Detrimental Coastline Alteration at Horseshoe Crab Spawning Grounds in Pahang, South China Sea

The unregulated coastal land use in Pahang, East Coast of Peninsular Malaysia, has interfered with the landscape and natural hydrodynamic processes such as tides and currents. The river mouths of Balok and Pahang Tua were subject to anthropic activities and this resulted in sediment transition. Eventually the shore was unfavorable for horseshoe crab spawning activity. Construction of foreign structures including ripraps, land reclamation (parking lot), and jetty renovation between 2011 and 2013 was found to be responsible for the sediment transition from coarse to finer sand at Balok Beach. The nearby mining activities also brought a considerable sediment load to the shoreline. On the other hand, Tanjung Selangor beach also experienced a shift in the sedimentological conditions. A series of coastal alterations in the vicinity that began with sand mining in 2010, followed by jetty construction between 2010 and 2011, and road bridge in 2011–2016, caused a sediment transition into fine sand. Horseshoe crab spawning grounds must not be neglected from protection. We recommend monitoring using hydrographic and soil models so that sedimentation impacts toward shore and river morphology can be forecasted while intervention becomes timely.