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Click here to go back Details of this species in Port Elizabeth Status: Alien Invasiveness: Invasive Occurrence: Established Source: Branch and Stephanni 2004 Arrival Date: Introduction: Intentional, legally Species Notes for this Location: M. galloprovincialis was independently introduced to Port Elizabeth on the South Coast by mariculture trials. Three years after the introduction, M. galloprovincialis had spread along a total of 223 km of coastline from the initial point of introduction, although numbers further away were very low. Management Notes for this Location: Location Notes: Impacts: Competition: Relative to the three native species, Mytilus galloprovincialis grows faster in absolute terms under optimal conditions, and its growth is proportionally less diminished by exposure to air (Van Erkom Schurink and Griffiths 1993, in Branch and Stephanni 2004). Its annual reproductive output expressed as a percentage of its body mass, exceeds 120% as it reproduces more than once each year; its total annual output is between 20% and 200% greater than that of any of the indigenous species (Van Erkom Schurink and Griffiths 1991, in Branch and Stephanni 2004). This high reproductive output translates into an exceptionally high rate of recruitment, with densities of up to 20,000 recruits per 100cm2 being recorded on the west coast (Harris et al., 1998, in Branch and Stephanni 2004). M. galloprovincialis is also more tolerant of exposure to air than any of the indigenous species. Survivorship of M. galloprovincialis (measured over 24 months at midtide levels where the mussels experienced about 50% exposure to air) is more than double that of any of the other species. Confirmation of the relative tolerance of the four species to aerial exposure was provided by experiments in which mussels were held for 42 weeks at the high-tide level where they experienced up to 7 days of continuous exposure to air. Under these conditions, survivorship of M. galloprovincialis was 92%, but 78% for Perna perna, 37–46% for Choromytilus meridionalis and 0–10% for Aulacomya ater (Hockey and van Erkom Schurink 1992, in Branch and Stephanni 2004). Last Modified: 9/05/2006 9:35:11 a.m.