Home About us Contact
|
Home About us Contact | ||
|
|
||
Successful Recruitment (successful + recruitment)
Selected AbstractsA numerical study of inferred rockfish (Sebastes spp.) larval dispersal along the central California coastFISHERIES OCEANOGRAPHY, Issue 1 2010CHRISTINE H. PETERSEN Abstract Successful recruitment of marine fishes depends on survival during early life-history stages, which is influenced by oceanic advection due to its impact on coastal trophodynamics and transport processes. Here we evaluate the influence of ocean circulation on the dispersal of rockfish (Sebastes spp.) larvae along the central California coast using an implementation of the Regional Ocean Modeling System, driven at the surface by output from the Coupled Ocean Atmosphere Mesoscale Prediction System. Thousands of floats simulating rockfish larval propagules, constrained to follow fixed depths, were released over a broad coastal area at 2-day intervals, and transported by simulated ocean currents at depths of 1, 7, 20, 40, and 70 m. Trajectory statistics are averaged across the 4-yr period from January 2000 through December 2003 to reveal mean trajectory direction, net displacement, fractional cross-shore loss, and duration of retention for different seasons. On average, near-surface propagules originating nearshore are transported offshore during the upwelling season, whereas deeper propagules move alongshore to the north. This vertical shear vanishes during winter, with most floats moving alongshore to the north, regardless of depth. After 35 days in the water column, typical transport distances were ,50 km for floats remaining nearshore and ,150 km for floats over the midshelf and slope. Implications for performance of marine reserves for rockfish conservation are discussed. Our results also provide evidence for a strong semiannual pattern of coastal retention rates, with high export of near-surface drifters during the upwelling season. In contrast, high rates of shelf retention occurred for releases at 20 m and deeper during summer, and at all depths during winter. [source] Resilience of tropical rain forests: tree community reassembly in secondary forestsECOLOGY LETTERS, Issue 5 2009Natalia Norden Abstract Understanding the recovery dynamics of ecosystems presents a major challenge in the human-impacted tropics. We tested whether secondary forests follow equilibrium or non-equilibrium dynamics by evaluating community reassembly over time, across different successional stages, and among multiple life stages. Based on long-term and static data from six 1-ha plots in NE Costa Rica, we show that secondary forests are undergoing reassembly of canopy tree and palm species composition through the successful recruitment of seedlings, saplings, and young trees of mature forest species. Such patterns were observed over time within sites and across successional stages. Floristic reassembly in secondary forests showed a clear convergence with mature forest community composition, supporting an equilibrium model. This resilience stems from three key factors co-occurring locally: high abundance of generalist species in the regional flora, high levels of seed dispersal, and local presence of old-growth forest remnants. [source] Modelling potential spawning habitat of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Bay of BiscayFISHERIES OCEANOGRAPHY, Issue 1 2007BENJAMIN PLANQUE Abstract Large amplitude variations in recruitment of small pelagic fish result from interactions between a fluctuating environment and population dynamics processes such as spawning. The spatial extent and location of spawning, which is critical to the fate of eggs and larvae, can vary strongly from year to year, as a result of changing population structure and environmental conditions. Spawning habitat can be divided into ,potential spawning habitat', defined as habitat where the hydrographic conditions are suitable for spawning, ,realized spawning habitat', defined as habitat where spawning actually occurs, and ,successful spawning habitat', defined as habitat from where successful recruitment has resulted. Using biological data collected during the period 2000,2004, as well as hydrographic data, we investigate the role of environmental parameters in controlling the potential spawning habitat of anchovy and sardine in the Bay of Biscay. Anchovy potential spawning habitat appears to be primarily related to bottom temperature followed by surface temperature and mixed-layer depth, whilst surface and bottom salinity appear to play a lesser role. The possible influence of hydrographic factors on the spawning habitat of sardine seems less clear than for anchovy. Modelled relationships between anchovy and sardine spawning are used to predict potential spawning habitat from hydrodynamical simulations. The results show that the seasonal patterns in spawning are well reproduced by the model, indicating that hydrographic changes may explain a large fraction of spawning spatial dynamics. Such models may prove useful in the context of forecasting potential impacts of future environmental changes on sardine and anchovy reproductive strategy in the north-east Atlantic. [source] Transport of larval jack mackerel (Trachurus