Effects of habitat on mercury concentrations in fish: a case study of Nile perch (Lates niloticus) in Lake Nabugabo, Uganda.

This study focused on variation in fish mercury (Hg) concentrations in 185 Nile perch (Lates niloticus) samples collected across four different habitat types in Lake Nabugabo, Uganda, a tropical lake located proximate to Lake Victoria. We quantified the stomach contents of Nile perch using the % index of relative importance, as well as, nitrogen and carbon isotopic concentrations to assess the role of diet and trophic level on Hg concentrations. In each habitat, we also evaluated a suite of chemical and physical characteristics that are commonly associated with variation in Hg bioavailability in temperate systems. Using linear mixed models and ANOVA, we demonstrate that habitat of capture is an important predictor of Hg concentrations in Nile perch from Lake Nabugabo and that the relationship between habitat and Hg is size and diet dependent. Nile perch diet as well as dissolved oxygen concentration and pH were also correlated with observed differences in fish Hg. Overall, Hg concentrations in Nile perch were all well below the WHO/FAO recommended guideline of 500 ng/g (mean 13.6 ± 0.4 ng/g wet weight; range 4.9 and 29.3 ng/g wet weight). This work contributes to a growing awareness of intra-lake divergence in Nile perch, as well as, divergence in Hg concentrations between varying aquatic habitat types, particularly wetlands.

Little evidence for morphological change in a resilient endemic species following the introduction of a novel predator.

Human activities, such as species introductions, are dramatically and rapidly altering natural ecological processes and often result in novel selection regimes. To date, we still have a limited understanding of the extent to which such anthropogenic selection may be driving contemporary phenotypic change in natural populations. Here, we test whether the introduction of the piscivorous Nile perch, Lates niloticus, into East Africa's Lake Victoria and nearby lakes coincided with morphological change in one resilient native prey species, the cyprinid fish Rastrineobola argentea. Drawing on prior ecomorphological research, we predicted that this novel predator would select for increased allocation to the caudal region in R. argentea to enhance burst-swimming performance and hence escape ability. To test this prediction, we compared body morphology of R. argentea across space (nine Ugandan lakes differing in Nile perch invasion history) and through time (before and after establishment of Nile perch in Lake Victoria). Spatial comparisons of contemporary populations only partially supported our predictions, with R. argentea from some invaded lakes having larger caudal regions and smaller heads compared to R. argentea from uninvaded lakes. There was no clear evidence of predator-associated change in body shape over time in Lake Victoria. We conclude that R. argentea have not responded to the presence of Nile perch with consistent morphological changes and that other factors are driving observed patterns of body shape variation in R. argentea.

A seven-year intervention to diffuse economic innovations with safety benefits to Wisconsin dairy farmers.

The purpose of this study was to conduct a targeted information dissemination campaign to persuade agricultural managers to adopt more profitable practices that reduce injury hazards compared to traditional practices. The project disseminated information to northeast Wisconsin dairy managers about three production practices that were more profitable and had safety benefits (barn lights, silage bags, and calf feed mixing sites) using information sources that these managers were known to rely on. The project prospectively evaluated rolling, independent, community-based, probability samples (a different group of operations each year) at baseline and after each of seven intervention years. The project also evaluated comparison samples from either Maryland or New York dairy operations after intervention years two through seven. In baseline versus year seven comparisons, the Wisconsin dairy managers reported getting more information about the three practices. Compared to New York managers, Wisconsin managers reported getting more information after year seven about the three practices. Among Wisconsin managers, intervention year was associated with increased adoption of all three practices. Compared to New York managers, Wisconsin managers were more likely to report adopting two of the three practices after year seven. A targeted campaign that disseminated information to managers through traditional channels was associated with increases in manager reports of getting information about, being aware of and adopting profit-enhancing work practices with safety benefits in a high-hazard industry.

Hypoxia and male behaviour in an African cichlid Pseudocrenilabrus multicolor victoriae.

This study tested the prediction that hypoxia may reduce the frequency of energetically expensive behaviours by quantifying male mating and aggressive displays in the cichlid Pseudocrenilabrus multicolor victoriae after long-term acclimation (5 months) to either high dissolved oxygen (DO) or low DO. Regardless of DO treatment, males engaged in more aggressive displays than mating displays; however, males acclimated to low DO reduced their total number of displays compared to high DO-acclimated males.

