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The occurrence of a pelagic salp Iasis cylindrica (Cuvier, 1804) is noted, for the first time, from Bangladesh marine water since its first record from the Bay of Bengal region nearly four decades ago. A total of eight solitary zooids of I. cylindrica were collected from a rocky intertidal habitat characterized by water temperature, salinity and pH of 30 °C, 31‰ and 8.2, respectively. The species was identified by examining morphological characteristics, for which detailed descriptions and photographs (both live and stained) are provided. Such information about the Bay of Bengal specimens of I. cylindrica is lacking in the literature. In addition, comparison between I. cylindrica and its closely related species of the genus Salpa are pointed out as they often co-occur.

Flyingfishes of the family Exocoetidae are sometimes difficult to identify solely based on morphology as members of certain genera share overlapping characteristics. Combining morphological and molecular analyses, the present study reports two specimens of stained flyingfish Cheilopogon spilonotopterus (Bleeker 1865) from the northern Bay of Bengal. As for COI gene sequences, nucleotide variations at five different positions (576 nucleotides identical out of 581 bp) were noted between two specimens of C. spilonotopterus and K2P genetic distances for all conspecific sequences ranged 0.000–0.050. The results of DNA barcoding, therefore, support the validity of both specimens as C. spilonotopterus at genetic level. These are the first DNA barcode records of C. spilonotopterus from the northern Bay of Bengal region.

Not Available Bangladesh J. Zool. 48(1): 189-195, 2020

Knowledge of bio-physicochemical variables is essential to better understand the functioning of tropical marine ecosystems, which are rich in biodiversity and provide nutrition and livelihoods to billions of people in the developing countries. This study analysed the spatial and temporal variability of phytoplankton and zooplankton with chlorophyll, primary productivity, temperature, salinity, oxygen and nutrients in the Bay of Bengal (BoB), collecting data from the World Ocean, and COPEPOD and Aqua MODIS records. The results indicated a strong gradient in bio-physicochemical conditions of the BoB, from the coast to the open sea. Specifically, the spatial variability in chlorophyll was negatively correlated (R2= 0.59) with temperature and zooplankton, while a positive correlation (R2= 0.70) was noted between chlorophyll and silicate, nitrate, phosphate, dissolved oxygen and salinity. All the variables exhibited a strong vertical gradient at depths up to 500 m. Temperature, nutrients, zooplankton and to a lesser extent salinity and rainfall had an influence on the annual abundance of phytoplankton. Over the long term, a significant positive trend in temperature and a significant negative trend in primary productivity were observed in the BoB. The findings of this study will be useful to draw insights on the state of fisheries habitats and the overall environmental conditions of the BoB in response to future climate changes.

Information on stock condition and reproductive biology are important for fisheries conservation and management planning. This study examined reproduction, growth, mortality and yield of sulphur goatfish (Upeneus sulphureus Cuvier 1829), which is a low-value food fish abundantly caught as bycatch in artisanal and industrial fishing from the southeast coast of Bangladesh at northern Bay of Bengal. Data were collected monthly obtaining samples from local fish landing center. The gonadosomatic index indicated that U. sulphureus spawns twice a year during January–May and August–October. Fecundity of the fish was positively correlated with the body and gonad weight, and varied from 15 128–97 274 eggs with fish weight 11.30–58.73 g. Monthly length–frequency distribution was analyzed through FISAT software, thus the estimated seasonalized von Bertalanffy growth parameters were L∞ = 21.80 cm, K = 0.54 per year, C = 0.5, WP = 0.1 and Rn = 0.300, respectively. Moreover, the value of seasonalized total mortality coefficient Z (2.24) was smaller than that of the non-seasonalized Z (4.16). The instantaneous natural mortality and fishing mortality, calculated for non-seasonalized total mortality, were 1.31 and 2.86, respectively. Furthermore, the high exploitation rate (E = 0.69) was close to maximum exploitation level (Emax = 0.75) in yield-per-recruit analysis, suggesting that U. sulphureus is being exploited at the MSY (maximum sustainable yield) level. Therefore, further increase in fishing effort may reduce U. sulphureus stocks in the coastal waters of Bangladesh.

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 2/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.

