bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differences in habitat distribution of a planktonic copepod, Eudiaptomus gracilis
Authors: Svensson Jan‐Erik
Published: July 2006

The spatial distribution of adult males and females in a population of the copepod Eudiaptomus grachs; was studied throughout one year The sexes were markedly segregated in spring and under ice in late winter This skewed distribution was mainly due to a strong concentration of females in deep water in the lake centre Males were more evenly distributed but dominated in relative terms strongly over females near the surface and the littoral zone Among females, those carrying eggs were most concentrated in deep regions Also during summer, females in the lake centre showed a marked abundance peak in deep water but the distribution of egg‐carrying females did not differ from other females During autumn and early winter, differences in the distribution of the sexes were minor The distribution of the sexes is discussed in relation to predators, temperature, food, and mates Female copepods are susceptible to fish predation when carrying eggs Fish may contribute to the over‐representation of females in deep regions by eating or scaring away this category of vulnerable prey from littoral areas and from the surface waters The fish predation hypothesis does not accurately predict the seasonal occurrence of the skewed distribution, however Feeding rate of fish is most likely low under ice Reproductive advantages in the warmer deep water may have contributed to female choice of habitat in late winter In spring and late winter proportionally fewer females near the surface and shore carried eggs, but they earned more spermatophores This indicates that these females were more receptive to matings Phytoplankton biomass was higher near the surface Thus, males may have gamed mating advantages and more food by avoiding deep water in the centre of the lake
Effects of scale‐dependent variation in ice cover on the distribution of wintering belted kingfishers Ceryle alcyon
Authors: Kelly Jeffrey F. , Home Beatrice Van
Published: July 2006

Understanding why species react differently to changing environments requires detailed understanding of the factors that regulate distributions within current ranges These types of investigations require spatially and temporally explicit examination of the scales at which a species responds to environmental factors To obtain this type of information, we analyzed the relationship between ice cover and abundance, distribution, and spacing of belted kingfishers Ceryle alcyon during the autumn/winters of 1993–1994 and 1994–1995 Our results indicate that the effects of ice cover on kingfisher populations are complex and scale dependent At a small spatial scale (0 5 km) the abundance of kingfishers was negatively correlated with ice cover, as we expected At a large spatial scale (15 5 km), however, there was no relationship between these variables We argue this contradiction m our results is due to differences in the patchiness of ice cover at these scales In a year with average winter temperatures (1993–1994) the spatial and temporal autocorrelation of ice cover and kingfisher distribution were similar In a warm year (1994–1995), however, we found no such similarity Neighbor distances were shorter during the cold year than during the warm year and shorter during censuses with extensive ice cover than censuses with sparse ice cover We conclude that ice cover is a key factor regulating the distribution and abundance of belted kingfishers in our study area during cold to average years, but that during warm years other factors are likely to be more important Based on these patterns we think that patterns of ice cover may be important in mediating the response of kingfishers to changes in climate
Decomposition and nutrient dynamics of oak Quercus spp. logs after five years of decomposition
Authors: Schowalter T. D. , Zhang Y. L. , Sabin T. E.
Published: July 2006

Decomposition of oak Quercus spp. logs (25 35 cm diameter, 3 m long) was compared among log substrates in Oregon, Minnesota. Kansas and North Carolina during the first five years on the ground. Decomposition of whole logs (weighted by substrate) averaged 0.069 yr‐1 (±0.16 SD). but followed a 2‐exponential model (k = 0.12 yr‐1 year 1 and k = 0.06 yr ‐1 years 2 5), reflecting qualitative differences among log substrates (outer and inner bark, sapwood and heartwood). Rapid loss from bark substrates contributed to the initial rapid decay rate. Sapwood decay rate averaged 0.15 yr‐1 and dominated the second log decay rate. Heartwood lost only 6% mass during the first five years, for an overall decay rate of 0.012 yr‐1 that likely will represent a longer‐term third exponential decay rate.

Carbon loss amounted to ca 5 kg yr‐1 per 170 kg log. Nutrient concentrations generally declined during the first five years, but nitrogen, sulfur, and sodium accumulated in sapwood and heartwood during this period. Sulfur content increased in all substrates and doubled in whole logs during this 5‐yr period. Complex patterns of nutrient content suggest patterns of microbial colonization and nutrient utilization. Polynomial models were developed to describe rates of carbon and nutrient flux in log substrates.
Temporal patterns of age‐class distributions on foothills landscapes in Alberta
Authors: Andison David W.
Published: July 2006

The strategy of managing for “natural” patterns towards ecological sustainability of forests is currently limited lo simple spatial attributes of landscapes. Yet, there is general agreement that landscapes are highly dynamic entities suggesting that temporal patterns may also he important. This study used historical estimates of 20‐yr disturbance rates, and a spatially explicit, stochastic landscape model to create multiple possible landscape mosaic scenes for three different landscapes in the foothills of Alberta, The results were summarized as frequency distributions by age‐class, and the distributions compared to the percentage of area in the current, and the pre‐commercial landscapes. Results indicated that aside from one age‐class in one of the landscapes, both current and pre‐commercial age‐class distributions were well within the historical ranges suggested by the simulations. More generally, the simulations indicated relatively high, but landscape specific, levels of historical temporal variability. This implies that there are patterns to temporal variability which may be captured, quantified, and emulated as alternatives to single age‐class management targets. The research also demonstrates a method of assessing age‐class distributions within the context of historical ranges of distributions.
Biodiversity indicators: graphical techniques, smoothing and searching for what makes relationships work
Authors: Williams p. H.
Published: July 2006