Genetic divergence in morphology-performance mapping between Misty Lake and inlet stickleback.

Different environments should select for different aspects of organismal performance, which should lead to correlated divergence in morphological traits that influence performance. The result should be genetic divergence in aspects of performance, morphology and associations ('maps') between morphology and performance. Testing this hypothesis requires quantifying performance and morphology in multiple populations after controlling for environmental differences, but this is rarely attempted. We used a common-garden experiment to examine morphology and several aspects of swimming performance within and between the lake and inlet populations of threespine stickleback (Gasterosteus aculeatus) from the Misty system, Vancouver Island, Canada. Controlling for body size, lake stickleback had shallower bodies, larger caudal fins and smaller pelvic girdles. With or without morphological covariates, lake stickleback showed greater performance in both sustained and burst swimming. In contrast, inlet stickleback showed greater manoeuverability than did lake stickleback in some analyses. Morphology-performance relationships were decoupled when considering variation within vs. between populations. Moreover, morphology-performance mapping differed between the two populations. Based on these observations, we advance a hypothesis for why populations adapting to different environments should show adaptive genetic divergence in morphology-performance mapping.

Geographic variation in phenotypic plasticity in response to dissolved oxygen in an African cichlid fish.

Genetic adaptation and phenotypic plasticity are two ways in which organisms can adapt to local environmental conditions. We examined genetic and plastic variation in gill and brain size among swamp (low oxygen; hypoxic) and river (normal oxygen; normoxic) populations of an African cichlid fish, Pseudocrenilabrus multicolor victoriae. Larger gills and smaller brains should be advantageous when oxygen is low, and we hypothesized that the relative contribution of local genetic adaptation vs. phenotypic plasticity should be related to potential for dispersal between environments (because of gene flow's constraint on local genetic adaptation). We conducted a laboratory-rearing experiment, with broods from multiple populations raised under high-oxygen and low-oxygen conditions. We found that most of the variation in gill size was because of plasticity. However, both plastic and genetic effects on brain mass were detected, as were genetic effects on brain mass plasticity. F(1) offspring from populations with the highest potential for dispersal between environments had characteristically smaller and more plastic brains. This phenotypic pattern might be adaptive in the face of gene flow, if smaller brains and increased plasticity confer higher average fitness across environment types.

Hypoxia and energetics of mouth brooding: is parental care a costly affair?

This study explores costs of mouth brooding and the response of parent and offspring to brooding under hypoxia in the maternal African mouth brooder Pseudocrenilabrus multicolor. Fish of swamp origin were acclimated to hypoxia (1.42 mg oxygen L(-1)) or normoxia (8.00 mg oxygen L(-1)) for a minimum of 6 months prior to measures of metabolic rate and embryo traits. Regardless of brooding stage, standard metabolic rates were lower in females acclimated to low dissolved oxygen (DO) compared to high-DO acclimated females. Regardless of DO acclimation treatment, standard metabolic rates were approximately 48% higher in brooding females (with the estimated metabolic rate of the brood removed) compared to post-brooding females. There was no difference in brood maintenance metabolism, female relative condition, embryo size, and embryo number between fish acclimated to low DO vs. high DO. However, the length of the brooding period (from egg-laying to release of fry) was approximately 27% shorter in females acclimated to low DO compared to females acclimated to high DO suggesting accelerated development in offspring brooded under hypoxia. These findings demonstrate a cost to mouth brooding and provide evidence for a parental strategy to deal with the expense of providing offspring care under hypoxia.

Energetics of hypoxia in a mouth-brooding cichlid: evidence for interdemic and developmental effects.

