bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of the Brain–Pituitary Relationship: Evidence from the Agnatha
Authors: Gorbman Aubrey
Published: April 2008

In the brain of the lamprey there are neurosecretory cells that manufacture and carry known hormonal materials to the neurohypophysis, which is that part of the diencephalic floor that is adjacent to the adenohypophysis. The adenohypophysis is differentiated into a pars distalis and a pars intermedia. However, unlike all other vertebrates, there is no vascular or nervous connection between the neurohypophysis and the pars distalis. If there is any regulation of the adenohypophysis by the hormones released from the endings of neurosecretory axones in the neurohypophysis, it would have to be by diffusion across the intervening connective tissue. Such regulation remains to be demonstrated.It is difficult to decide whether this relationship between neurohypophysis and pars distalis in the lamprey (and hagfish) is primitive or degenerate in its evolution. However, in three groups of more primitive fishes an intermediate condition is found in which a vascular connection exists between the neurohypophysis and a part of the adenohypophysis. This being so, we may speculate that the lamprey and other cyclostomes represent the simplest and most primitive anatomical relationship between brain and adenohypophysis, one in which the two organs are merely apposed, allowing neurosecretions to diffuse between the two. In the elasmobranchs, holocephalians, and the coelacanth, part of the pars distalis has been vascularized by portal vessels beginning in the neurohypophysis. In all other vertebrates the entire pars distalis is so vascularized.Key words: brain, pituitary gland, neurosecretion, hormones, evolution, Lampetra richardsoni, L. tridentata, Petromyzon marinus
Changes in Biological Characteristics of the Sea Lamprey (Petromyzon marinus) as Related to Lamprey Abundance, Prey Abundance, and Sea Lamprey Control
Authors: Heinrich John W. , Weise Jerry G. , Smith Bernard R.
Published: April 2008

Biological characteristics of adult sea lampreys, Petromyzon marinus, in the Great Lakes changed in response to lamprey and prey abundance and the chemical control program. Sea lampreys collected as early as 1947, through 1978, from southern Lake Superior, northwestern Lake Michigan, the Ocqueoc River and Canadian shore of Lake Huron, and the Humber River of Lake Ontario were analyzed. Generally, abundance of sea lampreys peaked in each lake before the chemical control program began. The annual mean lengths and weights were relatively low when lampreys were abundant and increased as the numbers were reduced by the control efforts. As an indication of the change in sea lamprey weight per unit change in length, annual log10 weight on log10 length equations were solved at the arbitrary length of 410 mm. The values were plotted against years for each lake and interpreted with respect to chemical treatment periods. All slopes were negative before the control period and positive thereafter. Sea lamprey lengths and weights were low when fish stocks in the Great Lakes were near depletion. As salmonids again became abundant through stocking, lampreys grew larger. In Lake Superior, where detailed records on lake trout abundance have been available since 1959, a significant relation exists between the changes in the sea lamprey estimated weight values at 410 mm and in lake trout abundance (P < 0.01). Male sea lampreys were the dominant sex when populations of the parasite were high. A shift to a preponderance of females occurred as lamprey abundance declined.Key words: Petromyzon marinus, Salvelinus namaycush, abundance, sex ratio, weight–length relationship, chemical control
Biology of the North American Anadromous Sea Lamprey, Petromyzon marinus
Authors: Beamish F. W. H.
Published: April 2008

The sea lamprey (Petromyzon marinus) in the western Atlantic Ocean adjacent to North America is usually found within a depth of 200 m between latitudes of 30 and 53°. Spawning size lampreys have been recorded in 116 rivers between 32 and 48° latitude. The upstream spawning migration which may extend to several hundred kilometres, takes place between March and September, the actual time varying directly with latitude. Fecundity of the anadromous P. marinus (approximately 124 000–305 000) is the highest for any lamprey species. Energy requirements for migration and reproduction are discussed in the context of parental investment. The larval phase lasts 6–8 yr and is followed by a highly synchronous period of metamorphosis. On completion of metamorphosis in late autumn some juveniles migrate downstream to the estuary or ocean and commence feeding. In at least some rivers, a portion of the young juveniles overwinter in the natal stream without feeding. Subsequent to a short feeding period in May these young juveniles leave the river for the sea. Sea lampreys attack a variety of marine elasmobranchs and teleosts. Only swordfish, Xiphias gladius, and striped bass, Roccus saxatilis, are reported to eat lampreys. During the marine interval, which lasts from 23 to 28 mo, the calculated instantaneous growth rate is 0.645–0.785 g∙d−1. Lamprey scarring frequency on Atlantic salmon, Salmo salar, in the St. John River, New Brunswick, increased from 2.6 to 15.0% between 1972 and 1975 coincident with a dramatic rise in the number of migrant salmonids. Scars were most prevalent on larger salmon, particularly females. Most scars were recorded on the right side of salmon, particularly in the ventral regions.Key words: sea lamprey, Atlantic Ocean, distribution, life cycle, growth, energetics, fecundity
Distribution and Abundance of European River Lamprey (Lampetra fluviatilis) Larvae in Three Rivers Running into Bothnian Bay, Finland
Authors: Kainua K. , Valtonen T.
Published: April 2008

