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Walvis Ridge Namibia

Walvis Ridge Namibia is a proposed EBSA that lies contiguous to the Walvis Ridge EBSA in the high seas. Walvis Ridge itself is a unique and significant seamount chain in the high seas that forms a bridge between Africa and the Mid-Atlantic Ridge in the Atlantic Ocean. Walvis Ridge Namibia EBSA encompasses the globally rare connection of a hotspot track (seamount chain formed by submarine volcanism) to continental flood basalt. There is high upwelling-driven productivity in the area. Habitat heterogeneity is a result of the complex benthic topography, supporting likely high biological diversity including vulnerable sessile macrofauna, demersal fish and foraging threatened seabirds. Despite some fishing pressure, the EBSA is currently in good ecological condition.

EBSA Description: Walvis Ridge

General Information


The Walvis Ridge EBSA spans a significant hotspot track (seamount chain formed by submarine volcanism) that comprises the aseismic Walvis Ridge and the Guyot Province. This feature forms a submarine ridge running north-east to south-west from the Namibian continental margin to Tristan da Cunha and Gough Islands at the southern Mid-Atlantic Ridge. It is a unique geomorphological feature likely to be of special importance to vulnerable sessile macrofauna and demersal fish associated with seamounts. Given the complex habitat heterogeneity (comprising steep slopes, canyons, embayments formed by massive submarine slides, trough-like structures, a graben, abyssal plains, and shallow summits of seamounts and guyots), it is likely that the area supports a relatively higher biological diversity. This has been confirmed by research cruises that have sampled a variety of benthic macrofauna, including fragile species such as corals, and have also recorded a high diversity of globally threatened seabirds. Although bottom fisheries occur on the Walvis Ridge, the spatial extent of commercial fishing is limited to a relatively small area.

MARISMA updates

The site description has been updated, and changes to the EBSA delineation have been proposed. With support from the BCC, other member state EBSA working groups, and MARISMA, the Namibian EBSA Task Team are discussion options for implementing site-specific managament in key areas of this EBSA with SEAFO and the STRONG High Seas Project.

Introduction of the area

The aseismic Walvis Ridge is a seamount chain formed by hotspot submarine volcanism, some of which are guyots, that is connected to a continental flood basalt province. The Ridge presents a barrier between North Atlantic Deep Water to the north and Antarctic Bottom Water to the south. The surface oceanographic regime is the South Atlantic Subtropical Gyre bounded by the productive waters of the Benguela Current System and the Subtropical Convergence Zone. The feature described here is depth-bound around the 4000‑m isobath, and contains significant areas within the likely vertical extent of near-surface zooplankton migration (1000 m). The area supports a high diversity of seabirds, some of which are endemic to the Tristan Group in the southwest. Although biologically significant, data from research cruises are patchy and variable. However, the area contains several named seamounts, recognized and endorsed by the General Bathymetric Chart of the Oceans (GEBCO) that likely support enhanced primary production, abundance and species richness (e.g., Dobrovol’sky, Ewing, Filippov, Valdivia Bank, Wüst, Radostnaya, Schedraya, Smejnaya and Zubov). 

Description of location

The Walvis Ridge extends obliquely (NE-SW) from the northern Namibian shelf (18°S) to the Tristan da Cunha island group at the Mid-Atlantic Ridge (38°S). Although the focus area is predominantly located outside of national jurisdiction, it does extend into the Namibian exclusive economic zone. The EBSA boundary links tightly to important benthic features comprising the Walvis Ridge (produced by combining GEBCO data with that from www.bluehabitats.org: see Harris et al., 2014, and data from Holness et al., 2014). Those features that are continuous with the Ridge, as well as isolated hills that are in close proximity are included. The component within Namibia’s jurisdiction includes areas with a high selection frequency in the regional spatial prioritization to meet biodiversity targets efficiently, as well as key features that form part of the Ridge. Given the global rarity of the connection between the hotspot track and the continental flood basalt province, it is imperative that the full extent of this feature is encompassed within the EBSA.


Area details

Feature description of the area

The Walvis Ridge is both a benthic and water column feature: it is a chain of seamounts that individually and collectively constitute an ecologically and biologically significant deep-sea feature, as also recognized by the Census of Marine Life project (CenSeam: http://censeam.niwa.co.nz). The Walvis Ridge also includes a number of deep-sea features in addition to the seamounts and guyots, such as steep canyons, embayments formed by massive submarine slides, trough-like structures, a graben, abyssal plains, and a fossilized cold-water coral reef mound community (GEOMAR 2014). Based on these physical features, the focus area can be divided into three sections (GEOMAR 2014). The northern section extends SW from the Namibian shelf, with a steep NW scarp, ridge-type seamounts, and guyots with rift arms. The central section comprises a SW narrow and a NE broader section, with the former incised by two trough-like features, and the latter including Valdivia Bank and a prominent graben of 200 km x 20 km. Finally, the southern section bifurcates into two NE-SW-trending ridge-like extensions each about 450 km long, one heading towards Tristan da Cunha and the other towards Gough, with a seamount chain lying approximately parallel between the ridges (GEOMAR 2014).

