770 resultados para heterothermy index


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Details are given of the development of a bioeconomic culture index that may be used to assist in choosing fish for culture. This index takes into account growth performance indexes and mean annual prices of the fish. Examples are given of the culture indices of some of Kuwait's commercially important fish species. The proposed indices given realistic output for these fish and allow comparison and evaluation of different taxa with widely differing biological and economic characteristics.

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A fishery-independent assessment of juvenile coastal shark populations in U.S. waters of the northeast Gulf of Mexico was conducted using two methods: gillnets and longlines. Surveys were conducted monthly during April–October in two fixed sampling areas from 1996 to 1998. The Atlantic sharpnose shark, Rhizoprionodon terraenovae, and the blacktip shark, Carcharhinus limbatus, were the most common species captured with either longlines or gillnets. An additional 14 shark species were captured, and juvenile indices of abundance were developed for 8 species with gillnets and 6 species of sharks with longlines. Trends in catch-per-unit-effort were found to vary depending on species. Length-frequency information revealed that the majority of sharks captured were juveniles. Given the direct relationship between stock and recruitment for sharks, continued monitoring of juvenile abundance will aid in determining the strength of the parental stock size and for predicting future population strength.

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With current and anticipated increases in magnitude of extreme weather events and a declining consistency in weather patterns, particularly challenging for agriculture, there has been a growing interest in weather index-based insurance (IBI) schemes in Bangladesh. A number of weather index-based insurance products have already been tested and applied across Asia and Africa, with varying degrees of success, as a mechanism to improve livelihood security by enabling vulnerable populations to transfer risk associated with climate change, extreme weather events and other hazards. In the process, these efforts have generated important new knowledge on how these schemes can be designed and implemented for optimal results. However, the practice of index-based insurance is still limited in Bangladesh, and the experience and knowledge generated by the different stakeholders involved needs to be better communicated.

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A normalized difference vegetation index (NDVI) has been produced and archived on a 1° latitude by 1° longitude grid between 55°S and 75°N. The many sources of data errors in the NDVI include cloud contamination, scan angle biases, changes in solar zenith angle, and sensor degradation. Week-to-week variability, primarily caused by cloud contamination and scan angle biases, can be minimized by temporally filtering the data. Orbital drift and sensor degradation introduces interannual variability into the dataset. These trends make the usefulness of a long-term climatology uncertain and limit the usefulness of the NDVI. Elimination of these problems should produce an index that can be used for climate monitoring.

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WorldFish and the International Centre for Climate Change and Development (ICCCAD) held a two-day workshop on the topic of Weather Index-Based Insurance: Lessons Learned and Best Practices for Bangladesh. Weather index insurance is based on a predefined weather event which when triggered ensures automatic payout to farmers who have taken out insurance. For example, the climatic trigger could be a predefined consecutive number of days where rainfall is below a set level or when the floodwater level reaches above a certain point. Index insurance has been operating for about 10 years in many countries but is still at an early stage in Bangladesh, where there are two schemes currently being piloted and three other projects being developed. The aim of the two-day workshop was twofold: to ascertain the present state of index insurance in Bangladesh and elsewhere, and to work together to identify ways forward.

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Annual radiolarian flux (1954-1986) extrapolated from varved Santa Barbara Basin sediments was compared to instrumental data to examine the effect of interannual climate variability. Paleo-reconstructions over large geographic areas or 10^3 years and longer typically rely on changes in species composition to signal environment or climate shifts. In the relatively short period studied, climate fluctuations were insufficient to significantly alter the assemblage, but there was considerable variability in the total flux of radiolarians. This variability, greatest on 5- to 25-year time scales, appears to be linked to regional climate variability. Total flux correlates to regional California sea surface temperature and the composite of sea level pressure over the Northern Hemisphere for years of high radiolarian flux resembles positive PNA circulation.