habitat_narrative
Marine
Rhabdosargus globiceps adults inhabit shallow reefs to 50 m in the summer and are found on reefs and unconsolidated sediments down to 120 m depth on the Agulhas Bank in the winter (Griffiths et al. 2002). Juveniles are common in estuaries and bays, including the surf-zone, seagrass beds and coastal lagoons (Talbot 1955; Lasiak 1981; Wallace et al. 1984; Bennett 1989; Whitfield and Kok 1992; Lamberth et al. 1994, 1995; Clark 1997; Griffiths et al. 2002; Heemstra and Heemstra 2004). A subpopulation of R. globiceps occurs in Langebaan Lagoon, Saldanha Bay and frequents tidal channels with sandy bottoms <10 m depth (Arendse 2011). Adults disperse offshore in winter and concentrate inshore at depths < 60m in response to oceanographic patterns in summer (Griffiths et al. 2002). Acoustic telemetry work has shown that this is a relatively mobile species (Attwood et al. 2007, Kerwath et al. 2008). Fish migrate across the bay, spending June to August in Saldanha Bay and the remainder in Langebaan Lagoon where they exhibit a degree of site fidelity but also undertake diel commuting behaviour (Attwood et al. 2007, Kerwath et al. 2008). This species primarily feeds on crustaceans and molluscs. Larger individuals are able to crush clams, gastropods, and mussels (Griffiths et al. 2002, Heemstra and Heemstra 2004). Juvenile R. globiceps feed on small crustaceans including amphipods, isopods, ostracods and filamentous algae (Griffiths et al. 2002, Heemstra and Heemstra 2004). The maximum recorded age for this species is 21 years. The maximum length recorded is 47.2 cm FL, and the maximum recorded weight is 3.6 kg (V. Taylor pers. comm.).Reproduction
Rhabdosargus globiceps is a rudimentary hermaphrodite that spawns in summer from September to March throughout its range (Griffiths et al. 2002). The age at 50% maturity is 1.5 to 3.2 years for males and two or more years for females (Griffiths et al. 2002, Attwood et al. 2010). Length at 50% maturity ranges from 15.3 cm FL to 23.6 cm FL for males and 22.2 cm FL for females (Griffiths et al. 2002, Attwood et al. 2010).
Generation length for R. globiceps is estimated to be nine years, using the following equation for a gonochoristic fish species: Generation length = Σxlxmx/Σlxmx
