bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Spawning Runs of Sea Lamprey (Petromyzon marinus) in Selected Streams of Lake Superior after Chemical Control
Authors: Moore H. H. , Schleen L. P.
Published: April 2008

During lampricide treatment of a stream, sea lamprey, Petromyzon marinus, that will constitute the spawning run the following spring inhabit the Great Lakes and are not affected by the treatment. However, the number of adults captured at electrical barriers declined as much as 99% in some streams 1 year after chemical treatment. Large declines of adults were noted in streams which were treated late in the year. Streams in which significant populations of larval lampreys survived the chemical treatment, or contained lentic populations, continued to attract adults. Adult sea lampreys could be attracted to sea lamprey ammocoetes in streams or in offshore areas and hence use this as one of a number of clues to determine rivers suitable for spawning.Key words: sea lamprey, olfaction, orientation/homing, spawning migration, habitat alteration (chemical), Petromyzon marinus, lampricides
Adult Biology of the River Lamprey (Lampetra ayresi) and the Pacific Lamprey (Lampetra tridentate) from the Pacific Coast of Canada
Authors: Beamish Richard J.
Published: April 2008

River lamprey (Lampetra ayresi) metamorphose in late July with downstream migration occurring in the following year from May to July. Once adults enter salt water they begin to feed immediately by consuming chunks of flesh primarily from herring and young salmon. From June until September they increase in size by an estimated 11–14 cm and 12–18 g. In 1975, 667 000 lamprey were estimated to be in the Strait of Georgia resulting in the deaths of 60 000-000 juvenile fish. Between September and late winter river lamprey return to freshwater. Spawning occurs in the spring, from April to June and adults die after spawning. The length of adult life from the onset of metamorphosis until death following spawning is 2 yr. Pacific lamprey (Lampetra tridentata) begin metamorphosis in July and the known period of entry into salt water is from December until June. Feeding can commence in freshwater or salt water by mid-October. Pacific lamprey move into water deeper than 20–70 m and are present in all major fishing grounds off Canada's west coast. A relatively high incidence of lamprey attacks has been observed on sockeye and pink salmon that are aggregating in preparation to return to freshwater. The smallest mature or maturing pacific lamprey found in this study measured 16 cm and the largest measured 72 cm. Adults may spend [Formula: see text] in salt water before returning to freshwater from April to June and completing their upstream migrations by late September. Stocks that return in the spring exhibit exceptional migratory instincts often migrating considerable distances in freshwater to the uppermost regions of tributary streams before they spawn from April to July in the following year. After entry into freshwater and prior to spawning, adults shrink in length by approximately 20%. The average life span from the onset of metamorphosis until death following spawning probably is 5 yr. A nonanadromous form that appears to be a new species exists in lakes and attacks a large percentage of resident salmonids.Key words: Pacific lamprey, river lamprey, life history, fish parasites, Pacific fishes
Review of the Ecology of Lampreys in Northern Europe
Authors: Maitland P. S.
Published: April 2008

The general distributions of Petromyzon marinus, and Lampetra fluviatilis and L. planeri in Europe are similar and include much of the west and north, whereas Lethenteron japonicum occurs only in the north. The larvae of all four species occupy areas of shaded silt (optimum particle size: 180–380 μm) in parts of streams where current velocities are about 0.4 m/s. The gradients of streams in which they occur range from 1.9 to 5.7 m/km. Though differing in small details, the life cycles have much in common and spawning occurs usually in the spring or early summer. Both males and females spawn only once and die after reproduction. After hatching, the small larvae drift downstream to suitable silt beds. Larval life is variable and may last from 3 to 5 yr or even more. Larval metamorphosis and downstream migration occur during spring and summer and takes place mainly at night. The larvae of all species feed on fine particulate matter — mainly microorganisms and detritus. Adult L. planeri do not feed, but those of the three other species grow and mature in the sea where they are parasitic on a variety of marine and anadromous teleosts. There are considerable differences among the fecundities of the four species — related very much to the size of the adult females. Relatively few data are available on the population dynamics of any of the species.Key words: lampreys, ecology, Europe
Lampreys and Lamprey Fisheries in Finland
Authors: Tuunainen P. , Ikonen E. , Auvinen H.
Published: April 2008

There are three lamprey species in Finland. European river lamprey (Lampetra fluviatilis) is common along the coast of Finland and 28 rivers are known to support spawning populations while landlocked river lamprey populations exist in three watercourses. European brook lamprey (Lampetra planed) is common in freshwater all over the country, and sea lamprey (Petromyzon marinus) has been reported off the Finnish coast only 19 times since 1854. Food of the river lamprey and landlocked river lamprey includes valuable fish species such as herring, sprat, and vendace, but no effects on the fish stocks have been reported. River lamprey catch in Finnish coastal rivers make up about 2–2.5 million individuals (100 t) and lampreys are used only for human consumption. The fishing season begins in August and ends in February. Environmental changes in rivers (dams, pollution, etc.) have caused great damage to river lamprey populations. Successful attempts have been made to promote spawning by transporting lampreys over the dams. Landlocked river lamprey, brook lamprey, and sea lamprey are of no economic significance in Finland.Key words: sea lamprey, river lamprey, brook lamprey, distribution, Finland, life history, fisheries, management
Classification of Sea Lamprey (Petromyzon marinus) Attack Marks on Great Lakes Lake Trout (Salvelinus namaycush)
Authors: King Jr. Everett Louis
Published: April 2008

