World Aquaculture Magazine - March 2021

38 MARCH 2021 • WORLD AQUACULTURE • WWW.WA S .ORG primary data of the CGIAR Challenge Program onWater and Food – Ganges Basin Development Challenge (CPWF-GBDC) component. Characteristics and Operational Approach of Shrimp Farming in Bangladesh Extensive shrimp ponds in Bangladesh are less than 1 ha in size and shallow (Table 1). Survival and annual yield is also very low compared to extensive shrimp farming as practiced in the Mekong Delta in Vietnam (Anh et al. 2020, Brennan et al. 2008) and lower than the carrying capacity of standard shrimp ponds (Muqsith et al. 2019, Song et al. 2020). Relatively low survival and yield could be due to the farming landscape. As indicated by FGD participants (Table 1), disease outbreaks are more likely at the beginning of the monsoon and heavy rainfall can quickly alter the salinity and pH of shallow shrimp farms. The weaker health and immunity of non-fed shrimp leads to disease, low survival and reduced annual yield. In traditional practice, farmers have developed their own mechanism of reducing the risk of disease losses through multiple stocking management. The virulence of white spot syndrome disease (WSSD), the most common shrimp disease in Bangladesh, is linked with life stages (Kasornchandra et al. 1998). Of the three multiple stocking patterns described in Table 2, pattern one is most common as it gives farmers more flexibility for financial arrangements for farm operation. The majority of farmers operate farms on their own land and use their own labor in farmmanagement. They do not consider the lease value of the land and their own labor as investments. The cost of shrimp seed (post-larvae) is the major operational cost (Table 3) which constitutes 66 percent of the overall operational cost. Though the operational cost is almost US$ 1000, it is still much less in comparison to other southeast Asian Introduction Shrimp is the fastest-growing and most-traded aquaculture species by value (FAO 2020). Among consumers it is often perceived that shrimp are produced in intensive systems that require a huge investment. Shrimp farming is also blamed for the loss of mangrove wetlands (Ashton 2008), damage to coastal agro-ecosystems (Hossain et al. 2013) and taking away the livelihood of poor farmers (Islam 2006). However, these notions are not always representative of the practical reality. Due to many changes in coastal agro- ecosystems, driven by climatic and anthropogenic factors, some areas are not suitable for cultivation of other crops and where shrimp provides the only viable livelihood option for millions of people (Shameem et al. 2015). According to a recent global assessment, around 50 percent of the total shrimp farming area is still extensive and operated mainly by smallholders (McNevin and Boyd 2018). There are major areas of extensive shrimp farming in Bangladesh and Vietnam (McNevin and Boyd 2018). Although productivity and farm management of extensive systems are going through progressive changes in Vietnam (Anh et al. 2020), the situation in Bangladesh is more static (DOF 2001, 2020). To better understand the context, this study focused on characterizing extensive shrimp farms in Bangladesh, analyzing national productivity trends from 2000, listing key innovations demonstrated in the last ten years and exploring the reasons why farmers are not able to adopt improved farmmanagement practices. Shrimp farmers (n=769) from Khulna division of Bangladesh, the major shrimp farming area of the country, were surveyed to collect data for characterization of farming systems. In addition, three focus group discussions (FGDs) were organized in Satkhira district of Khulna division, where the greatest number of shrimp farms are located. National productivity trends were calculated from government statistics and key innovations for improving productivity was derived from One Hundred Dollar Shrimp Farming K.A. Kabir, R.H Sarwer, M.A. Haque, S.B. Saha, M. Karim and M. Phillips TABLE 1. General features of extensive shrimp farms in Bangladesh. Farm size (ha) 0.73 Water area (ha) 0.65 Water depth (m) 0.4 (dry season) 0.7 (wet season) Water exchange Yes 1 Culture species Penaeus monodon Stocking pattern Multiple 2 Stocking density (PL/m 2 per yr) 14.1 3 Feeding No Aeration No Use of chemicals Lime, organic and inorganic fertilizer Hired labor (man days/yr) 20 4 Survival (%) 8.3 5 Disease outbreak More at the start of monsoon. Continues throughout the year. Relatively less at low salinity Harvesting Multiple 6 Annual yield (kg/ha) 294 1 Fr equenc y o f wa t e r e x change var i e s among t he f arms ba s ed on i t s pr ox imi t y t o r i v e r s and/o r i r r i ga t i on cana l s o f t he f armi ng c l us t e r . 2 Thr ee ma j o r s t o ck i ng pa t t e rns hav e been obs e r v ed (Tab l e 2) . 3 The av e rage annua l s t o ck i ng dens i t y o f t he t hr ee ma j o r s t o ck i ng pa t t e rns ba s ed on t he pr opo r t i on o f f arme r s prac t i c i ng . 4 I nvo l v emen t o f h i r ed l abo r var i e s by mon t hs and i s ma i n l y r equ i r ed dur i ng f i na l har v e s t i ng and a f t e rwards f o r ma i n t enanc e o f t he f arm dur i ng t he non - f armi ng wi n t e r pe r i od . 5 Sur v i va l l ar ge l y var i e s among f arms and i s d i f f i cu l t t o ca l cu l a t e . I t i s e s t ima t ed ba s ed on t o t a l numbe r har v e s t ed (annua l y i e l d/av e rage shr imp we i gh t ) d i v i ded by t he t o t a l s t o ck i ng t hr oughou t t he y ear . 6 Har v e s t i ng s t ar t s a f t e r 1.5 mon t hs o f s t o ck i ng and c on t i nue s e v e r y 3-5 day s ar ound e v e r y f u l l moon and new moon pe r i od un t i l Nov embe r .