Annotated checklist of ponyfishes (Perciformes: Leiognathidae) from Bangladesh, the northern Bay of Bengal.

Information on the taxonomy of ponyfishes (Leiognathidae Gill 1893) from Bangladesh was hitherto inadequate and details of some species were lacking. Based on specimens, the present study reports 12 species of ponyfishes from the coasts of Bangladesh with short descriptions of their diagnostic characters. Six of these species, Aurigequula longispina (Valenciennes 1835), Deveximentum megalolepis (Mochizuki & Hayashi 1989), Equulites leuciscus (Günther 1860), Eubleekeria rapsoni (Munro 1964), Gazza rhombea Kimura, Yamashita & Iwatsuki 2000 and Karalla daura (Cuvier 1829), constitute the first records in Bangladesh. The present specimens of D. megalolepis represent the westernmost distribution of this species in the Indo-Pacific region.

Primary productivity connects hilsa fishery in the Bay of Bengal.

Tropical hilsa shad (Tenualosa ilisha) contributes significantly to the society and economy of Bangladesh, India and Myanmar, but little is known about their habitats across the life cycle and their relationship with environmental drivers. This study describes spatial and temporal variability of productivity in the Bay of Bengal (BoB) relating to hilsa fishery. Decadal data on net primary productivity, nutrients (i.e. nitrate, phosphate and silicate) and zooplankton were collected from Aqua MODIS, world ocean database and COPEPOD respectively with spatial resolution 1°×1°. Moreover, monthly abundance of phytoplankton, hilsa catch and long-term catch dynamics were analyzed to determine the associations between variables. The present study was extended over 3.568 million km2 area, of which 0.131-0.213 million km2 area characterized as the most productive with net primary production of >2,000 mg C/m2/day, 0.373-0.861 million km2 area as moderately productive with 500-2,000 mg C/m2/day, and 2.517-3.040 million km2 area as the least productive with <500 mg C/m2/day which were consistent with field verification data. In case of nutrients, the Ganges-Brahmaputra-Meghna (GBM) delta was rich in nitrate and phosphate than that of the Ayeyarwady delta, while silicate concentration persisted high all over the northern BoB including the deltas. A peak abundance of phytoplankton was observed in GBM delta during the months of August-November, when ~80% of total hilsa are harvested in Bangladesh annually. Variations in seasonal productivity linked with nutrients and phytoplankton abundance are important factors for predicting hilsa habitat and their migration patterns in the deltaic regions and shelf waters of BoB. These results can be useful in forecasting potential responses of the hilsa in BoB ecosystem to changing global ocean productivity.

Microplastic contamination in Penaeid shrimp from the Northern Bay of Bengal.

Microplastic pollution has received increased attention recently due to potential threat to marine biota and human health. This study reports microplastic (MP) content in brown shrimp (Metapenaeus monocerous) and tiger shrimp (Penaeus monodon) inhabiting in the shallow and offshore waters of the Northern Bay of Bengal, Bangladesh. Gastrointestinal tract (GT) of shrimps (n = 150) were examined for MPs following alkali digestion, microscopic observation and chemical analysis by micro-Fourier Transformed Infrared Spectroscope (µFTIR). A total of 33 and 39 MP items were found in P. monodon and M. monocerous, averaging 3.40 ±â€¯1.23 and 3.87 ±â€¯1.05 items/g GT, respectively. Among various shapes, types and colours of MP, filament (57-58%), fiber (32-57%) and black (48-51%) were dominant amongst the various particles identified. Tiger shrimp had high numbers (23 items) of larger size fractions of MPs (1-5 mm) but brown shrimp had high numbers (15 items) of smaller MPs (250-500 µm), and µ-FTIR data confirmed 13 particles of polyamide-6 and 6 particles of rayon polymers. These results provide a baseline of MP contamination in seafood from Bangladesh that should be useful for future monitoring efforts.

Microplastics in fishes from the Northern Bay of Bengal.

