Distribution of seagrasses, substratum types and epibenthic macrobiota in Torres Strait, with notes on pearl oyster abundance

Abstract

The benthic habitat of Torres Strait was surveyed in May-June 1989, using almost 600 transects (each 4 × 500 m) randomly dispersed over an area of about 25 000 km². The distribution and relative abundance of seagrasses were estimated visually and mapped, along with the distributions of substratum types and epibenthic macrobiota; pearl oyster abundance was also estimated. Seagrasses were seen in most transects and, though very patchy at small scales, tended to increase from almost zero abundance in the southern and eastern areas of the survey to moderately dense in north-western Torres Strait. The epibenthic macrobiota and the substratum type also varied greatly, with the greatest diversity and abundance of biota associated with the harder substrata. The survey area supported an estimated 1.2-2.5 million pearl oysters, and though their density varied significantly with habitat type, the latter accounted for only about 12% of the variance.