Integrated and collaborative ecological and socio-economic modelling for sustainable razor clam management at Don Hoi Lord Ramsar Site, Thailand

Abstract

Don Hoi Lord wetland located near Mae Klong river mouth in the area of Samut Songkhram province, upper the Gulf of Thailand. The wetland was registered as the 1099th Ramsar site. Razor clam (Solen regularis) is an important species in the sandbars which are a part of this wetland. Fisherman has harvested razor clam for generating income more than 2 generations. Due to the previous studies, razor clam population has decreased since 1981. The objective of this study aims to explore possible sustainable management policies for Don Hoi Lord by using Companion Modelling approach (ComMod). The approach mainly consists of Agent-based simulation model (ABM) and participatory simulation workshop with stakeholders involvement. To achieve the aim of the study, there are 3 parts including: 1) ecological study of razor clam population and its environmental factors especially sediment and particulate organic carbon (POC) between June 2008 – May 2009; 2) socio-economic study to understand fisherman harvesting behavior and razor clam market mechanism; and 3) ABM development from field study finding and test the agreeable management scenarios with stakeholders. Moreover, the ABM was used in participatory simulation workshop to validate the ABM and to exchange and discuss on razor clam sustainable management. The results from ecological study showed that razor clam population density was in crisis due to the decreasing of mean density to 0.51±0.30 clam/m2 as the lowest record among previous scientific studies. In addition, razor clam density had negative correlation with %organic matter in soil sediment and particulate sediment in water column (p < 0.05) but it was not correlated with POC. Razor clam market mechanism driven by a trader who buys all razor clam from a fisherman and processed razor clam as clam meat before distributing to market. A buying price is set independently by traders based on their razor clam stock and a current market demand. Regarding fisherman, there were 2 factors affected fisherman’s decision to harvest razor clam, which are the density of razor clam and the price of razor clam. Due to the low razor clam density, fishermen would change to harvest on other species instead of razor clam but razor clam is still their preference. The ABM development was done by added i-stage distribution model and re-calibrated until the simulation model represented system behavior. Then, the management scenarios were tested by the ABM and found that reserved zoning in cooperation with individual quota system was the best scenario for sustaining razor clam population. Next, spatial interface of the ABM was upgraded based on socio-economic finding and the upgraded ABM was used in participatory simulation workshop with stakeholders. The workshop can be a forum for discussion among stakeholders by using ABM as mediator and sharing their representations for collective agreement to achieve sustainable management.