Abstract
Hippopus porcellanus is a rare and heavily exploited giant clam species with limited distribution range in the Indo-West Pacific Region. Overharvesting has resulted in the localized extinction of H. porcellanus in the Philippines, but its populations appeared to have recovered in Tubbataha Reefs Natural Park (TRNP) after more than 20 years of protection. As one of the least studied giant clam species, the shell dimension-live weight relationships were determined. In addition, the growth parameters of H. porcellanus in TRNP were monitored with the mark-recapture method. All three shell dimensions of H. porcellanus were good estimators of live weight. The von Bertallanfy growth parameters K (0.29) and Lâ (29.24 cm) were determined on the basis of 80 marked individuals recaptured twice within 2.5 years. Nearly 90% of marked clams survived at the end of the study. Studies on aspects of biology of other giant clams species at the park is suggested.
Highlights
Giant clams (Cardiidae: Tridacninae), with only 11 extant species (Othman et al, 2010; Su et al, 2014) worldwide, are the largest living bivalves that for centuries have been utilized as food and their shells as ornaments
In 1993, only empty shells of H. porcellanus, H. hippopus and Tridacna derasa were encountered by Estacion et al (1993) in Tubbataha Reefs Natural Park (TRNP)
The relationships between the different shell dimensions and live weight of H. porcellanus were best expressed by the equation W = aLb, where W stands for live weight and L for any of the three shell dimensions
Summary
Giant clams (Cardiidae: Tridacninae), with only 11 extant species (Othman et al, 2010; Su et al, 2014) worldwide, are the largest living bivalves that for centuries have been utilized as food and their shells as ornaments. Excessive harvesting of these clams for external trade has led to local extinctions of several species in the Philippines, Micronesia, Singapore and Indonesia (see Tan and Zulfigar, 2003; Gomez and Mingoa-Licuanan, 2006; Othman et al, 2010; Neo and Todd, 2013). Hippopus porcellanus and the newly discovered three giant clam species Tridacna costata, Tridacna rosewateri and Tridacna teveroa have the most restricted geographical ranges (Othman et al, 2010), making them more vulnerable to harvesting. Calumpong and Cadiz (1993) found a few individuals of H. porcellanus, suggesting that the species is rarely present or has been overexploited in the reefs of Tubbataha
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