Search

This thesis consists of three essays about migration, gender, and family economics, within the framework of applied economics and with a special focus on a developing country. The first essay of my thesis contributes to the literature on fiscal policies and intergenerational transfers. The second essay contributes to the literature on the effects of children’s sex composition on parental behavior and how it may affect children’s cognitive and non-cognitive development. The third essay contributes to the literature on gender and family economics. The first chapter, co-authored with Rómulo A. Chumacero, develops a business cycle model of a small open economy with heterogeneous agents and international labor mobility, with a particular focus on taxes and transfer policies. Migration occurs as a result of the maximization problem of families and, combined with remittances, makes consumption smoothing possible. This paper shows how transfers from the government to young people and elders, funded with distortionary taxes, prompt the migration of people of working age and, among them, some of the most skilled members of the economy. The model is calibrated to match labor mobility in various age-skill groups and aggregate cycle dynamics of the Uruguayan economy, including government transfers and migration volatility. The second chapter investigates how the gender of the second-born sibling affects first- born cognitive and non-cognitive development and their parental treatment when children are on average 52 months (and not older than 66 months) in Uruguay. Since the study looks at children at a very early age, sibling-to-sibling influences are unlikely to play a role and hence an opportunity to isolate effects that arise purely via parental treatment. The identification strategy overcomes parental preferences’ bias of children’s sex composition due to the randomness of the sex of the second-born child. Results show that first-born boys who have a same-sex younger sibling have lower levels of motor skills and non-cognitive development. In contrast, first-born girls are not affected by having a younger sister or brother. The main drivers of the differences between first-born boys and girls are the lower probability of boys living with both biological parents, less investment of parents in their quality time, and a reduced likelihood of attending preschool. The third chapter analyzes the impact of intra-household bargaining on the labor supply of heterosexual couples with different divisions of domestic work. The objective is to compare the decision-making process in families with egalitarian, traditional, and non-traditional gender role attitudes towards the division of domestic work. Data from Uruguay shows that couples of all types are sensitive to bargaining power shifts, as measured by the non-labor income difference between cohabiting partners and married couples. Results suggest that a relatively rich male has more bargaining power and supplies less labor, and the opposite is true for his partner. In addition, being married reduces the labor supply of women and increases that of men in egalitarian households. These results are robust to selection into employment correction. Finally, less gender-normative households assign a larger share of non-labor income to women after the negotiation process. Esta tesis consta de tres ensayos sobre migración, género y economía de la familia, en el marco de la economía aplicada y con especial énfasis en un país en desarrollo. El primer capítulo de mi tesis contribuye a la literatura de políticas fiscales y transferencias inter- generacionales. El segundo capítulo contribuye a la literatura sobre los efectos de la com- posición sexual de los hijos en el comportamiento de los padres y cómo puede afectar el desarrollo cognitivo y no cognitivo de los niños y niñas. El tercer capítulo contribuye a la literatura sobre género y economía de la familia. El primer capítulo, en coautoría con Rómulo A. Chumacero, desarrolla un modelo de ciclos económicos de una economía pequeña y abierta a la movilidad de internacional del trabajo y agentes heterogéneos, con especial atención a los impuestos y las políticas de transferencia. La migración se produce como resultado del problema de maximización de las familias y, combinada con las remesas, hace posible la suavización del consumo. Este trabajo muestra cómo las transferencias del gobierno a los jóvenes y a los mayores, financiadas con impuestos distorsionantes, impulsan la migración de las personas en edad de trabajar y, entre éstas, a algunos de los miembros más calificados de la economía. El modelo se calibra para que coincida con la movilidad laboral en varios grupos de edad y nivel de calificación, así como con la dinámica del ciclo agregado de la economía uruguaya, incluidas las transferencias del gobierno y la volatilidad de la migración. El segundo capítulo investiga cómo el sexo del segundo hermano afecta al desarrollo cognitivo y no cognitivo del primer hijo y al comportamiento de los padres cuando los niños tienen una media de 52 meses (y no más de 66 meses) en Uruguay. Dado que este trabajo analiza a los niños en edades muy tempranas, es poco probable que las influencias entre hermanos desempeñen un rol importante en los resultados cognitivos y no cognitivos, brindando una oportunidad para aislar los efectos que surgen puramente a través del comportamiento de los padres. La estrategia de identificación supera el sesgo en las preferencias de los padres sobre la composición del sexo de los hijos debido a la aleatoriedad del sexo del segundo hijo. Los resultados muestran que tener un segundo hermano varón, relativo a tener una segunda hermana, afecta negativamente el desarrollo motor y el desarrollo no cognitivo del primer hijo, pero no afecta de forma diferenciada el desarrollo de la primer hija. Los principales mecanismos que podrían explicar las diferencias observadas entre los primeros hijos e hijas son: la menor probabilidad de vivir con ambos padres biológicos, la menor inversión de los padres en tiempo de calidad y la menor probabilidad de que asistan a la escuela pre-escolar. El tercer capítulo analiza a través de la oferta de trabajo de hombres y mujeres, el poder de negociación al interior de hogares en parejas heterosexuales, que difieren en normas sociales respecto a la división del trabajo doméstico y que son clasificados como tradicionales, igualitarios y no tradicionales. Los datos de Uruguay muestran que los hogares son sensibles a cambios en el poder de negociación, medidos por la diferencia de ingresos no laborales entre los miembros de la pareja y el hecho de estar casados. Los resultados sugieren que un hombre relativamente más rico tiene mayor poder de negociación y ofrece menos horas al mercado de trabajo, y lo contrario ocurre con su pareja. Además, el hecho de estar casado reduce la oferta de trabajo de las mujeres y aumenta la de los hombres en los hogares igualitarios. Estos resultados son robustos a la corrección por sesgo de selección en el mercado laboral. Por último, los hogares menos normativos en materia de género asignan una mayor parte de los ingresos no laborales a las mujeres tras el proceso de negociación.

