Saba Bank

Special Edition Tiger Shark Expedition 2021

The Dutch Caribbean waters are home to more than thirty species of sharks and rays. With the creation of the Yarari Marine Mammal and Shark Sanctuary in 2015, these species have received increased attention and protection.  The intention of this sanctuary was to create a network of protected habitats stretching across the Caribbean.  Currently this sanctuary includes the waters around the islands of Saba, St. Eustatius and Bonaire.

Saba Bank

A recent expedition to the Saba Bank focused on learning more about tiger sharks and how they use this habitat.  Saba Bank, located 11 kilometers from Saba, is a submerged atoll world renown for its rich biodiversity.  This seamount rises 1800 meters from the sea floor and is topped with over 100 square kilometers of coral reef. This area is the largest national park within the Kingdom of the Netherlands.

The Expedition

Photo credit © Daniel Norwood (all rights reserved)

The Tiger Shark Expedition was the first of its kind for the Saba Bank.  During this project five satellite tags were attached and researchers confirmed the pregnancy stages via ultrasound for two different species of sharks.  In total, 56 sharks, including 16 tiger sharks, were identified.

This project was a collaborative effort by the Protected Area Management Organizations of the Dutch Caribbean: Saba Conservation Foundation (SCF)Nature Foundation St. Maarten (NFSXM), St. Eustatius National Parks (STENAPA)STINAPA Bonaire, the Aruba National Parks Foundation (FPNA), the Dutch Caribbean Nature Alliance (DCNA) and World Wildlife Fund for Nature- The Netherlands (WWF-NL), Arizona State UniversityUniversity of GroningenBeneath the Waves and funded by the Biodiversity Fund of the World Wildlife Fund for Nature- The Netherlands (WWF-NL) and Dutch Postcode Lottery.

 

Photo credit © Daniel Norwood (all rights reserved)

 

This special edition BioNews is the culmination of these efforts.  Understanding the shark species that utilize the Dutch Caribbean waters is crucial step in improving conservation measures moving forward.

 

 

 

The full special edition can be found here: https://dcnanature.org/tiger-shark/

 

 

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Saba
Saba bank
St. Eustatius
St. Maarten
Author

Reef Sharks Move to Deeper Water as They Mature

A new study from Wageningen University & Research (WUR) showed that reef sharks utilize different areas of the reef throughout their lifetime. Using baited video cameras, six different species of reef sharks were recorded around the northern Dutch Caribbean islands. These results will impact the design and implementation of shark conservation strategies for years to come.

 

Reef Sharks

Reef sharks play a critical role within the ocean. As a top predator, reef sharks help maintain the delicate balance within (coral) reef environments. In fact, research has found that reefs with healthy shark populations are more resilient and capable of withstanding the pressures of climate change, pollution, overfishing and diseases.

Juvenile Sharks

Understanding the dynamics of habitat use of local shark populations is critical when designing effective marine conservation strategies. This is exactly what the latest reef shark study from WUR hoped to achieve. Using baited remote underwater video cameras at 376 locations around the reefs of Saba, Saba Bank and St. Eustatius, fish ecologist Twan Stoffers and his colleagues recorded 126 different shark sightings.

Of the six different species recorded in this study, juvenile Caribbean reef sharks (Carcharhinus perezi) and nurse sharks (Ginglymostoma cirratum) were most commonly recorded. Overall, they observed young sharks in shallow, more complex areas of the reef, whereas the larger, more mature, sharks were observed further away from the reef in deeper habitats up to 65 meter depth. Larger nurse sharks were frequently recorded in seagrass beds. The researchers were surprised that hardly any adults were observed over the course of the entire study.

Implications

This knowledge could have an important impact on conservation strategies for reef sharks and other endangered shark species. Since reef sharks use a variety of different habitats (both shallow and deeper water areas), creating an interconnected conservation network is vital for ensuring full protection throughout their life cycle. Sanctuaries such as the Yarari Sanctuary (which includes the marine area around the Caribbean Netherlands) are an important step in creating a network of protected areas. In addition, efforts such as the Caribbean Shark Coalition are important as well, because they work to build capacity for shark and ray research, policy and conservation within the Wider Caribbean Region.

Report your sightings

You can help contribute to the overall understanding of sharks and other species by reporting your nature sightings on sightings and photos on DutchCaribbean.Observation.org or download the free apps (iPhone (iObs) & Android (ObsMapp)).