Criteria for the classification of marks inflicted by sea lamprey (Petromyzon marinus) into nine categories were developed from laboratory studies in an attempt to refine the classification system used in field assessment work. These criteria were based on characteristics of the attachment site that could be identified under field conditions by unaided visual means and by touching the attachment site. Healing of these marks was somewhat variable and was influenced by the size of lamprey, duration of attachment, severity of the wound at lamprey detachment, season and water temperature, and by other less obvious factors. Even under laboratory conditions staging of some wounds was difficult, especially at low water temperatures. If these criteria are to be used effectively and with precision in the field, close examination of individual fish may be required. If the feeding and density of specific year-classes of sea lampreys are to be accurately assessed on an annual basis, close attention to the wound size (as it reflects the size of the lamprey's oral disc) and character of wounds on fish will be required as well as consideration of the season of the year in which they are observed.Key words: sea lamprey, attack marks, lake trout, Great Lakes
Predatory-Phase Sea Lampreys (Petromyzon marinus) in the Great Lakes
Authors: Johnson B. G. H. , Anderson William C.
Published: April 2008

Incidentally caught predatory-phase sea lampreys were obtained from the commercial fisheries of the Laurentian Great Lakes, together with related catch data, in return for a reward offered to fishermen. Catches of sea lampreys per unit of fishing effort in Lake Superior generally paralleled other indices of sea lamprey abundance. Recently metamorphosed sea lampreys tended to appear early in the season in deepwater fisheries, typically those directed toward cisco (Coregonus spp.), whereas older specimens were taken more often in gear set at shallower depths during summer and fall. The proportion of male sea lampreys in the collections decreased annually between spring and fall, due apparently to a shoreward movement of the males. Large lake trout (Salvelinus namaycush) appeared to be the preferred prey of the sea lamprey. From studies of the stomach contents, sea lamprey feeding activity appeared to reach a peak in late summer or early fall, thereafter declining until the cessation of feeding in early spring. Growth rate reached a maximum in late summer or early fall. Greatest length was attained between January and March, after which a decrease in length was observed. Predatory-phase sea lampreys remained concentrated near the mouths of their parent streams if sufficient numbers of prey were present. Their distribution in the Great Lakes was related to the location of prey.Key words: sea lamprey, predation, Great Lakes fishery
Parasitic Phase of the Sea Lamprey (Petromyzon marinus) in Lake Ontario
Authors: Christie W. J. , Kolenosky D. P.
Published: April 2008

Sea lamprey produced in other areas of Lake Ontario appeared to be responsible for significant levels of predation on target species of the eastern outlet basin. The life history of the lamprey is simple with only one parasitic generation present in the lake during the feeding period. Wound frequencies on gillnetted whitefish were influenced by season, fish size, gillnet set duration, and a large random error component which suggested a contagious distribution. Scar frequencies were influenced by fish age and indicated improved survival of whitefish when fish weight exceeded lamprey weight by 43 times. Lamprey impact on the whitefish stocks would probably have been more important at lower fishing intensities. The lamprey may have been prey limited, and size and species preference were probably such that lake trout and burbot were not buffered against sea lamprey by white suckers or whitefish. The analysis favored the view that lamprey were innocuous in 19th century Lake Ontario by reason of prey size and density, but climatic and other environmental effects could also have been important.Key words: sea lamprey, lake whitefish, Lake Ontario
Changes in Mortality of Lake Trout (Salvelinus namaycush) in Relation to Increased Sea Lamprey (Petromyzon marinus) Abundance in Green Bay, 1974–78
Authors: Moore J. D. , Lychwick T. J.
Published: April 2008

Increased sea lamprey (Petromyzon marinus) abundance in Green Bay during 1977 is documented utilizing sea lamprey counts and lake trout (Salvelinus namaycush) wounding as methods of measurement. Since lake trout rehabilitation began in 1965, sea lamprey predation has been consistently higher in Green Bay and Northern Lake Michigan than other areas of the lake. It appears that increased sea lamprey predation in Green Bay, above the former high levels, resulted in decreased abundance and increased mortality of lake trout. The increase in lampreys is related to the colonization of the Peshtigo River, Marinette County, Wisconsin.Key words: Green Bay, sea lamprey increases, Peshtigo River, lake trout, increased mortality
On Evaluating Measures to Rehabilitate Lake Trout (Salvelinus namaycush) of Lake Superior
Authors: Lawrie A. H. , MacCallum W.
Published: April 2008

