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While stocking floodplain depressions or beels with fingerlings is a common form of fisheries management in Bangladesh, bio‐economic guidance for improving the outcome of stocking strategies is sparse. The Community‐Based Fisheries Management (CBFM) Project, funded by the Ford Foundation and the UK Government's Department for International Development (DfID) promoted stocking practices in beels throughout the country as a means to improve fisher livelihoods. This paper describes an empirical bio‐economic model developed using data generated under the CBFM project. The model offers guidance on selecting stocking densities depending upon the available size (length) of fingerlings to maximize profit and return on investment while minimizing risk. Because large fingerlings are relatively inexpensive and have lower rates of natural mortality, the model predicts that it is more profitable to stock large fingerlings at low densities than small fingerlings at high densities. These general recommendations were found to be largely insensitive to the market price for harvested fish. To minimize credit burden and financial risk, minimum stocking densities should be selected according to the length of fish available that maximizes profit. Because of its empirical nature, the model recommendations may not be applicable beyond the project sites. Furthermore, it is recommended that attempts be made to field test the model predictions before widespread adoption or promotion. 相似文献
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Golam Ahmed David Takuwa Inonge T. Chibua Zibisani Bagai Lebogang Morekisi Hilary Shoniwa 《Communications in Soil Science and Plant Analysis》2016,47(4):512-520
An ultrasonic method using two approaches, A and B, along with a reference Environmental Protection Agency (EPA) Method 3050B [i.e., a mixture of 30 mL of nitric acid–hydrochloric acid–hydrogen peroxide–water (HNO3-HCl-H2O2-H2O)] were contrasted for leaching of a plant matrix. The trace metals were arsenic, cadmium, cobalt, chromium, copper, mercury, manganese, nickel, lead, selenium, and zinc (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se and Zn) and quantified by ICP-OES followed by an investigation into residue formation and the impact of digestion time. Approach B was the most accurate and precise with percent recoveries ranging between 99 and 120%, whereas ultrasonic approach A and the USEPA method 3050B gave similar results with poor accuracies and precisions. In the optimization of the digestion time using approach B, the total metal recovery was fairly the same over a period of 120 min except for Cr and Cu, which showed slight variations. 相似文献
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The Relationship Between Pathogen-induced Systemic Resistance (ISR) and Multigenic (horizontal) Resistance in Plants 总被引：2，自引：0，他引：2
Sadik Tuzun 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(1):85-93
Plants have developed mechanisms to successfully co-exist in the presence of pathogenic organisms. Some interactions between plants and pathogens are based on recognition of specific elicitor molecules from avirulent pathogen races (avr gene products), which is described in the gene-for-gene resistance theory. Another type of resistance, multigenic (horizontal) resistance, is a less well-studied phenomenon that depends upon multiple genes in the plant host. All plants possess resistance mechamisms which can be induced upon pre-treatment of plants with a variety of organisms or compounds. This general phenomenon is known as induced systemic resistance (ISR). At least in some plant species, ISR depends on the timely accumulation of multiple gene products, such as hydrolytic enzymes, peroxidases or other gene products related to plant defences. The pre-treatment of plants with an inducing organism or compound appears to incite the plant to mount an effective defense response upon subsequent encounters with pathogens, converting what would have been a compatible interaction to an incompatible one. Our studies in three plant–pathogen systems clearly document that multigenic-resistant plants constitutively express specific isozymes of hydrolytic enzymes that release cell wall elicitors, which in turn may activate other defense mechanisms. ISR induces constitutive accumulation of these and other gene products prior to challenge. ISR is known to function against multiple organisms, and there is no specificity observed in the accumulation patterns of defense-related gene products when ISR is induced. It is therefore hypothesized that the constitutive accumulation of specific isozymes of hydrolytic enzymes, or other defense related gene products, is an integral part of both multigenic resistance and the phenomenon of ISR. Further, plants in which ISR has been activated appear to move from a latent resistance state to one in which a multigenic, non-specific form of resistance is active. 相似文献
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Antimicrobial and cytotoxic constituents of Loranthus globosus 总被引：2，自引：0，他引：2
(+)-Catechin, 3,4-dimethoxycinnamyl alcohol and 3,4,5-trimethoxycinnamyl alcohol were isolated from the barks of Loranthus globosus. All compounds showed significant antimicrobial and cytotoxic activities. 相似文献
