Saba Bank

A dedicated Saba Bank Symposium was organised by the University of Wageningen in December 2016. The Symposium was held in Den Helder and brought together researchers and conservationists from throughout the Kingdom to share their knowledge and to provide an overview of the current state of scientific knowledge about the Netherland’s largest and most remote National Park.

Among others, presentations were given on the following topics:

• Where does our interest in Saba Bank come from? by Paul Hoetjes
• State of the reefs: 3 expeditions to Saba Bank by Erik Meesters
• Fish and fisheries at Saba Bank by Martin de Graaf
• Importance of Saba Bank for local communities, by Kai Wulf
• Research by NIOZ on the Saba Bank, by Fleur van Duyl
• Coral diversity and historical collections of Saba Bank, by Bert Hoeksema
• Shark habitat use, by Erwin Winter
• Listening to the Bank: whales and dolphins, by Dick de Haan

The Symposium ended with a panel discussion on the sustainable use of the Saba Bank and what is needed to protect the Saba Bank for the future.

We have done our best to capture the wealth of information presented at the symposium for you in our BioNews letter and hope, that like us, you are impressed by the depth and diversity of the work that has been done to explore and document our largest National Park: The Saba Bank.

To read this interactive Pdf, please make sure to have Adobe Acrobat Reader installed on your computer. We recommend you to open BioNews in full screen.  In case you do not have this program, please click here to download. Feel free to email research@DCNAnature.org in case you experience any issues downloading the program so we can assist you.

BioNews is produced by the Dutch Caribbean Nature Alliance and funded by the Ministry of Economic Affairs.

A small submersible remotely operated vehicle (ROV) was used to explore mid-depth habitats of Saba Bank – a submerged carbonate platform in the northeastern Caribbean Sea. The ROV enabled observation and specimen collection to greater depths (40 to > 150 m) than possible with conventional scuba methods. The topography, substrate, benthic communities and fish assemblages of a prominent front reef system at Overall Bank were examined in some detail. Observations made from 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 (number of species observed per survey) was greatest in the reef crest zone and declined with depth, however sightings of commercially important lutjanids species such as silk and blackfin snapper increased with depth. Significant cover by reef-building corals (i.e. constructional reef development) was only evident in the reef crest zone, and terminated at 38 to 42 m depth. Substrate of the transition slope zone, from 42 m to 75 m depth, was primarily a hard bottom consisting of consolidated reef structures and rubble with sand interspersed. Sponges, gorgonians and macro algae dominated the benthic community there. In the deep slope zone (> 75 m depth), a soft bottom substrate predominated that was composed of fine, readily resuspended sediments together with scattered rubble fragments. Benthic invertebrates were very sparse in the deep slope zone. 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 rhodoliths 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 future ROV explorations to new areas of Saba Bank are likely to reveal still greater diversity in mid-depth habitat types.

Abstract

Most gorgonian octocoral species are described using diagnostic characteristics of their sclerites (microscopic skeletal components). Species in the genus Pterogorgia, however, are separated primarily by differences in their calyx and branch morphology. Specimens of a morphologically unusual Pterogorgia collected from Saba Bank in the NE Caribbean Sea were found with calyx morphology similar to P. citrina and branch morphology similar to P. guadalupensis. In order to test morphological species boundaries, and the validity of calyx and branch morphology as systematic characters, a phylogenetic analysis was undertaken utilizing partial gene fragments of three mitochondrial (mtMutS, cytochrome b, and igr4; 726bp total) and two nuclear (ITS2, 166bp; and SRP54 intron, 143bp) loci. The datasets