Adaptation to seasonal change is essential for survival, and is especially critical for organisms living in physically harsh environments. Brittle stars (Ophiothrix), known as a keystone species, inhabiting the intertidal rocky ecosystem are affected by multiple stressors, but molecular insights into their adaptation remain poorly studied. In the present study, transcriptomic responses of Ophiothrix exigua from the intertidal habitats of the North Pacific Ocean during summer and winter are reported. A total of 12,844 differentially expressed genes (DEGs) were identified. Of these, 7102 genes were up-regulated and 5742 genes were down-regulated in summer relative to winter. One hundred fifty-two key DEGs, including 31 up-regulated and 121 down-regulated genes, were categorized into three major subcategories and seven subclasses. The key DEGs included heat shock cognate protein 70 (HSC70), toll-like receptor-2 (TLR2), cAMP-dependent protein kinase catalytic subunit beta-like isoform X2 (PKA), serine/threonine-protein kinase mTOR (MTOR), and ras-related c3 botulinum toxin substrate 1 isoform X1 (RAC1). Glutathione peroxidase-like (GPX) and tubulin superfamily members (TUBA, TUBB) were consistent across seasons. The main defense-related pathways in brittle star were phagosome, apoptosis, and glutathione metabolism. These findings would greatly enhance our understanding of the genomic basis of environmental adaptation in intertidal invertebrates.

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 (Gunther 1860), Eubleekeria rapsoni (Munro 1964), Gazza rhombea Kimura, Yamashita & Iwatsuki 2000 and Karalla daura (Cuvier 1829) constitute the first records in Bangladesh. And the present specimens of D. megalolepis represent the westernmost distribution of this species in the Indo-Pacific region. This article is protected by copyright. All rights reserved.

Antibiotic exposure in the intensive care unit (ICU) is very high, although 50% of all antibiotics may be unnecessary. We aimed to determine predicting factors, outcomes, and the utility of simple screening tools to avoid antibiotic overuse in the ICU. We analyzed 510 young children who did not receive antibiotics during ICU stay to those treated with antibiotics. The logistic regression analysis revealed that cases were more often older and independently associated with hypernatremia. Cases less often had severe underweight, altered mentation, age-specific fast breathing, lower chest wall in-drawing, adventitious sound on lung auscultation, abdominal distension, developmental delay, hyponatremia, hypocalcemia, and microscopic evidence of invasive diarrhea (for all, p

A new strain of coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for the coronavirus disease 2019 (COVID-19) pandemic was first detected in the city of Wuhan in Hubei province, China in late December 2019. To date, more than 1 million deaths and nearly 57 million confirmed cases have been recorded across 220 countries due to COVID-19, which is the greatest threat to global public health in our time. Although SARS-CoV-2 is genetically similar to other coronaviruses, i.e., SARS and Middle East respiratory syndrome coronavirus (MERS-CoV), no confirmed therapeutics are yet available against COVID-19, and governments, scientists, and pharmaceutical companies worldwide are working together in search for effective drugs and vaccines. Repurposing of relevant therapies, developing vaccines, and using bioinformatics to identify potential drug targets are strongly in focus to combat COVID-19. This review deals with the pathogenesis of COVID-19 and its clinical symptoms in humans including the most recent updates on candidate drugs and vaccines. Potential drugs (remdesivir, hydroxychloroquine, azithromycin, dexamethasone) and vaccines [mRNA-1273; measles, mumps and rubella (MMR), bacille Calmette-Guérin (BCG)] in human clinical trials are discussed with their composition, dosage, mode of action, and possible release dates according to the trial register of US National Library of Medicines (clinicaltrials.gov), European Union (clinicaltrialsregister.eu), and Chinese Clinical Trial Registry (chictr.org.cn) website. Moreover, recent reports on in silico approaches like molecular docking, molecular dynamics simulations, network-based identification, and homology modeling are included, toward repurposing strategies for the use of already approved drugs against newly emerged pathogens. Limitations of effectiveness, side effects, and safety issues of each approach are also highlighted. This review should be useful for the researchers working to find out an effective strategy for defeating SARS-CoV-2.

