Large predators have disproportionate effects on their underlying food webs. Thus, appropriately assigning trophic positions has important conservation implications both for the predators themselves and for their prey. Large-bodied predators are often referred to as apex predators, implying that they are many trophic levels above primary producers. However, theoretical considerations predict both higher and lower trophic position with increasing body size. Nitrogen stable isotope values (δ15N) are increasingly replacing stomach contents or behavioral observations to assess trophic position and it is often assumed that ontogenetic dietary shifts result in higher trophic positions. Intraspecific studies based on δ15N values found a positive relationship between size and inferred trophic position. Here, we use datasets of predatory vertebrate ectotherms (crocodilians, turtles, lizards and fishes) to show that, although there are positive intraspecific relationships between size and δ15N values, relationships between stomach-content-based trophic level (TPdiet) and size are undetectable or negative. As there is usually no single value for 15N trophic discrimination factor (TDF) applicable to a predator species or its prey, estimates of trophic position based on δ15N in ectotherm vertebrates with large size ranges, may be inaccurate and biased. We urge a reconsideration of the sole use of δ15N values to assess trophic position and encourage the combined use of isotopes and stomach contents to assess diet and trophic level.
Body Size , Food Chain , Nitrogen Isotopes , Predatory Behavior , Vertebrates , Animals , Nitrogen Isotopes/analysis , Nitrogen Isotopes/metabolism , Predatory Behavior/physiology , Lizards/physiology , Lizards/metabolism , Fishes/physiology , Gastrointestinal Contents/chemistry , Turtles/physiology , Turtles/metabolism
Despite a global phase out of some point sources, mercury (Hg) remains elevated in aquatic food webs, posing health risks for fish-eating consumers. Many tropical regions have fast growing organisms, potentially short food chains, and few industrial point sources, suggesting low Hg baselines and low rates of trophic magnification with limited risk to people. Nevertheless, insufficient work on food-web Hg has been undertaken in the tropics and fish consumption is high in some regions. We studied Hg concentrations in fishes from floodplain lakes of the Juruá River, Amazonas, Brazil with three objectives: 1) determine rates of Hg trophic magnification, 2) assess whether Hg concentrations are high enough to impact humans eating fish, and 3) determine whether there are seasonal differences in fish Hg concentrations. A total of 377 fish-muscle samples were collected from 12 floodplain lakes during the low-water (September 2018) and falling-water (June 2019) seasons and analysed for total Hg and stable nitrogen (N) isotopes. The average trophic magnification factor (increase per trophic level) was 10.1 in the low-water season and 5.4 in the falling-water season, both well above the global average for freshwaters. This high rate of trophic magnification, coupled with higher-than-expected Hg concentrations in herbivorous species, led to high concentrations (up to 17.6 ng/g dry weight) in predatory pirarucu and piranha. Nearly 70% of all samples had Hg concentrations above the recommended human-consumption guidelines. Average concentrations were 42% higher in the low-water season than the falling-water season, but differences varied by species. Since Hg concentrations are higher than expected and fish consumption in this region is high, future research should focus on Hg exposure for human populations here and in other tropical-rainforest regions, even in the absence of local point sources of Hg.
Mercury , Water Pollutants, Chemical , Animals , Bioaccumulation , Environmental Monitoring , Fishes , Food Chain , Humans , Lakes , Mercury/analysis , Water/analysis , Water Pollutants, Chemical/analysis
The giant arapaima (Arapaima sp.) has been described as a fish of change in Amazonia because of its important role in the conservation of floodplains, food security and income generation for rural communities. Nonetheless, despite the cultural, ecological and economic importance of arapaima, data on diet are scarce. Aiming to expand knowledge about arapaima diet in western Amazonia, scientific knowledge was integrated with the knowledge of local dwellers. During the low-water period (September 2018) and the falling-water period (June 2019), arapaima stomachs were collected from 11 floodplain lakes in the middle Juruá River. All fishes were measured [TL (total length)] and sexed. Food items from each stomach were categorized as fishes, invertebrates, plants and bone remains and weighed. Also, in the latter period, experienced local fishers were interviewed about arapaima feeding. This integrated approach revealed that young arapaima eat fish and invertebrates but adult arapaima eat fish of a wide range of species, which were mainly of low and intermediate trophic positions. This study reports the first case of cannibalism for arapaima and also shows that during the low-water period, many individuals had empty stomachs or only some small fish-bone remains and/or plant material. Arapaima sex and TL had no influence on the absence of prey in stomach contents. Overall, it can be concluded that local people had consistent ethnobiological knowledge of arapaima feeding ecology that could be useful within management projects in the region.