japonicus) estimated from trajectories of satellite-tracked drifters and advective velocity fields obtained from sequential satellite thermal images in the eastern East China SeaFISHERIES OCEANOGRAPHY, Issue 6 2002Hee-Yong Kim Abstract Transport processes of jack mackerel (Trachurus japonicus) larvae in the waters off the west coast of Kyushu in the eastern East China Sea, have been investigated using satellite-tracked surface drifters and consecutive satellite thermal images. Trajectories of drifters describe northward flows over the continental shelf, eastward flows of the Kuroshio south-west of Kyushu, and a weak clockwise gyre off the west coast of Kyushu. In particular, the clockwise gyre causes the entrainment of jack mackerel larvae into the waters off the west coast of Kyushu. Consecutive satellite thermal images help to elucidate the northward warm water intrusion from the Kuroshio front south-west of Kyushu. Particle trajectories using sea surface current fields computed with the Maximum Cross Correlation (MCC) technique also reveal that the transport of jack mackerel larvae into the nursery ground off the west coast of Kyushu caused by the anti-cyclonic gyre and the warm streamers are an important process for successful recruitment. [source] Effective Methods to Improve Recruitment and Retention in School-Based Substance Use Prevention StudiesJOURNAL OF SCHOOL HEALTH, Issue 9 2009Jean-Marie Bruzzese PhD ABSTRACT BACKGROUND: Poor recruitment and high attrition may invalidate results of research studies. This paper describes successful recruitment and retention strategies in a school-based substance use prevention trial and explores factors associated with intervention attendance and retention. METHODS: A total of 384 parent-child dyads from 15 schools in the New York Metropolitan area participated in a control trial, testing the efficacy of parent-training to prevent youth substance use. Assessments were completed immediately post-intervention and 6-, 12-, and 24-month postintervention. Logistic regression analyses were used to determine which familial and study characteristics predicted attendance in the intervention and retention by parents and youth. RESULTS: 84% of intervention parents attended 4 of the 5 workshops; 83% of control parents attended their single workshop. Intervention attendance was predicted by parent job status, but this was not significant after controlling for other family factors. Retention rates ranged from 87% to 91% over the 2 years. No family characteristics predicted retention, but time since baseline and attendance at treatment workshops and the control workshop did. For children, age at baseline and ethnicity predicted retention, but this did not remain significant in the adjusted model. CONCLUSION: Intervention attendance was high and retention rates far exceeded the minimum standard of 70% retention in behavioral studies. Recruitment and retention strategies were effective for different family constellations. Efforts to maximize participation in both treatment and control interventions are critical to retention in longitudinal trials. [source] Gorgonian population recovery after a mass mortality eventAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2005C. Cerrano Abstract 1.Mass mortality events are becoming more common all over the world, both in tropical and temperate seas. An extensive mortality occurred in the Mediterranean Sea in 1999, affecting many benthic species, mainly sponges and gorgonians. 2.The recovery of a population of the sea fan Paramuricea clavata, for a period of 3 yr, from 1999 to 2002, was studied by both line transects and fixed frames. The average size of the colonies decreased, indicating a size-dependent mortality episode, but their density, as a result of successful recruitment, was not altered after 3 yr. 3.P. clavata showed three recovery patterns: (i) sexual reproduction, (ii) coenenchyme regeneration and (iii) fragmentation of affected branches. Moreover, the growth rates of small colonies varied in the different years. The sex ratio of the population was also altered, with females being more affected than males; the population studied showed a significant male bias (3.3:1, n=150), varying greatly from the typical sex ratio (1:1) previously recorded in the same population before the mass mortality event. Copyright © 2004 John Wiley & Sons, Ltd. [source] The conservation of unionid mussels in Louisiana rivers: diversity, assemblage composition and substrate useAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2001Kenneth M. Brown Abstract 1.,To aid in their conservation, unionid mussel assemblages were surveyed in three relatively unstudied rivers in south-eastern Louisiana. 2.,Although total species richness varied among rivers, species diversity (as estimated both by Shannon-Weaver H, and rank-abundance curves) was fairly similar. 3.,Assemblage composition varied among the rivers, with the West Pearl River having the most dissimilar group of species. The endangered inflated heel splitter, Potamilus inflatus, was found only in the lower Amite River. 4.,The most common species had size distributions skewed towards larger individuals, but small individuals were collected (including the inflated heel splitter), indicating successful recruitment. 