for nuclear and mitochondrial loci contained few phylogenetically informative sites, and
tree topologies did not resolve any of the morphological species as monophyletic groups. Instead, the mitochondrial loci and SRP54 each recovered two clades but were slightly incongruent, with a few individuals of P. guadalupensis represented in both clades with SRP54. A concatenated dataset of these loci grouped all P. anceps and P. guadalupensis in a clade, and P. citrina and the Pterogorgia sp. from Saba Bank in a sister clade, but with minimal variation/resolution within each clade. However, in common with other octocoral taxa, the limited genetic variation may not have been able to resolve whether branch varia- tion represents intraspecific variation or separate species. Therefore, these results suggest that there are at least two phylogenetic lineages of Pterogorgia at the species level, and
the atypical Pterogorgia sp. may represent an unusual morphotype of P. citrina, possibly endemic to Saba Bank. Branch morphology does not appear to be a reliable morphological character to differentiate Pterogorgia species (e.g., branches “flat” or “3–4 edges” in P. gua- dalupensis and P. anceps, respectively), and a re-evaluation of species-level characters (e.g., sclerites) is needed. 

Although little fisheries data exist for red hind, Epinephelus guttatus (Linnaeus, 1758) on the Saba Bank, Netherlands Antilles, spawning aggregation characteristics from other populations can be used to assess the health of a red hind spawning population previously undocumented there. In December 2005, a spawning aggregation site for red hind was surveyed on Saba Bank at 17°33.6´N, 63°17.7´W. Red hind aggregated on the northeast edge of the bank, in an area of 0.053 km2 . Spawning occurred in January 2006 during the week prior to and possibly after the full moon. Reproductively developed males and females were collected from December through February, however, in January average fish density increased from 1.46 ± 0.26 fish 100 m–2 to 34.27 ± 2.20 fish 100 m–2 and the M:F sex ratio shifted from 4:1 to unity. Fish were observed exhibiting little territorial or haremic behavior. Gonadosomatic indices in females reached high daily averages in January and February of 15.86 ± 5.4 and 6.93 ± 2.40 respectively, one day prior to the full moon. Average daily water temperature dropped throughout the study period, and during the week prior to the full moon in January, ranged from 26.7 °C to 26.5 °C. Current direction was dominated by tidal fluctuations but during the spawning period was predominantly directed to the southwest. Comparison of spawning population characteristics across red hind aggregation sites in the eastern Caribbean under varying degrees of protection suggests that the Saba Bank aggregation is moderately exploited and should be monitored and more closely managed.

Many environmental variables may influence fish assemblage structures in terms of abundance, biomass and mean size. The aim of this study is to provide a baseline survey on reef fish assemblages and shark presence covering the whole Saba bank (Dutch Caribbean). Hereby determining the influence of habitat, depth and fishing pressure on the structure of reef fish assemblages and shark presence. Baited Remote Underwater Video (BRUV) survey was used to describe reef fish assemblage structures on the Saba bank. Between 2012-2014, a total of 165 60 min BRUV deployments were conducted on locations varying in habitat complexity (0-4, Polunin and Roberts, 1993), depth (15-40m) and fisheries. The eleven most abundant fish species observed on the Saba bank represented eight families and accounted for nearly 50% of the total number of individual fish observed. Labridae was the most abundant fish family observed with a relative abundance of 22%. Most abundant fish species by number of individuals were Thalassoma bifasciatum (N=849 (9.8%)) Stegastus partitus (N=725 (8.4%)) and Acanthurus bahianus (N=430 (5.0%)).

Habitat complexity was positively correlated with species richness (Nsp), fish abundance (MaxN), and mean biomass, and negatively correlated with mean fish length. Strongly developed vertical relief habitats were found to support high numbers of fish species (N=19.1±0.6SE) of relatively low mean lengths (22.4cm±0.3SE), whereas less complex habitats were characterized by low numbers of species (N=8.3±0.8SE) with relatively high mean lengths (24.6cm ±0.81SE). Depth was negatively correlated with Nsp, MaxN and mean biomass and positively correlated with mean fish length. These relationships were all according to expectations based on earlier studies.

A minor part of the variability in the structure of reef fish assemblages was explained by differences in fisheries activity, indicating that no clear fisheries effect was observed in fish assemblages in this study. Furthermore, no significant differences in average size of target species were observed between areas with different fishing pressure. However, the general absence of piscivores such as large snappers and groupers was an indication of the indelible effects of past fisheries on the Saba bank.