The Lake Superior lake trout (Salvelinus namaycush) population is being rebuilt following its collapse in the early 1950s. Estimates are presented of the contributions to this recovery provided directly by the artificial recruitment of hatchery fish, a demonstrable amelioration in mortality rates and a resurgence, lately, of natural recruitment. Of the increased lake trout abundance, 55% on the average was owing to trebling the planting density, 40% to improved survival, and 5% to increasing recruitment of native lake trout. The precise contribution of the sea lamprey (Petromyzon marinus) control program could not be defined for lack of sufficient early data.Key words: lake trout, sea lamprey, rehabilitation, natural recruitment, hatchery stocking
Prospects for Integrated Pest Management of the Sea Lamprey (Petromyzon marinus)
Authors: Sawyer Alan J.
Published: April 2008

The concepts of integrated pest management (IPM) may be applied to the problem of controlling the sea lamprey, Petromyzon marinus, in the Great Lakes. IPM originated as the integration of biological and chemical methods of insect control. It has since evolved into an interdisciplinary approach to ecologically, economically, and socially compatible pest control based on applied systems ecology, real-time monitoring systems and optimal control theory. The component processes of sea lamprey population dynamics are discussed with reference to key ecological variables and possible control points. To implement an integrated approach to sea lamprey pest management successfully, work is needed on basic lamprey biology and ecology, predictive models, alternative control tactics, and the economics of lamprey-induced injury to fish.Key words: Petromyzon marinus, sea lamprey; integrated pest management, systems analysis, modeling
Potential Problems in the Registration of Sea Lamprey (Petromyzon marinus) Control Agents
Authors: Meyer Fred P. , Schnick Rosalie A.
Published: April 2008

It is highly probable that increased data will be required in future applications for registration of control agents to support claims of efficacy, environmental safety, and human safety for control of the sea lamprey, Petromyzon marinus. Alternative techniques, such as biological or physical control methods, are also encompassed by regulatory control. Pheromones, hormones, attractants, and repellents are subject to the same stringent regulations applied to purely chemical methods. Guidelines for registering live biological control agents are under review and revision, but currently such agents are regulated under the same requirements as chemicals. The irreversible act of releasing living control organisms, such as predators, parasites, or pathogens, and their possible detrimental effects on nontarget species, will require significant proof that they will not harm the ecosystem. Biologics, such as serums, vaccines, or antigens, also require registration, but the process is less complicated and requires less time for completion. Regulation of physical control devices occurs only if the method or device is offered for sale with claims as to its efficacy.Key words: sea lamprey, sea lamprey control, Petromyzon marinus, lampricides, chemical registration, chemical control, biological control, physical control
Development of Sea Lamprey (Petromyzon marinus) Larvicides
Authors: Howell John H. , Lech John J. , Allen John L.
Published: April 2008

Larvicides are used to control sea lamprey (Petromyzon marinus) in the Great Lakes. These larvicides are useful because they are more toxic to sea lamprey than fish species found in the same habitat. The lampricides come from two classes of chemical compounds: (1) halonitrophenols, and (2) halonitrosalicylanilides. Selectivity of the larvicides appears to be based on the differences in the ability of sea lamprey larvae and fishes to detoxify and/or excrete the chemicals. Glucuronide conjugation is an important mechanism for detoxification of these larvicides by fish, and selectivity of larvicides may be due to differences in glucuronyl transferase activity between lamprey and fishes. If more detailed information were available on uptake, metabolism, excretion, and the biochemistry and physiology of lamprey as compared to fishes, it might be possible to design chemicals that would be more selective than those now in use.Key words: sea lamprey, larvicides, selective toxicity, uptake, metabolism, excretion, halonitrophenols
Sterility Method of Pest Control and Its Potential Role in an Integrated Sea Lamprey (Petromyzon marinus) Control Program
Authors: Hanson Lee H. , Manion Patrick J.
Published: April 2008

The sterility method of pest control could be an effective tool in the sea lamprey (Petromyzon marinus) control program in the Great Lakes. Some of the requirements for its successful application have been met. A field study demonstrated that the release of male sea lampreys, sterilized by the injection of 100 mg/kg of P,P-bis(1-aziridinyl)-N-methylphosphinothioic amide (bisazir), will reduce the number of viable larvae produced. The actual reduction in reproductive success that occurred was directly related to the ratio of sterile to normal males in the population. The technique can be used in many ways in an integrated control program and has considerable potential for the more effective control of the sea lamprey. Eradication is a distinct possibility.Key words: sea lamprey, Petromyzon marinus; pest control, fish control, sterile-male technique, sterilization, chemosterilants, bisazir, Great Lakes
Responses of Lake Trout (Salvelinus namaycush) to Harvesting, Stocking, and Lamprey Reduction
Authors: Walters Carl J. , Steer Greg , Spangler George
Published: April 2008