Introduction Son preference, an ongoing concern in India, is a known driver of ideal family size preferences and contraceptive use among couples. These associations can vary substantially with parity and can influence men and women differently. This study assesses the association of sex composition of children by parity and a) men's higher ideal family size preference relative to women and b) use of modern contraceptives by couples. Methods We used the Couples Recode dataset from National Family Health Survey (NFHS) 2015-16 and identified couples who had at least one child and had complete responses for variables used in the study (N = 56,731 couples). We developed multivariable linear and logistic regression models to study the association between sex composition of children by parity and our dependent variables. Results Our findings indicate that the sex composition of children is associated with men's higher ideal family size preference, relative to women, among couples with four or more children. We also find that couples with less than four children are less likely to use modern contraceptives when they have an equal or a greater number of daughters than sons compared to those who have no daughters. Findings suggest that couples with four or more children are more likely to use modern contraceptives when they have at least one son and one daughter and are less likely to use contraceptives when they have all daughters and no sons, than couples who have no daughters. Conclusion This study contributes to existing research on the relationship between sex composition of children with ideal family size preferences and contraceptive use by highlighting meaningful differences between higher and lower parity couples. Findings from the study can be used by family planning programs in India to customize family planning counselling messages by both sex composition and parity., Highlights • Men do not have a higher ideal family size preference, relative to women among couples with less than four children. • Men's higher ideal family size preferenceobserved only among couples with four or more children. • Couples with less than four children are less likely to use modern contraceptives when they have more daughters than sons. • Couples with four or more children are less likely to use contraceptives if they have all daughters and no sons.

Background School injuries are an important adolescent health problem. Previous research suggests that relevant risk behaviors for school injuries, risk-taking and aggression, are highly susceptible to peer effects. Specifically, evidence suggests that the ratio of men and women in peer groups (sex ratio) affects individuals’ propensity for aggression and risk-taking. However, potential associations of classroom sex ratios with adolescent school injury risks have not been studied so far. The purpose of this paper is to investigate the association of classroom sex compositions with adolescent school injuries. Methods We investigate the association of classroom sex ratios with school injuries in a longitudinal survey dataset containing 13,131 observations from 9,204 adolescent students (ages 13-16) from secondary schools in Germany. The data also allow us to identify injuries due to aggressive behavior and analyze these injuries in detail. We use multilevel logistic regression models to analyze risks of both overall and aggression-related school injuries. Results Adolescent students’ risk for school injuries is significantly and positively associated with male-skewed classroom sex ratios (OR = 1.012, p=0.012). Specifically, the risk of sustaining a school injury increases by 33.5 percent when moving from the 10th to the 90th classroom sex ratio percentile. Moreover, we find an even stronger positive association between male-dominated classrooms and aggression-related injury risks (OR = 1.022, p=0.010). Compared to classroom sex ratios at the 10th percentile, the risk of an aggression-related injury is 78 percent higher in classrooms with a sex ratio at the 90th percentile. Finally, we find that both boys’ and girls’ injury risks equally increase with a higher proportion of male students in their classroom. Conclusions Our findings indicate that sex composition of classrooms is an important contextual factor for adolescent school injuries, in particular school injuries resulting from aggression. These findings illustrate the need to integrate a contextual perspective on school injuries among adolescent students both into research and into intervention planning. Supplementary Information The online version contains supplementary material available at 10.1186/s12889-021-12370-8.

This paper studies whether sibling gender affects personality traits. We use the idea that if parents decide to have a second child, it is random whether they will have a boy or a girl. Therefore, the relationship between the second-born sibling's gender and the first sibling's personality traits is causal. We employ longitudinal data from a large British cohort which is followed from birth onwards. The dataset includes personality traits at age 10 and 16. Our main result is that oldest boys in a household are more agreeable if their next-born sibling is a girl. This effect is robust across age (10 and 16), when controlling for among others family size, and when applying corrections for multiple hypothesis tests. Agreeableness is an important trait in life as it has been shown to correlate positively among others with being employed, having a skilled job, savings, and life satisfaction.

