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The Saba Bank

The Saba Bank, a 2000 km² shallow bank (average depth 20 m) immediately south-east of the island of Saba

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Articles about the Saba Bank:

	Management Plan for the Saba Bank. S. Lundvall. 2007. (pdf 1.2 MB)
	Report on the Saba Bank Fisheries, 2007. W. Toller (pdf 440 KB)
	Report on habitat surveys on the Saba Bank. W. Toller. 2007 (pdf 2.9 MB)
	Report on ROV observations on the Saba Bank. W. Toller et al. 2007 (pdf 570 KB)
	Fish records from the Saba Bank commercial fishery. W. Toller. 2007 (pdf 775 KB)
	Report on 2007 Gorgonian survey. P. Etnoyer (pdf 170 KB)
	Preliminary report of the Saba Bank RAP expedition 2006., S. McKenna (pdf 300 KB)
	First report on the fisheries of the Saba Bank in 2000. F. Dilrosun (pdf 650 KB)
	1996 review of Saba Bank. E. Meesters et al. (pdf 740 KB)

GENERAL DESCRIPTION OF THE SABA BANK

LOCATION AND SITUATION
GEOLOGY AND GEOMORPHOLOGY
MARINE HABITATS, FLORA AND FAUNA, AND NATURAL RESOURCES
HUMAN USE
CRITICAL THREATS

View of Saba from the Saba Bank

INTRODUCTION

Reports of decreasing fish stocks, destructive fishing activities of foreign vessels, anchoring of oil tankers and tank cleaning, have raised concerns about the environmental state of the Bank. Meesters et al, (1996) [download full report, pdf 720KB], commissioned by the Environmental Department of the Netherlands Antilles reviewed the Saba Bank in 1996 in combination with a short study on location. He concluded that the habitat of the Saba Bank is particularly important for several reasons:

• The significance of the sea-current patterns suggest that the reefs are potentially an important source of fish and shellfish larval dispersal to the islands of Saba, St Maarten and to the islands in the eastern Greater Antilles and the Virgin islands,
• The coral reefs of the Saba Bank are relatively remote from intense human impact and may not only provide important scientific information on the status of reefs in relatively unspoiled condition, but are also a reserve of biodiversity for the region,
• The reefs of the Saba Bank are potentially a resource for dive-tourism and an essential resource for fishing.

Meesters’s study also recommended that a management plan should be developed in order to preserve this unique marine habitat. The National Policy paper “Contours of Environmental & Nature Conservation Policy for the Netherlands Antilles” incorporated this recommendation, and again in the National Nature Policy Plan of 2000 the development of a management plan for the Saba Bank is stated as an important objective. As a first step to realize such a management plan, the department of Environment of the Netherlands Antilles (MINA) initiated a comprehensive fishery catch assessment survey in 1999-2000 (Dilrosun, 2000. Pdf 850 KB), in order to get an impression of the fisheries resources of the Saba Bank, and produced a video to create awareness of the underwater world and introduce the idea of management. In 2006, together with Conservation International a Rapid Assessment Program of the Saba Bank was undertaken, which confirmed the uniqueness of the Bank.

INTEGRATED MANAGEMENT PLAN

In order to sustainably use the bank's resources and integrate different forms of usage, while at the same time protecting its unique biodiversity, an integrated management plan for the whole bank is necessary. In 2007 MINA concluded a project for a more complete biodiversity survey of the bank. The results of this study, in combination with the earlier fishery assessment data, form the basis for an integrated management plan. The full management plan can be downloaded through the link provided above. Below is the description of the Saba Bank based on the survey and the previous work on the Saba Bank.

LOCATION

The Saba Bank (17^o25' N, 63^o30' W) is an undersea elevation with a flattened top, a bank, 4 km southwest of the island of Saba and 25 km west of St. Eustatius (Figure 1). It is raised about 1000m above the general depths of the surrounding sea floor and its shape is approximately rectangular, the long axis trending ENE-WSW. With a length of 60 to 65 km and a width of 30 to 40 km, the total surface area is 1800 km² (measured to the 50 m isobath).The platform is somewhat tilted with the northwestern part of the surface being deeper than the southeastern part. The largest part of the Bank is between 20 and 50 m depth, but a substantial eastern part (approximately 225 km²) is between 13 and 20 m depth. On its western rim depths are around 50 m, while on the eastern and southeastern edges, where a prominent ridge system (55 km long) runs along the platform, depths vary between 11 and 15 m.