We used a common-garden rearing experiment to explore environmentally induced tolerance to hypoxia in the African mouth-brooding cichlid Pseudocrenilabrus multicolor. F(1) fish originating from three field populations were grown under low or high dissolved oxygen (DO), and their resting routine metabolic rate (RMR), critical oxygen tension (P(crit)), and marginal metabolic scope (MMS) were quantified. In a second rearing experiment, we compared the RMR of brooding and nonbrooding females of low-DO origin grown under low and high DO. Fish reared under low DO had a lower P(crit) than fish reared under high DO. There was also an interaction between treatment and gender; females had a higher P(crit) than males when reared under normoxia. Variation in RMR was driven primarily by population effects, and there was an interaction between treatment and population. Regardless of population or treatment, males had a higher MMS than females. Fish reared under low DO had a higher MMS than fish reared under high DO, except for the high-DO population in which there was no treatment effect. Brooding females had a higher RMR than postbrooding females regardless of the growth treatment, indicating an energetic cost to brooding. The results suggest a strong element of developmental plasticity in P(crit) across populations and both plastic and genetic components of variation in the RMR and MMS. This study also highlights the cost of parental care in mouth-brooding fishes, which may increase the fitness of the offspring at the energetic expense of the parent, a cost that may be elevated under hypoxia.

Specialized morphology for a generalist diet: evidence for Liem's Paradox in a cichlid fish.

The stable isotope ratio and seasonal changes in diet of Alluaud's haplo Astatoreochromis alluaudi, a cichlid fish with massive pharyngeal jaws well known for its ability to process hard-bodied prey, are described. The diet of A. alluaudi was quantified in Lake Saka, Uganda, over a period of 30 months. Variation in physico-chemical variables (mean monthly rainfall, water temperature, turbidity and dissolved oxygen), as well as potential competitor density and food abundance, was measured throughout the second half of the study (14 months). Stomach contents and isotope analysis revealed a diet comprised mainly of fishes and insects, with a low contribution of molluscs (0-33%) in any given month. No correlation was detected between diet and either macroinvertebrate abundance or competitor abundance. The running average rainfall was positively related to the percentage of fish consumed per month. Although A. alluaudi exhibits an apparent molluscivorous trophic morphology in Lake Saka, molluscs did not appear to compose a major portion of its diet. Gradients of rainfall seemed to be the most important environmental predictor of diet choice in Lake Saka. These results are discussed with reference to Liem's Paradox that apparently morphologically specialized fishes often function as generalist feeders in the wild.

Hypoxia and life-history traits in a eurytopic African cichlid.

This study quantified variation in key life-history traits of the widespread African mouth-brooding cichlid Pseudocrenilabrus multicolor victoriae. Egg size, number, batch reproductive effort, size at maturity and brooding efficiency were compared among field populations across a wide range of dissolved oxygen (DO) concentrations from extreme hypoxia to normoxia. In the laboratory, a similar suite of characters was quantified in F1 of low- and high-DO origin reared under low or high DO. In general, females from low-DO habitats and females reared under low DO were characterized by a smaller size at maturity and no difference in batch reproductive effort when compared with females from high-DO habitats or females reared under normoxia. A trade-off between egg size and number was evident in the field and in the laboratory-rearing experiment, but the direction of the trade-off differed. Egg size was negatively correlated with egg number across field populations; females collected from low-DO sites generally had more, smaller eggs relative to females from high-DO sites. In the laboratory-rearing experiment, F1 females of high-DO origin produced larger, fewer eggs than F1 females of low-DO origin, lending support to the field results and suggesting a heritable component to these traits. There was also an element of developmental plasticity, F1 females raised under low DO produced larger, fewer eggs compared with F1 females raised under high DO (regardless of population) suggesting that DO may interact with other variables to determine egg size in the field.

Complex phenotype-environment associations revealed in an East African cyprinid.

Environmental factors influence phenotypes directly, as well as indirectly via trait correlations and interactions with other environmental variables. Using nine populations of the African cyprinid Barbus neumayeri, we employed path analysis to examine direct, indirect and total effects of two environmental variables, water flow (WF) and dissolved oxygen (DO), on several morphological traits. WF and DO directly influenced relative gill size, body shape and caudal fin shape in manners consistent with a priori predictions. Indirect effects also played an important role in the system: (1) strong, oppositely signed direct and indirect effects of WF on body shape resulted in a nonsignificant total effect; (2) DO had no direct effect on body shape, but a strong total effect via indirect effects on gill size; (3) WF indirectly influenced gill size via effects on DO. Only through examination of multiple environmental parameters and multiple traits can we hope to understand complex relationships between environment and phenotype.