Background: Studies on children and divorce in China find a negative association between the number of children and divorce and a protective effect of having a son. Nonetheless, we have little knowledge of how these associations have developed over time. Objective: This study explored the association of the number and sex composition of children with divorce risks in China over the period 1980-2012. Methods: We conducted an event history analysis of longitudinal data from the China Family Panel Studies. Results: Childless couples had an increasingly higher divorce risk than couples with children over our observation period. In the 2000s, the divorce risk of childless couples in both urban and rural areas was approximately five times that of one-child parents. The role of the child's gender differs for urban and rural one-child parents, with no significant effect on the divorce risk of urban parents and different effects over time for rural parents. Conclusions: Our findings show that ending a marriage when having no children has become an increasingly pronounced trend. Furthermore, partially due to the rapid socioeconomic and demographic progress and the rise of girls' empowerment, the child's gender has lost importance for the divorce risk of urban parents. Contribution: This study enriches our knowledge about the association between children and divorce risks in a rapidly developing society. Indirectly, the study also informs us about the evolution of son preference in China.

Society ascribes roles and expectations for people based on their sex. When the costs and benefits of each sex are different, people may have different motivations for having sons or daughters because children of different sexes are not substitutable. Sex preferences may then increase fertility, as women and couples who pursue a certain sex composition may progress to additional births. To understand how the social structure has been shaping sex preferences and fertility ideals, it is important to identify the characteristics of women with different preferences. Using responses to questions about an ideal number of children and their sex composition available in the Brazilian Demographic Health Survey of 1996 and 2006, this paper provides evidence that a balanced sex preference exists among most Brazilians; some evidence of a secondary daughter preference is also found. Evidence also shows that “gender indifference” has become more pronounced as fertility declines. A sociedade determina funções e expectativas às pessoas com base em seu sexo. Quando os custos e benefícios de cada sexo são diferentes, as pessoas podem ter diferentes motivações para ter filhos ou filhas porque crianças de diferentes sexos não são intercambiáveis. Preferências de sexo podem incrementar a fecundidade na medida em que mulheres e casais que desejam uma determinada composição de sexos entre seus filhos decidam por uma nova gravidez. Para compreender como a estrutura social determina as preferências de sexo e ideais de fecundidade, é importante identificar as características de mulheres com diferentes preferências. Utilizando respostas de questionários sobre o número ideal de crianças e sua composição de sexos, disponíveis na Pesquisa Nacional de Demografia e Saúde de 1996 e 2006, este artigo apresenta evidências que existe entre os brasileiros uma preferência de sexos balanceada, bem como evidências de uma preferência secundária por filhas. Evidências também apontam para uma “indiferença de gênero” que se tornou mais pronunciada conforme a fecundidade diminui.

Background Sex composition of living children within the context of “sex preference” and its association with various reproductive health outcomes has been extensively studied in South and South East Asia. Although sex preference has been observed in sub-Saharan Africa, there is paucity of research on sex composition of living children and its association with reproductive health behaviours and outcomes, particularly in a matrilineal inheritance system. The purpose of the study was to explore the existence of sex preference in a matrilineal inheritance system. Specifically, the study sought to better understand the issues by examining the sex composition of living children and how it is associated with reproductive outcomes such as pregnancy intendedness and intention to use postpartum family planning among women in a matrilineal area of Ghana. Methods This was a cross sectional study conducted at four selected health facilities in the Mfantseman municipality of the Central Region of Ghana. Out of the 1914 pregnant women attending antenatal clinic selected using total enumeration, from 2nd January to 30th April 2012, 1091 with living children and complete socio-demographic data were recruited for this study. Descriptive, chi square and multivariate logistic regression analyses were conducted. Results The mean age of the 1091 respondents in this study was 28.2 ± 6.0 years with mean gestational age of 26.7 ± 6.6 weeks. Whilst 78% of the women had at least a son, 71% had at least a daughter, with those having only sons exceeding those with only daughters by 6.3%. Also, majority of the women with more sons than daughters did not intend their current pregnancies. These observations, coupled with a sex ratio of 109 males to 100 females, inferred the existence of son preference. The levels of unintended pregnancy and intention to use postpartum family planning were high (70% and 78% respectively). There was an association between sex composition of living children and unintended pregnancy but no association between sex composition of living children and intention to use postpartum family planning. Women with only sons were 50% less likely to have unintended pregnancies compared to those with equal number of sons and daughters [AOR 0.5, 95% CI (0.3–0.8)]. Similarly, women over 30 years were 80% less likely to have unintended pregnancies compared to those 15–19 years [AOR 0.2, 95% CI (0.1–0.6)]. The women with parity of 5 or more and resident in Anomabo were more likely to have unintended pregnancy compared to those with parity of up to two [AOR 3.8, 95% CI (1.7–8.59)] and those resident in Saltpond [AOR 1.8, 95%CI (1.1–2.8), respectively. In addition, the women resident in Anomabo were more likely to have intention to use postpartum family planning compared to those in Saltpond [AOR 1.8, 95% CI (1.0–3.3)]. Conclusion There was persistence of more sons than daughters born in a predominantly matrilineal inheritance system and sex composition of living children had significant association with pregnancy intendedness but not with intention to use postpartum family planning.

