Response of the fish assemblage structure in a small farm pond to management dredging operations

Artificial water bodies, including farm ponds, contribute to regional biodiversity by providing alternative habitats for many species. Although management operations, such as dredging, are commonly conducted in farm ponds to maintain their function, little is known about the effects of habitat change associated with such operations on fish assemblages. The objective of this research was to examine the relationship between fish assemblage structure and pond management and via a comparative study before and after a dredging event. It was found that the fish assemblage structure was significantly different after the dredging event. Before dredging, extensive growth of aquatic macrophytes and low dissolved oxygen level were observed. Only two Cobitidae species, which have a tolerance to dissolved oxygen depletion, were recorded just before dredging. After dredging, the dissolved oxygen level and number of fish species had increased. The results indicated that management operations could change the fish assemblage structure via a shift in the dissolved oxygen level associated with changes in macrophyte coverage.