bluuebunny/crossref_metadata_2025 huggingface dataset:
Plate 470. Philadelphus maculatus
Authors: Rix Martyn
Published: December 2003

Philadelphus maculatus (Hitch.) Hu is illustrated from material collected near the type locality in north‐eastern Mexico, and a full description is provided. Related species in the P. microphyllus complex to which P. maculatus belongs, are reviewed, and its cultivation is discussed.
Plate 471. Aquilegia fragrans
Authors: Mathew Brian , Sinnott Mike
Published: December 2003

The Himalayan Aquilegia fragrans Benth. (Ranunculaceae) is illustrated. A full description of the species is provided, its taxonomy and relationships are discussed and recommendations are made for its successful cultivation.
Book Review
Authors: Clennett Chris
Published: December 2003

Book reviewed in this article:

Peter F. Yeo, Hardy Geraniums: New Edition
Consistent Estimation of the Structural Distribution Function
Authors: Klaassen Chris A. J. , Mnatsakanov Robert M.
Published: December 2003

Motivated by problems in linguistics we consider a multinomial random vector for which the number of cells N is not much smaller than the sum of the cell frequencies, i.e. the sample size n. The distribution function of the uniform distribution on the set of all cell probabilities multiplied by N is called the structural distribution function of the cell probabilities. Conditions are given that guarantee that the structural distribution function can be estimated consistently as n increases indefinitely although n/N does not. The natural estimator is inconsistent and we prove consistency of essentially two alternative estimators.
Effect of feedback signal and psychological characteristics on blood pressure self‐manipulation capability
Authors: Lal Saroj K.L. , Henderson Robyn J. , Carter Norman , Bath Andrew , Hart Michael G. , Langeluddecke Pauline , Hunyor Stephen N.
Published: December 2003

Blood pressure presentation mode and personality are likely to influence biofeedback outcome. Thirty‐six normotensive subjects were randomly assigned to visual or auditory continuous systolic feedback. “Distracting speech” and “broad band noise” were also superimposed and the effect on the biofeedback response was investigated. Psychological influence was also investigated. Systolic pressure reductions of 4 ± 4.3 mmHg (visual, p= .04) and 5 ± 5.5 mmHg (visual + auditory, p= .03) were achieved compared with auditory feedback (2 ± 4.7 mmHg), which was less effective. The addition of noise or speech had no effect on the systolic response, but speech adversely affected diastolic reduction (p= .04). Mood (p= .003) was associated with systolic lowering, whereas increased trait anxiety (p= .06) and expectation (p= .03) had trends for opposite effects. Increased anger‐hostility, state‐anxiety, and expectation (p= .06) had links with systolic raising capability. We conclude that feedback modality and psychological characteristics have implications for studies investigating blood pressure manipulation capability.
Scaling of movement velocity: A measure of neuromotor retardation in individuals with psychopathology
Authors: Caligiuri Michael P. , Lohr James B. , Ruck Robert K.
Published: December 2003

The study of motor slowness based on observational methods has limitations. Whether motor retardation has a psychomotor or neuromotor basis is unclear because psychiatric and motor symptoms overlap. Observational methods lack the precision necessary to distinguish cognitive from motor processes. For the present study, we used an objective measure of neuromotor dysfunction to quantify the extent to which an individual programs movement velocity in anticipation of increasing target distance. Persons with Parkinson's disease (PD) or functional psychosis were studied with a group of healthy comparison subjects. Results indicated that the slope of the linear function relating velocity to distance was abnormal in the PD group and in approximately half of the psychosis group. Analyses revealed the measure to have high specificity and sensitivity. Weak correlations between velocity scaling and psychopathology support the neuromotor basis of the measure. We conclude that this measure of velocity scaling is relatively uninfluenced by cognitive factors that may underlie psychomotor retardation.
Brain Asymmetry. Edited by Richard J. Davidson and Kenneth Hugdahl. Cambridge, MA: MIT Press, 1995.
Authors: Compton Rebecca J. , Heller Wendy
Published: December 2003

In an era characterized by an increasing bias in favor of molecular paradigms in neuroscience, this ambitious volume attests to the fundamental value of conceptualizing neural systems on a more molar and integrative level. Researchers in the area of brain asymmetry are in a unique position to make connections between brain functioning and behavioral functioning and are using sophisticated behavioral and clinical methods and advanced electrophysiological and hemodynamic techniques to do so. Chapters in this book elucidate complex cognitive and emotional phenomena from multifaceted perspectives ranging from the biochemical to the sociocultural. Indeed, the editors consider the study of brain asymmetry, with its ability to address various levels of analysis with diverse methodological and conceptual approaches, as an exemplary paradigm for future brain/behavior research.
Coping with variability and change: Floods and droughts
Authors: Kundzewicz Zbigniew W. , Budhakooncharoen Saisunee , Bronstert Axel , Hoff Holger , Lettenmaier Dennis , Menzel Lucas , Schulze Roland
Published: December 2003

