Adolphe O. Debrot

The effect of artificial reef design on the attraction of herbivorous fish and on coral recruitment, survival and growth

A B S T R A C T

Fish assemblages of different types of artificial reefs can differ greatly in abundance, biomass and composition, with some reef types harboring over five times more herbivores than others. It is assumed that higher herbivorous fish abundance results in a higher grazing intensity, affecting the benthic community by means of enhanced coral recruitment, survival and growth. Territorial fish species might affect this process by chasing away other fish, especially herbivores. In this study we compared the fish assemblage, territorial behavior and grazing intensity by fish on two artificial reef types: reef balls and layered cakes, differing greatly in their fish assemblage during early colonization. In addition, the effect of artificial reef type on benthic development and coral recruitment, survival and growth, was investigated. Although layered cakes initially harbored higher herbivorous fish biomass, this effect was lost during consecutive monitoring events. This seems to be the result of the higher territorial fish abundance around the layered cakes where almost four times more chasing behavior was recorded compared to the reef balls. This resulted in a more than five times lower fish grazing intensity compared to the reef-ball plots. Although macroalgae were effectively controlled at both reefs, the grazing intensity did not differ enough to cause large enough structural changes in benthic cover for higher coral recruitment, survival or growth. The high turf algae cover, combined with increasing crustose coralline algae and sponge cover likely explained reduced coral development. We recommend further research on how to achieve higher grazing rates for improved coral development on artificial reefs, for example by facilitating invertebrate herbivore. 

Date
2023
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Saba
St. Eustatius

Obituary – Dr. Walter (Wòti) Bakhuis, Carmabi/Stinapa director 1981-2006

On the 25th of March this year, Dr. Walter L. (Wòti) Bakhuis passed away at the ripe old age of 80 in Maarssen, The Netherlands. With his passing, the Dutch Caribbean conservation community lost a good friend and longtime colleague who served as the director of Carmabi and Stinapa-Netherlands Antilles for a period of 25 years (1981-2006). In addition to brothers and sisters, he leaves behind his wife Rineke, two sons, Walter and Jimmy and two granddaughters.

Wòti was a very modest person who avoided the spotlights as much as possible. He was first and foremost a people person; friendly, warm, ready to help, and an excellent listener. It was a great pleasure to his many colleagues to have worked with him throughout the years. During his 25 years as director of Carmabi and Stinapa he spent almost all his time selflessly helping, leading and enabling others. Right from the beginning there hardly was any time for his own research and his last peer-reviewed scientific contribution titled “Size and Sexual Differentiation in the Lizard Iguana iguana on a Semi-Arid Island” was published in 1982 in the prestigious Journal of Herpetology. Afterwards, Wòti left the details of science to others and instead dedicated the rest of his career fully to the many concerns of colleagues, board members, university students, visiting scientists and the conservation of the natural and cultural patrimony of the Dutch Caribbean.

Wòti received his doctorate in brain research from the Rijksuniversiteit of Groningen in in 1977 and began working for the Caribbean Marine Biological Institute (Carmabi) and Stinapa (Netherlands Antilles National Parks Foundation) in 1978 as the first island-born, non-European staff member and scientist. On the 3d of March 1981, he took over the reigns from his predecessor Dr. Ingvar Kristensen and uninterruptedly served as an exemplary director of both organizations till July 2006, after which he emigrated to The Netherlands together with his Dutch wife Rineke. In the subsequent years he repeatedly served his successors with wise advice. His last visit to the island was in October 2021 on the occasion of his 80th birthday.

Because of his unwavering resolve at critical moments he was often able to ensure the continued survival and functioning of his institutions in an environment that often was not very understanding of the need for natural science and nature conservation. In the Dutch Caribbean, putting ideals into action and results can be especially challenging. The lack of understanding of the need for sustainability, financial limitations, and petty politics can be very discouraging and frequently delay or stagnate critical progress. However, thanks to his particularly positive Christian attitude of hope and untiring patience, discouragement and frustration never were able to get hold of him.

