bluuebunny/crossref_metadata_2025 huggingface dataset:
Population Biology of Lake Trout (Salvelinus namaycush) of Lake Superior before 1950
Authors: Sakagawa Gary T. , Pycha Richard L.
Published: April 2011

Scale samples collected in 1948 were used to estimate the instantaneous total mortality rate (0.70) and growth for lake trout (Salvelinus namaycush) in Lake Superior before the population had been significantly reduced by the sea lamprey (Petromyzon marinus). Indirect evidence indicates that the instantaneous natural mortality rate was probably 0.10–0.25. The Ricker model was used to calculate yield per recruitment, which varied with natural mortality and growth. Natural mortality was more critical than growth; yield per recruitment increased 183.3% with a 60% decrease in instantaneous natural mortality (from 0.25 to 0.10). For the prelamprey lake trout population the yield per recruitment was about 12–34 lb; the recruitment of about 3.6–10.1 million lake trout of age 1.5 resulted in an annual commercial production of 4 million lb.
A Device for Rapid Removal of Embryos from Fish Eggs
Authors: MacKelvie R. M.
Published: April 2011

An inexpensive and easily constructed device is described whereby embryos were removed from fish eggs for the study of viral multiplication.
Results of the Initial Survey of the Experimental Lakes Area, Northwestern Ontario
Authors: Cleugh T. R. , Hauser B. W.
Published: April 2011

A reference list is given to locations, areas, maximum depths, transparencies, total dissolved solids, and conductivities of lakes shown on the insert map of the Experimental Lakes Area in the back of this issue.
Electronic Processing of Acoustical Data for Fishery Research
Authors: Lenarz William H. , Green James H.
Published: April 2011

A system for processing acoustical data is described. Acoustical data are recorded on magnetic tape in analog form in the field. The data are converted to digital form and analyzed with the aid of a digital computer. The system provides investigators with considerably more information than is available from paper records now in common use.
Intraspecific Variations and Postglacial Distribution of Lake Char (Salvelinus namaycush)
Authors: Khan N. Y. , Qadri S. U.
Published: April 2011

A morphometric and meristic study of 325 lake char (Salvelinus namaycush) from over its range of distribution showed different gene pools. The similarities and differences observed among lake char of various primary ocean drainages and among various populations of lake char within these drainages suggested that the species survived the last glaciation in unglaciated Alaska and Yukon, possibly other unglaciated northern areas, and at least three refugia in the south, the Atlantic, Upper Mississippi, and Upper Missouri.
Some Enzymatic Properties of Plasma Esterases from Channel Catfish (Ictalurus punctatus)
Authors: Hogan James W.
Published: April 2011

Rates of ester hydrolysis by plasma enzymes from five fish species ranged from 12 8 to 46.6 μmoles acetylcholine hydrolyzed/ml plasma per hr. Enzymes in channel catfish (Ictalurus punctatus) plasma hydrolyzed the substrates acetylcholine, phenyl acetate, and glyceryl triacetate at rates of 28.1, 96.7, and 6.8 μmoles substrate hydrolyzed/ml plasma per hr, respectively. Esterolytic activity was attributed, in part, to an acetylcholinesterase-like enzyme. In vitro organophosphate inhibition of enzymes in channel catfish plasma was similar to that previously reported for catfish brain acetylcholinesterase (EC 3.1.1.7, acetylcholine acetyl-hydrolase).
Lipid and Caloric Contents of the Relict Amphipod Pontoporeia affinis in Cayuga Lake, New York
Authors: Green Roger H.
Published: April 2011

The relict amphipod Pontoporeia affinis at 100 m depth in Cayuga Lake, New York, had a lipid content of 33.1% of dry weight, which is unusually high for a benthic crustacean. This high lipid content resulted in the unusually high caloric content of 5240 cal/g dry weight, and a mean annual standing crop of 370 cal/m2. Annual production was estimated to be 1565 cal/m2 per year. In confirmation of the high caloric value, P. affinis from an oligotrophic lake in northwestern Ontario had a caloric content of 4741 cal/g dry weight.
Preliminary Survey of Heavy Metal Contamination of Canadian Freshwater Fish
Authors: Uthe J. F. , Bligh E. G.
Published: April 2011

The concentration of 13 toxic elements in dressed fish from a nonindustrialized and heavily industrialized freshwater area have been measured. With the exception of mercury, in no instance did levels exceed limits set by regulatory agents for lead, arsenic, copper, and zinc. Indeed in the majority of instances the levels from the industrialized area did not differ significantly from those of the nonindustrialized area.
Egtved Virus: Demonstration of Neutralizing Antibodies in Serum from Artificially Infected Rainbow Trout (Salmo gairdneri)
Authors: Jørgensen P. E. Vestergård
Published: April 2011

Rainbow trout (Salmo gairdneri) kept in a tank with tap water supply for 18 months at a water temperature of 8–13 C were given monthly intraperitoneal injections of nonpathogenic cell-culture-derived Egtved virus. After 1 year, a low titer of neutralizing antibodies to Egtved virus could be demonstrated in the trout serum. Such antibodies could not be demonstrated by the method applied in sera from rainbow trout exposed to natural infection with Egtved virus at two Danish trout farms.
Habitat Segregation in Sanguinicolid Blood Flukes (Digenea) of Scorpaenid Rockfishes (Perciformes) on the Pacific Coast of North America
Authors: Holmes John C.
Published: April 2011