The legislative authority of the island of Saba does not extend beyond the territorial sea. Beyond the territorial sea jurisdiction lies with the Central Government of the Netherlands Antilles. Approximately 20% of the Saba Bank lies within the Saban territorial waters, with the remaining 80% falling within the limits of the Exclusive Fisheries Zone, soon to become Exclusive Economic Zone (EEZ). Management of both the 12 nautical miles zone and the EEZ (once it has been officially established) can be mandated to the island territory of Saba by the Central Government under the National Maritime Ordinance.

Oceanography

The Saba Bank and the neighbouring islands are affected by The Antilles Current and possibly the Caribbean current. The Antilles Current was named in 1876, and flows northward east of the Antilles joining the Florida Current past the outer Bahamas. Its waters are concentrated into a strong northward jet about 80-100 km wide centred at 400 m depth. Mooring studies have indicated that the Antilles has mean transport speeds of 3.2 Sv northwards in the upper 800m of water (see Figure 3).

Click to enlarge. The Antilles Current transports tropical waters from the North Equatorial Current northwestward. It is a signi-ficant source of warm water for the Gulf Stream system. (source: http://oceancurrents.rsmas.miami.edu/)	Click to enlarge. The Caribbean current is formed by waters flowing though the Antilles Island chain from the Atlantic into the Caribbean sea. (source: http://oceancurrents.rsmas.miami.edu/ )

The narrowly spaced chain of islands, Banks, and sills of the Antilles Islands Arc, including Saba and the neighbouring islands, separate the Caribbean from the Atlantic Ocean and act as a sieve for the inflow of Atlantic water to the Caribbean Basin. Water flows into the Caribbean Sea through the narrow passages between the islands and continues westward as the Caribbean Current, the main surface circulation in the Caribbean Sea (Figure 4).

Waves, known as ground swells, are produced by low pressure weather systems at sea.
Waves produced by the wind are generally highest from June to July and from December to March when the wind speeds are highest. The dominant easterly wind drives waves towards the west. During swell wave conditions there is likely considerable impact on the communities on the Bank.

Ecoregion

Based on oceanographic, biogeographical, and larval connectivity data various marine ecoregions have been identified in the world. Within the Caribbean, or Tropical Northwestern Atlantic Province, the Saba Bank is part of the Eastern Caribbean Ecoregion, which extends from Grenada to the Virgin Islands. Within this ecoregion the Saba Bank is assumed to be an important source of larvae of various marine organisms for the northern parts of this region, especially the Virgin Islands. Depending on the length of larval stages this influence from the Saba Bank can extend much further for some organisms. Research on the connectivity of lobsters and conch of the Saba Bank needs to be undertaken to see how far the Saba Bank influence extends for these commercially important species. Climate change may have serious effects on the regional dispersal of larvae and the role of the Saba Bank in this needs to be further clarified

GEOLOGY AND GEOMORPHOLOGY
Bathymetric chart of the Saba Bank, with the Overall Bank study area.

The Saba Bank is located at the intersection of three different types of geological activity. It is near the eastern end of the tectonically active Greater Antilles island chain, at the north end of the Aves Ridge and just to the west of the north end of the volcanic island arc chain near the northeastern boundary of the Caribbean Sea. The Saba Bank has intrigued many scientists dating back to the beginning of the century. Spencer (1904; p. 357) considered the Bank to be "a remnant of the coastal plains on the mountainous backbone of the Antillean ridge". He concludes that the Bank "has been levelled by coral growth and the sands derived from them". Vaughan (1919) viewed the Bank as a submarine plateau, levelled by planation agencies, which almost certainly were both subaerial and submarine, which has been submerged in recent geologic time. Vaughan already indicated that the Bank essentially duplicates the atolls in the Pacific. This was later verified by Van der Land (1977) who considers the Bank to be an actively growing atoll, although it is completely submerged, and ranks it among the largest atolls in the world. Davis (1926) viewed the Bank as "an atoll lagoon floor, deprived of its original reef and probably somewhat planed down by low-level abrasion in the post glacial epoch" (Davis 1926, p. 138). Differences of opinion on the formation of Banks such as the Saba Bank have caused heated debate. Vaughan stated that infilling behind barrier reefs could never be the reason for the existence of the Bank, whereas Davis thought this was an essential process.

On the Saba Bank the reef zonation pattern follows a sequence from shelf edge to central Bank. On the eastern portion of the Bank, known as Overall Bank, reef zones occur in the following sequence as one moves from east (windward, open ocean) to west (leeward, towards central Saba Bank): seaward slope, fore reef (with one or more “front reefs”), reef flat, backreef slope (“escarpment”), lagoon, and patch reef (located within the lagoon).

