary of the Sound where surface waters mix with the Strait of Georgia. Production decreases linearly in an up-inlet direction, reaching minimum values at the head of the Sound where the influence of the turbid Squamish River discharge is greatest. Annual production in the boundary waters of the Sound for 1973 and 1974 was 300 and 516 g C∙m−2, compared to an average of 118 and 163 for remaining stations. Strong light attenuation by the turbid Squamish River and flushing by the seaward moving surface layer were considered the most important factors controlling phytoplankton production and distribution in Howe Sound. Colored effluent from two pulp mills and turbid mine tailings and gravel washing water were minor perturbants to the system as a whole, but in affected bays and subregions of the Sound their effects on phytoplankton production were considerable. Annual production in Howe Sound was slightly higher than values for the Strait of Georgia and considerably greater than estimates from the North Pacific. Key words: phytoplankton, production, fjord–embayment, coastal marine, phytoplankton distribution, succession
A Gillnet Fishery Considered as an Experiment in Artificial Selection
Authors: Handford Paul , Bell Graham , Reimchen Tom
Published: April 2011

Temporal patterns of change in growth, condition, and mean age of samples of lake whitefish (Coregonus clupeaformis) taken from Lesser Slave Lake, Alberta, during 1941–75 are described. Growth rate and condition have declined, while mean age has increased. Gillnet fisheries are highly selective of large, heavy, fast-growing individuals, and we suggest that culling of this sort will provoke an evolutionary response in the stock, which may be reflected in patterns of change in growth and age. This hypothesis and others are discussed, and the general importance of artificial selection in lake fisheries is briefly considered. The possible implications for fishery management are outlined. Key words: artificial selection, evolution, growth rate, gillnet, Coregonus clupeaformis.
Cytotaxonomic Study of Gila Trout, Salmo gilae
Authors: Beamish R. J. , Miller R. R.
Published: April 2011

Gila trout, Salmo gilae, has a diploid chromosome complement of 2n = 56 consisting of 49 metacentric and submetacentric chromosomes and 7 acrocentric or telocentric chromosomes. Karyotypes of this and other species of western North American trouts of the genus Salmo suggest that chromosomal modifications are correlated to speciation in this genus. Key words: salmonidae, Salmo gilae, karyotype, chromosome, speciation
The dermatology of teleost fishes: a bibliography
Authors: Snieszko S. F.
Published: April 2011

not available
Morphology, Physiology, Behavior, and Ecology of Perca fluviatilis L. and P. flavescens Mitchill
Authors: Thorpe J. E.
Published: April 2011

A review of literature on Perca fluviatilis and P. flavescens indicated one difference (in the position of the predorsal bone) sufficient to maintain their separateness as species. Otherwise they are overwhelmingly equivalent biologically. Their distributions are limited by the same effects of temperature, current speed, salinity, and dissolved oxygen. They are similar in gonadal development and age at first maturity; in the effects of water temperature and latitude on spawning time, and of environmental fertility on fecundity; in spawning behavior, fecundity, and the course of larval development. Growth capacities are similar and their expression subject to population density and temperature in the same way. Both species are adapted to a diet of small live animals, but will take whatever is available; cannibalism is characteristic, and may begin at the same early feeding stage. The two species show similarities in diurnal periodicity of feeding and in total food consumption. They also have the same pattern of development of light responses, of schooling, of activity and of daily and seasonal migrations. Within the fish community they fulfill the same role as converters of invertebrate foods into a form suitable for consumption by terminal fish predators, especially Stizostedion spp., influencing the population dynamics of their predators in similar ways. Key words: Percidae, morphology, physiology, ecology, Perca, life history, growth, reproduction, yellow perch, Eurasian perch
Pikeperch (Stizostedion lucioperca) in its Natural Habitats in Poland
Authors: Nagięć Maria
Published: April 2011

The distribution and biology of pikeperch, Stizostedion lucioperca, in Poland are reviewed along with the characteristics of lakes where pikeperch are abundant. The characteristics of these lakes include low mean depth, lack of thermal stratification in summer, and intensive mixing of water. These characteristics are discussed in relation to primary productivity, zooplankton composition, abundance of benthos, and fish harvests in lakes and firths. Key words: Percidae, pikeperch lakes, harvest, habitat, Stizostedion lucioperca
Responses of Walleye (Stizostedion vitreum vitreum) and Yellow Perch (Perca flavescens) Populations to Removal of White Sucker (Catostomus commersoni) from a Minnesota Lake, 1966
Authors: Johnson Fritz H.
Published: April 2011