Knowledge of the distribution of biodiversity remains poor. This situation might more readily be resolved If the species richness of certain groups of organisms indicated the richness of other, less well known groups. A spatially explicit exploration of the pattern in the predictive power that one taxon (a potential‘indicator group”) might have for the diversity of another has been performed previously. In this paper we respond to three important points that have been raised. First, we describe an additional graphical technique for visualising spatial aspects of indicator relationships. Second, we examine some of the consequences of smoothing species richness data on observed indicator relationships. Third, we consider some of the factors that may contribute to strong indicator relationships.
Habitat selection and group formation pattern of fallow deer Dama dama in a submediterranean environment
Authors: Apollonio Marco , Focardi Steiamt , Toso Silvano , Nacci Laura
Published: July 2006

We analyzed the patterns of association between sex and age classes of fallow deer Dama dama in addition to the modification of aggregation patterns as a function or the degree of cover in different habitats in a coastal submediterranean environment in Italy. Deer preferred large open grasslands, small clearings, woods and marshes. Habitat selection varied strongly according to sex, and there were also ecological differences among males of different age classes. Adult females were mostly in family groups, with subadults and fawns. These groups were very stable in time and space. On the contrary bachelor herds were unstable social associations, adapting their size to the local degree of cover. In open grasslands males and females sometimes formed mixed groups with group size similarly being adapted to degree of cover. The possibility that random events fully explained fallow deer aggregation patterns was excluded, while the existence of non‐linear mechanisms of aggregation was shown. The persistence of antipredator strategies in this managed population may account for these findings.
The dispersal of a dry‐fruited shrub by red deer in a Mediterranean ecosystem
Authors: Malo Juan E. , Suárez Francisco
Published: July 2006

Seed dispersal of dry‐fruited shrubs has received little attention in Mediterranean areas despite their frequency in the vegetation and the consideration given to the dispersal of fleshy‐fruited shrubs in the area. Red deer faeces has recently been found to contain large numbers of seeds from one of the most common shrubs of this group, gum cistus Cistus ladanifer, although its importance in the reproduction of the species is unknown. This study examines the role of the red deer as an effective disperser of C. ladanifer. For this purpose, we quantify i) the C. ladanifer seed content in red deer dung over a year, ii) the seed shadow generated by the red deer wish their faeces during the same period, and iii) the ability of the dung‐borne seeds to germinate and establish as seedlings under field conditions within five years following excretion. The results reveal an extremely high seed Content of the species in red deer dung (up to 80.5 ± 41.9 germinable seeds g‐1), which is virtually confined to the summer (July–August), when we estimate that a red deer defecates up to 24 000 seeds of the species per day. Furthermore, red deer mainly deposit gum cistus seeds amongst plant formations lacking the species: over the year, red deer excrete <2600 seeds m‐2 in C. ladanifer‐dominated scrub and 7400–8800 seeds m‐2 in other plant formations. Under natural conditions, the dung‐borne seeds have a more sniggered among‐years germination pattern than free seeds in the soil. Though no seedling survived its first summer drought, the survival of seedlings sprouted from dung was significantly longer than that of control seedlings in the first and third years after deposition, and indistinguishable from it the second, fourth and fifth years. This is the first quantification of the importance of red deer to C. ladanifer dispersal and establishment, and suggests that endozoochory by mammalian herbivores can be very valuable for dry‐fruited shrubs in the Mediterranean region.
The evolution of marine insects: phylogenetic, ecological and geographical aspects of species diversity in marine water striders
Authors: Andersen Nils MøSller
Published: July 2006

No other group of insects have been more successful in colonizing marine habitats than water striders and their allies (Heteroptera, Gerromorpha). More than 10% of the 1700 species of gerromorphan bugs are marine. Water striders have colonized the marine environment at least 14 times. The fossil records suggest that marine habitats were invaded by members of the families Veliidae and Gerridae earlier than 20‐30 and 45 million years before present, respectively. Estuaries and mangrove swamps are undoubtedly the ancestral type of habitat, but water striders have diversified further in marine habitats including the surface of the open ocean (sea skaters.Halobates).Except for being obligatorily flightless, marine water striders are structurally very similar to their non‐marine relatives. Physiological and behavioral rather than morphological specializations are likely to have been key innovations in the transition from limnic to marine habitats. The oldest and most species‐rich clades originated in the Indo‐West Pacific region. There are 3.5 times as many species of marine water striders in the Indo‐West Pacific region than in the Atlantic/Caribbean/East Pacific region. This “diversity anomaly” is explained historically by region‐specific differences in the origin and proliferation of clades, in paleoclimate and paleogeography, and in the propensity for dispersal between regions.
Geographic variation and evolution of immunosuppressive genes in a Drosophila parasitoid
Authors: Dupas Stephane , Boscaro Marco
Published: July 2006