Evaluation of an occupational injury intervention among Wisconsin dairy farmers.

OBJECTIVES: Dairy farming injury rates are high. Previous agricultural research has shown that better information flow can speed adoption of more profitable practices. We conducted and evaluated an intervention to increase voluntary adoption of three production practices that were safer and more profitable than typical practices: barn lights, bag silos, and a mixing site for calf feed. METHODS: Print mass media, public events, university Extension, and dairy farmers already using the practices were all enlisted to disseminate information to 4,300 northeast district Wisconsin dairy farmers. Evaluation questionnaires were mailed to independent samples of farm managers before (n = 582) and after (n = 572) the 12 month long intervention. RESULTS: After the intervention, more managers reported getting information about barn lights from public events (12% vs. 23%) and private consultants (8% vs. 17%) and about silo bags from print media (79% vs. 87%) and private consultants (9% vs. 14%). More managers were aware of barn lights (48% vs. 72%) and the calf feed mixing site (44% vs. 56%). There was a nonsignificant tendency for more managers to report adopting barn lights (12% vs. 23%). CONCLUSIONS: Improving information flow to operation managers about safer, more profitable production practices may be a relatively easy way to supplement conventional injury control efforts in high-hazard industries.

Musculoskeletal discomfort, injuries, and tasks accomplished by children and adolescents in Wisconsin fresh market vegetable production.

Little or no research is available about the tasks that children and adolescents perform in small scale, fresh market vegetable production. A mail questionnaire was administered in an exploratory study to an age-stratified, convenience sample of children and adolescents age 5 to 18 (n = 81) who were working on Wisconsin fresh market vegetable operations. Children and adolescents reported averaging 349 hours of farm work last year. Youths completed over 1/5 of all the tractor operation and produce loading and unloading that was completed by adults or children on their farms; 1/7 of the weeding, produce washing, and packing; and 1/12 of the hand harvesting during typical weeks when they worked. Fifty percent of 15-18 year olds reported experiencing low back discomfort in the last year, and 25% reported disabling discomfort. Children and adolescents performed the same range of tasks and often the same scope of work as adults. Further investigation with larger, more representative youth samples is needed to confirm these findings.

Commentary on two articles concerning generalized and specific cognitive deficits.

This is a commentary on essays in this journal issue by M. E. Strauss (2001) and R. A. Knight and S. M. Silverstein (2001) on research methodology for studying cognitive deficits. Concentrating mostly on Knight and Silverstein's article, the authors review the psychometric issues in the matched-task design, analyze Knight and Silverstein's "process-oriented" objections to that design, and scrutinize their methods for studying cognitive deficits, examining 2 of their empirical studies as examples of those methods.

A longitudinal study of high scorers on the hypomanic personality scale.

Former college students (n = 36) identified by high scores on the Hypomanic Personality Scale (HYP; Eckblad & Chapman, 1986) were compared with control participants (n = 31) at a 13-year follow-up assessment. As hypothesized, the HYP group reported more bipolar disorders and major depressive episodes than the control group. The HYP group also exceeded the control group on the severity of psychotic-like experiences, symptoms of borderline personality disorder, and rates of substance use disorders. HYP group members with elevated scores on the Impulsive-Nonconformity Scale (Chapman et al., 1984) experienced greater rates of bipolar mood disorders, poorer overall adjustment, and higher rates of arrest than the remaining HYP or control participants.

Validity and usefulness of the Wisconsin Manual for Assessing Psychotic-like Experiences.

The Wisconsin Manual for Assessing Psychotic-like Experiences is an interview-based assessment system for rating psychotic and psychotic-like symptoms on a continuum of deviancy from normal to grossly psychotic. The original manual contained six scales, assessing thought transmission, passivity experiences, thought withdrawal, auditory experiences, personally relevant aberrant beliefs, and visual experiences. A seventh scale assessing deviant olfactory experiences was subsequently added. The rating scales have good interrater reliability when used by trained raters. Cross-sectional studies indicated that the frequency and deviancy of psychotic-like experiences are elevated among college students who were identified, hypothetically, as psychosis prone by other criteria. Psychotic-like experiences of moderate deviancy in college students successfully predicted the development of psychotic illness and poorer overall adjustment 10 years later. The manual is useful for identifying psychosis-prone individuals and is recommended for use in linkage and treatment outcome studies. The present article provides an interview schedule for collecting information required for rating psychotic-like experiences.

