Mangrove litter production and seasonality of dominant species in Zanzibar, Tanzania

This study is aimed at examining the litter production and seasonality of Avicennia marina, Bruguiera gymnorhiza, and Rhizophora mucronata. Litter was collected using nylon litter traps of 1 mm2 mesh size in the Uzi-Nyeke mixed mangroves, Zanzibar, over a period of 2 years. Contents were sorted, dried, weighed, and the average daily litter production for each component was calculated. A distinct seasonality and species variation were found in all mangrove litter components. The average annual litterfall rate was higher in B. gymnorhiza, followed by R. mucronata and A. marina (3.0, 2.8, and 2.0 ton dry wt. ha-1year–1 respectively). Leaf fraction was the main component of litter in all species, but fruit and flower for R. mucronata also had a considerable contribution to the total litterfall. The presented patterns of litter production are associated with average temperature and wind speed which are both strongly correlated with litter seasonality. Our data contributes to the body of knowledge on  patterns of litter production and the ecological integrity of mangrove forests in Zanzibar.Keywords: Litterfall, mangrove species, seasonal pattern

Foreign Exchange Rate Transaction Exposure in Emerging Insurance Markets: A Model of the Egyptian Insurance Market.

Emerging insurance markets, have limited access to financial instruments that they can use to create common hedge(s) to manage foreign exchange risk. This is the first empirical study to focus on the limitations when modelling foreign exchange rate transaction exposure in emerging insurance markets. This work is based on the cash flow methodology proposed by Martin and Mauer (2003, 2005) in reference to banks, and employed by Li et al. (2009) when assessing US insurance companies. Some econometric methodological innovations have been introduced to study the limitations of modelling foreign exchange rate transaction exposure in emerging insurance markets. An extensive literature review is followed by a quantitative investigation, to answer the following research questions. 1) Is the foreign exchange transaction exposure, as measured by a fundamental (economic) method of modelling the interplay of foreign exchange rates with other economic variables, significant, for all Egyptian insurance companies? 2) Is the foreign exchange transaction exposure, as measured by a technical (statistical) way of modelling the interplay of foreign exchange rates with other economic variables, significant for all Egyptian insurance companies? 3) Is the exchange transaction exposure for the Egyptian insurance industry, as a whole, significant? Although the foreign exchange rate transaction exposure for the Egyptian insurance industry, as a whole, is insignificant (question3), the percentage of Egyptian insurers affected by foreign exchange rate transaction exposure in US dollars, estimated at the individual firm level, was found to be 22% (question 1) and 35% (question2) respectively

The Effects of Extended Depletion Region on Noise Modeling of HEMT ’s

In this paper we present a high frequency noise model for short channel HEMTs.This model takes into account the effect of depletion region that extends into gate to drain spacing.The effect of this high field extension region on the noise performance of three HEMT structures is analytically calculated and compared with measured data

Landmark-based morphometric and meristic variations of endangered mrigal carp, Cirrhinus cirrhosus (Bloch 1795), from wild and hatchery stocks

Wild stocks of endangered mrigal carp, Cirrhinus cirrhosus (Bloch 1795), continues to decline rapidly in the Indo-Ganges river basin. With an objective to evaluate its population status, landmark-based morphometric and meristic variations among three different stocks viz., hatchery (Jessore), baor (Gopalganj) and river (Faridpur) in Bangladesh were studied. Significant differences were observed in 10 of the 15 morphometric measurements viz., head length, standard length, fork length, length of base of spinous, pre-orbital length, eye length, post-orbital length, length of upper jaw, height of pelvic fin and barbel length, two of the 8 meristic counts viz., scales above the lateral line and pectoral fin rays and 10 of the 22 truss network measurements viz., 1 to 10, 2 to 3, 2 to 8, 2 to 9, 2 to 10, 3 to 4, 3 to 8, 4 to 5, 4 to 7 and 9 to 10 among the stocks. For morphometric and landmark measurements, the 1st discriminant function (DF) accounted for 58.1% and the 2nd DF accounted for 41.9% of the among-group variability. In discriminant space, the river stock was isolated from the other two stocks. On the other hand, baor and hatchery stocks formed a very compact cluster. A dendrogram based on the hierarchical cluster analysis using morphometric and truss distance data placed the hatchery and baor in one cluster and the river in another cluster and the distance between the river and hatchery populations was the highest. Morphological differences among stocks are expected, because of their geographical isolation and their origin from different ancestors. The baseline information derived from the present study would be useful for genetic studies and in the assessment of environmental impacts on C. cirrhosus populations in Bangladesh

Municipal wastewater can result in a dramatic decline in freshwater fishes: a lesson from a developing country

Impacts of ineffective wastewater management on the biodiversity of receiving waters in developing countries are poorly documented. Using a before-after-control-impact methodology, we measured the effects of untreated wastewater release on the fish community in the Barnoi River, Bangladesh. In 2006, prior to untreated wastewater discharge, fish abundance, species richness and water quality were similar across sampling sites. In 2016, after 8 years of wastewater release to the downstream reach, fish abundance and species richness were reduced by >47% and >35% respectively at downstream sites compared to unaffected upstream sites and >51% and >41% lower respectively compared to the pre-wastewater discharge period. The wastewater impact was particularly severe during months of low discharge (October–December). Water transparency, dissolved oxygen and pH were lower (P < 0.001) at impacted downstream sites compared to upstream sites. Nineteen species (41.3% of all species we recorded) are threatened in Bangladesh and the abundance of these species, except one, decreased significantly (P < 0.05) at the impacted sites. We recommend improved wastewater management by applying primary treatment facilities and incorporating reedbed filtration as a mean of biological treatment, into the canals carrying wastewaters. The success of such measures should be tested with fish species that were most responsive to wastewater, using the indicator species concept

