MEPS 670:239-245 (2021)  -  DOI: https://doi.org/10.3354/meps13773

ABSTRACT: Due to demand for their unique and beautiful shells, chambered nautiluses are at risk of overharvesting throughout their ranges across the tropical Indo-Pacific region. In Palau, collection and harvest of the endemic Nautilus belauensis is minimal. To evaluate the N. belauensis population on Uchelbeluu reef near Koror, we compared population demographics and trap yields observed during surveys in 1982 with new surveys from 2015. Identical trap designs and protocols from 1982 were used on the same reef locations for the 2015 surveys. We captured 96 N. belauensis in 5 trap sets that soaked for 2 d in 2015, for an average catch-per-unit-effort (CPUE) of 9.6 Nautilus trap^-1 d^-1. N. belauensis CPUE showed no significant differences between 1982 (9.76 Nautilus trap^-1 d^-1) and 2015. Mature animals in 2015 comprised 86.4% of the total catch, of which 63.2% were males and 36.8% females with 1 animal of indeterminate sex. The overall sex ratio in 2015 was 1.71:1 and did not significantly differ from 1982 (1.87:1). There were no recaptures of marked animals in 2015, and no shells bore inscribed numbers from prior studies. While the lack of studies during the years between 1982 and 2015 preclude our ability to comment on the temporal stability of the N. belauensis population, the resemblance of the population demographics and trap yields over a 33 yr period suggests similar population characteristics during the survey years.

KEY WORDS: Nautilus belauensis · Palau · CPUE · Population · Sex ratio · Trap