Academic literature on the topic 'Migratory Obstacles'
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Journal articles on the topic "Migratory Obstacles"
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Castro-Santos, Theodore, and Alex Haro. "Quantifying migratory delay: a new application of survival analysis methods." Canadian Journal of Fisheries and Aquatic Sciences 60, no. 8 (2003): 986–96. http://dx.doi.org/10.1139/f03-086.
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Statistical techniques commonly used in fish passage research fail to adequately quantify delays incurred at obstacles, or the effects of modifications to those obstacles on passage rates. Analyses of telemetry data describing these effects can be misleading, particularly when passage route of some individuals is not established (e.g., because of mortality, tag failure, passage through unmonitored or alternate routes, etc.). Here, we demonstrate how event-time analysis, better known as survival analysis, can be used to quantify passage rates for any study that allows tracking of individuals through time, even when some individuals fail to pass the route or obstacle in question. We review two of the primary methods of event-time analysis (parametric and Cox's proportional hazards regression analyses) and use them in combination with logistic regression to provide unbiased estimates of delay incurred at a hydroelectric facility, as well as insights on factors affecting both rates of passage and route selection. Passage rate increased with increased depth of a surface bypass sluice gate and, among fish that passed through the turbines, with turbine flow. The data further indicate that risk of turbine passage increased with both delay and turbine flow.
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Schubert, Herman D., Kunyan Kuang, Fengying Kang, Mark W. Head, and Jorge Fischbarg. "Macular holes: migratory gaps and vitreous as obstacles to glial closure." Graefe's Archive for Clinical and Experimental Ophthalmology 235, no. 8 (1997): 523–29. http://dx.doi.org/10.1007/bf00947011.
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Jasso Vargas, Rosalba. "Espacios de estancia prolongada para la población migrante centroamericana en tránsito por México." Frontera norte 33 (January 1, 2021): 1–34. http://dx.doi.org/10.33679/rfn.v1i1.2075.
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The objective of this article is to identify the main areas where Central American migrants spend most of their time during their transit through Mexico. The theoretical framework reviews the mobility-immobility and aspiration/ability approaches that focus on mobility restrictions and waiting times. The definition of waiting territories and the inclusion of the length of stay variable contribute to the study of transit migration from the perspective of immobility. Using the Migration Survey in the Northern Border (Emif Sur), the magnitude of displacements through the reported areas by migrants is estimated as having the longest length of stay in their migratory displacement. Long-term transit spaces correspond to different border regions and locations close to migratory routes. The provided empirical evidence indirectly suggests obstacles to mobility manifested in long- term transit spaces.
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Burnside, Robert J., Claire Buchan, Daniel Salliss, Nigel J. Collar, and Paul M. Dolman. "Releases of Asian houbara must respect genetic and geographic origin to preserve inherited migration behaviour: evidence from a translocation experiment." Royal Society Open Science 7, no. 3 (2020): 200250. http://dx.doi.org/10.1098/rsos.200250.
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Maintaining appropriate migratory strategies is important in conservation; however, translocations of migratory animals may alter locally evolved migration behaviours of recipient populations if these are different and heritable. We used satellite telemetry and experimental translocation to quantify differences and assess heritability in migration behaviours between three migratory Asian houbara ( Chlamydotis macqueenii ) breeding populations (640 km range across eastern, central and western Uzbekistan). Adults from the eastern population migrated twice as far (mean = 1184 km ± 44 s.e.) as the western population (656 km ± 183 s.e.) and showed significantly less variation in migration distance than the central population (1030 km ± 127 s.e.). The western and central populations wintered significantly further north (mean: +8.32° N ± 1.70 s.e. and +4.19° N ± 1.16 s.e., respectively) and the central population further west (−3.47° E ± 1.46 s.e.) than individuals from the eastern population. These differences could arise from a differing innate drive, or through learnt facultative responses to topography, filtered by survival. Translocated birds from the eastern population (wild-laid and captive-reared, n = 5) migrated further than adults from either western or central recipient populations, particularly in their second migration year. Translocated birds continued migrating south past suitable wintering grounds used by the recipient populations despite having to negotiate mountain obstacles. Together, this suggests a considerable conserved heritable migratory component with local adaptation at a fine geographic scale. Surviving translocated individuals returned to their release site, suggesting that continued translocations would lead to introgression of the heritable component and risk altering recipient migration patterns. Conservation biologists considering translocation interventions for migratory populations should evaluate potential genetic components of migratory behaviour.