We examine how the gender of a sibling affects labor market outcomes and family formation. Identification is complicated by parental preferences: if parents prefer certain sex compositions over others, children' s gender affects not only the outcomes of other children but also the existence of potential additional children. We employ two empirical strategies that both address this problem. First, we use a large sample of singletons to estimate whether first-borns are affected by the gender of their second-born sibling. Second, we look at a sample of dizygotic (i.e. non-identical) twins. We find that a same-sex sibling increases men's earnings and family formation outcomes (marriage and fertility), as compared to an opposite-sex sibling. The results for women are similar but the effects are smaller in magnitude and less robust. We argue that the income result for men could be driven by competition between brothers, as we find that men with brothers choose higher paying occupations. For women, we find suggestive evidence that the income premium may come partly from lower unemployment, which could be due to shared job search networks. The effects on family formation might stem from differential parental treatment for men, and from competition between sisters for women.

Successful social interaction requires the ability to integrate as well as distinguish own and others' actions. Normally, the integration and distinction of self and other are a well-balanced process, occurring without much effort or conscious attention. However, not everyone is blessed with the ability to balance self-other distinction and integration, resulting in personal distress in reaction to other people's emotions or even a loss of self [e.g., in (subclinical) psychosis]. Previous research has demonstrated that the integration and distinction of others' actions cause interference with one's own action performance (commonly assessed with a social Simon task). The present study had two goals. First, as previous studies on the social Simon effect employed relatively small samples (N < 50 per test), we aimed for a sample size that allowed us to test the robustness of the action interference effect. Second, we tested to what extent action interference reflects individual differences in traits related to self-other distinction (i.e., personal distress in reaction to other people's emotions and subclinical psychotic symptoms). Based on a questionnaire study among a large sample (N = 745), we selected a subsample (N = 130) of participants scoring low, average, or high on subclinical psychotic symptoms, or on personal distress. The selected participants performed a social Simon task. Results showed a robust social Simon effect, regardless of individual differences in personal distress or subclinical psychotic symptoms. However, exploratory analyses revealed that the sex composition of interaction pairs modulated social Simon effects. Possible explanations for these findings are discussed.

We examine how the gender of a sibling affects earnings, education and family formation. Identification is complicated by parental preferences: if parents prefer certain sex compositions over others, children's gender affects not only the outcomes of other children but also the very existence of potential additional children. We address this problem by looking at dizygotic twins. In these cases, the two children are born at the same time, so parents cannot make decisions about one twin based on the gender of the other twin. We find that the gender of the sibling influences both men and women, but in a different way. Men with brothers earn more and are more likely to get married and have children than men with sisters. Women with sisters obtain lower education and give birth earlier than women with brothers. Our analysis shows that the family size channel cannot explain the findings. Instead, the most likely explanation is that siblings affect each other via various social mechanisms.

In demography, the value of children refers most often to the benefits parents receive from having and rearing children. Benefits may accrue from the children themselves, from the experience of rearing them, or from the responses of kin, community, and society at large. Children also entail costs for parents and the value of children sometimes refers to their net value (benefits less costs). Benefits and costs of children are shaped by the economic conditions of life, forms of social organization, and cultural beliefs and practices. Studies using surveys to measure the value of children report variation in values across societies; by socioeconomic status; between women and men; for first, second, and higher order births; and for daughters versus sons. Cultural foundations for the value of children have also been explored. The net value of children underlies parents' desires for children which, in combination with their ability to achieve those desires, influences their decisions to have children and how many children they have.

