st. Eustatius

Ten-year assessment of Caribbean Netherlands fisheries monitoring: data challenges and recommendations

Summary

Over the last 10 years, the Caribbean Netherlands fisheries on Saba and St. Eustatius have been monitored and multiple assessment reports have been made by Wageningen Marine Research (WMR) in collaboration with local Data Monitoring Officers (DMOs). However, due to challenges in collecting the necessary data, there are gaps in the data which can lead to large uncertainties in the current stock assessments and make it difficult to deliver a more detailed assessment of the fisheries and the state of the stocks.

The specific objectives of this report were to present the data challenges and provide recommendations to address the shortcomings in the current data collection. By addressing these and providing solutions, improvements of the Caribbean Netherlands fisheries monitoring program can be made.

The main gaps identified in the data are:

- Limited coverage by the logbook data, especially the case in St. Eustatius. This implies that large raising factors are applied when estimating total effort and landing estimates, which leads to more uncertain estimates.

- Landings not reported by species (at least for the main species) and port sampling for species composition not frequent enough to be able to produce landing estimates and abundance indices at the species level (instead of species groups). For instance in Saba, the number of trips sampled to estimate the length-composition of the landings was on average 60 per year (excluding 2011), with mainly lobster and redfish trips being sampled. On average, around 40 trips per year were sampled for species composition, taken representatively from the different fishing methods. This is less than one catch sampled per week. This is too low and needs to be intensified if data availability and quality are to improve.

- While some species are over-sampled for length-composition, others are not sampled enough to be able to compute reliable length-based indicators.

 

Our key recommendations are:

o Port sampling and biological data collection-frequency must be stepped up to meet minimum targets.

o Going along with fishers on the vessels, in order to measure catches on location. (Then fishermen won’t have to wait at the harbor for the DMOs work to be done.)

o Facilitate working in morning/midday/evening shifts. This enables data collection after regular working hours, e.g. when fishers come home late in the day (5-6pm).

o Set quantitative targets for data collection. We suggest targeting for a minimum of 70% logbook declarations, activity surveys, catch species composition and weight data (tonnes), while doubling the effort on selected species of importance

o Data collection will now need to include exact biometric data to establish length-weight and fecundity curves, sex ratios and reproductive seasons for individual species, as well as the collection of otoliths from a range of sizes for each species as a basis for age and growth studies by the WMR otolith lab.

o Have DMOs sit in a workspace with a clear view of the harbor where fishers arrive with their catches, so they can immediately act when boats arrive with their catches. This is mainly an issue for the St. Eustatius DMO.

o For bycatch measurements photographing the fish on a cm grid surface can save measuring time in port or on vessels. o Increase willingness of fishers to participate in data collection. o Incentivize fishers to participate by organizing regular (bimonthly or quarterly) gettogethers where the DMOs update fishers on some monitoring results, providing snacks and drinks.

o Provide dedicated freezer storage space for fishers at the harbor, enabling DMOs more time for the port sampling. Fishers willingness to wait for port sampling is understandably limited. By providing dedicated freezer storage facility, the DMOs can take extra time needed for sufficient biological sampling (i.e. species composition, length, sex) while the catch of the fishers stays fresh. The same can be done for lobster catches if a port-based holding area is provided. 

o Provide modern technologies to the fishers and/or DMOs, e.g. Electronic Reporting Systems (ERS) such as electronic logbooks, and GPS systems such as the Vessel Monitoring System (VMS).

o Arrange for closer involvement of WMR in work planning for the island DMO’s

Date
2022
Data type
Research report
Theme
Research and monitoring
Report number
C053/22
Geographic location
Bonaire
Saba
Saba bank
St. Eustatius

Using Satellite Imagery to Map St. Eustatius Coralita Invasion

Coralita is an invasive plant species, rapidly spreading across St. Eustatius.  A recently published report highlighted the ability to use satellite imagery to systematically map Coralita’s distribution over the island.  The approach could provide key insights into how habitat and vegetation are changing over time to aid in conservationists’ efforts to minimize the negative effects of Coralita and similar invasive species.