Aporocotyle macfarlani Holmes, 1971, was found in five species of Sebastes taken from the inland waters around the San Juan Islands, Washington, or the inshore waters around Vancouver Island, B.C. Psettarium sebastodorum Holmes, 1971, was found in 14 species of Sebastes from the same locations or from deeper offshore waters west of Vancouver Island. The two flukes have different dominant hosts. Their numbers show different relations with depth. Aporocotyle macfarlani appears to be associated with fish that frequent reefs.Aporocotyle macfarlani occupies the lumen of the afferent branchial arteries, the ventral aorta, and rarely parts of the heart; P. sebastodorum is threaded into the intertrabecular spaces of the ventricle and atrium. The overlap in the distributions of the two species is reduced in concurrent infections.
Periodic and Resident Components in Communities of Atlantic Fishes
Authors: Tyler A. V.
Published: April 2011

From trawling at least monthly on a station in Passamaquoddy Bay, N.B., four groups of species were distinguished. One group of species was present on station during winter only, another group in summer only, and a third group was present throughout the year. A fourth group of species was present only occasionally. This type of temporal component structure was found in previously published data for stations with similar habitat but at different latitudes and different temperature regimes. With increased annual temperature fluctuation by locality, there were proportionately more species in the periodic components and fewer in the regular component. Comparable tropical communities had very small periodic components.
Determination of Nitrilotriacetic Acid in Inland Waters by Gas Chromatography of the Trimethyl Ester
Authors: Murray D. , Povoledo D.
Published: April 2011

A method for the analysis of low concentrations of nitrilotriacetic acid (NTA) in natural waters was developed. The NTA was converted to the trimethyl ester and determined quantitatively by gas chromatography using methyl heptadecanoate as an internal standard. The lower limit of detection was 25 μg/liter of NTA. The identity of the ester was confirmed using a mass spectrometer–gas chromatograph combination.
Relation Between Tube-Building and Feeding in Neoamphitrite robusta (Polychaeta: Terebellidae)
Authors: Brown P. L. , Ellis D. V.
Published: April 2011

Tube-building and feeding behaviour of Neoamphitrite robusta shared similar initial activities of tentacle extension, particle gathering, and passage of particles to the oral region. Particles were sorted by the inner lips, but the extent of sorting depended upon whether the animal was tube-building or feeding. Particles to be incorporated into the tube were passed over the outer lips and moulded into the tube in a stereotyped manner. Tube-rebuilding in test specimens (tubes removed) proceeded significantly faster than tube-building in control specimens (within tubes), although feeding was significantly less in the test specimens. Nonfeeding specimens were able to construct tubes. The two behaviours were able to proceed independently, although feeding supplemented tube-building with the passage of rejected particles to the tube.
A New Species, and Additions to the Descriptions of Six Other Species of Syllides Örsted (Syllidae: Polychaeta)
Authors: Banse Karl
Published: April 2011

Additions are made to the description of Syllides articulosa, S. convoluta, S. japonica, and S. longocirrata. Syllides fulva and S. verrilli are recognized as valid species, and Syllides benedicti is newly described. Several new records are given. The overlapping of characters of Syllides and Pionosyllis is pointed out. Possibly, the insertion of the blades of the compound setae may prove to be a reliable character in differentiating the two genera.
Size Selective Predation Among Juvenile Salmonid Fishes in a British Columbia Inlet
Authors: Parker Robert R.
Published: April 2011

Field observations suggest early sea mortality of pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon fry is largely due to predation by juvenile coho (O. kisutch) salmon. A series of experiments demonstrates a strong bias toward the smaller individuals of the prey population. This results in an apparent growth rate 0.3–0.5% per day due to the biased mortality alone. With a high innate growth rate [Formula: see text], the prey are shown to "outgrow" the predator [Formula: see text], and hence become unavailable. Chums are shown to have an advantage over pinks through slightly earlier entry into the estuary and a larger initial size. The mechanism of selection used by the predator is not known from this study.
Relation Between Production and Biomass
Authors: Allen K. Radway
Published: April 2011

A series of mathematical models of cohorts in animal populations representing various combinations of several different simple growth and mortality functions is examined to investigate the ratio between mean biomass and production over unit time, and to compare this ratio with the mean age and mean life span of the animals in the cohort.For any cohort, the ratio of production per unit time to mean biomass is equal to the ratio of total production by the cohort to its total biomass integral by time. For populations consisting of a number of simultaneous, successive, or overlapping cohorts, the ratio of production per unit time to mean biomass is equal to the mean of the ratios for the individual cohorts weighted by the mean biomasses of the cohorts.If the cohorts are identical, the population ratio is the same as the cohort ratio and problems arising from the presence of more than one cohort may be ignored. Formulations for the total production per cohort, biomass integral, and, where they can be simplified, their ratios, are given.Comparison with mean age and mean life span shows that for constant exponential mortality, mean age and mean life span are both equal to the reciprocal of the production–biomass ratio. For other mortality functions, if growth in weight is linear, the production–biomass ratio equals the reciprocal of the mean age. For other models there is no simple relation. In general, mean age appears a better approximation than mean life span to the reciprocal of the production–biomass ratio.These methods are applied, as an example, to Antarctic krill, using a model having linear growth in length and four periods with different exponential mortality rates. For this model, annual production is 1.8 times the mean biomass so that assumption of equality leads to an underestimate of production. Mean age and mean life span are 0.21 and 0.037 years respectively. Thus, use of either of these as an approximation, and particularly mean life span, leads to severe overestimation of annual production.
Benthic Community Metabolism in Bay of Quinte and Lake Ontario
Authors: Johnson M. G. , Brinkhurst R. O.
Published: April 2011