His untiring efforts and patience contributed to many major milestones for both science and conservation in the Dutch Caribbean. Some of the most important lasting results in which he played a key role, and unbeknownst to many, were the establishment of the Bonaire National Marine Park, the Curaçao Underwater Park, the Saba Marine Park, Parke Nashonal Shete Boka in Curaçao and the purchase of 240 hectares of crucial conservation habitat of the Jeremie plantation in Curacao for expansion of the Christoffel National Park and the conservation of rare endemic trees.

A country without institutions would be little less than an unorganized and uncoordinated collection of individuals. For this reason, institutions form the backbone and key infrastructure of nations to be treasured, nourished and built. In the Dutch Caribbean small economies of scale and fragmentation undermine performance and continuity within many sectors of society. However, during Wòti’s years with Carmabi and Stinapa he did everything he could to strengthen and anchor these organizations as being key infrastructure of the Dutch Caribbean. In that he has certainly succeeded and which arguably constitutes one of his most important and lasting contributions to society in the Dutch Caribbean. In 2003 he received the royal distinction of Knight of the Order of Orange-Nassau for his enduring and multifaceted contributions to society.

 

submitted by:

Dr. Adolphe O. (Dolfi) Debrot, Wageningen Marine Research, The Netherlands, Carmabi and Stinapa subdirector (1989-2006), director (2006-2010)

ir. Paul Stokkermans, Carmabi director (2010- present)

 

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In Memoriam Dr. Walter (Wòti) Bakhuis

Op 25 maart is in Maarssen, Dr. Walter L. (Wòti) Bakhuis op 80-jarige leeftijd van ons heengegaan. Daarmee hebben wij een goede oude vriend verloren die wij kennen van zijn meer dan 25 jaar als directeur van Carmabi en Stinapa op Curaçao. Hij laat naast broers en zusters, zijn echtgenote Rineke, twee zoons, Walter en Jimmy, en zijn twee kleindochters achter.

Wòti was een zeer bescheiden man die weinig op de voorgrond trad en was vooral een mensen mens. Het was bijzonder prettig om met hem al die jaren samen te hebben gewerkt. Gedurende zijn 25 jaar aan het roer van Carmabi en Stinapa is hij vooral leidinggevend en voorwaardenscheppend bezig geweest. Tijd voor eigen onderzoek was er vanaf de eerste dag al nagenoeg niet. Wòti stond voor collega’s en bestuursleden klaar op alle uren van de dag.

Hij promoveerde in 1977 op de Rijksuniversiteit te Groningen en trad in 1978 in loondienst van de Stichting Caraïbisch Marien Biologisch Instituut (Carmabi) als eerste Antilliaanse staflid van de organisatie. Op 3 maart 1981, trad hij aan als directeur en heeft tot juli 2006 meer dan 25 jaar lang op voortreffelijke wijze de leiding gevoerd over zowel het onderzoeksinstituut Carmabi als de natuurbeheersstichting Stinapa. Daarna heeft hij zijn opvolgers menigmaal met raad en daad bijgestaan. Zijn laatste bezoek aan het eiland was in October 2021 ter viering van zijn 80ste verjaardag.

Dankzij zijn inspanningen vele belangrijke mijlpalen en resultaten bereikt op de gebieden van zowel natuuronderzoek en -bescherming. Hij heeft een instrumentele rol gespeeld in o.a. de oprichting van het Bonaire Marine Park, het Curaçao Underwater Park, het Saba Marine Park, de instelling van Parke Nashonal Shete Boka, Curaçao en de aankoop 240 ha cruciaal natuurgebied van plantage Jeremie

Vanwege zijn resoluut optreden op cruciale ogenblikken, is Carmabi goed blijven functioneren in een omgeving die vaak weinig begrip kon opleveren voor de noodzaak voor natuurbescherming. In de Nederlandse Cariben is het minder vanzelfsprekend dat er een soepel verloop is bij het omzetten van een ideaal in daden. Het klimaat, de financiële problematiek, de vaak politieke tegenwerking, etc., kunnen bijzonder ontmoedigend zijn. Dankzij zijn bijzonder positieve christelijke kijk op zaken en onmeetbare geduld, hebben ontmoediging en frustratie nooit vat op hem kunnen krijgen.

