Meijer zu Schlochtern, M.

Raw underwater towed video transects of the seabed of the Sababank. Originally made to estimate the queen conch densities these video's depict many hours of seabed recordings. See Boman et al. (2016) for more information or contact the DCBD administrator.

On the 6th of September powerful category five storm Hurricane Irma struck Sint Maarten with 185 MPH winds, causing widespread damage to the island and its infrastructure. The hurricane also caused significant damage to the island’s nature and environment, underwater life is also damaged severely due to surge and strong water motion, therefore the Sint Maarten Nature Foundation conducted Marine Park, Reef and Marine Research assessment to determine the level of impact underwater. 

Several St Maarten dives sites, in the Man of War Shoal Marine Park and around the island, have been visited and surveyed promptly for reef and coral damage, marine life presence, marine research setups and to assess the mooring systems for dive operators. Marine assessments were carried out from the 28th of September until the 6th of October 2017 and were continued again on the 1st of November until the 20th of November 2017.

Raw data of turtle nest observations, including: nest identification, species, false crawls, etc.

Please contact Nature Foundation St.Maarten for more information.

Raw data of shark observations by the Nature Foundation and St.Maarten dive schools (Dive Adventures, Dive Safaris, Scuba Fun, Ocean Explorers).

Please contact Nature Foundation St.Maarten for more information.

Raw data of brown pelican counts on St.Maarten 2010-2023. Counts from 2010-2012 differ in monitoring method from 2016-2023. The latter includes counts for the number of chicks on nests, fledgelings, adults in view on land and on sea.

Please contact Nature Foundation St.Maarten for more information.

Queen conch (Lobatus gigas) populations living deeper than 20 m are rarely studied, because of the limitations of conventional survey methods using divers [i.e., belt transect (BT), towed-diver]. A crucial management goal for conch populations is to maintain adult densities at adequate levels to ensure reproduction, which is highly density dependent. Therefore, accurate estimates of adult conch densities, both in shallow and deep areas, are essential. The rapid technical progress of video systems has made it possible to develop new cost-effective ecological sampling tools, which can be used to survey areas previously hardly accessible. A lightweight towed video array was used, which was able to survey adult conch throughout the species entire depth range (ca. 0–60 m depth), in a safe and efficient manner. The towed video method (TVM) was compared with a conventional BT method using scuba divers, in its ability to identify adult live and dead conch. A series of intercalibration transects was conducted in a high-complexity (HC) and in a low-complexity (LC) habitat by having the towed video followed by a diver conducting a concurrent standard BT, covering the exact same surface area as the towed video. In both the HC and LC habitat, adult live queen conch had similar counts with both methods. Adult dead conch were not mistaken for live conch but were significantly underestimated with the towed video compared with the BT. The results validate the use of TVM as a reliable sampling tool to estimate densities of live adult conch in both HC and LC habitats throughout the species depth range. 

Abstract:

The queen conch (Lobatus gigas) is under pressure and has decreased in distribution and abundance as a result of fisheries in the Caribbean region. To ensure sustainable fishery, knowledge on the population dynamics of this species is required. Therefore, this research focused on the status and the reproductive behaviour of the conch population around St Eustatius and provides information about the possibilities for a sustainable fishery. Conch distribution and abundance, population structure, reproductive activity and fishing pressure were determined in the coastal waters around the island of St Eustatius by dive surveys, towed video surveys, reproduction surveys and fishery catch surveys. The study covered the entire Statia National Marine Park waters and covered different habitats and depths up to 40m.

The study shows that the queen conch is abundant around St Eustatius, with mean densities of 57 (dive surveys) and 115 (video surveys) adults per ha. The total adult queen conch stock was estimated to be 184,100 (95% C.I.: 77,586-390,000) in 2,700 ha Marine Park. Further, a higher conch abundance was found on rubble habitats and at greater depths (17-31 m). Mainly mature conchs were detected, indicating a shortage of recruitment of young conch, or a difficulty in observing young conch. Further, reproductive activity started in March and declined after October, with peak reproductive activity during June and July. Minimum lip thickness reported for reproductive behaviour was 9 mm. However, this study also indicated that more research is necessary to qualify the exact spawning season and size at maturity of conch around St Eustatius.

In conclusion, the status of the queen conch could be qualified as good and does not seems to appear under direct pressure in the coastal waters of St Eustatius. With this population status, small- scale fishery may be possible without negative consequences for the queen conch population. However, to ensure long-term sustainable of a conch fishery, harvest restrictions as advised by the queen conch working group are recommended to be used; like a minimum of 15 mm lip thickness, closed areas and an annual harvest of maximal 6200 adult conch. Thus, non-detrimental fishing is possible for queen conch on St Eustatius, under the conditions that, proper management and harvest restriction regulations need to be developed, implemented and enforced in close co-operation with stakeholders.