Sustained yields, declines, and recovery of lake trout (Salvelinus namaycush) can be explained by a simple model that hypothesizes normal population regulation through density dependent body growth, coupled with depensatory lamprey mortality. The model indicates that either lamprey or fishing alone could have caused the Lake Superior decline, though they apparently operated in concert. The presence of depensatory lamprey mortality leads to a "cliff edge" in the system's dynamics, such that catastrophic changes may be repeated in the future. It is not unlikely that Lake Superior is on the verge of a second collapse. Options for dealing with potential disasters include conservative harvesting policies, development of more sensitive monitoring indicators, and modified stocking policies that may speed the coevolution of a viable lamprey/trout association.Key words: lake trout, sea lamprey, simulation, Great Lakes, policy analysis
Estimates of Lamprey-Induced Mortality in Whitefish, Coregonus clupeaformis
Authors: Spangler George R. , Robson Douglas S. , Regier Henry A.
Published: April 2008

The seasonal rate of lamprey attack upon lake whitefish in Lake Huron is estimable as the proportion of recently wounded fish in the catch. The nonfatal lamprey attack rate is estimable from the accumulation of healed scars observed on a cohort of marked (tagged) fish sampled throughout the fishing season. The difference between these estimates is an estimate of the fatal lamprey attack coefficient. In northern Lake Huron, lamprey attacks on whitefish are most frequent during August to November. The fatal lamprey attack rate is greatest during late summer when a large proportion of attacks results in the death of the host. Approximately 75% of the lamprey attacks on whitefish are fatal during mid-June to mid-November.Key words: Lake Huron, Petromyzon marinus, lake whitefish, lamprey attack rate
Estimate of Lamprey-Induced Mortality in a Lake Trout (Salvelinus namaycush) Population
Authors: Youngs William D.
Published: April 2008

A competing risk model was applied to mortality occurring in a lake trout population subjected to fishing and lamprey parasitism. Two indices are proposed as a measure of lamprey-induced mortality in the lake trout (Salvelinus namaycush) population: the average number of wounds per fish (W/F) and the average number of scars per fish (S/F) accumulated by a cohort over a period of 1 yr. These indices were used as a measure of the force of lamprey-induced mortality. Fishing mortality was estimated from angler returns of tags on lake trout. Tag returns were also used in a maximum likelihood method to estimate survival of lake trout. Fishing and lamprey-induced mortality components of the model were analyzed by linear regression methods with the force of total mortality (i) as the independent variable. The component for lamprey-induced mortality (either W/F or S/F) did not contribute significantly to the reduction in variation of the force of total mortality, but the component for fishing mortality was significant. A negative coefficient for some analyses associated with the component for lamprey-induced mortality suggested a possible conditioning influence by other factors. Growth of lake trout was examined as a possible conditioning factor but analyses suggested that growth did not influence survival. Lamprey did not apparently cause any appreciable mortality in the lake trout population, age 4 and older, in Cayuga Lake during the years studied. It was not possible to consider younger age-groups of lake trout. Keywords: lake trout, lamprey, mortality
Bioenergetics Model and Foraging Hypothesis for Sea Lamprey (Petromyzon marinus)
Authors: Kitchell James F. , Breck James E.
Published: April 2008

A bioenergetics model for growth of lamprey during the parasitic phase was used to estimate food consumption by lampreys and the impact of lamprey feeding on host fishes. Estimates are evaluated by application to several Great Lakes case histories. Temperature and size-dependence of feeding and respiration were sufficient to account for growth dynamics. The model demonstrates that distribution of host fishes, by determining the thermal history of the lamprey, has important effects on lamprey life history and host mortality. Modeled lamprey growth and feeding rates, relative to size of the host, predict a strongly seasonal host mortality rate peaking in autumn. The predicted mortality pattern corresponds with that of independently derived data. Principles of optimal foraging theory applied to lamprey yield a hypothesis that predicts highest wounding and scarring frequencies at intermediate lamprey: host abundance ratios. A second component of the hypothesis predicts seasonal changes in these frequencies as lamprey size increases. Growth rates of lamprey and their host species plus wounding and scarring frequencies are more sensitive indicators of changing abundance ratios and lamprey effects than population changes resulting from predation by lamprey.Key words: sea lamprey, Petromyzon marinus; model, bioenergetics, growth, consumption, fish mortality, Great Lakes
Benefits and Costs of Sea Lamprey (Petromyzon marinus) Control in the Great Lakes: Some Preliminary Results
Authors: Talhelm Daniel R. , Bishop Richard C.
Published: April 2008

While economic studies of the Great Lakes fisheries are still in their infancy, evidence is accumulating which suggests that efforts to rehabilitate the salmonid fisheries of the Great Lakes, including sea lamprey control, are paying rich dividends; benefits may exceed costs by half a billion dollars each year. Sportfishing values are much greater than commercial fishing values, so anglers benefit most from sea lamprey control. Expanding rehabilitation efforts in ways that will enhance angler success may also be economically sound. PCB levels in Great Lakes salmonids may be lowering the value of angling; 30% of anglers surveyed report eating less of their catch as a result of warnings. However, 93% oppose discontinuing stocking because of the PCB problem. The effects of possible energy shortages are difficult to predict, and may not necessarily reduce Great Lakes fisheries values.Key words: sea lamprey, benefit–cost analysis, fishery economics, recreation economics
Interactions between Sea Lamprey (Petromyzon marinus) and their Forage Base. A Report from the SUS Stock Effects Task Force
Authors: Lawrie A. H.
Published: April 2008

