Boman, E.M.

Juvenile queen conch are primarily associated with native seagrass such as Thalassia testudinum in large parts of their range in the Caribbean and the southern Gulf of Mexico. Here, a number of non-native seagrass species have been introduced including Halophila stipulacea, which is natural to the Red Sea and the Indo-Pacific. In the Caribbean, H. stipulacea often creates dense continuous mats with little or no sediment exposed, compared to native seagrass, which grows much less dense. We examined the diet and growth of juvenile conch in both native, mixed, and invasive seagrass beds using stable isotope analysis and an in situ growth enclosure experiment. Organic material in the sediment (i.e. benthic diatoms and particulate organic matter) was found to be the most important source of carbon and nitrogen for juvenile queen conch in all 3 habitats investigated, and there was a significantly higher probability of positive growth in the native seagrass compared to the invasive seagrass. Due to the importance of the organic material in the sediment as a source of nutrition for juvenile conch, limited access to the sediment in the invasive seagrass can potentially cause inadequate nutritional conditions to sustain high growth rates. Thus, it is likely that there is a negative effect on juvenile queen conch growth currently inhabiting invasive seagrass beds, compared to native seagrass beds, when other potential sources of nutrition are not available.

The first observations of juvenile lemon sharks (Negaprion brevirostris) around the island of Sint Eustatius are described. Observations were made in the summer of 2015 and spring of 2016 and only consisted of individuals estimated to be smaller than 65 cm in total length (TL). These observations represent a range extension of this species within the waters of the Dutch Caribbean. 

Prior to 2014 little research had been conducted on the Anguilla conch fishery aside from indirect data collected by the Department of Fisheries and Marine Resources (DFMR) during annual monitoring of reef and seagrass areas, or via generic landing site visits and other observations. Due to a suspected inadequacy of current regulations combined with concerns relating to fishery sustainability, DFMR facilitated two small groups of visiting researchers in 2014 and 2015 to fill this knowledge gap. The work conducted, combined with that carried out recently in neighboring islands, confirmed that the current minimum landing size of 18 cm shell length for Lobatus gigas (formerly Strombus gigas) is a poor indicator of conch maturity, with up to 94% of individuals of this size still immature. Histological analysis of gonad samples revealed that there is no correlation between shell length and maturity, with the development of a flared lip a much more precise indicator. It was concluded that a lip thickness of 10 mm should replace the minimum shell length legislation in order to move towards a more sustainable fishery. Semi-cleaned meat weight (digestive glands removed), essential to allow assessment of conch chucked by fishers while out at sea, currently set at 225 g was concluded to be sufficient given that meat weight can reduce as conch pass well beyond maturity. By accompanying fishers while harvesting L. gigas compliance to regulations seemed good, although it was recognized that this could be due to a researcher being present onboard. From in-water habitat and L. gigas abundance surveys a patchy distribution of conch were observed which led to an overall conclusion that the conch fishery in Anguilla is likely to be unsustainable, and so the need for legislative change is urgent. Based on boat activity surveys during the study period it was estimated that 69,190 lbs of semi-cleaned meat is landed per year by the fishery across an active fleet of seven full to part-time vessels (thus excluding recreational or small scale catches). This represents an estimated 6% of the fishable biomass. It is suggested that to ensure sustainability, this fishery should not be developed much beyond its current size and consideration be given to the issuance of special species specific licenses, and the introduction of recreational catch limits. This is especially relevant due to L. gigas being listed in 1992 under Appendix II of Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), of which Anguilla is party. It has been suggested that consideration be given to the possibility of conch farming in Anguilla, although the present study found this an unviable option due to a lack of extensive protected shallow water habitats and the difficulty in obtaining hatchery seed or juveniles for culture.