In a northeastern Minnesota lake subject only to sportfishing, removal of 85% of the estimated standing crop (34 kg/ha) of adult white suckers, Catostomus commersoni in 1966 was followed by marked changes in community structure and interrelations. During 7 yr alter the removal: catch indices for adult suckers remained far below those before the sucker removal but juvenile suckers increased about 17-fold; yellow perch, Perca flavescens, increased about 15-fold; walleye Stizostedion vitreum vitreum, standing crop increased about one-third; mayflies increased in diet of adult perch and smaller invertebrates decreased; micro-crustaceans increased in diet of young-of-the-year and juvenile perch; young-of-the-year perch increased in diet of adult walleye; walleye angling yield increased from an average of 3.0 kg/ha before the removal to an average of 4.9 kg/ha in 1970–73; the rate of exploitation of adult walleye did not change with increase in angling effort; and the increased walleye harvest consisted mostly of fish recruited to the catch during the fishing season. The average annual harvest of walleye in 1970–73 exceeded estimated potential production for all fish by 81.5% and probably cannot be sustained. Removal of white suckers from lakes with limited fish species diversity appears to benefit percid populations. Key words: Percidae, species interactions, (Stizostedion vitreum vitreum), Perca flavescens, Catostomus commersoni, harvests, community response, community ecology, food, competition
Population Dynamics of Percids in Lake IJssel and some Smaller Lakes in The Netherlands
Authors: Willemsen J.
Published: April 2011

Pikeperch (Stizostedion lucioperca) and Eurasian perch (Perca fluviatilis) in Lake IJssel both prey mainly upon the very abundant smelt (Osmerus eperlanus). But competition for food is of little or no importance and growth is not density-dependent. Growth rates for perch and ruffe (Gymnocephalus cernua) in some lakes are exceptionally rapid, mean lengths after 3 yr being 24 and 18 cm, respectively. Very intensive fishing for pikeperch (total annual mortality 81%) in the season before first spawning removes particularly the fast-growing fish from the population, thus restricting reproduction mainly to the slow-growing pikeperch. Year-class strength of pikeperch is strongly favored by a high summer temperature during the first year of life. Strong year-classes of pikeperch in Lake IJssel are characterized by a mean length of the young-of-the-year of 14.5 cm or more. Migration of pikeperch and perch in Lake IJssel is restricted. When transported to other areas of the lake, both species showed a distinct homing behavior. Key words: Percidae, population dynamics, Stizostedion, Perca, Gymnocephalus
Evidence of Inter- and IntraSpecific Competition as Factors Regulating Walleye (Stizostedion vitreum vitreum) Biomass in Oneida Lake, New York
Authors: Forney John L.
Published: April 2011

The sequence of events that led to a decline in numbers of American eel (Anguilla rostrata) and esocids and an increase in numbers of walleye (Stizostedion vitreum vitreum) in Oneida Lake from 1900–74 are reviewed. Demise of eel and esocids was followed by a rise in numbers of walleye, but little change in mean size of individual walleye. Reduced interspecific competition apparently enhanced walleye recruitment, but the anticipated increase in growth of walleye was probably inhibited by intensified intraspecific competition. This interpretation was supported by evidence that recruitment and growth of walleye in 1957–74 were regulated by prey abundance. Transition from a diverse predator population to one dominated by walleye was orderly and yellow perch (Perca flavescens) remained the most abundant prey. Key words: Percidae, competition, walleye biomass, Stizostedion, population dynamics, community ecology
Walleye (Stizostedion vitreum vitreum) Fluctuations in the Great Lakes and Possible Causes, 1800–1975
Authors: Schneider J. C. , Leach J. H.
Published: April 2011