Floods and droughts are natural phenomena for which the risks of occurrence are likely to continue to grow. Increasing levels of exposure and insufficient adaptive capacity are among the factors responsible for the rising vulnerability. The former is conditioned by anthropopressure (e.g., economic development of flood–prone areas) and adverse effects of climate change; scenarios for future climates indicate the possibility of amplified water–related extremes. This article presents the current situation of coping with extreme hydrological events within the pressure–state–response framework. Among promising response strategies, the role of forecast and warning, and of watershed management are reviewed. Sample success stories and lessons learnt related to hydrological extremes are given and policy implications discussed.
Combating drought through preparedness
Authors: Wilhite Donald A.
Published: December 2003

Drought is a complex, slow–onset phenomenon that affects more people than any other natural hazard and results in serious economic, social, and environmental impacts. Although drought affects virtually all climatic regimes and has significant consequences in both developed and developing countries, its impacts are especially serious in developing countries where dryland agriculture predominates.

The impacts of drought are often an indicator of unsustainable land and water management practices, and drought assistance or relief provided by governments and donors encourages land managers and others to continue these practices. This often results in a greater dependence on government and a decline in self–reliance. Moving from crisis to risk management will require the adoption of a new paradigm for land managers, governments, international and regional development organizations, and non–governmental organizations. This approach emphasizes preparedness, mitigation, and improved early warning systems (EWS) over emergency response and assistance measures.

Article 10 of the Convention to Combat Desertification states that national action programmes should be established to identify the factors contributing to desertification and practical measures necessary to combat desertification and mitigate the effects of drought. In the past 10 years, there has been considerable recognition by governments of the need to develop drought preparedness plans and policies to reduce the impacts of drought. Unfortunately, progress in drought preparedness during the last decade has been slow because most nations lack the institutional capacity and human and financial resources necessary to develop comprehensive drought plans and policies. Recent commitments by governments and international organizations and new drought monitoring technologies and planning and mitigation methodologies are cause for optimism. The challenge is the implementation of these new technologies and methodologies. It is critical for governments that possess this experience to share it with others through regional and global networks. One way to accomplish this goal is to create a network of regional networks on drought preparedness to expedite the adoption of drought preparedness tools to lessen the hardships associated with severe and extended drought episodes.
Foreign direct investment and institutional obstacles: The case of Russian forestry
Authors: Nilsson Mats , Söderholm Patrik
Published: December 2003

This article examines why, in spite of vast forest resources, Russia has been unable to attract foreign investors into its forest industry. A survey of 32 influential Western European forest companies indicates that purely economic factors, such as labour or raw material costs, are not the main reasons these companies refrain from investing. Instead, the companies identify a number of institutional factors: ambiguous legal systems; difficulties in negotiating with local authorities; unfair tax enforcement; and general political instability as the main impediments to FDI in the sector. These factors have led many companies to abandon previously considered investments in Russia, and also to terminate existing business relationships with Russian partners. The survey results also indicate that, while many investors in forestry were attracted by the potential for a growing Russian market in the early days of the transition period, they have become more and more aware of the many institutional obstacles challenging growth in the sector. The article concludes, therefore, that FDI in the Russian forestry sector is likely to remain low until a fundamental change takes place in the legal and political systems.
Small–scale mining in South Africa: Past, present and future
Authors: Mutemeri Nellie , Petersen Francis W.
Published: December 2003

Mining is an important part of the South African economy and has been the driver of much of the economic development of the country. However, the small–scale mining subsector still has to realise its full potential.

A small–scale mine has been defined as a mining activity employing less than 50 people and with an annual turnover of less than 7.5 million Rand and includes artisanal mines. Small–scale miners are involved in many commodities but there appears to be a bias towards gold, diamonds and quarrying for construction materials, including brickclays. Small–scale mining is regulated by the same legislation (i.e., for the environment, labour, mineral rights, exploration and mining permitting, and skills development) as large–scale mining, though compliance is low, particularly where artisanal mining in concerned.

The effective participation of small–scale miners in the mining sector is hampered by their lack of skills, i.e., technical, business and management, and their limited access to mineral deposits, capital and markets. Some of these hindrances have been inherited from the imbalances of the colonial and apartheid eras and continue to act as barriers, making entrance to the industry difficult. For those who have entered the industry out of desperation, as is the case with most artisanal miners, their activities result in negative impacts evident in the inefficient, unsafe and environmentally unfriendly operations.

