Risk in aquaculture: farmers’ perceptions and management strategies in Bangladesh

Abstract

This study examines Bangladesh fish farmers’ perception for risk sources, risk management strategies, and the relationship with socio-demographic variables. Data were collected from a sample of 350 farmers in Bangladesh. Exploratory factor analysis of a set of perception measurement items was used to assess farmers’ attitudes towards risk and their risk management strategies. The results reveal that fish-diseases, fish price variability, low quality of feed and fingerlings, flood and credit constraints were perceived as the most important sources of risk. For risk management, supply of good quality feed and fingerlings, diseases prevention, crop insurance, increasing personal savings, and assurance of bank loans were considered as the most important strategies to mitigate risks. Empirical evidence shows that farmers engage in multiple management strategies to reduce production risk.     

Ingestion efficiency of Macrobrachium rosenbergii (de Man) larvae feeding on Artemia, Moina micrura Kurz and their combination

Ingestion efficiency of Macrobrachium rosenbergii (de Man) larvae feeding on Artemia alone (A), Moina alone (M) and a 50:50 mixture of Artemia and Moina (AM) at 1, 3, 5 and 7 organisms ml^-1 densities was investigated in terms of individual ingestion rate (IIR), dry mass ingestion (DMI) and energy intake (EI). Irrespective of larval stages and test food densities, larvae showed a significantly higher IIR for diet A except for AM, as the IIR for A and AM were similar from stage V onwards. Compared with diet A, IIR of M were sevenfold to fourfold lower, up to stage V. However, the larvae showed a sharp increase in IIR thereafter and gradually the differences reduced to about 1.6-1.2 fold at later stages. Despite the lower IIR, both DMI and EI for Moina were higher from stage VIII onwards than values for Artemia. In case of mixed diet (AM), the larvae of all stages showed a food selectivity response.     

Methionine Requirement of Juvenile Japanese Flounder Paralichthys olivaceus

Abstract.— Growth studies were conducted to determine the dietary methionine requirement of juvenile Japanese flounder Paralichthys olivaceus . A basal diet was formulated to contain 50% crude protein from casein and gelatin, as intact protein sources, supplemented with crystalline L-amino acids (CAA), to correspond to the amino acid pattern found in the whole body protein of the juvenile Japanese flounder, except methionine. Test diets contained six graded levels of L-methionine 0.53, 0.83, 1.13, 1.43, 1.73, and 2.03% of diet (dry matter basis) or 1.06, 1.66, 2.26, 2.86, 3.46 and 4.06% of protein. To prevent leaching losses of water-soluble amino acids, CAA were pre-coated with carboxymethylcellulose (CMC), and diets were further bound with both CMC and κ-carrageenan after addition of the pre-coated CAA. Weighing about 2.80 g, each triplicate group of the juvenile flounder were fed test diets twice a day (5% of body weight) for 40 d. Survival rate, specific growth rate, feed conversion efficiency and apparent protein retention were significantly ( P < 0.05) affected by dietary methionine concentrations. The optimum dietary level of methionine in the presence of 0.06% of dietary cystine for Japanese flounder juvenile was estimated by using break point analysis. The values determined based on weight gain and feed efficiency were 1.49% of diet (or 2.98% of protein) and 1.44% of diet (or 2.88% of protein), respectively. These requirement values are close to the methionine level of flounder whole body protein.     

Gill ATPase activities of silver perch, Bidyanus bidyanus (Mitchell), and golden perch, Macquaria ambigua (Richardson): Effects of environmental salt and ammonia

The Australian freshwater fish, silver and golden perch, are increasingly being used for aquaculture. Addition of salt to water is commonly used in commercial aquaculture to reduce stress attributed to high ammonia concentrations. The activities in gill homogenates of ouabain-sensitive Na⁺/K⁺-ATPase and NEM-sensitive ATPases (as a measure of H⁺-ATPases) of silver and golden perch were measured after maintaining the fish in water containing different salt and ammonia concentrations. Six treatments were applied in a 2 × 3 factorial design: two salt treatments, low salt (LS) of 2.5 g l^− 1 and high salt (HS) 5 g l^− 1, and three ammonia treatments, no added ammonia (NA), low ammonia (LA), 3 mg total ammonia nitrogen (TAN) l^− 1 and high ammonia (HA), 5 mg TAN l^− 1. In both species, activity of Na⁺/K⁺-ATPase was lowest in fish kept in the LSNA treatment (7.4 ± 0.4 μmol Pi mg protein^− 1 h^− 1 for silver perch and 3.1 ± 0.6 for golden perch) and highest in the HSHA treatment (15.2 ± 1.0 μmol Pi mg^− 1 protein h^− 1 for silver and 8.4 ± 1.2 for golden perch). In both species there was a significant increase (P < 0.001) in Na⁺/K⁺-ATPase activity with increase in salt concentration and with an increase in ammonia concentrations. A significant interaction (P < 0.036) between salt and ammonia on Na⁺/K⁺-ATPase activity was observed in silver but not in golden perch. In contrast, the lowest activity for NEM-sensitive ATPase was observed in the HSNA treatment (1.0 ± 0.2 μmol Pi mg^− 1 protein h^− 1 for silver and 1.5 ± 0.4 for golden perch) and highest in LSHA treatment (2.9 ± 0.4 μmol Pi mg^− 1 protein h^− 1 for silver and 3.6 ± 1.2 for golden perch). In both species there was a significant decrease in NEM-sensitive ATPase activity with increase in salt concentration and an increase in activity with increase in ammonia (P < 0.003). In silver perch, a significant interaction between the treatments was observed (P < 0.02). The results suggest that in these species of freshwater fish the Na⁺/K⁺-ATPase has a role in salt and ammonia homeostasis and that the NEM-sensitive ATPases are more active in fish kept in water with a lower salt content. It is possible that the increase in ammonia resistance when salt is added to the environmental water in commercial aquaculture systems may be due to the effects of salt on gill Na⁺/K⁺-ATPase activity rather than the NEM-sensitive ATPases.     