Een land zonder instituten zou weinig meer zijn dan een samenraapsel van individuën. Instituten vormen daarom de infrastructuur van een land, en dienen gezond en sterk gehouden te worden. Op de Antillen vormen kleinschaligheid en versnippering grote problemen voor diverse sectoren binnen de maatschappij. Tijdens Wòti’s jaren op Carmabi heeft hij echter alles gedaan wat binnen zijn macht was om Carmabi als één van de belangrijke instituten van de Nederlandse Cariben te behouden en te versterken. Dat is hem zeker gelukt en is mogelijk zijn allerbelangrijkste verdienste aan onze Antilliaanse samenleving.  In 2003 heeft hij voor zijn inspanningen een Koninklijke onderscheiding ontvangen, als Ridder in de Orde Oranje Nassau.

Dr. Adolphe O. (Dolfi) Debrot, Wageningen Marine Research

ex-Carmabi onderdirecteur (1989-2006), directeur (2006-2010)

 

  1. Paul Stokkermans, Directeur Carmabi (2010- heden)

 

 

 

 

Published in BioNews 52

 

Date
2022
Data type
Media
Theme
Education and outreach
Tags
Geographic location
Aruba
Bonaire
Curacao
Saba
Saba bank
St. Eustatius
St. Maarten

An integrative approach to assess non-native iguana presence on Saba and Montserrat: are we losing all native Iguana populations in the Lesser Antilles?

Abstract

Invasive alien species are among the main drivers of the ongoing sixth mass extinction wave, especially affecting island populations. Although the Caribbean is well-known for its high species richness and endemism, also for reptiles, equally important is the regional contribution of non-native species to island biodiversity. The Lesser Antilles encompass high genetic diversity in Iguana, though most native populations either have gone extinct or are declining following competitive hybridization with invasive non-native iguanas. Here we assessed non-native presence in two poorly-studied native melanistic Iguana iguana populations using available genetic tools, and explored utilizing size-dependent body measurements to discriminate between native and non-native iguanas. Genetic samples from Saba and Montserrat were genotyped across 17 microsatellite loci with STRUCTURE and multivariate analyses indicating non-native iguanas presence only on Saba. This was corroborated by mtDNA and nDNA sequences, highlighting a non-native origin in Central America and the ABC islands. We identied preliminary evidence suggestive of hybridization. Morphological variation among size-dependent characteristics showed that non-native iguanas have signicantly larger subtympanic plates than native iguanas. Non-native individuals also differed in scalation and coloration patterns. Overall, our ndings demonstrate the need for continuous monitoring for non-native iguanas within remaining native Iguana populations in the Lesser Antilles, with those not directly threatened by non-native iguanas restricted to only 8.7% of the historic range. Although genetic data allows for identication of non-native or hybrid iguana presence, this eld-to-lab workow is time consuming. Rapid in-situ identication of non-native individuals is crucial for conservation management, and besides scale and coloration patterns, we have highlighted the utility of size-dependent variables for rapid diagnosis. We urge regional partners to build morphometric databases for native Iguana populations that will help to quickly detect future incursions of non-native iguanas and allow the rapid implementation of effective countermeasures during the early phase of invasion.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Saba

Assisted Natural Recovery: A Novel Approach to Enhance Diadema antillarum Recruitment