Rates of sedimentation of organic matter to the bottom sediments at four stations (in order from the inner Bay of Quinte to open Lake Ontario) averaged 1.91, 0.42, 0.36, and 0.21 g m−2 day−1. Respective respiration rates of sediment cores averaged 0.35, 0.25, 0.22, and 0.15 g O2 m−2 day−1. Approximately 90% of imported energy (IM) was used by the benthic communities at the three lakeward stations and 23% at the inner bay station. Low utilization in the inner bay was substantiated by the high organic matter (28%) in sediments there, in contrast with Lake Ontario sediments (3–4%). Low utilization was attributed to the relatively greater proportion of allochthonous import. Only 2% of imported energy was assimilated by macroinvertebrates in the inner bay, in contrast with about 30% at the lakeward stations.A concise model of macroinvertebrate production, P = c(a∙b IM) (where c is the proportion of growth to respired and exported energy and is derived from the average growth efficiency of macroinvertebrates, a is proportion of imported energy used by the total benthic community, and b is proportion of the latter used by macroinvertebrates), was used to deduce the relation between production and import. All of the parameters a, b, and c presumably decrease with increasing import, although c may be low initially at low import and sparse food supply.
Effects of Handling and Salinity on Oxygen Requirements of the Striped Bass, Morone saxatilis
Authors: Chittenden Jr. Mark E.
Published: April 2011

Oxygen requirements of striped bass, Morone saxatilis, were studied at 0 and 10‰ salinity using combinations of handling and constantly decreasing oxygen concentrations. Effects of handling and salinity on oxygen requirements were negligible or absent. Successive and merging patterns of behavior at low oxygen concentrations were: restlessness, spasmodic swimming, surfacing, inactivity, equilibrium loss, and death. Mean oxygen levels with 99% confidence limits at restlessness, inactivity, equilibrium loss, and death were 1.81 ±.10, 1.28 ±.10, 0.95 ±.06, and 0.72 ±.04 mg/liter. Virtually no fish exhibited these behavior patterns until oxygen declined to 3.12, 2.19, 1.44, and 1.04 mg/liter, respectively; nearly all fish did at 0.91, 0.66, 0.62, and 0.50 mg/liter, respectively. Size of fish did not affect oxygen levels at death and equilibrium loss.Ventilation rate was maximum at 2.0–3.0 mg/liter and declined at lower concentrations. Amplitude was maximum at the beginning of inactivity then declined. Because short-term respiratory failure occurred at equilibrium loss, this behavior probably represents oxygen levels that would cause an abrupt fish-kill. Long-term respiratory failure at inactivity indicated that death would follow a period of resistance.There is no sharp distinction between suitable and unsuitable oxygen concentrations, because duration of exposure determines the intensity of the result even at lethal levels. Onset of restlessness (about 3 mg/liter at 16–19 C) probably represents the minimum permissible oxygen level for normal existence. Even this may be insufficient to maintain optimum populations of striped bass.
Redescription and Distribution of the Rare Deep-Sea Eel Xenomystax atrarius in the Eastern Pacific Ocean
Authors: Peden Alex E.
Published: April 2011

Xenomystax atrarius Gilbert has been considered a possible representative of as many as three eel families (Congridae, Muraenesocidae, and Nettastomidae) by recent authors. Although the species is described in detail in this account, it cannot be definitely assigned to a family without major revision of these families. The species is now known from 19 specimens captured mostly near the continental slope of the eastern Pacific Ocean between Valparaiso, Chile, and Vancouver Island, B.C. Xenomystax rictus Garman 1899 should be considered a junior subjective synonym of X. atrarius Gilbert 1891.
Comparative Study of the Muscle Catheptic Activity of Some Marine Species
Authors: Wojtowicz M. B. , Odense P. H.
Published: April 2011

The hemoglobin-splitting activity and the autolytic- (endogenous) catheptic activity of the white skeletal muscle of 13 Atlantic fish species were measured and found to be low relative to the catheptic activity of other tissues. On the other hand, catheptic activities of lobster and crab claw muscles were high. Lobster tail muscle showed little activity, a factor perhaps contributing to its tougher texture relative to the claw muscle. The individual variations between samples of the same species were great and the ranges of the species overlapped each other with no evident phylogenetic distinction. The hemoglobin-splitting activity was always higher and was always directly correlated with the autolytic activity for each individual sample. Using an urea-free hemoglobin substrate pH optima were found in the range 3.0–3.6. Urea shifted the pH optima upwards approximately 0.4 unit. Fish muscle cathepsins were found to have the same level of activity as chicken muscle.
An Infrared Photographic Technique Useful for Studying Vascularization of Fish Gills
Authors: Davis John C.
Published: April 2011

An infrared photographic technique was used to study patterns of blood distribution within gills of intact trout. Injection of adrenaline in the subintestinal vein produced a marked change in photographic appearance of the gill as it appeared swollen with blood and more blood was visible in the lamellae at the gill filament tips. The technique appears useful for studying large changes in gill vascularization.
Adaptive Variation in Swimbladder Length and Volume in Dace, Genus Rhinichthys
Authors: Gee John H.
Published: April 2011

