Sex Ratio Variation of the Omani Indian Oil Sardine <i>Sardinella longiceps</i> (Valenciennes, 1847)

Abstract

During the period 2004–2008, a total of 1590 (1022 females and 568 males) Omani Indian oil sardines ( Sardinella longiceps ) were randomly sampled from a landing site in Al-Seeb, Sultanate of Oman, to determine sex ratio. The results were compared with the results of a previous sampling study conducted in 1997–1998 in the same area, in which 1799 sardines (905 females and 560 males) were sampled. During the period 2004–2008, the total length of female sardines ranged from 12.8 to 22 cm with a mean of 16.7 ± 1.72 cm and their total weight ranged from 16.8 to 94.6 g with a mean of 43.65 ± 0.46 g. Male sardines ranged from 12.3 to 21.5 cm in length with a mean of 16.42 ± 1.8 cm and their weights range d from 16.32 to 79.8 g with a mean of 41.34 ± 0.57 g. During 1997–1998, female sardines ranged from 10 to 21.3 cm in length with a mean of 16.19 ± 2.16 cm and their weights ranged from 8.21 to 91.0 g with a mean of 38.33 ± 0.52 g. The male sardines ranged from 12 to 20.6 cm in length with a mean of 16.7 ± 1.8 cm and their weights ranged from 16.32 to 79.8 g with a mean of 41.34 ± 0.57 g. The monthly sex ratios fluctuated between 0.45 and 1 with a mean of 0.63 ± 0.04 in 1997–1998 samples and between 0.29 and 0.98 with a mean of 0.68 ± 0.02 in 2004–2008 samples. The overall sex ratios during 1997–1998 and 2004–2008 were 0.62 and 0.64, respectively. Both the sex ratios were different from the expected sex ratio of 0.5 according to the c 2 test (P-value < 0.01). The relationship between sex ratio and length was explained by the power function as (sex ratio=0.002 L 2.03 , r = 0.92) for the period 1997–1998 and by (sex ratio=6.7×10 -6 L 6.84 , r = 0.96) for 2004–2008.