bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological, Physiological, and Ethological Differences Between Walleye (Stizostedion vitreum vitreum) and Pikeperch (S. lucioperca)
Authors: Marshall T. R.
Published: April 2011

A review of the literature indicated that pikeperch (Stizostedion lucioperca) are generally more tolerant than walleye (S. vitreum vitreum) of a wide range of environmental sources of stress, such as organic pollution, sedimentation, and fluctuating water levels. This advantage presumably arose from numerous morphological and physiological specializations which are expressed through appropriate behavioral patterns. Of prime importance is the ritualistic redd building and guarding behavior developed by the pikeperch which contributes to a consistently successful rate of fertilization and lowered mortality of their eggs and larvae. In addition, pikeperch have a much higher fecundity and require a less specific set of spawning conditions than do walleye. These attributes allow the pikeperch much greater reproductive success under stressful conditions and thus more flexibility in their range. Key words: behavior, cultural eutrophication, environmental stress, morphology, physiology, pikeperch, reproductive potential, reservoirs, Stizostedion, walleye
Factors Affecting the Shift in Predominance from Eurasian Perch (Perca fluviatilis) to Roach (Rutilus rutilus) in the Kličava Reservoir, Czechoslovakia
Authors: Pivnička K. , Švátora M.
Published: April 2011

A shift in predominance from Eurasian perch (Perca fluviatilis) to roach (Rutilus rutilus) in the Kličava Reservoir in 1964, 10 yr after filling, was attributed mainly to a marked decline in the ratio of female to male perch spawners. The ratio was about 1:4 for perch and unity for roach. Fecundity of perch was about 25% that of roach which, together with the decline in spawning females, probably contributed to smaller year-classes. The decline in growth rate of perch in response to increasing abundance was greater than that for roach. Under equal environmental conditions, roach is also more productive than perch. Key words: Percidae, Perca, Rutilus, Kličava Reservoir, Czechoslovakia, shift in predominance, fecundity, sex ratio, methodology, growth–abundance relationships
Limnological Characteristics of Ontario Lakes in Relation to Associations of Walleye (Stizostedion vitreum vitreum), Northern Pike (Esox lucius), Lake Trout (Salvelinus namaycush), and Smallmouth Bass (Micropterus dolomieui)
Authors: Johnson M. G. , Leach J. H. , Minns C. K. , Olver C. H.
Published: April 2011

Commonest lake types of the 15 combinations of four fish species (walleye, Stizostedion vitreum vitreum; northern pike, Esox lucius; lake trout, Salvelinus namaycush and smallmouth bass, Micropterus dolomieui) were walleye–pike (22%), pike "only" (19%), lake trout "only" (16%) and smallmouth bass "only" (10%). Lake trout–walleye and lake trout–walleye–smallmouth bass types were extremely rare. Lake depth and area were variables of greatest significance in distinguishing lake types by discriminant analysis. Climatic factors explained the general geographic distribution of smallmouth bass. Hypotheses to explain the low frequency of walleye in small lakes include possibilities of (1) low probability of successful coexistence of pike and walleye, (2) lack of wind fetch to clear spawning areas, and (3) "Lebensraum requirement" of the walleye. Key words: limnology, Percidae, methodology, Ontario lake types, Stizostedion vitreum vitreum, Esox lucius, Salvelinus namaycush, Micropterus dolomieui, distribution, associations
Yield Properties and Structure of Boreal Percid Communities in Ontario
Authors: Adams G. F. , Olver C. H.
Published: April 2011

A synoptic review of yield data for 70 northern Ontario lakes from 1917 to 1973 showed that percids mainly walleye (Stizostedion vitreum vitreum) constituted about one-third, by weight, of the total fish yield. This relationship, which was independent of fishing effort, lake size, and lake productivity, is considered to be an emergent property of this type of fish community and represents a degree of homeostasis within the community under exploitation. The relation of percid yield to theoretical yield (based on the morphoedaphic index — MEI) reflected organizational structure and suggested the existence of a community (percid) component within the MEI, and from this we recommend upper limits of percid harvest for boreal percid lakes.Most (83%) of the 70 lakes had an average total yield of less than 2.5 kg∙ha−1∙yr−1, 53% (37 lakes) yielding less than one-half of the theoretical yield (average 3.4 kg∙ha−1∙yr−1). Long-term average yields exceeded the theoretical maximums in only 11 lakes. Mesotrophic to slightly eutrophic waters appeared as optimum for percid yields.Inferences from the data suggest an unexploited boreal percid community is characterized by high community stability and low net community production with resiliency low because of the low productive capacity of the waters. A yield index (RYI), which was assumed to reflect both effort and vulnerability to exploitation, showed that fishing intensity tended to be higher on the smaller, less productive lakes in this study. Key words: Percidae, Stizostedion, community ecology, yield properties, management implications
Interrelations Between Walleye (Stizostedion vitreum vitreum) and Smallmouth Bass (Micropterus dolomieui) in Four Northeastern Minnesota Lakes, 1948–69
Authors: Johnson Fritz H. , Hale John G.
Published: April 2011

