Life history and population characteristics of the Antarctic starfish, Anasterias antarctica Luetken, 1856 (Asteroidea: Forcipulatida: Asteriidae) around the Falkland Islands

The biology of littoral fauna of the Falkland Islands is largely unknown. This pilot study was launched by Shallow Marine Surveys Group and was aimed at investigating life history of the Antarctic starfish, Anasterias antarctica, a dominating invertebrate predator of intertidal and subtidal, including its distribution, seasonal and ontogenetic migrations, spawning seasonality, fecundity, growth, and feeding habits. A total of 3,426 starfish were sampled in different habitats around the Falkland Islands at low tide using SCUBA diving. Sampling included measuring arm length, presence/absence of brooding and feeding; the prey was identified to the lowest taxa and measured if condition permitted. In a total of 48 broods, eggs were counted and embryonic stage assigned. This medium-sized species attains an arm length of 96 mm (85.4 g). The size increased with depth and starfish carry out seasonal bathymetric migrations with smaller animals (<30 mm) being rare in waters >10 m depth in winter. Egg laying occurs between March and July, and juvenile dispersal—mostly in October–November. Fecundity (52–363 eggs) and egg/offspring size increase with maternal size. Juvenile starfish are of ca. 2 mm arm length and grow to 9–11 mm in 1 year. Feeding intensity is at a maximum before and after the reproductive period. Females might occasionally resume feeding when they are still brooding a small number of juveniles. The starfish prey upon isopods (Sphaeromatidae), molluscs Pareuthria spp. and variety of gastropods, bivalves chitons, barnacles, and also scavenges. Prey size increases with starfish size.