A preliminary report on the marine Macrobenthos and the Demersal fish fauna of the island of Filfla (Maltese Islands, Central Mediterranean)

Abstract

The nature, distribution, and abundance of the main component species of the supralittoral, mediolittoral and upper infralittoral marine macrobenthic assemblages of Filfla were studied during a series of expeditions to the islet between 1990 and J 994. The demersal fish fauna was censused by direct observation. The distribution of sponges was studied along two 2m-wide belt transects laid along a gently sloping and a steep sloping bottom, respectively. In general, the same type of benthic assemblages as found on other exposed rocky coasts in the Maltese Islands occurred at Filfla. However, at Filfla, the littoral zones were compressed, and species richness and abundance in the littoral and sublittoral were generally low compared to other exposed rocky shores in the Maltese Islands. In spite of the extensive infralittoral sandy bottoms present at Filfla, no sea-grass meadows were encountered. Most of these differences are probably attributable to the high exposure, the extensive boulder shores and submarine boulder fields that surround the islet, and to bottom turbulence. Large differences in species composition and abundance of sponges were found between the two transects. Crambe crambe and Agelas oroides were the most abundant sponges on the steep bottom, while Sarcotragus spinosula was the most abundant species on the more gently sloping one. Compared to that of mainland sites, the demersal fish fauna of Filfla was impoverished in terms of both species richness and abundance.