not available Bangladesh J. Zool. 46(2): 275-280, 2018

Tropical hilsa shad, which is an anadromous fish migrating from the sea to spawn in freshwater river, constitutes an important fishery in some Asian and Middle East countries, particularly in Bangladesh. But, historical information on hilsa biology and ecology has confronted the scientists and policymakers with research and management challenges. We have reviewed both the old and recent findings on hilsa fishery to document the status of knowledge and potential gaps, necessary to comprehend for formulating a more effective fishery management plan. Thus, there has been a decline in hilsa catches in the riverine system associated with shift in fish migration routes, indiscriminate harvesting of brood and juvenile fish, and degradation of habitat. Specifically, the riverine hilsa catches peaked in the 1960s, declining thereafter, and became relatively abundant in marine waters since 1990s. Biological data indicated that hilsa goes through multiple reproductive cycles; therefore, a comprehensive understanding of reproductive biology, recruitment by various cohorts, stock abundance and habitats across the life cycle are necessary to accurately impose fishery regulatory measures, such as fishing ban in spawning season in Bangladesh. Moreover, domestication initiative is important for artificial seed production and mariculture development of hilsa that can not only offer economic return to small‐scale farmers but also reduce the growing pressure on capture fishery. Importantly, the arrangement of co‐management is found ideal as fishermen, scientists and managers can work jointly to improve the regulatory processes and to sustain the hilsa fishery over time.

Meeting consumer concerns and preferences for fresh and safely processed fisheries products free of chemical and synthetic preservatives is a challenge for the aqua-food industry. As such, natural preservatives from plant and animal origin including chitosan, essential oils (EOs), plant extracts and lactic acid bacteria have attracted considerable interest recently. These preservatives have antimicrobial and antioxidant properties that can retard spoilage, uphold product quality and safety as well as extend the storage shelf-life of fish and seafood. Chitosan and EOs have been successfully used in edible coatings, film wrapping and dipping solutions. The present review focuses on the effectiveness of chitosan, EOs and other natural preservatives intended for prolonging the shelf-life of fisheries products, and maintaining their freshness and quality. Moreover, the mechanisms of action of natural additives, harmful impacts of chemical preservatives and status of aquatic food preservatives in Southeast Asian countries are summarized, with notes on important research gaps. Overall, this study informs recent development in natural preservatives related to the aqua-food industry.

Threonine is an essential amino acid in fish nutrition, but no information is available on the dietary threonine requirement in largemouth bass, Micropterus salmoides. Thus, 360 fish (19.0 ± 0.1 g) were randomly divided into six experimental groups (20 fish per cage; three replicates), and offered diets supplemented with crystalline L-threonine at 0 g kg−1 (control), 2.5 g kg−1 (Thr-2.5), 5.0 g kg−1 (Thr-5.0), 7.5 g kg−1 (Thr-7.5), 10.0 g kg−1 (Thr-10.0) and 12.5 g kg−1 (Thr-12.5) for eight weeks to determine the optimum threonine requirement of largemouth bass. The results showed that dietary threonine significantly (P 0.05) by any dietary treatments. Whole-body crude protein and lipid were lower (P

Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k (growth coefficient) and t 0 (zero-length age) gradually increased from 0.26 and–0.58 year in 1960 to 0.56 and–0.25 year in 2008, respectively. Although, L∞ (body length) sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t r (inflexion age) decreased from 3.78 year in 1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as: fishing vessel power>feeding grade>sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.

Seaweeds are primary producers and among the important marine ecosystem engineers capable of modifying their surrounding abiotic and biotic environments. The southern coast of Bangladesh has an excellent prospect for seaweeds farming due to favorable environmental conditions and natural availability of commercially important species. Through quantitative and qualitative analyses, the present study determines potential contribution of seaweeds toward achieving several targets of United Nations sustainable development goals (SDGs) and the blue economic development in Bangladesh. There are 300 households engaged in seaweeds farming, primarily along the southeast coast, producing 390 tonnes wet weight (= 97.5 tonnes dry weight) of seaweeds per annum with potential applications in food, feed, cosmetics and pharmaceuticals sectors. And the current seaweeds production can be increased yearly at ~50% rate, which is 50 million tonnes (dry weight) from ~5,000 km2 farming area when extrapolated to the year 2050. This may bring a positive change to issues regarding food security, gender equality, economic growth, nutrients removal, carbon sequestration, employment and aquatic environmental health. Overall, the benefits of seaweeds farming could reflect on 26 targets of 8 SDGs and potentially contribute US$0.7 million to the blue economy in Bangladesh.

