Preliminary observations of the feeding periodicity and selectivity of the introduced seastar, Asterias amurensis (Ltitken), in Tasmania, Australia

Abstract

Field observations of the introduced north Pacific seastar, Asterias amurensis, in Tasmania showed that it feeds over the 24-h period with no obvious cycle ofactivity. Percentage ofseastars feeding at anytime ranged from 17.2% at 1600 h to 58.2% at2000 h. Feeding periodicity did not correlate with the time ofday or the height ofthe tide. A significantly higher proportion ofjuveniles than adult seastars were found to be feeding at any given time. A comparison ofprey items found in the stomachs with the availability ofprey items in sediments revealed that, in the field, A. amurensis selected some prey species and avoided others. A total of 15 species were consumed, with molluscan prey the most important (> 60%) in winter and spring and at the two depths studied (2 m and 5 m). It is concluded thatA. amurensis is an opportunistic generalist predator but shows a certain degree ofspecialisation in local populations. All bivalves at the field site were found to be juveniles (most < 5 mm shell length) . Whether this is a natural phenomenon or due to the presence ofA. amurensis cannot be ascertained, as there are no data from these sites prior to the introduction ofthis seastar. Due to the dominance ofjuveniles, the resilience of the bivalve community is likely to be low.