With the advent of the new political dispensation in South Africa, a new era is dawning for the country’s small–scale mining subsector. This has resulted in a change of attitude and new government policies which have led to special programmes being put in place to promote the subsector. Intervention strategies for the support of small–scale mining (some of which are already in operation) include programmes for kickstarting mineral beneficiation and value–addition projects, development of appropriate technologies and skills and technology transfer. Proponents of small–scale mining see a well–regulated industry as being the cornerstone of future rural economic development, particularly for previously disadvantaged communities in the poverty nodes.
11. A Liang-Zeger Method for Modeling Dyadic Interdependence in the Analysis of Social Networks
Authors: Yamaguchi Kazuo
Published: December 2003

This article introduces a modified Liang-Zeger method for the estimation of the variance-covariance matrix of parameter estimates for models of social network data that include variables to characterize dyadic nonindependence. While the pseudolikelihood method has been used recently to estimate parameters for such models, the issue of estimating their standard errors, or the variance-covariance matrix more generally, has been neglected. This article addresses the issue by proposing a method for such estimation and also presents an illustrative application of the method to empirical social network data.
2. An Assessment of Alternative Measures of Time Use
Authors: Juster F. Thomas , Ono Hiromi , Stafford Frank P.
Published: December 2003

Although time use has received much attention by social scientists as an index of resource allocation and social relations across groups, only a few studies have carefully assessed the relative strengths and weaknesses of the existing methods of measuring time use: time diary (TD), stylized (S) respondent report, and experiential sampling method (ESM). We note the varying degree of biases that arise in part from the extent of detail in the information collected by the three methods. Using findings from our analysis of the structure of these methods, we hypothesize that there are empirical exceptions to previously reported common findings that TD provides less biased information on time use than does S—namely (a) when labor market workers report their time spent on labor market work, and (b) when the historical trend in time, rather than the absolute level, is studied. Empirical results confirm our prediction and show that, among individuals who work regularly, TD and S estimates of labor market work hours reported by the same persons correspond closely to one another. In addition, when assessing historical trends, TD and S values correspond closely to one another, although TDs yield some inexplicable deviations from the trend even when the sample and the codes are carefully standardized. We also provide notes on a strategy of standardization for diary codes that are distinct across historical or national contexts.
3. Measuring the Frequency of Regular Behaviors: Comparing the “Typical Week” to the “Past Week”
Authors: Chang LinChiat , Krosnick Jon A.
Published: December 2003

Social scientists often measure the frequency with which people perform behaviors executed regularly throughout their daily lives, but there is no standard approach to this measurement task: some investigators have asked respondents about their behavior during a “usual” or “typical” day, week, or month, whereas others sought to describe the same sorts of behavior patterns by asking about the most recent day, week, or month. This paper compares the validity of “typical” week and “past” week reports for assessing habitual behavior patterns using data from the 1989 National Election Study Pilot, in which respondents were randomly assigned to report TV news program and newspaper exposure during either a typical week or the past week. The predictive validity of the measures was assessed using objective tests of current events knowledge and identification of political figures, as well as self-assessments of political knowledge. The typical week questions consistently manifested superior predictive validity, especially among the most educated respondents.
5. Modeling Multiple Failure Time Data: A Survey of Variance-Corrected Proportional Hazards Models with Empirical Applications to Arrest Data
Authors: Ezell Michael E. , Land Kenneth C. , Cohen Lawrence E.
Published: December 2003

Proportional hazards models are powerful methods for the analysis of dynamic social processes and are widely used in sociology to estimate the effects of covariates on event timing (e.g., time to arrest, birth, marriage). The proper statistical modeling of failure time data is an important analytical issue in sociology, but to date the field has largely neglected the application of these models to multiple failure time data in which the conventional assumption of the independence of failure times is not tenable. This paper critically describes a class of models known as variance-corrected proportional hazards models that have been developed by statisticians to take into account a lack of independence among failure times. The purpose is to provide an exposition and comparison for sociologists of several such models and associated methods for handling multiple failure time data that can be readily estimated in commonly available statistical software packages. We pay special attention to the data requirements necessary for estimation of the models. The paper concludes with an illustrative application of the models to analyze the arrest patterns of a sample of California Youth Authority parolees.
Training Systems and Labor Mobility: A Comparison between Germany and Sweden*
Authors: Korpi Tomas , Mertens Antje
Published: December 2003

The mobility effect of general and specific training is a key issue in the debate on the design of educational systems. Using data from two retrospective life‐history surveys, we compare general school‐based vocational training and specific apprenticeship training with regard to inter‐firm, inter‐occupational and inter‐industrial mobility. The results show that workers with school‐based degrees display greater occupational mobility, while no difference in firm and industrial mobility can be discerned. This suggests that apprenticeships do not eliminate job search at labor market entry, that they reduce occupational mobility, and that responsiveness to structural change is similar under both training systems.
How Rigid are Nominal Wages? Evidence and Implications for Germany*
Authors: Knoppik Christoph , Beissinger Thomas
Published: December 2003