Changes in walleye (Stizostedion vitreum vitreum) stocks in the Great Lakes from 1800 to 1975 were linked to proliferation of foreign species of fish and culturally induced sources of stress — exploitation, nutrient loading, alteration of spawning habitat, and toxic materials. During the 1800s, three small spawning stocks (and probably many others) were damaged or destroyed because of either overfishing or elimination of spawning habitat through logging, pollution, or damming.During 1900–40, stocks in the Michigan waters of Lake Superior, southern Green Bay, the Thunder Bay River of Lake Huron, the North Channel of Lake Huron, and the New York waters of Lake Ontario declined gradually. Pollution, in general, and degradation of spawning habitat, in particular, probably caused three of the declines and overexploitation was suspected in two instances. In addition, the decline of three of these stocks occurred when rainbow smelt (Osmerus mordax) were increasing.During 1940–75, stocks in seven areas declined abruptly: Saginaw Bay (1944), northern Green Bay (1953), Muskegon River (mid-1950s), western Lake Erie (1955), Nipigon Bay (late 1950s), Bay of Quinte (1960), and Black Bay (mid-1960s). The decline of each stock was associated with a series of weak year-classes. The stocks were exposed to various sources of stress, including overexploitation, pollution, and interaction with foreign species, which, if not important in the decline, may be suppressing recovery. Only the western Lake Erie stock recovered, in part due to a reduction in exploitation and, possibly, because of the relatively low density of smelt and alewives (Alosa pseudoharengus) in the nursery areas.Relatively stable stocks persisted in five areas: Wisconsin waters of Lake Superior, Lake St. Clair — southern Lake Huron, eastern Lake Erie, northern Lake Huron, and parts of Georgian Bay. Pollution problems were relatively minor in these areas and exploitation was light during recent decades. Apparently these stocks were more capable of withstanding the additional stresses exerted by alien species. Key words: population fluctuations, Percidae, Stizostedion, Great Lakes walleye, history of fisheries, summary of stresses, harvests, management implications
Species Interactions in Percid Communities
Authors: MacLean James , Magnuson John J.
Published: April 2011

Evidence for species interactions in communities with Perca and Stizostedion is evaluated. Substantial evidence exists for the importance of predation by and on percids to community structure and function. Some evidence also clearly demonstrates that competition is an important interaction both within Perca populations and between Perca and other species. The necessity of using manipulative experiments to test for community level effects of competition and predation is emphasized. Such manipulative experiments, however, should be restricted in number and conducted with great care, because the community changes they induce are often irreversible and detrimental.Species interactions related to feeding have apparently resulted in the partitioning of habitat and food resources among fishes in percid communities. Partitioning of space is considered in terms of distribution of Perca and Stizostedion in respect to temperature in stratified and unstratified aquatic systems. In stratified lakes, percids are expected to be spatially segregated from fishes with other thermal requirements, such as the warmwater centrarchids and the cold-water salmonids. Seasons and depths of potentially intense interactions are diagrammed. In unstratified lakes, latitude and lake size set the stage for the thermal habitat that favors the physiology of percids in some systems. Resource partitioning, in respect to food size and time of day for foraging, is also diagrammed and appears to be important. It is argued that species interactions between other fishes and Perca and Stizostedion are greatly reduced by present patterns of resource utilization. Key words: competition, predation, resource partitioning, percid communities
Structure and Transformation of Fish Production Systems
Authors: Kerr S. R.
Published: April 2011

A tentative synthesis is provided of some considerations that emerged from the PERCIS proceedings. The percid composition of commercial fisheries tends to be relatively conservative except where abrupt community transformations, characterizable as fold catastrophes, mark the effects of critical conjunctions of fishing intensity and lake productivity acting jointly as control variables. These behaviors of fish production systems are consistent in general with current observations and theory based upon size-dependent processes in marine pelagic fisheries. Key words: theory, percidae, community ecology, fishing intensity, production systems
Seasonal and Vertical Distribution and Growth of Juvenile and Adult Capelin (Mallotus villosus) in the St. Lawrence Estuary and Western Gulf of St. Lawrence
Authors: Bailey R. F. J. , Able K. W. , Leggett W. C.
Published: April 2011