Coralita overgrowth (Source: Achsah Mitchell)

Coralita is a fast-growing, climbing vine with beautiful pink or white flowers. Originally from Mexico, Antigonon leptopus started out as a popular garden plant, but has expanded its territory and is now aggressively invading natural areas. Its fast-growing nature means it can outcompete most native species for terrain, quickly making it the dominant species, and reducing overall diversity. This is especially the case on St. Eustatius, where ground surveys indicate the plant already appears on 15-33% of the island.

Mapping Techniques

One of the biggest issues in controlling invasive species is accurately accounting for its presence, particularly if data needs to be collected over a wide area. This is where satellite imagery can help by providing an affordable, high spatial resolution option. A new collaborative study from the Utrecht University, University of Zurich, Wageningen University, and the Technical University of Braunschweig provided key insight by using such satellite imagery to identify Coralita. The method is successful, as areas dominated by Coralita emit a relatively distinct electromagnetic signal that can be detected by satellites. Once the distribution of Coralita has been mapped using this technique, it is possible to identify the environmental conditions associated with Coralita’s presence. This approach provides a relatively low-cost solution that is powerful, accurate and repeatable; key in identifying and monitoring its spread in the future.

“In creating this map,” said Elizabeth Haber, first author of this study, “it was my hope to produce something that could be useful for those who are caring for and protecting the incredibly special nature on Statia.”

Results

Using this method, researchers sampled 162 locations across St. Eustatius and estimated that Coralita was the dominant canopy cover (>50%) on over 3% of the island (64 ha). Perhaps more importantly, this map also showed that Coralita was not randomly distributed but generally found, for example, in areas of water accumulation, near roads or near drainage channels. Furthermore, Coralita was often found in grasslands and areas of development and is relatively rare in natural forests, highlighting how human disturbances can promote the spread of Coralita. It is important to note that data filtering and physical limitations of using satellite imagery means that Coralita growing under trees or shrubs or in smaller patches is likely underrepresented in this study.

Map of the distribution of Coralita on St. Eustatius (Haber et al., 2021)

 

Conservation Implications

Even with the physical limitations, the fact that this study is cost effective and repeatable means that consistent comparisons of Coralita’s distribution can be made over time. These comparisons are vital in understanding how populations and habitats are shifting, granting conservationists a fantastic tool in forecasting the spread of invasive species. Arguably the greatest asset of the Caribbean is its vast biodiversity. Already threats of climate change, habitat loss, invasive species and urban development are upsetting this fragile balance. St. Eustatius, although small, is home to several endemic plant species, two of which are the Statia morning glory and Statia milkweed, along with the critically endangered Lesser Antillean Iguana which could all be threatened by the habitat alterations of Coralita growth.

To read more, please find the full report on the Dutch Caribbean Biodiversity Database using the link below.

https://www.dcbd.nl/document/high-spatial-resolution-mapping-identifies-...

 

Article published in BioNews 48

 

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

Feasibility study of a new harbour on the island of St. Eustatius

St. Eustatius is a small island in the Caribbean that belongs to the Kingdom of the Netherlands. Its existing harbour is due for upgrades and repairs on existing structures have been discussed in addition to the possibility of constructing a new harbour. The island is rugged, and the landward side of the coast is surrounded by cliffs except for a small stretch of coast where the hinterland is quite flat.

The island is not self­sufficient and all cargo comes in via the existing harbour. These cargo flows coming from the harbour are transported through the touristic centre of the island making for some unpleasant and dangerous situations. Additionally, the harbour is mostly used by large cargo vessels and leaves no room for leisure ships. The government of the island sees the potential to attract more tourists, but is also aware that the current state of the facilities could be improved. The objective of this Master’s thesis is to explore the feasibility of constructing a new harbour on the west coast of St. Eustatius and to find a suitable layout and a conceptual design for a new harbour. This will be done following the regular design approach in which the design steps are conceptualisation, verification, evaluation and selection. The location of the new harbour has already been determined in earlier research and is shown in Figure 1. The location is chosen where the hinterland is quite flat.