Larvae of parasitic European river lamprey (Lampetra fluviatilis) were studied in the Kalajoki, Pyhäjoki, and Siikajoki rivers which flow into Bothnian Bay in Finland. In the Kalajoki river, ammocoetes occur up to 40 km upstream from the mouth, but in the Pyhäjoki rapids block most of the adult migration about 20 km from the river mouth. The Siikajoki river is blocked by a hydroelectric dam 16 km from the estuary. The mean abundance of larvae in 1977 was 12/m2 in the Pyhäjoki and 21/m2 in the Siikajoki river. In 1978 the mean abundance was 6/m2 in the best area (an 8-km stretch) of the Kalajoki, 15/m2 in the Pyhajoki, and 21/m2 in the lower 7 km of the Siikajoki river. The mean length of larvae was smallest in the Siikajoki (45 mm in 1977 and 55 mm in 1978) and largest in the Kalajoki river (77 mm in 1978). Reasons for such size differences and the variation in year-class strengths may be attributable to oxygen deficiencies and other problems caused by dams and other construction work on the rivers. Both the Siikajoki and Kalajoki rivers appear to be affected in this way. The Pyhäjoki appears to be the least disturbed of the three rivers. Ammocoetes favor mean grain sizes from 0.05 to 0.10 mm. Myomere studies on larvae from the Siikajoki river gave a mean count of 62.3 (range, 60–64) and verified that the larvae involved were those of the river lamprey.Key words: lamprey, Finland, larvae, ammocoete, Lampetra fluviatilis, European river lamprey
Ecology of the European River Lamprey (Lampetra fluviatilis) in Northern Sweden
Authors: Sjöberg K.
Published: April 2008

River lamprey is widely distributed along most of the Swedish coast and is the basis for a number of fisheries. The length of larval life in the river is uncertain. Metamorphosed lampreys (mean length: 105 mm) move downstream at night, mainly during March to May. The upstream spawning run of adults from the sea starts in August and continues for many months. During this migration large numbers of lampreys are caught in traps by fishermen. Spawning takes place in late May or early June when the water temperature reaches about 10°C. Adult lampreys have several predators in the river, especially certain birds (goosander, Mergus merganser) and fish (burbot, Lota lota).Key words: lamprey, Sweden, fishery, larvae, metamorphosis, age, length, spawning, predators, migration
Scarring of Whitefish (Coregonus lavaretus) by European River Lamprey (Lampetra fluviatilis) in Loch Lomond, Scotland
Authors: Maitland P. S.
Published: April 2008

Whitefish are abundant in Loch Lomond and have been attacked by lampreys for over 100 yr. In all samples (totalling about 1000 whitefish) taken from different parts of the loch between 1951 and 1979 the incidence of lamprey scarring was high (from 26 to 50%), many times that of any of the other 14 species of fish in the loch. Multiple scarring was common. Small whitefish (less than 25 cm) were rarely scarred, whereas larger ones (more than 25 cm) frequently had been attacked. Scars occurred all the year round, but fresh wounds only in the summer — especially July and August. Almost all the scars occurred along the backs of the fish between the head and adipose fin, and above the lateral line. There is little evidence that these attacks affected the growth or condition of the whitefish concerned. Lampreys do not appear to attack fish in freshwater in other parts of Great Britain, but parasitism has been recorded in a few lakes in Finland and Russia.Key words: scarring, Coregonus lavaretus, Lampetra fluviatilis, Scotland
Response of Lake Whitefish (Coregonus clupeaformis) to the Control of Sea Lamprey (Petromyzon marinus) in Lake Huron
Authors: Spangler George R. , Collins John J.
Published: April 2008

Changes in population parameters of three stocks of whitefish (Coregonus clupeaformis) in Lake Huron following control of sea lamprey (Petromyzon marinus) have varied between the major basins of the lake. In the North Channel and main basin, whitefish survival rates increased significantly, from values of 23 to 37% and 16 to 24%, respectively. In both areas the abundance of lamprey declined while whitefish increased. In Georgian Bay, whitefish populations did not reflect changes attributable to lamprey control, possibly because of low lamprey abundance. During the control period, whitefish survival rates declined from 57 to 39%, abundance declined and growth rates increased.Key words: Lake Huron whitefish, lamprey control, Petromyzon marinus
Lake Trout (Salvelinus namaycush) and Sea Lamprey (Petromyzon marinus) Populations in Lake Michigan, 1971–78
Authors: Wells LaRue
Published: April 2008

Lake trout (Salvelinus namaycush) was exterminated in Lake Michigan by the mid-1950s as a result of the combined effects of an intensive fishery and predation by the sea lamprey (Petromyzon marinus). The widespread application of lampricide in tributary streams had greatly reduced the abundance of lampreys by the early 1960s, and a program to restore self-sustaining populations of lake trout through stocking of yearlings and fingerlings was initiated in 1965. Although the hatchery-reared fish spawned widely in Lake Michigan each year after 1970, no progeny were observed except in an isolated area in Grand Traverse Bay. During 1971–78, sea lamprey abundance was generally greater in Wisconsin than in other parts of the lake. However, the rate of occurrence of sea lamprey wounds on lake trout dropped dramatically there in 1978 after the Peshtigo River, a tributary to Green Bay, was treated with lampricide. Application of Lake Michigan wounding rates to a regression model relating mortality to lamprey wounding developed from Lake Superior data, yielded lamprey-induced mortality estimates in 1977 of 5% in Michigan plus Indiana (combined) and 31% in Wisconsin; corresponding estimates for 1978 were 5 and 15%.Key words: lake trout, sea lamprey predation, abundance, Lake Michigan
Changes in Mortality of Lake Trout (Salvelinus namaycush) in Michigan Waters of Lake Superior in Relation to Sea Lamprey (Petromyzon marinus) Predation, 1968–78
Authors: Pycha Richard L.
Published: April 2008

