Density of the Porcelain Crab Petrolisthes teres Melin (Anomura: Porcellanidae) in the Intertidal Zone of Cocoy Beach, Tiniguiban, Puerto Princesa City, Palawan, Philippines

Abstract

The present study aimed to assess the monthly density of P. teres in intertidal pebble/cobble substrate. The study was conducted from June to November 2004. Density of porcelain crabs was assessed in six stations that were equally distributed over the intertidal area of Cocoy Beach, Puerto Princesa City. In each station two quadrats (0.25m3) were selected and sampled monthly. Environmental parameters such as water temperature, salinity, substrate temperature and rainfall were also assessed on a monthly basis.

The pebble substrate of Cocoy Beach constitutes an important habitat for P. teres. A total of 10,096 individuals were collected with monthly mean density of 369.7, 475.3, 557.7, 631.0, 661.0, 707.6 and 615.2ind./m2 in June, July, August, September, October and November, respectively, and an overall mean density of 559.4ind./m2. Density in June was significantly lower than the other months. It is assumed, that P. teres occurs in lower densities in summer compared to the rainy season. Among the stations the highest overall mean density (772.4ind./m2) was encountered in station IV, followed by stations V, III, II and I. Densities were significantly lower in stations I and II compared to the other stations. The significantly higher density of P. teres in stations III-VI in comparison to I and II is assumed to be related to the fact that station I and II are more disturb since they are within a passage for gleaners and boats. Differences in density among stations might also be substrate related.

Monthly water temperature and salinity were within the normal range for the geographic location and season. It is recommended to extend the study to include the dry season.