Many recent attempts to find evidence on downward nominal wage rigidity in micro data have suffered from problems such as composition bias and the effects of measurement error. In this paper, a model of proportional downward nominal wage rigidity is developed which avoids these problems by taking into account the determinants of wage changes and the measurement process that leads to observable earnings changes. We find a high degree of downward nominal wage rigidity in German micro data. Its real implications for individual expected wage growth, the aggregate wage level and equilibrium unemployment have marked effects for rates of inflation lower than 3 percent.
Nocturnal autumn bird migration at Falsterbo, South Sweden
Authors: Zehnder Susanna , Åkesson Susanne , Liechti Felix , Bruderer Bruno
Published: December 2003

We investigated the patterns of nocturnal bird migration in autumn 1998 at a coastal site on the Falsterbo peninsula in south‐western Sweden, by means of a passive infrared device. In total 17 411 flight paths, including track direction and altitude, of migrating birds were recorded for 68 nights from August to October. Mean migratory traffic rate per night varied between 6 and 6618 birds km−1 h−1, with an average of 1319 birds km−1 h−1. Migration at Falsterbo showed a similar seasonal pattern to that reported for central Europe, with pronounced peaks of migration and intermittent periods with relatively low migratory intensities. Weather factors explained two thirds of the variance in the intensity of bird migration. During nights with intense migration, associated with weak winds, the mean track direction was close to that in central western Europe (225°). Birds usually maintained a constant heading independent of wind directions and, in consequence, were drifted by the wind. The mean orientation clearly differed from that of the nearest coastline, suggesting that the birds did not use the topography below to compensate for wind drift.
Immunity, growth and begging behaviour of nestling Barn Swallows Hirundo rustica in relation to hatching order
Authors: Saino Nicola , Incagli Michele , Martinelli Roberta , Ambrosini Roberto , Møller Anders Pape
Published: December 2003

In altricial birds, asynchronous hatching often results in a size hierarchy among nestlings. However, laying order and hatching order may affect components of offspring condition differentially. Since parasites can have a heavy impact on their hosts, strategies may have evolved that allow parents and offspring to allocate critical resources to immunity depending on hatching order. In this study of the Barn Swallow Hirundo rustica we (1) analyse the relationship between laying and hatching order of eggs, (2) compare morphological, serological and immunological traits between early‐ and late‐hatched siblings, and (3) compare the begging behaviour of early‐ and late‐hatched nestlings. Hatching order strictly reflected laying order. Late‐hatched chicks begged more for food but had smaller body mass throughout the nestling period. Immunoglobulin concentration and intensity of T cell‐mediated immunity were larger in late‐hatched nestlings. Large concentration of immunoglobulins in late‐hatched nestlings may reflect transfer of immunity from the mother via the egg. Alternatively, in association with larger T cell‐mediated immunity, immunoglobulin production may indicate larger investment in immunity by late‐hatched nestlings. Laying order and hatching order may therefore affect components of nestling condition differentially.
The growth bars on tail feathers in the male Styan's Grasshopper Warbler may indicate quality
Authors: Takaki Yoshihide , Eguchi Kazuhiro , Nagata Hisashi
Published: December 2003

We propose that growth bar size may indicate the quality of individuals in Styan's Grasshopper Warblers Locustella pleskei. Positive correlations of an individual's standardized growth bar width between years showed that some individuals of both sexes were usually in better condition than others. The survival rate of males with wider growth bars was higher than that of other males. These survivors might have survived better because of a better body condition. We also examined the relationships between growth bar width and reproductive parameters (arrival date, pairing date and reproductive success). Males with wider growth bars arrived earlier, acquired a mate earlier and achieved higher total reproductive success by breeding twice. In females, growth bar width was correlated with reproductive parameters (arrival date, pairing date and total reproductive success), but not with survival. These results suggest that males with wider growth bars were of higher quality than those with narrower bars. The contrasting results for the two sexes may be explained by differences in their breeding tactics.
Effects of testosterone implants on pair behaviour during incubation in the Yellow‐legged Gull Larus cachinnans
Authors: Alonso‐Alvarez Carlos
Published: December 2003

