Timing of Atlantic salmon Salmo salar smolt migration predicts successful passage through a reservoir.

Around 30% of Atlantic salmon Salmo salar smolts successfully survived passage through Loch Meig, a reservoir in the north of Scotland, en route to the sea. However, this survival rate was in turn dependent on the timing of migration, with the earliest migrants in the spring having the best chance of survival. This could have implication for fisheries management, since the estimation of smolt downstream survival may be influenced by which time period of the smolt run is analysed.

Fishes in a changing world: learning from the past to promote sustainability of fish populations.

Populations of fishes provide valuable services for billions of people, but face diverse and interacting threats that jeopardize their sustainability. Human population growth and intensifying resource use for food, water, energy and goods are compromising fish populations through a variety of mechanisms, including overfishing, habitat degradation and declines in water quality. The important challenges raised by these issues have been recognized and have led to considerable advances over past decades in managing and mitigating threats to fishes worldwide. In this review, we identify the major threats faced by fish populations alongside recent advances that are helping to address these issues. There are very significant efforts worldwide directed towards ensuring a sustainable future for the world's fishes and fisheries and those who rely on them. Although considerable challenges remain, by drawing attention to successful mitigation of threats to fish and fisheries we hope to provide the encouragement and direction that will allow these challenges to be overcome in the future.

Interactions between parental traits, environmental harshness and growth rate in determining telomere length in wild juvenile salmon.

A larger body size confers many benefits, such as increased reproductive success, ability to evade predators and increased competitive ability and social status. However, individuals rarely maximize their growth rates, suggesting that this carries costs. One such cost could be faster attrition of the telomeres that cap the ends of eukaryotic chromosomes and play an important role in chromosome protection. A relatively short telomere length is indicative of poor biological state, including poorer tissue and organ performance, reduced potential longevity and increased disease susceptibility. Telomere loss during growth may also be accelerated by environmental factors, but these have rarely been subjected to experimental manipulation in the natural environment. Using a wild system involving experimental manipulations of juvenile Atlantic salmon Salmo salar in Scottish streams, we found that telomere length in juvenile fish was influenced by parental traits and by direct environmental effects. We found that faster-growing fish had shorter telomeres and there was a greater cost (in terms of reduced telomere length) if the growth occurred in a harsher environment. We also found a positive association between offspring telomere length and the growth history of their fathers (but not mothers), represented by the number of years fathers had spent at sea. This suggests that there may be long-term consequences of growth conditions and parental life history for individual longevity.

Does individual variation in metabolic phenotype predict fish behaviour and performance?

There is increasing interest in documenting and explaining the existence of marked intraspecific variation in metabolic rate in animals, with fishes providing some of the best-studied examples. After accounting for variation due to other factors, there can typically be a two to three-fold variation among individual fishes for both standard and maximum metabolic rate (SMR and MMR). This variation is reasonably consistent over time (provided that conditions remain stable), and its underlying causes may be influenced by both genes and developmental conditions. In this paper, current knowledge of the extent and causes of individual variation in SMR, MMR and aerobic scope (AS), collectively its metabolic phenotype, is reviewed and potential links among metabolism, behaviour and performance are described. Intraspecific variation in metabolism has been found to be related to other traits: fishes with a relatively high SMR tend to be more dominant and grow faster in high food environments, but may lose their advantage and are more prone to risk-taking when conditions deteriorate. In contrast to the wide body of research examining links between SMR and behavioural traits, very little work has been directed towards understanding the ecological consequences of individual variation in MMR and AS. Although AS can differ among populations of the same species in response to performance demands, virtually nothing is known about the effects of AS on individual behaviours such as those associated with foraging or predator avoidance. Further, while factors such as food availability, temperature, hypoxia and the fish's social environment are known to alter resting and MMRs in fishes, there is a paucity of studies examining how these effects vary among individuals, and how this variation relates to behaviour. Given the observed links between metabolism and measures of performance, understanding the metabolic responses of individuals to changing environments will be a key area for future research because the environment will have a strong influence on which animals survive predation, become dominant and ultimately have the highest reproductive success. Although current evidence suggests that variation in SMR may be maintained within populations via context-dependent fitness benefits, it is suggested that a more integrative approach is now required to fully understand how the environment can modulate individual performance via effects on metabolic phenotypes encompassing SMR, MMR and AS.

