A classification strategy for mapping trochus shell habitat in Torres Strait, Australia

Abstract

Trochus niloticus is a large, marine gastropod that is harvested from the coral reefs of Torres Strait, to the north of Australia. Prime habitat for the large, commercial sized trochus is restricted to narrow zones of coral rubble and pavement on the windward edges of reefs. These areas are difficult to map and survey for trochus shell. Initial research demonstrated that Landsat TM imagery could be used to produce an accurate map of trochus habitat for a single reef. A methodology was then developed to transfer a classification mask, generated from this intensively surveyed reef to others in Bourke Group of islands. The procedure returned results that were within 2% to 12% (underestimates) of areal estimates based on fieldwork and air photo interpretation This methodology offers potential as an accurate and cost effective way of monitoring habitat across the remote environments occupied by trochus.