Growth pattern and changes in abundance of the endangered bat star Asterina stellifera

Abstract

The sea star Asterina stellifera has declined during the last decade and is currently abundant only in the southern limit of its former range. We surveyed this population over 5 years to model individual growth and explore the relationship of changes in local abundance with variation in environmental factors and the reproductive status of individuals. Our results show that A. stellifera is a species with slow growth and a relatively long lifespan. Contrary to expectations for temperate species, growth rates were fairly constant through the year and therefore models including seasonal oscillations were inappropriate. The abundance of this species increased significantly from early spring to early summer, likely due to augmented activity and small‐scale aggregation during the reproductive season that affected our estimates of abundance. No significant recruitment occurred during the 5 years studied. The lack of recruitment during long periods and the slow individual growth rates make A. stellifera particularly vulnerable to local extinction. This study was performed prior to the arrival in the study area of the invasive kelp Undaria pinnatifida and side‐gilled sea slug Pleurobranchaea maculata, species that threaten the community structure where A. stellifera lives. Therefore, the information reported here will be essential to assessing the impacts of these exotic species on this sea star population.

Rate of natural mortality in the sea starArchaster angulatus(Echinodermata: Asteroidea)

“…In general species with a rapid growth rate and early maturity also exhibit higher mortality rate and shorter lifespan (Ebert, 1975) and A. angulatus appears to conform to this pattern. In terms of longevity, A. angulatus is similar to that estimated for Asterina stellifera (>5.5 years, Meretta et al ., 2016) but less than that estimated for Protoreaster nodosus (at least 17 years; Bos et al ., 2008). Nojima (1979) did measure mortality in A. latespinosus , however post-spawning morbidity of >99% of spawning adults was a significant feature of mortality rates in that species.…”

Locomotion and righting behavior of sea stars: a study case on the bat star Asterina stellifera (Asterinidae)

“…A timer kept the photoperiod at 12 h light:12 h dark. In all tanks, the individuals stayed on the observed field mean density (≈ 12 ind/m 2 ) (Meretta et al, 2016). Asteroids received a continuous food supply similar to those found in the natural environment (Farias, Meretta, & Cledón, 2012).…”

“…Large fragmented boulders of big rocks and vertical walls of orthoquartzite blocks characterize the sampling area (Genzano, Giberto, & Bremec, 2011). Therefore, studying this species' locomotion pattern is a first step in understanding its foraging strategy (Meretta, Rubilar, Cledón, & Ventura, 2014;Meretta, Farias, Cledón, & Ventura, 2016). Some basic questions related to sea stars locomotion arise.…”