A short history of providing medical history within the British medical undergraduate curriculum.

This article aims to discuss the history of medical history in the British medical undergraduate curriculum and it reviews the main characters and organisations that have attempted to earn it a place in the curriculum. It also reviews the arguments for and against the study of the subject that have been used over the last 160 years.

Among-sibling differences in the phenotypes of juvenile fish depend on their location within the egg mass and maternal dominance rank.

We investigated whether among-sibling differences in the phenotypes of juvenile fish were systematically related to the position in the egg mass where each individual developed during oogenesis. We sampled eggs from the front, middle and rear thirds of the egg mass in female brown trout of known dominance rank. In the resulting juveniles, we then measured traits that are related to individual fitness: body size, social status and standard metabolic rate (SMR). When controlling for differences among females in mean egg size, siblings from dominant mothers were initially larger (and had a lower mass-corrected SMR) if they developed from eggs at the rear of the egg mass. However, heterogeneity in the size of siblings from different positions in the egg mass diminished in lower-ranking females. Location of the egg within the egg mass also affected the social dominance of the resulting juvenile fish, although the direction of this effect varied with developmental age. This study provides the first evidence of a systematic basis for among-sibling differences in the phenotypes of offspring in a highly fecund organism.

Early maternal experience shapes offspring performance in the wild.

Both the environments experienced by a mother as a juvenile and an adult can affect her investment in offspring. However, the implications of these maternal legacies, both juvenile and adult, for offspring fitness in natural populations are unclear. We investigated whether the juvenile growth rate and adult reproductive traits (length, body condition, and reproductive investment at spawning) of female wild Atlantic salmon (Salmo salar) were related to the growth and survival of their offspring. Adult salmon captured on their upstream migration were used to create experimental full-sib clutches of eggs, which were mixed and then placed in artificial nests in a natural stream that lacked salmon due to a migration barrier. Four months later we resampled the stream to obtain family-level estimates of offspring size and survival. Mothers that had grown slowly as juveniles (as determined by scalimetry) but had invested heavily in reproduction (egg production for a given body length) and were in relatively poor body condition (somatic mass for a given body length) at spawning produced the largest eggs. Larger eggs resulted in larger juveniles and higher juvenile survival. However, after controlling for egg size, offspring growth was positively related to maternal juvenile growth rate and reproductive investment. The predictors of offspring survival (i.e., reproductive success) varied with the juvenile growth rate of the mother: If females grew slowly as juveniles, their reproductive success was negatively related to their own body condition. In contrast, the reproductive success of females that grew quickly as juveniles was instead related positively to their own body condition. Our results show that maternal influences on offspring in the wild can be complex, with reproductive success related to the early life performance of the mother, as well as her state at the time of breeding.

Metabolic divergence between sibling species of cichlids Pundamilia nyererei and Pundamilia pundamilia.

This study compared Pundamilia nyererei and Pundamilia pundamilia males in routine metabolic rate (R(R)) and in the metabolic costs males pay during territorial interactions (active metabolic rate, R(A)). Pundamilia nyererei and P. pundamilia males housed in social isolation did not differ in RR . In contrast to expectation, however, P. nyererei males used less oxygen than P. pundamilia males, for a given mass and level of agonistic activity. This increased metabolic efficiency may be an adaptation to limit the metabolic cost that P. nyererei males pay for their higher rate of aggressiveness compared to P. pundamilia males. Thus, the divergence between the species in agonistic behaviour is correlated with metabolic differentiation. Such concerted divergence in physiology and behaviour might be widespread in the dramatically diverse cichlid radiations in East African lakes and may be an important factor in the remarkably rapid speciation of these fishes. The results did not support the hypothesis that higher metabolic rates caused a physiological cost to P. nyererei males that would offset their dominance advantage.

What causes intraspecific variation in resting metabolic rate and what are its ecological consequences?