Panopea abbreviata es el molusco bivalvo infaunal de mayor tamaño del Mar Argentino. Se distribuye desde Río de Janeiro (Brasil) hasta la Patagonia Argentina. En los golfos San Matías (GSM) y San José (GSJ), conforma una metapoblación que presenta una distribución discontinua, formada por una serie de poblaciones ubicadas a lo largo de las costas.Es el bivalvo más longevo explotado en el Atlántico Sur. En el GSM su pesquería comenzó en el año 2000 y, si bien la misma es incipiente, debido a las características biológico-poblacionales de P. abbreviata es un recurso que requiere de un manejo precautorio. Excepto por estudios preliminares sobre el crecimiento y el ciclo reproductivo, no se contaba con la información básica para manejo. El objetivo general del presente trabajo de tesis fue integrar procesos y patrones de la dinámica poblacional de P. abbreviata, con especial consideración de la estructura espacial, para establecer puntos de referencia biológicos que permitan orientar el proceso de pesca y explorar opciones para el manejo sustentable.El área de estudio comprende sitios ubicados dentro del GSM y del GSJ. Ambos golfos están divididos en dos sectores hidrográficos por frentes termohalinos. Esta configuración define tres dominios dentro de los cuales se han elegido dos sitios: i) GSM, al noroeste del frente termohalino: El Sótano y Punta Colorada ii) GSM sur y sector Oeste del Golfo San José: Puerto Lobos y La Tapera iii) GSJ al este del frente termohalino: Playa Fracasso y Punta Conos. En cada uno de estos sitios se realizaron muestreos entre los años 2006 y 2011 con el fin de estudiar la estructura de tallas y edades, patrón de crecimiento individual, mortalidad y tendencias históricas en el reclutamiento.La edad de los individuos se estimó a partir de las líneas de crecimiento anuales observadas en cortes delgados de valvas. Se encontraron diferencias significativas entre las estructuras de edades de todas las poblaciones. El rango de edad fue entre 1 y 60 años, hallándose una marcada diferencia en la edad máxima entre las poblaciones del GSM (60 años) y el GSJ (30 años). El patrón de crecimiento individual fue estudiado utilizando el modelo de von Bertalanffy. En todas las poblaciones estudiadas el patrón fue similar y coincidió con el hallado en estudios previos para esta especie y otras especies del género Panopea, caracterizado por un crecimiento rápido durante los primeros 10 años de vida que luego prácticamente se detiene. Se encontraron diferencias significativas en los parámetros estimados de este modelo entre todas las poblaciones. El ciclo reproductivo de P. abbreviata fue estudiado, durante abril-2006 a abril-2007 en El Sótano, y enero-2007 a diciembre-2007 en Puerto Lobos y Punta Conos, usando técnicas histológicas estándar e indicadores cualitativos y cuantitativos. El patrón reproductivo se caracterizó por una continua proliferación y evacuación de gametas a lo largo de todo el año. Este patrón no exhibió variaciones interanuales ni entre las poblaciones, y es único en el género Panopea. Los indicadores cuantitativos permitieron observar una ligera estacionalidad en El Sótano y Puerto Lobos: durante el otoño e invierno predominan las fases de proliferación y maduración, mientras que en primavera y verano predominan desove y recuperación. En Punta Conos el patrón fue más irregular. La proporción de sexos no fue significativamente diferente de 1:1. Sin embargo, en las tres poblaciones se observó que la proporción es balanceada en los individuos mayores, pero los machos predominan en las tallas más pequeñas. Este patrón sugiere que la especie podría ser protándrica. Se observaron muy pocos individuos hermafroditas, lo cual podría deberse a que la reversión sexual se produzca en forma rápida, o bien, que la reversión se produzca en edades y tallas tempranas. La tasa instantánea de mortalidad fue estimada utilizando diferentes métodos (método de la longevidad, curva de captura, estimador de Chapman-Robson y método tafonómico). Los valores estimados variaron entre 0,0526 y 0,243 años-1 de acuerdo al método empleado para la estimación. A partir de la estimación de la tasa instantánea de mortalidad natural, por el método tafonómico, y las estructuras de edades de las seis poblaciones, se reconstruyeron las tendencias históricas en el reclutamiento. Las mismas, al considerar año a año, no mostraron coherencia geográfica. Sin embargo, en todas las poblaciones se encontró una tendencia creciente en las últimas décadas. Esta tendencia sería un proceso gradual que se puede observar a escala de décadas. Las poblaciones que se encuentran en el GSJ serían relativamente nuevas, estando presentes desde 1980 en adelante. En la actualidad, sólo dos poblaciones, El Sótano y Puerto Lobos, son explotadas. Para analizar la pesquería se utilizaron cuatro fuentes de información pesquera: relevamientos cualitativos, observadores a bordo, partes de pesca y muestreos de desembarcos. La pesquería en El Sótano presentó dos pulsos claramente definidos. El primero, durante los años 2001 y 2002, bajo un régimen de pesca experimental con un número limitado de embarcaciones que realizaron pocas salidas. El segundo, desde el año 2006 a la actualidad, con un régimen virtualmente abierto, que superó el número de salidas y la captura total del primer pulso y continúa creciendo. Las estructuras de tallas y pesos de las capturas presentaron diferencias entre años, en particular en la proporción de individuos grandes. La abundancia relativa, en las distintas poblaciones del GSM, presentó una gran heterogeneidad espacial, con parches de densidad variable dentro de cada población. Los resultados obtenidos a partir del estudio de la CPUE sugieren una variación en la abundancia a pequeña escala. P. abbreviata presenta algunas características, como la longevidad, baja tasa instantánea de mortalidad natural, dificultad para estimar la biomasa de las poblaciones y para observar los cambios en la productividad a corto plazo, que imponen precaución en el desarrollo de su explotación. Sin embargo, también presenta características positivas para el desarrollo de la misma, como el crecimiento rápido, edad de primera madurez temprana, tendencias históricas en el reclutamiento que indican que las poblaciones se encuentran en expansión y constituye una metapoblación ampliamente distribuida. Una explotación sustentable de las poblaciones es posible bajo un régimen de comanejo, que involucre a todos los actores de la pesca, basado en medidas que contemplen regulaciones espacialmente explicitas y tomen en cuenta la variabilidad observada entre las poblaciones. ENGLISH ABSTRACT: Panopea abbreviata, the southern geoduck, is the largest infaunal bivalve of the Mar Argentino. P. abbreviata is distributed from Rio de Janeiro (Brazil) to Patagonia Argentina. In San Matías (SMG) and San José (SJG) gulfs, there is a metapopulation with discontinuous distribution, formed by a number of populations located along the coast. Southern geoduck is the most long-lived bivalve exploited in the South Atlantic. In SMG the fishery began in 2000. Due to its biological and demographic characteristics, it is a resource that requires a precautionary management, even when is an incipient fishery. However, there were no basic information for such management, except for preliminary studies on growth and reproductive cycle. The main objective of this thesis was to integrate patterns and processes of P. abbreviata population dynamics, with special consideration on spatial structure. This information will enable to establish biological reference points to guide the process of fishing and exploring options for sustainable management. The study area includes sites located at SMG and SJG. Both gulfs are divided into two hydrographic sectors by thermohaline fronts. This configuration defines three dominions within which two sites were chosen: i) SMG, NW of the thermohaline front: El Sótano and Punta Colorada ii) SMG, SW sector of the San Jose Gulf: Puerto Lobos and La Tapera iii) SJG, E sector of the thermohaline front: Playa Fracasso and Punta Conos. Each of these sites was sampled between 2006 and 2011 in order to study size, age structure, individual growth pattern, mortality and historical trends of the recruitment. Ages of individuals were estimated from annual growth lines observed in thin sections of the geoduck´s shell. Geoduck ages ranged between 1 and 60 years old. Marked difference between maximum age of SMG (60 years) and SJG (30 years) populations was found. Also, significant differences between the age structures of all populations were found.Individual growth pattern was estimated by the von Bertalanffy model. The similar pattern was found for all populations as it was for previous studies conducted on this and other species of genus Panopea. Southern geoducks grow rapidly during the first 10 years and slow down in the following years. There were significant differences in the individual growth parameters between populations. The reproductive cycle of the southern geoduck was studied throughout April 2006-April 2008 at El Sótano and between January 2007- December 2007 in Puerto Lobos and Punta Conos. Standard histological techniques and quantitative indicators were used. The reproductive pattern of P. abbreviata is characterized by a continuous proliferation and spawning throughout the year. This pattern did not exhibit interannual variations nor among populations. It is similar to that described for other southern geoduck populations but is unique for this genus. Quantitative indicators allowed us to elucidate a slight seasonality in the reproductive cycle at El Sótano and Puerto Lobos: a pronounced spawning takes place during warm months and gamete accumulation occurs during cold months. In contrast, at Punta Conos the pattern was irregular. Sex ratios were not different of 1:1. But even when the sex ratio was balanced in large clams, the sex ratio was biased in favour of the males for small individuals. This pattern suggests a protandric development. Few hermaphroditic individuals were found, which could be as a result of a quick sex reversal or reversal of sex occurs at small ages and sizes. The instantaneous rate of mortality was estimated using four methods (estimates of maximum age, the Chapman-Robson estimator, catch curve analysis and taphonomic method). Estimates values of instantaneous mortality rate varied from 0.0526 to 0.243 yr-1 and differed between estimation methods. The historical trend of recruitment was reconstructed using the estimation of the instantaneous natural mortality rate by phonomic method, and the age frecuency distribution of six populations. In all populations an increasing trend in recruitment were found over the past decades. Populations in the SJG would be relatively new, being present from 1980 onwards. Actually, only two populations, El Sótano and Puerto Lobos, are exploited. To analyze the fishery, there were used four sources of information: qualitative surveys, on board observers reports, fishing reports and sampling of landings. The fishery at El Sótano had two clearly defined pulses. The first one between 2001 and 2002, with a limited number of vessels under a experimental fishing regime. The second one, since 2006, that had more fishing trips than the first one. Sizes and weights catches frequency distributions differed between years, particularly for large individuals. Relative abundance of the different populations in SMG, showed a large spatial heterogeneity, with patches of varying density within each population. CPUE analysis suggests that there exist a variation in abundance at small scale. P. abbreviata has some biological characteristics, such as longevity and low instantaneous natural mortality rate. These features make it difficult to estimate the biomass of the populations and to observe changes in the shortterm productivity, which impose a caution in the development of their exploitation. However, it also has positive characteristics for fishery development such as fast growth and early age at first maturity. Also, historical recruitment trends indicates that populations are expanding and they are widely distributed metapopulation. Sustainable stocks exploitation is possible under a co-management system, involving all actors of fishing, based on measures that include spatially explicit regulations and that takes into account the variability observed between populations. Tesis (Doctorado). Realizada en el IBMPAS (Instituto de Biología Marina y Pesquera "Almirante Storni", San Antonio Oeste, Argentina) Unpublished Panopea abbreviata Moluscos bivalvos almeja Manejo sustentable Dinamica Poblacional Biología pesquera crecimiento edad ciclo reproductivo composición por sexos variación espacial mortalidad reclutamiento histología condiciones ambientales

