The Lesser Antillean Iguana, Iguana delicatissima is the largest extant native land vertebrate of St. Eustatius and was recently lost (~1990s) from the only other Dutch Caribbean island where it was native (St. Maarten). It is an IUCN Red List Critically Endangered (CR) species that has disappeared from most islands in the Lesser Antilles. A recognized principal cause for its endangerment throughout the islands is displacement by and hybridization with invasive alien Green Iguanas, Iguana iguana (IAGI) (Knapp et al. 2014). On 22nd February 2016 an adult female IAGI was caught in Princess Estates, St. Eustatius. The possibility that the animal had been present on the island for a longer period, that it may have laid one or more nests, or the possibility that there may have been other IAGIs on the island, represented an imminent danger to the continued existence of the Lesser Antillean Iguana. We conducted a Rapid Response Extermination Campaign (RREC) with the goal of wiping out the IAGI at an early stage. Three thorough visual surveys were conducted during 2016-2017 in key risk areas in an attempt to detect and eliminate all IAGIs and their hybrids. In total 409.5 observer hours were spent during three dedicated surveys in and around areas where IAGIs or hybrids had been captured, seen or reported. Searches were conducted over a total of 40 days and covered a total of trajectory of 114.2 km. Only a single detection was realized during these directed surveys. This suggests that the RREC took place at an early stage of the invasion. Nevertheless, due to local publicity via newspapers and radio programs, several records were reported by the public. Thanks to these reports, and opportunistic encounters by park management staff, five captures of IAGIs or their hybrids were realized between February 2016 and January 2017. Since then eight additional captures have been realized, demonstrating that the RREC, even when augmented by public support and extra vigilance by park management staff, was insufficient to purge the island of the IAGI. Our study documents three distinct IAGI introductions between 2013 and 2020, one of which was likely intentional and two of which were incidental stowaways on container ships. Our results show that, even though it is a relatively large animal, due to its relatively secretive nature, camouflage, and high fecundity, eliminating the IAGI from an island will require a more intensive and sustained effort than we provided, even by means of an RREC in the early stages of the invasion. Informing stakeholders and the public in an early stage of the campaign can clearly make a critical contribution towards an RREC. Even four years after the campaign, the numbers of the IAGI and its hybrids still appear to be limited and concentrated in and around inhabited areas, their likely main point of entry being the island’s harbour. We conclude that it may not be too late to quell the invasion before the critically endangered, largest surviving island-endemic vertebrate is permanently lost from St. Eustatius. Additional IAGI extermination campaigns need to be launched as soon as possible. The harbour of St. Maarten was identified as the source on the most recent 2020 introduction. As St. Maarten serves as a major inter-island trans-shipment hub in the Lesser Antilles, and the Lesser Antilles are rich in endemic iguanas vulnerable to the IAGI, it is essential that St. Maarten ports cull all Green Iguanas in and around their grounds to prevent the spread of this major pest to the islands with which they trade.
Queen conch (Lobatus gigas), is an economically and culturally important marine gastropod. The species is subject to extensive exploitation throughout large parts of the Caribbean which has led to a decrease in population densities across much of the species’ distribution range. Hence, there is a need for protective measures to safeguard the reproductive stock. This requires a better estimation of its size at maturity, which is best quantified as the thickness of the lip that the shell develops after reaching its maximum length. The lip thickness at 50% maturity (LT50) was determined using a logistic and an accumulation model, from seven representative location of distribution of this species in the Wider Caribbean Region. LT50 of both females (7–14 mm) and males (4–11.5 mm) varied between different locations in the Caribbean, although it did not correspond with variation in water temperature. In most cases females had a larger LT50 than males indicating sexual dimorphism. LT50 values estimated with the logistic model were smaller (7–14mm for females, 4–11.5mm for males) than values estimated with the accumulation model (13–26mm for females, 16–24mm for males), showing an overestimation of LT50 in queen conch in previous studies which used the accumulation model to estimate LT50. Locations with a relatively high variation in water temperature had a significantly shorter reproductive season. The implementation of adequate minimum size regulation based on lip thickness (ca. 15 mm) and a Caribbean wide seasonal closure (May–September) using the most recent biological information from this study, taking into consideration the local differences in LT50 and reproductive season, will assist in developing a long term sustainable queen conch fishery in the Caribbean
Concern for the future of Queen Conch has resulted in a number of regional and international measures, which have been taken to protect them. Trade in Queen Conch came under regulation when the species was listed in Appendix II of CITES in 1992, which prompted “numerous collaborative initiatives to promote its recovery, reduce overfishing and ensure legal, sustainable trade” (CITES, 2017). At the first meeting of the International Queen Conch Initiative in 1996, several Caribbean countries adopted the Declaration of San Juan and thereby pledged to improve regional management of the Queen Conch through harmonized regulations, enhanced communication and the application of scientific advice for the management and assessment of stocks (Daves and Fields 2006). In the Dutch Caribbean, a 4-year PhD project entitled “Queen conch in the Dutch Caribbean Territories (CONDUCT)” aims to improve our understanding of the ecology and life history of the Queen Conch and to provide guidelines for a more sustainable conch fishery. The project, which started in June 2014, is part of the TripleP@Sea and is a collaboration between Wageningen University & Research and Wageningen Marine Research.
This news-item was published in BioNews 10-2017.
A detailed understanding of spatial genetic structure (SGS) and the factors driving contemporary patterns of gene flow and genetic diversity are fundamental for developing conservation and management plans for marine fisheries. We performed a detailed study of SGS and genetic diversity throughout the overharvested queen conch (Lobatus gigas) fishery. Caribbean countries were presented as major populations to examine transboundary patterns of population differentiation.
Nineteen locations in the greater Caribbean from Anguilla, the Bahamas, Belize, Caribbean Netherlands, Honduras, Jamaica, Mexico, Turks and Caicos, and the USA.
We genotyped 643 individuals with nine microsatellites. Population genetic and multivariate analyses characterized SGS. We tested the alternate hypotheses: (1) SGS is randomly distributed in space or (2) pairwise genetic structure among sites is correlated with oceanic distance (IBOD).
Our study found that L. gigas does not form a single panmictic population in the greater Caribbean. Significant levels of genetic differentiation were identified between Caribbean countries (FCT = 0.011; p = .0001), within Caribbean countries (FSC = 0.003; p = .001), and among sites irrespective of geographic location (FST = 0.013; p = .0001). Gene flow across the greater Caribbean was constrained by oceanic distance (p = .0009; Mantel r = .40), which acted to isolate local populations.
Gene flow over the spatial scale of the entire Caribbean basin is constrained by oceanic distance, which may impede the natural recovery of overfished L. gigas populations. Our results suggest a careful blend of local and international management will be required to ensure long-term sustainability for the species.