Smallmouth bass (Micropterus dolomieui) introduced from 1945 to 1948 into four rocky, infertile northeastern Minnesota lakes with established walleye (Stizostedion vitreum vitreum) populations reached maximum abundance in 9–15 yr and then declined to low numbers within 2–4 yr. In three, walleyes declined as the bass increased and in the fourth there was a simultaneous rise of walleye and bass followed by increased abundance of walleye with the decline of bass. Interspecific competition for spawning sites, shoal habitat, or food did not appear to be factors in the fluctuations in abundance. Growth of both species was density-dependent implying that intraspecific competition may have been the main factor. Also, predation of young walleye by bass may have been a factor in failure of walleye year-classes. Key words: Percidae, species interrelations, Stizostedion, Micropterus, competition, diet, populations fluctuations, habitat use, density
Food Consumption of Walleye (Stizostedion vitreum vitreum) and Sauger (S. canadense) in Relation to Food Availability and Physical Conditions in Lake of the Woods, Minnesota, Shagawa Lake, and Western Lake Superior
Authors: Swenson William A.
Published: April 2011

Measurement of walleye (Stizostedion vitreum vitreum) daily food consumption rates and prey density in Lake of the Woods, Minnesota, Shagawa Lake, and western Lake Superior showed a general relationship exists between the two variables. Daily food consumption increased from 1 to 3% of body weight at prey densities up to 400 mg∙m−3. Abundance of age 0 yellow perch (Perca flavescens) in Lake of the Woods, Minnesota, and Shagawa Lake resulted in much higher prey densities and daily food consumption to 4% of body weight. In Lake Superior where walleye fed exclusively on rainbow smelt (Osmerus mordax), prey density did not exceed 300 mg ∙m−3 and daily food consumption averaged less than 2.5% of body weight.Hourly food consumption by walleye changed in response to variation in prey availability and light intensity. Night feeding predominated during July and August when walleye fed on pelagic age 0 yellow perch. Feeding appeared to be continuous or crepuscular during June and September when larger demersal prey fish or invertebrates were eaten. Food consumption declined when prey concentrated near aquatic macrophytes and under conditions of high light intensity. Walleye daily food consumption was not influenced by a change in temperature from 20 to 15 °C.Daily food consumption of Lake of the Woods, Minnesota sauger (Stizostedion canadense) averaged less than walleye and was influenced by wave activity and prey density. Demersal prey was utilized by sauger throughout the 24 h-day. Key words: Percidae, food consumption, behavior, feeding, walleye, Stizostedion vitreum vitreum, sauger, S. canadense, light
Unexploited Percid Populations of West Blue Lake, Manitoba, and their Interactions
Authors: Kelso J. R. M. , Ward F. J.
Published: April 2011

West Blue Lake, Manitoba, essentially unaffected by man, sustains populations of yellow perch, Perca flavescens, and walleye, Stizostedion vitreum vitreum, which interact in two fundamental ways: perch are a major source of energy for walleye and the two species share common food organisms.Perch adults, juveniles and fry generally contributed 80–90% of the energy required for the annual walleye production (340 kg) and, on the basis of conversion experiments, provided for at least 1.7 kg∙ha−1 of the observed production of 2.1 kg∙ha−1. The brief summer growth period, combined with moderate mortality, caused biomass to reach a maximum in early fall at which time production ceased.Although walleye utilized yellow perch as its basic energy supply, behavioral differences tended to offer protection to juvenile and adult perch. Walleye were active at night, whereas older perch w ere inactive. Age 0 perch, during their epilimnetic phase, on the other hand, were active at night and vulnerable to walleye predation providing at least 18% of the observed walleye production.Walleye and yellow perch shared the same food resources although at different times and to different degrees. This competition was most intense between walleye (> 25 cm) and adult perch (> 12 cm). A main food item shared was amphipods. Most other food items (sticklebacks, mayflies, crayfish) were also shared but none in equal proportions by the two percids.Neither of the percid species showed a preponderance of older individuals and both showed evidence of strong and weak year-classes — walleye to a greater degree. Also, for walleye at least, production was only 2.1 kg∙ha−1, and biomass appeared to be stable, approximately 900 kg. Growth for both species was less than most other percid communities and was restricted to a brief, ≈ 80 day, period. Key words: unexploited, yellow perch, walleye, feeding, behavior, production, population structure
Trends in Harvests of Pikeperch (Stizostedion lucioperca), Eurasian Perch (Perca fluviatilis), and Northern Pike (Esox lucius) and Associated Environmental Changes in Lakes Mälaren and Hjälmaren, 1914–74
Authors: Rundberg Hugo
Published: April 2011

The fish communities in and the trophic states of lakes Mälaren and Hjälmaren have changed gradually since the late 1700s. In both lakes, pikeperch (Stizostedion lucioperca), Eurasian perch (Perca fluviatilis), and northern pike (Esox lucius) are important species in the recreational and commercial fishery. Pikeperch has increased from an unimportant species to predominance in both lakes. The importance of Eurasian perch however, has decreased markedly. The most likely explanation for these changes is increased cultural eutrophication. Key words: Percidae, pikeperch, Eurasian perch, northern pike, harvests, eutrophication, community change, behavior
Changes in Fish Community of Klíčava Reservoir with Particular Reference to Eurasian Perch (Perca fluviatilis), 1957–72
Authors: Holčík Juraj
Published: April 2011