The fore reef zone is a steeply sloping and topologically variable region. Van der Land (1977) observed a “front reef” rising from a “reef terrace” at 30-40 m depth. High-resolution bathymetry confirmed the presence of at least one front reef feature at Overall Bank. To the west (leeward) of the front reef, an area resembling a spur-and-groove reef is found. For the purposes of this management plan, these various reef features are considered elements of a single zone - the fore-reef zone.

Westward (leeward) of the fore reef zone, the reef rises to ~ 15 m depth and forms a wide (> 1000 m) level expanse. Van der Land (1977) identified this area as the reef flat and suggested that it comprised an inner and outer zone distinguished by bathymetry. Examination of recent high-resolution bathymetry data did not differentiate inner and outer reef flat zones within the area of Overall Bank.

The lagoon zone extends eastward (leeward) from the reef flat and backreef slope zones. Van der Land considered the lagoon a single zone, although he distinguished “patch reef’ formations within it. Bathymetry confirmed the presence of patch reeflike features within the lagoon.

Depth profile from high resolution bathymetric data in the “Overall Bank” area on the Eastern edge of the Saba Bank.

MARINE HABITATS, FLORA AND FAUNA, AND NATURAL RESOURCES

Saba Bank: rich mixed reef dominated by gorgonians, with sponges, hard corals, and algae
(Source Juan Armando Sanchez M.). click to enlarge

For a more detailed characterization of habitats in the "Overall Bank" study zone see the report by Wes Toller, 2008: Habitat Surveys of Saba Bank, Netherlands Antilles: An Assessment of Benthic Communities and Fish Assemblages. Unpublished report presented to the Department of Environment of the Netherlands Antilles (MINA) (pdf 2.9 MB)

The marine habitats represented within the Saba Bank can be categorized as follows:

• Open water: supporting planktonic and pelagic sea creatures including fish and migratory species such as whales, dolphins, and sea turtles,
• Sea bed (benthos): supporting coral reefs, algae (and possibly sea grass beds), and infauna (burrowing creatures like mollusks and worms), benthic invertebrates and fish.

There is regular exchange of water, energy and materials between each of these habitats. Organisms also move freely between the different environments for feeding and reproduction. As the waters around the Saba Bank are very deep the Bank has very little, if any, exposure to terrestrial influences. This includes freshwater runoff, sediments, nutrients and any form of coastal pollution, which all stress and eventually kill marine organisms.

Open Water

The open water supports pelagic fish populations, most of which are highly migratory such as Tuna (Thunnus sp.), Dolphin (Dorado / Coryphaena hippurus) and Wahoo (Acanthocybium solandri) as well as Marlin (Makaira sp.) and swordfish (Xiphias gladius) which are found primarily around the edges of the Bank.

While there is little documented information of Caribbean species of turtle that can be found on Saba Bank, there have been several confirmed sightings of Hawksbills (Eretmochelys imbricata) during the 2007 survey, indicating the Bank is a foraging area for them. It is quite likely that the Bank is an important foraging are for Green Turtles (Chelonia mydas) as well due to the large algae fields. Leatherbacks (Dermochelys coriacea), and Loggerheads (Caretta caretta) have been seen on the Bank so it is quite likely that they also use the Bank for foraging, though the leaterbacks were likely only migrating through.

A number of Cetaceans are present on the Saba Bank, including; Humpback Whales (Megaptera novaeangliae), Sperm Whales (Physeter macrocephalus), Spinner Dolphins (Stenella longirostris), and Bottlenose Dolphins (Tursiops truncatus). Humpback whales, migrating north to their mating grounds, are occasionally seen in the channel between Saba and the Bank. A humpback whale with calf was seen on the Bank in the area known as Moonfish Bank during the 2006 expedition. During dives in February 2002 and in January 2006, humpback whale song was heard.

There are a number of birds that live almost exclusively in the open ocean environment, using Saba as a breeding ground or migratory stop over. These include Frigate Birds (Fregata magnificens), Red Billed Tropicbirds (Phaethon aethereus), Brown Pelicans (Pelecanus occidentalis) and Audubon’s Shearwater (Puffinus lherminieri).

Pelagic zone
With the exception of the seabed, everything in blue water beyond the 30m depth contour can be considered the pelagic zone. The pelagic environment is commonly thought of as being made up of number of different ecological zones; most importantly, the epipelagic, mesopelagic and the bathypelagic; we will only be discussing the epipelagic zone.