Relative growth in length and volume of swimbladder is described in four species of dace, genus Rhinichthys. Swimbladder volume varied widely in R. atratulus, R. cataractae, and R. osculus as they adjusted buoyancy by altering swimbladder volume, but variability was less in R. falcatus whose range was overlapped by the other three species. A variety of relative growth patterns in swimbladder length was found due mainly to the presence or absence of an inflection which, when present, varied at fork length of occurrence. Where ecological information was known, the length at occurrence of inflection corresponded to a change in environment occupied, from still to current. In the laboratory, R. atratulus and R. cataractae adjusted swimbladder volume to compensate for different water velocities. All age-groups of the former attained a greater buoyancy than the latter, while R. cataractae reached a lower negative buoyancy. Young R. cataractae made greater adjustments of swimbladder volume than older fish; the reverse occurred with R. atratulus. These adjustments resulted in a significant change in swimbladder length independent of age, except for R. cataractae from Lake Winnipeg which had very short swimbladders. The hypothesis that occurrence of the inflection in swimbladder length was caused by the shift from a still to current environment, resulting in a decrease in swimbladder volume and length was accepted for R. atratulus, but rejected for R. cataractae. An additional hypothesis based on environmental control is proposed.
Virulence and Persistence of Rough and Smooth Forms of Aeromonas salmonicida Inoculated into Coho Salmon (Oncorhynchus kisutch)
Authors: Anderson Douglas P.
Published: April 2011

Virulent isolates of Aeromonas salmonicida showed a majority of smooth colonies, while the attenuated isolates displayed mostly rough colonies. A lesion occurred at the site of inoculation when one of the rough forms was inoculated into yearling coho salmon, but few mortalities were recorded even though the rough forms were readily recovered from both the lesion and the kidney. The fish inoculated with the same dosage of smooth forms all died within 96 hr of inoculation.
Detection of Antibodies to Aeromonas liquefaciens in Fish by an Indirect Fluorescent Antibody Technique
Authors: Lewis D. H. , Savage N. L.
Published: April 2011

A technique for detecting antibodies in fish is described that may be of value in screening fish populations for various disease agents. The technique is based on the reaction between fluorescein-labelled antifish globulin and a fish antibody–antigen complex. The immune responses of Pimephales promelas, Notemigonus crysoleucas, and Fundulus grandis to Aeromonas liquefaciens were demonstrated by the technique.
Genetic and Environmental Sources of Variation in Length and Weight of Rainbow Trout (Salmo gairdneri)
Authors: Aulstad Dag , Gjedrem Trygve , Skjervold Harald
Published: April 2011

Rainbow trout (Salmo gairdneri) of three-year-classes (1967–1969) were produced from random mating, and one-year-class (1970) from inbreeding. The two first-year-classes were fullsib groups. Intraclass-correlations for body length in the 1967-year-class were: 0.16, 0.15, 0.09, and 0.17 at 90, 130, 355, and 485 days of age, respectively. The corresponding estimate for the 68-year-class was 0.25 at age 110 days. Phenotypic correlations between body length at different ages were high within seasons, but low between seasons.For the 1969-year-class the sire x dam interaction component was negative at ages 150 and 280 days, indicating that nonadditive gene effects were unimportant. Estimated heritabilities ranged from 0.0 to 0.40, those from the sire component being generally higher. Environmental differences between tanks were low, but not ignorable. The 1970-year-class, produced from first generation of fullsib mating, showed significant differences between inbred and control (noninbred) for mortality of eggs and fry, but not for body weight at age 75 days.
First Records of the Striped Bass, Morone saxatilis, in British Columbia Waters
Authors: Forrester C. R. , Peden Alex E. , Wilson R. M.
Published: April 2011

Two specimens of the striped bass (Morone saxatilis) were taken in British Columbia waters in 1971. One was taken off Port San Juan (48°30′N, 124°30′W) and one in Barkley Sound (48°58′N, 125°03′W). Previous most northerly published record for the Pacific coast was from Puget Sound, Washington.
Lipid Composition of the Queen Crab (Chionoecetes opilio)
Authors: Addison R. F. , Ackman R. G. , Hingley J.
Published: April 2011

Muscle tissue of the queen crab, Chionoecetes opilio, contained 0.75% lipid, 78.8% of which was phospholipid (chiefly choline phosphatides) and the balance mainly cholesterol. Viscera contained 13.6% lipid, the bulk of which was triglyceride. Fatty acid composition was generally similar to that of other marine species. However, 20:5ω3 was the major polyunsaturate (rather than the more usual 22:6ω3) and within the 18:1 series, the ω7 isomer was present in unusually large quantities.
Aging Round Whitefish (Prosopium cylindraceum) of the Leaf River, Ungava, Quebec, by Otoliths
Authors: Jessop B. M.
Published: April 2011

Ages assigned to 503 round whitefish (Prosopium cylindraceum (Pallas)) from the Leaf River on the basis of otoliths differed notably from those assigned on the basis of scales only for fish above age 8. The hyaline zones in otoliths corresponded to the scale annuli, and the growth increments in otoliths at various dates as percentages of the totals during the collection period were similar to those for scales. Otolith radius increased linearly with fork length, as did otolith weight with fish age.
Marking Larval Largemouth Bass with Radiostrontium
Authors: Carlson Clarence A. , Shealy Jr. M. H.
Published: April 2011

