Growth and reproduction of Megabalanus tintinnabulum (Crustacea: Cirripedia) in coastal waters of Pakistan, North Arabian Sea

Abstract

The growth and reproductive/ brooding pattern of Megabalanus tintinnabulum were studied from January 2012 to December 2013 on two rocky shores, Buleji and Manora, Karachi, the northern Arabian Sea. Population parameters were estimated using the von Bertalanffy growth function (VBGF) and ELEFAN 1 with the aid of FiSAT software. The population of M. tintinnabulum showed variability in density, size and growth rates between two rocky shores. The average density of M. tintinnabulum was higher at Buleji (101.9 ± 15.02 individual m−2) than Manora (76.0 ± 8.05 individual m−2). Though the estimated asymptomatic length (L∞) of M. tintinnabulum was 51.98 mm at both sites, the growth coefficient (K) value was higher at Manora (0.63 year−1) than Buleji (0.44 year−1). The population of M. tintinnabulum grew at a faster rate attaining the length of 31.8 mm in one year at Manora as compared to length of 23.7 mm at Buelji. Longevity (A0.95) in M. tintinnabulum was 4.8 years at Manora and 6.8 years at Buleji, while the longevity (A0.99) was higher at both sites being 7.3 years at Manora and 10.5 years at Buleji. The natural mortality rate (M) was 1.131 year−1 and 0.894 year−1 at Manora and Buleji, respectively. Though mature ovaries and testes were found throughout the year but the brooding individuals were observed during the winter (November to February) period showing that lower temperatures (20–24ºC) are preferred over higher temperatures (29–34ºC). The brooding capacity was same at two rocky shores but the numbers of brooders were higher at Manora than Buleji. The reproductive capacity was 7914 ± 303 of eggs per brood.