Brackish Water Shrimp Farming Research Articles

Resource degradation and livelihood in the coastal region of Bangladesh

A study was conducted in four selected upazilas under four coastal districts through participatory rural appraisal (PRA), household survey and monitoring, sampling, focal group discussions, personal interview, onfarm field visits, institutional consultations, and secondary information. The investigation revealed that the valuable natural resources of the whole region are at the verge of serious degradation. Various causes have been identified, which are responsible for degradation of both resources and production environments. These causes include human population growth, coastal embankment, upstream withdrawal of Ganges water, brackish water shrimp farming, salt production, use of agro-chemicals, industrial activities, commercial activities, over-exploitation, etc. The study also showed that the degradation of natural resources is the reason behind the squeezing of historically dominant livelihood opportunities of the coastal communities. The current scenarios of the coastal ecosystem urge necessary steps to be taken for sustainable management of valuable resources and to create alternative livelihood opportunities for the coastal communities.

Economic returns of disease-affected extensive shrimp farming in southwest Bangladesh

One hundred and two brackish water shrimp farms in Shyamnagar Upazila of Satkhira District, Bangladesh, were surveyed to study their costs and returns. Key data were collected, using a questionnaire survey from January to August 2002. Profitability of operations was affected by fluctuating yields and prices due to diseases, and generated economic risk. The average total cost of production per hectare was 63,437.57 Bangladeshi taka (tk) (US$1,084.40/ha). The farmers achieved a variable yield of black tiger shrimp (Penaeus monodon), ranging from 7.48 kg/ha to 455.03 kg/ha, with a mean yield of 146.39 kg/ha, through multi-stock and multi-harvest methods. The gross and net incomes per hectare were tk49,999.87 (US$854.69) and tk40,307.04 (US$689.01), respectively. Of the total biomass, 44% came from P. monodon, while the rest (23% and 33%) came from other shrimp and finfish respectively. The return to total cost of P. monodon was a negative profit (tk0.78).

Seed supply for coastal brackishwater shrimp farming: environmental impacts and sustainability

Globally, shrimp farming has been a significant agro-based economic activity since the early 1970s. Because it offered a huge immediate economic return, shrimp farming showed a booming expansion and soon became a multimillion dollar industry. However, it has been under extreme criticism because of its devastating ecological and socio-economic impacts. Because seed is the primary input, the impact from farming has started from the source of seed supply, so that not only are natural stocks of shrimp seeds now overexploited worldwide but seed collection activities also significantly reduce stocks of other living resources. Although hatcheries were developed as potential alternative and have replaced the natural seed source to a great extent, large-scale hatchery productions provide a potential source of coastal pollution. However, this area is still poorly studied. The present paper provides a review of the environmental impacts of the wild shrimp seed fishery as well as the possibility of environmental degradation from artificial shrimp seed production in hatcheries.

Water and sediment quality, partial mass budget and effluent N loading in coastal brackishwater shrimp farms in Bangladesh

The present study aimed to quantify the water and sediment quality and growth and production parameters and to establish nutrient budgets for an average of five selected semi-intensive shrimp ponds in Bangladesh over a growing cycle. Physico-chemical parameters of water and sediments were measured and analyzed by standard methods. Gross yield (kg ha −1) of shrimp was calculated from the stocking and harvesting data. Finally, a partial nutrient mass budget for N and P was calculated. Most of the parameters of water and sediments correlated significantly with each other suggesting a high degree of interactions between different parameters in the system. Significantly higher concentrations of all species of nitrogenous nutrients were recorded in the effluent waters than that entering into the ponds. Therefore, a high loading and net output of nitrogenous nutrients in effluent waters was documented. The study also indicated a net discharge of solids and minerals through effluent loading. However, significantly lower concentrations of phosphorus in the effluent water indicated a net retention and trapping of phosphatic nutrients in the environment. Total production ranged between 532.0 and 697.0 kg ha −1 cycle −1 and P. monodon production between 484.0 and 562.0 kg ha −1 cycle −1. Ponds gained nitrogen primarily from intake water (55%) and fertilizers (29%), and nitrogen was lost primarily from water exchange (78%) and harvested shrimp (12%). Phosphorus gain occurred mostly from intake water (52%) and fertilizers (25%), and phosphorus was lost primarily from water exchange (52%) and harvested shrimp (3.3%). About 10% of input nitrogen and 44% of phosphorus were not accounted for in measured losses, and presumably were fixed or metabolized in the system. On average, 78 g N was discharged to and 25 g P was removed from the surrounding water by the system for each kilogram of shrimp produced. Mean conversion of feed nitrogen and phosphorus to shrimp flesh averaged 74% and 40%, respectively. It was concluded that semi-intensive systems serve as net supplier of N to and net remover of P from the surrounding water.