The conceptualisation starts with gathering relevant information about the requirements and boundary conditions of the project. The future cargo volumes and future vessel dimensions are estimated on which the dimensions of the required facilities of the harbour are based. These cargo volumes are determined with growth of population, welfare and the tourism sector in mind. Environmental conditions and hydrodynamic conditions of the proposed project location are also gathered. Data includes information of topography, bathymetry, soil characteristics, archaeological remains, environmental and aviation regulations and also data about waves, wind, currents and water levels. Here, it is found that the off­shore wave heights during hurricane conditions are quite significant but break on the foreshore and subsequently lose energy. On the contrary, the daily wave climate is relatively calm. It is confirmed by the gathered data that the location of the new harbour has potential for construction since the hinterland is relatively flat and is located out of the zones of important nature parks. However, it is expected that significant amounts of historic remains are found in the area which need to be removed before construction. For future design steps it is advised to gather more accurate data.

The government of St. Eustatius is the client and has some clear wishes and demands. First and foremost, the harbour should be built in phases. The first phase would account for the current and future cargo volumes to the island. The second phase would be the expansion of the harbour to function as a transshipment hub and develop as a competitor to the congested harbour of St. Maarten. This way, the funding of the expansion can partly come from the operational profits of the harbour. The necessary buildings and facilities, including their dimensions, have been found in conversations with the client and through calculations. The required wet areas of the port and the elevation levels were found based on the dimensions of the design vessel. The road leading to the new harbour will be constructed on the already existing dirt road which needs upgrading.

In the development of the harbour layouts three alternatives have been developed. These are developed with the small scale of the harbour in mind which lead to the choice of discarding a northern breakwater. This choice is justified since the data showed that the waves during daily conditions almost solely come from the south. The turning circle has been moved out of the harbour basin too to save space which is justified based on the limited amounts of movement. The alternatives differ in their orientation of the berth and the usage of the breakwater as a berth. The conceptualisation step is finished by discussing the modifications on these alternatives. A shift of the harbour landwards, placement of the storage on land or water and a combination of both is considered.

The verification of these layout alternatives is done by analysing the possibility of constructing a breakwater, the impact on the morphology of the island and studying the wave penetration of the harbour basin of every alternative.

The breakwater of the different alternatives is situated at different water depths which makes for the design under different conditions. For the design of the breakwater two types, rubble mound and caisson, are considered, that have (dis)advantages under certain circumstances. It needs to be verified that a design for both types of breakwater can be designed for the different water depths. It turns out that the waves at the deeper location are too large to be able to construct a rubble mound breakwater there. In some alternatives, the use of a caisson breakwater could not be verified as a result of the small water depth. This is a result of the economic disadvantage of a caisson breakwater at such a shallow depth. These designs are subsequently dropped from the analysis.

The harbour should not have a negative influence on the morphology of the island and the sediment transport should not have a negative impact on the construction and operation of the harbour. The west coast of the island experiences very minor sediment transport in the northern direction as a result of lack of sediment availability in the surf zone. It is found that the construction of the harbour does influence the coastline in a positive way as the breakwater is able to capture the limited available sediment. The harbour would be an excellent contribution in combination with beach nourishment since the historic structures on the coastline are once again protected.

The last topic of the verification step treats the wave penetration into the harbour basin. Here, the wave direction has been divided into three main wave directions. The wave penetration has been determined on a basis of refraction and diffraction diagrams and the wave height at the berths has been calculated. The downtime of every alternative per wave direction showed to be on the high side after the comparison with allowable wave heights. The designs have been altered by means of an elongation of the breakwater to create calmer conditions and lower the downtime to be under the 1.1%. This was not possible in one alternative where the safety of navigation would be diminished and this alternative has been discarded. The harbour oscillations as a result of resonance of long ocean waves is also investigated. Here, the measured waves in the existing harbour are investigated and compared to the natural periods of the alternative layouts. Even though the natural periods of the harbour concepts are situated further from the measured period of the waves in the existing harbour, there still is a chance resonance will occur. More investigation into this subject is advised in more detailed design steps.

