Agriculture and fisheries production in a regional blending and dynamic fresh and saline water systems in the coastal area of Bangladesh

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With the increase of salinity, shrimp monoculture is a typical production system on many global coasts. They are thus inviting commercially valuable exotic shrimp species that threaten the population of natives and causing alteration of ecosystem function. This intentional introduction and redistribution of shrimp species is an Anthropocene feature of the global coast. Therefore, we investigated how the coastal system breaches a freshwater system leading to more saline-friendly production. Spatiotemporal mapping showed the scope of diversified coastal livelihood that illustrate the coexistence of saline and sweet water-based production system in Bangladesh with a mean accuracy of 89% (kappa statistics 0.86). In many parts, the once agriculturally dominated landscape has transformed into aquaculture to produce shrimp, crab, fish, and salt. Continuous Change Detection and Classification (CCDC) algorithm also depicts the breakpoint in time series of normalized difference vegetation index (NDVI) data due to coastal land-use change. This dynamism includes the strong presence of mixed rice-shrimp culture in Assasuni (west coast) and Chakaria (east coast), as well as salt panning in Chakaria and paddy rice production in Kalapara (mid-coast). Thus those areas are more resilient because many other coastal communities primarily depend on shrimp or aqua monoculture, having limited or no alternative production system. Due to semi-intensive shrimp cultivation, biotic depletion, disease, pollution like antibiotics, nutrients, and organic matter loads are also less than the global coast's intensive aquaculture area. This study revealed the need for a blended fresh and saline-based production system. The findings can be used as a reference in the formulation and implementation of sustainable coastal management policies.