Parasitoids that must kill the host to complete their development are expected to evolve towards increased virulence. In some conditions however Leptopilina boulardi loses its ability to counteract the host immune reaction. This trait is determined by major genes. For each host species there is a specific gene for immune suppression by the parasite. Here the geographic variations of the immunosuppressive gene frequencies are investigated in relation to the distribution of the host species. The necessity to deal with host immunity is a major constraint on the host range of L. boulardi. Against Drosophila simulans and D. yakuba. the presence of the immunosuppressive allele is correlated with the presence of the host species in the locality. Against D. melanogaster. the data suggest that this gene is counterselected when the parasite is exposed to numerous host species. This counterselection is explained by the existence of a cost of immunosuppressive genes. Against D. yakuba, this cost was evaluated in population cages as a selective coefficient of s = ‐0.20. The cost differs between the genes. Against D. melanogaster, it was not significant in population cage conditions. The parasitoid invests more in the suppression of the D. yakuba reaction than that of D. melanogaster. This variation of the investment in immunosuppression is discussed within the framework of the adaptive budget theory.
A simple transformation for sets of range sizes
Authors: Williamson Mark , Gaston Kevin. J.
Published: July 2006

Transformation of data to normality may be illuminating and useful statistically. There are two standard families of transformations, power transformations for positive numbers. bounded at the left, and folded transformations for proportions, bounded both at the left and the right. It has been shown that there is no one satisfactory power transformation for range size data. However, such measures are limited to the right as well as the left, and we consider applying folded transformations to them. Seven data sets of range sizes recorded by 10 km squares are studied. Six are British (native and introduced plants, mammals, dragonflies and two breeding bird surveys) the seventh is of Swiss breeding birds. Using these we show that the right hand limit of the distribution can be estimated and the best folded transformation found. In all cases the right hand limit is larger than the range size of the most widespread species and smaller than the notional scope of the survey. In all cases the logit or Hog, the logarithmic folded transformation, is satisfactory: in five cases it is the best. It is well known that abundance is approximately (though not exactly) log‐normally distributed. The relationship of that to our discovery that range size data are approximately logit‐normal is discussed. There is no fully satisfactory explanation for either observation at present.
Testing for nestedness in the terrestrial isopods and snails of Kyklades islands (Aegean archipelago, Greece)
Authors: Sfenthourakis Spyros , Giokas Sinos , Mylonas Moysis
Published: July 2006

Most insular communities exhibit nestedness, with the species assemblages of the more depauperate islands constituting subsets of those of the richer. Several methods for the estimation and evaluation of nestedness have been developed during the last fifteen years. In this paper we use two of the more recent and elaborate methods, namely the ‘temperature’ method of Atmar and Patterson and the ‘departures’ method of Lomolino, in order to investigate patterns of nestedness in the distribution of two well studied and speciose animal groups, terrestrial isopods and land snails, in the Kyklades archipelago (Aegean Sea. Greece) that lies between two continental regions, Significant nestedness is present in both species assemblages and, surprisingly, each method gives almost identical levels of nestedness for the two animal groups. Isolation has been found to be more important in producing nestedness in both groups than area, which does not seem to be an important explanatory factor. However, the role of isolation in this case is better understood under an historical perspective, taking into account the complex palaeogeography of the region and the differential departmentalisation of distinct island groups. Additionally, certain metrics of habitat diversity that were included in the analysis were the best explanatory factors of nestedness, indicating a more complex causal pattern that also involves extinction. Since the two methods used are based on different assumptions and have different scopes, their results do not converge. The ‘temperature’ method finds the maximum possible nestedness in an island sorting which does not necessarily lead to plausible biogeographical explanations, while the ‘departures’ method, although more useful in detecting causality, fails to fully evaluate levels of nestedness. Nevertheless, both methods are valuable tools in the exploration of interesting distributional patterns, when this effort is accompanied by a good understanding of historical, ecological and idiosyncratic properties of each particular data set.
Future prospects and their implications for research on the ecology of freshwater fish
Authors: Larkin P. A.
Published: July 2006

Abstract– Projected world population increases imply demand for an increase of 60 million tonnes on the present world fish production of 100 million tonnes. Capture fisheries are unlikely to yield more because many stocks are already overexploited, there are few remaining unexploited and management shows few signs of redressing problems. Aquaculture is a possible source of the required production, given maintenance of current rates of increase. If this potential is to be realized, the importance of maintaining the quality of freshwater, brackish and coastal marine environments can scarcely be overstated. In a world of rapid change, there is an urgent need for research at all levels of biological and social organization that relate to the ecology of freshwater fish. At the organismic level, genetics, migratory behaviour and physiological ecology will be emphasized. Population genetics research is needed to enlighten controversies concerning the impact of cultural practices and the effects of harvesting natural populations. Greater attention will be given to interactions between species, including fish and their parasites, and the dynamics of multispecies interactions in pond culture and in capture fisheries. Issues of multiple uses of water resources will force research on freshwater fish ecology into broader contexts. The march of discovery in all branches of science will have major implications for freshwater fisheries research. The next few decades will be demanding of the creative energies of young researchers.
Variation in the population density of adult sea‐trout, Salmo trutta, in 67 rivers in England and Wales
Authors: EIIiott J. M.
Published: July 2006