The high habitat heterogeneity supports moderately diverse biological communities, including benthic macrofauna such as brachiopods, sponges, octocorals, deep-water hexacorals, gastropods, bivalves, polychaetes, bryozoans, cirriped crustaceans, basket stars, ascidians, isopods and amphipods (GEOMAR 2014). Altogether, 970 species have been recorded in this EBSA, including several threatened species (OBIS 2017). Productivity seems to increase from SW to NE along Walvis Ridge, with sediment organic carbon and the abundance and diversity of phytoplankton communities increasing towards the Namibian shelf, likely reflecting patterns of nutrient transport and upwelling in the north-flowing Benguela Current that are more intense closer to the African continent (GEOMAR 2014).

Research has been carried out several times at the Walvis Ridge during various oceanographic cruises. These include: Russian Federation cruises; Spanish-Namibian surveys (see summary of knowledge in Perez et al., 2012); US Walvis Ridge cruise MV1203 Expedition (March 2012; http://earthref.oth/ERESE/Projects/mv1203) and the GEOMAR cruise SO233 WALVIS II (GEOMAR, 2014). These cruises have collected both physical and biological data/samples.

Feature conditions and future outlook of the proposed area

The Walvis Ridge EBSA is primarily recognized as a geological feature but the biota in the area could be vulnerable to fishing (e.g., orange roughy, alfonsino, southern boarfish, deep-water crabs, fragile sessile benthic megafauna; SEAFO report in FAO Statistical Area 47 and a portion of 34). The fisheries beyond national jurisdiction are managed by SEAFO, which has introduced area management, catch quotas, and a suite of bottom-fishing regulations. Fisheries within the Namibian EEZ, however, are managed by Namibia’s Ministry of Fisheries and Marine Resources. Concentrations of ferromanganese nodules on the deepest adjacent areas (adjacent Cape Abyssal Plain; Perez et al., 2012) have been observed, thus in future, seabed mining may also be a consideration and would be subject to management by the International Seabed Authority. Oil exploration has already taken place within the EBSA, namely Welwitschia-1 well, which was drilled in 2014 at 20°11’9.79”S, 11°19’3.27”E. Although it was found to be dry, future drilling activities in the general area, including inside the extended EBSA, are likely. The Namibian sections of the EBSA are largely in good condition, though some impacted areas exist on the far eastern edge (Holness et al., 2014). No evidence exists to suggest that the high seas portion of the EBSA is impacted to any large degree, it is therefore reasonable to assume that it is also in good condition. 


Assessment of the area against CBD EBSA criteria

 Uniqueness or rarity

Rank: High

As the only extensive seamount chain off of the Mid-Atlantic Ridge in the Southeast Atlantic, the Walvis Ridge is a unique geomorphological feature. It is also one of the few hotspot tracks on earth that connects to continental flood basalt.  

 Special importance for life-history stages of species


Rank: High

Seamount chains may facilitate connectivity between individual seamounts over extensive distances. The varied topography and geomorphology support demersal fish resources (based on demersal fisheries records in locations shallower than 2000 m). The varied bathymetry dictates the distribution area and provides significant habitat for bentho-pelagic species (e.g., hotspots for orange roughy), and is also likely to do so for epi-pelagics (Clark et al., 2007, Rogers and Gianni, 2010). These seamounts are significant habitats for cold-water corals and sponges (Zibrowius and Gili, 1990; GEOMAR 2014). Thus, the Walvis Ridge is of special importance for sessile macrofauna and for demersal fish associated with seamounts (FAO FIRMS species distribution maps) (http://firms.fao.org). The feature is also an important post-breeding area for Spectacled Petrel (Procellaria conspicillata), an Atlantic Ocean endemic species breeding only on an island within the Tristan group and recorded as foraging along the Walvis Ridge (Reid et al., 2014). It includes parts of the foraging areas for globally threatened seabirds, such as the Tristan Albatross (Diomedea dabbenena), Wandering Albatross (Diomedea exulans) and Atlantic Yellow-nosed Albatross (www.seabirdtracking.org). The series of seamounts provides a potential stepping stone feature for organisms from coast to mid ocean (e.g., dispersion of the benthic octopod, Scaeurgus unicirrhus; Sanchez and Alvarez, 1988).