Largemouth bass (Micropterus salmoides) were marked by exposing newly-hatched prolarvae to 6.4, 11.3, and 16.8 μCi 85Sr/liter pond water for 7 days. Embryos were collected by pipette from nests in ponds and incubated to hatching in disposable aquaria m the laboratory. Radiostrontium accumulation from water continued throughout the first week of postembryonic life but was most rapid after the fourth day of exposure. In another study the techniques were found useful for quantifying predation on larval bass by aquatic invertebrates.
Distribution of Herring (Clupea harengus) Larvae Along the Southern Coast of Nova Scotia with Observations on Their Growth and Condition Factor
Authors: Sameoto D. D.
Published: April 2011

The distribution and abundance of herring larvae on the southern coast of Nova Scotia suggested the presence of a fall spawning population. Larvae were found in St. Margaret's Bay from late September to June. They showed a slower growth rate than larvae from the Clyde Sea, Scotland, and weighed less at a particular length than did larvae from the Clyde Sea and Boothbay, Maine. The larvae had a lower condition factor at 25 mm length than larvae from the North and Baltic Seas. No larvae were found on the Scotian Shelf during late May and early June, 1969, but were abundant during September and October. Herring spawning beds were reported from areas along the entire coast of Nova Scotia from Canso to Cape Sable.
Likelihood Analysis of Three-Way Contingency Tables
Authors: Lindsey J. K. , Nash F. W.
Published: April 2011

The three-way contingency table is considered as an analysis of variance problem. Since the appropriate distribution is multinomial rather than normal, the log likelihood ratios are used to make inferences instead of the variance ratios.
Effect of Thermal Stress on Predator Avoidance in Sockeye Salmon
Authors: Sylvester J. R.
Published: April 2011

Under laboratory conditions, predation rates of yearling coho salmon (Oncorhynchus kisutch) on sockeye salmon fry (Oncorhynchus nerka) increased with increasing acclimation temperature. Elevated temperature doses significantly decreased survival of sockeye salmon fry. The results suggest that under natural conditions, sudden increases in water temperature could alter predator–prey interactions of some fish by increasing predation mortalities.
Synonymy of Sebastes caenaematicus with Sebastes borealis, and Range Extension Record
Authors: Westrheim S. J. , Tsuyuki H.
Published: April 2011

Sebastes caenaematicus Tsuyuki and Westrheim (1970) is synonymized with Sebastes borealis Barsukov (1970). Recorded geographical range of S. borealis has been extended southward in the eastern Pacific Ocean at least 600 miles, to Cape Flattery, Wash. (48°23′N lat), and probably 1000 miles, to Eureka, Calif. (40°46′N lat).
Factors of Ecologic Succession in Oligotrophic Fish Communities of the Laurentian Great Lakes
Authors: Smith Stanford H.
Published: April 2011

Oligotrophic fish communities of the Great Lakes have undergone successive disruptions since the mid-1800s. Major contributing factors have been intensive selective fisheries, extreme modification of the drainage, invasion of marine species, and progressive physical–chemical changes of the lake environments. Lake Ontario was the first to be affected as its basin was settled and industrialized earliest, and it was the first to be connected by canals to the mid-Atlantic where the alewife (Alosa pseudoharengus) and sea lamprey (Petromyzon marinus) which ultimately became established in the Great Lakes were abundant. Oligotrophic fish communities were successively disrupted in Lakes Erie, Huron, Michigan, and Superior as the affects of population growth, industrialization, and marine invaders spread upward in the Laurentian drainage.The degree and sequence of response of families offish and species within families differed for each factor, but the sequence of change among families and species has been the same in response to each factor as it affected various lakes at different times. The ultimate result of the disruption of fish communities has been a reduction of productivity of oligotrophic species that ranges from extreme in Lake Ontario to moderate in Lake Superior, and which has reached a state of instability and rapid change in the upper three Great Lakes by the rnid-1900s similar to the situation in Lake Ontario in the mid-1800s. Since oligotrophic species (primarily salmonines, coregonines, and deepwater cottids) are the only kinds of fish that fully occupied the entire volume of the deepwater Great Lakes (Ontario, Huron, Michigan, and Superior), the fish biomass of these lakes has been reduced as various species declined or disappeared. In Lake Erie, which is shallow, and in the shallow bays of the deep lakes, oligotrophic species were replaced by mesotrophic species, primarily percids, which have successively increased and declined. All oligotrophic species are greatly reduced or extinct in lakes Ontario and Erie, and are in various stages of decline in lakes Huron, Michigan, and Superior, from greatest to least, respectively. The percids appear to be near the end of their sequence of succession in lakes Erie, Ontario, and Huron (primarily Saginaw Bay) where only the yellow perch (Perca flavescens) remains abundant. The yellow perch appears to be on the brink of decline in Lake Erie, which has been more severely influenced by water quality change than the other lakes.
Brienzersee, Thunersee, and Bielersee: Effects of Exploitation and Eutrophication on the Salmonid Communities
Authors: Roth H. , Geiger W.
Published: April 2011