Thermo-mechanical and morphological properties of short natural fiber reinforced poly (lactic acid) biocomposite: Effect of fiber treatment

Untreated oil palm empty fruit bunch (REFB), alkali treated EFB (AEFB), ultrasound treated EFB (UEFB) and simultaneous ultrasound-alkali treated EFB (UAEFB) short fibers were incorporated in poly(lactic acid) (PLA) for fabricating bio-composites. The REFB fiber-PLA (REPC) and treated EFB (TEFB) fiber-PLA (TEPC) composites were prepared and characterized. Glass transition temperature, crystal melting temperature, decomposition temperature, melt flow index, density and mechanical properties (tensile strength, tensile modulus and impact strength) of TEPC are found to be higher than those of REPC. The observed crystallization temperature of TEPC is lower than that of REPC. Among all samples, TEPC prepared from UAEFB fiber shows better performances than other samples fabricated by REFB and AEFB fibers. Scanning electron microscopy, Fourier transform infrared spectroscopy and XRD analyses well support all the observed results.     

High density cotton population in late sowing improves productivity and tolerance to cotton leaf curl virus under semi-arid subtropical conditions

Journal of Plant Diseases and Protection - Cotton leaf curl virus (CLCuV) is a menace to cotton productivity in Africa and Asia, especially in Pakistan. Early cotton planting is one of the options...     

Community ecology and spatial distribution of trees in a tropical wet evergreen forest in Kaptai national park in Chittagong Hill Tracts,Bangladesh

We investigated the floristic composition, woody species diversity and spatial distribution of trees in a tropical wet evergreen forest in Kaptai national park in Chittagong Hill Tracks, Bangladesh. We recorded 25 families, 37 genera, 40 species and 1771 woody individuals in a 0.09 ha plot. Euphorbiaceae and Moraceae were the most speciesrich families, and Castanopsis, Ficus and Terminalia were the most species-rich genera. Bursera serrata Wall. ex Colebr. was the dominant species in terms of highest importance value(13%). Trema orientalis(L.)Bl was typically a light demanding species as it appeared in the top canopy with only one individual having the seventh highest IV, but had no regeneration. The expected maximum number of species(Smax) was 140,indicating that many species may invade the forest as the Smax is greater than the recorded total number of species. The nature of the disappearance and appearance of species in the present forest reflects instability of floristic composition. The values of Shannon's index H ′ and Pielou's index J ′(evenness) were 3.36 bit and 0.63, respectively. These values show moderately high species diversity as compared to other subtropical forests in the tropics. In addition, a sample area of 200 m2 in this forest would be sufficient for measuring the diversity indices H ′ and J ′,whereas the trend of J ′may indicate the rate of equality of individuals among the different species decreased with increasing area. The distribution pattern for the total stand was completely random. However, the dominant species showed aggregate distribution for small areas, but random distribution for large areas. The spatial association between species showed that the strongest positive interspecific association occurred between Streblus asper Lour. and Castanea indica Roxb.(ω =0.51). As a whole, most species were weakly associated with each other,of which 58% species associations were completely negative. The result of cluster analysis showed that species pairs were spatially independent at all or most small clusters; stands of species from all clusters are mosaics of complete habitat and pioneer habitat. All patches in this forest community have similar habitat and regeneration niches, which could be a phenomenon for a young growth forest. Thus, the existence of habitat and regeneration niches may be an important factor in the maintenance of diversity in this forest.     

Breeding approaches for bacterial leaf blight resistance in rice (Oryza sativa L.), current status and future directions

Bacterial leaf blight (BLB) is one of the most serious threats to the rice crop in irrigated and rainfed areas of the world. It is caused by Xanthomonas oryzae pv. oryzae and has been known for more than a century. Through rigorous screening and selection, a number of resistant cultivars have been produced and utilized, but resistance was overcome by the development of mutant strains of pathogen and by the dynamic change in Xoo populations. About 38 resistance genes have been reported in rice against the disease and a few have been cloned. The pyramiding of several resistance genes through marker assisted selection has been a quite effective strategy for combating the disease. However, new powerful tools such as transgenics have been introduced to make a significant impact. The purpose of this mini-review is to consolidate the existing knowledge about bacterial leaf blight in rice and the progress made both in conventional as well as in molecular dimensions of breeding together with potential findings and constraints.     

Effects of alumumium on nutrient composition and yield of oats

Spotty chlorosis appeared on the young leaves of Al toxic plants and was severe or high Al level. Stems of the Al‐treated plants were purple While the roots were short, thick and brown in colour with little branching.

The dry matter yield of tops and roots decreased with increased Al level. The concentration of P was greater in roots of Al toxic plants than in the control plants but a converse affect was recorded in tops.

Increased rates of Al caused a decrease in the concentrations of P,K,Ca, M_c and Mn in plant tops, while Al concentration increased both in tops and roots. Iron content in tops affected with increased Al and in root a regular increase was observed. The results indicate that Al toxicity depressed the growth of oats, resulted in abnormal root development with tittle branching and affecting the utilization of several essential plant nutrients by oat plant.