Fisheries production in Southeast Asian Farmer Managed Aquatic Systems (FMAS): II. Diversity of aquatic resources and management impacts on catch rates

Abstract

Southeast Asian rice farmers often manage aquatic habitats and resources on their land to increase harvest of aquatic animals (Amilhat, E., Lorenzen, K., Morales, E.J., Yakupitiyage, A., Little, D.C., 2009. Fisheries production in Southeast Asian farmer-managed aquatic systems (FMAS). I. Characterisation of systems. Aquaculture 296, 219-226). We characterize the diversity of aquatic resources harvested from such Farmer Managed Aquatic Systems (FMAS) and evaluate the effectiveness of management practices within contrasting FMAS in Cambodia, Thailand and Vietnam. Farmers harvested diverse self-recruiting species (SRS) from FMAS in all study areas: 24 locally recognized species in Cambodia, 66 in Thailand and 17 in Vietnam. Fish accounted for the largest share of SRS by weight in all areas but frogs, snails, crustaceans and insects were also important. Amphibious species, well adapted to rice farming landscapes, dominated catches of both fish and non-fish SRS. Stocked cultured species (CS) comprised only fish, were less diverse and differed between countries according to aquaculture practices. SRS catch rates in FMAS were significantly higher than wild animal catch rates in open aquatic systems in Cambodia and Thailand, indicating an underlying difference in abundance. This positive effect is likely attributable to lower harvesting effort in FMAS (where access was restricted to owners), agricultural inputs, and management measures aimed specifically at increasing aquatic animal production. Various management measures were recorded, but only the construction of brush parks and fertilisation was associated with positive effects on catch rates in the SRS-dominated FMAS of Cambodia and Thailand. Ponds in Vietnamese FMAS were managed intensively as carp polyculture systems, and catch rates within them responded positively to a wide range of management inputs. FMAS support a high abundance of aquatic animals including diverse SRS and benefit nutrition and income of farming households, agro-ecosystem services, and biodiversity conservation.