A total of 85 shark observations were made with Ginglymostoma cirratum as most abundant species (N=41), followed by Carcharhinus perezii (N=36), Galeocerdo cuvier (N=5) and Carcharhinus limbatus (N=3). Relatively high shark abundances (0.20 sharks hour-1) were observed on the Saba bank compared with other Caribbean regions (The Bahamas: 0.14 sharks hour-1, Belize, 0.17 sharks hour-1). Shark abundance (CPUE) was positively correlated with habitat complexity, whereas depth exerted a negative influence on shark abundances. High shark numbers are a good sign for the health of the Saba Bank ecosystem, since sharks are apex predators, making them a prime indicator for ecosystem health.

Besides ‘traditional’ measures, ecomorphology was presented as an alternative measure in explaining variation in reef fish assemblages. For ecomorphological analysis insight in trophic morphology was obtained by using a Fish Food Model (FFM). The FFM in this study quantitatively related properties of 14 marine food types to morphological characterics of 15 common fish species on the Saba bank and predicted the capacity of utilizing these food types for each species. Strong differences in morphology and little overlap was observed for all different fish species in the FFM-analysis, which was mainly explained by two sets of variables involving predatory and herbivorous lifestyle. By multiplying each species’ capacity of using food types with its abundance an ecomorphological profile of each fish assemblage was calculated. On a functional level reef fish assemblages showed less variability than on species composition level, this possibly is an indication for high levels of robustness in niche differentiation in reef fish communities on the Saba bank.

Contour map of the Saba bank (GIS)
 

 

The Saba Bank is the largest submerged carbonate platform of 2,200 km2 in the Caribbean Sea, which lies partially within the Exclusive Economic Zone of the Netherlands and partially within the territorial waters of Saba and St. Eustatius. The Saba Bank houses an expansive coral reef ecosystem with a rich diversity of species and as such is also an important source of commercial fish for the nearby islands.

The Saba Bank furthermore forms the largest protected area of the Kingdom of the Netherlands, after the Dutch part of the Wadden Sea in Europe. It was declared a protected area by the Dutch Government in 2010 and has been registered as such in the Specially Protected Areas and Wildlife (SPAW) protocol of the Cartagena Convention for the Protection and Development of the Marine Environment of the Wider Caribbean. In 2012 it was internationally declared a Particularly Sensitive Sea Area (PSSA) by the International Maritime Organization (IMO) and an Ecological or Biological Significant Area (EBSA) by the Convention on Biological Diversity (CBD). As there are no large land masses nearby, the Saba Bank can be considered as relatively pristine and remote from human influences. Anthropogenic threats such as fisheries and environmental threats such as climate change, sea surface temperature increase and acidification, however, also threaten the Bank’s coral reefs.

As part of the Saba Bank research program 2011-2016, commissioned by the Dutch Ministry of Economic Affairs (EZ), expeditions to the Saba Bank were conducted in October 2011 and from 19 to 26 October 2013. The Saba Bank research program aims to obtain information on the biodiversity, ecological functioning and carrying capacity for commercial fisheries to facilitate sustainable management of the area. The expedition was funded by the Dutch Ministry of Economic Affairs and the World Wildlife Fund in the Netherlands.

The primary objectives of the 2011 and 2013 research expeditions were to collect data on benthic and reef fish communities, and on sponges and nutritional sources of the sponge community. Studies added to the 2013 expedition were research into the structural complexity of the reef; coral-algal interactions; and connectivity between populations. An international, multidisciplinary team of marine biologists investigated the coral reef structure as well as the spatial variation in species assemblages and population genetic connectivity of corals, algae, fish and sponges during eleven SCUBA dives at 20-30m depth.

During the expedition thirty-three 50m long transects resulted in more than 2000 images of the reef, and over 5000 fish counts of almost 100 fish species. A preliminary comparison with the data from 2011 gives the impression of a reduction in snappers, groupers and grunts, while there were noticeably more sharks. There were fewer algae on the Saba Bank than in 2011, possibly indicating a healthier reef, although there appeared to be a gradient of increasing algal cover towards the island of Saba. It seems unlikely that this is related to anthropogenic activities on the island, but more likely to natural causes.

