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Offsetting the impact of the marine ornamental trade: a case study of two temperate top shells (Osilinus lineatus and Gibbula umbilicalis) as potential clean-up crew

Authors


G. J. Watson, Institute of Marine Sciences, School of Biological Sciences, University of Portsmouth, Ferry Road, Portsmouth, PO4 9LY, UK. E-mail: gordon.watson@port.ac.uk

Abstract

  1. It is estimated that several million tropical gastropods are exported each year for the marine ornamental trade to become part of a clean-up crew (those species that have a beneficial function such as controlling nuisance algae) in an aquarium. Collecting non-tropical species could offset exploitation impacts, reduce shipping costs and increase survival rates due to shorter transport distances. However, these species must be able to survive and function at tropical marine tank temperatures (25 °C).
  2. Two species of intertidal temperate top shell (Osilinus lineatus) and (Gibbula umbilicalis) were acclimated to 25 °C, 27 °C and 29 °C and survivorship compared with ambient (UK summer) conditions for 55 days. Virtually all G. umbilicalis died during the experiment in all elevated temperatures. In contrast, O. lineatus had minimal mortality in all treatments except the 29 °C, which reached 46.7% ±3.3 by day 55.
  3. Locomotor activity and position in relation to the air/water interface were assessed at 25 °C and ambient conditions. All individuals from both species were active and the mean activity score did not differ between treatments. The majority (63–85%) of the individuals of both species also spent their time either submerged or at the air–water interface and those held at 25 °C spent less time on average out of the water.
  4. Nitrocellulose plates impregnated with an algal extract were used to assess grazing of both species at 25 °C compared with ambient temperature. Over 24 h both consumed significant quantities, and no differences in levels were observed between temperatures or species.
  5. Together this evidence shows that O. lineatus survives equally well at standard tropical aquarium temperatures and also continues to function as a clean-up crew. Collection of this and other non-tropical species may be an important alternative conservation approach to tropical collection if ethical and management issues are addressed.

Copyright © 2012 John Wiley & Sons, Ltd.

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