Title Macrobenthos, current velocity and topographic factors as indicators to assess the assimilative capacity of fish farms: Proposal of two indices
Authers Hisashi YOKOYAMA, Misa INOUE and Katsuyuki ABO
Keywords Fish farm, Assimilative capacity, Current velocity, Environmental criteria, Plaster ball
Citation Bull. Fish. Res. Agen. supplement No. 19,89-96, 2007
Abstract
In order to provide site selection guidelines for fish farming, two indices have been previously proposed based on surveys of the macrobenthos and bottom environments conducted at fish farms in Kumano-nada, central Japan. In this review, these results are summarized, and requisites for determining the limit of maximum fish production are discussed from a standpoint of assimilative capacity of fish-farm environments. An index ‘ED' (Embayment Degree) is calculated from the distance from a bay mouth to a fish-farm site, the width of the bay, the water depth of the site and the maximum depth at the bay mouth. Another index, ‘ISL' (Index of Suitable Location) is calculated from the water depth and current velocity under a fish cage. Current velocities can be estimated by plaster balls readily and simultaneously at many stations. Biotic and abiotic factors at the fish farms were found to be changed along gradients of fish production and ED or ISL, suggesting that these indices are effective for estimating the assimilative capacity. ED can be used as a simple indicator for the site selection. ISL has a wider potential application to assess the assimilative capacity under a variety of topographical conditions.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull19/11.pdf