Abstract– Analysis of annual rod and commercial catches of adult seatrout demonstrated strong positive relationships between large‐scale spatial variance (S2s, variation in catches between rivers for each year) and spatial mean density (x̄s, mean catch per year), and also between temporal variance (S2t, variation in catches between years for each river) and temporal mean density (x̄t, mean catch for each river). Both relationships were described by a power function, s2=ax‐b. For spatial variability, there were no significant differences between power functions for both rod and commercial catches from the North West, Welsh and South West regions. As the power b was not significantly different from two, relative spatial variability (measured by coefficients of variation (CV)) was fairly constant between years. Significantly higher values of b were obtained for the Wessex (GM b= 2.233) and North East (GM b=2.824) regions, and therefore the increase in CV with mean annual catch was significant but slight for Wessex rivers and marked for North East rivers. For temporal variability, there were no significant differences between power functions for both rod and commercial catches from all 5 regions and therefore a common power function was fitted to the data from all 67 rivers. As the power b was significantly less than two (GM b= 1.729), relative temporal variability (measured by CV) decreased significantly with increasing mean catch per river. Some limitations and implications of this analysis are discussed. Similar results from different regions for both rod and commercial catches suggest that such data do reflect adult population density, in spite of the different methods used to catch the sea‐trout, variations in fishing effort and failures to report catches. The analysis of temporal variability provides a basis for classifying the major sea‐trout rivers according to their mean annual catch and their relative variability in catches between years (using the CV).
Diel and seasonal utilization of home ranges in a small lake by smallmouth bass (Micropterus dolomieui)
Authors: Savitz J. , Bardygula L. G. , Harder T. , Stuechsli K.
Published: July 2006

Abstract– Diel and seasonal movements of 9 smallmouth bass were monitored by ultrasonic tracking for 1–1.5 years in a small gravel pit lake in northeastern Illinois. Each fish had several home ranges over the study period. Males established home ranges around a nesting site in May and June. During the summer months, smallmouth bass had diurnal, nocturnal, diurnal and nocturnal home ranges. The fish exhibited 2 types of behavior when they were within their home ranges. They were either motionless, which generally occurred on the nocturnal home ranges, or they swam slowly about their home ranges. Rapid directional swimming movements occurred when fish were swimming across the lake or moving between home ranges. The home ranges were transitory. The average size of the reproductive (male) home range was 0.07 hectare; 0.12 hectare for nocturnal home ranges; 0.18 hectare for diurnal home range; and 0.20 for diurnal‐nocturnal home range. Generally, reproductive and nocturnal home ranges were smaller; other types could be as small as these but were often larger. However, there was no significant difference in home range sizes.
A descriptive and experimental study of microhabitat use by young‐of‐the‐year benthic stream fishes
Authors: Greenberg L. A. , Stlles R. A.
Published: July 2006

Abstract– We studied microhabitat use of young‐of‐the‐year (YOY) benthic stream fishes (Cottus, Etheostoma, Percina) using underwater surveys conducted in the Little River of Tennessee, United States. At the upstream site, only Cottus was present and its density was low. Further downstream all genera were present, and YOY density was high and concentrated in deep water habitats. Microhabitat use by the species differed from microhabitat availability, with most species using deep, slow‐moving water with silt‐free, coarse substrates that lacked riverweed, Podostemum ceratophyllum. Despite differences in microhabitat use, there was substantial overlap among species. Because YOY were positively associated with coarse substrates and coarse substrates were uncommon in deep water, we tested their importance by adding cobbles to 3 deep water habitats. We found that YOY benthic fishes colonized areas with cobbles but not sand. After 2 months, however, many of the cobble areas were covered by sediment. These data suggest that YOY fish are substrate‐limited in deep water habitats and that the hydrological properties of pools preclude establishment of permanent instream cover. It is unclear why YOY occur in areas with little instream cover.
Production of Atlantic salmon (Salmo salar) in fresh water and at sea at hgh and low densities
Authors: Chadwick E. M. P. , Randall R. G.
Published: July 2006

A basic management objective is to identify the production capacity of Atlantic salmon in both freshwater and marine environments. Production in the biological sense is the total elaboration of fish biomass over time, and it is a function of fish abundance, growth and survival. In this article, we consider the factors that affect production at low and high stock levels. Using data from New Brunswick (Miramichi and Restigouche Rivers) and Newfoundland (Western Arm Brook), we consider freshwater and marine production of salmon at low and high stock levels. For all life stages, freshwater and marine production are related to initial biomass of the year‐class: thus, it is important to maintain adequate egg deposition. Production at high stock levels is stock‐dependent and mortality is extremely variable, particularly in the marine environment.
Feeding ecology of redside dace,Clinostomus elongatus
Authors: Daniels R. A. , Wisniewski S. J.
Published: July 2006