The distribution of juvenile and adult capelin (Mallotus villosus) in the estuary and western Gulf of St. Lawrence was similar in 1974 and 1975. Juvenile (age 1 and 2) capelin were largely restricted to the western Gulf, which appears to serve as a nursery area for larval and juvenile capelin, throughout the summer and fall. During the summer and early fall capelin occurred in small schools which were widely distributed over most of the western Gulf. Concentration of juvenile and adult capelin into dense schools and their movement into the lower estuary in November were interpreted as the initiation of a contranatant migration to the spawning areas in the estuary. Spawning occurred first in the upper estuary (April–May) and was progressively later in the lower estuary and western Gulf. Postspawning mortality was high and resulted in a rapid decline in the abundance of adult capelin in the estuary and western Gulf following spawning. A concentration of juvenile capelin in and near the mouth of the Saguenay River throughout the year was apparently supported during the late summer by zooplankton production in the river. These fish, in turn, contribute heavily to the food resource of a large population of beluga whales that summer in the area. Capelin from the study area reach a greater mean size at the end of the 1st yr than do those from Newfoundland, Labrador, and Greenland. Subsequent growth was similar to that of stocks from southern Newfoundland but was faster than in stocks from northern Newfoundland and Labrador. Capelin populations in the estuary and western Gulf matured earlier and had younger mean ages than those from other areas in the Canadian Atlantic. Key words: capelin, Mallotus villosus, Gulf of St. Lawrence, seasonal distribution, vertical distribution, growth, spawning
Blood Changes in Atlantic Cod (Gadus morhua) Infected with Trypanosoma murmanensis
Authors: Khan R. A.
Published: April 2011

Blood samples for hematological and parasitological studies were obtained from 30 Atlantic cod (Gadus morhua) at intervals after infection with Trypanosoma murmanensis via leeches. Hematological procedures included estimation of hematocrit, hemoglobin, erythrocyte sedimentation rate (ESR), and differential white cell count. Tissues were also examined for histological changes. Results from the cod could be divided into two groups. In the first group of 10 cod (16–24 cm), coincident with the rise in parasitemia, hematocrit and hemoglobin levels decreased and the ESR increased following infection. Values did not return to normal levels by 92 days postinfection despite decreasing and somewhat irregular fluctuating parasitemias after 29 days. There was no apparent change in the differential white cell count. Increased hemopoiesis occurred in the kidney and various developmental stages of erythrocytic precursors were noted in peripheral blood. The fish appeared somewhat lethargic. In the second group of 20 cod (26–49 cm), hematological changes observed were slight and there was no evidence of decreased mobility. These results suggest that the blood changes observed in the group of small cod are sufficient to affect them similarly under natural conditions so that they could become more prone to predators, pollutants, or diseases. Key words: blood changes, Atlantic cod, trypanosomes
Evaluation of the Ascorbic Acid Status of Rainbow Trout (Salmo gairdneri)
Authors: Hilton J. W. , Cho C. Y. , Slinger S. J.
Published: April 2011

Due to the instability of supplemental ascorbic acid in practical trout diets and the increased metabolism of this vitamin in trout ingesting enviromental toxicants, a method of assessing the adequacy of dietary ascorbic acid and the ascorbic acid status of the trout is required. Two groups of trout grown on ascorbic acid deficient diets produced deficiency symptoms within 16–20 wk. Liver ascorbic acid concentrations in the two groups declined to levels below 20 μg/g when deficiency symptoms appeared. Groups of trout grown on diets containing supplemental ascorbic acid to provide near or in excess of the National Research Council–National Academy of Science requirement for this vitamin after processing showed substantially higher liver ascorbic acid concentrations than the deficient fish. This indicates that the liver ascorbic acid concentration can be used as an index of the ascorbic acid status of the trout and that levels 20 μg/g or lower are marginal and immediate supplementation is required. Key words: ascorbic acid, rainbow trout, nutritional requirements
Phytoplankton Summer Standing Crop and Annual Productivity as Functions of Phosphorus Loading and Various Physical Factors
Authors: Oglesby Ray T.
Published: April 2011

Relations of phytoplankton summer standing crop and annual productivity to morphometric properties and edaphic factors, especially phosphorus loading, have been examined for a large, diverse, globally distributed group of lakes. Standing crop was highly correlated with dissolved phosphorus loading when mixing of the water column was taken into account. A regression applicable to lakes of all depths is given as a log-log function with predictive confidence intervals for summer mean values. Boundary conditions for the exclusion of certain lakes have been roughly determined. For lakes of mean depth > 25 m areal loading accounted for 97% of the variance in summer phytoplankton standing crop. Phosphorus inputs to shallower systems were adjusted to give a simple approximation of the influence of mixing processes and the ratio of bottom area to overlying water volume. Annual primary productivity seems to be a more complex and variable function of phosphorus loading than is summer standing crop. The former correlated fairly well with the morphoedaphic index. Productivity and standing crop showed well-defined trends in relation to other variables, but point scatter was so great that more exact definition of these functions was not justified. Key words: phytoplankton, phosphorus, eutrophication, lakes, morphoedaphic index
Relative Toxicity of Free Cyanide and Dissolved Sulfide Forms to the Fathead Minnow (Pimephales promelas)
Authors: Broderius Steven J. , Smith Jr. Lloyd L. , Lind David T.
Published: April 2011