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Lin, Huai-Ti, Ivo G. Ros, and Andrew A. Biewener. "Through the eyes of a bird: modelling visually guided obstacle flight." Journal of The Royal Society Interface 11, no. 96 (2014): 20140239. http://dx.doi.org/10.1098/rsif.2014.0239.
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Various flight navigation strategies for birds have been identified at the large spatial scales of migratory and homing behaviours. However, relatively little is known about close-range obstacle negotiation through cluttered environments. To examine obstacle flight guidance, we tracked pigeons ( Columba livia ) flying through an artificial forest of vertical poles. Interestingly, pigeons adjusted their flight path only approximately 1.5 m from the forest entry, suggesting a reactive mode of path planning. Combining flight trajectories with obstacle pole positions, we reconstructed the visual experience of the pigeons throughout obstacle flights. Assuming proportional–derivative control with a constant delay, we searched the relevant parameter space of steering gains and visuomotor delays that best explained the observed steering. We found that a pigeon's steering resembles proportional control driven by the error angle between the flight direction and the desired opening, or gap, between obstacles. Using this pigeon steering controller, we simulated obstacle flights and showed that pigeons do not simply steer to the nearest opening in the direction of flight or destination. Pigeons bias their flight direction towards larger visual gaps when making fast steering decisions. The proposed behavioural modelling method converts the obstacle avoidance behaviour into a (piecewise) target-aiming behaviour, which is better defined and understood. This study demonstrates how such an approach decomposes open-loop free-flight behaviours into components that can be independently evaluated.
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Amoretti, Guido. "Psychological obstacles to multiculturalism: how stereotypes and mechanisms of defence may cause adverse behaviours to multiculturalism." Geopolitical, Social Security and Freedom Journal 1, no. 1 (2018): 61–69. http://dx.doi.org/10.2478/gssfj-2018-0003.
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Abstract Migration flows are part of human history. The process of globalization, if on the one hand it seems to favour the movement of human beings, on the other hand it is creating the conditions for the recovery of migratory flows, especially within some areas of the world and, in part, directed towards advanced development countries. This creates problems of acceptance on the part of the host with respect to the customs and habits of the guest. Resistance to reception, used for political ends by populist parties, has deep roots that have to do with psychological and social factors: defence mechanisms, stereotypes and prejudices. The article stresses the importance of training in overcoming these obstacles to building a society that is first multicultural and then intercultural.
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Erdelen, Walter R., and Jacques G. Richardson. "Human migration: managing its increasing complexity." foresight 22, no. 1 (2019): 109–26. http://dx.doi.org/10.1108/fs-02-2019-0007.
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Purpose This paper aims to discuss the history of human migration till the present day. Design/methodology/approach The authors analyze the human movement from pre-hominid times, forming patterns of existence. Thus, ambient sun and water, weather and climate extremes, shelter, food supply, natural or human-made disasters gave rise to Homo sapiens’ wanderlust. Findings Despite obstacles, formidable barriers and even perilous deterrents, the species explored and exploited new soils and waters, whether beneficial or destructive of nature’s ample providence. Originality/value The authors treat societal as well as individual action, cultural behavior and the emergence of economic anthropology. Migratory legislation and regulation now risk transformation into resentment and then xenophobia.
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Makrakis, Sergio, Ana P. S. Bertão, Jhony F. M. Silva, Maristela C. Makrakis, Fco Javier Sanz-Ronda, and Leandro F. Celestino. "Hydropower Development and Fishways: A Need for Connectivity in Rivers of the Upper Paraná Basin." Sustainability 11, no. 13 (2019): 3749. http://dx.doi.org/10.3390/su11133749.