Abstract–Redside dace,Clinostomus elongatus(Kirtland), from two populations in New York, USA, consumed adult Diptera; over 85% of the prey taken between April and November was in this order. AdultHilaraspp. (Empididae) were the dipterans consumed most frequently; individuals of this genus represented 70% and 60% of the items consumed by fishes from populations in Allcgheny and Hudson River drainages, respectively. Over 98% of the prey consumed by redside dace was in ten insect orders. Adult and larval chironomids and adult trichopterans were the next most frequently consumed prey. Adult chironomids made up 9% of the diet, by number, in both populations. Adult trichopterans accounted for 2–3% of the items taken. Adult empidids were selected by individuals in both populations. The dominance of flying insects in the diet of redside dace is related to their foraging behavior. These data show that adjacent terrestrial environments may be important to some stream‐dwelling organisms.
Growth of age‐0 smallmouth bass (Micropterus dolomieu Lacepéde): interactive effect of temperature, spawning date, and growth autocorrelation
Authors: Sabo M. J. , Orth D. J.
Published: July 2006

Abstract– We examined the growth of individual age‐0 smallmouth bass collected from the North Anna River, Virginia (USA), to determine whether growth during early life stages was most affected by temperature, duration of growing season, growth during previous stages, or whether growth was a stochastic process. Spawning was delayed in 1990, all individuals grew in warm temperatures, and their growth rates during early life stages were not correlated with prevailing temperatures or with growth during previous stages. By the end of the summer, swim‐up date was not correlated with size at the time of collection. In 1991, individuals that swam‐up earliest consistently grew slower (and in colder temperatures) during early life stages. Late swim‐ups (that were exposed to warmer temperatures) grew faster during early life stages but had a shorter growing season. By the middle of the summer, all individuals had an equal chance of being among the largest members of the cohort. The size distribution of the age‐0 cohort at the end of the summer did not differ between years, despite the fact that spawning occurred 3–5 weeks later in 1990 (when temperatures were maximized) than in 1991 (when temperatures were still rising).
Does male‐mating attack in the herbivorous cichlid,Petrochromis polyodon, facilitate the coexistence of congeners?
Authors: Kohda M.
Published: July 2006

Abstract–Coexistence through male‐mating attack in 3 herbivorous cichlids,Petrochromis polyodon, P. trewavasaeandP. famula, was investigated on a shallow rock substratum in Lake Tdnganyika, Africa. All 3 species maintained individual feeding territories that rarely overlapped and were defended against both conspecifics and congenerics. All 3 species took similar foods from rock surfaces. Larger fish were dominant over smaller territorial neighbours irrespective of species. MaleP. polyodon, the largest and most aggressive fish, attacked conspecific males far beyond their feeding territories in terms of mating tactics. Removal experiments suggested that such attacks result in maleP. polyodonterritories being separate. The space betweenP. polyodonfeeding territories can be occupied by congeneric fishes.
The age structure and distribution of Atlantic salmon parr, Salmo salar L., in small tributaries and main stems of the subarctic River Teno, northern Finland
Authors: Erkinaro J.
Published: July 2006

Parr of the Atlantic salmon in subarctic River Teno, northern Finland (70°N, 28°E), are found to migrate to small tributaries that are not spawning areas for the adult salmon. The age distribution of the salmon differs significantly between these brooks and the natal rivers, the parr in the brooks being typically 2–4 years old, whereas those in the main rivers were mostly of age 0–2 years. The older fish were found in the uppermost regions of the brooks. The ratio of salmon to brown trout decreases towards the upper reaches of the brooks. At least some of the young salmon overwinter in the brooks. However, the number of fish and the area inhabited diminished towards the autumn in some occasions. It is suggested that this migratory behavior may be an adaptational phenomenon that could cause variation in survival among young salmon in the River Teno.
Management options for a more complete utilization of the biological fish production in Sri Lankan reservoirs
Authors: Pet J. S. , Gevers G. J. M. , Van Densen W. L. T. , Vijverberg J.
Published: July 2006

Abstract– Stock dynamics of the introduced tilapia Oreochromis mossambicus and co‐occurring indigenous cyprinids were studied in a typical lowland reservoir in Sri Lanka. All species exhibited peaks in reproductive activity during the rainy seasons in November and May. O. mossambicus was estimated to grow to 14 cm in its first year and to 21 cm in its second. A high natural mortality (M was found, both for the cyprinids (M=1.3 yr−1 to 4.7 yr−1 over a range of species) and for O. mossambicus (M= 1.9 yr−l and 1.7 yr−1 for females and males). The fishing mortality (F) of O. mossumbicus, estimated for the length range from 15.0 to 18.5 cm, was 5.5 yr−1 for females and 4.7 yr−1 for males. The total fish biomass was estimated at 1 829 kg/ha, with 128 kg/ha O. mossambicus and 1 098 kg/ha small pelagic cyprinids, mainly Amblypharyngodon melettinus. The total biological fish production was around 5 400 kg/ha/yr, with O. mossambicus and the small pelagic cyprinids accounting for 400 kg/ha/yr and 3 600 kg/ha/yr respectively. The commercial fishery yielded 242 kg/ha/yr (including 70% or 169 kg/ha/yr O. mossambicus), indicating an incomplete utilization of the total biological fish production. It was concluded that there is scope for an approximately 100% increase of the total yield. Reimplementation of a 76 mm minimum mesh size, to prevent overfishing of O. mossambicus, is recommended as a management measure. Additional options are direct exploitation of the untapped resource of small pelagic cyprinids, or indirect exploitation by means of a culture‐based fishery on Lates calcarifer, a controllable predator.
The biological and economic yield from a long‐term eel‐stocking experiment
Authors: Wickström H. , Westin L. , Clevestam P.
Published: July 2006