Individual differences in the energy cost of self-maintenance (resting metabolic rate, RMR) are substantial and the focus of an emerging research area. These differences may influence fitness because self-maintenance is considered as a life-history component along with growth and reproduction. In this review, we ask why do some individuals have two to three times the 'maintenance costs' of conspecifics, and what are the fitness consequences? Using evidence from a range of species, we demonstrate that diverse factors, such as genotypes, maternal effects, early developmental conditions and personality differences contribute to variation in individual RMR. We review evidence that RMR is linked with fitness, showing correlations with traits such as growth and survival. However, these relationships are modulated by environmental conditions (e.g. food supply), suggesting that the fitness consequences of a given RMR may be context-dependent. Then, using empirical examples, we discuss broad-scale reasons why variation in RMR might persist in natural populations, including the role of both spatial and temporal variation in selection pressures and trans-generational effects. To conclude, we discuss experimental approaches that will enable more rigorous examination of the causes and consequences of individual variation in this key physiological trait.

The role of physiology in the divergence of two incipient cichlid species.

Sexual selection on male coloration has been implicated in the evolution of colourful species flocks of East African cichlid fish. During adaptive radiations, animals diverge in multiple phenotypic traits, but the role of physiology has received limited attention. Here, we report how divergence in physiology may contribute to the stable coexistence of two hybridizing incipient species of cichlid fish from Lake Victoria. Males of Pundamilia nyererei (males are red) tend to defeat those of Pundamilia pundamilia (males are blue), yet the two sibling species coexist in nature. It has been suggested that red males bear a physiological cost that might offset their dominance advantage. We tested the hypothesis that the two species differ in oxidative stress levels and immune function and that this difference is correlated with differences in circulating steroid levels. We manipulated the social context and found red males experienced significantly higher oxidative stress levels than blue males, but only in a territorial context when colour and aggression are maximally expressed. Red males exhibited greater aggression levels and lower humoral immune response than blue males, but no detectable difference in steroid levels. Red males appear to trade off increased aggressiveness with physiological costs, contributing to the coexistence of the two species. Correlated divergence in colour, behaviour and physiology might be widespread in the dramatically diverse cichlid radiations in East African lakes and may play a crucial role in the remarkably rapid speciation of these fish.

Implantation of cocoa butter reduces egg and hatchling size in Salmo trutta.

This study demonstrated that, irrespective of hormone type or dose, administering cocoa butter implants during egg development affected the growth of female brown trout Salmo trutta and reduced the size of their offspring. Cortisol treatment also increased adult mortality. Caution is urged in the use of implants for studies of maternal hormonal influences on adult fishes and their offspring.

Presence of a conspecific causes divergent changes in resting metabolism, depending on its relative size.

It is well established that the average metabolism of many species of fish varies with group size. However, it is not clear whether all individuals respond in the same way. Here, we use a newly calibrated method of measuring the metabolic rate of fish from opercular (ventilatory) movements that allows for the first-time estimation of changes in resting metabolic rate (RMR) of each individual within different social groups and when alone. The presence of a conspecific had divergent effects on the RMR of juvenile Atlantic salmon Salmo salar, depending on its relative body size: the presence of a smaller fish caused a 40 per cent reduction, whereas the presence of a slightly larger fish approximately doubled RMR. These effects occurred in the absence of activity and were sustained at lower magnitude in the case of the relatively smaller conspecific even if a transparent barrier prevented any physical interactions between fish. Changes in RMR were mirrored by changes in eye colour that indicate they were linked to stress levels. These contrasting and strong responses show that even the nearby presence of a conspecific can have profound and variable effects on an individual's energy budget; they also highlight the complex trade-offs involved in social interactions.

Juvenile salmon with high standard metabolic rates have higher energy costs but can process meals faster.

Basal or standard metabolic rate (SMR) has been found to exhibit substantial intraspecific variation in a range of taxa, but the consequences of this variation are little understood. Here we explore how SMR is related to the energy cost of processing food, known as apparent specific dynamic action or the heat increment of feeding. Using juvenile Atlantic salmon Salmo salar, we show that fishes with a higher SMR had a higher peak and a greater total energy expenditure when digesting a given size of meal. However, the duration over which their metabolism was elevated after consuming the meal was shorter. The greater energy costs they incur for processing food may be related to their assimilation efficiency. These relationships are likely to have implications for feeding strategies and growth rates, since individuals with a higher SMR have higher routine costs of living but recover more quickly following feeding and so may have a greater potential for processing food.