These three lakes of the Aare Valley in Switzerland have been subjected to increasingly intense fisheries exploitation in recent decades. Fishing intensities have been roughly comparable in the three lakes in any particular year. Attempts at introducing non-native species have been made in all lakes but none of the attempts have had appreciable effect. Nutrient loading, due to domestic wastes predominantly, has been much greater with the downstream Bielersee than the upper two lakes, and somewhat greater in the Thunersee than the highest lake, Brienzersee. But even the latter is now showing symptoms of nutrient stress, in that populations of indicator phytoplankters have recently erupted.Ecological effects ascribed to the fishery include a marked reduction in stocks of Arctic char due to angling and pelagic coregonines due to commercial gillnetting. The latter taxa have recently shown pronounced fluctuations in year-class abundance. An energetic hatchery program has mitigated exploitation effects to some extent.Total stocks of fishes have increased due to eutrophication with initial increases in all fish taxa, except perhaps Arctic char. The cyprinids, percids, and esocids have increased in the Bielersee to a far greater extent than the salmonids with a result that the latter are now contributing smaller proportions of the catches. The cyprinids have little economic value and their burgeoning stocks are creating ecological and economic problems in the Bielersee as well as many other Swiss lakes. The cyprinids apparently cannot be effectively controlled by piscivores such as esocids, even where the latter are assisted by a hatchery program.
Loch Lomond: Man's Effects on the Salmonid Community
Authors: Maitland Peter S.
Published: April 2011

Loch Lomond, the largest area of fresh water in Great Britain, has been utilised by man for many hundreds of years. There are fifteen species offish at present in the loch: all of these are native. Several of them have formed the basis of commercial and sport fisheries in the past but the only two species of importance at present (as sport fish) are salmon (Salmo salar) and trout (Salmo trutta). Man has influenced the loch in ways other than fishing: several fish species have been introduced (none successfully); nutrient input is increasing; loch water is used for domestic and industrial supply; many forms of recreation take place on the loch; and it is of major importance as an amenity. In spite of these stresses there is no indication of any major change in the fish populations within recorded time; nor is there any evidence that they will alter in the foreseeable future, providing a rational conservation programme is developed for the area.
Lake Michigan: Effects of Exploitation, Introductions, and Eutrophication on the Salmonid Community
Authors: Wells LaRue , McLain Alberton L.
Published: April 2011

Lake Michigan surface area is 22,400 square miles and its main depth is 276 ft. Its fauna is generally typical of North American oligotrophic lakes. The original fish populations included 10 coregonines and one salmonine. The lake whitefish, the lake herring, and the lake trout were most abundant.Man's activities have caused great changes in the lake in the past 120 years. Although changes in water chemistry and in the lower biota have been generally modest (except locally), those in salmonid communities have been vast. Exploitation, exotic fish species (especially the sea lamprey and alewife), and accelerated eutrophication and other pollution, all have played a role in bringing about the modifications (mostly marked declines in abundance) in salmonid communities.Commercial exploitation was largely responsible for the changes in the salmonid communities before the invasion of the lamprey (1936), although eutrophication and other pollution, and alterations of spawning streams, also were important. The lamprey and alewife (first reported in 1949), however, have exerted a greater impact than the other factors in recent decades.
Lake Erie: Effects of Exploitation, Environmental Changes and New Species on the Fishery Resources
Authors: Hartman W. L.
Published: April 2011

In no other lake as large as Lake Erie (surface area, 25,690 km2) have such extensive changes taken place in the drainage basin, the lake environment, and the fish populations over the last 100 years. Deforestation and prairie burning led to erosion and siltation of valuable spawning grounds. Marsh spawning areas were drained. Lake-to-river spawning migrations were blocked by mill dams. Accelerated cultural nutrient loading increased total dissolved solids by nearly 50% (1920–70). Average summer water temperatures increased 1.1 C. Phytoplankton and zooplankton abundance increased severalfold. Severe oxygen depletion developed in the bottom waters of all three basins of the lake. Lake sturgeon were fished out as nuisance fish in the late 1800s. The commercial fisheries for lake trout, lake whitefish, and lake herring collapsed by 1940 and those for blue pike and walleye by 1960. Yellow perch production became unstable in the 1960s. The effects of exploitation, environmental changes, and new species on these fish population changes are discussed.
The Future of Salmonid Communities in Fennoscandian Lakes
Authors: Grimås Ulf , Nilsson Nils-Arvid , Toivonen Jorma , Wendt Curt
Published: April 2011

In trying to make predictions for the future of the Fennoscandian lakes it is difficult to disregard the obvious threat of a common protein deficiency in the world population. At the moment, however, there is a trend in the fishery away from a commercial and subsistence gillnet fishery towards a use of the lakes for recreational purposes. Eutrophication induced by man is proceeding everywhere, although governmental authorities are aware of this threat. In some large lakes the process may have reached an optimum where it is still favouring production of relatively large yields of some important species of fish. Exploitation of some species, for example salmonids and sander, is in some cases overly intensive, but is not yet regarded as a serious problem. Introductions of "exotic" species have had little influence on native stocks. The release of hatchery-reared landlocked salmon, rainbow trout, and lake trout will hopefully raise the value of the fishery in some lakes in the future. Pollution by toxic substances such as mercury, DDT, and PCB, and the fall-out of SO2 from the atmosphere, are at present the most serious threats to the fishery.
Effects of Eutrophication on Salmonid Communities in Oligotrophic Lakes
Authors: Colby P. J. , Spangler G. R. , Hurley D. A. , McCombie A. M.
Published: April 2011