 Importance for threatened, endangered or declining species and/or habitats


Rank: Medium

Bluefin and big-eye tuna occur in the area (e.g., FishBase), and orange roughy hotspots within the area are known (SEAFO information). The far south EEZ of Tristan da Cunha is a foraging area for albatross, penguins, shearwaters and petrels (www.seabirdtracking.org). Historic whale capture data in the mid-ocean portion of the feature indicate former concentrations of Right and Sperm Whales (maps derived from OBIS: www.iobis.org), and an opportunistic survey within the area in 2009 as part of the South Atlantic MAR-ECO project recorded 23 sightings of cetaceans (Perez et al., 2012). Critically Endangered leatherbacks nesting in South Africa also pass over Walvis Ridge during their post-nesting migrations to the feeding grounds near St Helena Island (Harris et al., 2017).

 Vulnerability, fragility, sensitivity, or slow recovery


Rank:  High

Habitat-forming sessile megafauna are fragile and vulnerable to bottom contact fishing gears and slow to recover from damage. Habitat prediction models and observational data (Durán Muñoz et al., 2012, GEOMAR 2014, Perez et al., 2012) indicate presence of cold-water corals and sponges, and other delicate fauna such as basket and feather stars (see also the OBIS database for species records: http://www.iobis.org/explore/#/area/351). Based on empirical evidence (e.g., observations from Spanish/Namibian cruises on the Valdivia Bank, and along the whole ridge; GEOMAR 2014) the seamounts and deep-sea features along the Walvis Ridge have sensitive habitats, biotopes and species, justifying high criterion ranking. 

 Biological productivity


Rank: Medium

Productivity appears to increase from SW to NE along the Walvis Ridge, as seen in the sediment organic carbon load and abundance, and diversity of phytoplankton that both increase closer to the Namibian shelf (GEOMAR 2014).  Several seamounts also extend into the photic zone and may have enhanced primary production. Significant areas are within the likely vertical range of epipelagic zooplankton migration (Jacobs and Bett, 2010).


 Biological diversity


Rank: Medium

Data on biological diversity are limited, however there are some data on seabirds, fish, and benthic mega-, macro- and meiofauna (see Perez et al., 2012 for a review, and GEOMAR 2014), including 17 922 records of 907 species listed on OBIS (OBIS 2017). The south-west end of the feature has high seabird diversity, including Spectacled Petrel, Atlantic Yellow-nosed Albatross, Sooty Albatross and Atlantic Petrel. Foraging range extrapolations and satellite tracking work have highlighted the south-west part of the feature as important for the following seabird species (status on IUCN Red List 2017-1 is given for all): Tristan Albatross (Diomedea dabbenena) - Critically Endangered; Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) – Endangered; Sooty Albatross (Phoebetria fusca) – Endangered; Atlantic Petrel (Pterodroma inerta) – Endangered; Grey-headed Albatross (Thalassarche chrysostoma) – Endangered; Northern Royal Albatross (Diomedea sanfordi) – Endangered; Wandering Albatross (Diomedea exulans) – Vulnerable; Grey Petrel (Procellaria cinerea) – Near Threatened; Black-browed Albatross (Thalassarche melanophrys) – Near Threatened; Cory’s Shearwater – Least Concern; Great Shearwater (Puffinus gravis) – Least Concern; Southern Giant-Petrel (Macronectes giganteus) – Least Concern. Observations and the range of habitats created by the seamount chain and immediately adjacent abyssal area suggest comparatively higher diversity of ecosystems, habitats, communities, and species. This has been confirmed to some extent through bathymetric/geological surveys and biological sampling of the benthos, which revealed a variety of benthic macrofauna (GEOMAR 2014).




Rank: High

Human influence is largely historic, fisheries were and are mainly confined to seamount summits (SEAFO information, Clark et al., 2007, and relevant papers cited in Perez et al., 2012), and oil exploration drilling has been limited to date. Whaling has ceased in this area for several decades. Apart from seamounts that are likely to have been impacted by bottom-fishing, the remainder of the area is considered to have a high degree of naturalness. No evidence exists to suggest that the high seas portion of the EBSA is impacted to any large degree, it is therefore reasonable to assume that it is in good condition. The Namibian sections of the EBSA are largely in good condition, though some impacted areas exist on the far eastern edge (Holness et al., 2014). 



BirdLife International. 2009. Designing networks of marine protected areas: exploring the linkages between Important Bird Areas and ecologically or biologically significant marine areas. Cambridge, UK: BirdLife International. www.cbd.int/doc/meetings/mar/ewbcsima- 01/other/ewbcsima-01-birdlife-02-en.pdf.

