The potential efficacy and application of freshwater and hypersaline immersion to control the spread of a marine invasive species

Abstract

Introduced into New Zealand waters in 2008, the polychaete worm Sabella spallanzanii (Gmelin, 1791) is a marine invasive species with potential for significant ecological and economic impact. Within New Zealand, efforts to cope with this pest have focused on containment as efficacious control methods are in their infancy. To remedy this, we tested the efficacy of hyper-saline (50‰) and hypo-saline (0‰) baths as a potential control method for this species. Specimens of S. spallanzanii were collected from within the Auckland region and exposed to salinity treatments for up to 1440 min (24 h) and mortality rates were compared using LT50 i.e. number of minutes taken for 50% of worms to die. Specimens subjected to hypo-saline conditions resulted in an LT50 of 31.0 min compared to 132.0 min for hyper-saline conditions. Accordingly, hypo-saline dips have potential as an environmentally safe and cost-effective management method for maintenance of recreational vessels and other marine structures (e.g. aquaculture gear and shellfish stocks) that are heavily fouled with S. spallanzanii.