An Experimental Investigation on the Fishes Associated with Drifting Objects in Coastal Waters of Temperate Australia

The association of fish with natural and experimental drifting objects was investigated in the coastal waters near Sydney, Australia (during 1990). Controlled experiments were conducted using small fish attraction devices (FADs) and algae obtained from reefs to test the effects of drift time, size, color and type of object on the fish attracted; 'control seines' were done in open water. Total densities of fish were generally higher around the natural drift algae and experimental drift objects than in the adjacent open water. Although well pigmented juvenile fish were most abundant, some larvae and a few adults were also caught around drift objects. Families of fish associated with the drift algae included juvenile mullids, pomacentrids and teraponids as well as larval ambassids and gerreids. Fish were quickly attracted to FADs of different sizes and colors and to experimental algae, Patterns of colonization by fish to drifting objects varied among sampling times, often due to very low numbers of fish captured on some sampling occasions. Families of fish caught around FADs in great numbers that were present in low abundance in open water included pelagic, reef and estuarine-associated fish as follows: juvenile carangids, sphyraenids, mullids, mugilids and larval ambassids, sillaginids, sparids and gerreids. When large numbers of fish were captured, similar densities and types of fish were attracted to all types of FADs and experimental algae. Many larval fish demonstrated no affinity for algae with high numbers caught in open water and around the drifting objects (e.g., clupeids and atherinids). Drift objects influence the distribution of fish in surface waters. FADs provide a useful method for the collection of small fish and as tools for conducting controlled experiments.