A closer look into shrimp yields and mangrove coverage ratio in integrated mangrove-shrimp farming systems in Ca Mau, Vietnam

Shrimp aquaculture is the biggest source of export income in Vietnam. However, the development of the shrimp poses a serious threat to coastal mangroves by converting coastal mangroves into shrimp farms. Much effort has been made to replant mangroves and reduce the impacts of shrimp farming on the environment, and maintaining mangrove coverage at 30-50% of total farm area has provided the highest benefits in the integrated mangrove shrimp model. In this study, we re-examine the benefits of forest cover on the survival and yield of tiger shrimp (Penaeus monodon) in the integrated mangrove shrimp farming systems in Ca Mau province, Vietnam. The study found positive linear correlations of log transformed survival and yield of tiger shrimp with forest cover of the forms: Ln (survival) = - 1.39 + 0.038 x forest coverage (r(2) = 0.22; p value = 0.0007); Ln (yield) = 3.55 + 0.026 x forest coverage (r(2) = 0.16; p value = 0.004). The households with high forest cover (i.e., > 45%) also had 1.07 +/- 0.29 and 1.39 +/- 0.36 (CI 95%, p value = 0.000) kg ha(-1) higher yield per night harvest than those with medium and low forest cover, respectively. As a result, households with high forest cover have higher benefits than those with lower forest cover. Our findings together with previous published studies lead to the recommendation that farmers maintain mangroves in farming systems for better economic and environmental benefits.