Ecosystem , Feeding Behavior/physiology , Fishes/physiology , Gastrointestinal Contents , Animals , Brazil , Conservation of Natural Resources , Lakes , Rivers
The trophic position of a top predator, synonymous with food-chain length, is one of the most fundamental attributes of ecosystems. Stable isotope ratios of nitrogen (δ15N) have been used to estimate trophic position of organisms due to the predictable enrichment of 15N in consumer tissues relative to their diet. Previous studies in crocodilians have found upward ontogenetic shifts in their 'trophic position'. However, such increases are not expected from what is known about crocodilian diets because ontogenetic shifts in diet relate to taxonomic categories of prey rather than shifts to prey from higher trophic levels. When we analysed dietary information from the literature on the four Amazonian crocodilians, ontogenetic shifts in dietary-based trophic position (TPdiet) were minimal, and differed from those estimated using δ15N data (TPSIA). Thus, ontogenetic shifts in TPSIA may result not only from dietary assimilation but also from trophic discrimination factors (TDF or Δ 15N) associated with body size. Using a unique TDF value to estimate trophic position of crocodilians of all sizes might obscure conclusions about ontogenetic shifts in trophic position. Our findings may change the way that researchers estimate trophic position of organisms that show orders of magnitude differences in size across their life span.
Alligators and Crocodiles/physiology , Body Size , Diet , Food Chain , Alligators and Crocodiles/growth & development , Animals , Nitrogen Isotopes/pharmacokinetics
Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ13C from reproductive and somatic tissues were correlated, probably because δ13C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ15N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.
Fishes/physiology , Reproduction , Adiposity , Animals , Energy Metabolism , Female , Herbivory , Lipid Metabolism , Male
En el Centro Penitenciario de Hombres de Barcelona ha habido un aumento creciente de ingresos por delitos contra la seguridad vial. El objetivo de esta investigación es obtener un perfil psicológico en una muestra de 115 internos, analizar cuáles son los predictores en la conducción agresiva, y finalmente contrastar la posible existencia de diferentes tipologías, en función de la ausencia o presencia de otros delitos, con o sin componentes agresivos. Los resultados muestran que las causas o estados que causan irritación, los antecedentes familiares de conducción agresiva y la presencia de trastornos psiquiátricos son predictores de la conducta agresiva en la conducción, así como la agresividad física es también un predictor de los accidentes. No hay diferencias en internos que también presentan otras tipologías delictivas (AU)
In the Barcelona Men's Penitentiary Centre, there has been a recent increase in offenders serving time for traffic offences. The objective of this research is to obtain a psychological profile of a sample of 115 inmates, to assess what the predictors of aggressive driving are and, finally, to compare the possible existence of different types, depending on the absence or presence of other offences with or without aggression. The results show that causes of, or states that cause, irritation, as well as a family history of aggressive driving and the presence of psychiatric disorders are all predictors of aggressive driving. They also show that physical aggression is a predictor of accidents. There are no differences in offenders who have committed other types of offence (AU)
Humans , Male , Automobile Driving/psychology , Aggression/psychology , Violence/psychology , Risk Factors , Prisoners/psychology , Mental Disorders/complications
