Biology and fisheries of Namibian hakes (M. paradoxus and M. capensis)

Gordoa, Ana; Macpherson, Enrique; Olivar, M. Pilar; Scharm, Wolfgang

doi:10.1007/978-94-011-1300-7_3

Cited by 26 publications

(26 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Following independence, Namibia has taken full responsibility for managing the resources within its EEZ and management of the fisheries in both countries is under the assumption of national and discrete stocks for both species. However, while present knowledge indicates that Cape hake includes stocks largely confined within the respective national jurisdictions (Gordoa et al 1995;Payne and Punt 1995), the situation appears to be less clear for the deep water hake. The traditional view, as reflected in present management practices, is that DWH is not a shared stock.…”

Section: Introductionmentioning

confidence: 75%

Life cycle of hake and likely management implications

Strømme

Lipiński

Kainge³

2015

Rev Fish Biol Fisheries

View full text Add to dashboard Cite

Despite its economic and social importance for Namibia and South Africa, limited documented information exists regarding key aspects of the biology of deep-water hake, including its life cycle. This study utilizes data collected through the demersal surveys of the R/V Dr Fridtjof Nansen in South Africa and F/V Blue Sea 1 in Namibia to describe the migratory patterns of deep-water hake in space and time. Furthermore the study investigates aspects of the life cycle of this important species in the Benguela region. Results show that deep-water hake spawns between the western Agulhas Bank and Elands Bay in South Africa with the main nursery ground between Hondeklip Bay and the northern tip of Orange Banks. Deep-water hake in Namibia (up to the Kunene River) and along the south coast of South Africa (eastwards to Port Alfred) originate from these grounds, and undertake long-range migrations across latitudes and longitudes, respectively. This hypothesis is supported by the finding that spawning has not been observed in Namibia and there are no small juveniles along the South African south coast from the eastern border of the Agulhas Bank. The proposed pattern implies an interconnection between the Namibian and the South African components of the stock and the consequent need for a revision of the present management regime based on the assumption of stocks confined within the respective national jurisdictions. This study has used length frequency distributions in space and time in order to investigate the life cycle, in terms of origin, movement and population structure in particular, an approach that may also be useful for other widely distributed species.

show abstract

Section: Introductionmentioning

confidence: 75%

Life cycle of hake and likely management implications

Strømme

Lipiński

Kainge³

2015

Rev Fish Biol Fisheries

View full text Add to dashboard Cite

show abstract

“…The northern, upper slope assemblage (23 to 28OS, 300 to 500 m) encompasses areas where fishing pressure is high. Fishing (bottom trawl) activity was particularly intense north of 28" S latitude, mainly between 250 and 400 m (Gordoa et al 1995). In contrast, the assemblages located south of that latitude or inshore are subject to negligible levels of fishing pressure, because the bottoms are not conducive to trawling or are of little interest to commercial fisheries (Gordoa et al 1985) Fish samples were collected in the course of 6 stratified random bottom-trawl surveys carried out during 3 consecutive austral winters (1987/88/89) and summers (1988/89/90).…”

Section: Methodsmentioning

confidence: 99%

Biomass spectra in benthic fish assemblages in the Benguela System

Macpherson¹,

Gordoa²

1996

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

ABSTRACT. B~ornass spectra in the different benthic fish assemblages at depths between 100 and 800 m off the coast of Namibia were studied over a p e r~o d of 3 yr These assemblages were located in areas spanning active upwelling centres on the shelf and zones of lower productiv~ty on the lower slope. The slopes of the curves for the normallzed size distributions were related to zonal productivity and abundance of the smallest slze classes. In the main upwelling centre, in which abundance of small specimens was h~g h e r and comrnunlty diversity lower, biomass clearly dropped off with increasing size; teleost fishes and m~d-level predators (which prey on euphausiids and other pelagic crustaceans) predominated In the less productive zone, where the biomass of small specimens was very low and communlty divers~ty very h~g h , biornass increased or at least tended to remaln constant with size and elasrnobranchs and apex predators (which prey on fish and cephalopods) were most abundant.

show abstract

“…Small gobies are more common closer to the coast than larger fish (O'Toole 1978) and likely move offshore with increasing age and size, as do many other demersal species within the region (e.g. Gordoa et al 1995). Interestingly, both species of jellyfish are found throughout the water column but reach highest densities near the surface , which suggests either that large gobies scavenge moribund jellyfish on the seafloor (as e.g.…”

Section: Ontogenetic Shift In Goby Dietmentioning

confidence: 99%

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

Bank¹,

Utne‐Palm²,

Pittman³

et al. 2011

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

The bearded goby Sufflogobius bibarbatus has become a key component of the pelagic food web off Namibia following the crash in pelagic fish populations during the 1970s, and its biomass is increasing despite significant predation pressure and apparent life-history constraints. The integrated feeding of the bearded goby was studied from samples collected during April 2008, using stable isotope ratios (δ 13 C, δ 15 N, δ 34 S) and fatty acids, to resolve conflict amongst previous dietary studies based on gut-content analysis and to understand how diet could influence its success within the region. Isotopes of carbon and nitrogen suggest that the now abundant jellyfish could contribute up to 74% of the diet, and δ 34S signatures indicate that the diatom-and bacteria-rich sulphidic sediments on the central shelf may contribute around 15% to the diet. Fatty acid analyses provided support for sulphur bacterial and jellyfish-feeding amongst gobies, and further suggest that small gobies fed more on zooplankton while large gobies fed more on sedimented diatoms. Both data sets suggest that ontogenetic changes in diet were linked to changes in habitat: pelagic when small, more demersal when large. The study highlights the value of using multiple tracers in trophic studies and indicates that the dietary flexibility of the bearded goby, in conjunction with its behaviour and physiology, likely contributes to its success within the northern Benguela ecosystem.KEY WORDS: Benthic-pelagic coupling · Keystone species · Disturbed ecosystem · Feeding · Aequorea forskalea · Chrysaora fulgida Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 428: [219][220][221][222][223][224][225][226][227][228][229][230][231][232][233] 2011 fish Chrysaora fulgida (Reynaud, 1830) and Aequorea forskalea (Forskål, 1775) (Bakun & Weeks 2006, Lynam et al. 2006. 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). 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). Juvenile gobies generally occur inshore of the 200 m isobath, while larger individuals are more common offshore (O'Toole 1978). Although S. ...

show abstract

Biology and fisheries of Namibian hakes (M. paradoxus and M. capensis)

Cited by 26 publications

References 31 publications

Life cycle of hake and likely management implications

Life cycle of hake and likely management implications

Biomass spectra in benthic fish assemblages in the Benguela System

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

Contact Info

Product

Resources

About