The Yellow‐legged Gull Larus cachinnans is monogamous with bi‐parental incubation. In this study, the effects of high levels of plasma testosterone in male Yellow‐legged Gulls during the incubation period were analysed. Free‐living male gulls were implanted with testosterone (T‐males), and their sexual behaviour within the pair was observed and compared with that of control pairs. Egg temperatures, length of incubation and hatching success were also analysed. T‐males and their mates displayed more sexual behaviour than the controls. T‐males engaged in mounting behaviour with their mates, whereas control males did not. Proportionally less time was spent incubating (in relation to time present in the colony) by T‐males than control males. However, the mates of T‐males did not spend more time incubating than control females to compensate for male neglect, although they did spend more time on the territory. Egg temperature in T‐male nests was significantly lower than in control nests, but no significant difference in the length of incubation or hatching success between the two groups was found. In birds, the effects of high testosterone levels on male behaviour during incubation have only been analysed in a polyandrous species whose females usually do not contribute to incubation. The present results thus suggest that those males of a monogamous species with bi‐parental incubation that sustain high testosterone levels after laying, thus reducing their contributions to incubation, will be confronted with a lack of compensation from their mates during incubation. Finally, this lack of female compensation seems to be mediated by behavioural interactions with the male rather than by her absence from the colony.
The distribution of extra‐pair young within and among broods – a technique to calculate deviations from randomness
Authors: Neuhäuser Markus , Forstmeier Wolfgang , Bretz Frank
Published: December 2003

Molecular paternity tests show that extra‐pair fertilizations are common in many socially monogamous bird species. However, the question of why females often seek extra‐pair copulations is still controversial. Competing alternative explanations differ in their predictions on how extra‐pair young should be distributed within and among broods. Analysing these distributions may therefore help to resolve this controversy. In several species broods without extra‐pair young and those with total or nearly total extra‐pair paternity have been claimed to be over‐represented. Consequently, extra‐pair nestlings would be distributed non‐randomly among nests. To compute expected frequencies (i.e. the patterns of random distribution) the Poisson distribution has frequently been used. However, the Poisson distribution is not appropriate for two reasons. (1) Impossible configurations can receive positive probabilities. (2) The Poisson distribution approaches randomness only if extra‐pair fertilizations are events of low probability, which often is not the case. We show how randomness can be computed appropriately by using the multivariate hypergeometric distribution. Re‐analysing published data on distributions of extra‐pair young, we show that the result that there are more broods containing either none or many extra‐pair young than expected by chance is even more pronounced than previously thought.
Feather mite loads influenced by salt exposure, age and reproductive stage in the Seychelles Warbler Acrocephalus sechellensis
Authors: Dowling Damian K. , Richardson David S. , Blaakmeer Karen , Komdeur Jan
Published: December 2003

Many factors may affect symbiont distributions within host populations. Intrinsic factors, such as genotype, body condition and age may account for variations in symbiont loads between individuals . However, abiotic factors may also contribute to variations. We investigated correlates of variation in the number of feather mites, Trouessartia sp. (Trouessartiidae), per individual in the Seychelles Warbler Acrocephalus sechellensis on Cousin Island. Warblers from territories exposed to high levels of salt spray had lower feather mite loads than warblers from territories unaffected by salt spray, and juveniles had higher mite loads than adults. When the effects of salt spray were controlled for statistically, incubating birds had lower mite loads than birds in other stages of reproduction. Thus, an extrinsic and two intrinsic factors contribute to predicting feather mite loads.
Duration of primary moult affects primary quality in Grey Plovers Pluvialis squatarola
Authors: Serra Lorenzo
Published: December 2003

Feather wear is the natural degradation and breakage of feather structure during the interval between moults. Different rates of feather wear have been observed for primaries of free‐living populations of several species of passerines and waders, and this variability has been linked to different concentrations of melanins. In this study primary moult duration explained 59% of the variation in annual rates of primary abrasion (percentage wing length loss) of seven Grey Plover wintering populations, while migration distance explained 14%. The analysis suggests that primary moult duration plays a key role in determining primary durability and hence primary quality. Long distance migrants might evolve more durable primaries, despite the higher predation risks and energetic costs of a prolonged moult. Partial or complete pre‐breeding primary moults of first‐year waders and complete biannual moults of some passerines might have evolved under selective forces favouring migration with unabraded primaries.
Differential investment in the Banggai cardinalfish: can females adjust egg size close to egg maturation to match the attractiveness of a new partner?
Authors: Kolm N. , Olsson J.
Published: December 2003

To test whether females can change their egg investment according to the different attractiveness ( i.e. size as measured by standard length,Ls) of a new mate after eggs have already matured in response to an earlier mate, female Banggai cardinalfishPterapogon kauderniwere first allowed to produce eggs for small (unattractive) or large (attractive) males. Then, when spawning was initiated, but prior to actual spawning, their partner was switched to either a significantly larger or a significantly smaller partner, respectively. A strong positive correlation between egg size and days until spawning with the second male was found for the females initially paired to a small and then a large male. Within a few days, these females apparently increased their egg size to match the attractiveness of their new male. No correlation between days until spawning and egg size in females initially paired to a large and then a small male, however was found, so apparently females were unable to adjust egg size in response to a decrease in mate attractiveness. Consequently, it is suggested that females can increase their egg size investment even after the onset of egg maturation and that this change can be quite rapid.
Environmental enrichment and prior experience of live prey improve foraging behaviour in hatchery‐reared Atlantic salmon
Authors: Brown C. , Davidson T. , Laland K.
Published: December 2003