The epipelagic zone stretches from the surface down to 200 meters. This is where most plants and animals (flora and fauna) live due to the abundance of light and nutrients. Pelagic fish species are found in this part of the sea around the edges of the Saba Bank. This includes small bait fish such as Herring (Clupea harengus) – a major food source for marine mammals, and larger, predatory fish such as the blackfin tuna (Thunnus atlanticus), Wahoo (Acanthocybium solandri) and Dolphin (Dorado - Coryphaena hippurus) all of which are commercially important species.

Healthy and abundant migratory pelagic fish stocks of Tuna, Dolphin and Wahoo are critical to support Saba’s small scale local fishing industry. Globally endangered cetaceans and sea turtles regularly migrate through Saba waters.

Sea Bed

Deep sea bottom
Softbottom habitats make up some of the deep areas along the south east edge. The sediments are usually comprised of a mixture of biologically fixed silica and calcium carbonate, as well as silts, and sand sediments.

There is little known about the deep water environments on the Saba Bank which are beyond the reach of SCUBA divers. However, with the use of a remotely operated vehicle (ROV) it was possible to examine a number of deeper sites on the Bank. Observations made from the ROV indicate that substrate and benthic communities show consistent zonation patterns along the depth gradient of the front reef slope. A transition in the reef fish assemblage was also evident, though less pronounced, along this same depth gradient. Fish diversity was greatest in the reef crest zone and declined with depth, however sightings of commercially important lutjanid species such as silk and blackfin snapper increased with depth.

Some experimental deep water fishing was conducted during the October survey. Some of the fish caught included the snowy grouper (Epinephelus niveatus), saddled moray (Gymnothorax conspersus), sharktooth moray (Gymnothorax maderensis), grey conger (Conger esculentus), and a deep body boarfish (Antigonia capros).

In addition to the surveys at Overall Bank, four ROV surveys were made at two other Saba Bank areas: Poison Bank and Grapplers Bank. The substrate at Poison Bank was comprised of coralline algal nodules or “rhodoliths” which formed extensive rhodolith beds. At Grapplers Bank, a steep rocky escarpment was explored. The near-vertical rocky scarp began at 120 m depth and extended down slope beyond the limits of the ROV survey (157 m depth). Observations made from ROV at Overall Bank suggested a continuous reef system that is relatively uniform and predictable at mid-depths in terms of its structure, substrate composition, and community zonation patterns. In contrast, the few observations made by ROV at Poison Bank and Grapplers Bank revealed habitats that were quite different from those at Overall Bank. This implies that explorations to new areas of Saba Bank are likely to reveal still greater diversity in mid-depth habitat types.

Download full report on ROV observations:
Toller, W., S. Lundvall and P. Hoetjes. 2008. Some observations made from a ROV on mid-depth habitats and reef fish communities of Saba Bank, Netherlands Antilles. Unpublished report presented to the Department of Environment of hte Netherlands Antilles (MINA). (pdf 570 KB)

Research voyages in the Florida Keys which have explored deep water environments have recorded considerable numbers of new invertebrate and fish species. There is every reason to believe that the same would be true of the deep water benthic environment on the Saba Bank. In 2007 two new species of gorgonians were discovered with 8 dives with the ROV. With further sampling it is quite possible that more new species would be discovered.

Coral reefs

The coral reefs are found primarily along the east and southeast edges of the Bank and are rich in terms of cover and diversity of reefbuilding corals as well as gorgonians. There are a variety of reef types on the Saba Bank, from patch reefs through spur-and-groove type reefs with sandy channels. Each of these provides a hard substrate for coral and other animals to settle on, which in turn attracts fish and an abundance of other invertebrates.

The coral reefs are home to many fish species including, Angelfish (Holocanthus sp. and many others), Groupers, Triggerfish, Scorpionfish, Moray eels (e.g. Gymnothorax moringa), Wrasses and Chromis, Parrotfish, and roaming schools of Blue Tangs (Acanthurus coeruleus). In sandy areas Garden eels (Heteroconger halis), Peacock Flounder (Bothus lunatus), Stingrays (Dasyatis Americana) and Flying Gurnard (Dactylopterus volitans) can all be seen. Near to the reefs in the blue water, Black Jacks (Caranx lugubris), Bar jacks (Caranx ruber), Barracuda (Sphyraena sp.) and schools of Horse-eye jacks (Caranx latus) and Wahoo (Acanthocybium solandri) roam around looking to feed off the smaller reef fish.