The final step in this analysis is the evaluation and selection of the most suitable alternative. This has been done by a multi criteria analysis in which weighted scores have been determined. The ratio between the costs and the weighted score of every alternative would result in a most suitable alternative which can be seen in Figure 3. This design is partly dug in into the land and is executed with a rubble mound breakwater. It might be possible to gather the required material from the island but it is highly likely that these need to be imported.

The price of this design, excluding the construction of the harbour buildings and the road, is estimated to be in the order of $35 million (±50%) and is very much influenced by the costs of the breakwater. The cross­section of the breakwater of the final design can be found in Figure 4.

This Master’s thesis is a first step for the exploration into the possibilities regarding the construction of a new harbour on the island of St. Eustatius. Therefore, the availability of data has not always been guaranteed and resulted in the need to estimate, or assume, necessary information. It is advised, in following design steps, to gather more accurate data by performing measurements and real­life experiments. The level of accuracy of the data should match the advance of the detail of design. Specifically, the structure of the subsoil and the wave behaviour should be investigated more thoroughly. Scale model tests and on­site measurements are part of this additional gathering of information and verification. Conclusions from further research might alter the design.

Date
2022
Data type
Research report
Theme
Research and monitoring
Report number
Master Thesis
Geographic location
St. Eustatius

High peak settlement of Diadema antillarum on different artificial collectors in the Eastern Caribbean

The massive die-off of the herbivorous sea urchin Diadema antillarum in 1983 and 1984 resulted in phase shifts on Caribbean coral reefs, where macroalgae replaced coral as the most dominant benthic group. Since then, D. antillarum recovery has been slow to non-existent on most reefs. Studying settlement rates can provide insight into the mechanisms constraining the recovery of D. antillarum, while efficient settlement collectors can be used to identify locations with high settlement rates and to collect settlers for restoration practices. The aim of this study was to compare pre and post die-off settlement rates and to determine possible settlement peaks in the Eastern Caribbean island of St. Eustatius. Additionally, we aimed to determine the effectiveness and reproducibility of five different settlement collectors for D. antillarum. D. antillarum settlement around St. Eustatius was highest in May, June and August and low during the rest of the study. Before the die-off, settlement recorded for Curaçao was high throughout the year and was characterized by multiple settlement peaks. Even though peak settlement rates in this study were in the same order of magnitude as in Curaçao before the die-off, overall yearly settlement rates around St. Eustatius were still lower. As no juvenile or adult D. antillarum were observed on the reefs around the settlement collectors, it is likely that other factors are hindering the recovery of the island's D. antillarum populations. Of all five materials tested, bio ball collectors were the most effective and reproducible method to monitor D. antillarum settlement. Panels yielded the least numbers of settlers, which can partly be explained by their position close to the seabed. Settler collection was higher in mid-water layers compared to close to the bottom and maximized when strings of bio balls were used instead of clumps. We recommend research into the feasibility of aiding D. antillarum recovery by providing suitable settlement substrate during the peak of the settlement season and adequate shelter to increase post-settlement survival of settlers. The bio ball collectors could serve as a suitable settlement substrate for this new approach of assisted natural recovery.

Date
2022
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Geographic location
St. Eustatius

Hurricane-induced population decrease in a Critically Endangered long-lived reptile

ABSTRACT

Catastrophic events, like hurricanes, bring lethal conditions that can have population-altering effects. The threatened Caribbean dry forest occurs in a region known for its high-intensity hurricane seasons and high species endemism, highlighting the necessity to better understand hurricane impacts as fragmentation and clearing of natural habitat continues. However, such studies remain rare, and for reptiles are mostly restricted to Anolis. Here we used single-season occupancy modeling to infer the impact of the intense 2017 Atlantic hurricane season on the critically endangered Lesser Antillean Iguana, Iguana delicatissima. We surveyed 30 transects across eight habitats on St. Eustatius during 2017-2019, which resulted in 344 individual surveys and 98 iguana observations. Analyses of abundance and site occupancy indicated both measures for 2018 and 2019 were strongly reduced compared to the pre-hurricane 2017 state. Iguanas at higher elevations were affected more profoundly, likely due to higher wind speeds, tree damage and extensive defoliation. Overall, our results indicate a decrease in population estimates (23.3-26.5%) and abundance (22-23.8%) for 2018 and 2019, and a 75% reduction in the number of opportunistic sightings of tagged iguanas between 2017-2018. As only small and isolated I. delicatissima populations remain, our study further demonstrates their vulnerability to stochastic events. Considering the frequency and intensity of hurricanes are projected to increase, our results stress the urgent need for population-increasing conservation actions in order to secure the long-term survival of I. delicatissima throughout its range.