Species reports by local communities and tourists are invaluable for nature conservation efforts to help increase public awareness and overall species protection.

DCNA, Observation International and Naturalis Biodiversity Center are working together to develop on automated species identification app for your phone for all species on land and in sea. Your uploaded photos are of great value to make this possible. For questions, please contact research@DCNAnature.org

More information

For more information, please find the full report here or follow along on the DCNA’s free digital newsletter BioNews for the latest updates. For questions related to the reef shark study, please contact twan.stoffers@wur.nl

 

Article published in BioNews 45 and Special Edition BioNews: Tiger Shark Expedition

 

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Saba
Saba bank
St. Eustatius
Author

Expedition on the Saba Bank to Enhance Tiger Shark Protection

Starting August 1, 2021 a team of researchers will spend a week on the Saba Bank investigating the life-cycle of tiger sharks. Researchers will investigate the migration routes, where and when tiger sharks breed so they can protect them better within the Dutch Caribbean’s Yarari Marine Mammal and Shark Sanctuary as well as beyond. In this expedition members from the Saba Conservation Foundation (SCF)Nature Foundation St. Maarten (NFSXM), St. Eustatius National Parks (STENAPA)STINAPA Bonaire, the Aruba National Parks Foundation (FPNA), the Dutch Caribbean Nature Alliance (DCNA) and World Wildlife Fund for Nature the Netherlands (WWF-NL) will participate.

© Sami Kattan

In 2016, the Saba Conservation Foundation, Nature Foundation St. Maarten, and Sharks for Kids  partnered together as part of DCNA’s Save our Sharks Project funded by the Dutch National Postcode Lottery. Since then, satellite tagging of tiger sharks has been conducted on the Saba Bank and around Sint Maarten. Through this research we now know that tiger sharks in Dutch waters travel throughout the Caribbean basin, with most of these tagged sharks being sexually mature females. During the upcoming expedition the researchers aim to not only tag and track more tiger sharks to further investigate the life cycle, but they will also measure if and how large the pups inside pregnant tiger sharks are. This will help to determine if the Saba Bank is in fact a breeding ground for tiger sharks, one of the main goals of the expedition.

Tiger Shark. © Jarrett Corke WWF-Canada

The other objective is to see where these transboundary sharks migrate to in order to better understand the importance of the Yarari Marine Mammal and Shark Sanctuary and protect other geographical areas. The Yarari Sanctuary was established on September 1, 2015 and aims to protect marine mammals, sharks, and rays throughout the waters of Bonaire, Saba, and since September 2018, St. Eustatius. Collaboration between not only the six Dutch Caribbean islands but countries across the wider Caribbean as a whole is necessary in order to protect and conserve these essential species and ecosystems. Therefore the Caribbean Shark Coalition was recently formed to collaborate better in the entire Greater Caribbean region.

Celebrated on July 28 each year, World Nature Conservation Day acknowledges that a healthy environment is the foundation for a stable and healthy society. This includes a healthy ocean which, undoubtedly, depends on sharks. Sharks are large top predators that serve a critical role in maintaining balance in the marine ecosystem. Sharks help keep their prey population healthy by eating the weak while also affecting their prey’s distribution. In healthy oceans, sharks help to maintain stable fish stocks and healthy coral reefs and seagrass beds, which is important for the fisheries and the economy of the islands.

The Tiger Shark research expedition is coordinated by the DCNA and generously funded by WWF-NL through the Biodiversity Funds and the Dutch National Postcode Lottery. For more information on the Pregnant Tiger Shark Expedition, follow the participating organizations on Facebook, Instagram or DCNA’s website(https://dcnanature.org/news/).

 

Article published in BioNews 45 and Special Edition BioNews: Tiger Shark Expedition

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Saba
Saba bank
Author

Sababank: onderzoek 2011 -2016

1. Inleiding

Dit boek neemt u mee in de bijzondere onderwaterwereld van de Saba Bank. Tegelijkertijd geven we u een overzicht van de resultaten uit verschillende onderzoeksprojecten uitgevoerd tussen 2011 en 2016, gepresenteerd tijdens het Saba Bank Symposium (Den Helder, 8 december 2016)

Date
2016
Data type
Media
Theme
Research and monitoring
Tags
Geographic location
Saba bank

Status and trends in Saba Bank fisheries: Analysis of fisheries data collected over the period 2011-2020

This report is an update of earlier published reports on the status and trends in the of Saba Bank fisheries (Graaf et al. 2017, Brunel et al. 2018). The new analyses presented here are based on three additional years (2018-2020) of data collected by the Saba Bank Management Unit.

