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Browns Bank

Browns Bank is on the western continental margin of South Africa. It includes the only patch of a unique gravel habitat (which is Critically Endangered), reef-building cold-water corals, and untrawled hard grounds on the shelf and shelf edge. This EBSA is an important spawning area for demersal and pelagic fish species, and is part of a critical area for retention of spawning products. The spawning area is also linked to nursery grounds on the inshore area of the west coast and the Agulhas Bank. The Agulhas and Southern Benguela ecoregions meet at the south-eastern boundary of the EBSA, and sporadic shelf-edge upwelling enhances the productivity along its outer margin. This EBSA also overlaps substantially with two proposed marine Important Bird Areas.

EBSA Description: Browns Bank

General Information

Summary

Browns Bank includes benthic and pelagic habitats of the outer shelf and shelf edge along the western continental margin of South Africa. The area includes a unique gravel habitat, reef-building cold-water corals and untrawled hard grounds. It is an important fish spawning area for demersal and pelagic species. The spawning area is linked to nursery grounds on the inshore area of the west coast and the Agulhas Bank and has better retention than that of areas further north. The Agulhas and Southern Benguela ecoregions meet at the south-eastern boundary of the area and sporadic shelf edge upwelling enhances the productivity along the outer margin. The area is important for threatened habitats and species, including a Critically Endangered benthic habitat type and overlapping substantially with two proposed marine Important Bird Areas, namely for Cory’s Shearwater and Atlantic Yellow-nosed Albatross. The area was also identified as a priority area through two systematic biodiversity plans, meeting targets for habitat representation, vulnerable marine ecosystems and hake spawning. 

MARISMA updates

The site description has been updated; changes to the delineation are being discussed. 

Introduction of the area

The area is along the outer shelf and shelf edge of the western continental margin of South Africa. It includes benthic and pelagic habitats with unconsolidated sand and gravel habitats and a pelagic habitat type that is characterised by elevated productivity and frequent fronts due to shelf-edge upwelling (Lutjeharms et al., 2000, Lagabrielle 2009). The area ranges from approximately 150 m – 800 m and the Agulhas and Southern Benguela ecoregions meet at the its south-eastern edge (Sink et al., 2012), with sporadic shelf-edge upwelling that enhances the productivity along its outer margin (Lagabrielle et al., 2009). The area includes the western Agulhas Bank spawning ground, and is part of a critical area for retention of spawning products (Hutchings et al., 2002). It was identified as a priority area through a national plan to identify areas for offshore protection (Sink et al., 2011) and by a systematic biodiversity plan for the South African west coast (Majiedt et al., 2013).

Description of location

Browns Bank includes benthic and pelagic habitats of the outer shelf and shelf edge along the western continental margin of South Africa. This area is off the southwest coast of South Africa and is completely within national jurisdiction.

 

Area details

Feature description of the area

The Browns Bank area includes unconsolidated sand and gravel habitats, and hard ground habitats that are poorly known (Sink et al., 2012b). The pelagic habitat is characterised by elevated productivity and frequent fronts due to shelf edge upwelling (Lutjeharms et al., 2000, Lagabrielle 2009). The biodiversity at Browns Bank includes benthic macrofaunal communities characterized by high abundances of brittle stars and many species of polychaetes (Karenyi, unpublished data); cold-water corals have also been collected within the area. Further, it is a proposed marine Important Bird Area (IBA) for two species of seabirds, Cory’s Shearwater and Atlantic Yellow-nosed Albatross (BirdLife International 2013), indicating that it holds a significant proportion of the global population of these species during some periods of each year for which data are available. Browns Bank is also part of the western Agulhas Bank spawning ground as described by Hutchings et al., (2002). This area has been included in annual demersal fish trawl surveys conducted by the Department of Agriculture, Forestry and Fisheries.

Feature conditions and future outlook of the proposed area

According to Wilkinson (2009) there are three areas of untrawled hard grounds on the shelf edge within this area, suggesting they are still intact. However, Sink et al., (2012a,b) indicate that the outer shelf gravel habitat is in poor condition and there is no remaining area of this habitat type left in good or fair condition.

 

Assessment of the area against CBD EBSA criteria

 Uniqueness or rarity

 

Rank: High

Browns Bank was identified by two systematic plans as a priority area because it is the only place where targets for the Southern Benguela Gravel Outer Shelf habitat (which is Critically Endangered) can be met (Majiedt et al., 2013, Sink et al., 2011). It should be noted that this habitat type has a limited extent with an estimated total area of less than 450 km2.

 

 Special importance for life-history stages of species

 

Rank: High

This area is part of the western Agulhas Bank spawning ground as described by Hutchings et al., (2002). The gadoid Cape hakes Merluccius capensis and M. paradoxus, the gempylid Thyrsites atun (snoek) and the clupeid Etremeus whiteheadii (round herring) move to the western Agulhas Bank and southern west coast to spawn, generally in late winter and early spring when offshore Ekman losses are at a minimum. The eggs and larvae drift northwards and inshore to the west coast nursery grounds. Browns Bank, an apex area of the Agulhas Bank, is recognized as a critical area for retention of spawning products because eddies in this area help to re-circulate water inshore and link important nursery areas with this spawning habitat on the shelf edge. Strong jet currents on the west coast oblige adult hake to shift southwards to spawn, to ensure that juveniles enter the west coast nursery grounds downstream (Hutchings et al., 2002). The area is also important for juvenile spiny lobsters (Santos et al., 2014). This shelf-edge area also constitutes foraging area for offshore seabirds (BirdLife International 2013). Limited tracking datasets have shown that the shelf edge is heavily used by a diversity of pelagic seabirds. In particular, the Browns Bank site is a proposed marine IBA for two species of seabirds; Cory’s Shearwater and Atlantic Yellow-nosed Albatross (BirdLife International 2013). Additional seabird tracking datasets may result in this site being an IBA for additional species in future.