BirdLife International. 2010. Marine Important Bird Areas toolkit: standardised techniques for identifying priority sites for the conservation of seabirds at-sea. BirdLife International, Cambridge UK. Version 1.1: May 2010. www.birdlife.org/eu/pdfs/Marine_IBA_Toolkit_2010.pdf.

Census of Marine Life project CenSeam http://censeam.niwa.co.nz, http://seamounts.sdsc.edu.

Clark, M.R., Vinichenko, V.I., Gordon, J.D.M, Beck-Bulat, G.Z., Kukharev, N.N., Kakora, A.F. 2007. Large scale distant water trawl fisheries on seamounts. Pp. 361-412 in Seamounts: Ecology, Fisheries and Conservation. Fish and Aquatic Resources Series 12, T.J. Pitcher, T. Morato, P.J.B. Hart, M.R. Clark, N. Haggan and R.S. Santos, eds, Blackwell Publishing, Oxford.

Durán Muñoz, P., Sayago-Gil, M., Murillo, F.J., Del Río, J.L., López-Abellán, L.J., Sacau, M., Serralde, R. 2012. Actions taken by fishing nations towards identification and protection of vulnerable marine ecosystems in the high seas: The Spanish case (Atlantic Ocean). Marine Policy, 36: 536–543.

FAO FIRMS (Fishery Resources Monitoring System) firms.fao.org.

GEBCO (General Bathymetric Chart of the Oceans) Available at http://www.gebco.net/data_and_poducts/gridded_bathymetry_data/.

GEOMAR, 2014. RV SONNE Fahrtbericht / Cruise Report SO233 WALVIS II: Cape Town, South Africa - Walvis Bay, Namibia: 14.05-21.06.2014. Hoernle, K., Werner, R., Lüter, C (eds). Helmholtz-Zentrum für Ozeanforschung Kiel, Germany: Nr. 22 (N. Ser.), 153 pp.

Harris, L.R., Nel, R., Oosthuizen, H., Meyer, M., Kotze, D., Anders, D., McCue, S., Bachoo, S. 2017. Managing conflicts between economic activities and threatened migratory marine species towards creating a multi-objective blue economy. Conservation Biology, in press.

Harris, P.T., Macmillan-Lawler, M., Rupp, J., Baker, E.K. 2014. Geomorphology of the oceans. Marine Geology, 352: 4-24.

Holness, S., Kirkman, S., Samaai, T., Wolf, T., Sink, K., Majiedt, P., Nsiangango, S., Kainge, P., Kilongo, K., Kathena, J., Harris, L., Lagabrielle, E., Kirchner, C., Chalmers, R., Lombard, M. 2014. Spatial Biodiversity Assessment and Spatial Management, including Marine Protected Areas. Final report for the Benguela Current Commission project BEH 09-01.

Jacobs, C.L., Bett, B.J. 2010. Preparation of a bathymetric map and GIS of the South Atlantic Ocean: a review of available biologically relevant South Atlantic Seamount data for the SEAFO Scientific Committee. National Oceanographic Centre Southampton, Research and consultancy Report No. 71 (unpublished manuscript).

OBIS. 2017. Summary statistics of biodiversity records in the Walvis Ridge EBSA. (Available: Ocean Biogeographic Information System. Intergovernmental Oceanographic Commission of UNESCO. www.iobis.org. Accessed: 2017-07-27).

Perez, J.A.A, dos Santos Alves, E., Clark, M.R., Bergstad, O.A., Gebruk, A., Azevedo Cardoso, I., Rogacheva, A. 2012. Patterns of life on the southern Mid-Atlantic Ridge: Compiling what is known and addressing future research. Oceanography, 25: 16-31.

Reid, T., Ronconi, R., Cuthbert, R., Ryan, P.G. 2014. The summer foraging ranges of adult spectacled petrels Procellaria conspicillata. Antarctic Science, 26: 23-32.

Rogers, A.D., Gianni, M. 2010. The implementation of UNGA Resolutions 61/105 and 64/72 in the Management of Deep-Sea Fisheries on the High Seas. Report prepared for the Deep Sea Conservation Coalition, International Programme on the State of the Ocean, London UK. 97 pp.

Sanchez, P., Alvarez, J.A. 1988. Scaeurgus unicirrhus (Orbigny, 1840) (Cephalopoda Octopodidae): First record from the South-east Atlantic. South African Journal of Marine Science, 7: 69-74.

Zibrowius, H., Gili, J.M. 1990. Deep-water Scleractinia (Cnidaria Anthozoa) from Namibia, South Africa and Walvis Ridge, southeastern Atlantic. Scientia Marina, 54: 19-46.

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EBSA criteria met at a high (red), medium (orange) or low (yellow) rank. 


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