Long-term monitoring of the demersal fish community in a steel-slag disposal area in the coastal waters of Kaohsiung, Taiwan

Dumping of approximately two million tonnes of steel slag in a shallow (ca. 40 m), sandy-bottom area in southern Taiwan from 1984 to 1989 has caused major changes of the substrate. After cessation of slag disposal, the demersal fish community in the area was monitored for 9 years (1990-1998). Species richness and the Shannon diversity index at the disposal site and a control site were significantly different, while the number of individuals and the Index of Multivariate Dispersion, as a measure of relative variation, were not. Splitting the data according to three 3-year periods did not reveal significant differences in any of the univariate community metrics. However, multivariate analysis revealed significant temporal differences, dispersion becoming smaller over time. It is concluded that slag disposal created a reef-like habitat and the associated fish fauna had a higher diversity than that seen on the sandy bottom present originally, partly caused by increased habitat complexity and partly by diversion of fishing activities because of potential gear damage. However, in the long run the ecological benefits may not last because the habitat is gradually being covered up again by sand. (C) 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.