Abstract:Mudflat in the Yellow River Delta is the main production region of shellfish in Shandong Province. To enable economic development, the mudflat was greatly exploited, natural condition of the mudflat was disturbed, and the shellfish habitat was constantly subjected to changes. Based on remote sensing (RS) data and geographic information system (GIS) technology, the mudflat shellfish habitat in the Yellow River Delta data were obtained, and its spatio-temporal variation over the past 30 years was analyzed. For this study, a collection of Landsat images taken during the lowest tidal levels during 1986—2017 were selected as the data source and six images were used in the study. To extract the mudflat shellfish habitat, we chose the instantaneous waterline as the lower boundary and the reclamation dyke, aquaculture pond, or mean high tide line combined with vegetation line as the upper boundary. The results showed that the shellfish habitat area continued to decline from 1986 to 2017, from 1188 km2 in 1986 to 396 km2 in 2017. The variations were the most obvious during 1993—2001 and 2008—2013, and the average annual reduction area was approximately 34 km2. In terms of space, the Diaokou section showed a drastic variation, and the lower boundary expanded slightly to the sea during 1986—1993. However, the upper boundary moved toward the sea and the lower boundary retreated to the land during all other periods, and the area was greatly reduced. As for the estuary, its upper boundary was stable. At the lower boundary, deposition and erosion alternated due to the dual effects of runoff, sand transportation, and marine dynamic erosion, but the area changed only slightly on the whole. The factors influencing spatio-temporal changes in shellfish habitat were evidently different. Occupation by salt fields, aquaculture ponds, and engineering constructions were the main reasons for the changes in the Diaokou and Laizhou Bay sections. The estuary was mainly affected by changes in runoff, sand transportation, and marine dynamic erosion. However, in the Dongying Harbor and its adjacent section, habitat function was completely lost because of the construction of ports and oilfields.