Causes of blindness at Nkhoma Eye Hospital, Malawi.

PURPOSE: The majority of blindness in Sub-Saharan Africa is treatable. This hospital-based study was undertaken in order to investigate the etiology of blindness at Nkhoma Eye Hospital, Malawi. METHODS: One ophthalmologist examined 2082 consecutive new patients who presented to the outpatient department at Nkhoma Eye Hospital, Malawi in 2006. Data recorded included age, sex, visual acuity and diagnosis. Patients were classified as blind if their best corrected visual acuity was <3/60 in one eye (unilateral) or two eyes (bilateral). RESULTS: The most common diagnosis in new outpatients was cataract (52.8%), followed by glaucoma (8.1%), corneal pathology (7.2%), uveitis (4.5%) and maculopathy (3.2%). There were 742 (35.6%) patients with unilateral blindness and 331 (15.9%) patients with bilateral blindness. Unilateral blindness was present in 37.4% of males and 26.5% of females. The most common causes of unilateral blindness were lens pathology (57.8%), followed by glaucoma (12.1%), corneal pathology (10.0%) and uveitis (6.1%). Bilateral blindness was present in 12.5% of males and 16.8% of females respectively. The most common causes of bilateral blindness were lens pathology (54.4%), followed by glaucoma (19.9%), retinopathy (3.6%), maculopathy (3.6%), uveitis (3.6%) and corneal pathology (3.3%). CONCLUSIONS: Cataract is the most common cause of blindness in Nkhoma. Resultantly, cataract management is preferentially targeted in the Nkhoma VISION2020 Programme. Training of auxiliary eye personnel in cataract diagnosis and surgery may assist in this approach.

Deferred costs of compensatory growth after autumnal food shortage in juvenile salmon.

Growing animals are often able to offset the effects of periods of reduced food availability by subsequently undergoing a phase of elevated compensatory or 'catch-up' growth. This indicates that growth rates are not normally maximized even when food is not limiting, suggesting that fast growth may be costly. Here, we show experimental evidence of a long-term deferred cost of compensatory growth after a period of food shortage. Juvenile salmon subjected to a short-lived low-food regime in autumn subsequently entered a hyperphagic phase, leading to complete restoration of lipid reserves and partial recovery of lost skeletal growth relative to controls. However, several months later they entered a prolonged phase of poorer performance (despite food now being freely available), so that by the following spring they were substantially smaller than controls and had lower lipid reserves for their body size. The incidence of sexual maturation in males the following breeding season was also reduced. Salmon thus appear to trade off the benefits of short-term restoration of fat stores prior to winter against long-term performance.

Changes in blindness prevalence over 16 years in Malawi: reduced prevalence but increased numbers of blind.

BACKGROUND/AIMS: In the coming two decades significant increases in the burden of blindness are anticipated unless concerted efforts are made to improve eye care in developing countries. Evidence of changing prevalence rates or numbers of blind people are few. The change in blindness prevalence and the number of blind people in an adult population of Malawi was measured over a 16 year period. METHODS: In 1999 a population based survey of blindness in adults (age 50+) was conducted in Chikwawa district of Malawi. Visual acuity and cause of vision loss were recorded for each eye independently. Blindness was defined as presenting better eye vision of <6/60. Findings from a 1983 survey of blindness in the same district (using similar methods) were re-analysed to be comparable with the survey conducted in 1999. RESULTS: Among 1630 enumerated adults 89% were examined. The age adjusted prevalence of blindness in the adult population was 5.4% and more common in women than men. In each age group the prevalence of blindness was lower in 1999 than in 1983; the overall reduction in blindness was 31%. During this period the 50+ population in Malawi increased almost twofold. Extrapolating the Chikwawa district data to the Malawi population reveals that the number of blind people has increased by 24%; the increase is primarily because of the large increase in the size of the most elderly group, aged 70 and above. CONCLUSION: The majority of blind people in Chikwawa (1983 and 1999) are in the age group 70 and over. This group has had the largest proportional increase in population size in this time. Services in this population have improved in the intervening 16 years and yet there was still an increase in the number of blind people. There was little change in excess blindness in women, suggesting that the same barriers that prevented utilisation of services in 1983 probably persist in 1999. Efforts to reach the most elderly and to reach women are needed to lead to a reduction in blind people in settings such as rural Malawi.