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South American rivers have become intensely affected by the construction of hydroelectric dams that block the river’s connectivity for migratory fish species. In order to mitigate the problems caused by dams and to reestablish connections between habitats, fishways are implemented. Fishways are structures that aid fish in overcoming obstacles and help preserve migratory, reproductive, and feeding routes. This study performed an inventory of all hydropower plants—present and future—in the Upper Paraná River, with the objective of identifying fishways unknown to scientific literature, as well as the task of mapping them. By doing so, the current situation of structural connectivity via fishways in the Upper Paraná River Basin was described. Overall, 389 dams along 209 rivers were identified; of these, only 9% (35 dams) have fishways. In addition, an alarming explosion of future medium-sized hydropower plants was observed, with an expectation of an almost 500% increase in relation to those existing. This data reveals a trend of reduction of free-flowing river stretches, which are crucial habitats for Neotropical potamodromous species, and point to a deficiency in the structural connectivity of existing hydropower dams. Furthermore, if the implementations of these expected constructions are associated with limited connectivity as a result of the absence of fishways, the management of fisheries and their resources in the Upper Paraná River may become unsustainable.
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Gurgel, Liliane de Lima, José Roberto Verani, and Sathyabama Chellappa. "Reproductive Ecology ofProchilodus brevisan Endemic Fish from the Semiarid Region of Brazil." Scientific World Journal 2012 (2012): 1–7. http://dx.doi.org/10.1100/2012/810532.
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The commercially important migratory fishProchilodus brevisis from the Neotropical region, and understanding the reproductive ecology of this potamodromous fish is essential for its conservation and management. This study investigated the length-mass relationship, sex ratio, length at first gonadal maturity, gonadal development stages, gonadosomatic index, condition factor, and reproductive period ofP. brevis. Temporal distribution of rainfall, temperature, dissolved oxygen concentration, pH, and electrical conductivity of the water were related to the reproductive period of this fish. Rainfall seems to be the main environmental factor which modulates changes in limnological parameters and the timing of the spawning period of this fish.P. brevismigrates into lower reaches of the river to feed during the dry season and returns to the upper reaches during the rainy season to spawn. Inadequate facilities for migration create obstacles for spawning success of this ecologically important fish.
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Godfrey, Jason D., David C. Stewart, Stuart J. Middlemas, and John D. Armstrong. "Depth use and migratory behaviour of homing Atlantic salmon (Salmo salar) in Scottish coastal waters." ICES Journal of Marine Science 72, no. 2 (2014): 568–75. http://dx.doi.org/10.1093/icesjms/fsu118.
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Abstract Knowledge of swimming depths and migration routes of homing Atlantic salmon in open coastal zones is urgently required to inform decisions on managing the species, e.g. for the sustainable development of marine renewable energy. In May–June 2013, pop-up satellite tags programmed to detach from fish after 1–10 d were fitted to 50 adult salmon on the northern coast of Scotland. Most of the tags returned water depth recorded at regular intervals (n = 47) and gave a geographic location following detachment (n = 44). In general, salmon were found near the surface during the study, with the median number of records at 0–5 m depth ranging from 72 to 85%, depending on the extent of known potential systematic bias. Depth use varied among individuals (8–100% at 0–5 m) and cluster analysis suggested that the sample of fish could be split into two groups, representing different patterns of depth use. These clusters were also associated with pop-up location. There was a small but significant increase in recorded depth at night compared with during the day, contrasting with findings of salmon at sea in other contexts. The mean maximum dive depth was 64 m (range 13–118 m), of similar order to the likely available water column depth. These results suggest that salmon will potentially interact with man-made obstacles, e.g. renewable energy generators, throughout the water column and particularly in surface waters.
Dissertations / Theses on the topic "Migratory Obstacles"
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Gesicki, David V. "The Influence of Topography, Wind, and Time of Night on Migratory Songbird Orientation along the Southwest Coast of Lake Erie." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu152845051093791.
Full textBook chapters on the topic "Migratory Obstacles"
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Stock, Inka. "Travelling Adventures: Migration as an Existential Quest." In Time, Migration and Forced Immobility. Policy Press, 2019. http://dx.doi.org/10.1332/policypress/9781529201970.003.0003.
