Modeling the Efficacy of Three Types of Artificial Timber Reefs in Mitsu Bay, Japan

Abstract

With the aim of simultaneously improving fishery production and utilizing forestry and oyster fishery wastes, three types of artificial timber reefs (ATRs)—constructed from simple timbers, timbers with oyster shells from local oyster farms, and timbers with leaves/branches from forest thinning—were deployed in Mitsu Bay, Japan. We developed a food web model to investigate the relative efficacies of these ATR types compared with the bare, sandy seafloor. The model described the material flow through the food webs formed in each ATR type and their potential to increase fisheries production. The model outputs were validated with observational data over three years. The model fit the observed biomass of both prey animals and fish predators. The simulation results highlighted that ATRs, particularly those with additional materials, had two to three times higher feeding flow than the sandy seafloor and resulted in increased fish biomass. Fish catch doubled in the ATR areas compared to the bare seafloor. Aside from providing a feeding ground, the complexity of the ATRs with additional materials likely acts to provide shelter for juvenile fish. ATR deployment using by-products such as those mentioned above may not only enhance fish stock but also help foster the establishment of a recycling-oriented society.