Building upon Decis and Ryan (1985) Self-determination theory as well as the sportive behavioral correlates of the model of Commitment (Scanlan et al., 1976), this study tries to establish the relationship between motivation and commitment in youth sport. For this purpose 454 young competitive soccer players answered the Sport Motivation Scale (SMS) and the Sport Commitment Questionnaire (SCQ) during the regular season. The SMS measures the three dimensions of the Motivational continuum (the Amotivation, the Extrinsic Motivation and the Intrinsic Motivation). The SCQ measures the Sportive Commitment and its composing factors such as the Enjoyment, the Alternatives to the sport, and the Social Pressure. Our findings provided a clear pattern of the influence of motivation in sport enjoyment and commitment, outlining the positive contribution of intrinsic and extrinsic motivation to enjoyment and commitment. Amotivation, contributes positively to alternatives to sport and negatively to enjoyment and commitment. It should be noted that extrinsic motivation has a higher contribution to enjoyment whereas intrinsic motivation has a higher contribution to commitment (AU)
Fundamentándose en la teoría de la Autodeterminación (Deci y Ryan, 1985) así como en los correlatos conductuales del modelo de Compromiso (Scanlan et al. 1976), este estudio trata de establecer las relaciones entre motivación y compromiso en jóvenes jugadores de fútbol. Con este propósito 454 jóvenes jugadores de fútbol contestaron la Escala de Motivación Deportiva (SMS) y el Cuestionario de Compromiso Deportivo (SCQ). El SMS mide las tres dimensiones del continuum motivacional (Amotivación, Motivación extrínseca y motivación intrínseca). El SCQ mide el compromiso deportivo y los factores que lo componen, tales como el disfrute, las alternativas al deporte y la presión social. Nuestros resultados proporcionan un patrón claro acerca de la influencia de la motivación en el compromiso y la diversión en el deporte, subrayando la contribución positiva de la motivación intrínseca y extrínseca en la diversión y el compromiso. La amotivación contribuye positivamente a las alternativas al deporte y negativamente a la diversión y el compromiso. Es de destacar que la motivación extrínseca tiene una contribución mayor a la diversión, mientras que la motivación intrínseca tiene una contribución mayor al compromiso (AU)
Humans , Male , Female , Adolescent , Adult , Motivation , Soccer/psychology , Athletic Performance/psychology , Sports/psychology , Data Analysis/methods , Behavioral Medicine/methods , Behavioral Research/organization & administration , Behavioral Research/standards , Logistic Models
Building upon Deci's and Ryan (1985) Self-determination theory as well as the sportive behavioral correlates of the model of Commitment (Scanlan et al., 1976), this study tries to establish the relationship between motivation and commitment in youth sport. For this purpose 454 young competitive soccer players answered the Sport Motivation Scale (SMS) and the Sport Commitment Questionnaire (SCQ) during the regular season. The SMS measures the three dimensions of the Motivational continuum (the Amotivation, the Extrinsic Motivation and the Intrinsic Motivation). The SCQ measures the Sportive Commitment and its composing factors such as the Enjoyment, the Alternatives to the sport, and the Social Pressure. Our findings provided a clear pattern of the influence of motivation in sport enjoyment and commitment, outlining the positive contribution of intrinsic and extrinsic motivation to enjoyment and commitment. Amotivation, contributes positively to alternatives to sport and negatively to enjoyment and commitment, It should be noted that extrinsic motivation has a higher contribution to enjoyment whereas intrinsic motivation has a higher contribution to commitment.