Several antiviral peptides (AVPs) from aquatic organisms have been effective in interfering with the actions of infectious viruses, such as Human Immunodeficiency Virus-1 and Herpes Simplex Virus-1 and 2. AVPs are able to block viral attachment or entry into host cells, inhibit internal fusion or replication events by suppressing viral gene transcription, and prevent viral infections by modulating host immunity. Therefore, as promising therapeutics, the potential of aquatic AVPs for use against the COVID-19 pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is considered. At present no therapeutic drugs are yet available. A total of 32 AVPs derived from fish and shellfish species are discussed in this review paper with notes on their properties and mechanisms of action in the inhibition of viral diseases both in humans and animals, emphasizing on SARS-CoV-2. The molecular structure of novel SARS-CoV-2 with its entry mechanisms, clinical signs and symptoms are also discussed. In spite of only a few study of these AVPs against SARS-CoV-2, aquatic AVPs properties and infection pathways (entry, replication and particle release) into coronaviruses are linked in this paper to postulate an analysis of their potential but unconfirmed actions to impair SARS-CoV-2 infection in humans.

Tidepools are one of the intertidal habitats providing homes to many marine species. This study investigated the diversity and abundance of tidepool fishes on a rocky shore from Bangladesh. Fish samples were collected from the east and west coasts of St. Martin’s Island between November 2018 and March 2019. There were 441 specimens distributed in 23 species belonging to 20 genera and 14 families. Among those, 11 species represented new records for Bangladesh, namely Allenbatrachus reticulatus, Bathygobius coalitus, Bathygobius curacao, Callogobius hasseltii, Crenimugil crenilabis, Halichoeres nigrescens, Istigobius decoratus, Istigobius ornatus, Ostorhinchus cookii, Siganus sutor and Yongeichthys nebulosus. The most speciose families were Gobiidae (6 species), Pomacentridae (3 species) and Blenniidae (2 species), and in terms of number of individuals, Gobiidae (42%) and Blenniidae (38%) were abundant. The mean abundance of fish in tidepools was decreasing with increasing intertidal elevations (i.e. lower > middle > upper intertidal zones), although the differences were not significant. Moreover, fish abundance and diversity were positively correlated with the surface area of tidepool. Six species were common in the sampling sites, and the east coast of St. Martin’s Island had higher species richness and diversity than the west coast. Temperature (31.8 ± 2.9 °C), salinity (31.8 ± 2.1‰) and pH (8.3 ± 0.1) of the tidepool waters were comparable to those reported for a range of rocky/reef environments across the Asia–Pacific region. This is the first report on tidepool fishes from the northern Bay of Bengal that can be useful for understanding the ecological importance of intertidal zones, and further expanding the knowledge of marine biodiversity and natural history in data-poor regions.

Aquatic habitat connectivity is vital for the continued existence of migratory fish. Using GIS and outranking multicriteria analysis based on hydrometeorological data, this study describes habitat preference of egg, fry, juvenile and adult phases of hilsa shad, Tenualosa ilisha (Hamilton), as well as their spawning areas in the aquatic ecosystems of Bangladesh. The total area studied was 29 484 km2, about 29% of which belonged to the Meghna, Shahbajpur, Tetulia and Ander Manik rivers, and the channels of Sandwip, Kutubdia and Moheshkhali islands, which provide the most suitable habitat for the species. An additional 27% of moderately suitable area was located in other deltaic rivers and inshore waters. The remaining 44% was offshore deeper water, which was least suitable for hilsa. The most suitable area for spawning, eggs, fry, adults and juveniles was 6, 11, 29, 38 and 56% of the area, respectively. The model outputs were validated against field measurements and fishers’ indigenous knowledge with an accuracy level of 92%. Thus, this study provides key information about the location of hilsa at different stages of its life cycle, information useful in understanding its occurrence over a relatively large geographical area. Information of this kind is useful in fishery conservation and management.

A sanctuary is a specific form of protected area and considered to be an important management measure for the conservation and management of fisheries resources. Using socioeconomic and biological indicators, this study investigates the perceptions of fishers towards sanctuaries that were established in the rivers of Meghna and Padma and in inshore waters of Bangladesh since 2005 to protect the declining hilsa ( Tenualosa ilisha ) populations. Both qualitative and quantitative data were collected from six communities adjacent to five hilsa sanctuaries and then analyzed to know the socioeconomic profile of fishers as well as their perceptions of the performance of sanctuaries. The majority of fishers felt that an apparent recent increase in hilsa catch is due to the establishment of sanctuaries. Their perception is well supported by catch statistics that show higher overall hilsa production both from inland and marine waters. However, fishery closure led to substantial economic hardship due to lost income. If the sanctuaries are to function effectively, issues (e.g. lost income) affecting fishers must be addressed by offering compensation schemes so that fishers are able to support their families. The process has to be transparent, inclusive and equitable. There is also a need to support alternative livelihoods for fishers in order to reduce dependence on hilsa fishing. Moreover, fishers must be provided with economic and/or other incentives so as to share responsibilities to protect and manage sanctuaries successfully. Since fishers’ involvement is key to the success of sanctuaries, social acceptance of fish sanctuaries by fishers is a must.

