The den ecology and the effects of fishing pressure on the distribution of Octopus cyanea (Octopodidae: Mollusca) in Rodrigues lagoon, Rodrigues, Mauritius

Abstract

ABSTRACT Octopus cyanea is a species of particular economic importance for coastal regions in the tropical Indo-Pacific, including the Mauritian island of Rodrigues. At present, little is known about their habitat preferences and how this may impact on their abundance from fishing pressure. This study aimed to investigate how the abundance of this octopus and their potential den sites differed between three areas of Rodrigues lagoon, Mauritius which were subjected to differing levels of fishing pressure and in which other marine species competed for the same space. A series of surveys over two months was conducted to measure octopus numbers, counted holes and abundance of selected invertebrates in 1000 m2 belt transects, In total, 503 holes were counted that would be suitable for octopuses, and 17 octopuses were observed within the holes. A highly fished lagoon area, contained the most potential den holes. The other organisms found in the counted holes were fish, including eels, urchins and holothurians. I attribute the seemingly low abundance of octopus compared to previous surveys overall to the time of year and the lack of suitable habitat within these areas. Octopus abundance throughout the lagoon is low despite it being within a Marine Protected Area and does not follow the expected patterns of abundance when subjected to differing levels of fishing pressure, that is, it was expected that more would be found in the best protected area. Application of improved knowledge of octopus biology and habitat preferences could provide better management plans for their protection.