A review of the conservation status and survey methods for the live-bearing sea star Parvulastra vivipara

Abstract

The live-bearing sea star Parvulastra vivipara, 1 of only 6 Asteroidea species globally that gives birth to live young, had an uncertain conservation status due to data deficiencies and historical differences in research methods. Restricted to southeast Tasmania, its distinctive reproductive strategy, coupled with limited distribution, low genetic diversity, and geographically isolated populations makes P. vivipara populations highly susceptible to localised and global extinction. Since the species was described in 1969, ten different historical survey methods have been used to survey P. vivipara populations. Notably, the survey area at these locations has increased through time as P. vivipara abundances declined. In 2022, surveys revealed the persistence of P. vivipara populations at 10 of 15 historically documented locations. Five locations experienced local extinction of P. vivipara populations, 3 in the last 2 decades, and 4 locations had <150 individuals remaining. P. vivipara density has experienced a decline of 90% from the first surveys in 1974-2001 to recent surveys in 2022. Based on the current trajectory, it is predicted that the density of P. vivipara will decline to 1 ind. m-2 by 2033 and 1 ind. site-1 by 2111, with some locations experiencing this decline even sooner. The rapid decline and restricted area of occupancy mean that P. vivipara qualifies for Critically Endangered status under IUCN Red List criteria A1 and B1. There is a pressing need for standardised and ongoing monitoring, management of key threats, and recovery strategies to bolster local and global P. vivipara populations against the threat of extinction.