Total mortality rates of lake trout (Salvelinus namaycush) of age VII and older from eastern Lake Superior were estimated from catch curves of age distributions each year in 1968–78. The instantaneous rate of total mortality Z varied from 0.62 to 2.31 in close synchrony with sea lamprey (Petromyzon marinus) wounding rates on lake trout. The regression of transformed Z on the index of lamprey wounding, accounted for over 89% of the variation in lake trout mortality (r2 = 0.893). An iterative method of estimating rates of exploitation u, instantaneous rates of fishing mortality F, K (a constant relating sample catch per unit effort to population size), instantaneous normal natural mortality rate M, and instantaneous rate of mortality due to sea lamprey predation L from the sample catch per unit effort and total catch by the fishery is presented. A second method using the results of a 1970–71 tagging study to estimate the mean F in 1970–77 yielded closely similar results to the above and is presented as corroboration. The estimates of u, F, and M appear to be reasonable. F ranged from 0.17 in 1974 to 0.42 in 1969 and M was estimated at 0.26. L varied from 0.21 in 1974 to 1.70 in 1968. Management implications of various policies concerning sea lamprey control, exploitation, and stocking are discussed.Key words: lake trout, sea lamprey, lamprey control, mortality, predation, Lake Superior, fishery, management
Pheromone Communication in Sea Lampreys (Petromyzon marinus): Implications for Population Management
Authors: Teeter John
Published: April 2008

The results of recent preference tests indicate that both male and female landlocked sea lampreys (Petromyzon marinus), after reaching a specific stage of sexual maturation, release pheromones which attract conspecifics of the opposite sex. In addition, sexually immature males, captured at the beginning of a spawning migration, exhibit a preference for water in which sea lamprey larvae have been held, suggesting that chemical signals, originating from populations of sea lamprey larvae in a river, may aid migrating adults in selecting a suitable spawning stream. The possible influence of a number of environmental and physiological factors on pheromone communication in sea lampreys is discussed. Synthetic pheromones have been utilized in insect pest management programs as lures for mass-trapping one or both sexes and for disrupting normal pheromone communication. Similar strategies may be applicable in an integrated program of sea lamprey population management.Key words: pheromones, reproduction, spawning migration, sea lampreys, population management, preference behavior
A Synthesis of Knowns, Unknowns, and Policy Recommendations from the Sea Lamprey International Symposium
Authors: Walters Carl J. , Spangler George , Christie W. J. , Manion Patrick J. , Kitchell James F.
Published: April 2008

The Sea Lamprey International Symposium (SLIS) has provided a broad spectrum of facts and speculations for consideration in future research and management programs. Many aspects of the laboratory biology and field life history of the sea lamprey (Petromyzon marinus) are now well understood. There is little question that it can now be controlled by chemical larvicides, and perhaps in the future by more efficient integrated control programs. There is correlative evidence (wounds, scars, catch curves) that lamprey caused major mortalities in some fish species, and that control in conjunction with stocking has lead to remarkable recoveries of salmonid stocks in the Great Lakes. However, there are great gaps in understanding about just what the lamprey does under field conditions, and it is not yet possible to reject several hypotheses that assign lamprey a minimum or transient role in fish stock changes. Further studies on details of lamprey biology are, in themselves, unlikely to fill the gaps; one alternative is to conduct a large-scale field experiment involving cessation of lamprey control while holding other factors (fishing, stocking) as steady as possible. If it is decided to proceed with management on the assumption that lamprey are important, without the major field experiments to confirm it, then at least the following steps should be taken: (1) the chemical treatment program should be reviewed in detail, with a view to finding treatment schedules that will minimize frequency and dose rates for lampricide applications; (2) pilot studies on alternative control schemes (sterile male, attractants, barriers) should only be funded if they are statistically well designed (several replicate and control streams), and involve quantitative monitoring of lamprey spawning success and subsequent total production of transforming larvae; (3) the lake trout (Salvelinus namaycush) stocking program should be maintained at its present level, and should involve diverse genotypes rather than a few hatchery strains; (4) growth in the sport fisheries for lake trout should be curtailed, and commercial fisheries should not yet be permitted; (5) a multispecies harvesting policy should be designed that takes into account the buffering effect of each species on lamprey mortality suffered by others (i.e. should some species not be harvested at all, and viewed instead as buffers for more valuable species?); and (6) a program should be developed for restoring, by culture if necessary, native forage species in case the introduced smelt and alewife should collapse under pressure from fishing and prédation by the growing salmonid community.Key words: sea lamprey, proposed research, fishery management, mathematical models, population dynamics
Occurrence of the Toxic PhytoflagellatePrymnesium parvumand Associated Fish Mortality in a Norwegian Fjord System
Authors: Kaartvedt S. , Johnsen T. M. , Aksnes D. L. , Lie U. , Svendsen H.
Published: April 2008