Abstract– Two almost eel‐free lakes (339 and 299 ha respectively) in southeastern Sweden were stocked with French elvers in the autumn of 1980. The introduced eel stocks were monitored from the time of stocking and onwards using outlet traps equipped with fine‐meshed screens and subsequently by test‐fishing with long‐lines and fyke‐nets. Up to and including the spring run of 1994, more than 5,900 eels or about 2,600 kg were recaptured from one of the lakes, mostly as migrating silver eels. This means a recapture rate of about 11%. In the other lake most recaptures came from fyke‐netting of the yellow eel stock. In this lake only 1.7% have been recaptured up to this point. These differences in yield and recapture rates from the two lakes are discussed in the context of lake productivity, growth rates, sex ratios, sizes of stocked elvers and size at silvering. In cconomic terms, the results from the higher‐yielding lake indicate an excellent rate of profit. After approximately 10 years, the investment (cost of the introduced elvers) was paid back at a lending interest rate of 10%.
The influence of predation risk on habitat selection and food intake by Arctic charr, Salvelinus alpinus (L.)
Authors: Damsgård B. , Ugedal O.
Published: July 2006

Abstract— Large piscivorous fish are assumed to affect habitat selection and food intake of prey fish. To study the effects of cannibalistic Arctic charr, Salvelinus alpinus (L.), on smaller stunted charr, we sampled the prey fish in littoral and pelagic habitats using gill nets, before and shortly after the release of large charr in a small lake (0.52 km2). In the habitats where the risk of predation was highest, the catch per unit effort de creased from 13.3 to 4.8 fish per 100 m2 of gillnet after release of pred ators. The large decrease in numbers of charr < 18 cm corresponded with the predicted vulnerable prey sizes, according to a model based on the size distribution of predators. The occurrence of planktivorous fish and weight‐specific food intake decreased in the high risk habitat and remained unaffected in the low risk habitats. Changes in the food intake of prey fish could not be explained in terms of fish length, indicating that prey fish changed diet when the risk of predation was high.
An accessory lateral line in some New Zealand and Australian galaxiids (Teleostei: Galaxiidae)
Authors: McDowall R. M.
Published: July 2006

Abstract— Many New Zealand and Australian galaxiids have bilateral accessory lateral lines along the dorso‐lateral trunk that consist of widely spaced neuromasts from head to dorsal fin. Dietary studies show that many species feed extensively on terrestrial foods. Some of them are also nocturnally active. The accessory lateral line may assist these fish in locating terrestrial foods at the surface of the water, and perhaps in avoiding predators. Species that lack the accessory lateral line are principally diurnal, mid‐water, shoaling species, or small, slender, cryptic, riffle‐dwellers.
Fatty acid and lipid content of Oreochromis niloticus L. in Ethiopian lakes — dietary effects of phytoplankton
Authors: Zenebe T. , Ahlgren G. , Gustafsson I. ‐B. , Boberg M.
Published: July 2006

Abstract— Herbivorous tilapia fish, Oreochrornis niloticus L. (Cichlidae), collected from five Ethiopian lakes were analyzed for lipid and fatty acid contents of the dorsal muscle using spectrophotometry and gas‐liquid chromatography. The results showed remarkable variation between the lakes in both the lipid and total fatty acid content of the fish, 1.7–21 and 1.6–9.3% of dry weight (DW), respectively. Most fish from Lakes Haiq and Chamo contained higher levels of fat (≥ 10% DW) compared to fish from Lakes Ziway, Langeno and Awassa which contained ≤ 5% DW fat. A total of 28 fatty acids were identified. The saturated fatty acids ranged from 5.3–30 mg. gg−1 DW, monounsaturated Fatty acids from 1.3–30 and polyunsaturated fatty acids from 6.8–29 mg. g−1 DW. The most abundant fatty acids were palmitic acid, docosahexaenoic acid (DHA), oleic acid, stearic acid, palmitoleic acid, arachidonic acid and eicosapentaenoic acid (EPA). EPA and DHA alone amounted to 2.6–15 mg. g−1 DW. The ω3/ω6 ratios ranged from 1.3–7.6 and L. Haiq fish showed the highest ratios, 5.1–7.6, indicating that the fat was of high nutritional quality. The reason for such variation is probably the varied diet available to the fish in the various lakes, This study, along with previous reports, confirms that the phytoplankton flora constituting the diet of O. niloticus varies greatly between the study lakes. The variation in phytoplankton is also reflected by the fatty acid pattern of net samples taken from the study lakes.
Swimming ability and differential use of velocity patches by 0+ cyprinids
Authors: Garner P.
Published: July 2006

Abstract– The ability of chub, dace and roach to resist displacement in a laboratory channel was not only controlled by species‐specific swimming ability, but also by the fishes’ability to locate areas of reduced velocity. Dace were better able to withstand high velocities than roach. Chub were better at locating slow flowing patches than either roach or dace throughout their early development. Only chub larvae shifted towards slower flowing patches as velocity increased. All juveniles shifted to slower flowing patches at high velocities.
Bone tissue reactions to periodontal dressings.
Authors: Haugen Ellen , Majör Ivar A.
Published: July 2006

78 rats weighing 180–200 g were used to assess the bone tissue responses to three periodontal dressings (Coe‐pak, Peripac and Ward's Wondrpak). The dressings were implanted subscutaneously on periosteal covered and denuded bone. Sham operated animals served as controls and a comparison btween the responses produced by the three dressngs were made.