Practical phase of the project aimed at studying and determination of the most appropriate time for sturgeon catch was conducted at 10 catch stations (2 in each region) in Guilan, Mazandaran and Golestan provinces in 2002 and 2003. Number of catch stations was 4 in Guilan and Mazandaran provinces each and 2 in Golestan province. The project was carried out following the ratifications of the high committee for sustainable utilization of sturgeons which passed through in 2001. Considering the results on factors like average caviar yield, quantity and quality of produced caviar, sex composition of caught spawners and catch per unit effort we found that the average caviar yield of Persian sturgeon in all three Guilan, Mazandaran and Golestan provinces was higher in spring catch than autumn and winter and in winter catch was higher than autumn while the amount of caviar obtained was higher in autumn. Considering sex composition percentage of mature female caught was higher in spring than other seasons. Catch stations located in Guilan and western and central Mazandaran showed almost similar condition. Spring catch from late march (last 10 days) up to the 10th of May, autumn catch from late September and early October (23 September- 2 October) to the 1 st December, and winter catch from 1 st to 21st march are suitable period for catch. At the Khazarabad catch station the suitable time of catch differs from other stations therefore the proper time for catch appears to be 10- 20 may in spring and 21- 30 January in winter catch seasons. The quality and quantity of catch is suitable in spring from 21- 31 march to 21- 31 may, in autumn catch from 12- 22 October to 11- 21 December and in winter catch from 9- 19 February to 11- 20 march at catch stations located in Golestan province. As for stellate sturgeon at catch stations of Guilan and Mazandaran provinces the spring catch from 21 march specially from 21 April to 20 June was suitable and all other quantitative and qualitative factors confirmed better quality and quantity of catch in this period (21 April- 20 June) in comparison to other seasons. Gill nets (lower in number as compared to other sturgeons) could be set up beginning from 20 February to 20 March in winter catch. Our study showed quantitative and qualitative increase in catch from 9- 19 April to the end of decade from 22-31 May suggesting a suitable time of catch for stellate sturgeon in Golestan province. Based on our quantitative and qualitative results the summer catch is not suitable for Persian sturgeon and stellate sturgeon and winter catch for stellate sturgeon. Iranian Fisheries Science Research Institute Published

