15 resultados para Lunar theory.

em Aquatic Commons


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From a manager’s perspective, oftentimes the publicly held concerns related to small docks and piers are not really related to the environment. They may be more related to visual impacts and aesthetic concerns, a sense of over-development of the shore, or simply change. While individuals may hold personal aesthetic values related to small docks in general or an individual structure in particular, techniques have evolved that appear to provide reproducible, predictive assessments of the visual impacts and aesthetic values of an area and how those might change with development, including an increase in numbers of small docks. These assessments may be used to develop regulatory or non-regulatory methods for the management of small docks based on state or community standards. Visual impact assessments are increasingly used in the regulatory review of proposed development—although this process is still in its infancy as regards small docks and piers. Some political jurisdictions have established visual impact or aesthetic standards as relate to docks and others are in the process of investigating how to go about such an effort. (PDF contains 42 pages)

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Monthly catches of the Macrobrachium fisheries were recorded at a commercial shrimp landing site on the coasts of Calabar (Nigeria), from April 1997 to August 1998. Catches fluctuated over an annual cycle, with two peaks occurring from May-July and November-December. These peaks represented periods of major activities, reproduction, recruitment or migration. Also, mean catches decreased in the months of February and August, corresponding to the peak of dry season and the so-called 'August break', respectively. Catches from active gears (seine, push net) varied among the moon phases too, with a main peak during full moon, and the minimum catch was recorded during the first moon quarter. However, the catch from passive gear (trap) depicted an inverse relationship, showing a peak during the first moon quarter. Variation in catches at different months and moon phases were significant at P:0.05. Recognize these variations and trends would help in management decisions such as defining closed seasons without adversely affecting the economy of the fishers

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The foundation of Habermas's argument, a leading critical theorist, lies in the unequal distribution of wealth across society. He states that in an advanced capitalist society, the possibility of a crisis has shifted from the economic and political spheres to the legitimation system. Legitimation crises increase the more government intervenes into the economy (market) and the "simultaneous political enfranchisement of almost the entire adult population" (Holub, 1991, p. 88). The reason for this increase is because policymakers in advanced capitalist democracies are caught between conflicting imperatives: they are expected to serve the interests of their nation as a whole, but they must prop up an economic system that benefits the wealthy at the expense of most workers and the environment. Habermas argues that the driving force in history is an expectation, built into the nature of language, that norms, laws, and institutions will serve the interests of the entire population and not just those of a special group. In his view, policy makers in capitalist societies are having to fend off this expectation by simultaneously correcting some of the inequities of the market, denying that they have control over people's economic circumstances, and defending the market as an equitable allocator of income. (deHaven-Smith, 1988, p. 14). Critical theory suggests that this contradiction will be reflected in Everglades policy by communicative narratives that suppress and conceal tensions between environmental and economic priorities. Habermas’ Legitimation Crisis states that political actors use various symbols, ideologies, narratives, and language to engage the public and avoid a legitimation crisis. These influences not only manipulate the general population into desiring what has been manufactured for them, but also leave them feeling unfulfilled and alienated. Also known as false reconciliation, the public's view of society as rational, and "conductive to human freedom and happiness" is altered to become deeply irrational and an obstacle to the desired freedom and happiness (Finlayson, 2005, p. 5). These obstacles and irrationalities give rise to potential crises in the society. Government's increasing involvement in Everglades under advanced capitalism leads to Habermas's four crises: economic/environmental, rationality, legitimation, and motivation. These crises are occurring simultaneously, work in conjunction with each other, and arise when a principle of organization is challenged by increased production needs (deHaven-Smith, 1988). Habermas states that governments use narratives in an attempt to rationalize, legitimize, obscure, and conceal its actions under advanced capitalism. Although there have been many narratives told throughout the history of the Everglades (such as the Everglades was a wilderness that was valued as a wasteland in its natural state), the most recent narrative, “Everglades Restoration”, is the focus of this paper.(PDF contains 4 pages)