A task force of participants convened during the course of the Sea Lamprey International Symposium considered the implications, for management of Great Lakes fisheries, of information provided about known interactions between feeding sea lampreys and the stocks of fish on which they prey. A weighted series of recommendations identified the need for more information or for changes in management practice.Key words: sea lamprey, Great Lakes, Finger Lakes, fishery management, stock concept
Assessment of Lamprey and Fish Stocks in the Great Lakes in Relation to Control of the Sea Lamprey (Petromyzon marinus): Report from the SLIS Assessment Measurements Task Force
Authors: Maitland P. S.
Published: April 2008

Available and potential methodology for assessing lamprey and prey fish populations is related to existing and future requirements of the sea lamprey control program of the Great Lakes Fishery Commission (GLFC). For lamprey, we recommend that the classification of Great Lakes tributaries according to their potential for larval production and the quality of lamprey attack data should be improved and standardized; standardized collections of spawning run adults should be continued; research should be encouraged on attractants and repellents, a male sterilization program, and the biology of parasitic phase animals. For fish, we recommend that more emphasis be given to the precision and standardization of estimates to allow better comparison between places and years, and the assessment of fish stocks other than major prey species; the GLFC support an evaluation program of an important prey species; and that other assessment methods (e.g. acoustic; counts of entrained fish) be explored. Because lamprey control is a long-term process that may span periods of environmental change, monitoring of physical, chemical, and biotic factors should be encouraged. Research on the impact of lampricides on nontarget organisms should be expanded. We also discuss and offer suggestions on the future of sea lamprey control.Key words: stock assessment, fishery surveys, methodology, populations control, proposed research
An Acoustic Study of Shrimp (Pandalus montagui) Distribution near Resolution Island (Eastern Hudson Strait)
Authors: Crawford R. E. , Hudon C. , Parsons D. G.
Published: April 2008

Echo integration, a multistage plankton sampler (BIONESS), and a bottom trawl were used to examine the horizontal and vertical distribution of shrimp (Pandalus montagui) near Resolution Island in eastern Hudson Strait. Shrimp were concentrated in two locations within the study area and they maintained this pattern of horizontal distribution for at least 7 d. Acoustic observations revealed a scale of horizontal patchiness that was obscured by the "homogenization effect" of sampling by bottom trawl and plankton net. The shrimp underwent a nocturnal vertical migration with other zooplankton to > 200 m from the bottom and a subsequent downward migration during early daylight hours. This diel migration resulted in reduced availability of shrimp to the bottom trawl at night. Timing of the migrations varied, possibly as a result of interaction with oceanographic processes.
Progression of Coronary Arterial Lesions in Atlantic Salmon (Salmo salar) as a Function of Growth Rate
Authors: Saunders R. L. , Farrell A. P. , Knox D. E.
Published: April 2008

Development of coronary arteriosclerosis has been studied in all life stages of both wild and cultured Atlantic salmon (Salmo salar). Lesions accumulate slowly during juvenile growth in freshwater in both wild and cultured populations and increase sharply during early marine life; much of the progression occurs well before the onset of sexual maturity. Fewer than 5% of sexually mature Atlantic salmon (wild or fast-growing cultivated) were free of coronary lesions. Lesions were distributed over 45–85% of the length of the coronary artery. Lesions were less abundant and less advanced in a cultured strain of salmon that grew more slowly than another cultured, fast-growing strain. We conclude that prevalence and severity of lesions in Atlantic salmon accelerate in parallel with, and possibly in response to, those factors responsible for rapid growth in the sea. We discuss diet, endocrine changes associated with sexual maturation, metabolic aspects of parr–smolt transformation, and physiological stress as factors possibly influencing progression of lesions associated with rapid growth during the marine stage.
Optimal Harvest Rates for Mixed Stocks of Natural and Hatchery Fish
Authors: Kope Robert G.
Published: April 2008

Optimal harvest rates were computed using dynamic programming for mixed-stock fisheries exploiting two stocks of either natural or hatchery origin. Natural stocks were described by a Ricker spawner–recruit relationship and hatchery stocks were described by a rectilinear spawner–recruit relationship. Harvest rates were optimized for both risk-neutral and risk-averse utility functions. For two natural stocks with low productivities, optimal harvest rates generally appeared to favor the stronger stock for a risk-neutral utility function and the weaker stock for a risk-averse utility function. For both utility functions, optimal harvest policy became less sensitive to relative stock strength as the productivity of the stocks increased. When at least one of the stocks was of hatchery origin, optimal harvest policy favored the weaker stock using either utility function.
Evolution of Dissolved and Particulate Matter during the Ice-Covered Period in a Deep, High-Mountain Lake
Authors: Catalan Jordi
Published: April 2008

