Effect of lunar phases in the size distribution of Holothuria scabra on intertidal areas in Sarangani Bay, Philippines

There have been few studies conducted on sea cucumbers, specifically Holothuria scabra, in Sarangani Bay, Philippines; and thus, there is little information to guide conservation and management efforts of these organisms in this area. A survey on the size distribution of H. scabra was carried out in three shallow intertidal areas by using the belt transect method during two lunar phases – full moon and new moon – for four months to evaluate this species’ intertidal population. The result shows a unimodal distribution of H. scabra, with specimens found during the new moon phase to be significantly larger than those found during the full moon phase. The sex ratio was estimated to be 1:1, consistent with most holothuroid studies, and not affected by the lunar phase. Population densities ranged from 0.17 individuals per square metre (ind. m-2) during full moon periods, to 0.34 ind. m-2 during new moon periods at three stations. The calculated allometric coefficient of 1.84 indicates that H. scabra are leaner for a given length in these areas than in other areas. The results also suggest that lunar phases have an effect on the size distribution of H. scabra, which probably explains the larger individuals collected by intertidal gleaners during new moon periods. evaluate the size distribution, sex ratio and density of H. scabra on selected intertidal areas in Sarangani Bay during two different lunar phases: full moon and new moon. Materials and methods Sarangani Bay is located in the southeast of Mindanao, Philippines between 5o33’25’’,and 6o6’15’’N and between 124o22’45’’ and 125o19’45’’E (Fig. 1). Three stations were selected in Sarangani Bay for the study. The stations were chosen based on reports of high abundance of sea cucumbers and the presence of intertidal gleaners. The first site is in Sitio Linao, Barangay Tinoto, Maasim, where the nearby Tausug community harvests sea cucumbers for subsistence; the second site is in Sitio S’nlang, Barangay Tinoto, Maasim, where harvesting is minimal; and the third site is in Sitio Macatimobol, Barangay Taluya, Glan, where sea cucumbers were harvested unsustainably. In every station, six belt transects (50-m long and 4-m wide) were established perpendicular to the shore at 10-m intervals. Investigators surveyed these transects at the lowest ebb tide during the full moon and new moon phases. In total, sampling took place over 24 nights between October 2014 and January 2015. Three investigators collected all H. scabra found within the 200 m2 transects. Sea cucumbers were put back into water to 1 Department of Marine Biology, College of Fisheries, Mindanao State University–General Santos, General Santos City, Philippines 9500 * Author for correspondence: pitogo.kiermitchel@gmail.com 49 SPC Beche-de-mer Information Bulletin #36 – March 2016 relax for five minutes. Then, total length – from mouth to anus – was measured to the nearest 0.5 cm with a tape measure. This operation was done quickly so that the sea cucumbers would not eviscerate. All of the measurements were recorded on pre-printed datasheets.