The massive die-off of the sea urchin Diadema antillarum in 1983–1984 is one the main reasons for low coral recruitment and little coral recovery in the Caribbean. As the natural recovery of D. antillarum is slow to non-existent, multiple restoration studies have been attempted. There are currently three different approaches to obtain individuals for restocking: the translocation of wild-collected juveniles or adults, lab-reared juveniles cultured from wild-collected settlers, or lab-reared juveniles cultured from gametes. All three methods are costly and can only be applied on a relatively small scale. We here propose a fourth, new, approach, which we term assisted natural recovery (ANR) of D. antillarum populations. ANR, a concept already applied in terrestrial restoration to restore forests and grasslands, can accelerate succession by removing barriers to natural recovery. In this study, performed on the Dutch Caribbean island of Saba, suitable settlement substrate was provided in the form of bio ball streamers that were attached to the reef shortly before the settlement season. At the end of the experiment, reefs with streamers had significantly higher D. antillarum recruit densities than control reefs without additional settlement substrate, indicating that the lack of settlement substrate is an important factor constraining natural recovery. However, D. antillarum recruit abundance was low compared to the measured settlement rates, possibly due to low post-settlement survival. The size distribution of recruits showed that recruits almost never became larger than 20 mm, which is likely due to predation. We conclude that, next to low settlement availability, low post-settlement survival and high predation on recruits also constrain the natural recovery of D. antillarum populations on Saba. To improve the survival of settlers till adults, we propose to 1) reduce predation on settlers by using bio balls or other substrates that can provide shelter to larger individuals and 2) optimize the reef habitat by removing macroalgae, either manually or by facilitating other herbivores. To improve the survival of recruits, we suggest to 1) choose sites with a known lower predation density or 2) protect recruits with a corral around the reef underneath the streamers. The combination of these measures could improve prospects for ANR, and we expect this new approach can contribute to the recovery of D. antillarum populations in the future.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Saba

Phenological trajectories of Caribbean very dry tropical forests diverge under different geologic formations

Abstract
Tropical dry forests experience pronounced seasonal changes in precipitation mani- 
fested in varied plant phenologies. At landscape scales, geologic substrate—one of the 
least understood abiotic factors interacting with precipitation—may modulate phe- 
nological responses in these forests through a combination of mechanisms regulat- 
ing water and nutrient use. We leveraged a phenological dataset from the semiarid 
island of Curaçao to examine the extent to which plant phenology at multiple levels 
of biological organization diverge under different geologies. Monthly observations 
over a 30-month period of leaves, flowers, and fruits of 69 plant species of different 
life forms at three nearby sites differing in their underlaying geology were used to 
examine intra- and inter-annual plant responses at species, community, and system 
levels. The integration of leaf, flower, and fruit observations at intra-annual scales 
revealed diverse phenological strategies among species, broad associations with geo- 
logic substrate, and the extent of intra-specific variation as a function of geology. The 
community- and system-level analyses at inter-annual scales showed a reduction in 
mean leaf scores during the 30-month period, a weak and strong leafless period in 
1993 and 1994, respectively, and differences among geologic substrates. Finally, we 
observed significant and positive relationships between precipitation and the pheno- 
phase scores; the strength of the relationships varied with phenophase and geologic 
substrate. Results of this work emphasize the importance of geologic substrate, and 
more broadly speaking landscape heterogeneity, in modulating plant phenological re- 
sponses in tropical dry forests. Ultimately, this information will become important to 
understand and mitigate global climate change impacts.
Abstract in Spanish is available with online material.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

POPULATION ESTIMATE, NATURAL HISTORY AND CONSERVATION OF THE MELANISTIC IGUANA IGUANA POPULATION ON SABA, CARIBBEAN NETHERLANDS

Abstract.– Intraspecific diversity is among the most important biological variables, although still poorly understood for most species. Iguana iguana is a Neotropical lizard known from Central and South America, including from numerous Caribbean islands. Despite the presence of native melanistic I. iguana populations in the Lesser Antilles, these have received surprisingly little research attention. Here we assessed population size, distribution, degree of melanism, and additional morphological and natural history characteristics for the melanistic iguanas of Saba, Caribbean Netherlands based on a one-month fieldwork visit. Using Distance sampling from a 38- transect dataset we estimate the population size at 8233 ±2205 iguanas. Iguanas mainly occurred on the southern and eastern sides of the island, between 180-390 m (max altitude 530 m), with highest densities both in residential and certain natural areas. Historically, iguanas were relatively more common at higher altitudes, probably due to more extensive forest clearing for agricultural reasons. No relationship was found between the degree of melanism and elevation, and few animals were completely melanistic. Furthermore, we found that body-ratio data collection through photographs is biased and requires physical measuring instead. Although the population size appears larger than previously surmised, the limited nesting sites and extremely low presence of juvenile and hatchling iguanas (2.4%), is similarly worrying as the situation for I. delicatissima on neighboring St. Eustatius. The island’s feral cat and large goat population are suspected to impact nest site quality, nest success, and hatchling survival. These aspects require urgent future research to guide necessary conservation management.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Saba