At the end of July 1989, toxin-producing Prymnesium parvum was spread through a fjord system in the surge of freshwater released from a hydroelectric power plant. In total, 750 tonnes of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) died in fish farms. Prymnesium parvum germinated in the brackish surface layer of a fjord branch which, during July, was characterized by longer residence time, higher temperatures, and lower nitrogen and silicate concentrations than the rest of the fjord system. Nutrient loading (especially phosphate) from fish farms may, however, have stimulated local growth of the alga. At the time of the first observed fish mortality, the salinity was 5‰ and the temperature 18 °C. Pelagic concentrations of P. parvum were generally low, with a maximum of 2.2 × 106cells∙L−1found close to a fish farm. Denser concentrations of P. parvum were, however, found in association with benthic substrates. Phosphorus limitation was probably important for the production of toxin by P. parvum.
Use of Size–Frequency Data to Estimate the Age Composition of Crayfish Populations
Authors: France Robert , Holmes John , Lynch Alejandro
Published: April 2008

Age-classes in crayfish populations can be determined from size–frequency data provided four tenets are adhered to: (1) only crayfish collected from areas of rock substrate are used; (2) trapping data are excluded; (3) species do not have longevities exceeding about 4 yr; and most importantly, (4) sample sizes are greater than about 200. Studies that have failed to follow these guidelines have met with limited success in dissecting mixed frequency distributions. Further, three validation procedures must be undertaken: (1) temporal replication within molting events to measure the precision of both data collection and size–frequency analysis; (2) corroboration with known-age crayfish from either field recaptures or laboratory molt increments; and (3) concordance with independent analysis of the mean size at onset of sexual maturity. When these checks support the size–frequency results, population age composition and analyses of rates of growth or mortality can be considered reliable.
Effects of Prolonged Flooding on Nektonic Invertebrates in Small Diked Marshes
Authors: Murkin Henry R. , Kadlec John A. , Murkin Elaine J.
Published: April 2008

This study examined the response by nektonic invertebrates to prolonged flooding of a series of experimental marshes in the Delta Marsh in south-central Manitoba. Prior to flooding, nektonic invertebrate densities, biomass, and numbers of taxa were at their highest levels during midsummer in open-water sites with dense submersed vegetation; during the same period, nekton levels within the experimental marshes were minimum in stands of emergent vegetation. These differences appear to be related to available habitat structure and dissolved oxygen concentrations. Flooding to 1 m above normal eliminated the submersed vegetation and existing emergent vegetation. This resulted in a single large input of litter at the time of flooding with little or no subsequent input during flooding. The herbivore–detritivore functional group reached high levels early in the first year of flooding and remained high until late in the second year of flooding. The predator–parasite group did not exhibit a similar increase following flooding. Changes in the amount of plant litter available as both food and habitat affected these changes in the nekton following flooding. Wind-induced water currents also probably had an effect on nekton distributions during the flooding period.
Estimation of Temporal Acidification of Central Ontario Lakes
Authors: Johnson M. G. , George S. E. , Kelso J. R. M.
Published: April 2008

The Wright–Henriksen model was used to estimate chemical changes in 255 central Ontario lakes attributable to strong acid loading. Background SO42− in precipitation, 14.5 μeq∙L−1, was estimated by analysis of "clean" events in contemporary data and used to determine background SO42− in lakes, which averaged 26 μeq∙L−1. Net (excess) SO42− averaged approximately 100 μeq∙L−1. An empirical function was used to calculate ANC0 (at historical t0) and ANC loss from net SO42−. Then, pH0 was estimated from ANC0, obtained with empirical and theoretical relationships of contemporary pHc and ANCc. Almost all of ANC0 of 125 μeq∙L−1 on average was lost in one group of lakes near Sudbury. Associated mean pH decrease was 0.8–1.4 depending on the model used. Approximately 60–70% of ANC0 of 110 μeq∙L−1 was lost, with a pH decrease of 0.3–0.8, in lakes of two groups near Parry Sound. Only 20–30% of ANC0 of 160 μeq∙L−1 had been lost, with little pH change, in a group of lakes closer to Sault Ste. Marie. Such estimates are required for a rational interpretation of data on the distribution of fish species in Ontario lakes and estimation of losses of fish.
Factors Related to the Biomass and Production of Fish Communities in Small, Oligotrophic Lakes Vulnerable to Acidification
Authors: Kelso J. R. M. , Johnson M. G.
Published: April 2008