Global warming is a major threat to the natural environment worldwide with potential adverse impact on plankton community. This will ultimately lead to a change in the dynamics of aquatic food webs. In this study we used seasonally forced multi-species version of the classic Rosenzweig–MacArthur predator–prey model to understand the role and stochastic influence of increasing temperature on marine plankton. First, stable coexistence of four phytoplankton and three zooplankton species was created in a system and then the level of temperature changed to achieve our research goal. We found that the stable coexistence of phytoplankton and zooplankton was related to periodic shifts in species biomass, variation in inter-specific competition and niche configuration. Warming significantly reduced total plankton biomass and changed turnover time of a species, with gradual warming breaking the stable coexistence of phytoplankton and zooplankton. In addition, we found that warming make specialist species more vulnerable than generalist species. After adding noise, a significant variation was observed in plankton biomass and amplification of noise was higher for phytoplankton compared to zooplankton. These results suggest that stochastic or unpredictable nature of temperature fluctuations may create a window of opportunity for the emergence of new species. Overall, warming would induce a shift in plankton dynamics and thereby exert pressure on plankton dependent communities such as fish in the long run.

Highlights: • Nutrients and zooplankton were the most important predictors for diatom. • Temperature and zooplankton had a negative effect on diatom. • Species interaction explained 20% variability in diatom abundance. • Six environmental variables explained 57% of the variability. Abstract: Temporal variability in phytoplankton is driven by a range of biotic and abiotic factors. In this study, we aimed to identify and estimate the important explanatory variables affecting the diatom species and their abundance in the coastal waters of Bangladesh. For this, species interaction and six explanatory variables were taken into consideration to develop a density dependent Bayesian regression model for quantifying the relative importance of different explanatory variables causing the variability in diatom abundance. Thus, three nutrients such as silicate, nitrate and phosphate, and zooplankton were identified as the most important predictors for 19–25 species. Moreover, the effect of three nutrients and salinity was positive for most diatoms, while temperature and zooplankton had a negative effect. Species interaction and environmental variables combinedly explained 77% of the variability in diatom abundance, with the latter being the dominant factor. Specifically, six environmental variables combinedly explained 57% of the variability in diatom abundance and the remaining 20% of the variability was due to species interaction. This is the first modelling study on phytoplankton community describing the dynamics of diatom species in the coastal waters of 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.

Onshore barrier in the intertidal area is reported to influence coastal geomorphology, sediment dynamics, and erosion and accretion processes. The present study describes sediment texture and deposition pattern, and shore profile of a tidal mudflat located in the Kutubdia Island of Bangladesh. A physical barrier in the form of concrete ring structure was placed on the mudflat of experimental site and the control site was 50 m away without any barrier. The texture of sediment was mostly medium silt (45.3%) in leeward side (= the side facing away from the tide/wave action) of the barrier. Whereas, coarse silt was dominant in the control (35.2%) and seaward side (31.2%), followed by medium silt (25.1% and 29.0%, respectively). The proportion of fine sand was higher in the control (18.4%) and seaward side (16.1%) than that of the leeward side (6.1%). Because of the barrier, there was noticeable sedimentation on mudflat as demonstrated by increased elevation of shore profile in the leeward side, 23.3 cm vs. 3.6 cm in the control. Sediment deposition was, however, varied due to susceptibility to erosion depending on grain size distribution, e.g. the fine deposits had greater erodibility than the sandy deposits. These results suggest that barrier on mudflat could bring a positive change to the sediment profiling and shore morphology, and thus help stabilizing the eroding shoreline.

