Barnacles are generally found to be attached on the hard substrata and are abundantly found in the intertidal zones. Acorn barnacles (Chthamalus malayensis) are found abundantly in upper littoral zones and have ability to tolerate strong waves action, high temperature and desiccation Shell  of Chthamalus malayensis is elongated, egg-shaped and is greyish-white. In Pakistan, C. malayensis are abundant in different intertidal zone of Sindh and Balochistan coast including at  Sandspits and Hawksbay which has abundant population of this barnacle on their rocky shores. A comparative study of bioecological characteristics of Chthamalus malayensis from Sandspit and Hawksbay beaches was made during which  the distribution of Chthamalus malayensis at these beaches was study and compared.  The population density of Chthamalus malayensis at Kakka Pir Sandspit and Hawksbay show higher during the month of November and January due to distinct intertidal zonation and some distinctive environmental factors .The Chthemalus malayensis samples that were collected from Hawksbay shore, displayed highest variation within weight and length over the year as compared to Sandspit.

KEY WORDS

Barnacles, Chthamalus malayensis, rocky shore, intertidal zone, Karachi. Sandspit, Hawksbay, bioecology