We estimated biomass and production of the fish community in 19 small (<50 ha) lakes from four watersheds in central Ontario. Lake pH ranged from 4.8 to 7.1. We found 19 fish species in these lakes; yellow perch (Perca flavescens), pumpkinseed (Lepomis gibbosus), white sucker (Catostomus commersoni), and largemouth bass (Micropterus salmoides) were the most common. On average, there were 4.5 species per lake. Neither fish community biomass nor production was significantly different among the communities identified by cluster analysis, and the number offish species was not lower at lower pH. More than 75% of each lake's total biomass was confined to less than three fish species. Whole-lake fish biomass was related to the total number of species in the lakes and their average age. Fish community production was related to fish biomass, averge fish size, and acid neutralizing capacity (ANC) with an almost equal influence provided by each factor. At lower ANC and pH, fish were usually smaller in weight and often had lower population growth rates. In these lakes where the influence of lake size and trophic status was minimized, fish community biomass and production were only secondarily related to lake pH or ANC.
Further Perspectives on Yield per Recruit Analysis and Biological Reference Points
Authors: Norris James G.
Published: April 2008

Spawner–recruit relationships (SRRs) are indeterminate for most species. Earlier workers proposed solving "amount of harvest" problems for such cases by tacitly assuming that the SRR is density independent (a straight line through the origin) for the available data. I extend that concept and demonstrate a technique for solving "method of harvest" problems when the SRR is indeterminate. This technique uses spawning biomass per recruit, rather than fishing effort, as the benchmark for comparing alternative methods of harvest. Yields from different harvesting methods are deemed comparable only when they produce the same spawning biomass per recruit. If the comparisons are consistent over the entire range of spawning biomass per recruit values, one can evaluate the relative merits of competing methods of harvest without the benefit of spawner–recruit data. Although this technique does not determine the optimal gear selectivity, it allows comparisons of sustainable yields from currently available gear types. The technique is particularly useful for analyzing fishery allocation and by-catch problems. Two life history parameters, critical age (age at which a cohort maximizes its biomass or dollar value) and the age at 50% sexual maturity, may be most important in determining the optimal method of harvest (fishing gear selectivity).
Diel and Seasonal Changes in Resting Levels of Various Blood Parameters in Brook Trout (Salvelinus fontinalis)
Authors: Audet Céline , Claireaux Guy
Published: April 2008

Plasma osmolality, chloride, glucose, Cortisol, thyroid hormones, and blood hematocrit all varied seasonally in freshwater-adapted, age 1 + brook trout (Salvelinus fontinalis) kept under natural photoperiod and water temperatures. In addition, plasma osmolality, Cortisol, and thyroxine all displayed diel cycles that differed from month to month. High Cortisol levels were related to sexual maturation and possibly to low water temperatures. Seasonal cycles of plasma thyroid hormones did not seem to be influenced by water temperature. Plasma osmolality, chloride, glucose, and thyroxine showed small but significant seasonal changes similar to the variations observed at the time of smoltification in other salmonid species.
Piscivory, Growth, and Size-Selective Mortality of Age 0 Pikeperch (Stizostedion lucioperca)
Authors: Buijse Anthonie D. , Houthuijzen Rob P.
Published: April 2008

Year-class strength of pikeperch (Stizostedion lucioperca), indexed as the age 0 abundance in trawl surveys, varied 300-fold in the northern part of Lake IJssel, The Netherlands, over the period 1966–89. Both mean length and year-class strength of age 0 pikeperch in November were highly correlated with mean summer temperature. Depending on the environmental conditions, especially water temperature and availability of food, the initially unimodal length frequency distribution of age 0 pikeperch developed into a positively skewed, bimodal or negatively skewed distribution towards the end of the summer. Strong year-classes were characterised by larger mean lengths and a negatively skewed frequency distribution, while weak year-classes were smaller and positively skewed. Stomach contents consisted of zooplankton and macrofauna for the smaller specimens and of age 0 smelt (Osmerus eperlanus) for the larger pikeperch (> 10 cm). Body energy content increased with fish length, and differences in proximate analysis were more pronounced later in the season. The condition of nonpiscivorous age 0 pikeperch was low and decreased over time, while that of piscivorous pikeperch increased. The onset of piscivory, favoured by high temperatures during summer, has a direct positive effect on the growth and survival of age 0 pikeperch.
Use of Risk Analysis to Assess Fishery Management Strategies: A Case Study using Orange Roughy (Hoplostethus atlanticus) on the Chatham Rise, New Zealand
Authors: Francis R. I C. C.
Published: April 2008

Risk analysis can enhance the value of scientific advice to fishery managers by expressing the uncertainty inherent in stock assessments in terms of biological risk. I present a case study involving an overexploited population of orange roughy (Hoplostethus atlanticus) on the Chatham Rise, New Zealand. This analysis quantifies the risk to the fishery and shows how this decreases as the rate of reduction in total allowble catch increases. The technique helps fishery managers balance biological risk against economic risk. Ways of generalizing the technique are discussed.
Histopathology of Rainbow Trout (Oncorhynchus mykiss) after Long-Term Exposure to Biologically Treated Bleached Kraft Mill Effluent in Experimental Stream Channels
Authors: Hall Timothy J. , Haley Richard K. , Borton Dennis L. , Walsh Alexander H. , Wolke Richard E.
Published: April 2008