Soon after the 1955 filling of the 60 ha mesotrophic Klíčava Reservoir in Czechoslovakia, the fish fauna started to change. Generally, lithophils were replaced by phytophils and then by ecologically more plastic species. Fish biomass increased in the first 12 yr from 65 to 236 kg/ha, but after 1967 dropped to about 170 kg/ha. Increased biomass and density of piscivores were responsible for the decline. Among the piscivores the most important role was played by the pikeperch (Stizostedion lucioperca) rather than the Eurasian perch (Perca fluviatilis) or northern pike (Esox lucius). Cyclical changes in the age structure of the perch population and the periodical occurrence of many young resulted from fluctuations in the rate of cannibalism, which affected the density of the fry and yearlings. A decline in zooplankton biomass and disappearance of larger zooplankters in the first 5–6 yr of the reservoir were due to increased density of fish, especially perch, which fed on zooplankton. Synchronous predation by piscivores and zooplanktivores produced a nearly stable zooplankton biomass in the later years of the reservoir. The perch is a highly specialized species which behaves in the fish community more or less autonomously, because it is able to control its own density in accord with its food resources. The above conclusions are based on a literature review and analyses of new data. Key words: Percidae, community ecology, Perca, biomass, density, production, predation
Exploitation of Walleye (Stizostedion vitreum vitreum) in Lac Des Mille Lacs, Northern Ontario, by Commercial and Sport Fisheries, 1958–75
Authors: Elsey C. A. , Thomson R. T.
Published: April 2011

Harvests by three types of gear from Lac des Mille Lacs showed considerable differences in size selection of walleye (Stizostedion vitreum vitreum). Angling gear was most selective for smaller walleye (primarily 4–6 years old) and commercial gill nets and trap nets were most selective for larger walleye (primarily 5–11 years old), indicating there was not effective competition for fish of the same size. The great difference in size selectivity of the gears should serve as a caution against basing inferences about the status of stocks based on harvest from a single or similar gear.From 1971 to 1975 the total annual harvest (5.24 kg/ha) exceeded the theoretical potential yield (3.91 kg/ha) by 34%.The large number of age-groups (1–12), the high sport fishery catch per unit of effort (0.40 fish per man-hour) and the lack of appreciable change in rate of growth suggested no inimical effects on the walleye fishery due to exploitation.Walleye accounted for 62% of the total harvest (1971–75) reflecting both the preference for this species and their vulnerability to conventional (passive) commercial gear. The sport fishery harvest for the same period accounted for 92% of the total harvest. Key words: Percidae, exploitation, Stizostedion, gear selectivity
Walleye (Stizostedion vitreum vitreum) and Yellow Perch (Perca flavescens) Populations and Fisheries of the Red Lakes, Minnesota, 1930–75
Authors: Smith Jr. Lloyd L.
Published: April 2011

In an investigation of the commercial fishery of Red Lakes, Minnesota, for the 46-yr period 1930–75, catch statistics were analyzed, and the dynamics of the perch and walleye populations were examined. Mean annual yields of walleye for two statistical periods, 1930–53 and 1954–75, were 309,900 and 245,100 kg, respectively for walleyes, and 96,400 and 109,500 kg for perch. Annual abundance (CPE based on average catches per day per 5-net units of gill nets) varied from 3.8 to 64.6 kg for walleye, and from 2.5 to 34.4 kg for perch. Causes of fluctuations in harvestable stock were directly related to strength of year-classes and to growth rate during the season of capture. Year-class strength was not related to the abundance of parent stock or of potential predators. The respective strengths of year-classes of perch and walleye in the same year were positively correlated (r = 0.859, P < 0.01), and are directly related to climatic factors. Growth rate of walleye in different calendar years varied from +30.7 to −42.2% of mean growth, and that of perch from +13.4 to −8.6% (1941–56). Growing season began in mid-June and was almost over by September 1. Walleye yield could be enhanced by starting harvest July 1 instead of early June. Perch yield could be improved by harvesting small perch. Key words: Percidae, Perca, population dynamics, Stizostedion, long-term yield
Dynamics of the Walleye (Stizostedion vitreum vitreum) Population in Escanaba Lake, Wisconsin, 1955–72
Authors: Kempinger James J. , Carline Robert F.
Published: April 2011

Harvest and population dynamics of warmwater fish populations in Escanaba Lake have been under study since 1946, when complete creel census was initiated. Walleye (Stizostedion vitreum vitreum) and yellow perch (Perca flavescens) were among the most important species in the sport catch. The purpose of this report is to describe dynamics of the walleye population from 1955 to 1972.Annual densities of age 3 and older walleye in spring ranged from 13 to 52/ha (mean = 34) and standing crops averaged 12.3 kg/ha. Annual densities of fall fingerlings appeared to be the most important factor influencing size of adult populations. We were unable to isolate factors that governed densities of fall fingerlings. Year-class strength was not affected by water temperatures during incubation nor by size of fall fingerlings. Growth rates of fingerling walleye were density-independent. Survival of fingerlings to age 3 averaged 12% annually; survival was not influenced by size of fingerlings nor by density of potential predators. We found no evidence to suggest that cannibalism had any effect on density of fingerlings or their survival to age 3. Total mortality of adult walleye averaged 47% annually and exploitation rate was 28%. Ricker's (1975) equilibrium yield model was used to assess possible effects of a size limit on walleye yields. We concluded that a size limit would lead to an increase in population biomass, a decrease in growth, and that yields would not change greatly. Key words: Percidae, population dynamics, Stizostedion, harvest, abundance, density, regulations, survival, production, equilibrium yield, biomass
Percids in the Canadian Waters of Lake Huron
Authors: Spangler G. R. , Payne N. R. , Winterton G. K.
Published: April 2011