In Norway, Sweden, and Finland, most Eurasian beaver (Castor fiber) harvested are shot in April and May. Since beaver cannot be sexed or effectively aged under spring hunting conditions, hunters normally shoot the first animal seen. The consequences for population management are unknown. We tested the hypothesis that (1) the age composition and reproductive status of beaver shot did not vary significantly as individuals were removed sequentially from colonies, and (2) the sex ratio of shot beaver did not deviate significantly from a 50:50 distribution. We investigated the sex, age, and reproductive status of 126 beaver shot with rifles between 13 March and 15 May, 1997-1999, on a 242-km 2 land area in southeast Norway. The sex ratio of fetuses and all age groups did not deviate significantly from 50:50. The age ratio of the pooled bag was 14% juveniles, 22% 2 year olds, and 63% adults. Adults and pregnant females were more likely to be the first beaver shot from colonies. Pregnant females were probably vulnerable to hunters because of the increased nutritional demands of late pregnancy. Removal of an estimated 22-26% of the beaver population each year, of which 25% were pregnant females, was seemingly the main cause of the decline in occupied colonies from 57 to 31 (46%) during 3 years. The apparent susceptibility of adults and pregnant females to spring shooting should be considered when designing management plans for beaver.

Family size preferences may be represented by family size desires, intentions, expectations, and ideals. Desired family size is the number of children wanted in one's lifetime and is viewed as a measure of the demand for children which, in combination with the supply of children and contraception determines the number of children born. Family size desires are conceptually and empirically distinct from family size intentions, expectations, and ideals. Desires, intentions, and expectations are often uncertain and change over the life course in response to new experiences and conditions. Ideals are shaped by the larger society and therefore change more slowly. Because childbearing is a two-person event, desires and intentions of sexual partners must be considered. As predictors of aggregate or individual fertility, family size desires must be adjusted to take into account partners' desires and changes over the life course, as well as fecundity, fertility control, and other constraints on individual behavior or outcomes.