Atlantic salmon salmo salar L. parr were reared for 3 months under standard hatchery conditions or in a structurally enriched tank (containing plants, rocks and novel objects). Half of each of these fish had prior exposure to live prey in the form of live bloodworm while the other half were fed hatchery‐pellets. After 12 days all fish were tested on a novel live prey item (brine shrimp). A significant interaction between the two factors (prior exposure to live prey and rearing condition) revealed that foraging performance was only enhanced in fish that had been reared in a complex environment and exposed to live prey. It appears that the ability to generalize from one live prey type to another is only enhanced in fish that had been reared in an enriched environment. The findings support the assertion that the provision of enriched environments in combination with exposure to live prey prior to release may significantly improve the post‐release survival rates of hatchery‐reared fishes. As both the environmental enrichment and the prior foraging experience procedures were comparatively simple, the provision of such pre‐release experiences are likely to prove cost effective to hatcheries.
Settlement and habitat use by juvenile pike in early winter
Authors: Hawkins L. A. , Armstrong J. D. , Magurran A. E.
Published: December 2003

The spatial distribution and social behaviour of young‐of‐the‐year pike Esox lucius was investigated in early winter. Reed beds were selected in the early exploration phase but thereafter, pike congregated in the pool habitat. A significant increase in pool occupancy combined with a decrease in reed bed occupancy and movement indicated settlement within 3 days. There was no evidence of territoriality, which has been reported previously in adult pike: indeed, inter‐individual spacing was consistent with social grouping rather than territory defence. The strong preference for reed cover among juveniles reported in other studies that were undertaken during summer was not observed here. Among‐individual variation in exploratory behaviour was observed but this was not related to activity levels or habitat use.
The function of mate choice in sticklebacks: optimizing Mhc genetics*
Authors: Milinski M.
Published: December 2003

Sexual reproduction is an evolutionary ‘puzzle’. A sexual female ‘throws away’ half of her genes (during meiosis), and ‘fills up’ what she lost with genes from a male. Thus, sexual reproduction can only be successful if the offspring with the new mixture of genes should be more than twice as fit as if she had just made a copy of herself. A challenging hypothesis assumes that infectious diseases select for females that reshuffle the immune genes for their offspring in each generation. The required increase in quality could be achieved by females selectively ‘smelling out’ suitable immune‐genes (i.e. Mhc alleles) in potential partners, which, in combination with the female's genes, offer optimal resistance against quickly changing infectious diseases. It was found that most three spined sticklebacks Gasterosteus aculeatus in natural populations around Plön, Germany, had intermediate instead of maximal numbers of different Mhc class IIB alleles. Furthermore, fish with an intermediate number of different Mhc alleles were infected with the lowest number of both parasite species and parasites per species. This suggests that Mhc heterozygosity was optimized instead of maximized. Can this immunogenetic optimum be achieved through female choice? In a flow channel design that allowed the detection of olfactory signals only, it was found that female three‐spined sticklebacks that were ready to spawn preferred males as mates that in combination with their Mhc alleles would allow the production of offspring with the optimal number of Mhc alleles. Thus, mate choice in three‐spined sticklebacks could have the two‐fold advantage over asexual reproduction that is required to maintain sexual reproduction. The interaction of olfactory with visual signals in three‐spined stickleback mate choice is discussed. The three‐spined stickleback is a suitable model organism for studying the evolution of sexual reproduction in relation to optimizing offspring immune genetics although other fishes may be as suitable.
How landscapes affect the evolution of dispersal behaviour in reef fishes: results from an individual‐based model
Authors: Dytham C.
Published: December 2003

The vast majority of tropical reef fishes have a sedentary adult phase and pelagic larval phase that is potentially highly dispersive. Dispersal may be favoured by a wide range of factors including the arrangement of suitable habitat in space. In this paper the dispersal strategy of individuals is followed and allowed to evolve in a simplified model of three different landscapes: an enclosed sea, an open archipelago and a barrier reef. The three landscapes have very different characteristics, but all have similar spatial clumping of reef habitat. In all landscapes, as minimum time to settlement increases, evolved movement strategy also increases and longer settlement windows favour dispersal. In the archipelago movement is not maximized until the minimum pelagic duration is longer than in the other landscapes. The model predicts that, given the same pelagic duration, species from enclosed seas should have more dispersive behaviours than those from open archipelagos, because of the density of habitat and the aggregation of habitat in space affect the likelihood of larvae finding suitable habitat for settlement.
Effects of fish size, time‐to‐fatigue and turbulence on swimming performance: a case study of Galaxias maculatus
Authors: Nikora V. I. , Aberle J. , Biggs B. J. F. , Jowett I. G. , Sykes J. R. E.
Published: December 2003