Percids have never dominated the commercial catch from Canadian waters of Lake Huron but coincident with declining salmonid production, they contributed about 17% of the commercial landings from 1940 to 1975. Walleye (Stizostedion vitreum vitreum) production declined gradually over the past century whereas yellow perch (Perca flavescens) production increased irregularly since 1910.Walleye occur in relatively discrete stocks associated with rivers, inlets, and estuaries in the North Channel and Georgian Bay whereas southern Lake Huron stocks are seasonal residents of the southeastern rim of the main basin. Yellow perch are ubiquitous throughout the littoral waters of the lake. Growth rates of walleye are similar to those for more southerly populations in the Great Lakes and year-class strength is highly variable. Angling and commercial fishing contribute significantly to mortality rates in exploited stocks but deteriorating environmental conditions are probably more important to the persistence of walleye stocks in Lake Huron. At least one stock is presently threatened by industrial acidification of the watershed. Key words: Percidae, Lake Huron, production, population biology, Stizostedion, Perca
Changes in Percid Populations and Species Interactions in Lake Erie
Authors: Nepszy Stephen J.
Published: April 2011

Changes in the percid community of Lake Erie from 1915 to 1975 are delineated mainly from recently published material. Sauger (Stizostedion canadense), blue pike (S. vitreum glaucum), walleye (S. vitreum vitreum), and yellow perch (Perca ftavescens) are the percids which have been affected by exploitation, eutrophication and the presence and proliferation of colonizing fish species. Changes in habitat, fishing techniques and gear have also affected percid and nonpercid interactions.Yellow perch, presently the most abundant percid, have experienced irregularity in recruitment, lack of strong year-classes, and increased exploitation. The concern over the status of yellow perch and walleye has led to some important management initiatives. Improved regulation of exploitation and present efforts by United States and Canadian government agencies to improve Great Lakes water quality, are expected to improve the success for long-term maintenance of percids in Lake Erie. Key words: Percidae, populations, Lake Erie, habitat change, exploitation, management, Stizostedion vitreum vitreum, S. canadense, S. vitreum glaucum, Perca flavescens
Reproductive Guilds of Percids: Results of the Paleogeographical History and Ecological Succession
Authors: Balon Eugene K. , Momot Walter T. , Regier Henry A.
Published: April 2011

A holistic picture of the Percidae is attempted, exploring the theory of reproductive guilds. Seven guilds encompass all 163 species; forms related closely in terms of Linnean taxonomy may belong to very different guilds. Adaptations in spawning ground selection, other reproductive behavior and morpho-physiological features of early ontogeny all center on respiration and protection against predators. The adaptation of guarding enables survival in low densities as well as in an environment with decreasing oxygen content, or enables invasion of such an environment. The paleogeographical origin and distribution of percid fishes are reconstructed along these lines. Over the short term, guild succession is enhanced by changes in fluvial gradient and lake metabolism. Key words: Percidae, succession, reproductive guilds
Applications of a Bioenergetics Model to Yellow Perch (Perca flavescens) and Walleye (Stizostedion vitreum vitreum)
Authors: Kitchell James F. , Stewart Donald J. , Weininger David
Published: April 2011

A simple energy budget equation is developed to yield a bioenergetics model designed to simulate fish growth. Parameters for the model are estimated from the literature for application to yellow perch (Perca flavescens) and walleye (Stizostedion vitreum vitreum). Simulations are presented that demonstrate model output as functions of body size, activity level, ration level, food quality, and environmental temperature. Sensitivity analyses identify the importance of food consumption, activity, and excretion as biological processes represented in the parameters. On the basis of temperature conditions in selected lakes and specified feeding levels, simulations are presented to quantify the importance of year-to-year variation of temperature in determining growth. In heterothermal systems, temperature selection by percids can have a significant effect on growth. For walleye on fixed rations, annual growth can vary from zero to twofold increments due entirely to differences in summer temperatures. Variations in food quality have lesser effects. Key words: Perca, Stizostedion, bioenergetics model, growth, sensitivity, simulations
A Dynamic Model of the Western Lake Erie Walleye (Stizostedion vitreum vitreum) Population
Authors: Shuter B. J. , Koonce J. F.
Published: April 2011

A simple population model of western Lake Erie walleye was constructed using empirical relationships linking growth to population density and recruitment to breeding stock size and the spring water temperature regime. Given a reasonable set of values for annual rates of natural and fishing mortalities, consistent with empirical estimates of total survival for the period from 1947 to 1975, the model generated a pattern of behaviour similar, both qualitatively and quantitatively, to that exhibited by the real population. Two types of stochastic model, based on the initial population model, were used to derive optimal harvest strategies for the population. Optimal strategies were not sensitive to variations in catchability and natural mortality. Yields produced were highly sensitive to variations in both these factors. A refined and extended version of this model may serve as a useful tool in developing realistic management policies for this population. Key words: Percidae, dynamic model, population model, Stizostedion, Lake Erie walleye, growth, density, survival, management implication
Food and Feeding of Spiny Dogfish (Squalus acanthias) in British Columbia Waters
Authors: Jones Barry C. , Geen Glen H.
Published: April 2011

Stomach content data on 14,796 spiny dogfish (Squalus acanthias) from British Columbia waters are presented. The major dietary components based on occurrence were 55% teleosts, 35% crustaceans, and 5% molluscs. The principal food items were herring (22%) and euphausiids (14%). Prey was largely pelagic (80%), with fishes predominating in winter and invertebrates in summer. Fishes became more important in the diet with increasing dogfish size. Dogfish consumed twice as much food in summer as in winter. Annual consumption varied from 5 times biomass for small dogfish to 2.5 times for larger animals. Preliminary analyses suggest that dogfish consume over 5 times the current annual commercial catch of herring, but insignificant quantities of salmon. Key words: dogfish, Squalus, feeding, food, biomass, predation, metabolism, seasonality, survivorship, digestion
Nutrient Distribution in the St. Lawrence Estuary
Authors: Greisman Paul , Ingram Grant
Published: April 2011