Competitive Behavior , Internal-External Control , Motivation , Pleasure , Soccer/psychology , Adolescent , Humans , Male , Personality Inventory/statistics & numerical data , Psychometrics , Surveys and Questionnaires
El propósito de la presente investigación fue estudiar el papel que el estilo de comunicación del entrenador y el clima motivacional inducido por él tienen en el compromiso y la diversión de los futbolistas jóvenes. Participaron 415 jugadores de fútbol de alto nivel de competición en la franja de edad de 14 a 16 años contestando cuestionarios de: a) percepción de clima motivacional inducido por el entrenador (PMCSQ-2); b) percepción de comportamientos del entrenador (CBAS-PBS); y c) compromiso deportivo (SCQ). Los resultados muestran que el clima de implicación promovido por el entrenador está altamente correlacionado con la percepción que los jugadores tienen de su comportamiento en el campo. Además, el clima motivacional y el estilo de comunicación de los entrenadores determina significativamente la diversión y el compromiso de los jugadores. La discusión se centra en la importancia de buscar y formar entrenadores con credibilidad que favorezcan el compromiso de los deportistas (AU)
The purpose of this research was to study the role of coaches communication style and coach-created motivational climate in young soccer players enjoyment and commitment. Four hundred and fifteen young soccer players of high competitive level in the age range from 14 to 16 completed the following questionnaires: a) coach-induced perceived motivational climate (PMCSQ-2), b) coaches behaviour perception (CBAS-PBS), and c) sport commitment (SCQ). Results showed that coach-created motivational climate correlated highly with the perception of coaches communication style. Moreover, coach-created motivational climate and communication style significantly determines players sport commitment and enjoyment. Discussion focuses on the importance of seeking and training credible coaches that favours athletes commitment (AU)
Humans , Male , Adolescent , Motivation , Group Processes , Soccer/psychology , Social Identification , Sports/psychology , Persuasive Communication , Psychometrics/instrumentation
The purpose of this research was to study the role of coaches' communication style and coach-created motivational climate in young soccer players' enjoyment and commitment. Four hundred and fifteen young soccer players of high competitive level in the age range from 14 to 16 completed the following questionnaires: a) coach-induced perceived motivational climate (PMCSQ-2), b) coaches' behaviour perception (CBAS-PBS), and c) sport commitment (SCQ). Results showed that coach-created motivational climate correlated highly with the perception of coaches' communication style. Moreover, coach-created motivational climate and communication style significantly determines players' sport commitment and enjoyment. Discussion focuses on the importance of seeking and training credible coaches that favours athletes' commitment.
Communication , Mentors , Motivation , Soccer , Social Environment , Adolescent , Humans , Male , Prospective Studies , Surveys and Questionnaires
The current study assessed the influence of parents' involvement on youth soccer players' commitment. 893 soccer players answered the Parental Involvement Sport Questionnaire - PISQ - (Lee & Maclean, 1997) and the Sport Commitment Questionnaire - SCQ - (Scanlan et al., 1993). The PISQ measures parents' directive behaviours, praise and understanding, as well as, active implication in the sport activity. The SCQ measures commitment and its predicting factors. Results show that praise and understanding of parents favours youth soccer players enjoyment and commitment, decreasing in this way the probability of drop-out.
En el presente estudio se ha evaluado la relación entre la actitud de los padres y madres y el compromiso deportivo de futbolistas cadetes. 893 jugadores de fútbol han contestado versiones españolas del Parental Involvement Sport Questionaire - PISQ - (Lee y Maclean, 1997) y el Sport Commitment Questionaire SCQ (Scanlan et al., 1993). El PISQ recoge los comportamientos directivos, el apoyo y comprensión, y la implicación activa de padres y madres en la actividad deportiva de los hijos. Por otro lado, el SCQ mide el compromiso de los futbolistas y los factores que lo predicen. Los resultados muestran que el apoyo y la comprensión de los padres favorecen el compromiso deportivo y la diversión de los futbolistas con lo que se disminuye la probabilidad del abandono deportivo.
The main purpose of this study was to test the Sport Commitment Model in young soccer players. Participants= (N= 437) age ranged from 14 to 16 years. Based on the sport commitment model proposed by Scanlan and colleagues, 6 scales and 28-items constitute the Sport Commitment Questionnaire (SCQ). Results of this study provide some support for the reliability and validity of the SCQ, using a sample of young soccer players. Reliability analysis provided acceptable internal consistency for four scales: Sport Commitment, Sport Enjoyment, Involvement Alternatives and Social Constraints. Sport Enjoyment (Β= .56, p<.001) and Involvement Alternatives (Β= -.40, p<.001) were the strongest sport commitment predictors. Further studies with a broader age range, different genders, and other sports or competitive levels are required to continue analyzing the sport commitment model