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In recent years coastal resource management has begun to stand as its own discipline. Its multidisciplinary nature gives it access to theory situated in each of the diverse fields which it may encompass, yet management practices often revert to the primary field of the manager. There is a lack of a common set of “coastal” theory from which managers can draw. Seven resource-related issues with which coastal area managers must contend include: coastal habitat conservation, traditional maritime communities and economies, strong development and use pressures, adaptation to sea level rise and climate change, landscape sustainability and resilience, coastal hazards, and emerging energy technologies. The complexity and range of human and environmental interactions at the coast suggest a strong need for a common body of coastal management theory which managers would do well to understand generally. Planning theory, which itself is a synthesis of concepts from multiple fields, contains ideas generally valuable to coastal management. Planning theory can not only provide an example of how to develop a multi- or transdisciplinary set of theory, but may also provide actual theoretical foundation for a coastal theory. In particular we discuss five concepts in the planning theory discourse and present their utility for coastal resource managers. These include “wicked” problems, ecological planning, the epistemology of knowledge communities, the role of the planner/ manager, and collaborative planning. While these theories are known and familiar to some professionals working at the coast, we argue that there is a need for broader understanding amongst the various specialists working in the increasingly identifiable field of coastal resource management. (PDF contains 4 pages)

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The role of life-history theory in population and evolutionary analyses is outlined. In both cases general life histories can be analysed, but simpler life histories need fewer parameters for their description. The simplest case, of semelparous (breed-once-then-die) organisms, needs only three parameters: somatic growth rate, mortality rate and fecundity. This case is analysed in detail. If fecundity is fixed, population growth rate can be calculated direct from mortality rate and somatic growth rate, and isoclines on which population growth rate is constant can be drawn in a ”state space” with axes for mortality rate and somatic growth rate. In this space density-dependence is likely to result in a population trajectory from low density, when mortality rate is low and somatic growth rate is high and the population increases (positive population growth rate) to high density, after which the process reverses to return to low density. Possible effects of pollution on this system are discussed. The state-space approach allows direct population analysis of the twin effects of pollution and density on population growth rate. Evolutionary analysis uses related methods to identify likely evolutionary outcomes when an organism's genetic options are subject to trade-offs. The trade-off considered here is between somatic growth rate and mortality rate. Such a trade-off could arise because of an energy allocation trade-off if resources spent on personal defence (reducing mortality rate) are not available for somatic growth rate. The evolutionary implications of pollution acting on such a trade-off are outlined.

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Commercial longline fishing data were analyzed and experiments were conducted with gear equipped with hook timers and timedepth recorders in the Réunion Island fishery (21°5ʹS lat., 53°28ʹE long.) to elucidate direct and indirect effects of the lunar cycle and other operational factors that affect catch rates, catch composition, fish behavior, capture time, and fish survival. Logbook data from 1998 through 2000, comprising 2009 sets, indicated that swordfish (Xiphias gladius) catch-per unit of effort (CPUE) increased during the first and last quarter of the lunar phase, whereas albacore (Thunnus alalunga) CPUE was highest during the full moon. Swordfish were caught rapidly after the longline was set and, like bigeye tuna (Thunnus obesus), they were caught during days characterized by a weak lunar illumination—mainly during low tide. We found a significant but very low influence of chemical lightsticks on CPUE and catch composition. At the time the longline was retrieved, six of the 11 species in the study had >40% survival. Hook timers indicated that only 8.4% of the swordfish were alive after 8 hours of capture, and two shark species (blue shark [Prionace glauca] and oceanic whitetip shark [Carcharhinus longimanus]) showed a greater resilience to capture: 29.3% and 23.5% were alive after 8 hours, respectively. Our results have implications for current fishing practices and we comment on the possibilities of modifying fishing strategies in order to reduce operational costs, bycatch, loss of target fish at sea, and detrimental impacts on the environment.