The horizontal distribution of nutrients in the St. Lawrence estuary during early July of 1975 is presented. The major sources of nutrients to the estuarine system appeared to be from the St. Lawrence River and the intermediate layer of the Laurentian Channel. By the assumption of simple mixing and conservation, the surface distribution of nutrients has been calculated. Differences between the calculated and observed values may be attributable to consumption, variability of the freshwater source and of the internal tide amplitude. Key words: nutrient distribution, estuarine circulation, mixing
Responses of a Fish Population Model to Young-of-the-Year Mortality
Authors: DeAngelis D. L. , Christensen S. W. , Clark A. G.
Published: April 2011

A multiple-age-class model is used to examine the effects of increases in density-independent young-of-the-year mortality caused by power plant entrainment of larval fish. It is demonstrated analytically that in all realistic cases, an increase in such mortality results in a smaller equilibrium population density of adult fish. The stability of the population with respect to perturbations about its equilibrium point is increased in these cases. However, situations can occur where a slight increase in mortality causes a catastrophic population decline. The model is used to generate autoregression graphs of population numbers that can be compared with field data. Key words: stock–recruitment, young-of-the-year mortality, compensation, Leslie matrix, mathematical model
Oocyte Maturation and Ovulation Induced in Hypophysectomized Winter Flounder (Pseudopleuronectes americanus) by Preparations from Pituitary Glands of American Plaice (Hippoglossoides platessoides)
Authors: Campbell C. M. , Idler D. R.
Published: April 2011

Hypophysectomized winter flounder (Pseudopleuronectes americanus) did not undergo spontaneous oocyte maturation, but the glycoprotein fraction of extracts of American plaice (Hippoglossoides platessoides) pituitaries induced maturation and ovulation. The nonglycoprotein fractions, previously shown to contain a vitellogenic factor, were less efficient than the glycoprotein fractions in the induction of maturation and ovulation. The activity of the nonglycoprotein fraction was further reduced by rechromatography on Con-A Sepharose, suggesting that its action on oocyte maturation and ovulation was due to contamination by the glycoprotein gonadotropin. Key words: hypophysectomy, gonadotropin, oocyte, maturation, ovulation, vitellogenesis, flounder, plaice, Pseudopleuronectes, Hippoglossoides
Leucocrit: A Simple Hematological Technique for Measuring Acute Stress in Salmonid Fish, Including Stressful Concentrations of Pulpmill Effluent
Authors: McLeay Donald J. , Gordon Michael R.
Published: April 2011

The number of leucocytes and thrombocytes in the circulating blood of fishes seems to reflect more accurately than the number of erythrocytes the fish's reaction to acute stress, including that caused by pollution. To facilitate the estimation of leucocytes in fish blood, a new test is being introduced called leucocrit, which is based on the determination of the volume of packed leucocytes–thrombocytes expressed as a percentage of the whole blood. For stocks of juvenile coho salmon (Oncorhynchus kisutch) and rainbow trout (Salmo gairdneri) held in freshwater under a variety of conditions, mean leucocrit values varied from 0.55 to 1.91%. Variations in age, species, food ration, degree of crowding, and prior disturbances offish stocks were associated with these differences. Leucocrit and leucocyte–thrombocyte counts for both species were depressed from stock values after 96-h or shorter (rainbow) exposure to stressful (high-temperature crowded) conditions; values for these measures were positively correlated but uncorrected with hematocrit values. Hematological values for subpopulations of underyearling rainbow trout reared under summer or winter photoperiod conditions were unaffected by photoperiod and responded similarly to acute stress. Leucocrit values for stocks of coho (1.30 ± 0.27%) and rainbow (0.92 ± 0.12%) were depressed due to transfer or acute exposure to bleached kraft pulpmill effluent (BKME). A 24-h exposure to BKME after 2 days' acclimation caused consistent leucocrit depressions, with median effective concentrations of 0.28 of the 96-h LC50 value for coho and 0.16 LC50 for rainbow. Hematocrit showed less sensitive or consistent changes due to stress or effluent exposure than leucocrit. Key words: leucocrit, leucocyte–thrombocyte count, hematocrit, blood, acute stress, BKME, pulpmill effluent, sublethal, salmonid fish, applications
Colonization and Decomposition of Fish Bone Material in Natural and Synthetic Aqueous Solutions
Authors: Smith E. A. H. , Mayfield C. I. , Wong P. T. S.
Published: April 2011

Partial dissolution of the inorganic (apatite) fraction of flesh-free fish (Perca sp.) cheek-bone material, added to P-free (<0.001 μg∙ml−1 total P) nutrient media as bone chips with a particle-size distribution of <250 μm, supported considerable populations of algae and bacteria at slightly alkaline pH levels and relatively low slurry densities (1–1000 μg∙ml−1). Bacteria and algae rapidly colonized the apatitic bone material and produced extracellular material in response to growth on bone surfaces. Acidic filtrates from bacterial cultures, aerobically or anaerobically cultivated in apatite media, readily solubilized bone material as indicated by increases in soluble ortho-PO43− concentrations after short exposure periods. Water extraction of bone apatite crystals showed that fish bones are sparingly soluble in lake water. Microbially mediated dissolution of bone material by acid end-products of bacterial metabolism would therefore greatly increase the rate of bone dissolution in nature. Regeneration of allochthonous-P from fish-bone dissolution may contribute significantly to the P-cycle of many aquatic ecosystems. Key words: biologic apatite, calcium phosphate, fish bone carbonate hydroxyapatite, dahllite
Effects of Pseudobranchectomy on Visual Pigment Density and Ocular PO2 in Atlantic Salmon, Salmo salar
Authors: Ballintijn C. M. , Beatty D. D. , Saunders R. L.
Published: April 2011