5.,Mussels were more common in silt than in sand or gravel, perhaps because fine sediments are more stable through time in these river systems. 6.,The greatest threat to these assemblages is gravel mining in the upper reaches of the rivers. At the present time only rivers with endangered species, or that have been declared scenic rivers, have any protection from gravel mining. Copyright © 2001 John Wiley & Sons, Ltd. [source] Recruiting older adults to health research studies: A systematic reviewAUSTRALASIAN JOURNAL ON AGEING, Issue 3 2009Josephine Auster Aim:, To provide a systematic review of papers comparing the effectiveness of different strategies to recruit older adults (aged 50 years and over) to participate in health research studies, to guide successful recruitment in future research. Methods:, Four major databases were searched for papers published between 1995 and 2008 with: target group aged 50 years or over; participants allocated to receive one of two or more recruitment strategies; and an outcome measure of response rate or enrolment in study. Results:, Twelve papers were included in the review. Conclusion:, For postal questionnaires, recruitment strategies used with older adults had comparable outcomes to those used to recruit from the general population. For other types of studies, strategies involving face-to-face contact may be more effective than indirect methods, but this needs to be balanced against feasibility. Overall, little evidence on the topic exists and more rigorous investigation is necessary. [source] Succession and Micro-elevation Effects on Seedling Establishment of Calophyllum brasiliense Camb. (Clusiaceae) in an Amazonian River Meander Forest1BIOTROPICA, Issue 4 2003Rachel T. King ABSTRACT I investigated the effects of successional stage and micro-elevation on seedling establishment of Calophyllum brasiliense (Clusiaceae), a common canopy tree of seasonally flooded lowland forest along the Manú River meander zone in southeastern Peru. To compare seedling establishment between microhabitat types, I planted C. brasiliense seeds in a fully crossed experimental design of three successional stages (early, mid, and mature) and two micro-elevations (levees and backwaters). Seedling establishment success in this study was affected by both successional stage and micro-elevation, but micro-elevation was most important in mid-successional habitats. In general, seedlings in early succession experienced better conditions than in mature forest; light levels were higher, herbivory lower, and seedling growth higher. In mid-successional forest, micro-elevation determined habitat quality; backwaters had higher light levels, lower herbivory, and higher seedling growth and survival than levees. Mid-successional backwaters were similar in quality to early successional forest for seedling establishment, while levees in that same successional stage were the poorest microhabitats for establishment. Although mid-successional backwaters are similar to early succession for seedling establishment, in the long run, seedlings that establish in mid-succession have a lower chance of reaching reproductive size before their habitat ages to mature forest than members of their cohort that established in early succession. I hypothesize that successful recruitment for C. brasiliense in the Manú River meander system requires dispersal to early successional habitat. RESUMEN Yo investingé el efecto de microhábitats del sistema serpentine ribereño, los cuales se diferencian en estado sucesional y en microelevación, en el establecimiento de plántulas de Calophyllum brasiliense (Clusiaceae), un árbol común en bosques estacionalmente inundados alrededor de los meandros del Río Manú en Perú. Para comparar establecimiento de plántulas entre los microhábitats, sembré semillas de C. brasiliense en seis condiciones de microhábitat, combinando los efectos de tres estados sucesionales (bosque temprano, mediano, y maduro) y dos microelevaciones (lomos y depresiones). El establecimiento de plántulas en este estudio fue afectado por estado sucesional y por microelevación, pero microelevación fue más importante en sucesión mediana. En general, plántulas en sucesión temprana tenían mejores condiciones que plántulas de bosque maduro; niveles de luz más altos, menor herbivoría, y una mayor tasa de crecimiento. En sucesión mediana, microelevacion determinó calidad de hábitat; depresiones presentaron más luz, menos herbivoria, y mayor crecimiento y sobreviviencia de plántulas que los lomos. Depresiones en sucesión mediano fueran similares en calidad a sucesión temprano en cuanto al establecimiento de plántulas, mientras que lomos en este mismo estado sucesional fueron los peores microhábitats para establecimiento. A largo plazo, las plántulas establecidas en sucesión mediano tienen menos probabilidad de alcanzar el tamaño reproductive (antes de que el hábitat llega a ser bosque maduro) que las plántulas de la misma edad, establecidas en sucesión temprana. El reclutamiento efectivo de C. brasiliense en el sistema serpentino del Río Manú probablemente requiere la dispersión al hábitat de sucesión temprana. [source] | |||||||||||||