Oligotrophic lakes respond to progressive eutrophication by a sequence of predictable events. Increased nutrient loads and subsequent increased plant production result in alterations in the abiotic environment, including changes in the color and transparency of the water, increased turbidity, oxygen depletion in the hypolimnion, and increased chemical stratification. The physico-chemical changes precipitate biotic changes among the phytoplankton, littoral algae, zooplankton, and benthos. The salmonid community may respond initially with an increased body growth rate in various taxa and a higher incidence of parasitism, but later inhibition of natural reproduction occurs, and finally, the taxa are replaced by others that can survive in the changed environment.A relation between natural nutrient loading (expressed in terms of a morphoedaphic index) and yield (both quantitative and qualitative) is proposed as an aid to determining the natural successional status of a lake. Knowing the natural baseline of a particular lake the fisheries managers can judge the nature and size of responses due to cultural nutrient loading and then alter the rate of cultural nutrient loading to modify the ecological effects, or they can use biological engineering to capitalize on the present conditions.Among the most important effects of eutrophication is the increased vulnerability of sedentary discrete stocks to changes in other stresses such as fishing.
Mobilization of Mercury from Sediments into Guppies (Poecilia reticulata)
Authors: Gillespie D. C.
Published: April 2011

Guppies (P. reticulata) were exposed in aquaria to aerobic and anaerobic sediments to which various forms of mercury were added and to sediments from two sites of industrial pollution. Whole body levels of total mercury (atomic absorption analysis) in these fish were used as a measure of mobilization of mercury from these sediments. Spot checks for methylmercury were carried out at intervals during the tests. Under aerobic conditions there was little mobilization of mercury from sediments to which mercuric chloride or sulphide had been added but total mercury concentrations rose rapidly in fish exposed to sediments containing metallic mercury.The proportion of methylmercury in fish reached maxima of 30% for metallic mercury, 40% for mercuric chloride, and 45% for mercuric sulphide. In anaerobic sediments, total mobilization was low and only mercuric chloride was significantly methylated (40% of the total in the fish).Both mobilization and methylation were proportionately greater in industrial sediments with a low mercury content than in sediments with a higher mercury content. Enrichment of sediments with lignosulphonate showed no real effects aerobically, possibly because of the chelation properties of the preparation used. Anaerobically, lignosulphonate stimulated methylation of mercury.The levels of mercury and methylmercury found in fish are consistent with data from nature. Some of the implications of the results are discussed.
Trials with an Automated Plankton Counter
Authors: Fulton John
Published: April 2011

An opto-electronic plankton counter-sizer counted samples of zooplankton in seven size classes about six times faster, with greater precision and likely greater accuracy than human sorters. Samples used in the trials were of low diversity, and dominant taxa in each of the seven size classes could be quickly identified under a low-power microscope before machine counts were made. Sample concentrations of less than 3000 organisms per liter were found to be optimal for machine counting. In samples of greater concentration, coincident passage of two or more small organisms caused a bias in favor of the larger size classes.
Use of Otoliths in Identifying Herring Stocks in the Southern Gulf of St. Lawrence and Adjacent Waters
Authors: Messieh Shoukry N.
Published: April 2011

Examination of 1423 herring from various fisheries in the southern Gulf of St. Lawrence and adjacent waters indicates that otoliths can be used as "natural tags" for identifying herring stocks. Two types of otoliths are described: an S-type characterizing spring-spawning herring and an A-type characterizing autumn-spawning herring. Over 97% of herring from spring and autumn fisheries had otoliths of the respective types. There appeared to be sub-divisions within each type.The distinguishing of these otolith types provides evidence that spring- and autumn-spawning herring mix on American Bank and off Shippegan in the Gulf of St. Lawrence and in Chedabucto Bay. The validity of otolith types as criteria for separating herring stocks was supported by comparison with relations of otolith length to fish length and with fin ray counts.
Influence of Salinity, Temperature, and Exercise on Plasma Osmolality and Ionic Concentration in Atlantic Salmon (Salmo salar)
Authors: Byrne J. M. , Beamish F. W. H. , Saunders R. L.
Published: April 2011

In unexercised Atlantic salmon (Salmo salar), plasma osmolality and Na+ and Ca++ concentrations varied little at temperature-salinity combinations of 3, 5, 10, and 14 C and 0, 15, and 30‰. Plasma K+ tended to increase with increase in temperature. Cl− values were similar at 5 and 14 C. At 1 C and 0‰, lower plasma osmolalities indicated reduced ability to osmoregulate. At 1 C and 30‰, elevated osmolalities and ionic values and mortalities indicated severe osmotic stress.After exercise for 2 hr at 3–4 body lengths/sec at 5 and 14 C, salmon in salinities of 0 and 15‰ had osmolalities and ionic values the same as or little changed from unexercised values. There were marked increases in the values following exercise in 30‰.
Ecological Segregation Between Longnose and Blacknose Dace (Genus Rhinichthys) in the Mink River, Manitoba
Authors: Gibbons John R. H. , Gee John H.
Published: April 2011

Longnose and blacknose dace occur in greatest abundance in the middle zone of the Mink River, and segregation in environment occupied is marked. Newly emerged longnose fry were found in stream margins, but by the middle of their first summer had moved into fast riffles (>45 cm/sec) where they completed their life cycle. Blacknose fry also occupied stream margins, remaining there for up to one year. Thereafter they were found mostly in channels of moderate current. Coexistence of fry of the two species in stream margins is minimized by earlier hatching of longnose dace. Diet of longnose and blacknose dace, consisting of aquatic insect larvae and nymphs, was strikingly similar.
Acute Zinc Toxicity to Rainbow Trout (Salmo gairdneri): Confirmation of the Hypothesis that Death is Related to Tissue Hypoxia
Authors: Burton Dennis T. , Jones Alma H. , Cairns Jr. John
Published: April 2011