Recent studies exploring sibling rivalry in the allocation of household resources in the U.S. produce conflicting results. We contribute to this discussion by addressing the role of sibling rivalry in educational attainment in Germany. Using the German Socioeconomic Panel (GSOEP) we are able to distinguish how the effects of sibling rivalry vary by cultural affiliation, i.e., among families of West German, East German and foreign origin. We also point out and correct for a reference group problem in earlier papers analyzing sibling rivalry.

Recent studies exploring sibling rivalry in the allocation of household resources in the U.S. produce conflicting results. We contribute to this discussion by addressing the role of sibling rivalry in educational attainment in Germany. Using the German Socioeconomic Panel (GSOEP) we are able to distinguish how the effects of sibling rivalry vary by cultural affiliation, i.e., among families of West German, East German and foreign origin. We also point out and correct for a reference group problem in earlier papers analyzing sibling rivalry.

Recent studies exploring sibling rivalry in the allocation of household resources in the U.S. produce conflicting results. We contribute to this discussion by addressing the role of sibling rivalry in educational attainment in Germany. Using the German Socioeconomic Panel (GSOEP) we are able to distinguish how the effects of sibling rivalry vary by cultural affiliation, i.e., among families of West German, East German and foreign origin. We also point out and correct for a reference group problem in earlier papers analyzing sibling rivalry.

The decapod crustaceans Eurypodius latreillii (Brachyura) and Pagurus comptus (Paguridae) were the most frequently occurring species in Agassiz trawl (AGT) samples obtained during the Chilean - German - Italian Victor Hensen Expedition in the Straits of Magellan and south of the Beagle Channel. Sex composition and length structure aspects were studied using the material from 15 stations in the two areas, which comprised 773 specimens of E. latreillii and 647 P. comptus. The size frequency of both species was characterized by the presence of small individuals in shallow waters. The sex composition varied with depth, indicating a dominance of E. latreillii females in deep waters, whereas no such pattern was observed in P. comptus. These differences may be caused by epizoites of E. latreillii and the availability of vacant gastropod shells for P. comptus, in addition to geographical aspects and life-cycle patterns of these species, Los crustáceos decápodos Eurypodius latreillii (Brachyura) y Pagurus comptus (Anomura), fueron las especies encontradas con mayor frecuencia en las muestras obtenidas durante la Expedición Chilena - Alemana - Italiana “Victor Hensen” (Octubre/Noviembre de 1994) en el Estrecho de Magallanes y al sur del Canal del Beagle, en el extremo sur de Chile. En estas localidades se obtuvieron las muestras mediante una red de tipo Agassiz. Los ejemplares fueron medidos, pesados y sexados, posteriormente se analizó la composición sexual y la estructura de tallas de estas especies. Se recolectaron un total de 773 individuos de E. latreillii y 647 individuos de P. comptus. Este material corresponde a los especímenes capturados en 15 estaciones. La estructura de tallas para ambas especies se caracterizó por la presencia de ejemplares de menor tamaño hacia zonas someras. La composición sexual presentó variaciones respecto de la profundidad, indicando una dominancia de hembras en aguas profundas para E. latreillii, pero este patrón no se observó en P. comptus. Los patrones observados dependerían de la presencia de epibiontes sobre el caparazón de E. latreillii y la disponibilidad de conchas vacías de gastrópodos para P. comptus, además de aspectos geográficos y de los ciclos de vida que presentarían ambas especies en la región.

WOS: A1997XD66100011 This research was carried out from October 1990 to September 1993 in the Altinkaya Dam lake of Bafra of Samsun province. In this period, 592 Common carp (Cyprinus carpio Linnaeus, 1758) were examined totally. The purpose of this study was to determine some reproduction features of the common carp such as the spawning season, fecundity, maturity age and sex ratio. The spawning took place from April-May to September-October. The common carp was established as a fractional spawner. Both the males and the females were found to attain maturity when two years old. Of 592 specimens, 311 were females and 281 were males. In the females and males, the ovaries constituted 0.131 to 20.142 % of the total weight of the fish, with an average of 2.092 %, and testes 0.030 to 8.770 %, with an average of 2.104 %. The ovarian eggs were found to be of different sizes. The most mature ova had an average diameter from 1.003 to 1.308. The number of ova per g ovary ranged from 603 to 1954 with an average of 1213. The fecundity varied considerably from individual to individual and ranged from 14656 to 575810 eggs, the average being 156197. The fecundity showed an increase with the increase in size of the fish. The number of ova per mm fork length and per g body weight 346 and 89, respectively. The various statistical relationships between fish lenght/weight and gonad weight and fecundity have been derived.