Abstract
Coastal wetlands have been gradually developed by aquaculture and other anthropogenic infrastructure, reducing the habitat for water birds. The traditional operation of shallow-pond milkfish (Chanos chanos) aquaculture in Taiwan may provide a model for aquaculture production that operates in harmony with overwintering water birds. The goal of this study was to test whether experimental water drawdown of aquaculture ponds, following the seasonal, traditional milkfish aquaculture, can create resource pulses that attract water birds in Tainan City in southern Taiwan. This experiment tested four types of aquaculture with potential for application: wild fish, no-feed tilapia, milkfish, and tilapia with feed. Ponds were surveyed every other day for water depth and water birds at least 37 times in four winters after water drawdown. In general, drawdown ponds created resource pulses that attracted higher feeding bird densities and numbers of species than control ponds in all aquaculture types. Milkfish ponds often had higher water birds in each year. Deep waders were sometimes the most abundant guild in the control, whereas shorebirds, shallow and deep waders were often higher in the drawdown treatment. Bird densities and numbers of species were correlated with water level, benthic biomass and water Chl a, but not with tilapia biomass. Species, such as Black-faced Spoonbills (Platalea minor), responded to water levels with the exception of Little Egrets (Egretta garzetta). The operation of seasonal, traditional shallow-pond milkfish aquaculture is suitable for foraging of water birds during the winter migratory bird season.
Highlights
Coastal development, including aquaculture and mariculture development, has significantly changed wetland ecosystems around the world, reducing habitats and affecting biotic communities [1,2,3,4]
Over the 4 years, densities and numbers of species of shorebirds, shallow, deep waders and ducks differed among water depth ranges in different aquaculture types, whereas other water birds were higher in water depth ranges >5 cm, but only in milkfish ponds (Table 2)
Bird densities of aquaculture types in the drawdown treatment were higher over the 4 years except no-feed tilapia in the 1st year and milk fish in the 4th year
Summary
Coastal development, including aquaculture and mariculture development, has significantly changed wetland ecosystems around the world, reducing habitats and affecting biotic communities [1,2,3,4]. Migratory water birds, relying on coastal wetlands, are among the most vulnerable groups of organisms in coastal areas and have continuously declined in numbers of species on the East Asian—Australasian Flyway [5,6]. To resolve conflicts between food production and biodiversity, the Convention of Biological Diversity declared that Satoyama landscapes are effective for keeping production in harmony with nature [7]. Many examples of traditional agriculture systems around the world provide food products and maintain diverse landscapes and biodiversity [8,9]. Few examples are present in the coastal aquacultural areas [10]. To facilitate the harmony between aquaculture and water birds, we need to find traditional and/or innovative solutions before formulating conservation policy
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