Oyster reefs have the potential as eco-engineers to improve coastal protection. A field experiment was undertaken to assess the benefit of oyster breakwater reefs to mitigate shoreline erosion in a monsoon-dominated subtropical system. Three breakwater reefs with recruited oysters were deployed on an eroding intertidal mudflat at Kutubdia Island, the southeast Bangladesh coast. Data were collected on wave dissipation by the reef structures, changes in shoreline profile, erosion-accretion patterns, and lateral saltmarsh movement and related growth. This was done over four seasons, including the rainy monsoon period. The observed wave heights in the study area ranged 0.1–0.5 m. The reefs were able to dissipate wave energy and act as breakwaters for tidal water levels between 0.5–1.0 m. Waves were totally blocked by the vertical relief of the reefs at water levels

Resilience has been conceptualized in various ways by anthropologists, ecologists, systems scientists and engineers; the boundaries of resilience are subjective and context dependent. Consequently, choosing the standards and metrics for assessing resilience remains key challenges for policy makers. In this study, using multicriteria evaluation of 40 basic criteria of human, physical, financial, natural and social assets, we have identified several elements, such as experienced fishermen, natural abundance of hilsa (Tenualosa ilisha), ability to assert decision on fish selling, nets and boats ownership, social harmony and capacity of buying food as essential livelihood assets for the fishermen at Hatiya Island, Bangladesh. These assets may enhance the relative resilience of the fishing community of the island to climate change by as much as 20–40%. The results of this study will improve our understanding of the elements that lead to resilience at the community level.

This study characterized probiotics Kocuria SM1 and Rhodococcus SM2, which were recovered from the intestinal microbiota of rainbow trout (Oncorhynchus mykiss, Walbaum). The cultures were Gram-positive, non-motile, catalase-positive and oxidase-negative cocci or rods. Cell multiplication of SM1 and SM2 was observed at 4–37 °C (45 °C for SM1), in 0–20% (w/v) NaCl and at pH 2–11. The viability was not affected when exposed to pepsin at pH 2.0 and 3.0, and pancreatin at pH 8.0. Neither isolates were chrome azurol S-positive for siderophore production. Of the 19 common enzymes analysed using the API-ZYM system, only 8 were evident in the culture of SM1 compared to 11 enzymes for SM2. The secondary metabolites of both probiotics were inhibitory to Acinetobacter baumannii, Vibrio anguillarum and V. ordalii; SM2 inhibited Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. SM2 was resistant to penicillin and sulphatriad, out of six antimicrobial agents; SM1 was resistant to sulphatriad. These results suggest that Kocuria SM1 and Rhodococcus SM2 are able to grow over a wide range of temperature, salinity and pH, including in conditions that mimic the gastrointestinal environment of fish and produce extracellular enzymes that may have a role in the host digestive processes. Importantly, Rhodococcus SM2 displays a high degree of bacteriocinogenic potential against multi-drug-resistant human pathogens that have never been documented among the gut microbiota of fish.

The availability of suitable freshwater spawning habitat is considered to be a major factor limiting the natural recruitment of anadromous Hilsa shad (Tenualosa ilisha) in the coastal waters of Bangladesh. Against this context, we applied georeferenced habitat database to determine spawning habitat suitability index of Hilsa shad. Landsat imagery and thematic layers were analyzed with ENVI and GIS, and developed a series of GIS models to identify and ranking of suitable spawning grounds. Thus, among the studied 29,484 km2 aquatic ecosystems, only 6% (=1851 km2) area is the most suitable consisting of the rivers Meghna, Shahbazpur, Tetulia and Ander Manik as well as the channel of Sandwip island. Whereas, 20% (=5996 km2) area including river, estuary and near shore water bodies are moderately suitable, and in particular, the offshore deep waters occupying 73% (=21,637 km2) area is least suitable. The model outputs were verified after field data of fishers’ indigenous knowledge with an accuracy level of 87%. This study suggests that necessary measures, such as conservation and management of spawning habitat should be implemented for an increased reproductive and recruitment success that will eventually improve populations of wild Hilsa shad in Bangladesh.

Hilsa shad Tenualosa ilisha comprises the largest and most valuable single fishery of Bangladesh. This study was conducted to identify suitable habitats for Hilsa juvenile in the northern Bay of Bengal along the coast of Bangladesh using Geographical Information Systems (GIS) based Multi-Criteria Evaluation (MCE) of water temperature, dissolved oxygen, pH, salinity, turbidity, current, depth and rainfall. Landsat imagery and 8 thematic layers were analyzed with ENVI and GIS capabilities, and developed as a series of GIS models to identify and prioritize the appropriate habitats for Hilsa juvenile. The study covered 29.484 km2 water body and revealed that 56% (16.388 km2) is the most suitable, 21% (6.054 km2) is moderately suitable and 24% (7.042 km2) is not suitable which was consistent with field verification. The assemblage of marinebrackish-freshwater ecosystems with favourable ecological parameters and rainfall patterns are very much important for supporting juvenile Hilsa in the study area. The results are useful for habitat-specific sanctuary development as the efficient conservation may lead to higher production of adult Hilsa and increase the economic benefit to the fishers.

