Growth and reproduction of the pelagic gobySufflogobius bibarbatusoff the Orange River, southern Africa

Abstract

Age, growth and reproduction of the pelagic goby Sufflogobius bibarbatus was investigated for males and females caught in demersal trawls between the Orange River and Port Nolloth on the west coast of southern Africa. Females had larger otoliths than males of similar body size, suggesting slower growth rates in females. S. bibarbatus is a large and long-lived gobiid, attaining 13cm at at least 6 years of age, with late maturation at 2-3 years of age. Males were larger than adult females of a similar age and matured at a larger size and greater age than females. Two batches of yolked oocytes were present in the ovaries and the maximum gonadosomatic index was 14.3%. Batch fecundity was significantly correlated with standard length (r 2 = 0.88) and ovaryfree body weight (r 2 = 0.92), and ranged from about 2 000 eggs in females 5.0-5.5cm long to about 10 000 in a female 9.8cm long. The mean fecundity was 842 ± 189 eggs per gramme of ovary-free body weight. The extended spawning season, from July to April, and the presence of more than one batch of yolked oocytes in the ovaries, suggest that the pelagic goby may be a serial batch spawner.

Dietary success of a ‘new’ key fish in an overfished ecosystem: evidence from fatty acid and stable isotope signatures

“…The sample sizes of each group used for both analyses are summarised in Table 2. While we acknowledge the circularity of the methods used to delimit size classes here, there is a clear relationship between age and length (Melo & Le Clus 2005) and there is a clear change in tracer signature over the continuous size gradient examined here.…”

“…Reproductive maturity is attained only at 2 to 3 yr of age, and although it is considered to be a serial batch spawner, overall fecundity is not high (Melo & Le Clus 2005). The species is discontinuously distributed between Southern Angola and the Eastern Cape (South Africa), with peaks in abundance mirroring the distribution of the diatomaceous mud belt off central Namibia (Staby & Krakstad 2006).…”

“…Crawford et al 1985), it is clear that gobies have not assumed the role of sardines or anchovy within the system. Despite relatively slow growth rates and late maturity, a comparatively long life-span (Melo & Le Clus 2005), and a high level of predation pressure, the regional biomass of Sufflogobius bibarbatus is increasing (Staby & Krakstad 2006). Although its adaptations to a physiologically stressful environment are remarkable (Utne-Palm et al 2010), its success within the altered ecosystem off Namibia must also reflect its flexible diet and an ability to use both the huge jellyfish biomass found there (Lynam et al 2006) and the benthos.…”

“…Sufflogobius bibarbatus is an unlikely 'winner' in the changed ecosystem off Namibia, as it is a relatively large, slow-growing gobiid that can attain 140 mm total length (TL) and an age of at least 6 yr (Melo & Le Clus 2005). Reproductive maturity is attained only at 2 to 3 yr of age, and although it is considered to be a serial batch spawner, overall fecundity is not high (Melo & Le Clus 2005).…”

“…These jellyfish have changed the transfer and flow of energy through the system, with most energy now thought to be channelled from jellyfish directly to the detrital food web (Heymans et al 2004). The scarcity of sardines has also resulted in an increased sedimentation of primary production (Bakun & Weeks 2006), which contributes to increased regional anoxia (Monteiro et al 2006).Sufflogobius bibarbatus is an unlikely 'winner' in the changed ecosystem off Namibia, as it is a relatively large, slow-growing gobiid that can attain 140 mm total length (TL) and an age of at least 6 yr (Melo & Le Clus 2005). Reproductive maturity is attained only at 2 to 3 yr of age, and although it is considered to be a serial batch spawner, overall fecundity is not high (Melo & Le Clus 2005).…”