Lobster fishery

After a period of increase from 2012 to 2015, fishing effort in the lobster fishery (Panulirus argus), has gradually declined in subsequent years, with nearly a halving of the effort between 2015 and 2020. The resulting landings of lobster have shown a similar pattern with an increase up to 2015 when they amounted to 78t, and, after a period of relative stability in 2016-2017, showed a marked decline to 27t in 2018, before partial recovery in 2019 and 2020. Increasing landings per unit effort (number per trip) indicate that the formerly reduced lobster abundance, which had been declining since 2000 and which reached its lowest level in 2011, has subsequently increased relatively steadily all through 2020, back to levels close to those of 2007. Length based proxies for exploitation level with respect to MSY suggest that there has been overfishing of the stock (F/FMSY >1) for all the period covered by the data, and the mean size of the lobsters landed has been decreasing over the last 5 years.

 

Lobster fishery fish bycatch

Mixed landings of reef fish in the lobster fishery have fluctuated between 7 and 15t annually. The biomass index derived from the LPUE of these bycatch species also shows a decrease of about 35% from high levels in 2000 and 2007 to lowest levels in 2011. After a partial recovery from 2011 to 2013, the biomass declined slowly until 2018, and then rose sharply in 2019. Among the three main species landed, two - the Queen triggerfish, Balistes vetula, and the white grunt, Haemulon album,- are being overfished according to length-based indicators while the Red hind, Epinephelus guttatus, is being fully exploited (F/FMSY close to 1). Red fish trap fishery The figure below gives a summary of the trends in the red fish trap fishery, which principally targets a mix of deep water snappers such as the Silk snapper, Lutjanus vivanus, the Vermillion snapper, Rhomboplites aurorubens, the Blackfin snapper, Lutjanus buccanella and the Lane snapper, Lutjanus synagris. In the redfish trap fishery (Lutjanidae), the number of trips has grown from 335 to 566 (corresponding to 10 000 and 13 400 traps set respectively) during the period 2012 to 2016 but dropped considerably to 271 trips in 2017 (5 600 traps). In the last three years, the effort increased again to reach nearly 600 trips in 2020 (16 000 traps), the highest effort for the whole period considered. The landings of redfish (mainly silk snapper and in smaller proportions blackfin and vermillion snapper) broadly followed the variation of the effort, with the highest estimates (>50t) for the last two years, recovering from a low value in 2017 (25t). This drop in snapper landings and effort in 2017 is the consequence of a 6- month closed season voluntarily implemented by the fishermen that year (Graaf et al. 2017).

The biomass index derived from the LPUEs shows a decrease of 50% between 2007 and 2011, followed by a steady increase until 2019 and a sharp decrease in 2020. Length-based indicators for fishing mortality indicate that silk snapper and vermillion snapper have been heavily overfished, with a ratio F/FMSY higher than 1.3. For the other two snapper species (but also for the vermilion snapper in the most recent years), the length composition data is scarce which results in a large uncertainty. Nevertheless, the F/FMSY proxy also suggests that these two stocks are subject to overfishing although this is less pronounced than for the two principal species.

 

Other fishing métiers

Bottom drop longline, pelagic and bycatch landings have remained much less important and have shown no significant new developments

Overall conclusion

For both the targeted lobster and “redfish” stocks, the LPUE based indices indicate that stock size overall increased since the beginning of the current port sampling program (2011), when they were at a lower level. In this report, length-based indicators of fishing mortality levels are presented for the first time. This provides new insights on the exploitation status of the stocks. These indicators suggest that, despite the overall increase in stock size, the stocks are subject to overfishing, slightly for the lobsters, but more severely for the redfish. With the current declining trend in effort for the lobster fishery, it can be expected that the fishing mortality is declining. It is important to continue monitoring the fishery (and particularly length measurements of the landings) to see if the length-based indicator will reflect such a decline in fishing mortality in coming years. The situation is more worrying for the redfish fishery for which the recent trend is an increase in the fishing effort. This, combined with the indication that the fishing mortality of these stocks has been well above FMSY, suggest that management action is needed to bring the fishing mortality to lower levels. Again, continued monitoring of the fishery is essential, as well as improved biological sampling and reporting of the catches. The current ability to accurately estimate the status of individual redfish species is limited by the fact that the fisheries data is not reported by species. Being able to split the landings per species, either by encouraging the fishers to report landings per species, or by increasing the intensity of biological sampling, would, on the long term, provide a better basis to manage the “redfish” snapper stocks. The present study further suggests that three key finfish species, which are mainly landed as bycatch from the lobster fishery, are either being overfished (Queen triggerfish and White grunt) or are at the verge of being overfished (Red hind). The Queen triggerfish and Red hind formerly were common in the landings in the Dutch Caribbean but now still only have significant populations on the Saba Bank. Therefore, both of these species require a cautionary management approach as well.