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Spawning periodicities of white seabass (Atractoscion nobilis) were evaluated by observing spawning behavior, by collecting eggs, and monitoring recognizable sounds produced during the release of gametes. A total of 297 spawning events were documented from 15 male and 47 female white seabass contained within the seminatural confines of a 526-m3 net pen located in Catalina Harbor, Santa Catalina Island, California. Consistent spawning occurred from March through July 2001−03, and peaked in May at a photoperiod of 14 hours. Most spawning occurred within the 2-hour period following sunset or from 19:00−20:00 hours Pacific Standard Time. White seabass spawned at every phase of the lunar cycle; but an increase in successive spawning events followed the new moon. Most spawning occurred in water temperatures from 15 to 18°C, and there was no apparent correlation with tidal cycles. Seasonal and diel spawning periods were directly correlated with increases in the rate, intensity, and variety of white seabass sounds; this correlation may indicate that sounds function to enhance reproductive success. These findings can be extended to further develop seasonal fishery regulations and to better comprehend the role of sound in the reproduction of sound-producing fishes.

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The CGIAR Strategy and Results Framework sets out four system level outcomes (SLOs), namely: reducing rural poverty, improving food security, improving nutrition and health and sustainable management of natural resources. In pursuit of these objectives the CGIAR has developed a set of sixteen CGIAR Research Programs (CRPs), each of which is expected to make specific contributions to a range of intermediate development outcomes (IDOs) linked to the SLOs. As part of this work the CRPs are developing impact pathways and theories of change designed to explain how the programs will achieve IDOs. The purpose of the present paper is to explain the approach that the CRP on Aquatic Agricultural Systems (AAS) is taking to using these programmatic tools to help achieve impact.

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Preliminary investigations to study the lunar, diurnal and tidal periodicity in abundance and migrations of prawns were made in the Bairavapalam distributary of the Goutami branch of the Godavari estuary during the period of November 1961 to July 1962. The study was based on observation of the catches of a stake net (bag net) operated near the mouth of the estuary. Records of the catches were maintained tidewise daily. Comparative estimates of abundance were made on the basis of catch per hour's operation. It was generally observed that the catches were higher during the darker half of the month than in the brighter fortnight. The landings during low tides were generally higher than those during high tides and usually heavier catches were made during nocturnal low tides than during the day low tides. A continuous inward and outward (immigration and emigration) movement of prawns of all size groups was observed in the estuary from November to July. In general, more penaeid prawns were found to be immigrating at dawn than at dusk. Similarly, the number of emigrants was also found to be generally higher during the new moon period than during the full moon. Metapenaeus monoceros showed an almost distinct nocturnal periodicity in migration, while no such periodicity was observed, distinctly, in other species. In the case of Penaeus indicus the movement of migrants was prolonged. In M. brevicornis the migrants were scarce till March and thereafter increased numerically. The migrant forms of Metapenaeus dobsoni continued to be abundant till May with peak periods in January and February. The migratory pattern of Metapenaeus affinis was similar to that of Metapenaeus brevicornis, though the migrants of the former species appeared a month earlier than the latter. Intensive studies over extended areas for longer periods are required to understand clearly the migratory pattern of the various species. The phenomenon of immigration of prawns can be clearly understood only by vital staining or tagging studies. Perhaps the emigrants might be returning with the succeeding changing life. To verify this, laboratory experiments, by vital stains, were conducted. The marked specimens, if released during the low tides on a large scale, may be recaptured during the subsequent high tides and the duration also may be calculated. At least some percentage of the emigrants remains in the sea for maturity and breeding.

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The effect of lunar and tidal influence on the landing of pelagic fish with drift gill nets has been studied for the first time from Bay of Bengal along the Orissa coast. The catchability of the gear was highest during the first quarter and lowest in the fourth quarter of the moon. The variation in catch rates during the four different quarters was not statistically significant. Contrary to the earlier belief, landing with gill net was not poor during the moonlit nights. The extensive use of bluish grey nylon twine matching with seawater in place of indigenous hemp or cotton twine, has largely eliminated the visibility of gear during the brighter phase of the moon. The rate of exploitation was found to be significantly higher during the nights of neap tide, compared to those of spring tide. A plausible explanation for this phenomenon has been offered.

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The paper deals with the lunar and tidal influences on the catches of seer by gill nets. The landings during full moon and new moon nights, during low and high tides and during different quarters of the lunar month for three fishing seasons are discussed.