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MEPS prepress abstract   -  DOI:

Nautilus belauensis population demographics and trap yields in Palau were similar between surveys in 1982 and 2015

Bruce Carlson*, M. Awai, W. B. Saunders, Erik C. Franklin

*Corresponding author:

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 two days in 2015, for an average catch-per-unit-effort (CPUE) of 9.6 Nautilus per trap per day. Nautilus belauensis catch per unit effort showed no significant differences between 1982 (9.76 Nautilus per trap per day) 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% 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 to 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-year period suggests similar population characteristics during the survey years.