Queen Conch

New Insight for Protecting the Future of Queen Conch

A new survey technique provides insight into Queen Conch populations off the islands of Anguilla, St. Eustatius and within the Saba Bank. This research offers new information concerning Queen conch population distribution, useful for management authorities. Queen conch population in the Caribbean in general  have been decimated by intense fishing pressure so improving surveying techniques will aid in their overall management in the region. 

Queen conch. Photo source: Mark Vermeij

Queen conchs (Aliger gigas) are an iconic species of the Caribbean, representing both economic and cultural importance. Unfortunately, these species are heavily exploited, as their meat is popular in local cuisine and their shells are popular decorative pieces. Historically population data for Queen conch were gathered using dive surveys, however, these can be logistically demanding and expensive and limited to depths accessible to divers. Luckily, a new collaborative study by Wageningen University and Research, Chicago’s Shedd Aquarium, Van Hall Larenstein University of Applied Sciences and the Royal Netherlands Institute for Sea Research worked to improve these population estimates by implementing a novel towed video system.   

New Techniques 

Through combining traditional dive surveys with the towed video system, researchers can now explore species abundance to a depth of 60 m. In addition, this method allows new relationships between environmental variables and conch abundance through this range which had previously been poorly studied. It is understood that Queen conch move to deeper waters as they mature, so being able to document these deeper depths will give researchers and managers a more complete view of conch populations.   

The Results 

Surveys were conducted throughout three different locations: Anguilla, St. Eustatius and within the Saba Bank. Saba Bank was found to have the highest overall mean conch density, with an average of 126 conch per hectare, and ranged from depths of 16 m to 50 m. St. Eustatius was found to have a mean density of 62 conch per hectare, ranging from depths of 11 m to 45 m. For all three locations the highest densities of conch were found in water deeper than 25 m, with densities of 393 conch/ha at depths greater than 40 m on Saba Bank and 285 conch/ha at depths greater than 30 m on St. Eustatius. 

In general, this study found patchy distribution patterns of adult conch, likely due to aggregating behavior during spawning events. Other environmental factors, such as algal cover, distance to the open ocean and depth were also shown to impact conch abundance. Depths between 17 and 45 m were shown to have the greatest number of reproductive conch, highlighting the importance of safeguarding these areas to protect the reproductive capacity for these populations in the future. 

Source: Marion Haarsma

Recommendations 

With this new information, management authorities can now focus their attention to areas likely to host Queen conch populations. Researchers from this project recommend that future Queen conch surveys operate over a range of depths while sampling a variety of bottom conditions. These results can then be analyzed to better understand the connection between the conch distribution and local or regional factors. Although each island may require their own approach, this study highlights that many of these factors may be universal and should be considered when designing future campaigns. 

There is still much to be learned about Queen conch, such as the impact of algal cover or shifts in seagrass densities and species on their foraging behaviors. Gaining a holistic understanding of local conch populations will aid in the design and implementation of effective conservation projects moving forward. To learn more about this project, you can find the published article on the Dutch Caribbean Biodiversity Database by using the link below. 

Report your sightings  

Have you observed an Queen conchs? Report your nature sightings and photos on the website 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. Besides, DCNA, Observation International and Naturalis Biodiversity Center are working together to develop on automated species identification app for your phone. Your uploaded photos are of great value to make this possible. For questions, please contact research@DCNAnature.org  

 

Read more  

You can learn more about this research by reading the published article on the Dutch Caribbean Biodiversity Database using the button below. 

 

More info in the Dutch Caribbean Biodiversity Database

 

 

Published in BioNews 52

Date
2022
Data type
Media
Theme
Research and monitoring
Geographic location
Saba
Saba bank
St. Eustatius
Author

Special Edition: Transboundary Species

There has been a recent increase in public awareness of environmental issues as the effects of climate change have become ever more noticeable in our daily lives. As we enter a new decade, it becomes useful to review what conservation efforts have worked so far, and take inventory of what efforts will be required for the future. Starting with the constitutional referendum creating the Caribbean Netherlands (Bonaire, St. Eustatius and Saba (BES), the response to conservation challenges of all six Dutch Caribbean islands have varied. Since 2010, the BES islands have seen an overall increase in funding support and conservation actions, and therefore presumably also saw greater improvements when compared to Aruba, Curaçao and Sint Maarten, though clearly not enough (Sanders et al, 2019).