Bilateral pseudobranchectomy (B.P.) of Atlantic salmon, Salmo salar, resulted in a progressive loss of visual pigment and a marked decrease in ocular PO2 near the retina. B.P. fish were dark and blind within a few hours of pseudobranchectomy. Unilateral pseudobranchectomy (U.P.) did not have a similar effect on ocular PO2 or visual pigment density in either the ipsilateral or the contralateral eye. U.P. fish did not become dark or blind. An interconnection exists between the right and left ophthalmic arteries permitting an intact pseudobranch to supply blood to the contralateral eye whose pseudobranch has been removed. Although intramuscular injection of acetazolamide caused an initial decrease in amount of visual pigment, body darkening, and blindness, these effects were not permanent. Acetazolamide also caused a marked decrease in ocular PO2 similar to that in B.P. fish. In control fish, dorsal aortic blood and ocular PO2 values were dependent upon an adequate irrigation of the gills. Key words: salmonid, Salmo, pseudobranch, oxygen tension, eye, visual pigment
Mass Stranding of the Long-Finned Pilot Whale, Globicephala melaena, on Sable Island, Nova Scotia
Authors: Geraci J. R. , St. Aubin D. J.
Published: April 2011

On December 23, 1976 a herd of over 130 long-finned pilot whales, Globicephala melaena, became stranded on Sable Island, Nova Scotia (43° 58′N; 59° 48′W). Data on sex, length, and maximum girth, as well as skin and blubber samples for eventual hydrocarbon analysis were collected on January 15 and 16 from up to 116 carcasses. The herd was composed of at least 65 males and 34 females; 17 animals could not be sexed due to seagull damage. The possible reasons for the stranding are discussed. In particular, implications in the news media that the stranding was precipitated by the December 15 breakup of the oil tanker Argo Merchant off the Massachusetts coast are discounted. Key words: long-finned pilot whale; mass stranding; herd composition; Canadian Atlantic
Effect of Freeze-Up on Major Ion and Nutrient Content of a Prairie Winterkill Lake
Authors: Barica J.
Published: April 2011

The reduction of lake volume due to ice formation in a shallow, moderately saline eutrophic prairie lake lacking a permanent surface inflow or outflow accounts for observed increases in specific conductance and concentration of predominant major ions (Mg, Ca, Na, and SO4). Dissolved inorganic carbon, total ammonia nitrogen, and soluble reactive phosphorus concentrations follow a different pattern; their increase under the ice cover is proportional to the decrease in dissolved oxygen and chlorophyll a content. Key words: winter fish kill, freeze-up, major ions, nutrients, prairie lakes, oxygen depletion, eutrophication
Marine Recreational Fisheries.
Authors: Withler F. C.
Published: April 2011

not available
Aquatic Applications of Ozone.
Authors: Gillespie D. C.
Published: April 2011

not available
Retinas of Fishes. An Atlas.
Authors: Stell W. K.
Published: April 2011

not available
Coastal Zone: Framework for Management in Atlantic Canada.
Authors: McAllister C. D.
Published: April 2011

not available
Investigation of the Impact of Mercury on Enclosed Water Columns Using a Zooplankton Simulation Model
Authors: Sonntag Nicholas C. , Greve Wulf
Published: April 2011

A computer simulation model of a phytoplankton–zooplankton–salmon system is used to investigate possible causes of different Pseudocalanus minutus s.l. population dynamics in three enclosed water columns. Mercury at 1 and 5 μg/ℓ was added to two enclosures, with the third serving as a control. Represented in the model are diatoms, flagellates, P. minutus, and fingerling chum salmon (Oncorhynchus keta). Population dynamics are represented in terms of age structure, with age-dependent feeding and survival. Real world data are used to represent the phytoplankton densities. The model results support a hypothesis that the observed Pseudocalanus populations after day 25 could have been a direct consequence of different flagellate populations in the enclosures rather than lethal effects of mercury on molting and reproduction success of the copepod. Key words: modeling, simulation, controlled ecosystems, mercury, zooplankton dynamics
Tests for Association of Transferrin and Lactate Dehydrogenase Phenotypes with Weight Gain in Rainbow Trout (Salmo gairdneri)
Authors: Reinitz Gary L.
Published: April 2011

Transferrin (Tf) phenotype was associated with weight gain in 147- and 230-day-old rainbow trout, but no association was found between lactate dehydrogenase (LDH) phenotype and weight gain. A total of 2038 progeny were examined from two different environments. Progeny lots were reared at densities below those known to affect mean fish weights. Differential survival among progeny with respect to their Tf of LDH phenotype was not detected. Key words: biochemical genetic markers, economic performance, transferrin, lactate dehydrogenase, weight gain
Simulation Concepts for Fishery Systems
Authors: Gales Lawrence E. , Buss James A. , Bledsoe L. J.
Published: April 2011