Outdoor experimental streams were used to determine the effects of effluent on histopathology of rainbow trout (Oncorhynchus mykiss). Studies were conducted for 10–11 mo using biologically treated bleached kraft mill effluent at concentrations ranging from 0.5 to 2.0 mg∙L−1 of effluent BOD5 (1.3–5.1% v/v) and for 42 mo at 0.5 BOD5 addition (1.5% v/v). Twenty different tissues from randomly selected fish were examined at the end of each exposure period. Lesions or tissue changes observed in fish from both control and effluent-treated streams were of primary or secondary parasite-induced etiology, a condition typical of natural streams. There was an absence of neoplasia over the range of concentrations. Hematocrit, leucocrit, and liver somatic index remained normal throughout the course of effluent exposure. These data corroborate the lack of effluent effects as determined from measurements of trout growth, survival, production, and reproduction.
Spatial Aggregation, Precision, and Power in Surveys of Freshwater Mussel Populations
Authors: Downing John A. , Downing William L.
Published: April 2008

We studied aggregation in 76 populations of freshwater mussels from relatively homogeneous surroundings in a wide range of habitats. Chi-square tests for spatial aggregation found only 53% of mussel populations significantly (p < 0.05) aggregated. The variance of replicate mussel samples (s2) varied with the mean number collected (m) as 1.49m1.17, but conformed to the general variance relation found for other aquatic taxa (m1.5) at m > 1. The number of replicate samples ([Formula: see text]) required to estimate mussel abundance with a given level of precision (D = SE/m) is approximately m−0.5D−2. Sampling mussels with large quadrats requires between 5 and 25 samples for 20% precision. Sampling designs to determine significant impacts (α = (β = 0.05) require 7–50 samples of each population to detect doubling or halving of the population density, or three to nine to detect order-of-magnitude changes. Large sampling units are recommended to ensure acceptable sampling precision and accurate chi-square analyses of spatial aggregation and to permit ecologists to detect significant impacts on freshwater mussel populations.
Biotic and Abiotic Determinants of the Diet of Brook Trout, Salvelinus fontinalis, in Lakes of the Laurentian Shield
Authors: Lacasse Sylvain , Magnan Pierre
Published: April 2008

From a survey of 12 lakes containing brook trout, Salvelinus fontinalis, 12 lakes containing brook trout and creek chub, Semotilus atromaculatus, and 13 lakes containing brook trout and white sucker, Catostomus commersoni, we built seven multiple linear regression models to account for the mean percent weight of different prey categories in the diet of brook trout. Presence of chub and sucker, zooplankton community structure, sampling date, morphoedaphic index, and the importance of rock outcrops accounted for 88% of the variation in weight of zoobenthos eaten by trout, which was the preferred prey in allopatry. Thirty percent of the variation in weight of zooplankton eaten by trout was explained by the importance of macrophytes and other refuges for fish. Models for amphipods, dipteran pupae, swimming insects, terrestrial insects, and prey-fish explained between 36 and 63% of the variation. The presence of white sucker or an index of their impact (mean length or density of Cladocera) and the characteristics of littoral habitats appeared in six of seven models. Littorasl habitats seemed particularly determinant for the inclusion of prey-fish in the diet, more prey-fish being eaten when regufes were abundant. Variables related to lake morphometry and physicochemistry appeared less regularly in the models.
On the Chemical Form of Mercury in Edible Fish and Marine Invertebrate Tissue
Authors: Bloom Nicolas S.
Published: April 2008

Total mercury, monomethylmercury (CH3Hg), and dimethylmercury ((CH3)2Hg) in edible muscle were examined in 229 samples, representing seven freshwater and eight saltwater fish species and several species of marine invertebrates using ultraclean techniques. Total mercury was determined by hot HNO3/H2SO4/BrClldigestion, SnCl2 reduction, purging onto gold, and analysis by cold vapor atomic fluorescence spectrometry (CVAFS). Methylmercury was determined by KOH/methanol digestion using aqueous phase ethylation, cryogenic gas chromatography, and CVAFS detection. Total mercury and CH3Hg concentrations varied from 0.011 to 2.78 μg∙g−1 (wet weight basis, as Hg) for all samples, while no sample contained detectable (CH3)2Hg (<0.001 μg∙g−1 as Hg). The observed proportion of total mercury (as CH3Hg) ranged from 69 to 132%, with a relative standard deviation for quintuplicate analysis of about 10%; nearly all of this variability can be explained by the analytical variability of total mercury and CH3Hg. Poorly homogenized samples showed greater variability, primarily because total mercury and CH3Hg were measured on separate aliquots, which vary in mercury concentration, not speciation. I conclude that for all species studied, virtually ail (>95%) of the mercury present is as CH3Hg and that past reports of substantially lower CH3Hg fractions may have been biased by analytical and homogeneity variability.
Spatial and temporal variation in littoral-zone benthic invertebrates from three south-central Ontario lakes
Authors: Reid R. A. , Somers K. M. , David S. M.
Published: April 2008