The goal of this Transboundary Species special edition of BioNews is to provide an update on the latest published research results and highlight the need for transboundary protection. These species know no boundaries, and thus move between the Dutch Caribbean islands and beyond. Their protection will require broadscale conservation efforts which cover the entire Caribbean, including the six Dutch Caribbean islands. Collaboration between all six islands is of the utmost importance. This is one of the Dutch Caribbean Nature Alliance’s (DCNA) main goals: working together and sharing skills, knowledge and resources to maintain a solid network and support nature conservation in the entire Dutch Caribbean.

 

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
Saba bank
St. Eustatius
St. Maarten
Author

Status of the queen conch Strombus gigas stocks, management and trade in the Caribbean: a CITES review.

The Queen conch Strombus gigas, a large marine gastropod, is found in the territorial waters of 36 countries and tettitories in the Caribbean region.  Over the past decades, intensive fishing has led to population declines resultin gin the total or temporal closure of the fishery in a number of locations.  Since November 1992, the species has been included in Appendix II of CITES.  In 2002, concerns about levels of illegal trade led to a "review of Significant Trade" in queen conch by TRAFFIC on behalf of the CITES.  For this review, data on commercial fisherisies landings, CITES trade data, stock status, and management measures were compiled with the assistance of CITES and fisheries authorities, and regional experts.

Date
2005
Data type
Other resources
Theme
Research and monitoring
Author

Interaction of Physical and Biological Factors in the Large-Scale Distribution of Juvenile Queen Conch in Seagrass Meadows

Large-scale distribution of a large, commercially significant gastropod, Strombus gigas (queen conch), was investigated in a II ,OOO-haregion of the Great Bahama Bank near Lee Stocking Island, Exuma Cays. Maps of depth and seagrass biomass, generated with Landsat thematic mapper data, and a 4-year survey of juvenile conch distribution showed that most of the juveniles were in aggregations located in 1.5-4.0-m water depth. Although general locations of juvenile conch aggregations remained the same between 1989 and 1992, their total surface area occupied only about 1.5% of the 8,300 ha of seagrass habitat available. Locations of only the most persistent long-term aggregations could be predicted on the basis of preferred seagrass biomass (30-80 g dry weight m-2); however, important conch nurseries were always located in tidal channels which brought clear, oligotrophic water from the Exuma Sound. Harmonic analysis of water temperature data from sites with and without juvenile aggregations showed that conch nurseries were subject to flushing with oceanic water on every tide, whereas non-conch sites reflected only diurnal heating and cooling of bank water. Relationships between circulation and juvenile conch distribution on the Great Bahama Bank may be related directly to larval recruitment, or indirectly to aspects of nutrient cycling and food production; evidence for both mechanisms exists. Although exact locations of conch aggregations shift from year to year, these shifts appear to occur within larger nursery habitats, the boundaries of which are set by a precise combination of physical and biological factors. Because most meadows are probably unsuitable for this severely ovcrfished species, critical nursery habitats should be identified and protected. 

Date
1996
Data type
Scientific article
Theme
Research and monitoring

Abundance and population structure of queen conch inside and outside a marine protected area: repeat surveys show significant declines