Changes in inorganic and organic matter beneath the ice in a deep oligotrophic lake are used to establish temporal and spatial scales of physical and biological processes involved in the dynamics of the system during low energy flow. Four phases were distinguished: (1) Ice-forming phase; light still penetrated the relatively thin snowpack, production was high, and a chlorophyll maximum developed close to the ice. (2) Transition towards a dark environment; light was reduced to very low levels by rapid snow accumulation, phytoplankton showed symptoms of shade adaptation, and nutrients and dissolved organic compounds changed markedly (e.g. soluble reactive phosphorus increased). (3) Central phase; for several months, loss processes (respiration, sedimentation) maintained constant rates, three zones of differing variability patterns were distinguished in the water column: an upper zone where biomass was higher and which was affected by exchange of substances with the cover during flooding processes, a middle zone with little change throughout the phase, and a deep layer, identified by catabolic activity, where diffusion of compounds from the sediment took place. (4) Thaw; sequential changes occurred near the surface owing to snowpack melting, chlorophyll reached the lowest winter values of the period in spite of light and nutrients, and nitrogen compounds changed significantly.
Temporal Variance Function for Total Phosphorus Concentration
Authors: France Robert L. , Peters Robert H.
Published: April 2008

General relationships between means and variances can be used to determine requisite sample number for desired levels of precision but have not been developed for phosphorus, one of the best indicators of lake eutrophication. Data from 65 north-temperate lake-years are used to compare such relationships of temporal variance as functions of mean concentration for both total phosphorus (TP) and chlorophyll a (Chl a). We found TP to be less seasonally variable than Chl a, confirming several regional analyses and strengthening the established recommendations that variability in Chl a should dictate sampling program design.
Influence of Stream Flows and Stock Size on Recruitment of Arctic Grayling (Thymallus arcticus) in the Chena River, Alaska
Authors: Clark Robert A.
Published: April 2008

The hypothesis that recruitment of Arctic grayling (Thymallus arcticus) in the Chena River is influenced by stream flows and stock size was tested using population data collected from 1976 through 1990. Recruitment may be influenced by stream flows during the initial weeks of life of Arctic grayling, namely during spawning, emergence, and the larval stage. Using correlation and regression analyses, stream flow during the time-frame was found to be a significant descriptor of variability in recruitment (r = −0.751, P = 0.005). Although stream flows were implicated in recruitment variation, creation of an environment-dependent, stock–recruitment model was not possible because estimates of measurement error were lacking, because of bias due to the relation between residuals and subsequent stock size, and because of the presumed autocorrelation of stock size. An alternative analysis was conducted to investigate the influence of stock size on recruitment when stream flows were thought to minimally affect recruitment. Using an estimate of natural mortality rate and assuming no fishing mortality, the theoretical contribution of recruits to the spawning stock exceeded the maximum observed stock size. I concluded that the maximum observed stock size failed to negatively influence recruitment, and the level of stock size that might influence recruitment is greater than the maximum observed stock size.
Zooplankton in Advective Environments: The Hudson River Community and a Comparative Analysis
Authors: Pace Michael L. , Findlay Stuart E. G. , Lints David
Published: April 2008

The temporal dynamics and spatial distributions of zooplankton in the tidal freshwater portion of the Hudson River were studied over a 3-yr period. We tested the hypothesis that advective transport regulates zooplankton biomass in the Hudson and in lakes, estuaries, and rivers for which we have published values. In the Hudson, zooplankton biomass was negatively correlated with discharge over the entire season (P < 0.0001) as well as during the warmer period of the year (P = 0.007) when biomass was greatest. The spatial distribution of zooplankton over 160-km transects was heterogeneous. Downstream changes in the abundance of a dominant species, Bosmina longirostris, indicate that certain areas of the river support net population growth whereas other areas are population sinks. We infer that zooplankton biomass in the Hudson is a function of the balance between reproduction determined by resources and losses due to advection. Zooplankton biomass differs among lakes, estuaries, and rivers in a manner consistent with the differences in water residence time. Biomass is highest in lakes, lower in saline estuaries and tidal rivers, and lowest in rivers. Advective losses appear to be important in explaining differences between planktonic communities in lentic and lotic environments.
Pharmacokinetics, Bioavailability, Distribution, and Metabolism of Sulfadimethoxine in the Rainbow Trout (Oncorhynchus mykiss)
Authors: Kleinow Kevin M. , Beilfuss Wendy L. , Jarboe Herman H. , Droy Brad F. , Lech John J.
Published: April 2008

