Allometric measurements of the giant clam (Tridacna gigas L.) to quantify deformities caused by stoking density

• Main Authors: Bacani, Christine Joy C., Pineda, Shaina M.
• Format: text
• Language: English
• Published: Animo Repository 1999
• Subjects: Giant clams > Growth; Giant clam culture; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/4485
• Institution: De La Salle University

Allometric measurements of the giant clam, Tridacna gigas were performed to quantify deformities caused by stocking density. Preliminary length, width, height, and weight measurements of seventy (70) juvenile clams were taken on April 15, 1998. Six weeks after, on May 28, 1998, clams were re-measured. The study was conducted off the island of Silaqui, Pangasinan in a giant clam nursery, operated by the University of the Philippines' Marine Science Institute (UPMSI). Standard linear regression analysis was used to relate clamshell measurements of length, width, height, and weight. Correlation coefficient (r) and coefficient of determination (r) were also computed to measure the strength of the straight-line relationship. The corresponding slopes were then analyzed. Slopes for length-width and length-height relationships of both deformed and normal clams showed negative allometric relationships (where slope is less than 1.) This implies that other variables increased at a relatively slower rate than shell length. Therefore, clam morphometry is elongated. Log transformations were also established. The results showed that in log length-log weight relationships for normal clams, weight is a cube of length. This means that the growth relationship is isometric. However, this is not the case for deformed clams, where length and weight proceed in different dimensions (slope is greater than or less than 3). Comparisons of average growth of variables showed that length, width, and height for deformed clams grow at a relatively equal pace. This indicates a rather box-like shell morphometry even if length measurements are relatively larger than width, height, or weight measurements. In normal clams, on the other hand, length has a much larger average growth rate than height. This indicates a rather elongated shell morphometry. Results showed that the slopes for both length-width (t= 0.817, p>0.05, df=65) and length height (t=0.489, p>0.05, df=65) relationships are not significantly different for normal and deformed clams. This indicates that both normal and deformed clams have similar growth patterns. But, once the clam is hindered by certain factors (i.e. flanked by two or more clams or outgrown its culture cage), growth patterns change. Unlike length-width and length-height relationships, slopes of log length-log weight were tested to be significantly different (t=5.045, p<0,05, df=65). This indicates that deformed clams are heavier than normal clams, suggesting thickening along the width of the shell.