In one series the dressings remained in situ for 3, 7, 14, 30 and 90 days. Osteocyte damage of varying extent was recorded for all materials. Remodelling of the bone surface adjacent to the dressing was observed. Bone resorption was never foud in the gournd defect produced to denude the bone tissue, but repair of the defect by bone formation was observed after long observation periods. This repair was retarded in some animals were Ward's Wondrpak had been implanted.

In another seiries Ward's Waondrpak was implanted against bone for three days, then re‐operated to remove the dressing and the defect allowed to heal for 30 days. The test group exhibited empty bone lacunae and the repair of the defect was retarded or lacking.
Studies of host responses during experimental gingivitis in humans
Authors: Norman M.E. , Baehni P. C. , Tsai C.‐C. , Stoller N. , McArthur W. P. , Taichman N. S.
Published: July 2006

To determine if the early accumulation of plaque in experimental gingivitis is associated with systemic alterations in acute phase serum proteins, immunoglobulins and complement, serial serum specimens were obtained from experimental subjects and matched controls. Therre were no singnificant changes in acute phase reactants (C‐reactive protein, transferrin, alpha‐1‐antitrypsin) or IgG, IgA or IgM. Total hemolytic complement (CH50) and C4 quantitative levels rose significantly in the experimental subjects 21 days after discontinuing oral hygiene, but not in the controls. There were no significant changes in C3 or Factor B levels in either group. Thus, there was no evidence of gross activation of the complement system by either pathway (e.g. consumptive depletion). On the other hand, functional analysis of the sera for spontaneous, complement derived, neutrophil chemotactic activity (SCA) revealed the following: (1) significant elevation in SCA occurred in the experimental subjects 3 and 21 days after discontinuing oral hygiene (compared to the Day 0 baseline value) but did not occur in the controls; (2) the elevated SCA was C5‐dependent; and (3) elevated serum SCA at days 3 and 21 was correlated with the enhancement of plaque mediated lysosomal release from polymorphonuclear leukocytes, incubated with aliquots of these sera. The data suggest that subtle degrees of systemic complement activation occur in experimental gingivitis but are only detected by sensitive, functional assays.
Black‐pigmented Bacteroides from clinically characterized periodontal sites
Authors: Spiegel Carol A. , Hayduk Susan E. , Minah Glenn E. , Krywolap George N.
Published: July 2006

Gingival sites were clinically evaluated on the basis of gingival color and contour, pocket depth, bleeding upon probing and peercent bone loss as measured radiographically. Using anaerobic techniques, subgingival plaque collected from these sites was examined for the presence of the black‐pigmented Bacteroides (BPB). The BPB were identified by biochemical testing and Gram stain morphology. With one exception, only saccharolytic strains (B. melaninogenicus) were found at normal and gingivitis sites, while these and asaccharolytic strains (B. asaccharolyticus) were found at sites exhibiting bone loss.
The response of polymorphonuclear leukocytes to chemotictic stimulation for smokers and non‐smokers
Authors: Kraal J. H. , Kenney E. B.
Published: July 2006

Polymorphonuclear leukocyte (PMN) function may be an important determinant in resistance against periodontitis. Since tobacco smoke may interfere with PMN function, the chemotactic response of PMN to serum and saliva was studied in smokers and nonsmokers and again in the same subjects after all smoked one cigarette. The assay used in this investigation appeared to be sensitive enough to detect some differences between polymorphonuclear leukocyte chemotaxis in some individuals. However, no effect of smoking of the ability of the cells to migrate of the ability of serum or serum or saliva to stimulate such migration was detected.
The effect of divalent cation chelators and magnesium on activation of the alternative complement pathway by Fusobacterium polymorphum (nucleatum)
Authors: Hawley Charles E. , Falkler William A.
Published: July 2006