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

 

Rank: High

The Atlantic Yellow-nosed Albatross is globally Endangered, and Browns Bank is a proposed marine IBA site for this species, indicating that it holds a significant proportion of the global population of this species during some periods of each year for which data are available (BirdLife International 2013). This area also contains the only patch of Southern Benguela Outer Shelf Gravel, a habitat type that is considered Critically Endangered (Sink et al., 2012a,b). The pelagic habitat within this area is considered Vulnerable and is the most threatened of South Africa’s 16 pelagic habitat types (Sink et al., 2012a).

 Vulnerability, fragility, sensitivity, or slow recovery

 

Rank:  Medium

This area has hard ground habitats on the outer shelf and shelf edge that are considered sensitive to demersal trawling and mining (Sink et al., 2011, 2012a, 2012bb). Recently, fisheries observers collected two species of cold water corals within this area (Capricorn Fisheries Monitoring, unpublished information). The specimens are in the invertebrate collection at iZiko, the South African Museum in Cape Town.

 Biological productivity

 

Rank: Medium

The Agulhas and Southern Benguela ecoregions meet at the southeastern boundary of the area and sporadic shelf edge upwelling enhances the productivity along its outer margin. Based on tracking data, the area holds a significant proportion of the global population of at least two species of seabirds, namely Cory’s Shearwater and the globally Endangered Atlantic Yellow-nosed Albatross (BirdLife International 2013).

 

 Biological diversity

 

Rank: Low

The national habitat map indicates a moderate number of habitat types within the area (Sink et al., 2012 a).

 

 Naturalness

 

Rank: Medium

There are three areas of untrawled hard grounds on the shelf edge within this area (Wilkinson 2009). The outer shelf gravel habitat is in poor condition and there is no remaining area of this habitat type left in good or fair condition (Sink et al., 2012a,b).

 

References

BirdLife International. 2013. Marine e-Atlas: Delivering site networks for seabird conservation. Proposed IBA site ‘Atlantic, Southeast 19 – Marine’. Available online: http://54.247.127.44/marineIBAs/default.html. Accessed 11 March 2013

Hutchings L, Beckley LE, Griffiths MH, Roberts MJ, Sundby S, van der Lingen C. 2002. Spawning on the edge: spawning grounds and nursery areas around the southern African coastline. Marine and Freshwater Research 53: 307-318.

Lagabrielle E. 2009. Preliminary report: National Pelagic Bioregionalisation of South Africa. Cape Town: South African National Biodiversity Institute.

Lutjeharms JRE, Cooper J, Roberts M. 2000. Upwelling at the inshore edge of the Agulhas Current. Continental Shelf Research, 20(7): 737 – 761.

Majiedt P, Holness S, Sink K, Oosthuizen A, Chadwick P. 2013. Systematic Marine Biodiversity Plan for the West Coast of South Africa. South African National Biodiversity Institute, Cape Town.

Santos, J., Rouillard, D., Groeneveld, J.C. 2014. Advection-diffusion models of spiny lobster Palinurus gilchristi migrations for use in spatial fisheries management. Marine Ecology Progress Series, 498: 227–241.

Sink KJ, Attwood CG, Lombard AT, Grantham H, Leslie R, Samaai T, Kerwath S, Majiedt P, Fairweather T, Hutchings L, van der Lingen C, Atkinson LJ, Wilkinson S, Holness S, Wolf T. 2011. Spatial planning to identify focus areas for offshore biodiversity protection in South Africa. Unpublished Report. Cape Town: South African National Biodiversity Institute.

Sink K, Holness S, Harris L, Majiedt P, Atkinson L, Robinson T, Kirkman S, Hutchings L, Leslie R, Lamberth S, Kerwath S, von der Heyden S, Lombard A, Attwood C, Branch G, Fairweather T, Taljaard S, Weerts S, Cowley P, Awad A, Halpern B, Grantham H, Wolf T. 2012a. National Biodiversity Assessment 2011: Technical Report. Volume 4: Marine and Coastal Component. South African National Biodiversity Institute, Pretoria.

Sink KJ, Wilkinson S, Atkinson LJ, Sims PF, Leslie RW, Attwood CG. 2012b. The potential impacts of South Africa’s demersal hake trawl fishery on benthic habitats: historical perspectives, spatial analyses, current review and potential management actions. Unpublished report. Cape Town: South African National Biodiversity Institute.

Wilkinson S. 2009. Ring Fencing the Trawl Grounds. South African Deep-sea Trawling Industry Association. Report prepared by Capricorn Fisheries Monitoring cc. Cape Town.

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BrownsBank

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

 

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