An overview of collected data and preliminary results is given in this progress report. Further comparative analysis between the data collected in the 2011 and 2013 and further analysis between research components, e.g. between algal biomass, herbivorous fish biomass and nutrient levels, will be performed in 2014. This may give more information on the potential causes of the observed south-north algal gradient.

The expedition elicited large public interest and media coverage in both Dutch and Caribbean media (details provided in Appendix F). The work of the researchers, both above and under water, was also recorded on film as part of the documentary series Marine Life for Discovery Channel.

Findings

A management plan was prepared in close consultation with a considerable number of stakeholders and stakeholder group representatives.

The plan specifies management goals and strategies for the Saba Bank Management Organization (SBMO) related to the organization mission. It also identifies the major existing and potential threats and issues facing the Bank from ecological, social and cultural perspectives and includes substantial input from stakeholders. It is designed to be an adaptive management tool.

Below is a very brief overview of the management plan

Part I: Saba Bank Background Information

• Location and situation
• Geology and geomorphology
• Marine habitats, flora and fauna and natural resources
• Human uses
• Critical threats to the Saba Bank:
• Overexploitation of fishery resources
• Impacts from tanker anchorage on benthic communities
• Impacts of tanker traffic on fishermen and traps
• Global climate change

PART II: Management Environment

• Vision: To secure a natural protected area that represents a unique and spectacular ecosystem; Mission: To contribute to the preservation of Saba’s natural heritage and promote the sustainable use of the natural resources; and Goals.
• Governance
• Human resources
• Physical resources
• Finance
• Stakeholders

Summary of Issues (see below)

Management Recommendations (PART III: Management Environment)

Key issue: Create a clearly defined conch reserve on the Saba Bank.
Actions: Create and implement the queen conch reserve with no commercial take of conch. Research into queen conch stocks.

Key issue: Monitor the landings of commercial fish catches (there is currently very little data available on the yearly landings from the commercial fishermen of Saba).
Actions: Collect records of fishing activity on the Saba Bank. Develop a system to report landing from commercial fishermen. This dataset will lay the foundation for establishing a long-term commercial fisherman reporting system, which in turn will enable the SBMO to assess the state of the Saba Bank’s fish stocks.

Key issue: Enforcement of fisheries regulations (there is currently minimal enforcement of the fisheries regulations)
Actions: Collaboration; work with the Government, Harbour Office and Police to establish clear enforcement procedures and publicize the outcome. Encourage local fishermen to work with the police in the enforcement of the regulations. The SCF is in the process of having one of their rangers trained as a special agent.

Key issue: Monitor red hind spawning aggregation; assist in the development of a spawning aggregation closed season.
Actions: Gather initial information: determine where the majority of the fishermen are from and gauge trends in fish densities during the aggregations. Consult with stakeholders, including both the public and fishermen. Provide assistance in draft legislation for closing the spawning aggregation.

Key issue: Monitor tanker anchorage damage on the Saba Bank.
Actions: Monitor the impacts of anchoring. Prevent anchorage within the 12 miles of territorial waters. Provide whatever support is required for the Central Governments proposal to have the Bank recognized as a Particularly Sensitive Sea Area (PSSA).

Key issue: Evaluate the potential for artificial reef development on the Saba Bank.
Actions: Create and monitor an experimental artificial reef.

Key issue: Monitor and evaluate coral health.
Actions: Continue to monitor bleaching. Continue to monitor the state of the coral at existing sites established in 2007 on a regular basis. Adapt methods where appropriate. Co-ordinate with other islands. Communicate methods and results with St. Eustatius, St Maarten, and other DCNA islands, as well as the regional Global Coral Reef Monitoring Networkm (GCRMN) nodes.