Morphological consequences of hybridization between farm and wild Atlantic salmon Salmo salar under both wild and experimental conditions

The escape of Atlantic salmon Salmo salar from aquaculture has been identified as a significant threat to the persistence and stability of wild salmon populations. Yet the magnitude of phenotypic impacts due to hybridization remains largely unresolved. We evaluated the phenotypic consequences of hybridization using geometric morphometrics both under natural conditions in the wild and in the laboratory using common garden experiments. Juvenile Atlantic salmon field-collected in 2015 and 2016 from 18 southern Newfoundland rivers were classified as pure wild, pure farm, or F1 hybrids using genetic assignment. Overall size and shape differences between wild and farm, and wild and F1 hybrid individuals were small, largely size related, and present between pure farm and other crosses. Laboratory-reared pure wild, pure farm, and F1 hybrid salmon were grown in tank and semi-natural conditions. Wild fish were significantly larger than both farm and hybrid salmon at first feeding; these size differences remained at 80 d post first feeding under semi-natural conditions, but all crosses were the same size in tank conditions, and there were no differences between pure farm and hybrid individuals under either condition. Significant shape differences were present among all pairwise comparisons under tank conditions, and in semi-natural conditions, pure wild individuals differed significantly from pure farm and hybrid individuals. Our results suggest phenotypic differences observed under laboratory conditions between wild and farm×wild hybrid individuals may not be appreciable in the wild, and that significant genetic changes may occur in wild populations experiencing hybridization in the absence of obvious large phenotypic changes.publishedVersio

Long - term conservation agriculture increases nitrogen use efficiency by crops, land equivalent ratio and soil carbon stock in a subtropical rice - based cropping system

Conservation Agriculture (CA) is still a relatively new approach for intensively cultivated (3 crops yr-1) rice-based cropping systems that produce high crop yield and amounts of residues annually. With the recent development of transplanting of rice into tilled strips on non-puddled soil, CA could become feasible for rice-based cropping patterns. However, the effect of increased retention of crop residues on crop response to nitrogen (N) fertilization rate in strip tilled systems with the transplanted rice and other crops grown in the annual rotation is yet to be determined. For nine years, we have examined the effects of soil disturbance levels - strip tillage (ST) and conventional tillage (CT), two residue retention levels –15% residue by height (low residue, LR) and 30% residue (high residue, HR) and five N rates (60%, 80%, 100%, 120%, and 140% of the recommended N fertilizer doses (RFD)) for a rice-wheat-mungbean cropping sequence. The 100% RFD was 75, 100 and 20 kg N ha-1for rice, wheat, and mungbean, respectively. Rice yields were comparable between the two tillage systems for up to year-6, wheat for up to year-3 but mungbean yield markedly increased in ST from year-1; however, the land equivalent ratio increased from year-1, principally because of higher mungbean yield. Introduction of ST increased land equivalent ratio by 26% relative to CT, N use efficiency and partial factor productivity. Nitrogen fertilizer demand for maximum yield in ST was increased by about 10% for rice and 5% for mungbean but decreased by 5% for wheat. Although fertilizer N demand had increased in ST system due to higher yield than CT, the N requirement declined by50–90% when the same yield goal is considered for ST as for CT. The soil organic carbon stock (0–15 cm) after 8 years increased from 21.5 to 30.5 t ha-1 due to the effect of ST plus high crop residue retention. Annual gross margin increased by 57% in ST over CT practice and 26% in HR over LR retention. In conclusion, after 9 years practicing CA with increased residue retention under strip tillage, the crops had higher N use efficiency, grain yield, land equivalent ratio and annual gross margin in the rice-wheat-mungbean cropping system while the N fertilizer requirement increased minimally

Cost-effectiveness analysis of a large-scale crèche intervention to prevent child drowning in rural Bangladesh

Background Drowning is the leading cause of death among children 12–59 months old in rural Bangladesh. This study evaluated the cost-effectiveness of a large-scale crèche (daycare) intervention in preventing child drowning. Methods The cost of the crèches intervention was evaluated using an ingredients-based approach and monthly expenditure data collected prospectively throughout the study period from two agencies implementing the intervention in different study areas. The estimate of the effectiveness of the crèches intervention was based on a previous study. The study evaluated the cost-effectiveness from both a program and societal perspective. Results From the program perspective the annual operating cost of a crèche was $416.35 (95$221 to $576), the annual cost per child was$16 (95% CI: $8 to$23), and the incremental-cost-effectiveness ratio (ICER) per life saved with the crèches was $17,008 (95$8817 to $24,619). From the societal perspective (including parents time valued) the ICER per life saved was −$166,833 (95% CI: − $197,421 to −$141,341)—meaning crèches generated net economic benefits per child enrolled. Based on the ICER per disability-adjusted-life years averted from the societal perspective (excluding parents time), $1978, the crèche intervention was cost-effective even when the societal economic benefits were ignored. Conclusions Based on the evidence, the crèche intervention has great potential for generating net societal economic gains by reducing child drowning at a program cost that is reasonable