Reduction of trachoma in the absence of antibiotic treatment: evidence from a population-based survey in Malawi.

PURPOSE: A survey was conducted in Chikwawa District, Malawi in order to compare the current prevalence of trachoma with a similar survey in 1983. METHODS: Using random cluster household sampling, children aged 1 to 6 and adults aged 50 or older were enumerated and examined for the presence of trachoma. RESULTS: Among the 1313 children enumerated, 1249 (95.1%) were examined and among the 1431 adults enumerated, 1221 (85.3%) were examined. The prevalence of active trachoma among the children was 13.9% (11.9-15.9%), 10.0% in males and 14.4% in females. The prevalence of active trachoma varied significantly among the 25 clusters, ranging from 3.9% to 38.2% with 5 clusters (20%) having a prevalence >20%. Signs of trachomatous trichiasis were observed in 1.0% of adults examined. Active disease in 1999 was associated with a longer distance to the primary water source. CONCLUSIONS: Since 1983 there has been no mass antibiotic treatment programme in the district and little change in socioeconomic status. However, compared to the 1983 findings, active trachoma has been reduced by over 50% (p < 0.001) and trachomatous trichiasis by over 80%. In the 16-year interim (especially in the past 7 years) health, water and hygiene programmes were initiated and we hypothesize that the reduction in active disease is likely due to these changes. Our findings suggest that sustained reductions in active trachoma can be achieved without community-based antibiotic distribution.

Plasma cortisol concentrations before and after social stress in rainbow trout and brown trout.

Two related experiments examined the relationship between plasma cortisol concentrations and the development of social hierarchies in fish. In the first, rainbow trout, Oncorhynchus mykiss, and brown trout, Salmo trutta, were observed for dominance interactions when confined within single-species pairs for 4, 48, or 168 h. Subordinate members of a pair exhibited significantly higher cortisol concentrations than dominant and single fish, but the pattern of cortisol elevation differed between the two species, being quicker to rise and increasing to a higher level in rainbow trout. Cortisol concentrations were correlated with behavioural measurements; the more subordinate the behaviour exhibited by a fish, the higher its cortisol concentration. Social stress was a chronic stressor, and no acclimation to social status occurred during the week. In the second experiment, measurements of plasma cortisol were made before pairing of rainbow trout and then after 48 h of confinement in pairs. Subordinate fish demonstrated significantly higher concentrations of plasma cortisol both before and after social stress. It therefore appears that in addition to cortisol being elevated during periods of social stress, an association may exist between initial cortisol levels and the likelihood of a fish becoming subordinate.

The predictability and patterns of vigilant behaviour.

While foraging, many animals alternate between feeding and scanning. Spectral analysis of continuous series of scan durations S and inter-scan intervals I for American Goldfinches Carduelis tristis, feeding either on small or large seeds, and choughs Pyrrhocorax pyrrhocorax showed that there were nonrandom fluctuations in the magnitude of S and I is all the examined series. Both the I and S showed cyclical oscillations between short and long events. Within individuals the sequential and temporal patterns in the I and S series were similar. However, the temporal patterns were more affected by variations in food-handling time than were the sequential ones. The predictability of the I and S series and the similarity, within individuals, of their sequential and temporal patterns seem general processes resistant to variations in behavioural constraints, and the temporal patterns in the I and S series fit to the method of handling food.

Perceptions of rape in a British sample: effects of relationship, victim status, sex, and attitudes to women.

A study of attitudes to rape in a non-student British sample is reported. Ninety-six subjects (64 male, 32 female) were presented with a newspaper rape account in which previous relationship between victim and rapist and victim status were manipulated. Respondents were divided into females, males with traditional attitudes to the female role, and males with progressive attitudes. Relationship and status had no effect on perceptions but consistent effects were found for sex of respondent and attitudes to the female role.