The effects of dietary probiotics on growth performance, health status of the digestive system and on the blood parameters of juvenile rainbow trout ( Oncorhynchus mykiss , Walbaum) were investigated. Compared to the controls, diets supplemented with Kocuria SM1 and Rhodococcus SM2 for 14 days caused no significant (P > 0.05) change on the growth of fish, although SM2 led to an increased specific growth rate. SM1 or SM2 started to colonize in the gut after 7 days of administration reaching a maximum, i.e. ~ 90–100% of total bacterial population, at 14 days. Yet, the probiotics disappeared from the gut once administration ceased. Structural differences were not noted in the pyloric caeca and foregut, but the overall condition of the midgut and hindgut improved in fish receiving probiotics. The profile of digestive enzymes, as determined by the use of API ZYM, and stress indicators, i.e. serum hemoglobin, urea, creatinine and glucose, was not affected by any of the experimental diets (P > 0.05).

Subcellular components of the probiotics Aeromonas sobria GC2 and Bacillus subtilis JB-1, when administered to rainbow trout, Oncorhynchus mykiss, conferred protection against a new biogroup of Yersinia ruckeri. Thus, intraperitoneal or intramuscular injection of rainbow trout with cell wall proteins (CWPs), outer membrane proteins (OMPs), lipopolysaccharides (LPS), whole cell proteins (WCPs) and live cells followed by challenge on day 8 with Y. ruckeri led to 80-100% survival compared with 10% survival in the controls. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of WCPs and OMPs from GC2 had 10 and 5 variable protein bands in comparison to 11 and 5 bands in the WCPs and CWPs from JB-1. Proteomic analyses were employed following SDS-PAGE to categorize one dominant protein of 104.7 kDa from the CWPs of JB-1 and equated it with 'Bacillus spp. endoglucanase' with a Mascot score >69. These results point to the potential of using cellular components of probiotics for protection of fish against bacterial diseases.

Site selection is a key factor in any aquaculture operation, affecting both success and sustainability as well as solving land or water use conflicts. This study was conducted to identify suitable sites for carp farming development in urban water bodies (UWBs) of Chittagong, Bangladesh using Geographical Information Systems (GIS) based MultiCriteria Evaluation (MCE) of water, soil and infrastructure database. ASTER imagery and 14 thematic layers were analyzed with ENVI and GIS capabilities, and developed a series of GIS models to identify and prioritize the appropriate UWBs for carp farming. The study identified 487 UWBs occupying 362 ha and revealed 280 ha (77%) is the most suitable, 36 ha (10%) is moderately suitable and 46 ha (13%) is not suitable which was consistent with field verification. The results are encouraging for extension of carp culture and diversify the economic activities of the urban dwellers.

Heavy metals, such as arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg) and zinc (Zn), are major environmental problem due to their toxic nature, nonbiodegradability and accumulative behaviors. Once in the estuarine/coastal and marine environments, sources predominantly form industrial, agricultural and hydrocarbon-related activities, scrap metal recycling, commercial ports and sewage, these contaminants accumulate in sediments and soils. Thus, heavy metals concentrations in coastal areas around shipyards, ports and industrial sites with refineries, smelters and milling facilities are often far exceed their background values or standard limits that can be toxic. The toxicity of heavy metals may negatively affects marine biodiversity as higher concentration is detected in fish and other organisms. Due to their persistence, through bioaccumulation and biomagnification along the aquatic food chain, heavy metals contamination ultimately affects human health. Here, the sources and impacts of heavy metals pollution in living systems are discussed.

The occurrence of Porpita porpita is reported, for the first time, in the coral island of St. Martin’s located in the southeastern coastal region of Bangladesh. P. porpita was found to occur in the lower littoral zone and beach rock pools, together with molluscan species, and collected during the pre-monsoon season when both water temperature (> 30°C) and salinity (> 30‰) tend to reach a maximum. This study recounts some details on the discovery and description of the species, and thus extends the global distribution and range limits of the genus Porpita.