Computer models for analysis of fishery systems may involve complex applications of mathematics and computer science. While the mathematical aspects of these models have been thoroughly studied, less attention has been paid to methodologies for their computer implementation. As a result, some models excessively simplify fishery systems to avoid difficulties in implementation. This study presents an advanced computer technique (linked lists) which permits the inclusion of complex time simulations and data structures in fishery models with little additional effort. Examples of application to complex information arrays and an age-structured population model are included. Key words: computer, simulation, model, fishery. FORTRAN, ecosystem
Grazing of Marine Copepod Developmental Stages on Naturally Occurring Particles
Authors: Poulet S. A.
Published: April 2011

Grazing experiments were performed with copepodids (stages CI–IV) of Pseudocalanus minutus feeding on naturally occurring particulate matter. Variations in the feeding rate of copepodids were associated with seasonal changes in the standing stock of particulate matter. Copepodids adapted to seasonal variations within the particle spectrum. Particle sizes < 22 μm contributed most of the standing stock of particles during the period studied. Maximum consumption was recorded when copepodids fed on small-size particles. The importance of fine particles is illustrated in comparative feeding experiments performed with adults and copepodids fed simultaneously on the same particles. The differences between the mean consumption of copepodids and adults are highly significant in the particle size ranges below 22 μm. The fact that copepodids obtain more food than adults on particles < 10 μm is probably related to the smaller mesh size and to the higher frequency of vibration of their mouth appendages. Although all copepod stages are opportunistic feeders, such a mechanism allows copepodids to reduce feeding competition with adults and allows them to fulfil their higher requirements for energy from food particles that have a high productive potential and a high nutritive value. This provides the evidence that feeding niches are partially separated between young and adult copepods. Key words: calanoid copepods, copepodids, Pseudocalanus minutus, grazing, competition, naturally occurring particles
Migrations and Activity Levels of Overwintering Atlantic Herring (Clupea harengus harengus) along Southwest Newfoundland
Authors: Winters G. H.
Published: April 2011

Recoveries of tagged Atlantic herring (Clupea harengus harengus) released with abdominally inserted magnetic tags indicated a rapid and random dispersion of tagged fish within the total population of herring along southwest Newfoundland. Recoveries further indicated a general westward movement of herring along southwestern Newfoundland from January to March, also reflected in the spatial distribution of commercial catches during this period. Metabolic rates of these overwintering herring, estimated from changes in body energy from December to March, were more than double the standard level, suggesting a high degree of activity, possibly due to avoidance behavior in relation to predatory actions by cod overwintering in the same area. Key words: tagging, movements, predation, metabolic levels
Effects of Phosphorus from Apatite on Development of Freshwater Communities
Authors: Smith E. A. , Mayfield C. I. , Wong P. T. S.
Published: April 2011

Phosphorus-free nutrients were added to three epilimnetic (pH 7.8) 40-ℓ tanks. Apatite crystals (30–100 μm) were added at loading rates of 30, 2, and 0 mg∙day−1. After a 60-day incubation at 20 °C, levels of particulate organic carbon, particulate nitrogen, and particulate organic phosphorus in Tank 1 increased from 0.42, 0.090, and 0.015 to 6.10, 0.820, and 0.430 μg∙ml−1, respectively. This increase was due to the proliferation of algae, bacteria, and zooplankton and did not occur in the tank with only P-free nutrients. Algae and bacteria grew extensively on the surfaces of apatite crystals causing crystals to aggregate. Zooplankton increases followed those in algae and bacteria, and grazing was restricted to the areas around the apatite crystals. Results suggest that the contribution of soluble ortho-PO43− from apatite to the P-cycle of aquatic environments would be more important under oligotrophic conditions than in areas receiving high loadings of anthropogenic-PO43−, particularly where high erosion increases apatite loadings. Key words: apatite, calcium phosphate, hydroxyapatite, fluorapatite, algae, biogeochemistry, freshwater communities
A Simple Device for Retrieving Instruments or Traps Set Under Ice
Authors: Busdosh M. , Manning A. E.
Published: April 2011

Recovery of instruments or traps suspended under ice is often difficult because refreezing at the circumference of the hole decreases the hole diameter to less than trap diameter, and freezes around the attached line. Line freezing can be reduced by suspending the instrument from the center of the hole. A device consisting of two lengths of wood hinged together, with recurved nails at the lower end can then be used to catch and recover the instrument line through an adjacent hole. These procedures reduce retrieval time by two thirds, and eliminate the damage to instruments or trapped animals that often occurs during recovery. The device can be easily made or repaired on site. Key words: under-ice sampling, under-ice trapping, instrument recovery, arctic
Evidence for the Assumption of Independence between Gastric Emptying Rate and Swimming Activity Using Atlantic Cod, Gadus morhua
Authors: Tyler A. V.
Published: April 2011

Juvenile Atlantic cod, Gadus morhua, were forced to swim at speeds of 0.07, 0.6, and 1.2 body lengths/s after eating measured quantities of food. Higher speeds could not be maintained for more than 2 days. Only the highest speed caused a decrease in gastric emptying rate, but the decrease was not of sufficient magnitude to interfere with ration estimates based on digestion rate data. Key words: feeding, swimming speed, digestion rate
The Yeast Phaffia rhodozyma as a Dietary Pigment Source for Salmonids and Crustaceans
Authors: Johnson Eric A. , Conklin Douglas E. , Lewis Michael J.
Published: April 2011

