The population structure and parasitic relationships of oyster (Crassostrea angulata), Arcotheres sinensis (Pinnotheridae), and Rhopalione sinensis (Bopyridae) at the oyster reefs of western Taiwan

This study examined the relationships among hosts, parasites, and hyperparasites of oyster farming on the west coast of Taiwan from June 2012 to August 2013. In a region of Taisi (Taiwan), which was composed of near coast and far coast racks, a total of 77 155 oysters were collected. Among them, 1166 oysters were parasitized by pea crabs, with the rate of parasitism of oysters by the pea crab, Arcotheres sinensis (Shen, 1932) being 1.51%. A total 1523 pea crabs were collected with a sex ratio of females to males of 1.03 : 1. A total of 285 bopyrid isopod parasites Rhopalione sinensis Markham, 1990 were collected from the pea crabs. The hyperparasitic rate of female pea crabs was 22.1%, and the sex ratio of female to male isopods was 1.16 : 1. Most of the pea crabs entered their hosts when the crabs were small, which allowed them to grow within the host.