The relationship between pH and acute toxicity of free cyanide (i.e. HCN + CN−) and dissolved sulfide (i.e. H2S + HS− + S2−) to the fathead minnow (Pimephales promelas) at 20 °C was determined for pH values ranging from about 6.8 to 9.3 and 6.5 to 8.7, respectively. The 96-h median lethal concentrations (LC50s) of free cyanide and molecular HCN were little different and fairly constant within the pH range 6.8–8.3. Beyond this, to pH 9.3 the values diverged markedly, with the free cyanide LC50s increasing and the HCN LC50s decreasing. Except for some increase with rise of pH from about 6.5 to 7.1, the 96-h LC50 concentrations of molecular H2S decreased linearly and by approximately fourfold as the pH increased from 7.1 to 8.7. The 96-h LC50 concentrations of dissolved sulfide in corresponding equally toxic solutions increased logarithmically as pH increased from 6.5 to 8.7. Acute toxicities to fathead minnows of free cyanide and dissolved sulfide do not depend entirely on the concentration of ambient molecular HCN or H2S. Change in toxicity of the molecular forms with pH was evaluated by two gill-permeability theories. The likelihood of certain chemical changes occurring at the gill surface or the possible penetration of the gill by both molecular and anionic forms present in the test solutions at different pH's was evaluated. Increased apparent toxicity of molecular HCN or H2S with elevated test pH is believed to result from the CN− and HS− anions penetrating the gill epithelium, though less readily than do the molecular forms, and enhancing the toxicities of these solutions as the pH increases. Key words: toxicology, hydrogen ion concentration, bioassays, lethal limits, gill-permeability theories
Artificial Hybrids Between Amur Pike, Esox reicherti, and North American Esocids
Authors: Crossman E. J. , Meade James W.
Published: April 2011

Artificial hybrids between Esox reicherti, the only species in the family Esocidae that does not occur naturally in North America, and North American esocids were developed. Five of a possible 10 crosses are described in detail. Three crosses failed (those involving the males of E. niger and E. americanus) for reasons other than methodology, the cross involving females of E. americanus americanus was not made, and a fifth cross involving the male of E. masquinongy was successful but no data are included. Interspecies fertility was suprisingly high, and an inverse relationship existed between survival of crosses and the difference in potential maximum size of parent species. At least one cross was fertile, and an F2 generation and backcrosses were developed. Key words: artificial hybrids. Esocidae, Esox reicherti, Esox masquinongy, Esox lucius, Esox niger, Esox americanus
Habrobaenus hudsoni n.gen., n.sp. and the Immatures of Baeoctenus bicolor Sæther (Diptera: Chironomidae)
Authors: Sæther Ole A.
Published: April 2011

Habrobaenus hudsoni n.gen., n.sp., described from males and a pupa, is related to Hydrobaenus Fries sensu Sæther. Habrobaenus appears to form the sister group of either Trissocladius, or Trissocladius and Zalutschia combined. The peculiar morphology of the immatures o Baeoctenus bicolor Sæther, described here for the first time, probably reflects their parasitic habit on the gills of Anodonta. Key words: Habrobaenus hudsoni, Baeoctenus bicolor, Diptera, Chironomidae, systematics, larvae, pupae, imagines
Biology of the Morid Fish Antimora rostrata in the Western North Atlantic
Authors: Wenner Charles A. , Musick John A.
Published: April 2011

