Abstract: An investigation was made on the amphioxus (Branchiostoma belcheri) and its habitat environment in Naozhou Island area from March to December 2006, aimed to provide information on the amphioxus conservation in South China Sea. It was found that B. belcher mainly distributed in the narrow range around 20°55.35′N and 110°31.5′E, and covered an area of 4.08 km². Its average resource density was 209 ind·m^-2, with a maximum of 1 053 ind·m^-2, and its average biomass was 40.8 g·m^-2, with a maximum of 424 g·m^-2. Its body length had an obvious seasonal fluctuation, and its spawning season was from March to July. The larva thrived in autumn and winter. There existed great differences in gonad maturity and sex ratio in different seasons and growth stages, with maximum sex maturity ratio up to 51% in spring. The body length at 50% maturity was 54 mm, and the sex ratio in the 30-55 mm length cohort was 1∶1. Females outnumbered males when the body length was above 55 mm. The equation for amphioxus body masslength relationship was W=00014 L^3.2898. When the body length reached 60 mm, the reducing coefficient of amphioxus population was 0.361 cm^-1.

Key words: Thousand-Island Lake, Landscape fragmentation, Biodiversity, Tree, Shrub