The dynamics of intertidal populations of the starfish Asterias rubens, living in contrasted habitats and over a broad geographical range, were studied from March 2000 to November 2002 using modal analysis. As only 1 juvenile (first year after recruitment) and 1 adult (subsequent years) modes could be distinguished; only juvenile growth was quantified. Concomitantly, experiments were carried out to test several factors assumed to influence juvenile growth: food quantity and quality, emersion, salinity variations and temperature. Three different juvenile growth patterns were evidenced: (1) a fast and protracted growth linked to high food availability and lack of disturbance; (2) a winter cessation of growth likely due to a seasonal increase of emersion-related stress and salinity variations; and (3) disrupted juvenile dynamics, which was encountered in 2 populations. In the first one, estuarine salinity conditions limited growth and, combined with food depletion, led to the extinction of the population. In the second one, wave action confined most of the population to a restricted area with low food levels. In the third scenario, intraspecific competition for food was probably at the source of an unusual growth pattern in which most juveniles did not grow while a small proportion achieved a medium growth rate.

Certain starfish have a restricted autotomy region at the base of each arm, at which the whole arm is detached if damaged or trapped. These species are common prey items of gulls, which have been observed to break-up starfish by gripping one arm and shaking the whole animal. This raises the possibility that shaking invokes the autotomy response, thereby accelerating consumption of prey and reducing the opportunity for prey to be stolen. To evaluate the role of autotomy in this interaction, specimens of Asterias rubens were shaken manually and the timing and pattern of breakage recorded. It was found that arm detachment was usually mediated by autotomy, although this depended on the way in which animals were shaken, and that autotomy did not effect detachment more rapidly than breakage outwith the autotomy region.

Three specimens of Atlantic starfish, Asterias rubens are here reported as the first record from the Black Sea. After being first reported from the Bosphorus Strait in 1996, this alien starfish has invaded the Sea of Marmara and is now extending its range of distribution to the Black Sea.