The species identification, distribution pattern, density and biomass of salt marsh and seagrass plants with some of the ecological parameters were studied in the Bakkhali river estuary, Cox's Bazar, Bangladesh during the first half of 2006. Two salt marsh species ( Spartina sp. and Imperata cylindrica ) and one seagrass species ( Halophila beccarii ) were identified during this investigation, providing the first reports of Spartina sp. and H. beccarii in coastal Bangladesh. Seagrass H. beccarii was found in an accreted area and co-existing with salt marsh, and scattered sparsely in the salt marsh habitat and macroalgae Ulva intestinalis . Flowering and fruiting were recorded from the seagrass H. beccarri during January and February. No flowers and fruits were observed for the salt marsh Spartina sp. during the study period. Results showed that the shoot density of Spartina ranged from 400 to 2875 shoots m −2 with the highest total biomass (165.80 g dry weight (DW) m −2 ) in March. Shoot density of H. beccarii ranged from 2716 to 14320 shoots m −2 in this estuarine coastal environment. The total biomass of seagrass was higher (17.56 g DW m −2 ) in March compared to the other months. The highest H. beccarii above ground (AG) biomass and below ground (BG) biomass were 9.59 g DW m −2 and 9.42 g DW m −2 , respectively. These parameters are comparable with those generally observed for the salt marsh and seagrass species in the other places of the world.

Arsenic (As) causes health concerns due to its significant toxicity and worldwide presence in drinking water and groundwater. The major sources of As pollution may be natural process such as dissolution of As-containing minerals and anthropogenic activities such as percolation of water from mines, etc. The maximum contaminant level for total As in potable water has been established as 10 µg/L. Among the countries facing As contamination problems, Bangladesh is the most affected. Up to 77 million people in Bangladesh have been exposed to toxic levels of arsenic from drinking water. Therefore, it has become an urgent need to provide As-free drinking water in rural households throughout Bangladesh. This paper provides a comprehensive overview on the recent data on arsenic contamination status, its sources and reasons of mobilization and the exposure pathways in Bangladesh. Very little literature has focused on the removal of As from groundwaters in developing countries and thus this paper aims to review the As removal technologies and be a useful resource for researchers or policy makers to help identify and investigate useful treatment options. While a number of technological developments in arsenic removal have taken place, we must consider variations in sources and quality characteristics of As polluted water and differences in the socio-economic and literacy conditions of people, and then aim at improving effectiveness in arsenic removal, reducing the cost of the system, making the technology user friendly, overcoming maintenance problems and resolving sludge management issues.

The efficacy of cellular components of probiotics Kocuria SM1 and Rhodococcus SM2 to protect rainbow trout (Oncorhynchus mykiss, Walbaum) against vibriosis was assessed. Groups of fish (average weight = 10-15 g) were immunized intraperitoneally (i.p.) with 0.1 ml of subcellular materials, i.e., 0.2 ± 0.05 mg protein per fish, comprising extracellular proteins (ECPs), cell wall proteins (CWPs) and whole cell proteins (WCPs) of SM1 and SM2, respectively, or with 0.1 ml of phosphate-buffered saline (PBS) to serve as the control. Seven days after administration, fish from each group were challenged i.p. with 0.1 ml of a suspension in PBS of 3 × 10(5) cells ml(-1) per fish of Vibrio anguillarum. Use of CWPs and WCPs demonstrated significantly (P0.05) better protection against V. anguillarum insofar as mortalities were reduced to 11-17% [relative percent survival (RPS) = 80-87%], although ECPs fared less well (mortalities = 33-38%; RPS = 56-62%; P0.05), compared to 86% mortalities of the controls. The mode of action reflected activation of innate immune factors by CWPs and WCPs, demonstrating significantly (P0.05) increased expression of respiratory burst (optical density; OD(550 nm)) from 0.039 to 0.043-0.045, peroxidase (OD(550 nm)) from 0.26 to 0.37-0.55, and bacterial killing activities (i.e., percentage of surviving bacteria reduced from 79% to 56-57% for SM2). Moreover, an elevation of leucocyte number (from 1.93% to 1.98-2.93%; P0.05) and immunoglubolin level (from 27 mg ml(-1) to 28.5-33 mg ml(-1); P0.05) were observed with the experimental groups. These results indicate that cell components of the probiotics stimulate an immune response.