Sulfadimethoxine (SDM), a sulfonamide antibacterial drug, was examined in regards to bioavailability, pharmacokinetics, distribution, plasma protein binding, mass balance, and metabolism in the rainbow trout (Oncorhynchus mykiss). Analysis of SDM pharmacokinetics when determined by 35S counting (parent/metabolite combination) and HPLC (parent) provided estimates for t1/2α, t1/2β, Vss, and Clb, of 0.63/0.38 (h), 17.0/15.9 (h), 500.8/421.6 (mL/kg), and 22.7/21.8 mL∙kg−1∙h−1, respectively. Multiple dose administration of [35S]SDM resulted in a terminal t1/2 of 35.2 h. Sodium SDM (42 and 126 mg/kg) and free drug (42 mg/kg) oral bioavailabilities were 63, 50, and 34%, respectively. Plasma protein binding (15.8 ± 5.1%) was nonsaturable and nonspecific. Tissues attained the highest levels of SDM equivalents in the bile followed by the intestine, liver, blood, skin, kidney, spleen, gill, muscle, and fat, respectively. Mass balance studies demonstrated a minor role for branchial ((0.6 ± 0.24%) 25 h) and urinary ((5.46 ± 2.24%) 24 h) routes of elimination over the first 24 h. SDM and N4-acetylated SDM (N4-A-SDM) were the major constituents for branchial and urinary routes, respectively. Metabolite analysis for select tissues demonstrated a predominance of N4-A-SDM in bile, SDM in plasma, and N4-A-SDM in the liver 20 h after dosing.
Relation of grilse to salmon ratio to environmental changes in several wild stocks of Atlantic salmon (Salmo salar) in Iceland
Authors: Gudjonsson S. , Einarsson S. M. , Antonsson Th. , Gudbergsson G.
Published: April 2008

The grilse to salmon ratio of each smolt class of Atlantic salmon (Salmo salar) during the last three decades were examined using data from catch records and from direct counter data in several rivers in western and northern Iceland. The counter data show that the catch data in Icelandic rivers reflects the number of spawners entering the rivers. Both long- and short-term changes in the grilse to salmon ratio were seen. Climatic changes can be responsible for long term changes in sea age composition of Icelandic salmon stocks. Short-term changes in the ratio can be explained by changes in marine conditions that influence the survival of salmon during their second year at sea.
Experimental assessment of the effect of temperature and salinity on elemental composition of otoliths using laser ablation ICPMS
Authors: Fowler Anthony J. , Campana Steven E. , Thorrold Simon R. , Jones Cynthia M.
Published: April 2008

Laser ablation – inductively coupled plasma mass spectrometry (LA-ICPMS) is a new technique that can be used for the multielemental analysis of otoliths at specific loci. This method was used to sample the otoliths of Atlantic croaker (Micropogonias undulatus), reared under different constant regimes of temperature and salinity, to determine whether the elemental composition of otoliths changes ontogenetically. Each otolith was sampled at a number of loci, beginning at the center and then every 500 μm along the longest axis to near the edge; of 23 isotopes measured simultaneously at each locus, 18 were standardized to48Ca and included in analyses. The elemental composition at otolith centers and near their edges differed significantly amongst treatments, with the effect of temperature a stronger influence. Elemental composition also varied across otoliths from within treatments, indicating endogenous effects. Ontogenetic patterns differed amongst treatments, indicating that endogenous control was mediated by the external environment. Otoliths of fish from one tank where the physical conditions were switched, showed greater variation in the multielemental signal than that resulting only from ontogenetic change. All analyses indicated that otolith formation is the product of numerous interactive exogenous and endogenous processes, including water temperature, salinity, and ontogeny.
Predicting the intensity and impact of Dreissena infestation on native unionid bivalves from Dreissena field density
Authors: Ricciardi A. , Rasmussen J. B. , Whoriskey F. G.
Published: April 2008

Introduced dreissenid mussels (Dreissena polymorpha and Dreissena bugensis) foul native unionid bivalves by attaching to their shells in large clusters and may critically impair many North American unionids that are already threatened by habitat degradation. Using literature and new field data, we examined patterns of Dreissena infestation on unionids, and the relationships between Dreissena field density, infestation intensity, and unionid mortality. Linear regression models showed that Dreissena field density strongly predicts (i) the proportion of unionids colonized by dreissenids (r2 = 0.90, p < 0.0001) and (ii) the mean number of dreissenids attached to unionids (r2 = 0.81, p < 0.0001). We fitted a compound Poisson model that accounts for dreissenid clustering and predicts both the proportion of colonized unionids and the mean infestation intensity as effectively as our empirically derived models. The proportion of unionids colonized by Dreissena follows a saturation curve, increasing rapidly with Dreissena densities up to 200/m2, and reaching a plateau at 70–80% colonization. Unionid mortality (reflected by the proportion of dead unionids) is strongly correlated with Dreissena field density (r2 = 0.82, p < 0.002) at densities above 1000/m2. Our models predict that severe unionid mortality (>90%) occurs when Dreissena density and mean infestation intensity reach 6000/m2 and 100 dreissenids/unionid.
Morphology and microhabitat use in stream fish
Authors: Wood Brian M. , Bain Mark B.
Published: April 2008

Microhabitat use and body morphology were compared among 15 warmwater stream fishes from the Alabama River (Alabama, U.S.A.) watershed. Morphological variation among separate populations of a species was detected in 14 of the 15 species, indicating that populations should be separated in analyses among species. Comparison of morphological variation between microhabitat generalist and specialist species suggested that all species may vary in morphology relative to their environment. Regression analysis showed that within two families, Cyprinidae and Percidae, morphology was related to specific microhabitat variables. In the Centrarchidae, morphology was not related to any microhabitat variables. Morphological differences among the species occurred along gradients that were similar to gradients of habitat utilization, indicating that within a family, species widely separated in microhabitat use were morphologically different and species using similar microhabitats were similar in morphology. Our results suggest that patterns of morphological variation correspond to properties of the available habitat for warmwater stream fish species.
Allometry of home range size in lake and river fishes
Authors: Minns Charles K.
Published: April 2008