ABSTRACT: Effectiveness of a marine protected area (MPA) in supporting fisheries productivity depends upon replenishment patterns, both in supplying recruits to surrounding fished areas and having a sustainable spawning stock in the MPA. Surveys for queen conch Strombus gigas were made in 2011 at 2 locations in the Exuma Cays, The Bahamas, for direct comparison with surveys conducted during the early 1990s at Warderick Wells (WW) near the center of the Exuma Cays Land and Sea Park (ECLSP) and at a fished site near Lee Stocking Island (LSI). There was no change in adult conch density and abundance in the shallow bank environment at LSI where numbers were already low in 1991, but numbers declined 91% in the deeper shelf waters. At WW, the adult population declined 69% on the bank and 6% on the island shelf. Unlike observations made in the 1990s, queen conch reproductive behavior near LSI is now rare. Average age of adult conch (indicated by shell thickness) at LSI decreased significantly during the 20 yr period between surveys, while average age increased at WW and juvenile abundance decreased. These results show that the LSI population is being overfished and the WW population is senescing because of low recruitment. In 2011, the ECLSP continued to be an important source of larvae for down- stream populations because of abundant spawners in the shelf environment. However, it is clear that the reserve is not self-sustaining for queen conch, and sustainable fishing in the Exuma Cays will depend upon a network of MPAs along with other management measures to reduce fishing mortality. 

Date
2012
Data type
Scientific article
Theme
Research and monitoring

What constitutes essential nursery habitat for a marine species? A case study of habitat form and function for queen conch

ABSTRACT: There is increasing recognition that habitats should be managed as part of fisheries management. It is generally assumed that amount of suitable habitat is linked to production of de- mersal species and that maps of bottom type will provide the information needed to conserve essen- tial habitats. In this review, a synthesis of nursery habitat is made for Strombus gigas (queen conch), a large, economically important gastropod in the Caribbean region. Juveniles occur on a variety of bottom types over their geographic range. In the Bahamas, nurseries occur in specific locations within large, beds of seagrass, while obvious characteristics of the benthic environment such as seagrass density, depth and sediment type are not good predictors of suitable habitat. Rather, nurseries persist where competent larvae are concentrated by tidal circulation and where settlement occurs selec- tively. Nursery locations provide for high juvenile growth resulting from macroalgal production not evident in maps of algal biomass, and they provide for low mortality compared with seemingly simi- lar surroundings. Therefore, critical habitats for queen conch juveniles are determined by the inter- section of habitat features and ecological processes that combine to yield high rates of recruitment and survivorship. While maps of bottom type are a good beginning for habitat management, they can be traps without good knowledge of ecological processes. A demersal species can occupy different substrata over its geographic range, different life stages often depend upon different bottom types, and specific locations can be more important than particular habitat forms. Habitat management must be designed to conserve habitat function and not just form. Implicit in the concept of ‘essential habitat’ is the fact that expendable habitat exists, and we need to prevent losses of working habitat because of inadequate protection, restoration or mitigation. Key nurseries may represent distinctive or even anomalous conditions. 

Date
2003
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire
Author

The Status of Queen Conch, Strombus gigas, Research in the Caribbean

An important scientific workshop on queen conch was held in Caracas, Ven­ ezuela, in July 1991. This workshop and the proceedings that emerged from it (Appeldoom and Rodriguez, 1994) pro­ vided a good background on the status of research on biology, fisheries, and mariculture of the queen conch. Be­ cause the general biology of the queen conch is already relatively well known, the purpose of this paper is to summa­ rize some of the important advances made in the study of queen conch since the 1991 workshop. Emphasis has been placed on topics related to the ecology of queen conch that are most relevant to fisheries management and stock re­ habilitation. In the following sections an attempt has been made to draw con­ clusions about habitat requirements for the species, mortality of juveniles as it relates to stock rehabilitation and en­ hancement, larval ecology and fisher­ ies oceanography of the species, and the conservation of reproductive stocks. 

