Development of a seagrass-fish habitat model-I: A Seagrass Residency Index for economically important species

Seagrass plays a major role in supporting the processes and function of the marine environment and is a key fisheries habitat, which provides nursery, feeding and breeding areas for fish and crustaceans. Seagrass beds also stabilise the seabed, trap sediments, reduce coastal erosion and provide the basis for the food chain through photosynthesis. The goal of this project is to establish a seagrass–fish habitat spatial model that will quantitatively assess the economic value of seagrass habitats, particularly for fisheries production and this paper describes a preliminary step in the model construction. With the help of fisheries scientists from the South Australian Research and Development Institute (SARDI), the functional relationship of some economically important species of fish, crustaceans and molluscs to seagrass habitats was investigated. As a result, a ‘seagrass residency index’ (SRI) fior some species has been estimated indicating the species most likely to be affected by changes in health and abundance of the seagrass beds in the coastal waters of South Australia. The information collected mainly relates to the periods of time spent amongst seagrass beds, sheltered reefs and open waters at different life stages of the fish: larval/juvenile, adult/feeding and adult/spawning. It was then hypothesized that the SRI would be a weighted sum of the averages of the estimated residence time at each stage. This paper describes how the SRI figures were calculated and outlines the intended use of the indices, in conjunction with other information, to assess the value of seagrass habitats. Copyright © 2000 John Wiley & Sons, Ltd.