The red yeast Phaffia rhodozyma contains astaxanthin as its principal carotenoid pigment. Incorporation of this yeast into the diet (15% wt/wt) of rainbow trout induced pigmentation within 43 days. However, lobsters fed the same diet did not readily accumulate the carotenoids of the yeast, though they became pigmented on a diet of live brine shrimp. The primary pigment isolated from the bodies of trout and lobsters fed the red yeast was astaxanthin. We conclude that P. rhodozyma is an excellent source of astaxanthin for cultivated salmonids. Key words: astaxanthin, carotenoid, diet, lobster, Phaffia rhodozyma, salmonids, yeast
Nomenclature Oligochaetologica: A Catalogue of Names, Descriptions and Type Specimens of the Oligochaeta.
Authors: Pickavance J. R.
Published: April 2011

not available
Herbicides: Chemistry, Degradation and Mode of Action.
Authors: Webster G. R. Barrie
Published: April 2011

not available
Economic Impacts of Extended Fisheries Jurisdiction.
Authors: Cauvin Dennis M.
Published: April 2011

not available
Relation of Water Temperature to Infections of Coho Salmon (Oncorhynchus kisutch), Chinook Salmon (O. tshawytscha), and Steelhead Trout (Salmo gairdneri) with Aeromonas salmonicida and A. hydrophila
Authors: Groberg Jr. W. J. , McCoy R. H. , Pilcher K. S. , Fryer J. L.
Published: April 2011

Juvenile steelhead trout (Salmo gairdneri), coho salmon (Oncorhynchus kisutch), and spring chinook salmon (O. tshawytscha) were infected by intraperitoneal or intramuscular injection with Aeromonas salmonicida or A. hydrophila at seven temperatures from 3.9 to 20.5 °C. At 3.9 and 6.7 °C, mortality in fish infected with A. salmonicida varied from 2 to 26% among the three salmonid species. At 20.5 °C 93–100% of these animals died within 2 or 3 days; at 6.7 °C or lower the fish survived for 12–23 days. Growth of A. salmonicida in vitro was influenced by temperature in a manner very similar to its influence on the in vivo infection. Comparable experiments with A. hydrophila gave results much like those with A. salmonicida, though some differences were noted. At a temperature of 20.5 °C percent mortality ranged from 64 to 100%. At 9.4 °C or below no deaths attributed to A. hydrophila occurred. Fatally infected fish died more rapidly at the higher temperatures. Key words: Aeromonas salmonicida, A. hydrophila, water temperature, furunculosis, motile aeromonas septicemia, coho salmon, chinook salmon, steelhead trout
Relation of Water Temperature to Bacterial Kidney Disease in Coho Salmon (Oncorhynchus kisutch), Sockeye Salmon (O. nerka), and Steelhead Trout (Salmo gairdneri)
Authors: Sanders J. E. , Pilcher K. S. , Fryer J. L.
Published: April 2011

Juvenile coho salmon (Oncorhynchus kisutch), sockeye salmon (O. nerka), and steelhead trout (Salmo gairdneri) were infected by intraperitoneal injection of a suspension of the causative organism of bacterial kidney disease at seven experimental temperatures from 3.9 to 20.5 °C. In coho salmon and steelhead trout percent mortality was maximal (78–100%) in the range of 6.7–12.2 °C. As the temperature increased above 12.2 °C mortality declined progressively; at 20.5 °C it was only 8–14%. The two highest temperatures had some suppressing effect on the disease, which was greatest at 20.5 °C. In sockeye salmon this was not apparent, as percent mortality was essentially 100% at all temperatures from 6.7 to 20.5 °C; this species appeared to be highly susceptible to the disease agent. Temperature also influenced the mean number of days between infection and death. This interval was shortest in all three species of salmonids at the higher temperatures, varying from 21 to 34 days at 15.0–20.5 °C. It increased progressively as temperature decreased below this range; at 6.7 °C it varied from 60 to 71 days among the three species. Key words: bacterial kidney disease, temperature, salmonids, Corynebacterium, coho salmon, sockeye salmon, steelhead trout
Toxicity of Cadmium to Goldfish, Carassius auratus, in Hard and Soft Water
Authors: McCarty L. S. , Henry J. A. C. , Houston A. H.
Published: April 2011

Variations in cadmium form and concentration and in selected water quality parameters (pH, dissolved oxygen, total hardness, total alkalinity, conductivity) were monitored during static bioassays conducted with relatively soft (~ 20 mg/L as CaCO3) and hard (~ 140 mg/L as CaCO3) waters. Cadmium concentrations were reasonably stable in soft water, and with the exception of total hardness, water quality was not greatly altered during assay. Cumulative mortality curves were of a simple sigmoidal type and readily analyzed by conventional procedures. LC50 values of 2.76, 2.13, and 1.78 mg Cd/L were estimated on the basis of 48-, 96-, and 240-h periods of observation. During hard-water trials there were transient increases in the amount of particulate cadmium present and sharp decreases in total cadmium levels. Several parameters (pH, total alkalinity, conductivity) exhibited transient and/or sustained variations of a cadmium concentration-dependent type. Mortality curves were typically biphasic. The extent of first-phase mortality was significantly correlated with the magnitude of the initial pH decline and the amount of cadmium present in centrifugable form. Conventional procedures did not result in rectification of 240-h cumulative mortality curves, and the 240-h LC50 value (40.2 mg Cd/L) is considered to be inherently less precise than those obtained on the basis of 48- and 96-h periods of observation (46.9, 46.8 mg Cd/L). Key words: goldfish, Carassius auratus, cadmium toxicity, hard water, soft water, mortality