Date
1997
Data type
Scientific article
Theme
Research and monitoring
Document
Author

Queen Conch Expert Workshop

Introduction

  1. The queen conch (Strombus gigas) is one of the most important fishery resources in the Caribbean in terms of its annual landings and its social and economic importance. Queen conch is an edible marine gastropod of the Caribbean Region that has been listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and Annex III of the Protocol Concerning Specially Protected Areas and Wildlife (SPAW) of the regional Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region (Cartagena Convention).
  2. While many problems of the fisheries in the region have been addressed, there is still significant concern over the status of some stocks and management in the region. As a result, a Queen Conch Expert Workshop was organised by the Caribbean Fisheries Management Council in Miami, USA, 22–24 May 2012 to discuss the various constraints on improving the management of the queen conch fisheries. This report contains the findings, conclusions and recommendations of this workshop. 
Date
2012
Data type
Other resources
Theme
Research and monitoring

Support to improve and harmonize the scientific approaches required to inform sustainable management of queen conch (Strombus gigas) by CARIFORUM States

This report describes the activities and outputs of the project to improve and harmonize scientific approaches required for the sustainable management of queen conch.

Five case studies were undertaken for the countries: The Bahamas, Belize, Dominican Republic, Grenada and Haiti. For each case study, a report of findings, conclusions and recommendations were completed. With the exception of Haiti, each country was visited and information obtained from stakeholders and local sources.

A regional review of scientific and management approaches to the management of queen conch was completed, containing regional management options. Information for regional review was obtained from the cases studies, CRFM, other international organisations and other contacts in the region.

Based upon the information obtained from the case studies and review, a 3-day regional validation workshop was conducted in St. Vincent, 6th-8th June 2013.

A Regional Management Options Paper was successfully produced and endorsed by the validation workshop for further consideration by CRFM and CARICOM states.

The main recommendation is that the Regional Management Options Paper should be used as the basis for a regional queen conch management plan by CARICOM states. Implementing the recommendations in the paper will not only improve management, but also increase international confidence in the region’s fishery management, reducing the chance of trade sanctions.

This report also places emphasis on developing analytical approaches for harvest strategies and specifically support for The Bahamas in developing its harvest strategy. 

Date
2013
Data type
Other resources
Theme
Research and monitoring
Document
Author

Shell Lip Thickness Is the Most Reliable Proxy to Sexual Maturity in Queen Conch (Lobatus gigas) of Port Honduras Marine Reserve, Belize

Queen conch (Lobatus gigas) is an important food source and export product for Belize, where extraction is regulated by shell length (SL) and market clean weight (MCW) limits. However, lip thickness (LT) limits are used to manage juvenile mortality and reduce risk of growth overfishing in other countries. Empirical studies suggest relationships between LT and sexual maturity vary spatially and need to be determined locally. This study was conducted to determine the most reliable, easily measurable proxy indicator(s) of maturity and associated target size limits in L. gigas that can effectively restrict harvest of juveniles. Morphological measures (SL, LT, lip width, unprocessed meat weight, MCW, operculum dimensions), gonadosomatic index (GSI) and histological evaluations were recorded from L. gigas collected in PHMR before, during, and after the L. gigas closed season. Upon determining Period 2 (during closed season) as the peak reproductive period, relationships between these variables in Period 2 were examined. No relationship was found in males between SL and maturity, and was weak in females, whereas there were significant curvilinear relationships between LT and GSI for both sexes, suggesting urgent need to base size limits on LT not SL. LT at which 50% of the population was mature (LT50) was 15.51 mm for females and 12.33 mm for males, therefore a 16 mm LT limit is recommended. MCW of female L. gigas was also significantly related to GSI, indicating MCW may be an appropriate management tool in conjunction with LT as it can be measured at landing sites whereas shells are usually discarded at sea. However, MCW at which 50% of females were mature (MCW50) was 199 g and many individuals exceeding LT50 had MCW <199 g, suggesting the current 85 g MCW limit is too low to protect juveniles yet 199 g MCW limit would be too high to substitute the recommended LT limit at landing sites. To minimize short-term impacts yet maximize long-term benefits to fishers’ livelihoods, multi-stage adaptive management is recommended that integrates initial catch reductions, followed by introduction of size limits of 16 mm LT, and 150 g MCW. Adjustable LT and MCW limits determined by fishery simulation could later be introduced. 

Date
2017
Data type
Scientific article
Theme
Research and monitoring