Surveys of benthic invertebrates have revealed patterns attributed to the impacts of acid deposition. Unfortunately, these patterns may be confounded by temporal variation that will affect follow-up studies of the recovery of these communities. Here, we assess spatial and temporal variation in time-limited, kick-and-sweep collections of littoral-zone benthos. Spatial variation comprised five sites representing the predominant nearshore substrates in each of three lakes. Temporal variation spanned a different scale in each lake with five sites sampled: (i) twice on the same day, (ii) once a week for 3 weeks, and (iii) four times through the ice-free season. Variation was quantified using a model II analysis of variance. Spatial differences predominated in same-day samples (60.4% of the variation on average) and those collected over a 3-week period (46.1%). In contrast, samples collected over the ice-free season revealed that spatial and temporal factors accounted for 9.4 and 25.6% of the variation. We conclude that our collections of littoral macrobenthos are highly repeatable if sampling is restricted to short periods (e.g., 3 weeks). Surveys spanning longer periods may incorporate considerable temporal variation from seasonal changes in abundance.
Population viability of the Snake River chinook salmon (Oncorhynchus tshawytscha)
Authors: Emlen John M.
Published: April 2008

In the presence of historical data, population viability models of intermediate complexity can be parameterized and utilized to project the consequences of various management actions for endangered species. A general stochastic population dynamics model with density feedback, age structure, and autocorrelated environmental fluctuations was constructed and parameterized for best fit over 36 years of spring chinook salmon (Oncorhynchus tshawytscha) redd count data in five Idaho index streams. Simulations indicate that persistence of the Snake River spring chinook salmon population depends primarily on density-independent mortality. Improvement of rearing habitat, predator control, reduced fishing pressure, and improved dam passage all would alleviate density-independent mortality. The current value of the Ricker α should provide for a continuation of the status quo. A recovery of the population to 1957–1961 levels within 100 years would require an approximately 75% increase in survival and (or) fecundity. Manipulations of the Ricker β are likely to have little or no effect on persistence versus extinction, but considerable influence on population size.
Toward a definition of conservation principles for fisheries management
Authors: Olver C. H. , Shuter B. J. , Minns C. K.
Published: April 2008

Conservation, like beauty, is clearly in the eye of the beholder. The lack of a clear definition of what is meant by the term conservation, however, may encourage misconceptions about the degree to which biological objectives can be traded off against pressing economic and social objectives. Our purpose is to promote a dialogue about the meaning and practice of conservation, which might lead toward consensus on essential biological objectives. We present a brief history of the philosophical evolution of the term conservation and offer a definition of conservation based on the argument for an ecological ethic. This ethic requires that human benefits be derived in a sustainable manner and recognizes that human uses need to be reconciled with intrinsic and necessary ecosystemic functions and structures. We then present a preliminary set of operating principles applicable to the management of fish stocks that are consistent with an ecological or ecosystemic view of conservation. By proposing a set of conservation principles for fisheries management we hope to initiate a debate about just what those principles ought to be.
The Richit–Richards family of distributions and its use in forestry
Authors: Wang Mingliang , Ramesh N. I. , Rennolls Keith
Published: April 2008

Johnson’s SBand the logit–logistic are four-parameter distribution models that may be obtained from the standard normal and logistic distributions by a four-parameter transformation. For relatively small data sets, such as diameter at breast height measurements obtained from typical sample plots, distribution models with four or less parameters have been found to be empirically adequate. However, in situations in which the distributions are complex, for example in mixed stands or when the stand has been thinned or when working with aggregated data, then distribution models with more shape parameters may prove to be necessary. By replacing the symmetric standard logistic distribution of the logit–logistic with a one-parameter “standard Richards” distribution and transforming by a five-parameter Richards function, we obtain a new six-parameter distribution model, the “Richit–Richards”. The Richit–Richards includes the “logit–Richards”, the “Richit–logistic”, and the logit–logistic as submodels. Maximum likelihood estimation is used to fit the model, and some problems in the maximum likelihood estimation of bounding parameters are discussed. An empirical case study of the Richit–Richards and its submodels is conducted on pooled diameter at breast height data from 107 sample plots of Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.). It is found that the new models provide significantly better fits than the four-parameter logit–logistic for large data sets.
Interactive effects of condensed tannin and cellulose additions on soil respiration
Authors: Madritch Michael D. , Jordan Lisa M. , Lindroth Richard L.
Published: April 2008

Plant polyphenolics are receiving increased attention for their influences on belowground processes. Tannins are of particular interest because of their predominance in natural systems, their wide variation in both quality and quantity, and their protein-binding abilities. Current theory holds that simple phenolics increase microbial activity by acting as carbon substrates, while larger tannins decrease microbial activity by binding with organic nitrogen such as proteins. Here, we present results from a simple microcosm experiment that demonstrates that the influence of condensed tannins on soil respiration depends on the availability of additional carbon substrates. We purified tannins from trembling aspen ( Populus tremuloides Michx.) and crossed three levels of tannin additions with three levels of cellulose additions in laboratory microcosms. Soil respiration was measured over 36 days. In the absence of cellulose, high amounts of condensed tannins increased cumulative soil respiration. In the presence of abundant cellulose, condensed tannins decreased cumulative soil respiration. The positive and negative effects of purified tannins on soil respiration are time dependent, such that initial respiration is likely tannin induced, while later respiration is cellulose induced and tannin limited.
Growth of epiphytic old forest lichens across climatic and successional gradients
Authors: Gauslaa Y. , Palmqvist K. , Solhaug K. A. , Holien H. , Hilmo O. , Nybakken L. , Myhre L. C. , Ohlson M.
Published: April 2008