A simple relationship for the inanga Galaxias maculatus swimming velocity is suggested and tested in low and high turbulence channels. The relationship connects the swimming velocity with fish Reynolds and Froude numbers and can be used in both ecological analysis (e.g. habitat requirements) and management strategies (e.g. fishways design). Contrary to some previous studies and intuition, effects of turbulence on swimming performance appeared to be negligible. The most likely explanation for this result relates to mechanics of fish–turbulence interactions that may be dependent on both the turbulence scales and energy. The data suggest that future studies of turbulence effects on fish behaviour should involve, in addition to turbulence energetics, consideration of fish dimensions in relation to the spectrum of turbulence scales.
A computer‐activated food delivery system for dispensing natural prey items among complex arrays of patches
Authors: Maclean A. , Miles M. S. , Armstrong J. D.
Published: December 2003

Experimental studies of the foraging ecology of drift‐feeding fishes have been limited in scope because of the lack of systems for dispensing suitable prey items to a number of patches with complex and controlled spatio‐temporal patterns of delivery rate. Here, tests are reported of a computer‐controlled feeding system that performs this requirement with considerable flexibility.
Influence of salinity and ovarian fluid on sperm motility in the fifteen‐spined stickleback
Authors: Elofsson H. , Van look K. , Borg B. , Mayer I.
Published: December 2003

Sperm motility of the fifteen‐spined stickleback Spinachia spinachia was investigated in different salinities, with or without the addition of ovarian fluid (25%). Sperm velocity, longevity, linearity and percentage of motile sperm were analysed with the aid of computer‐assisted sperm analysis (CASA). The sperm were found to have the longest duration of motility in sea water (60–90 min in salinities 20 and 30), shorter in brackish water (15–30 min in salinities 5·5 and 10) and were immotile in fresh water. The presence of ovarian fluid did not influence any sperm motility variable in any tested salinity.
Biomass size distributions as a tool for characterizing lake fish communities
Authors: De Leeuw J. J. , Nagelkerke L. A. J. , Van Densen W. L. T. , Holmgren K. , Jansen P. A. , Vijverberg J.
Published: December 2003

Biomass size distributions (BSDs) can be useful tools to (1) summarize complex information about fish community structure in a condensed graphical form, facilitating the characterization of freshwater fish communities, (2) compare the position of fish communities along environmental gradients and (3) elucidate major trophic interactions in freshwater fish communities. Biomass size distributions are presented by taxonomic and trophic group, for a selection of fish communities from 35 Scandinavian and eight Dutch lakes. They were used for the analysis of taxonomic and trophic shifts in the fish communities along a large environmental gradient, with productivity (expressed as total phosphorus concentration, TP) as its most important component. Regression analysis of fish community variables (such as proportion of cyprinids, or biomass of benthivores) were consistent with the semi‐quantitative conclusions drawn from BSDs, regarding taxonomic and trophic shifts with changes in TP in both Scandinavian and Dutch lakes, especially an increase in the amount and size of benthivorous fishes with increasing TP‐levels. In addition, differences in mortality and growth rates were shown to partly explain differences in BSDs. Biomass size distributions thus provide an integrative tool for qualitative and quantitative comparisons among fish communities.
Feeding pattern and the visual light environment in myctophid fish larvae
Authors: Sabatés A. , Bozzano A. , Vallvey I.
Published: December 2003

The trophic spectrum and feeding pattern of two myctophid larvae, Benthosema glaciale and Myctophum punctatum, were analysed in relation to changes in daily light intensity. The larvae of both species live relatively deep, occurring in the first 100 m, though distribution of M. punctatum extends to 150 m depth. The present study, carried out in the western Mediterranean (Alboran Sea), indicated that the larvae of the two species exhibit different foraging strategies. Both started to feed at dawn, but while feeding of M. punctatum was high at dawn and dusk, the feeding of B. glaciale remained high throughout the day. The light intensity profiles taken during the day indicated that at the depths where the species dwelt, light intensity was enough to provoke a feeding response. The larvae of these species, in contrast to the majority of fish larvae, had an enhanced sensitivity due to their pure rod‐like retina, an adaptation for foraging at low light intensities. Both species showed an ontogenetic change in their diet: B. glaciale preflexion larvae fed mainly on copepod eggs and nauplii, while postflexion larvae consumed calanoid copepodites; M. punctatum larvae showed a more diversified diet, composed of larger prey items. The stalked and elongated eye of M. punctatum larvae would enable the detection of a greater range of prey in terms of shape and size. In addition, the retina of this species was characterized by a higher summation ratio and longer photoreceptors, indicating a preference for dimmer environments. This could explain the decreasing feeding activity of M. punctatum during the high light intensity of the middle daylight hours. As a clear relationship existed between feeding pattern and light intensity in these myctophid larvae, the visual characteristics of each species could help to explain the different strategies of foraging behaviour, therefore avoiding a possible overlap in their trophic niche.
Reproductive biology of gag in the southern Gulf of Mexico
Authors: Brulé T. , Déniel C. , Colás‐Marrufo T. , Renán X.
Published: December 2003