Microplastics were determined in pink Bombay-duck (Harpadon nehereus), white Bombay-duck (H. translucens) and gold-stripe sardine (Sardinella gibbosa) collected from the Northern Bay of Bengal at Bangladesh. Gastrointestinal tracts of fishes (n = 25 per species) were examined for microplastics following alkali digestion protocol, microscopic observations and chemical analysis by micro-Fourier Transformed Infrared Spectroscope (µ-FTIR). A total of 443 microplastic items were found in the intestines of H. nehereus, H. translucens and S. gibbosa, averaging in the range of 3.20-8.72 items per species. Among various shapes, colours and types of microplastics, irregular (37-43%), white/transparent (26-68%) and fiber (50-55%) were dominant. The size fraction of microplastics ranging between 1 µm and 5 mm was 68-84 items/kg biomass, and µ-FTIR analysis identified 13 particles of polyethylene terephthalate and 66 particles of polyamide. The study findings raised concern that microplastics in marine fish could be a threat to public health via the food chain.

A verified habitat suitability model for the intertidal rock oyster, Saccostrea cucullata.

There is growing interest to restore oyster populations and develop oyster reefs for their role in ecosystem health and delivery of ecosystem services. Successful and sustainable oyster restoration efforts largely depend on the availability and selection of suitable sites that can support long-term growth and survival of oysters. Hence, in the present study a habitat suitability index (HSI) model was developed for the intertidal rock oyster (Saccostrea cucullata), with special attention: (1) to the role of the monsoon in the suitability of oyster habitats, and (2) to identify potential suitable sites along the south-eastern Bangladesh coast. Seven habitat factors were used as input variables for the HSI model: (1) water temperature; (2) salinity; (3) dissolved oxygen; (4) particulate inorganic matter (PIM); (5) pH; (6) Chlorophyll-a; and (7) water flow velocity. Seven field surveys were conducted at 80 locations to collect geo-spatial environmental data, which were then used to determine HSI scores using habitat suitability functions. The model results showed that the areas suitable (HSI >0.50) for oyster settlement and growth were characterized by relatively high salinities, Chlorophyll-a, dissolved oxygen and pH values. In contrast, freshwater dominated estuaries and nearby coastal areas with high suspended sediment were found less suitable (HSI <0.50) for oysters. HSI model results were validated with observed oyster distribution data. There was strong correlation between the HSI calculated by the model and observed oyster densities (r = 0.87; n = 53), shell height (r = 0.95; n = 53) and their condition index (r = 0.98; n = 53). The good correspondence with field data enhances the applicability of the HSI model as a quantitative tool for evaluating the quality of a site for oyster restoration and culture.

Stagnant surface water bodies (SSWBs) as an alternative water resource for the Chittagong metropolitan area of Bangladesh: physicochemical characterization in terms of water quality indices.

The concern over ensuing freshwater scarcity has forced the developing countries to delve for alternative water resources. In this study, we examined the potential of stagnant surface water bodies (SSWBs) as alternative freshwater resources in the densely populated Chittagong metropolitan area (CMPA) of Bangladesh--where there is an acute shortage of urban freshwater supply. Water samples were collected at 1-month intervals for a period of 1 year from 12 stations distributed over the whole metropolis. Samples were analyzed for pH, water temperature (WTemp), turbidity, electrical conductivity (EC), total dissolved solids, total solids, total hardness, dissolved oxygen (DO), chloride, orthophosphates, ammonia, total coliforms (TC), and trace metal (Cd, Cr, Cu, Pb, As, and Fe) concentrations. Based on these parameters, different types of water quality indices (WQIs) were deduced. WQIs showed most of CMPA-SSWBs as good or medium quality water bodies, while none were categorized as bad. Moreover, it was observed that the minimal water quality index (WQIm), computed using five parameters: WTemp, pH, DO, EC, and turbidity, gave a reliable estimate of water quality. The WQIm gave similar results in 72% of the cases compared with other WQIs that were based on larger set of parameters. Based on our finding, we suggest the wider use WQIm in developing countries for assessing health of SSWBs, as it will minimize the analytical cost to overcome the budget constraints involved in this kind of evaluations. It was observed that except turbidity and TC content, all other quality parameters fluctuated within the limit of the World Health Organization suggested standards for drinking water. From our findings, we concluded that if the turbidity and TC content of water from SSWBs in CMPA are taken care of, they will become good candidates as alternative water resources all round the year.