Impact of seawater intrusion control on the environment, land use and household incomes in a coastal area

Agricultural production in the coastal wetlands of Asia is often hindered by salinity intrusion caused by tidal fluctuation. This paper reports changes in environmental and socio-economic conditions that followed the phased construction and operation of sluices for controlling seawater intrusion from 1994 –2000 in a coastal area of the Mekong River Delta, Vietnam. Canal water salinity decreased rapidly upstream of sluices, allowing rice cropping intensification and increased rice production in the eastern part of the study area. However, the livelihoods of farmers in the western part were adversely affected due to cessation of supply of brackish water that was needed for brackish-water shrimp farming, while the acid sulphate soils present there posed problems for rice cultivation. The poor farmers and landless people suffered more because the fishery resource that they depended on declined sharply due to reduced salinity and increased acidity in the canal water. The findings confirmed that the environment and resource use in the coastal lands are very sensitive to external intervention. A clear understanding of the socio-economic and environmental impacts of salinity control measures in coastal areas can help planning to enhance farmers' incomes while minimizing negative environmental impacts. Land-use policy formulation, planning and management should adopt a more holistic approach, taking into account the interests of all resource users, especially the poor, instead of focusing on any particular sector.

A field survey of chemicals and biological products used in shrimp farming

This study documented the use of chemicals and biological products in marine and brackish water shrimp farming in Thailand, the world’s top producer of farmed shrimp. Interviews were conducted with 76 shrimp farmers in three major shrimp producing regions, the eastern Gulf coast, the southern Gulf coast and the Andaman coast area. Farmers in the study used on average 13 different chemicals and biological products. The most commonly used products were soil and water treatment products, pesticides and disinfectants. Farmers in the southern Gulf coast area used a larger number of products than farmers in the other two areas. In the study, the use of more than 290 different chemicals and biological products was documented. Many of the pesticides, disinfectants and antibiotics used by the farmers could have negative effects on the cultured shrimps, cause a risk for food safety, occupational health, and/or have negative effects on adjacent ecosystems. Manufacturers and retailers of the products often neglected to provide farmers with necessary information regarding active ingredient and relevant instructions for safe and efficient use.

The effects of zeolites and other alumino-silicate clays on water quality at various salinities

Intensive marine and brackishwater shrimp farms commonly use large quantities of zeolites in ponds with the aim of removing ammonia through ion exchange, providing physical cover over sediments to prevent leaching of metabolites into the water column, removing suspended solids, and improving water colour and diatom blooms. Zeolites have the capacity to remove ammonia and other nutrients/ metabolites from fresh waters by ion exchange and absorption. However, there are doubts as to their efficacy and cost-effectiveness in saline waters. This research was conducted to investigate the effect of zeolites on water quality under a range of conditions in seven laboratory-based trials and one pond trial. These investigated the effects of six types of commercially available zeolites and three other alumino-silicate clays at levels from one to 26 times the recommended dose rate (380 kg ha-1 month-1) in water at salinities of 0-30%o for periods of 3-19 days. The results indicated that none of the zeolites or natural alumino-silicate clays from Thailand had any significant effects on the removal of nutrients from water at salinities of 0-30%. Neither were these able to prevent nutrient emission from shrimp pond sediments in water at 20-2l%o salinity. Furthermore, none of the other suggested functions of reducing levels of particulate nutrients, enhancing algal biomass, or affecting oxygen and pH dynamics were evident. This study could not establish any useful, cost-effective role for zeolites in shrimp pond culture.