Date
2021
Data type
Research report
Theme
Research and monitoring
Report number
Wageningen University & Research report C062/21
Geographic location
Saba bank

Dissolution of a submarine carbonate platform by a submerged lake of acidic seawater

Abstract.

Submarine sinkholes are found on carbonate platforms around the world. They are thought to form and grow when 15 groundwater interactions generate conditions corrosive to carbonate minerals. Because their morphology can restrict mixing and water exchange, the effects of biogeochemical processes can accumulate such that the sinkhole water properties considerably diverge from the surrounding ocean. Studies of sinkhole waters can therefore reveal new insights into marine biogeochemical cycles, thus sinkholes can be considered as ‘natural laboratories’ where the response of marine ecosystems to environmental variations can be investigated. We conducted the first measurements in recently discovered sinkholes on 20 Luymes Bank, part of Saba Bank in the Caribbean Netherlands. Our measurements revealed a plume of gas bubbles rising from the seafloor in one of the sinkholes, which contained a constrained body of dense, low-oxygen ([O2] = 60.2 ± 2.6 μmol·kg−1), acidic (pHT = 6.24 ± 0.01) seawater that we term the ‘acid lake’. Here, we investigate the physical and biogeochemical processes that gave rise to and sustain the acid lake, the chemistry of which is dominated by the bubble plume. We determine the provenance and fate of the acid lake’s waters, which we deduce must be continuously flowing 25 through. We show that the acid lake is actively dissolving the carbonate platform, so the bubble plume may provide a novel mechanism for submarine sinkhole formation and growth. It is likely that the bubble plume is ephemeral and that other currently non-acidic sinkholes on Luymes Bank have previously experienced ‘acid lake’ phases. Conditions within the acid lake are too extreme to represent coming environmental change on human timescales but in some respects reflect the bulk ocean billions of years ago. Other Luymes Bank sinkholes host conditions analogous to projections for the end of the 21st 30 century and could provide a venue for studies on the impacts of anthropogenic CO2 uptake by the ocean.

Date
2021
Data type
Scientific article
Theme
Research and monitoring
Document
Journal
Geographic location
Saba
Saba bank

Update on the 2016-2017 catch trends in the Saba Bank fisheries

The recent status and trends in the Saba Bank fisheries up to and including 2015 port sampling data have been previously reported by de Graaf et al. (2017) and a policy brief has also been written based on those results (Debrot and de Graaf (2018). The purpose of this report is to update recent catch trends in the Saba Bank fisheries with the data from 2016 and 2017.

For the lobster fishery (Panulirus argus), the number of fishing trips (and number of traps set) gradually grew from 2012 to 2015 but has since leveled off. The resulting landings of lobster have shown a similar pattern of increase up to 2015 but have now leveled off at around 70 tons annually. Increasing landings per unit effort indicate that the formerly reduced lobster abundance, which had been declining since 2000 and which had reached its lowest level in 2011, has subsequently increased relatively steadily all through 2017, and now has increased back to levels close to those of 2007. The average size of lobsters taken, continues to be large, which is favourable to gradual stock recovery.

Mixed landings of reef fish in the lobster fishery have fluctuated between 10 and 20 tons annually. The LPUE abundance index in bycatch species also shows a decrease of about 35% from high levels in 2000 and 2007 to lowest levels in 2011, followed by an increase up to 2013, after which landings have levelled off.