A new species of Gorgonian coral, of the genus Pterogorgia, discovered on the Saba Bank in only 20 m depth in an area of hard pavement with some sand, with a rich algae community and many gorgonians.

The value of the coral reef of the Bank is not based on tourism, as is the case with the reefs of the Saba Marine Park, with respect to their economic importance to Saba, but its value is in the biodiversity and the habitat they provide for many animals and plants, which commercial and artisanal fisheries depend on. The coral reefs provide a habitat for a wide variety of creatures other than fish and coral. Countless species of crustaceans, worms, anemones, jellyfish, mollusks, echinoderms (seacucumbers and starfish), bryozoans, and sponges live on the reefs.

In addition to all of the animals and plants usually seen around the reefs and other marine habitats, some less frequently spotted species exist. Two turtle species use the waters as a foraging and breeding ground; Hawksbill Turtles (Eretmochelys imbricata) and Green Turtles (Chelonia mydas).

Sharks are often spotted on the Bank, nurse shark, reef shark (Carcharhinus perezi), blacktip shark, (Carcharhinus limbatus), and tiger shark (Galeocerdo cuvier).

Colonized pavement

Distributed throughout the remaining available habitat, wherever there is hard substrate available, there are communities dominated by algae, sponges and/or gorgonians. These communities typically have a less complex substrate with almost no slopes, varying amounts of sand cover, and a moderate energy regime.

Although the structural heterogeneity that supports reef biodiversity is absent, these areas do provide food, refuge, and much sought after space to numerous invertebrates such as lobster, queen conch, and fishes. These communities provide linkages to surrounding marine communities. According to preliminary benthic habitat maps, these communities dominate the seafloor of the central area of the Bank.

Queen Conch

The 2007 study estimated queen conch densities to be higher in areas characterized by sandy substrate and rubble but concluded that they are very patchy in their distribution. Although too few sites were surveyed to draw any firm conclusions the observed densities may indicate that Saba Bank conch stocks are fluctuating at or about the minimum density for effective reproduction. Since there has been no commercial conch fishery since the midnineties (P. Hoetjes, pers. com) this suggests that conch stock has been slow to recover.

Macroalgae

The Rapid Assessment expedition conducted in 2006 (Conservation International, 2006) noted the exceptionally high diversity of macroalgae on Saba Bank. Results from the study conducted in 2007 indicated that macroalgae are the most conspicuous component of benthic communities in all sampled strata. Some twenty new algae species were found on the Bank, which are currently being described. It was unclear what environmental conditions would favor robust macro algal growth on Saba Bank. Perhaps a suite of conditions (upwelling, wave energy, currents, depth and substrate) act collectively to favor growth of macroalgae over other forms of benthic cover. The fact that macroalgae dominated cover in all strata, yet the generic composition of algae varied among strata, indicates that environmental conditions may be favorable for the growth of many different types of macro algae. Acknowledged algae experts M. and D. Littler stated that the Saba Bank is without doubt the richest area in the Caribbean for macroalgae.

Anecdotal observations on macroalgae raise other questions about the ecology of macrophytes on Saba Bank. For example, a site named Twin Peaks had a very lush canopy of Dictyopteris (> 80 % cover, ~ 40 cm average height) in June. When Twin Peaks was revisited in July, the Dictyopteris bed had begun to deteriorate and by August Dictyopteris cover had fallen dramatically to < 5 % of benthic cover. In December and January, many small Dictyopteris specimens were observed. This suggests that at least some macroalgae have pronounced cycles of seasonal abundance on Saba Bank. However, timeseries observations (lasting >1 year) are needed to adequately establish which taxa show seasonality and whether the fluctuating patterns of macro algae abundance follow predictable seasonal cycles.

A diverse macroalgae population is critical to the region’s biogeochemical cycles and serves as an important source of food and possibly pharmaceuticals (Littler and Littler 2000).

Sea Grass Beds

Despite the apparently favorable growth conditions for marine macrophytes on Saba Bank, no seagrasses were observed at any survey sites during numerous surveys. Seagrass beds are clearly not a prominent component of benthic communities at Overall Bank. Previous surveys to other parts of Saba Bank also failed to document the presence of seagrass beds (e.g. Van der Land, 1977, Meesters et al. 1996, RAP Survey, 2006). Thus, there is no indication from available data that seagrass beds are even present on the Saba Bank. This supposition will obviously require more spatially extensive surveys to confirm. However, if preliminary indications are correct, then the traditional view of seagrass beds as critical components of coral reef ecosystems, and especially their role as nursery habitats for fisheries species may not be applicable to Saba Bank.