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Journal
Geographic location
St. Eustatius

Find me if you can: Pre- and Post-hurricane Densities of the Red-bellied Racer (Alsophis rufiventris) on St. Eustatius, and a review of the genus in the Caribbean

Abstract

We estimated population densities of the red-bellied racer (Alsophis rufiventris) on the Caribbean island of St. Eustatius in 2011, 2018 and 2019 to determine the likely influence of hurricanes Irma and Maria (September 2017), in addition to evaluating abiotic parameters which may be correlated with its presence. Surveys were conducted at seven sites in 2011 prior to the hurricanes, and at 81 and 108 sites in 2018 and 2019 respectively posterior to the hurricanes. A total of 8.2 ha was surveyed in 2011, and 11.42 ha in 2018/2019. The pre-hurricane (2011) racer density estimate was 9.2/ha (min 7.3 - max 11.6); post-hurricane estimates were 4.6/ha (min 3.4 - max 6.0) in 2018 and 5.0/ha (min 3.8 - max 6.5) in 2019. The pre-hurricane encounter rate of individual racers was 16.0 snakes/hour compared to 0.34 snakes/hour in 2018 and 0.41 snakes/hour in 2019 (post-hurricane). The decrease in encounter rates between 2011 and 2019 implies a negative impact of the hurricanes on racer abundance. Based on calculations of detection probability (0.02 in 2018 and 0.03 in 2019), post-hurricane lambda estimates were 1.82 (95% CI 0.66 - 5.01) in 2018 and 1.60 (95% CI 0.39 - 6.65) snakes/ha in 2019. Given the current small size of the remaining population and the presence of invasive species across the snake’s range, this species could be at risk of local extirpation. We suggest conservation actions such as invasive species management and habitat restoration to enable further recovery.

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Journal
Geographic location
St. Eustatius

Tropische natuur in Nederland

In oktober 2010 kregen Sint Eustatius, Bonaire en Saba de status van bijzondere Nederlandse gemeente. Dit houdt in dat Nederland de medeverantwoordelijkheid moet nemen voor de bescherming van een aantal unieke tropische natuurgebieden. Zo ook op Statia, zoals Sint Eustatius in de volksmond wordt genoemd.

 

Date
2012
Data type
Media
Theme
Research and monitoring
Geographic location
St. Eustatius
Image

Plants and Lichens of St. Eustatius. A Virtual Herbarium of the New York Botanical Garden

St. Eustatius, also informally known as "Statia" is an 11.8 square mile (30.6 square km) island with about 3,200 permanent inhabitants located off the coast of St. Maarten (go to map from link in banner). English is the official language of the island but Dutch is also taught in schools and is spoken by many Statians.

In January 2008, The New York Botanical Garden, in partnership with the St. Eustatius National Parks Foundation (STENAPA), the Department of Environment and Nature (MINA) of the Netherlands Antilles, and Conservation International, embarked on a project to survey the plants and lichens of Statia. (See photobook from the expedition.)

Although relatively small in size, Statia's topography is covered by several vegetation types with a variety of soil types, ranging from beach forest at sea level to elfin forest on the summit of The Quill, a dormant volcano, at some 600 m elevation. Our goal is to provide illustrated checklists (a virtual museum) of all of the plants and lichens that grow on Statia. Both native and introduced species are included.

To find collections representing species of flowering plants, gymnosperms, ferns, bryophytes, or lichens, you can access the information available for a given group by clicking on the appropriate image on the left hand side of this page.

