17 SPC Beche-de-mer Information Bulletin #34 – May 2014 An assessment of holothurian diversity, abundance and distribution in the shallow lagoons of Mauritius Katrin Lampe-Ramdoo 1 , Ruby Moothien Pillay 2 and Chantal Conand 3 Abstract The sea cucumber industry, which is known to be particularly vulnerable to overexploitation and collapse, has been under tremendous pressure in Mauritius since the mid-2000s. Consequently, in 2010, the Ministry of Fisheries imposed a two-year ban on the collection of sea cucumbers, which was later extended for another four years (2012–2016) to avoid the collapse of the fishery. This study collected data on the diversity and abundance of sea cucumbers in the shallow lagoons of Mauritius in order to assist with the sustainable management of the fishery. Previous surveys conducted in 2011 in the lagoons of the south and west coasts of the island revealed the presence of 17 holothurian species. The present study visited some of the earlier study sites as well as some new ones in the north and east coasts to assess sea cucumber abundance and diversity. From March to June 2013, 115 daytime transects at 23 sites (totally 92,000 m² in area) revealed a total of 7,488 holothurians, of which 76% were of commercial importance. The holothurians were distributed within a range of habitats with no significant correlation detected between abundance and habitat types. Holothurian distribution in the shallow lagoons of Mauritius seems to be influenced by physical, biological and anthropogenic factors. The present survey revealed that some species could be recovering from exploitation. Introduction The lagoons of Mauritius are impacted by climatic changes and various anthropogenic factors, all of which cause a reduction in habitats for marine organisms and a potential loss of biodiversity (Moothien Pillay et al. 2012). Moreover, the overexploitation of commercially important species is threatening the persistence of the most demanded and high-priced species. The sea cucumber industry, which is vulnerable to overexploitation and collapse, has been under tremendous pressure in Mauritius since the mid-2000s. Surveys carried out in 2010 by the Ministry of Fisheries revealed a decrease in abundance, species diversity and size of sea cucumbers at the surveyed sites when compared with data collected in 2007–2008 (AFRC 2012). As a consequence, a two-year moratorium was imposed on the fishery, and later extended to 2016, to reverse the rapid decline of sea cucumber populations. Because little is known about the ecology of sea cucumbers and the extent of their exploitation in Mauritius, this study was undertaken at a larger scale to assist the Ministry of Fisheries with the sustainable management of this fishery. This study builds on the baseline study that was carried out in 1 University of Applied Sciences, Bremen, Neustadtswall 30, 28199 Bremen, Germany (lampe-katrin@gmx.de) 2 Mauritius Oceanography Institute, France Centre, Victoria Avenue, Quatre-Bornes, Mauritius (rubykm@moi.intnet.mu) 3 Laboratoire d’Écologie Marine, Université de La Réunion, P.O. Box 7151, 97715, Saint-Denis, Île de La Réunion and MNHN Paris (conand@univ-reunion.fr) 2011 on the abundance, diversity and distribution of holothurian species inhabiting the western and southern shallow lagoons of Mauritius (Lampe 2013). For a more comprehensive understanding of the population dynamics of sea cucumbers around the island, besides the western and southern coasts, the northern and eastern regions were also studied. This was undertaken in light of the history and recent development of the sea cucumber fishery in Mauritius, including non-commercial species. Materials and methods Site description Mauritius is a small island state of volcanic origin located in the western Indian Ocean, approximately 900 km east of Madagascar (Saddul 1995). The island forms part of the Mascarene Archipelago with La Reunion, Rodrigues, St. Brandon and a few other smaller islands. The coastline is surrounded by a fringing reef and includes a lagoon that extends from the near shore to the reef flat and is composed of different zones that are further subdivided, depending on the size of the lagoon, into shore reef, mid-lagoon, back-reef, reef flat and fore reef (Baird et al. 2003).