HUMAN USES

Map of the Saba Bank showing positions of fish traps, anchoring tankers, a ship wreck, and whale sightings. click to enlarge

Fisheries

Full report on the 2007 fisheries survey:
Toller, W. and S. Lundvall. 2008. Assessment of the Commercial Fishery of Saba Bank. Unpublished report presented to the Department of Environment of the Netherlands Antilles (MINA). pdf 440 KB

Report on fish species recorded from commercial catches during 2007:
Toller, W. 2007. Research Note: Fish Records from the Saba Bank Commercial Fishery. Unpublished report presented to the Department of Environment of the Netherlands Antilles (MINA). pdf 770 KB

There are 12 commercial fishing licenses issued for Saban territorial waters and five fishing permits issued for the EFZ, one of which is for Saba. In 2000 fishing provided employment to a relatively large number of people (8% of the economically active population). About 20 people generate a living exclusively from the fishery, while a relatively large group of approximately 30 people find parttime employment in it and generates additional income in the fishery sector (Dilrosun 2000). The income that is generated by the fisheries sector is invested back into the Saba economy, since most of the fishermen are locals. Taxes and income are generated from sales of fuel, two-stroke oil, fishing gear, spare parts and engines. Such associated economic activities are also significant contributors to the island economy. The Spiny Lobster (Panulirus argus) fishery is without doubt the most important fishery on the island. The total lobster catch for 2007 is estimated to be 184,000 lbs (83.6 mt) tons, which represents a gross value of 2.3 million NAf (approximately US$ 1.3 million, Toller et al 2007).

The fishermen primarily fish for lobster on the eastern half of the Bank. This is due partially to the closer proximity to Saba. Some fishermen do fish areas on the Southeast side of the Bank. Bycatch from the lobster pots can be an important factor.

Table 1: Red snapper are the second most commercially important fisheries for Saba

Queen Conch

Queen Conch (Strombus gigas) with egg mass. (source S. Lundvall)

Currently there is no commercial queen conch (Strombus gigas) fishery on the Saba Bank. Historically this area supported large conch fisheries up until the mid nineties and although no hard data exist on the conch population from this time it is suspected that the conchs were severely overfished by foreign fishing vessels. In 1993 two containers full of conch meat from the Saba Bank, ready for export, were impounded on St. Maarten because they lacked the proper CITES documentation. Since the Coastguard started patrolling the Bank and enforcing the fishery legislation in 1996, there has been no commercial fishery for conch.

Fish Spawning Aggregations

The Saba Bank is an important spawning ground for fish species making the Bank an important source for the surrounding regions. This is particularly with respect to red hind (Epinephelus guttatus), queen triggerfish (Balistes vetula)—locally called moonfish—and squirrelfish (Holocentrus adscensionis), which are all known to have spawning aggregation sites on the Bank. The aggregation of the commercially important red hind occurs during the winter months (November till the end of February) around the full moon. The spawning aggregation area is 2.1 km long and 20-30 m wide, and runs along the edge of an old spur and groove reef. One specific area of the Bank is called the Moonfish Bank, after the large numbers of queen triggerfish caught there during the same months presumably because it is also a Spawning Aggregation Area.

Traditionally the Sabans would fish the triggerfish and red hind during the spawning aggregations, though not on a large scale. There are indications that this is changing with respect to red hind with the fishery increasing. Queen triggerfish may already have been depleted to such an extent that the spawning aggregation is not noticeable anymore, but this remains to be verified.

Tourism

Tourism on the Bank is still undeveloped. The local dive operators on Saba currently have no interest in offering dive trips to the Bank. Live aboard dive operators active in the region are not currently diving on the Saba Bank but could easily develop an interest once information about dive sites becomes available. Fishing charter boats from St. Maarten do take clients to fish the Saba Bank but the information on this is limited and likely not of large economic importance.

During the hydrographic survey carried out by the Dutch Hydrographic Service in 2006 a wreck was discovered on the Saba Bank. In 2007 a survey crew explored the wreck to determine the origins and potential for dive tourism. The boat is in 120 ft of water and is positioned upright on a sand bottom. Due to the amount of growth on the hull a name or registration could not be determined. The hold was explored and it appears to have been a cargo ship carrying a cement shipment. The Saba Island Government is currently investigating the origins of this ship. The wreck is positioned 22 km westsouthwest from the island of Saba. Due to the concentration of sea life around the wreck this site might have the potential to develop into a dive tourism site. Other sites with spectacular reef formations might similarly be developed by providing infrastructure for dive tourism in the form of mooring buoys and site descriptions. This would become even more feasible if the Saba Bank receives PSSA status from the IMO, giving it international recognition as a special area.