Key issue: Facilitate and promote research from visiting scientists
Actions: Promote scientific research on the Bank (conferences, local, national media, and presentations). Provide assistance to researchers (providing logistic support and access to equipment)

Key issue: Work with the commercial fishermen in the management of the fisheries resource.
Actions: Promote the creation of a fisheries association among the fishermen as key stakeholders.

Key issue: Establish sustainable financing mechanisms
Actions: Raise money from fishing permits. Seek structural funding from the Dutch government under the new constitutional relationships.

Findings

The main conclusion from this study is that no new fishing permits should be issued until a long-term fishery monitoring program is in place. The study emphasizes the need for effective enforcement of existing regulations.

Findings from the study include:

• 14 fishing vessels use the Saba Bank.
• Saba Bank fishermen engage in two types of fisheries: a spiny lobster fishery (most frequent), and a snapper fishery (least frequent).
• The total lobster catch amounts to about 90 tons per year and the total red snapper catch amounts to about 12 tons per year.
• A considerable number of traps are lost due to ship traffic and hurricanes. None of these traps are fitted with a biodegradable panel, so the lost traps pose a huge threat to the fish stock of the Saba Bank.
• In 1999, the Saba Bank fishery sector generated a gross economical value of 1.1 million US$.
• An important issue that came out of this study is that a substantial part of the landings of lobsters consist of illegal lobster catch. High percentages of under-sized lobsters and berried lobsters in the catch are a serious concern. A high percentage of lobsters landed are under the legal size limit and a substantial percentage of berried lobsters are landed. The mean CL (carapace length) of lobsters from the Saba Bank (10.7 cm) was set at this level so that future harvesting is not endangered as long as the legal size regulation is strictly enforced. 

Management Recommendations:

Fishery regulations must be strictly enforced for a successful management of the Saba Bank fishery:

(As a direct result of this catch assessment survey the Coast Guard of the Netherlands Antilles has commenced to strictly enforce the fishery regulations.) The following regulations are currently being enforced:

• Legal mesh size
• Use of the biodegradable panel
• Legal size limits for lobsters
• No landing of berried lobsters
• No landing of soft-shell lobsters (lobsters in ecdysis)
• Requirement of Fishing License for both Saban Territorial Waters and Economic Fishery Zone (EFZ) of the Netherlands Antilles.

The implementation of the fishery regulations by the Coast Guard of the Netherlands Antilles has resulted in a substantial decline in illegal fishery activities:

• The number of under-sized lobsters has decreased, and practically no berried lobsters and lobsters in ecdysis were brought in.
• Illegal (non-licensed) fishing activities from both foreign and domestic vessels have practically stopped.

Restrictions should be made on landing berried lobsters and lobsters in ecdysis, and on catch and effort through size limits (lobsters).

The total fishing effort for snappers should not be increased until more data is available (average length of the main snapper species of the Saba Bank is relatively small).

Further research and accurate catch and effort and length-frequency data are required to formulate sound regulations.

A communication network should be developed which involves fishermen, Central and Island Governments, the Coast Guard and the research community.

Both the Saba island Government and the Central Government need to strictly enforce the regulations concerning the legal mesh size and the biodegradable hatch for traps to reduce the amount of ghost traps on the Saba Bank.

The lobster fishery should not be expanded; there are already concerns that the fishing effort might have reached sustainable levels of exploitation.

Continued monitoring of the fishery is needed to show clear trends on the lobster fishery exploitation level.

The Central and/or Saba Island Government should ensure that data continues to be collected and interpreted.

Fishermen should be encouraged to exploit the resources of the Bank in a sustainable manner.

Both the Central Government and the Saba island Government should conform to the inspection procedures and standards required by the EC, so that fish products can once again be legally exported to the French islands.

It is recommended that both the Central Government and the Saba island Government specify the nature of the fishing licenses per target species. The resource users should pay a fee for these licenses according to regional standards. The income generated from the fishing licenses fee can be used for management and monitoring of the fishery, whereby the resource users contribute to the management and monitoring of the stock.

Abstract:

This paper provides a context for the results of recent biodiversity surveys of Saba Bank.