Acute heavy metal toxicity to fish has been attributed to the coagulation or precipitation of mucus on the gills and/or to cytological damage to the gills. The physiological mechanism of death by either of the above causes is related to a breakdown in gas exchange at the gills. This study of acute zinc toxicity to rainbow trout (Salmo gairdneri) supports an earlier hypothesis that modification of the gas exchange process at the gills creates hypoxia at the tissue level. Tissue hypoxia appears to be a major physiological change preceding death once the gas exchange process at the gills is no longer sufficient to supply the oxygen requirements of the fish.
Incidence of Vibrio parahaemolyticus in Shellfish from Eight Canadian Atlantic Sampling Areas
Authors: Thomson W. K. , Thacker C. L.
Published: April 2011

During July to October, 78 cultures of Vibrio parahaemolyticus, closely resembling strains isolated from human cases in Japan, were isolated from clams, mussels, and oysters collected from eight Canadian Atlantic areas. Approximately 22% of the shellfish examined yielded this species, about half being detectable by direct plating, and the rest after enrichment before plating.
Mercury in Harbour Porpoises (Phocoena phocoena) From the Bay of Fundy Region
Authors: Gaskin D. E. , Ishida K. , Frank R.
Published: April 2011

During 1969–71, 41 muscle and 20 liver samples were collected from harbour porpoises (Phocoena phocoena) in the Bay of Fundy region. These tissues were analyzed for total mercury content. Total Hg levels ranged from 0.21 to 1.92 ppm (average 0.75) in muscle tissue of males and from 0.26 to 2.58 ppm(average 1.02) in muscle tissue of females; from 0.89 to 18.30 ppm in liver tissue of males and from 0.55 to 91.30 ppm in liver tissue of females. Averages for the two latter series would be meaningless. A limited number (four muscle and six liver samples) of determinations of the methylated fraction were also made. In the muscle, Hg was virtually 100% methylated; in the liver the methylated fraction varied from 7.4 to 41%, being lowest in livers with highest total Hg.
Scales as a Means of Aging Dover Sole (Microstomus pacificus)
Authors: Demory Robert L.
Published: April 2011

An aging technique by means of scales is described for Dover sole (Microstomus pacificus). Agreement after two readings was 50%, but increased to 80% after three readings. Validation of the first annulus was established after examination of juvenile scales over a period of time during the first year of benthic residence. Location of the first annulus is contrary to published accounts. Scales offer a superior method of aging, especially for older fish. Interpretation and accuracy of scales from adult Dover sole males that remain in deep water one or more years is questionable.
Unusual Occurrence of the Brook Stickleback (Culaea inconstans) in the Mackenzie River, Northwest Territories
Authors: Falk M. R.
Published: April 2011

Two specimens of the brook stickleback (Culaea inconstans) were taken in the mouths of Pierre and Tsital Trien creeks near Arctic Red River on the Mackenzie River during 1971. Previous most northerly published records were from the south shore of Great Slave Lake. The specimens may have been carried downstream by spring floods and may not represent a resident population.
Paralytic Shellfish Poison and Melanin Distribution in Fractions of Toxic Butter Clam (Saxidomus giganteus) Siphon
Authors: Price R. J. , Lee J. S.
Published: April 2011

Frozen toxic butter clam (Saxidomus giganteus) siphons were fractionated and each fraction was bioassayed for paralytic shellfish poison (PSP) and chemically analyzed for melanin. Sonication removed over 50% of the melanin from the siphons and this fraction contained nearly 50% of the PSP initially present in the siphons. The data presented further implicate melanin as a PSP binding agent in vivo.
Effects of Several Factors on the Growth of the American Lobster (Homarus americanus) in Captivity
Authors: McLeese D. W.
Published: April 2011

With existing methods, there is little possibility of growing lobsters economically through a moult in captivity.In initial experiments on effects of temperature, feeding rate, diet, and sex on growth of spring-caught lobsters of 0.6–1.0 lb (0.28–0.45 kg) in captivity, gross weight of all 19 groups decreased by an average of 36% by 6 or 8 months (McLeese 1972).In these experiments on effects of maturity and storage density, lobsters of 1.0 lb (0.45 kg), maintained at four storage densities at 15 C, were fed fish, squid, and beef liver at 6% of their weight per week. Moulting occurred mainly from early July to late October with only a few others moulting by March (10 months). There was no difference in weight increment for mature and immature lobsters. Mean increments in length and weight were inversely related to storage density. Heavy mortality in one group was caused in part by lobster blood disease, gross weight in the remaining six decreased by an average of 2.5% by 6 months, and 19% by 10 months, corresponding with mortality of 17.5 and 29.4%.
Salmon-Canning Waste Water as a Microbial Growth Medium
Authors: Strasdine G. A. , Melville Joanne M.
Published: April 2011

Salmon-canning waste water was shown to support the growth of six species of bacteria both as a complete growth medium and as a supplementary source of available nitrogen. On this basis, the waste water compared favourably to six commercially available sources of nitrogen used routinely in microbiological growth media. Possibilities are discussed for the microbiological conversion of salmon-canning wastes into useful and marketable products.