In the redfish trap fishery (Lutjanus spp.), the number of trips in the redfish trap fisheries had grown significantly during the period 2012 to 2015. In 2016 effort increased again to 625 trips. In 2017 the exerted fishing effort dropped down to about 350 trips, a level seen last in 2012. The landings of redfish have fluctuated over this period, with lower values in 2012 and 2017 and higher values in 2014 and 2016. The LPUE abundance index shows a decrease by 50% between 2007 and 2011, followed by an increase to slightly higher and constant values between 2012 and 2016, while in 2017 the LPUE abundance index continued increasing. The only snapper for which sufficient data was available, was the silk snapper, Lutjanus vivanus. Average size of the silk snappers landed continued its increasing trend, indicative of gradual stock recovery. The drop in snapper landings, despite the higher LPUE in 2017, can especially be ascribed to the 6-month closed season implemented that year (Graaf et al. 2017).

The overall conclusion is that for both the lobster and redfish stocks, stock status, based on the LPUE index and size-structure trends have continued in developing favorably. Bottom drop longline, pelagic and bycatch landings have remained much less important and have shown no significant new developments.

There are two matters of concern that require follow up. Firstly, the positive prognosis for the snapper “stock” status may partly be based on targeting geographically different stocks as well as different species. Hence the data as collected and analyzed may actually be presenting a too optimistic assessment. To evaluate whether this is actually the case will require more detailed analysis based on individual species, as well as more accurate geographical recording of catches than as currently practiced. The second matter of concern regards the fate of the traps that were in the water on the Bank when the hurricanes Irma and Maria struck the area in September 2017. If trap loss was large, this may lead to higher detrimental impacts of ghost fishing in the coming years.

Date
2018
Data type
Research report
Theme
Research and monitoring
Report number
C083/18
Geographic location
Saba bank

Saba Bank video documentary

Video documentary describing the importance of the Saba Bank as a natural resource for the island of Saba, including underwater footage and interviews with fishermen and managers.

Date
2017
Data type
Media
Theme
Education and outreach
Geographic location
Saba bank
Author
Image

Changing benthic communities on Saba Bank Is Saba Bank becoming a ‘Sponge reef’?

Abstract - Due to multiple stressors, many coral reefs are degrading. Shifts from a coral
dominated system to an alternate phase are observed. For coral reefs, the shift described most
in the scientific literature is a shift to an algae dominated system. However, shifts to other
dominant species are observed as well, including sponge or cyanobacteria dominance. It is
thought that sponges may become dominant when macroalgae or turf algae cover increases.
Algae are producers of dissolved organic matter (DOM), a food source for sponges.
Cyanobacteria are producers of DOM as well, although it remains unclear whether sponges
can use this. Furthermore, the decrease in spongivore fish due to overfishing, and the increase
in picoplankton can result in increasing sponge cover. In this study, benthic cover of eleven
sites at Saba Bank in 2013 and 2015 is assessed. Corals and sponges were identified to species
level, to get insight into assemblages. Using the program CPCe, photo quadrats (N=10) of two
transects per site were analyzed. The same photo quadrats were used for analysis of sponge
diversity, all sponges larger than 4 cm were identified to species level. Last, in 2015 92
specimens of sponges were sampled and identified using DNA barcoding and morphological
analysis. Close-up photos of these specimens were made, so that sponge identification guide
of Saba Bank can be developed. A shift from turf algae dominance to cyanobacterial
dominance among the years 2013 and 2015 was observed. Possibly, Saba Bank experiences
some influence from the nearby islands Saba, St. Eustatius, and St. Kitts and Nevis.
Macroalgae cover was found to be higher in the northern and northeastern parts of the bank
(closer to the islands), whereas coral cover was lower in these parts. The coral with highest
cover in the benthic survey was Montastraea faveolata (34.7% and 45.5% of total coral cover
in 2013 and 2015). Using multivariate analysis, year and water depth had a significant effect
on coral composition, position of the site had no significant effect suggesting connectivity
between sites for corals. The species Xestospongia muta and Agelas sventres contributed most
to total sponge cover (X. muta: 11% and 12.9%; A. sventres: 10.4% and 15.4% of total sponge
cover in 2013 and 2015). Water depth, northing and non living cover had a significant effect
on sponge composition. Altogether, sponge cover was not high on Saba Bank and therefore it
is not (yet) becoming a sponge reef. In 2015, Saba Bank was dominated by cyanobacteria, this
may be beneficial to sponges, since cyanobacteria are producers of DOM.

Date
2016
Data type
Other resources
Theme
Education and outreach
Research and monitoring
Geographic location
Saba bank

BioNews 1-2017 Dutch Caribbean Newsletter

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:

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.

Date
2017
Data type
Media
Theme
Research and monitoring
Geographic location
Saba bank