Role of nematodes as bioindicators in marine and freshwater habitats

摘要

The utility of bioindicators has been established in recent times. The utilization of nematodes as a tool in water quality assessment in the 1970s (refs 3 and 4) was popular and their faunal composition emerged as a useful monitor of environmental conditions and ecosystem function. The parasitic copepods, digeneans, cestodes, acanthocephala and larval nematodes have dominated in the role of parasite indicators. But the host-parasite relationships involving adult nematodes have rarely been reported in the investigations identifying parasites as indicators. The subject of this investigation has been catfishes of two zoo-geographically different regions within the same country. Adult roundworms of genus Rostellascaris were recovered in the two-year study (Figure 1) during 1996-98 from Mystus tengra of river Ganges, Allahabad. Another catfish, Arius falcaris, examined in the Arabian Sea at Goa during 2000-2001 revealed another species of RosteUascaris namely R. oceanica. Studies making use of biological tags for stock delineation in intraspecific groups within a catfish host population at different geographic locations, are not very frequent. However, their role in substantiating differential spawning, nursery or feeding grounds, and behavioural forms of such groups or stocks within the same area, has been amply demonstrated. The objective of this investigation was to analyse restrictive population distribution behaviour of the nematode parasites and to determine useful discriminants for commercial exploitation in fish and fishery.