Oil and Gas

The geological history of the Saba Bank indicates that there is a reasonable chance for the presence of oil or gas. Consequently, extensive seismologic research and two drillings have been conducted on the Saba Bank. However, though producing a wealth of geological data, explorations in 1977 and 1982 did not detect any significant amount of oil or gas.

Sand

So far, the only commercial mineral identified on the Saba Bank is sand. Sand is only present in the
central parts of the Bank (Van der Land 1977). However, the 2007 study found it to be mostly only a thin layer, and not worth mining. Mining would also be expensive because of the general depth of the Bank. The presence of many patch reefs in the middle of the Bank may also obstruct and damage mining equipment. All indications are that sand is only present in limited amounts and mining would not be a sustainable use of the Bank and would seriously impact the rich bottom habitats.

Pharmaceuticals

Coral reefs are important as an inexhaustible source of chemical compounds, potentially beneficial to humans. One field of medical research against AIDS and cancer focuses on the discovery of new products from marine organisms. To date, medicines have already been developed from compounds isolated from gorgonians and sponges. Algae are also known to be potential sources of pharmaceutically active substances. Presently, the Saba Bank is not being used for this purpose. However, its rich biodiversity and the recent discovery of many new seaweed species and two new gorgonian species might form the basis for future explorations.

CRITICAL THREATS TO THE SABA BANK

Special interest species

Endangered Species

The Saba Bank is a home, a migratory stopover, or a breeding site for at least 16 species that are in some degree of danger according to the IUCN Red List, ten species listed on CITES Appendix I as endangered, and one CITES Appendix II species that has been overfished in most of its range (Strombus gigas, the Queen Conch). Whales are often heard during January-April as they migrate past, Humpback Whales in particular can be seen breaching from the Southern tip of the island. Dolphins, porpoises as well as sperm whales have also been sighted on the Bank

Table 2: IUCN Red List Species of some degree of concern, found on the Saba Bank

Threats change over time, and it is important to anticipate the potential negative impacts of certain activities, and consider them when making management decisions and amendments to the Management Plan

The four main threats to the Saba Bank are:
• Overexploitation of fishery resources
• Impacts from tanker anchorage on benthic communities
• Impacts of tanker traffic on fishermen and traps
• Global climate change

Overexploitation of fishery resources

The primary users of the Saba Bank are the fishermen from Saba, who have been fishing there since the previous century. Fishermen from neighboring Caribbean islands also fish on the Saba Bank. Intensive fishing methods may have reduced the queen conch populations severely in many places, though no data are available (Meesters 1996). Data from the 2007 study (Toller 2007), although insufficient for clear conclusions, appear to indicate that conch populations may be around the minimum threshold level for harvest density. This evidence indicates conch harvesting should not be permitted on the Bank.

In 2000, Faisal Dilrosun (2000) completed a comprehensive examination of the Saba Bank commercial fishery. Dilrosun performed extensive sampling of commercial catches—particularly for lobster size. His study provided baseline data to compare to current harvest patterns and stock condition as surveyed in the second half of 2007 (Toller 2007). The findings indicate that Saba Bank fishermen of 2007 exert a greater fishing effort in order to maintain lobster landings at year 2000 levels. An increase in fishing effort coupled with a decrease in observed catch rate could suggest that lobster harvests are now at, or exceed, the maximum sustainable yield for Saba Bank stocks. However, more definitive conclusions about trends in lobster stock abundance are not possible owing to the limited time frame of available fisheries data sets. The importance of redfish, as a percentage of total annual landings, has increased by threefold since 2000. The commercial fishery now harvests redfish primarily with fish traps, in contrast to hook & line fishing methods that predominated in 2000.

Tanker traffic

Ship traffic is constant in the area of the Saba Bank. There are many cargo, cruise ships, and tankers passing over the Bank. The primary reason for the heavy traffic is the oil transhipment facility located on St. Eustatius 25 miles southeast of Saba. This is a storage facility that is mainly used for oil being transported from the Middle East to the USA. It operates 50 storage tanks with a capacity of approximately 11 million barrels. The number of ships visiting the port each month is approximately 100.