This paper aims to assess the influence of canopy cover on lichen growth in boreal forests along a regional forest gradient. Biomass and area gain, and some acclimation traits, were assessed in the old-forest lichens Lobaria pulmonaria (L.) Hoffm., Pseudocyphellaria crocata (L.) Vain., and Usnea longissima Ach. transplanted 110 days in three successional Norway spruce ( Picea abies (L.) Karst.) forest stands (clearcut, young, and old forest) repeated along a rainfall gradient (continental, suboceanic, and Atlantic zones) in Scandinavia. Lichen growth peaked in Atlantic rainforests with mean dry matter (DM) gain up to 36%–38%. The alectorioid lichen U. longissima showed the widest range of growth responses and no signs of chlorophyll degradation. Its highest DM gain consistently occurred in clearcuts, whereas the DM gain was close to zero in the shadiest young forest. The two foliose lichens L. pulmonaria and P. crocata exhibited maximal growth rates in old forests, but apparently growth was limited by low light even in old forests. Their DM gain was reduced in the most sun-exposed clearcuts due to chlorophyll degradation and was relatively high under closed young canopies, suggesting a better adaptation to shade. The lichen responses show that a high frequency and dominance of young and dense fast-growing forest stands at a landscape level are not compatible with large populations of these old-forest lichens and that a lack of lichens under an industrial forestry regime may not necessarily be determined by low dispersal efficiency only.
Effects of two silvicultural regimes with large tree retention on epiphytic macrolichen communities in Adirondack northern hardwoods, New York, USA
Authors: Root Heather T. , McGee Gregory G. , Nyland Ralph D.
Published: April 2008

We sampled epiphytic lichen communities in nine Adirondack northern hardwood stands: three old growth, three reserve shelterwood, and three single-tree selection systems. Our objectives were to assess the effects of treatment, tree diameter at breast height, and their interaction on lichen communities and to determine whether lichen traits were associated with particular habitats. Lichen community composition was strongly related to tree diameter at breast height and differed between old growth and reserve shelterwoods. Lichen community composition was also related to an interaction between tree size and stand type. Lobaria pulmonaria (L.) Hoffm. was associated with large trees in old growth, whereas Evernia mesomorpha Nyl., Parmelia sulcata Taylor, and Physcia millegrana Degel. characterized those in shelterwood stands. Nitrophilous lichens were most common on small trees and in reserve shelterwoods, whereas small trees in selection systems and old growth supported lichens that were found to be most associated with larger trees overall. Selection systems apparently maintained lichen communities indistinguishable from those in old growth or reserve shelterwood. Because large trees hosted unique epiphyte assemblages particularly rich in fruticose and cyanolichen species, we expect that management retaining few or no large trees will alter epiphytic lichen communities.
Relationships among litterfall, fine-root growth, and soil respiration for five tropical tree species
Authors: Valverde-Barrantes Oscar J.
Published: April 2008

Although significant advances have been made in understanding terrestrial carbon cycling, there is still a large uncertainty about the variability of carbon (C) fluxes at local scales. Using a carbon mass-balance approach, I investigated the relationships between fine detritus production and soil respiration for five tropical tree species established on 16-year-old plantations. Total fine detritus production ranged from 0.69 to 1.21 kg C·m–2·year–1with significant differences among species but with no correlation between litterfall and fine-root growth. Soil CO2emissions ranged from 1.61 to 2.36 kg C·m–2·year–1with no significant differences among species. Soil respiration increased with fine-root production but not with litterfall, suggesting that soil C emissions may depend more on belowground inputs or that both fine root production and soil respiration are similarly influenced by an external factor. Estimates of root + rhizosphere respiration comprised 52% of total soil respiration on average, and there was no evidence that rhizosphere respiration was associated with fine-root growth rates among species. These results suggest that inherent differences in fine-root production among species, rather than differences in aboveground litterfall, might play a main role explaining local-scale, among-forest variations in soil C emissions.
Forest soil rehabilitation with tillage and wood waste enhances seedling establishment but not height after 8 years
Authors: Bulmer C. , Venner K. , Prescott C.
Published: April 2008

We evaluated soil conditions of rehabilitated log landings in the Interior Douglas-fir biogeoclimatic zone of British Columbia during the first 3 years after treatment and the growth of lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) on these log landings over 8 years. Rehabilitation treatments included combinations of tillage and the addition of either stockpiled topsoil or one of three organic amendments: hog fuel, sort-yard waste, and a wood waste – biosolids compost. The woody amendments were either applied as a surface mulch or incorporated into the soil after tillage. Tillage and addition of wood waste reduced soil bulk density and increased carbon content. Daytime soil temperatures in summer were lower under a hog fuel mulch than for the other treatments. The plots receiving hog fuel also had higher soil moisture content. One year after treatment, soil mechanical resistance for untreated soils, and those that were simply tilled, exceeded 2500 kPa for much of the growing season. Plots receiving wood waste had lower mechanical resistance. Use of wood waste in rehabilitation improved soil conditions and contributed to improved survival rates for planted lodgepole pine seedlings. Height growth after 8 years was not significantly affected by the treatments.