Implications of small scale variation in ecological conditions for the diet and density of red colobus monkeys.

In this 3-year investigation we documented patterns of density, diet, and activity of red colobus monkeys (Procolobus tephrosceles) in six areas in or near Kibale National Park, Uganda and related these patterns to availability of food resources. There were large differences in the density and behavior of the red colobus among the sites. For example, the red colobus at one site with a diverse plant community of more than 61 tree species, had a diet that included at least 42 species. In contrast, at a second site red colobus spent 92% of their feeding time eating from one species that dominated the tree community. The density of important red colobus food trees varied among sites from 32 trees/ha to 204 trees/ha, and red colobus density ranged from 0.70 groups/km(2) to 7.41 groups/km(2). Among sites, red colobus density was related to the cumulative DBH of important food trees, when one apparently anomalous site was excluded, and populations with more plant species in their diets tended to be those that were found at higher densities. Activity budgets of the red colobus populations varied markedly among sites. For example, feeding time ranged among sites from 29 to 55%, and traveling varied from 5 to 20%. When faced with increased foraging demands, red colobus reduced the time spent resting, while the time spent socializing remained fairly constant. Comparative socioecological studies typically contrast species separated by large geographical distances to ensure there is sufficient variation in the environment to detect behavioral responses. The marked differences in ecological conditions and red colobus behavior we documented over short geographical distances, suggests that small-scale contrasts are a useful tool to examine ecological determinants of behavior and community structure.

Magical ideation and social anhedonia as predictors of psychosis proneness: a partial replication.

The authors compared college students identified by high scores on the Magical Ideation Scale (M. Eckblad & L. J. Chapman, 1983) and the Revised Social Anhedonia Scale (MagSoc; n = 28; M. Eckblad, L. J. Chapman, J. P. Chapman, & M. Mishlove, 1982) with control participants (n = 20) at a 10-year follow-up assessment in an attempt to replicate L. J. Chapman, J. P. Chapman, T. R. Kwapil, M. Eckblad, and M. C. Zinser's (1994) report of heightened psychosis proneness in MagSoc individuals. The MagSoc group exceeded the control group on severity of psychotic-like experiences; ratings of schizotypal, paranoid, and borderline personality disorder symptoms; and rates of mood and substance use disorders. Two of the MagSoc participants but none of the control participants developed psychosis during the follow-up period (a nonsignificant difference). Consistent with L. J. Chapman et al.'s findings, the groups did not differ on rates of personality disorders or relatives with psychosis.

Agricultural safety efforts by county health departments in Wisconsin.

OBJECTIVE: The authors sought to improve the agriculture safety prevention efforts of county health departments in Wisconsin by examining current programs, staffs' perceptions of the farm safety problem, and the need for new resources. METHODS: A survey instrument was completed by a professional staff member of the local health department in each of Wisconsin's 69 counties. RESULTS: Usable responses were obtained from 84% of the counties. Forty-five percent of the responding staff members conducted some agricultural safety and health programs, most often health screenings or group meetings conducted collaboratively with county agricultural Extension agents. There were no major differences in county demographics or other service provision variables between staff members who conducted programs and those who did not. Staff members perceived the largest barriers to better safety as lack of staff time and difficulty getting farmers to attend safety programs. Most failed to place more emphasis on training agricultural workers to permanently correct hazards than on training them to work safely around hazards. However, the staff members ranked safety inspection checklists as the most needed new material and ranked Extension agents and farmers as the most appropriate people to conduct inspections using such checklists. CONCLUSION: County public health professionals want more staff time and new materials to increase the effectiveness of their agricultural safety efforts. Encouraging agricultural workers and family members to identify and correct hazards would be a more effective use of staff time than training people to work safely around hazards.

An improved model for professional conferences and workshops.

A cooperative learning method designed to increase learning and other benefits to participants is presented. Small group problem-solving from case studies or story narratives provides a way to overcome the limitations of conventional lecture presentations. An example that used a case study in small groups during a breakout session at a scientific conference to improve skills in intervention design and research evaluation is described.