Aspects of the reproductive biology of gag Mycteroperca microlepis in the southern Gulf of Mexico were studied by following seasonal variations in the gonado‐somatic index and through histological examination of gonads. Gag were collected from inshore and offshore waters of the Campeche Bank, Yucatan, Mexico, between April 1996 and December 2001. This species is a protogynous hermaphrodite, and appeared to be depth‐size distributed. The smallest gag (9–49 cm LF) collected were all juvenile females, and were caught in inshore waters (1–10 m depth), while the largest (49–116 cm LF), mainly adult females, males and transitionals, were captured in offshore waters (33–167 m depth). Overall the offshore male to female ratio was female‐biased (1 : 3·3) and differed significantly from unity. The species spawns at depths of c. 50–53 m, from early winter to mid‐spring, with peak spawning activity occurring between January and March. Fifty per cent of females reached first maturity at 72·1 cm LF. At 103 cm LF, 50% of sampled females had changed into males. Gag can be considered a monandric species, and sexual transition for this grouper seemed to occur in fish distributed within a narrow size range (85–111 cm LF). The results are compared with those of other authors for gag stocks from the south‐east Atlantic coast of the U.S.A. and the north‐east Gulf of Mexico.
Late migration and seawater entry is physiologically disadvantageous for American shad juveniles
Authors: Zydlewski J. , McCormick S. D. , Kunkel J. G.
Published: December 2003

Juvenile American shadAlosa sapidissimawere subjected to isothermal transfers into sea water (salinity 24)‘early’(1 September; 24° C) and ‘late’(10 November; 10° C) in the autumn migratory season. Early acclimation resulted in a modest osmotic perturbation that recovered rapidly. Haematocrit declined by 14% at 24 h, recovering within 48 h. Plasma osmolality increased by 6% at 4 h, recovering within 8 h. Early acclimation caused a two‐fold increase in gill Na+, K+‐ATPase activity by 24 h and a four‐fold increase by 4 days. The number of chloride cells on the primary gill filament increased two‐fold by 4 days. Chloride cells on the secondary lamellae rapidly decreased from 22 cells mm−1to <2 cells mm−1within 4 days. Late acclimation resulted in a severe and protracted osmotic perturbation. Haematocrit levels declined by 23% at 4 days, recovering by 14 days. Plasma osmolality increased by 36% by 48 h, recovering by 4 days. Initial gill Na+, K+‐ATPase activity was two‐fold greater than in ‘early’ fish and did not change during acclimation. Initial numbers of chloride cells on the primary filament were two‐fold greater than ‘early’ fish and did not increase during acclimation. Initial number of chloride cells on the secondary lamellae was five‐fold greater than ‘early’ fish (116v. 22 cells mm−1) and declined to negligible numbers over 14 days. Differences between initial measures for ‘early’ and ‘late’ fish reflect previously described physiological changes associated with migration. These data indicate that late migrants face a greater physiological challenge during seawater acclimation than early migrants. Physiological performance apparently limits the observed duration of autumnal migration.
Temporal and environmental influences on the variation in Atlantic salmon smolt migration in the Burrishoole system 1970–2000
Authors: Byrne C. J. , Poole R. , Rogan G. , Dillane M. , Whelan K. F.
Published: December 2003

The relationships between a number of environmental variables and the number of Atlantic salmon Salmo salar smolts migrating in the Burrishoole system, western Ireland, were examined over a 30 year period from 1970 to 2000. The number of Atlantic salmon smolts recorded migrating downstream decreased significantly from an annual mean of 11 579 in the 1970s to a mean of 6272 in the 1990s. The primary factor in the decline in Atlantic salmon numbers was a consistent decline in the number of returning adults from the 1970s until the mid 1990s. Timing of the smolt migrations (runs) was consistent throughout the three decades. The mean durations of the smolt runs were 102·1, 92·6 and 103·2 days for the 1970s, 1980s and 1990s respectively. Mean surface water temperatures at key points in the smolt run for the three decades were also similar. Mean water temperature values were 5·4, 5·1 and 5·3° C at the start of the smolt runs and 15·2, 14·9 and 15·3° C at the end of the smolt runs in the 1970s, 1980s and 1990s respectively. Multivariate analysis identified two groups of environmental variables which had a significant influence on the daily smolt catch. One group of variables dominated by photoperiod and temperature operated prior to the smolt run and was considered to regulate the development of smoltification. The second group of variables dominated by total light and water level operated within the smolt run and was considered to control daily smolt migration.