| Popis: |
Oyster drills are common on rocky shores and oyster (Crassostrea gigas) farming areas in Taiwan. Most studies on the oyster drill (Thais clavigera) were on its impact on the oyster industry. However, there are at least three Thais species in the west coast of Taiwan. And the basic biology of T. rufotincta and T. keluo was insufficient. Thus, the present study was undertaken to investigate population biology of the three congeneric drills(Thais spp.), including feeding rate, reproductive characters and population dynamics. T. clavigera was distributed from Tamsui to Tongkong along the west coast of Taiwan. But, it was rare at Tongkong. T. keluo was primarily found at Tamsui and Tongkong. The distribution of T. rufotincta was from Tongkong to Tamsui and mostly occurred between Tongkong and Taishi. Mean feeding rates (¡ÓSE) of T. clavigera, T. keluo and T. rufotincta were 0.054(¡Ó0.010), 0.038(¡Ó0.004) and 0.010(¡Ó0.003) oysters/snail¡Eday, respectively. The feeding rate of T. rufotincta was significantly lower than other species (PTamsui>Shiangsan for T. clavigera, Tamsui > Tongkong for T. keluo, and Chiku > Tongkong for T. rufotincta. It is suggested that water temperature and food abundance are important factors affecting drills¡¦ growth in the west coast of Taiwan. The recruitment of T. rufotincta at Chiku and Tongkong had two peaks. It was different from T. clavigera and T. keluo with only one peak. Futher studies are necessary to elucidate the relationship between recruitment with different peak periods among sites and environment variables such as primary production, salinity, current and so on. |