It is forbidden to pick plants and to remove plants from the island of Statia. All natural history studies must first be approved by the government of The Netherlands. To find out how to obtain permission to collect herbarium specimens, as was done in this study, contact STENAPA. All photographs are copyrighted by the photographer, Carol Gracie, unless otherwise noted. For permission to use the images, contact the photographers. Citizens of Statia have permission to download images from the website for personal or educational purposes.

Date
2009
Data type
Portal
Theme
Research and monitoring
Geographic location
St. Eustatius
Image
Plants and Lichens of St. Eustatius

Caribbean - GCRMN Coral Reef Monitoring started in St. Eustatius

Brief description of the recently started (Feb 2015) coral reef monitoring program in St. Eustatius using the guidelines agreed upon by the Caribbean (Global) Coral Reef Monitoring Network (Caribbean – GCRMN). 

Date
2015
Data type
Other resources
Theme
Research and monitoring
Geographic location
St. Eustatius

Climate Change Predictions for St-Eustatius and its possible impacts on the island

This report was created to highlight the most important climate change predictions for St. Eustatius and to highlight possible impacts on the island.

St. Eustatius (Statia) is a Caribbean island near St. Kitts and Nevis, St. Maarten and Saba. St. Eustatius has a surface of 21 square kilometres and forms part of the Dutch Caribbean. On 10-10-10 it became a special municipality of The Netherlands, together with Saba and Bonaire (together they form the BES-islands).

St. Eustatius is important for its marine and terrestrial species, some of which are endemic and/or endangered. Some examples of this include Iguana delicatissima and the newly-described endemic, Gonolobus aloiensis. However, because of the island’s small size, it is likely that climate change will threaten these species. Climate change will have different impacts on St. Eustatius.

Since 2010, the population on St. Eustatius has increased. On 01-01-2010 there were 3583 people living on St. Eustatius, but on 01-01-2014 this number grew to 4020. That is an increase of 437 people (12% compared to 01-01-2010) in just four years. Also 36% (714 persons) of the working population on St. Eustatius is working in the trade, transport or catering industry. And 31% (609 persons) is working in the government branch.

If we look at the coastal protection of St. Eustatius, than it is clear that this s predominantly natural, except for the protection near NuStar, the harbour and in Oranjestad Bay, which are man-made. This is also one of the reasons why most of the island is vulnerable to erosion, because there is no protection.

The nature on St. Eustatius has many strengths, weaknesses, opportunities and threats (SWOT).The most important strengths are good maintenance of the national parks, high biodiversity and the presence of marine and terrestrial protected areas. There are also opportunities for nature on the island. The most important one is scientific research, on many different kinds of species. Unfortunately, however, island’s nature also faces some threats and weaknesses. The greatest threats are non-native and invasive species (cows, goats, etc.), climate change and pollution. The most important weaknesses are a lack of environmental awareness, limited area of the island and small research populations (amount of species present on the island).

Climate change will affect St. Eustatius. IPCC predictions predict that temperatures will rise by approximately a minimum of 0.7 ˚C to a maximum of 2.4 ˚C by the end of the century, according to RCP 4.5 Precipitation rates will, according to RCP 4.5, vary by a maximum of -29% to a maximum of +14%. Sea levels will rise by approximately 0.5-0.6 meters by the end of the century (IPCC, 2013). This is all compared to the mean of the period 1986-2005.

These predictions will have some impacts on St. Eustatius. Climate change will especially have an impact on six different areas. These include: erosion, extreme events, coral reefs, human health, nature and tourism. The erosion rate is likely to increase in the future because of climate change. This will have a huge impact on the island. Also extreme events, like storms/hurricanes, are likely to happen more often in the future, with more extreme strengths. This will affect the corals around the different reefs that surround St. Eustatius. Not only will storms affect corals, but also rising sea temperatures will have a negative impact. Human health will also suffer under the effects of climate change. Mosquito density is likely to increase in the future, because of a more wet climate (IPCC, 2013). These mosquitos can spread diseases like dengue fever and the West Nile Virus. Terrestrial species will also experience the negative impacts of climate change. The main impact will be a shift in ecological zones. Finally, tourism can also suffer the negative impacts of climate change.

Date
2015
Data type
Other resources
Theme
Research and monitoring
Geographic location
St. Eustatius
Author