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Ten multiparous crossbred local Zebu cows were randomly divided into two nutritional groups (A and B) to determine the effect of urea-molasses-mineral block supplementation on body weight gain, milk production, and onset of ovarian cyclicity after calving. Both groups had farm rations daily, but the supplemented group (B) was provided with an additional diet daily of 250 g urea-molasses-mineral block. The cows in group A required 80-120 days (98.0 +/- 6.7 days) until peak milk progesterone concentrations and 60-80 days (72.0 +/- 3.8 days) were required for group B (p<0.05). Group B needed a shorter period for expression of standing estrus (91-101 days; mean 96.2 +/- 2.3 days) than group A [130-153 (141.6 +/- 4.6) days; p<0.01]. For groups A and B, body weight gain was 8.4 +/- 3.4 kg and 18.4 +/- 3.2 kg, respectively (p<0.01). The average milk production of groups A and B were 3.3 +/- 1.0 and 4.8 +/- 1.6 L/day, respectively (p>0.05). There was linear improvement in milk yield from Day 60 postpartum up to Day 90 of lactation in group B (supplemented). However, in group A, milk production decreased starting on Day 40 after parturition. 相似文献
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Hatchery culture of mud crabs has not yet achieved commercial viability despite decades of research efforts. Further research is therefore needed to better understand larval culture requirements of the crab. Based on anecdotal observations, an experiment was carried out to test whether the background colour of the culture vessel affected larval culture success. Newly hatched larvae of Scylla serrata were reared in culture vessels of five colours, i.e., black, dark green, maroon, sky blue and white. Larval survival and development were monitored daily until all of them either moulted to the first crab stage or died. The results showed clear effects of background colour on larval survival. A general tendency of higher larval survival in darker‐coloured backgrounds was evident. In particular, overall zoeal survival for larvae reared in black vessels was significantly higher than those reared in white ones. Background colour also appeared to affect larval development. Larvae reared in darker backgrounds generally had shorter development times and more synchronized moulting. A significant delay in zoeal development was observed in larvae reared in white vessels. Dark backgrounds possibly facilitated more efficient feeding, reduced settlement of larvae at the bottom of the vessels as well as minimized stress. This result appears to be the first to demonstrate that background colour can significantly affect larval survival and development of a crustacean species. 相似文献
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The aim of this study was to investigate the anatomy of the arterial supply and branches of the thoracic limb of the porcupine. With this aim, five (three male and two female) adult porcupines were used. The vascular tree of the thoracic limb was injected through the common carotid arteries with coloured latex. The a. thoracica externa arose from the a. axillaris at the level of the fourth rib. It divided into two branches and went to the m. cutaneus trunci and the m. pectoralis ascendens. The a. subscapularis came off the a. thoracodorsalis. Later, the a. circumflexa humeri caudalis et cranialis, the three muscular branches and the a. circumflexa scapulae arose from the a. subscapularis. The a. profunda brachii arose together with the a. bicipitalis from the same truncus. The a. collateralis ulnaris left from the a. brachialis independently. Rete carpi dorsale was formed by the a. radialis. the r. carpeus dorsalis of the a. collateralis ulnaris and the a. interossea caudalis. Arcus palmaris profundus was formed by the r. profundus of the a. interossea caudalis and the r. palmaris profundus of the a. radialis. In conclusion, despite a partial resemblance to that in the rat, the distribution of the thoracic limb arteries in the porcupine was found to be completely different from that of other mammals. These findings represent, to our knowledge, the first study on the distribution of thoracic limb arteries in the porcupine. 相似文献
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A trial of Avicennia officinalis L. with five different spacings was conducted in the newly accreted lands along the western coastline(Patuakhali district) of Bangladesh since 1993 to assess growth performance and the effect of spacing on tree growth. Data on tree density, height, diameter, bole height, crown diameter were recorded and analyzed when the stand was 19 years old. Mean height ranged from 12.89-13.52 m and diameter at breast height(dbh) from 26.57-32.16 cm in plots of different spacings. The mean annual height increment ranged from 0.67-0.71 m, mean annual diameter increment from 1.40-1.69 cm and wood volume from 6.02-10.04 m3·ha-1·a-1 in different treatments. Significantly greater diameter(32.16 cm) and wood volume(10.04 m3?ha-1?a-1) were obtained with wider(2.13 m × 2.13 m) spacing than with closer spacings. But tree growth was unaffected by other spacings. Growth data were also recorded from other A. officinalis plantations raised by Forest Department(FD) on different islands in Patuakhali and Bhola districts of Bangladesh. At these sites, mean annual height increment ranged from 0.33-0.62 m, mean annual diameter increment from 0.72-1.37 cm and wood volume from 1.55-5.73 m3?ha-1?a-1. The growth performance of A. officinalis indicated that the newly accreted lands along the western shoreline may be suitable for raising Avicennia plantations for the enrichment of coastal vegetation. 相似文献