Observations on Growth Rates and Maturity in an Introduced Population of the Roman Snail (Helix pomatia Linnaeus, 1758) at a Semi-Natural Site with no Natural Population

Helix pomatia Linnaeus, 1758, the Roman snail, is widely exploited for food in Europe. Over-exploitation has led to protective measures laid down in the European Union Habitats Directive (European Community Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (92/43/EEC). In Poland, the implementation of this directive has involved passive protection by means of closed seasons for collecting, minimum size limits and annual rotation of areas in which collecting is permitted (Dyduch-Falniowska et al., 2001). The size limit (minimum shell diameter of 30 mm) has not changed for several decades. Helix pomatia has relatively slow reproductive and maturation rates (Ligaszewski et al., 2014). Efforts have been made to improve these under controlled conditions (Jeppensen, 1976; Gomot, 1990; Chmielewski, 2005). In experiments at the National Research Institute of Animal Production in Balice, Poland, mature H. pomatia taken from the wild and kept in greenhouses reproduced successfully, producing large numbers of hatchlings both in autumn and after the winter hibernation (Ligaszewski et al., 2007). While rearing snails in such conditions over the whole of their life cycle (eggs to harvested adults) is expensive, the release of juveniles into apparently suitable habitats might increase the number of natural populations and serve to secure the snail’s future in the face of exploitation. This study thus set out to determine the fate of juveniles reared in greenhouses and released into a semi-natural, synanthropic site in which the snail was absent. A target area was modified to provide good starting conditions, and the growth rate and dispersal of the introduced juveniles studied over the period 2011–2015. In particular, the study aimed to MALACOLOGIA, 2016, 59(2): 341−346