From otter trawl catches in the Middle Atlantic Bight, blue hake, Antimora rostrata, were found at depths of 790 to at least 2930 m in the Norfolk Canyon area; maximum abundance was between 1300 and 2500 m. Available data indicate that the blue hake is more abundant in the western than the eastern North Atlantic. Males were smaller in average size than females and a skewed sex–depth relationship was found with a larger percentage of the catch in shallower depths being male. In Canadian Atlantic waters A. rostrata live in water at least 500 m shallower. The Middle Atlantic continental slope may serve as a feeding habitat for this species; the reproductive and larval portions of its life history are probably completed in the northern part of its range. Key words: Antimora rostrata, bathymétrie distribution, reproduction
Storage Life of Refrozen Silver Hake (Merluccius bilinearis) Processed as Fillets am Minced Flesh from Thawed, Stored, Round-Frozen Fish
Authors: Hiltz Doris Fraser , North D. H. , Lall Barbara Smith , Keith R. A.
Published: April 2011

Refrozen silver hake (Merluccius bilinearis), processed as fillets and minced flesh after thawing of stored round fish that had been frozen within 14 h of capture, underwent rapid deterioration during storage at −18 °C compared with once-frozen control materials from the same lot of fish. The estimated maximum storage life of silver hake refrozen as fillets after 3 and 6 mo storage of the round fish at −25 °C was reduced to about 4.5 and 1 mo, respectively, from 10 mo for once-frozen control fillets. Quality of the refrozen materials immediately after thawing and refreezing was similar to that of the round-frozen fish, except after 6 mo, where some initial deterioration occurred, particularly in minced flesh. Minced flesh was more unstable in frozen storage than fillets. In all once- and twice-frozen materials, formation of dimethylamine occurred concomitantly with decrease in protein extractability. Round-frozen fish underwent no loss in protein extractability during 6 mo storage at −25 °C, but some lipid hydrolysis occurred. These results suggest that the freeze–thaw–refreeze process as applied to silver hake will yield a final product of acceptable quality provided that storage of the round fish does not exceed 3–4 mo and that the refrozen materials are marketed within a month after processing. Key words: silver hake, Merluccius bilinearis, refrozen storage, dimethylamine, minced flesh
Proceedings of the First International Conference on Aquaculture Nutrition.
Authors: Yurkowski M.
Published: April 2011

not available
Fishes of the World.
Authors: Winterbottom Richard
Published: April 2011

not available
Feeding Interrelations Between Age-Groups of Pumpkinseed (Lepomis gibbosus) and Comparisons with Bluegill (L. macrochirus)
Authors: Keast Allen
Published: April 2011

Analysis of the stomachs of 2435 pumpkinseeds (Lepomis gibbosus) showed that the diet was made up largely of chironomid larvae, molluscs, isopods, with lesser quantities of amphipods, Trichoptera larvae, and Ephemeroptera nymphs. Cladocera were only important to the very young fish. Age-class separation, in terms of taxonomic and prey-size categories, was minor, although the diet changed somewhat with age. Quantification of the diet overlaps between year-classes (by Levins index) revealed overlap levels that were moderate to high, varying seasonally between 0.5 and 1.1. They were greatest in July when the diversity of available prey organisms fell and October when several size-classes simultaneously consumed isopods, then at a peak in biomass. The feeding and spatial ecology of the pumpkinseed was compared with that of a closely related congener, the bluegill (L. macrochirus). The two species and their equivalent year-classes separated out partially on diet (the bluegill consuming a greater proportion of Cladocera and Tnchoptera larvae; the pumpkinseed, molluscs and isopods), and partly on habitat and the height at which they foraged in the water column. Ecological overlap values between equivalent year-classes of the two species were moderate, 0.52–0.57 (Levins scale), on the basis of diet alone as well as when the habitat component was incorporated. It is suggested, however, that other differences serve to reduce these levels. Key words: feeding, year-class diets, sunfish, intraspecific competition, interspecific competition, prey invertebrates, Centrarchidae
Estimating the Diet of a Sluggish Predator from Field Observations
Authors: Peterson Charles H. , Bradley Brian P.
Published: April 2011

Predation often occurs slowly, so that observing a sufficiently large sample of entire predation episodes represents an inconvenient means of quantitatively estimating the predator's diet. Fortunately, related data are usually available specifying the proportions of predators found feeding on each prey type. We demonstrate how dividing the observed proportion of all predators found feeding on a given prey type by the average contact time required to consume a single item of that prey type produces an estimate of the relative frequency of the prey in the predator's diet. The analogous procedure, when based upon residence times in the gut, serves to derive a quantitative estimate of diet from numerical data on gut contents. Key words: dietary analysis, feeding frequencies, stomach contents, predator–prey contact times