The heavy ship traffic on the Saba Bank poses a danger to the small (avg. 40 ft LOA) artisanal fishing boats, which run the risk of being overrun by the large tankers. This risk has, according to the fishermen, caused them to avoid certain traditional fishing grounds, impacting their catches.

As the ships pass over the Saba Bank they often run over the marker buoys of the lobster and fish pots that are set all over the Saba Bank. This results in the loss of the buoys and displacement of the traps and, consequently, the loss of the traps. The number of traps lost annually due to ship traffic can run to several hundred, causing serious ecological consequences because such lost traps continue to catch fish and lobsters until they are completely corroded. In addition, the economic losses incurred by the fishermen are substantial.

Impacts from tankers also include rinsing, oil spills, discharge of sewage, and of ballast water, which may contain invasive species. This type of impact is difficult to quantify but can have an indirect or long term effects.

Tanker Anchorage

Some ships, mostly oil tankers, do not just pass over, but anchor on the Bank while waiting to load at Statia Oil Terminals or simply waiting for their next job. Tankers are actually advised to anchor on the Saba Bank to avoid paying mooring fees to Statia's Ports Authority (Lloyds Shipping Guide, p. 1420). Anchoring ships are both tankers and cargo ships with a depth range between 9 and 12 m. Larger tankers avoid the Bank when they are fully loaded because their depth is between 12 and 20 m, which is more than the water depth in the shallow areas of the Bank. Damage to the benthic community can occur during setting, retrieval and while at anchor. The anchors and their chains can destroy a relatively large reef area completely in a very short time. Because the ships often remain anchored for many days the damage can be enormous. The eastern and southeastern edges of the Bank, which support the most coral reefs, should be considered very sensitive to anchor damage. Bilge and wastewater, and hull cleaning activities possibly releasing toxic paint from anchored ships are also a concern.

The frequency of anchoring is variable throughout the year. During the months of September and October of 2007 three tankers at a time have been seen anchoring on the Bank. Due to the total size of the Bank it is impossible to monitor the whole Bank from Saba but fishermen have reported tankers anchoring on the west side of the Bank. While these reports do not capture all the anchorages it is clear that tankers, as well as cargo ships use the Bank frequently as an anchorage site.

Ship grounding and collisions

Ship groundings and collisions on the Bank, though they have not yet happened, could cause great damage to the Saba Bank coral reefs (see for example Hudson and Diaz 1988). The actual likelihood of a grounding accident is unknown, but grounding of large tankers appears a genuine danger if ever engine failure occurs, because the prevailing winds and currents would carry the tanker rapidly from Statia towards the Bank. The potential effects may be aggravated when groundings or collisions are accompanied by an, oil spill, which would endanger the fisheries (see previous section). The draught of large oil tankers is deeper than the average depth of the eastern and southeastern rim of the Bank.

There has been one sinking of a boat on the Saba Bank. During the 2007 Saba Bank Project an old wreck, discovered the previous year on the north portion of the Bank, was explored. It is believed to be the wreck of a cement boat that sank on the Bank in the mid 1970’s.

Global Climate Change

Increases in ocean temperatures associated with global climate change will increase the number of coral bleaching episodes. High water temperatures stress corals leading to “bleaching”—the expulsion of the colorful, symbiotic algae that corals need for survival, growth, and reproduction. While coral species have some capacity to recover from bleaching events, this ability diminishes with greater frequency, severity, or duration of bleaching. As a result, climate change is likely to reduce local and regional coral biodiversity, as sensitive species are eliminated. The effects of global climate change will combine with more localized stresses to further degrade coral reef ecosystems. Although climate change itself will adversely affect coral reefs, it will also increase the susceptibility of reef communities to degradation and loss resulting from intensified natural climate variability such as El Niño events and increased hurricane intensity, as well as disease, overfishing, disruption of food webs, and pollution from neighboring human communities.

In 2005 the Caribbean experienced a major coral bleaching event. There has been no monitoring on the Bank but there has been a notable change in live coral cover on the reefs. One site in an area known as Coral Gardens was visited in 2002 and this area was used in an informational video about the Saba Bank. This site was again visited during the 2007 dive survey and the coral cover was greatly reduced. Based on this comparison, as well as a general impression of coral cover, the pre-bleaching event and post-bleaching event data show that the impact of the 2005 bleaching event has been very significant.

Well developed reef with large coral colonies, almost completely dead and covered with algae, presumably the result of 2005 bleaching and its aftermath of disease mortality (source: Juan Armando Sanchez)

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