A complement consumption assay was used to investigate the anti‐complementary activity (AC) of Fusobacerium polymorphum (nucleateum) in guinea pig complement (GPC) which had been treated with the divalent cation chelators ethylamine diamine tetra acetic acid (EDTA) or ethylene glycol tetra acetic acid (EGTA). In the presence of 1 mM EGTA, a cell wall preparation of F. polymorphum reduced the hemolytic complement activity of GPC to essentially the same degree as that observed in the non‐chelated serum controls.hemolysin sensitized sheep erythrocytes (EA). A 1 mM concentraction of EDTA inhibited both the AC activity of F. polymorphum cell wall and the lysisi of EA via the classical pathway. It was also shown that the addition of 1 mM magnesium ion(Mg++)reversed the inhibitory effects of 1 mM EDTA on the lysis EA and on the apparent alternative pathway acitivity displayed by F. polymorphum cell walls. In contrast, the same concentration of Mg++ in the 1 mM EGTA tests did not reverse the EGTA inhibition of the classical pathwaym nor did it markedly augment the alternative pathway. These results indicate that the observed AC activity demonstrated by the cell wall preparation of F. polymorphum did not depend upon a functional classical pathway, but that it porbably occurred exclsively via the alternative complement pathway.
An in vivo study of dietary factors in the aetiology of tooth staining associated with the use of chlorhexidine
Authors: Prayitno A. , Taylor L. , Cadogan S. , Addy M.
Published: July 2006

An in vivo study was carried out to investigate the role of tea, coffe and cigarette smoking upon the staining of teeth associated with the use of chlorhexidine gluconate. Three groups of volunteers, one of which consisted of cigarette smokers, rinsed with a 0.2% chlorhexidine gluconate mouthwash three times a day throughout two 10 day periods. The two non smoking groups were allocated tea and coffe respectively for consumptionduring on 10 day period. The smoking group were allocated coffee during one 10 day period. During the other 10 day periods the volunteers refrained from all hot beverages. A fourth group refrained from all hot bevrages during a 21 day period. The staining which developed on the previously cleaned teeth and tongues of the volnteers at the end of the respective rinsing periods was scored. All volunteers kept a diet record throughout the whole study. The drinking of tea and coffe significantly increased staining of teeth and tongue when compared with not drinking. Staining by tea was significantly worse than staining by coffee. Cigarette smoking appeard to have an additive effect on the staining. Dietary analysis indicated that other factors ar important to development of chlorhexidine staining and some apeared particularly chromogenic in this respect.
Longitudinal therapeutic effects on the periodontal attachment level and pocketdepth in beagle dogs
Authors: Lang N. P. , Morrison E. C. , Löe H. , Ramfjord S. P.
Published: July 2006

Thirteen healthy Beagles, 3 1/2–5 years of age with moderate to advanced periodontal discase received a thorough scaling and prophylasis followed by four weeks of daily tooth cleaning. After one month, each of the fourposterior quadrants of each dog was subjected to one of the following treatments: 1) subgingival curettage, 2) modified Widman flap surgery with root planing, 3) apically repositioned flap and bone surgery for pocket elimination and 4) scaling and root planing as a control. Toothbrushings was carried out daily. In addition, every 14 days the dogs received a rubber cup and pumice prophylaxis throughout the entire length of the study. At the baseline, 1, 6, 12, 24 and 36 months following treatment, oral hygiene and gingival health were scored and the level of periodontal attachment and pocket depth were measured. The results at one Month suggested an increase in attachment levels which was grater after scaling or subgingival curettage than after flap procedures. Up to 36 months, the established attachment levels were maintained for all treatment groups and no significant difference was found between any of the treatments and the scaled controls. However, in advanced periodontal lesion attachment levels were not maintaned with scaling alone.

The present study has shown that the more conservative approaches to the treatment of periodontal disease such as subgingival curettage and Widman flap surgery may be as effective in maintaining clincal attachment levels as elaborate surgical procedures involving osteoectomy.
A theoretical consideration of the periodontal membrane as a collagenous thxotropic system and ist relationship to tooth eruption
Authors: Kardos Thomas B. , Simpson Leslie O.
Published: July 2006

It is proposed that the physiological behaviour of the dental follicle and perodontal membrane is explicable, on theoretical grounds, as having the characteristics fo a thixotropic gel. If the collagen “fibres” of soft connective tissue as seen in fixed specimens area accepted as the static appearance of a dynamic system, i.e. artefacts of fixation, then the physiologicla behaviour of theis collagenous tissue and the eruption of teeth may be explained in simple terms by changes in the viscosity of this biological system.
Experimental periodontitis induced in rats by streptococcal cell wall fragments
Authors: Hunter Neil , Schwab John H. , Simpson David M.
Published: July 2006

Bacterial cell wall fragments, consisting of peptidoglycan and associated polysaccharide of teichoic acid polymers were prepared from a group A streptococcus, a group D streptococcus, two Streptococcus mitis strains and Strepococcus sanguis. Injection of cell walls into rat gingival tissues resulted in self‐limiting inflammatory lesions that reached a peak in 2 to 3 days and resolved by 4 to 7 days/ An early polymorphonuclear leukocyte response was replaced by a mononuclear infiltrate characterized by a predominance of macrophages. Lymphocytes and plasma cells were not a common feature, even in animals given repeated injection of cell walls into the same area. A wide range of changes was seen in the alveolar bone, including loss of the periosteum with disappearance of osteoblasts, osteoclastic bone resorption, hyperplasia of the periostum with apparent osteoblastic activity, and osteoid formation. Osteoclast‐associated bone resrption was commonly seen on the periodontal ligament aspect of the alveolar bone and less frequently on the periosteal surface. Neonatal thymectomy did not alter the response, and respeated injections did not increase the severity of the reactions.