Growth rates of the giant clam Tridacna maxima (Röding, 1798) reared in cages in the Egyptian Red Sea

Abstract

The giant clam, Tridacna maxima were reared in cages in the sea; measurements of the shell's length, height, width and buoyant weight were taken under water to compare the growth rates of different size groups of T. maxima. The results showed that the specific growth rates were significantly high in the smallest size group and decreased with increasing clam size (P < 0.01). The highest specific growth rate was 0.35% day−1 for size group 50–70 mm length with 0.09% day−1 for size group 150–170 mm length. Shell growth rates varied by size group (P < 0.01). There was a general decreasing trend in the shell growth rate with increasing shell size. The average shell growth rate for all size groups along the period of the study was 2.1 ± 1.12, 1.8 ± 0.47 and 1.5 ± 0.56 mm month−1. Morphometric analysis showed that T. maxima shell weight exhibited positive allometric growth with “b” values of 3.28 and 3.11 for shell length and shell height respectively and negative allometric growth with “b” values of 2.35 for shell width. The correlation between shell sizes (length, height and width) and weight was high and positive (R = 0.95, 0.91 and 0.94 respectively). The Von Bertalanffy growth parameters were K = 0.26 year−1, L∞ = 244 mm.