Rice-ORS versus glucose-ORS in management of severe cholera due to Vibrio cholerae O139 Bengal: a randomized, controlled clinical trial.

This study examined the comparative efficacies of rice-based oral rehydration solution (R-ORS) and glucose-based oral rehydration solution (G-ORS) in the management of severe cholera due to Vibrio cholerae O139 Bengal that causes epidemic cholera in many developing countries. Stool culture-proved adult male patients with severe cholera due to V. cholerae O139 Bengal were randomly assigned in a 1:1 ratio to receive either R-ORS or G-ORS after their initial rehydration with intravenous (i.v.) fluid and subsequently four hours of observation. They also received the usual hospital diet and tetracycline capsules (500 mg 6 hourly for three days) immediately after their enrollment in the study. The primary outcomes for observation were stool output during the first 24 hours after intervention and treatment failure as measured by the incidence of re-institution of i.v. fluid after initiation of trial therapy and duration of diarrhoea. Of 113 patients finally included in the study, 57 received R-ORS and 56 G-ORS. The admission characteristics of the two treatment groups were comparable. No significant differences in the first 24 hours of median (inter-quartile range) stool output [179 (67-206) g/kg in R-ORS group vs 193 (80-237) g/kg in G-ORS group; p = 0.52], incidences of unscheduled i.v. fluid requirement [21% (12/57) in R-ORS group vs 25% (14/56) in G-ORS group; p = 0.78], and median (inter-quartile range) duration of diarrhoea [32 (24-48) hours in R-ORS group vs 32 (24-56) hours in G-ORS group; p = 0.64] were observed. It is concluded that rice-based ORS is effective but not superior to standard glucose-based ORS in the management of adult males with severe cholera due to V. cholerae O139 Bengal.

Tetracycline in the treatment of severe cholera due to Vibrio cholerae O139 Bengal.

Vibrio cholerae O139 synonym Bengal, recognized in 1993, is the second member in the list of about 200 serogroups of V. cholerae with epidemic and pandemic potential. Although replacement of fluids and electrolytes remains the cornerstone in the management of cholera, antimicrobial therapy can significantly shorten the duration of diarrhoea, and reduce stool volume and requirements ofrehydration fluids. The role of antimicrobial therapy on the natural course of the disease caused by this relatively new pathogen has not been systematically assessed. A randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the efficacy of tetracycline in the treatment of adults with severe cholera due to V. cholerae O139 Bengal. Forty-three adult males with severe cholera were randomly allocated to receive either 500 mg of tetracycline (n=21) or placebo (n=22) for three consecutive days. Demographic and clinical characteristics of these patients on admission were comparable. Tetracycline therapy was associated with significantly reduced total median (inter-quartile range) stool volume [216.48 (90.18-325.22) mL/kg vs 334.25 (215.12-537.64) mL/kg; p=0.001], higher rates of clinical cure (81% vs 27%; p<0.001), and shorter median (inter-quartile range) duration of diarrhoea [32 (24-48) hours vs 80 (48-104) hours; p<0.001]. The mean +/- (SD) requirement of intravenous fluid was not significantly different between the two groups [146.42 +/- 42.12 mL/kg vs 150.44 +/- 27.21 mL/kg; p=0.70]. The median (inter-quartile range) duration of faecal excretion of V. cholerae O139 was significantly shorter in the tetracycline group than the placebo group [1(1-2) day vs 5 (3-6) days; p<0.001]. The results of the study indicate that tetracycline therapy is clinically useful in the treatment of severe cholera due to V. cholerae O139 Bengal.