Community ecology of the metazoan parasites of the Indian mackerel Rastrelliger kanagurta (Scombridae) from the coast of Visakhapatnam, Bay of Bengal.

One hundred and eighty four specimens of the mackerel Rastrelliger kanagurta collected from fish landings at Visakhapatnam coast, Bay of Bengal, between January 2006 and 2007, were examined for analysis of their metazoan parasite community structure at infra and component community levels and study the effects of season and host body length on these communities. Fifteen species of metazoan parasites were collected including 3 spp. Monogenea, 7 spp. Digenea and 5 spp. Copepoda. All the fish were parasitized by one or more metazoan parasite species. A total of 2,004 parasites were collected with a mean of 10.9. The majority were digeneans accounting for 42.4% of total number of parasites collected and the hemiurid Lecithocladium angustiovum is found to be the most dominant species. Mean values of species richness (3.0 ± 1.5), abundance (12.4 ± 9.3) and diversity (H' = 0.92) were within ranges observed for most of the metazoan parasite communities of marine fish from temperate and tropical countries. Seasonally, the mean diversity and parasite species richness of infracommunities were high during December and January and low during September-October. No correlation was found between host total length and any of the community descriptors. Most of the parasites i.e., 12 out of 15 species of parasites collected were host specialists. Only one species Aponurus laguncula was a host generalist. All taxa of metazoan parasites showed a typical over-dispersed pattern of distribution. The dominance of the core species in all the infracommunities and the high degree of host specialization of the parasite species resulted in the predictable component in the infracommunities to be high, each infra community comprising a core species accompanied by a few secondary species.