Non-destructive video image analysis method for measuring growth in sponge farming: Preliminary results from the New Zealand bath-sponge Spongia (Heterofibria) manipulatus

Abstract

The skeleton of the New Zealand endemic sponge Spongia (Heterofibria) manipulatus (Demospongiae: Dictyoceratida: Spongiidae) has physical qualities that make it suitable for use as a bath-sponge. The species is particularly abundant around exposed coastlines of D'Urville Island in the Marlborough Sounds and on the east coasts of Northland and Coromandel Peninsula. Growth rates and changes in the shape of explants of S. (H.) manipulatus were monitored for a period of 12 months on a pilot marine farm near D'Urville Island, using digital video image analysis. This nondestructive method proved to be an accurate means of monitoring sponges for changes in size when compared with repeated wet-weighing ex situ. Sponge explants increased in size by an average of 28.5% from September 2000 to June 2001, after which growth varied markedly to September 2001, with most of the explants changing little or shrinking in size. Implications of the biological and physical characteristics of S. (H.) manipulatus, for the future commercial production of this species, are discussed. © 2003, Copyright Taylor & Francis Group, LLC.