Exceptional longevity, slow growth and late maturation infer high inherent vulnerability to exploitation for bass groper Polyprion americanus (Teleostei: Polyprionidae)

Abstract

The bass groper Polyprion americanus is a large demersal teleost (>1.5 m) thatinhabits deep continental and oceanic island slopes (50 to 1000 m). Currently, this species is considered Critically Endangered by the IUCN and there is a moratorium on its capture in Brazil.Fishing for this species is no longer commercially viable in Bermuda and they are fully protectedin South Africa. In most other locations, this species is rarely encountered and knowledge of itsbiology and catch history is limited. In the present study, specimens were collected from recreationaland commercial catches (n = 151) in the southeastern Indian Ocean from 2005 to 2012.Otolith edge analysis was used to verify that a single opaque zone was deposited annually fromMay to September. A maximum age of 78 yr for females and 55 yr for males was determined fromthin transverse sections of otoliths. The spawning period of this gonochorist was from autumn toearly winter (March to June) and partitioned prior to that of the sympatric congener P. oxygeneios(June to September). The lengths and ages at which 50% of females and males matured were 944and 808 mm total length, and 14.4 and 11.2 yr, respectively. The exceptional longevity, slowgrowth and late maturation of P. americanus imply a high inherent vulnerability at relatively lowlevels of exploitation. As such, the overexploitation of P. americanus in both Brazil and Bermudashould warrant close scrutiny in the waters off southwestern Australia, where exploitation ofdeepwater fisheries resources has increased.