El principal objetivo de este estudio fue probar el modelo de compromiso deportivo en jóvenes futbolistas. Participaron 437 jugadores de fútbol con edades comprendidas entre los 14 y 16 años. El Cuestionario de Compromiso Deportivo está compuesto de 6 subescalas y 28 ítems y tiene su fundamentación teórica en el modelo de compromiso deportivo propuesto por Scanlan y colaboradores. Los resultados muestran un grado de fiabilidad y validez adecuadas. Los análisis de fiabilidad muestran consistencia interna para cuatro de las subescalas: diversión deportiva, compromiso deportivo, alternativas a la implicación y coacciones sociales. La diversión deportiva (Β=.56, p<.001) y las alternativas a la implicación (Β =-.40, p<.001) son los predictores más potentes del compromiso. Son necesarios más estudios con distintos géneros, rangos de edad, deportes y niveles competitivos para continuar el estudio del modelo de compromiso deportivo
Male , Adolescent , Humans , Group Processes , Soccer/psychology , Psychometrics/instrumentation , Psychiatric Status Rating Scales/statistics & numerical data
The main purpose of this study was to test the Sport Commitment Model in young soccer players. Participants' ( N = 437) age ranged from 14 to 16 years. Based on the sport commitment model proposed by Scanlan and colleagues, 6 scales and 28-items constitute the Sport Commitment Questionnaire (SCQ). Results of this study provide some support for the reliability and validity of the SCQ, using a sample of young soccer players. Reliability analysis provided acceptable internal consistency for four scales: Sport Commitment, Sport Enjoyment, Involvement Alternatives and Social Constraints. Sport Enjoyment (Beta= .56, p <.001) and Involvement Alternatives (Beta= -.40, p <.001) were the strongest sport commitment predictors. Further studies with a broader age range, different genders, and other sports or competitive levels are required to continue analyzing the sport commitment model.
Soccer , Adolescent , Humans , Male , Surveys and Questionnaires
Eighty-three subjects were asked to solve a series of 15 mathematical problems after having been randomly assigned to an easy (5 problems) or to a difficult (9 problems) performance challenge. In addition to this, in order to create a sense of threat, subjects were told that a loud noise would be contingent upon failing to attain the performance challenge. Goal self-efficacy was computed from calculating the difference between self-efficacy level and the performance challenge. Intrinsic incentive value was derived from a six-item scale measuring the intensity of negative affects expected by the subject to be contingent upon a hypothetical failure to attain the goal. Systolic and diastolic blood pressure, and heart rate were collected during both the task performance and a prior rest phase. Anxiety-state was measured during the task performance as well. Statistical analyses revealed that interaction of goal self-efficacy and intrinsic incentive value partially predicted systolic blood pressure and heart rate reactivity. A main effect of self-efficacy was found on diastolic blood pressure. Overall, data best fitted to non-linear, quadratic functions in which either very low or very high self-efficacy, jointly with high incentive value, led to an enhanced cardiovascular reactivity. These findings are partially consistent with those previously obtained, and point to a complex model in which self-efficacy exerts specific effects on each cardiovascular parameter, usually in a non-monotonical way. Again, incentive value appeared as a moderator, but anxiety-state did not appear as a mediator of the relationship between goal self-efficacy and cardiovascular reactivity.
Anxiety/physiopathology , Cardiovascular Physiological Phenomena , Goals , Motivation , Self Efficacy , Adult , Analysis of Variance , Blood Pressure/physiology , Female , Heart Rate/physiology , Humans , Male , Psychophysiology , Regression Analysis , Surveys and Questionnaires
Eighty students volunteered to participate in an experiment with the aim of evaluating the impact of the manipulation of self-efficacy and negative incentive values on systolic and diastolic blood pressure, and pulse pressure. The subjects were asked to solve a series of 15 mathematical problems after having been randomly assigned to one of the four experimental conditions that were generated by combining two levels of self-efficacy (high versus low), and two levels of negative incentive value (high versus low), contingent upon failing to properly perform the task. The subjects' perceived competence was also evaluated. The results are consistent with those obtained in prior experiments, and they suggest that: (1) self-efficacy and negative incentive value interact in their effects on blood pressure; (2) the cognitive regulation of systolic and diastolic blood pressure and pulse pressure can be distinguished; (3) the subjects with low self-efficacy and high negative incentive value are the ones who generally experience the greatest activation; and (4) perceived competence does not appear to contribute to the psychophysiological regulation.
Blood Pressure/physiology , Mental Fatigue/diagnosis , Mental Fatigue/etiology , Stress, Psychological/psychology , Adult , Attitude , Female , Humans , Male , Mathematics , Self Efficacy