Recent biological surveys of corals, fishes, and algae emphasized habitat diversity and the relative richness of the marine flora and fauna. These assessments formed the basis for a management plan to protect Saba Bank’s biodiversity and a draft proposal seeking Particularly Sensitive Sea Area (PSSA) status for the Bank. The intention of the PSSA proposal is to protect the benthic habitat on Saba Bank from anchor damage. It is hoped that this collection will serve as a knowledge baseline and provoke further research in the area.

Findings:

Meesters et al, 1996: review of existing knowledge and quick field survey of Saba Bank.

• This study confirmed that Saba Bank is of great interest, both geologically and biologically.
• This study confirmed that the area is a regionally unique ecosystem, relatively pristine and remote from human influences, with high biological diversity and productivity.
• The study highlighted threats from overfishing and anchoring by large tankers.
• Meesters recommended further study of Saba Bank, improved legislative instruments, including international instruments, and enforcement to control current and future activities as well as capacity and awareness building.

This study formed the basis for the N.A government’s policy for Saba Bank. Lack of resources and capacity delayed implementation of this policy.

Dilrosun, 2000: first in-depth fisheries catch assessment that provided solid data about the state of the Saba Bank’s fisheries.

• This study concluded that no new fishing permits should be issued until a long-term fishery monitoring program was in place.
• The study emphasized the need for effective enforcement of existing regulations.

This study had immediate effects on Saba Bank policy; the island government of Saba declared a moratorium on fishing permits and a capacity building effort to strengthen the Coast Guard’s enforcement of existing regulations began.

Several studies were requested so as to demonstrate that the Saba Bank satisfies all the criteria that the International Maritime Organization requires for the area to become a Particularly Sensitive Sea Area (PSSA)

2006 Rapid Assessment Program (RAP) of Saba Bank: the aim was to produce appropriate and realistic conservation recommendations.

• This survey really demonstrated the richness of the Saba Bank’s biodiversity.
• Many new species were reported, and Saba Bank was found to have a uniquely diverse marine macro-algal flora.
• The expedition brought worldwide publicity for Saba Bank and helped to earmark Dutch development funding for further study of the Bank.

2007 high-resolution bathymetric GIS map of Saba Bank

• The map was produced using the Navy’s sonar data within a Geographic Information System (GIS) framework.
• The map formed the basis for further study of Saba Bank.

2007 Second Fisheries Assessment: the goal was to assess the crustacean and gorgonian fauna of Saba Bank.

• Two undescribed octocoral species were discovered
• Two different shallow water gorgonian habitats were distinguished

The number of anchoring tankers and the damage caused by them was documented through a vessel monitoring system and the report of a few cases.

Saba Bank Management Plan Draft

• In-depth description of Saba Bank’s biodiversity.
• More data on the use being made of the Bank.
• Better idea of the habitats present on the Bank.

A PSSA status proposal has been drafted and is currently being finalized.

New legislation to regulate international shipping in the waters of the Netherlands Antilles, needed in order to submit a PSSA proposal to the IMO, was passed. This legislation also makes it possible to declare the area an EEZ (another requirement for the PSSA proposal). The process is underway and is expected to be finalized in 2010. The anchoring prohibition will also be extended to the whole of the Bank in 2010.

Management Recommendations:

• Further study and monitoring of the Bank’s biodiversity and use will be required to guide the Bank’s management in a feedback loop.
• Interaction of biodiversity research and policy development is essential to developing effective management of biodiversity and public support.
• Carry out further research into the various habitats of the Bank, about which far too little is as yet known. To date, only a very small part of the huge area has been adequately sampled.
• Another priority is a study of marine mammals on Saba Bank to determine their presence and use of the bank. Anecdotal evidence suggests that humpback whales may use the Bank for calving, and sperm whales may find prey around the steep edges of the Saba Bank platform. Other areas of research that would contribute to more effective management include further studies of conch (Lobatus gigas) and lobster (Panulirus argus) populations, and sea turtles’ use of the Bank. Socio-economic studies would also be welcome.