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This chapter focuses on migrants’ journeys from their countries of origin to Morocco. The text analyses how phases of mobility and immobility are interdependent parts of the complex migration trajectories of my migrant research subjects. It explores the variety of obstacles that migrants encounter during travel towards Morocco, and the ways in which they continue to negotiate their social locations with respect to mobility along the way. By reviewing the variety of regulatory authorities (market, state and family) that structure their movement, I will show how aspirations and capabilities to migrate are produced and reproduced not only at the point of departure, but also along the way. Thus, rather than transiting through different places, the data shows how migrants’ journeys are best described as “fractured stays” in various places. These stays and the ways in which people travel do not leave them unchanged. Instead, it has a profound impact on themselves and their future migratory project. The migratory experience becomes a way of life which influences every other aspect of their identit
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"Advances in Fisheries Bioengineering." In Advances in Fisheries Bioengineering, edited by Richard W. Zabel, Brian J. Burke, Mary L. Moser, and Christopher A. Peery. American Fisheries Society, 2008. http://dx.doi.org/10.47886/9781934874028.ch10.
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<em>Abstract.</em>—Although many hydroelectric dams have fishways for upstream passage of migratory fish, passage delays often occur at these sites. Migrational delay may affect fish detrimentally in several ways, including depletion of energy reserves, suboptimal arrival timing at spawning sites, and prolonged exposure to hazardous conditions at the face of dams. We applied time-to-event analyses to passage times of radio-tagged adult Chinook salmon <em>Oncorhynchus tshawytscha </em>at four dams on the lower Columbia River, where many fish require several days to pass each dam. The analysis allowed us to determine instantaneous passage rates in response to fluctuating river conditions. By relating variability in passage rate to the predictor variables river temperature, river flow, and fish size, we determined the relative contribution of various factors to the passage time of migrating fish. We fit the model by maximizing the likelihood function that incorporated information from individuals rather than aggregated groups of fish. We used Akaike’s Information Criterion to distinguish among several competing models, each of which used a different predictor variable. We found that daytime passage rates were significantly greater than nighttime passage rates. Also, the influence of river flow, river temperature, and fish length on passage rates varied at the four dams. However, when a factor had a significant influence on passage time, the direction of the relationship was consistent across dams: river flow and fish length were positively related to passage time (greater values led to longer passage time), and river temperature was negatively related. This method is easily adaptable to study passage time of any fish population facing a broad range of obstacles to migration, whether natural or man-made.
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"Advances in Fisheries Bioengineering." In Advances in Fisheries Bioengineering, edited by Richard W. Zabel, Brian J. Burke, Mary L. Moser, and Christopher A. Peery. American Fisheries Society, 2008. http://dx.doi.org/10.47886/9781934874028.ch10.
Full textAbstract:
<em>Abstract.</em>—Although many hydroelectric dams have fishways for upstream passage of migratory fish, passage delays often occur at these sites. Migrational delay may affect fish detrimentally in several ways, including depletion of energy reserves, suboptimal arrival timing at spawning sites, and prolonged exposure to hazardous conditions at the face of dams. We applied time-to-event analyses to passage times of radio-tagged adult Chinook salmon <em>Oncorhynchus tshawytscha </em>at four dams on the lower Columbia River, where many fish require several days to pass each dam. The analysis allowed us to determine instantaneous passage rates in response to fluctuating river conditions. By relating variability in passage rate to the predictor variables river temperature, river flow, and fish size, we determined the relative contribution of various factors to the passage time of migrating fish. We fit the model by maximizing the likelihood function that incorporated information from individuals rather than aggregated groups of fish. We used Akaike’s Information Criterion to distinguish among several competing models, each of which used a different predictor variable. We found that daytime passage rates were significantly greater than nighttime passage rates. Also, the influence of river flow, river temperature, and fish length on passage rates varied at the four dams. However, when a factor had a significant influence on passage time, the direction of the relationship was consistent across dams: river flow and fish length were positively related to passage time (greater values led to longer passage time), and river temperature was negatively related. This method is easily adaptable to study passage time of any fish population facing a broad range of obstacles to migration, whether natural or man-made.