Effect of Silt and Clay on the Settlement of Short-necked Clam Ruditapes philippinarum Larvae

Abstract

In this study, we investigated the effect of silt and clay in the sediment on the settlement of Ruditapes philippinarum larvae. Mountain, river and sea sands of which silt and clay (< 0.075 mm) content was adjusted using silt and clay originating from these sands or dredged sediment (DS) were examined for settlement of R. philippinarum larvae. The addition of DS and Otagawa river sand-originated silt and clay did not accelerate the larval settlement, whereas the mountain and Jigozen sea sands-originated silt and clay promoted larval settlement at 5%. The negative impact of Otagawa river sand-originated silt and clay might be due to its high leachability of Mn, while the accelerated larval settlement by Jigozen sea sands-originated silt and clay could be attributed to its organic contents. The provided results indicate that a suitable ratio of the fine particles to coarse particles exists for the acceleration of the larval settlement, though the effect might be dependent on their chemical properties.Keywords: larval settlement, restoration, Ruditapes philippinarum, silt and clay, tidal flat INTRODUCTION Short-necked clam (Ruditapes philippinarum) resources in Japan have been decreasing for decades. To maintain the clam production, cultivated young short-necked clams have been transplanted to clam fishery areas. As for the causes of decrease in short-necked clam resources, deterioration of the sediment environment and decrease in number of their larvae in seawater were reported (Ishii et al., 2001;Sekiguchi and Ishii, 2003). Therefore, restoration of the sediment environment is an important task to reestablish clam habitats for the natural recovery of short-necked clam resources.

Antioxidant Responses of a Brackish Water Clam to Sediment Composition and Water Quality: a Field Experiment

“…Previous studies have examined sediment quality and its effect on the C. fluminea clam species, which exhibits significant biological stress [20]. Other studies have reported similar effects in the settlement of different clam species [21,22], and few studies have examined survival following eutrophic-driven changes in the food supply and habitat [6,[23][24][25][26] as well as biochemical alterations due to salinity and food availability [4] on brackish-water clams. However, to the best of our knowledge, the ORAC responses of C. japonica to sediment composition and water quality have not yet been investigated in actual brackish environments.…”