A renewed call for conservation leadership 10 years further in the feral cat Trap-Neuter-Return debate and new opportunities for constructive dialogue

Abstract

It has been 10 years since a seminal paper in the journalConservation Biologycalled for stronger leadership from the conservation community in counteringthe growing inappropriate use of Trap-Neuter-Return (TNR) as a method tocontrol feral cat,Felis catus, populations. The practice is rapidly spreading toareas of wildlife and conservation significance, and the need to counter thisdevelopment is extremely urgent. So far, the promulgation of TNR has beenbased on a narrow, single-species approach to animal welfare. However, anew, yet little-noticed, species-inclusive perspective on animal welfare includesthe consideration of collateral animal suffering for a more equitable assess-ment of TNR. Each setting, depending on the level of conservation required,may call for different methods for the management of free-roaming cats. TNRis just one such method and its appropriateness depends on the specific wild-life conservation needs for each area specified.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
St. Eustatius
St. Maarten

Case study of a Rapid Response Removal Campaign for the invasive alien green iguana, Iguana iguana

Abstract

The Invasive Alien Green Iguana (IAGI), Iguana iguana, has spread worldwide via the pet trade, as stowaways and via other means and has become a pest species of global concern. It also represents a major threat to the endemic Lesser Antillean Iguana, Iguana delicatissima, on St. Eustatius. Following the capture of an adult female IAGI on St. Eustatius in early 2016, we conducted a Rapid Response Removal Campaign (RC) from April 2016 to January 2017. Three sets of directed visual surveys totaling 409.5 observer hours and covering a combined trajectory of 114.2 km realized only a single detection of a hybrid that was later removed. During the remainder of the campaign period, an additional four IAGI hybrids were opportunistically detected and removed thanks to park staff or community involvement. Since the end of the campaign, eight additional detections and removals have been realized, three of which were IAGIs caught while offloading freight in the harbour and five of which were hybrids caught in surrounding suburban areas. We suggest that at least four distinct IAGI introductions to St. Eustatius occurred between 2013 and 2020. Our results show the value of motivating and mobilizing stakeholders and the public at an early stage of an invasion. Since the program’s initiation, eight of the 13 iguanas detected for culling were thanks to public and key stakeholder support and involvement. Four years after our campaign, the number of IAGIs and their hybrids still appear to be limited and concentrated in and around inhabited areas. Additional removal campaigns should be initiated as soon as possible, firmly based in public outreach, motivation and engagement. New legislation is needed to prohibit the importation, possession and harbouring of IAGIs or hybrids and to provide a framework for long-term structural funding required for effective control and removal. Routine fumigation and rigorous inspection of arriving cargo to eliminate the risk of stowaway IAGIs are also recommended. Culling of IAGIs is recommended for the port of St. Maarten, which serves as a major point of dispersal of IAGIs to St. Eustatius and likely also other islands in the region.

Date
2022
Data type
Scientific article
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

Establishment of two nonnative parthenogenetic reptiles on Saba, Dutch Caribbean: Gymnophthalmus underwoodi and Indotyphlops braminus

The native herpetofauna of the Lesser Antillean island of Saba (13 km2; 17.63°N, -63.24°W) includes one snake, Alsophis rufiventris, and four species of lizards, Anolis sabanus, Iguana melanoderma, Sphaerodactylus sabanus, and Thecadatylus rapicauda (Powell et al. 2015). Here, we report the establishment of both Gymnophthalmus underwoo-di Grant, 1958 and Indotyphlops braminus (Daudin, 1803) on the island.

 

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Geographic location
Saba