A data set assembled from published literature supported the hypotheses that (i) home range size increases allometrically with body size in temperate freshwater fishes, and (ii) fish home ranges are larger in lakes than rivers. The allometric model fitted was home range = A∙(body size)B. Home ranges in lakes were 19–23 times larger than those in rivers. Additional analyses showed that membership in different taxonomic groupings of fish, the presence–absence of piscivory, the method of measuring home range, and the latitude position of the water bodies were not significant predictive factors. Home ranges of freshwater fish were smaller than those of terrestrial mammals, birds, and lizards. Home ranges were larger than area per fish values derived by inverting fish population and assemblage density–size relationships from lakes and rivers and territory–size relationships in stream salmonids. The weight exponent (B) of fish home range was lower than values reported for other vertebrates, 0.58 versus a range of 0.96–1.14. Lake–river home range differences were consistent with differences reported in allometric models of freshwater fish density and production.
Assessment of forest GPP variations in central Italy
Authors: Rodolfi A. , Chiesi M. , Tagliaferri G. , Cherubini P. , Maselli F.
Published: April 2008

A debate is in progress concerning the possible effects of climate changes on the primary production of both natural and artificial ecosystems. The current investigation builds on the hypothesis that trends of increasing air temperature observed in several Italian regions should positively affect productivity of mountain forest ecosystems. Temperature rise in the Mugello valley (central Italy) in the period 1986–2001 was first confirmed by the analysis of data from a local station. The effects of this rise on the productivity of deciduous forest ecosystems (dominated by beech, Fagus sylvatica L.) were then analysed through estimates of the fraction of absorbed photosynthetically active radiation (FAPAR) derived from the US National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer satellite normalized difference vegetation index (NDVI) data. The use of a simplified parametric model (C-Fix) then allowed the combination of these FAPAR estimates with meteorological data (temperature and radiation) to produce annual values of forest gross primary productivity (GPP). Finally, validation of these GPP estimates was carried out by a comparison with dendrochronological measurements taken in the study forests. Because tree measurements were affected by external factors not exclusively related to forest GPP (stand aging, management practices, etc.), the comparison gave positive results only after applying a detrending operation to both series of annual GPP estimates and dendrochronological data. These results are a first indication that the rise in temperature that has occurred in Italy in the last decades has positively affected the productivity of mountain forest ecosystems.
Wolves, elk, and aspen in the winter range of Jasper National Park, Canada
Authors: Beschta R. L. , Ripple W. J.
Published: April 2008

We undertook a retrospective study of aspen age structure in the winter range of Jasper National Park to assess potential trophic cascades in wolf–elk–aspen systems. We compiled historical wolf ( Canis lupus Linnaeus, 1758) and elk ( Cervus elaphus Linnaeus, 1758) population data and, in 2005, sampled 42 trembling aspen ( Populus tremuloides Michx.) stands within the Palisades site along the Athabasca Valley near Jasper townsite and another 30 stands within the Willow Creek site in a relatively remote portion of the park. Results indicated that aspen recruitment (suckers or seedlings growing into tall saplings and trees) occurred at both sites in the early 1900s but decreased in the 1940s as elk numbers were reaching a maximum. Wolves were largely eliminated from the park in the mid-1900s, and aspen recruitment during that time ceased at both sites, apparently because of heavy browsing by elk. With recovery of wolf populations in the late 1960s and increasing predation risk, elk use of the Willow Creek site declined, and aspen recruitment resumed. However, at the Palisades site, an area of relatively low predation risk due to human use and developments, renewed aspen recruitment has not occurred. Results indicate that historical wolf or ungulate control programs and human developments influenced trophic cascades involving wolves, elk, and aspen in these winter ranges.
Hierarchical production planning in forestry using price-directed decomposition
Authors: Pittman Samuel D. , Bare B. Bruce , Briggs David G.
Published: April 2008

Forest planning models have increased in size and complexity as planners address a growing array of economic, ecological, and societal issues. Hierarchical production models offer a means of better managing these large and complex models. Hierarchical production planning models decompose large models into a set of smaller linked models. For example, in this paper, a Lagrangian relaxation formulation and a modified Dantzig–Wolfe decomposition – column generation routine are used to solve a hierarchical forest planning model that maximizes the net present value of harvest incomes while recognizing specific geographical units that are subject to harvest flow and green-up constraints. This allows the planning model to consider forest-wide constraints such as harvest flow, as well as address separate subproblems for each contiguous management zone for which detailed spatial plans are computed. The approach taken in this paper is different from past approaches in forest hierarchical planning because we start with a single model and derive a hierarchical model that addresses integer subproblems using Dantzig–Wolfe decomposition. The decomposition approach is demonstrated by analyzing a set of randomly generated planning problems constructed from a large forest and land inventory data set.